HIGH-PRESSURE PUMP

Abstract

A high-pressure pump (1) is equipped with a plunger (13) that moves in a reciprocating manner, a pressurization chamber (121) in which fuel is pressurized by the plunger (13), a fuel chamber (16) that accommodates a pulsation damper (50) and through which fuel flows, and a housing (11) that houses the fuel chamber. The fuel chamber (16) is connected to a return passage (310) through which fuel is returned from the fuel chamber (16) to a fuel tank (301) In addition, a connection passage (68) that includes a throttle (69) connects the fuel chamber (16) to the return passage (310).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase application of International Application No. PCT/IB2012/000011, filed Jan. 5, 2012, and claims the priority of Japanese Application No. 2011-003739, filed Jan. 12, 2011, the content of both of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a high-pressure pump.

2. Description of Related Art

In a high-pressure pump that supplies fuel to an injector of an engine (an internal combustion engine), the temperature of the fuel in the high-pressure pump may rise due to, for example, the heat from engine oil that is used to lubricate lifters, drive cams, and the like. Conventionally, it has been proposed to restrain the temperature of the fuel in a gallery chamber from rising and restrain the temperature of the fuel in a pressurization chamber from rising by returning the fuel in the high-pressure pump to a fuel tank through a return pipe (e.g., see Japanese Patent Application Publication No. 2010-65638 (JP-A-2010-65638)).

Furthermore, in order to efficiently restrain increases in the temperature of the fuel in the high-pressure pump, it is also conceivable to return the fuel to the fuel tank from a damper chamber that accommodates a pulsation damper. In this case, however, because the return pipe is connected to the damper chamber, the fuel flowing through a return passage may pulsate and cause a detriment to the pulsation absorbing function of the pulsation damper.

SUMMARY OF THE INVENTION

The invention provides a high-pressure pump that can suppress fuel pulsation in a return passage and restrain the pulsation absorbing function of a pulsation damper from deteriorating.

A first aspect of the invention relates to a high-pressure pump. The high-pressure pump includes a plunger that moves in a reciprocating manner, a pressurization chamber in which fuel is pressurized by the plunger, a fuel chamber which accommodates a pulsation damper and through which fuel flows, a housing in which the fuel chamber is formed, a return passage, through which fuel in the fuel chamber is returned toward a fuel tank, is connected to the fuel chamber, and a connecting portion, which is provided with a throttle, connects the fuel chamber with the return passage.

According to the foregoing aspect of the invention, fuel pulsation is damped by the throttle. Therefore, fuel pulsation in the return passage can be suppressed, and the pulsation absorbing function of the pulsation damper can be restrained from deteriorating.

In the foregoing aspect of the invention, the fuel chamber may be provided with a fuel supply port for supplying fuel to this fuel chamber, and the connecting portion may be provided at a position on the other side of the fuel supply port across the pulsation damper. According to the foregoing aspect of the invention, the fuel supply port and the connecting portion are arranged at diagonal positions across the pulsation damper. Therefore, the pulsation absorbing function of the pulsation damper can be efficiently brought out.

In the foregoing aspect of the invention, the fuel chamber may be provided with a guide member that guides flow of fuel traveling from the fuel supply port toward the connecting portion, and the guide member may be configured such that fuel introduced into the fuel chamber from the fuel supply port flows around the pulsation damper to reach the connecting portion. In the foregoing aspect of the invention, the guide member may be configured such that fuel from the fuel supply port flows through a space located below the pulsation damper, a space located beside the pulsation damper and on the other side of the fuel supply port across the pulsation damper, and a space located above the pulsation damper in this order to reach the connecting portion. According to the foregoing aspect of the invention, the return fuel returned to the fuel tank is caused to flow through the space located below the pulsation damper, the space located beside the pulsation damper, and the space located above the pulsation damper in this order and guided to the connecting portion by the guide member. Thus, fuel pulsation may be damped with the aid of both an upper face of the pulsation damper and a lower face of the pulsation damper. Therefore, the pulsation absorbing function of the pulsation damper can be brought out to the maximum possible extent.

According to the invention, fuel pulsation is damped by the throttle. Therefore, fuel pulsation in the return passage may be suppressed, and deterioration of the pulsation absorbing function of the pulsation damper is restrained.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of an example embodiment of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a schematic view of a fuel supply system equipped with a high-pressure pump according to the embodiment of the invention;

FIG. 2 is a cross-sectional view of the overall configuration of the high-pressure pump according to the embodiment of the invention;

FIG. 3 is a cross-sectional view of a damper device of the high-pressure pump of FIG. 2 and the periphery thereof;

FIG. 4 is a view showing a first modified example of the high-pressure pump and corresponding to FIG. 3; and

FIG. 5 is a view showing a second modified example of the high-pressure pump and corresponding to FIG. 3.

DETAILED DESCRIPTION OF EMBODIMENT

An embodiment of the invention will be described with reference to the accompanying drawings. In the described embodiment, the invention is applied to the fuel supply system of a V-6 gasoline engine (an internal combustion engine) mounted on an automobile. Furthermore, the engine of the described embodiment is also equipped with a port injection injector and an in-cylinder direct injection injector for each cylinder.

A fuel supply system 300 exemplified in FIG. 1 is equipped with a feed pump 302 that pumps fuel from a fuel tank 301. A low-pressure fuel pipe 303 connected to a discharge side of the feed pump 302 branches off toward a low-pressure fuel system LF and a high-pressure fuel system HF.

The low-pressure fuel system LF includes low-pressure fuel system delivery pipes 304a and 304b, which are connected to each bank of the engine. More specifically, the low-pressure fuel pipe 303 is connected to the low-pressure fuel system delivery pipe 304a installed in one of the banks, and the low-pressure fuel system delivery pipes 304a and 304b are connected to each other by a liaison pipe 304c. Port injection injectors 305 are connected to the low-pressure fuel system delivery pipes 304a and 304b in a manner corresponding to respective cylinders (three cylinders in each of the banks).

The high-pressure fuel system HF includes a high-pressure pump 1 that pressurizes fuel, which is pumped out by the feed pump 302 and drawn in via the other branch side of the low-pressure fuel pipe 303, and discharges the pressurized fuel toward in-cylinder direct injection injectors 306 provided in each cylinder of each bank.

The high-pressure pump 1 includes a housing 11, a plunger 13, a valve body 30, and an electromagnetic drive portion 70 (see FIG. 2), and may be attached to, for example, the head cover on one of the banks of the engine. A roller lifter 27 having a lifter body 271, a roller 272, is attached to the lower end of the plunger 13 of the high-pressure pump 1. The roller 272 is rotatably supported via a plurality of skids 274 provided on over the outer periphery of a spindle 273. A drive cam 281 provided on an intake cam shaft 28 in one of the banks abuts with the outer peripheral face of the roller 272. Three cam noses 282 are formed on the drive cam 281 at angular intervals of 120° around the axis of rotation of the intake cam shaft 28. Then, as the drive cam 281 is rotated by the intake cam shaft 28, the plunger 13 is pushed up via the roller lifter 27. In this configuration, the plunger 13 reciprocates within a cylinder 14, thereby varying the volume of a pressurization chamber 121. The high-pressure pump 1 will be described in detail later.

The pressurization chamber 121 of the high-pressure pump 1 communicates with the feed pump 302 via the low-pressure fuel pipe 303, and also communicates with the high-pressure fuel system delivery pipes 308a and 308b via a high-pressure fuel pipe 307. More specifically, in this configuration, the high-pressure fuel pipe 307 is connected to the high-pressure fuel system delivery pipe 308a installed in one of the banks, and the high-pressure fuel system delivery pipes 308a and 308b are connected to each other by a liaison pipe 308c. The in-cylinder injectors 306 are connected to the high-pressure fuel system delivery pipe 308a and 308b in a manner corresponding to the respective cylinders (three cylinders in each of the banks). It should be noted that a filter 303a and a pressure regulator 303b are provided in the low-pressure fuel pipe. The pressure regulator 303b maintains the pressure of the fuel in the low-pressure fuel pipe 303 at or below a threshold pressure (e.g., 400 kPa) by returning the fuel in the low-pressure fuel pipe 303 to the fuel tank 301 when the pressure of the fuel in the low-pressure fuel pipe 303 exceeds the threshold pressure.

Next, the configuration of the high-pressure pump 1 will be described in detail. As shown in FIGS. 1 and 2, the housing 11 of the high-pressure pump 1 may be formed from a stainless steel, for example, such as a martensite steel. The circular cylinder 14 is formed in the housing 11. The plunger 13 is supported in the cylinder 14 axially movably in a reciprocating manner. Further, an introduction passage 111, an intake passage 112, the pressurization chamber 121, and a discharge passage 114 are formed in the housing 11.

Further, the housing 11 has a tube portion 15. A passage 151 through which the introduction passage 111 and the intake passage 112 communicate with each other is formed inside the tube portion 15. The tube portion 15 is formed substantially perpendicularly to a central axis of the cylinder 14, and changes in inner diameter at some point. A step face 152 is formed at the region of the tube portion 15 where the inner diameter changes. The valve body 30 is provided in the passage 151 of the tube portion 15.

A fuel chamber (a damper chamber) 16 is formed between the housing 11 and a lid 12. The fuel chamber 16 is connected to the low-pressure fuel pipe 303. The feed pump 302 pumps fuel from the fuel tank 301 through the low-pressure fuel pipe 303 and into the fuel chamber 16 through a fuel supply port 311. The introduction passage 111 establishes communication between the fuel chamber 16 and the passage 151 of the tube portion 15. A first end of the intake passage 112 communicates with the pressurization chamber 121. A second end of the intake passage 112 opens to the inside of the step face 152. The introduction passage 111 is connected to the intake passage 112 via the inside of the valve body 30. The pressurization chamber 121 communicates with the discharge passage 114 on the other side of the intake passage 112. It should be noted that these fuel passages are illustrated as a fuel passage 100 in the embodiment of the invention.

The plunger 13 is supported by the cylinder 14 of the housing 11 axially movably in a reciprocating manner. The plunger 13 is composed of a small-diameter portion 131, and a large-diameter portion 133 that has a larger diameter than that of the small-diameter portion 131. The large-diameter portion 133 is connected to the pressurization chamber 121 side of the small-diameter portion 131, and the step face 132 is formed between the large-diameter portion 133 and the small-diameter portion 131. The pressurization chamber 121 is formed in the large-diameter portion 133 on the other side of the small-diameter portion 131. The step face 132 of the plunger 13 is provided, on the other side of the pressurization chamber 121, with a generally annular plunger stopper 23 that is in contact with the housing 11.

On the end face of the plunger stopper 23 that is nearer to the pressurization chamber 121, there are provided a recess 231 that is recessed toward the other side of the pressurization chamber 121 generally in the shape of a circular disc, and a groove channel 232 that extends radially outward from the recess 231 toward the outer edge of the plunger stopper 23. The diameter of the recess 231 is approximately equal to the outer diameter of the large-diameter portion 133 of the plunger 13. A hole 233 that penetrates the plunger stopper 23 in a through-thickness direction is formed through a central portion of the recess 231. The small-diameter portion 131 of the plunger 13 is inserted through the hole 233. Further, the end face of the plunger stopper 23 on the pressurization chamber 121 side is in contact with the housing 11. A generally annular variable volume chamber 122 is formed by the step face 132 of the plunger 13, an outer wall of the small-diameter portion 131, an inner wall of the cylinder 14, the recess 231 of the plunger stopper 23, and a sealing member 24.

A generally annular recess 105 that is recessed toward the pressurization chamber 121 is formed in the cylinder 14 outside an end thereof on the other side of the pressurization chamber 121. A spring seat 25 is fitted in the recess 105. An oil seal holder is integrally formed in the spring seat 25 and supports an oil seal 26 and the sealing member 24. The spring seat 25 is fixed to the housing 11. The sealing member 24 is sandwiched between the spring seat 25 and the plunger stopper 23. The sealing member 24 is composed of a sealing ring located on an inner peripheral side and made of, for example, PTFE, and an O-ring located on an outer peripheral side. The sealing member 24 adjusts the thickness of a fuel oil film around the small-diameter portion 131, thus restraining fuel from leaking to the engine due to the sliding of the plunger 13. The oil seal 26 is fitted to the end of the spring seat 25 away from the pressurization chamber 121. The oil seal 26 controls the thickness of the oil film around the small-diameter portion 131, thus restraining oil from leaking due to the sliding of the plunger 13.

An annular passage 106 and a passage 107 are formed between the spring seat 25 and the housing 11. The passage 107 is provided between a bottom 251 of the spring seat 25 and the housing 11. The annular passage 106 is provided between a tubular inner tube portion, which extends from an inner peripheral edge of the bottom 251 of the spring seat 25 toward the other side of the pressurization chamber 121 (downward in FIG. 2), and the housing 11. It should be noted that a tubular outer tube portion that extends from the bottom 251 of the spring seat 25 toward the other side of the pressurization chamber 121 is in close contact with the housing 11.

In addition, the passages 106 and 107 communicate with each other. Further, a passage 108, through which the passage 107 and the fuel chamber 16 communicate with each other, is formed through the housing 11. The passage 106 is communicated with the groove channel 232 of the plunger stopper 23. Accordingly, the groove channel 232, the passage 106, the passage 107, and the passage 108 communicate with one another, so that the variable volume chamber 122 communicates with the fuel chamber 16.

A head 17 is provided on the small-diameter portion 131 of the plunger 13 on the other side of the large-diameter portion 133. The head 17 is coupled to a spring seat 18. A spring 19 is compressed between the spring seats 18 and 25. That is, one end of the spring 19 (the end on the pressurization chamber 121 side) is in contact with the bottom of the spring seat 25 fixed to the housing 11, and the other end of the spring 19 is in contact with the spring seat 18 coupled to the head 17. The plunger 13 is driven to reciprocate by coming into contact with the drive cam 281 via the roller lifter 27. The roller lifter 27 is urged toward the drive cam 281 side (downward in FIG. 2) via the spring seat 18 due to an elastic force of the spring 19. That is, the spring 19 urges the plunger 13 in a direction to increase the volume of the pressurization chamber 121.

The variable volume chamber 122 changes in volume as a result of the reciprocating motion of the plunger 13. When the volume of the pressurization chamber 121 decreases due to the movement of the plunger 13 in a metering stroke or a pressurization stroke, the volume of the variable volume chamber 122 increases. Thus, fuel is drawn into the variable volume chamber 122 from the fuel chamber 16, which is connected to the fuel passage 100, through the passage 108, the passage 107, the passage 106, and the groove channel 232. Further, in the metering stroke, part of the low-pressure fuel discharged from the pressurization chamber 121 may be drawn into the variable volume chamber 122. Thus, the transmission of fuel pressure pulsation to the low-pressure fuel piping may be restrained due to the discharge of fuel from the pressurization chamber 121.

However, when the volume of the pressurization chamber 121 increases due to the movement of the plunger 13 in an intake stroke, the volume of the variable volume chamber 122 decreases. Thus, fuel is sent from the variable volume chamber 122 to the fuel chamber 16. It should be noted that the volume of the pressurization chamber 121 and the volume of the variable volume chamber 122 are determined only by the position of the plunger 13. Therefore, as fuel is drawn into the pressurization chamber 121, fuel is sent out from the variable volume chamber 122 to the fuel chamber 16. Thus, decreases in pressure within the fuel chamber 16 are restrained, and the amount of the fuel drawn into the pressurization chamber 121 through the fuel passage 100 increases. Thus, fuel is drawn into the pressurization chamber 121 with greater efficiency.

A discharge valve 90 that forms a fuel outlet 91 is provided on the discharge passage 114 side of the housing 11. The discharge valve 90 regulates the discharge of the pressurized fuel in the pressurization chamber 121. The discharge valve 90 includes a check valve 92, a regulation member 93, and a spring 94. The check valve 92 is formed as a closed-end tube from a bottom 921 and a tube portion 922 that extends from the bottom 921 toward the other side of the pressurization chamber 121, and is provided in the discharge passage 114 movably in a reciprocating manner. The regulation member 93 is formed as a tube, and is fixed to the housing 11, which forms the discharge passage 114. One end of the spring 94 contacts the regulation member 93, and the opposite end of the spring 94 contacts the tube portion 922 of the check valve 92. The check valve 92 is urged toward a valve seat 95 provided in the housing 11 by the elastic force of the spring 94. The end of the check valve 92 on the bottom 921 moves onto the valve seat 95 to close the discharge passage 114, and the end moves away from the valve seat 95 to open the discharge passage 114. When the check valve 92 moves toward the other side of the valve seat 95, the end of the tube portion 922 on the other side of the bottom 921 comes into contact with the regulation member 93, so that movement of the check valve 92 is restrained.

When the fuel pressure in the pressurization chamber 121 rises, the force exerted on the check valve 92 by the fuel in the pressurization chamber 121 increases. Then, when the force exerted on the check valve 92 from the fuel on the pressurization chamber 121 side exceeds the sum of the elastic force of the spring 94 and the force exerted by the fuel downstream of the valve seat 95, specifically, the fuel in the high-pressure fuel system delivery pipes 308a and 308b, the check valve 92 moves away from the valve seat 95. Thus, the fuel in the pressurization chamber 121 is discharged from the fuel outlet 91 to the outside of the high-pressure pump 1 via a through-hole 923 formed through the tube portion 922 of the check valve 92 and the interior of the tube portion 922.

In contrast, when the pressure of the fuel in the pressurization chamber 121 falls, the force received by the check valve 92 from the fuel on the pressurization chamber 121 side decreases. Then, when the force received by the check valve 92 from the fuel on the pressurization chamber 121 side falls below the sum of the elastic force of the spring 94 and the force exerted by the fuel downstream of the valve seat 95, the check valve 92 moves onto the valve seat 95. Thus, the fuel in the delivery pipes is prevented from flowing into the pressurization chamber 121 via the discharge passage 114.

The valve body 30 is press-fitted in the passage 151 of the housing 11, and may be fixed to the interior of the passage 151 by an engagement member 20 or the like. The valve body 30 has a generally annular valve seat portion 31, and a tube portion 32 that extends from this valve seat portion 31 toward the pressurization chamber 121 side. An annular valve seat 34 is formed on a wall surface of the valve seat portion 31 on the pressurization chamber 121 side.

A valve member 35 is provided inside the tube portion 32 of the valve body 30. The valve member 35 has a circular disc portion 36, and a guide portion 37 that is formed as a hollow cylinder that extends from the outer edge of the circular disc portion 36 toward the pressurization chamber 121. A disc-shaped recess 39 that is recessed away from the valve seat 34 is formed in the circular disc portion 36. An inner peripheral wall of the valve member 35 that forms the recess 39 is tapered, with its diameter decreasing toward the pressurization chamber 121. A ring-like annular fuel passage 101 is formed between an inner wall of the tube portion 32 of the valve body 30 and outer walls of the circular disc portion 36 and the guide portion 37. Due to the reciprocating movement of the valve member 35, the circular disc portion 36 moves onto or away from the valve seat 34 to regulate the flow of the fuel through the fuel passage 100. The dynamic pressure of the fuel flowing from the passage 151 to the annular fuel passage 101 is exerted on the recess 39. A stopper 40 is provided on the valve member 35 on the pressurization chamber 121 side, and is fixed to the inner wall of the tube portion 32 of the valve body 30.

The inner diameter of the guide portion 37 of the valve member 35 is slightly larger than that of an end of the stopper 40 on the valve member 35 side. Thus, when the valve member 35 moves toward the opening direction or toward the closing direction, the inner wall of the guide portion 37 slides along the outer wall of the stopper 40. Thus, the valve member 35 is guided to reciprocate in the opening direction or the closing direction.

A spring 21 is provided between the stopper 40 and the valve member 35. The spring 21 is located inside the stopper 40 and the guide portion 37 of the valve member 35. One end of the spring 21 is in contact with an inner wall of the stopper 40, and the other end of the spring 21 is in contact with the circular disc portion 36 of the valve member 35. The valve member 35 is urged toward the other side of the stopper 40, namely, in the closing direction, by the elastic force of the spring 21.

An end of the guide portion 37 of the valve member 35 on the pressurization chamber 121 side may abut against a step face 501 provided on the outer wall of the stopper 40. When the valve member 35 abuts against the step face 501, the stopper 40 prevents the valve member 35 from moving toward the pressurization chamber 121 side, namely, in the opening direction. When viewed from the pressurization chamber 121 side, the stopper 40 conceals the wall of the valve member 35 on the pressurization chamber 121 side. Thus, the influence of the dynamic pressure applied to the valve member 35 by the flow of the low-pressure fuel traveling from the pressurization chamber 121 side toward the valve member 35 side in a metering stroke is suppressed.

A volume chamber 41 is formed between the stopper 40 and the valve member 35. The volume of the volume chamber 41 changes with the reciprocating movement of the valve member 35. Further, a duct 42 through which the volume chamber 41 and the annular fuel passage 101 communicate with each other is formed through the stopper 40. Thus, the fuel in a plurality of passages 102 can flow into the volume chamber 41. The passages 102 are formed in the stopper 40 at an incline with respect to the axis of the stopper 40, and the annular fuel passage 101 is communicated with the intake passage 112 via the passages 102. The plurality of the passages 102 are formed along the circumferential direction of the stopper 40.

The above-described fuel passage 100 includes the annular fuel passage 101 and the passages 102 as well. Thus, the fuel chamber 16 is communicated with the pressurization chamber 121 via the fuel passage 100. Then, when traveling from the fuel chamber 16 side toward the pressurization chamber 121 side, fuel flows through the introduction passage 111, the passage 151, the annular fuel passage 101, the passages 102, and the intake passage 112, in the stated order. In contrast, when traveling from the pressurization chamber 121 side toward the fuel chamber 16 side, fuel flows through the intake passage 112, the passages 102, the annular fuel passage 101, the passage 151, and the introduction passage 111, in the stated order.

The electromagnetic drive portion 70 includes, for example, a coil 71, a fixed core 72, a movable core 73, and a flange 75. The coil 71 is wound around a resin spool 78, and generates a magnetic field when energized. The fixed core 72 is formed of a magnetic material. The fixed core 72 is accommodated inside the coil 71. The movable core 73 is formed of a magnetic material. The movable core 73 is arranged opposite the fixed core 72. The movable core 73 is accommodated inside the flange 75 and a tube 79 axially movably in a reciprocating manner. The tube 79 is made of a non-magnetic material, and prevents magnetic short circuit between the fixed core 72 and the flange 75.

The flange 75 is formed of a magnetic material, and is attached to the tube portion 15 of the housing 11. The flange 75 retains the electromagnetic drive portion 70 in the housing 11, and closes the end of the tube portion 15. A guide tube 76 is provided at a central portion of the flange 75.

A needle 38 is provided inside the guide tube 76 of the flange 75. The inner diameter of the guide tube 76 is slightly larger than the outer diameter of the needle 38. Thus, the needle 38 moves in a reciprocating manner while sliding along an inner wall of the guide tube 76. Thus, the reciprocating movement of the needle 38 is guided by the guide tube 76.

One end of the needle 38 is press-fitted or welded to the movable core 73, so that the needle 38 is integrally assembled with the movable core 73. Further, the other end of the needle 38 can abut on a wall surface of the circular disc portion 36 on the valve seat 34 side. A spring 22 is provided between the fixed core 72 and the movable core 73. The movable core 73 is urged toward the valve member 35 by the elastic force of the spring 22. The elastic force applied by the spring 22 to urge the movable core 73 is greater than the elastic force applied by the spring 21 to urge the valve member 35. That is, the spring 22 urges the movable core 73 and the needle 38 toward the valve member 35, namely, in the opening direction of the valve member 35 against the elastic force of the spring 21. If the coil 71 is not energized, the fixed core 72 and the movable core 73 are spaced apart from each other. Thus, when the coil 71 is not energized, the needle 38 moves toward the valve member 35 due to the elastic force of the spring 22, and the valve member 35 has moved away from the valve seat 34. In this manner, the elastic force of the spring 22 drives the needle 38 to abut against the circular disc portion 36, thereby pressing the valve member 35 in the opening direction.

Next, a damper device 10 will be described. The housing 11 has, on the other side of the plunger 13, a damper housing 110 in the shape of a bottomed tube. The fuel chamber 16 is formed within the damper housing 110. The fuel chamber 16 is positioned substantially coaxially with the plunger 13. The lid 12 may be formed of, for example, a stainless steel. One end of the lid 12 on the opening side thereof is bonded to the outer wall of the damper housing 110 through welding or the like, so that the lid 12 closes the opening 7 of the fuel chamber 16. The introduction passage 111, the passage 108, and the low-pressure fuel pipe 303 are connected to the fuel chamber 16. Thus, the fuel chamber 16 communicates with the pressurization chamber 121, the variable volume chamber 122, and the feed pump 302, which pumps fuel in from the fuel tank 301.

As shown in FIG. 3, the damper device includes a pulsation damper 50 as a damper member, an upper support member 61, a lower support member 62, press means 80, and the like. The pulsation damper 50 has an upper diaphragm 51 and a lower diaphragm 52. The upper diaphragm 51 and the lower diaphragm 52 are formed into the shape of a plate by, for example, pressing a metal plate of a stainless material or the like. The upper diaphragm 51 has an elastically deformable plate-like recessed face 53 provided at a central portion of the upper diaphragm 51, and a thin plate-like annular upper peripheral edge portion 55 provided integrally with a peripheral edge of the plate-like recessed face 53. As is the case with the upper diaphragm 51, the lower diaphragm 52 also has a plate-like recessed face 54 and a lower peripheral edge portion 56.

The entire circumference of the upper peripheral edge 55 of the upper diaphragm 51 and the entire circumference of the lower peripheral edge 56 of the lower diaphragm 52 are welded together along a circumferential direction thereof, so that a weld 57 is formed. Thus, a gastight chamber 3 is formed between the upper diaphragm 51 and the lower diaphragm 52. For example, helium gas, argon gas, or the mixture gas thereof is encapsulated at a predetermined pressure in the gastight chamber 3. The upper diaphragm 51 and the lower diaphragm 52 elastically deform in response to changes in the pressure within the fuel chamber 16. Thus, the volume of the gastight chamber 3 changes, thereby abating the pressure pulsation of the fuel flowing through the fuel chamber 16. It should be noted that spring constants of the upper diaphragm 51 and the lower diaphragm 52 are determined by the thicknesses and materials of the upper diaphragm 51 and the lower diaphragm 52, a gas encapsulation pressure of the gastight chamber 3, and the like in accordance with a required level of durability and other required performances. The pulsation frequency abatable by the pulsation damper 50 is determined by these spring constants. Further, the pulsation abating effect of the pulsation damper 50 changes in accordance with the magnitude of the volume of the gastight chamber 3.

The upper support member 61 and the lower support member 62 are generally tubularly formed by, for example, pressing or bending a metal plate of a stainless material or the like. The upper support member 61 has a tube portion 613, an inner flange 611, an outer flange 612, and a claw portion 65. The tube portion 613 is tubularly formed, and has a plurality of upper communication holes 63. The inner flange 611 annularly extends inward from one axial end of the tube portion 613, and is formed perpendicularly to the axis of the upper support member 61. The outer flange 612 annularly extends outward from the other axial end of the tube portion 613, and is bent so that it is inclined toward one end side of the upper support member 61. The claw portion 65 extends outward from the outer end of the outer flange 612, and the tip of the claw portion 65 is bent toward the other side of one end of the upper support member 61.

The lower support member 62 has a tube portion 623, an inner flange 621, an outer flange 622, and a claw portion 66. The tube portion 623 is tubularly formed, and has a plurality of lower communication holes 64. The inner flange 621 annularly extends inward from one axial end of the tube portion 623, and is perpendicular to the axis of the lower support member 62. The outer flange 622 annularly extends outward from the other axial end of the tube portion 623, and is inclined toward one end side of the lower support member 62. The claw portion 66 further extends outward from an outer end of the outer flange 622, and the tip end of the claw portion 66 is bent toward the other side of one end of the lower support member 62.

The weld portion 57 between the upper diaphragm 51 and the lower diaphragm 52 is engaged by the claw portions 65 and 66. Thus, relative movement of the upper support member 61, the lower support member 62, and the pulsation damper 50 in the radial direction is prevented. The outer flange 612 of the upper support member 61 and the upper peripheral edge portion 55 of the upper diaphragm 51 abut on each other along a circumferential direction thereof, so that an upper abutment portion 8 is formed. The outer flange 622 of the lower support member 62 abuts with the lower peripheral edge portion 56 of the lower diaphragm 52 along a circumferential direction thereof, so that a lower abutment portion 9 is formed.

A tubular recess 2 that is recessed toward the pressurization chamber 121 side is provided in an inner wall of the damper housing 110 on the other side of the lid 12. The inner flange 621 of the lower support member 62 is fitted in the recess 2. Thus, movement of the upper support member 61, the lower support member 62, and the pulsation damper 50 in the radial direction of in the fuel chamber 16 is prevented. Thus, an outer space 4 is formed between the inner wall of the damper housing 110 and outer walls of the upper support member 61 and the lower support member 62. The outer space 4 surrounds the exteriors of the upper support member 61 and the lower support member 62.

An inner space 5 is formed within the upper support member 61. An inner space 6 is formed inside the lower support member 62. The inner space 5 and the inner space 6 are separated from each other by the pulsation damper 50. However, the fuel in the outer space 4 and the fuel in the inner space 5 of the upper support member 61 flow via the upper communication holes 63, and the fuel in the outer space 4 and the fuel in the inner space 6 of the lower support member 62 flow via the lower communication holes 64.

The press means 80 has a press transmission member 82, and a disc spring 81 as an elastic member. The press transmission member 82 is annularly formed of, for example, a stainless material or the like, and is provided on the lid 12 side of the upper support member 61. The press transmission member 82 includes an annular portion 84 and a projection 83. The face of the annular portion 84 on the upper support member 61 side in an axial direction thereof is formed perpendicularly to an axis of the annular portion 84. Thus, the annular portion 84 and the inner flange 611 of the upper support member 61 are in surface contact with each other along a circumferential direction thereof. Thus, the elastic force of the disc spring 81 substantially homogeneously acts on the press transmission member 82. The outer wall of the annular portion 84 is guided to the inner wall of the damper housing 110. Thus, radial movement of the press transmission member 82 within the fuel chamber 16 is prevented. The projection 83 is so provided at an inner end of the annular portion 84 as to project toward the lid 12 side. Thus, a step is provided between an outer wall of the projection 83 and a face of the annular portion 84 on the lid 12 side in an axial direction thereof. The face of the annular portion 84 located on the lid 12 side and formed adjacently to this step serves as an engagement portion 85 that engages the disc spring 81.

The disc spring 81 is annularly formed of, for example, a stainless material or the like. One end of the disc spring 81 abuts on the lid 12. The other end of the disc spring 81 abuts on the engagement portion 85 along a circumferential direction thereof. The diameter of the disc spring 81 is smaller on the engagement portion 85 side than on the lid 12 side. Thus, the other end of the disc spring 81 is guided to the outer wall of the projection 83. Thus, movement of the disc spring 81 in the radial direction with respect to the press transmission member 82 is minimized The elastic force of the disc spring 81 is transmitted to the upper support member 61 and the lower support member 62 by the press transmission member 82, and acts on the upper abutment portion 8 and the lower abutment portion 9. Then, the upper support member 61 presses the upper peripheral edge portion 55 at the upper abutment portion 8, and the lower support member 62 presses the lower peripheral edge portion 56 at the lower abutment portion 9.

Next, the operation of the high-pressure pump 1 will be described. By repeating an intake stroke, a metering stroke, and a pressurization stroke, which will be described below, the high-pressure pump 1 pressurizes and discharges the fuel. The amount of fuel discharged is adjusted by controlling the duration of energization of the coil 71. The intake stroke, the metering stroke, and the pressurization stroke will be described concretely.

First, the intake stroke will be described. When the plunger 13 moves downward in FIG. 2, energization of the coil 71 is prevented. Thus, the spring 22 exerts elastic force on the movable core 73 and the valve body 35 is urged toward the pressurization chamber 121 by the needle 38. As a result, the valve member 35 is moved away from the valve seat 34 of the valve body 30. Further, when the plunger 13 moves downward in FIG. 2, the pressure in the pressurization chamber 121 decreases. Thus, the force exerted on the valve member 35 by the fuel on the other side of the pressurization chamber 121 is greater than the force exerted on the valve member 35 by the fuel on the pressurization chamber 121 side. Thus, the force is applied to the valve member 35 and moves it away from the valve seat 34. The valve member 35 moves until the guide portion 37 abuts on the step face 501 of the stopper 40. The valve member 35 moves away from the valve seat 34, namely, opens, so that the fuel in the fuel chamber 16 is drawn into the pressurization chamber 121 via the introduction passage 111, the passage 151, the annular fuel passage 101, the passages 102, and the intake passage 112. Further, at this moment, the fuel in the passages 102 can flow into the volume chamber 41 through the duct 42. Thus, the pressure in the volume chamber 41 is equal to the pressure in the passages 102.

Next, the metering stroke will be described. When the plunger 13 ascends from bottom dead center toward top dead center, the fuel from the pressurization chamber 121 exerts force on the valve member 35 to move the valve member 35 onto the valve seat 34, due to the flow of the low-pressure fuel discharged from the pressurization chamber 121 to the fuel chamber 16 side. However, when the coil 71 is not energized, the needle 38 is urged toward the valve member 35 by the elastic force of the spring 22. Thus, the needle 38 keeps the valve member 35 from moving toward the valve seat 34. Further, the wall surface of the valve member 35 on the pressurization chamber 121 side is covered with the stopper 40. Thus, the dynamic pressure resulting from the flow of the fuel discharged from the pressurization chamber 121 toward the fuel chamber 16 is restrained from directly acting on the valve member 35. Accordingly, the force applied to the valve member 35 in the closing direction by the flow of fuel is reduced.

In the metering stroke, while the coil 71 is stopped from being energized, the valve member 35 moves away from the valve seat 34 and is held in abutment against the step face 501. Thus, the fuel discharged from the pressurization chamber 121 by the ascent of the plunger 13 is returned to the fuel chamber 16 via the intake passage 112, the passages 102, the annular fuel passage 101, the passage 151, and the introduction passage 111, as opposed to when the fuel is drawn into the pressurization chamber 121 from the fuel chamber 16.

When the coil 71 is energized in the metering stroke, a magnetic circuit is formed among the fixed core 72, the flange 75, and the movable core 73, due to a magnetic field generated in the coil 71. Thus, a magnetic suction force is generated between the fixed core 72 and the movable core 73, which are spaced apart from each other. When the magnetic suction force generated between the fixed core 72 and the movable core 73 exceeds the elastic force of the spring 22, the movable core 73 moves toward the fixed core 72. Accordingly, the needle 38 of the movable core 73 also moves toward the fixed core 72. When the needle 38 moves toward the fixed core 72, the needle 38 becomes separated from the valve member 35 so that the needle 38 does not exert any force on the valve member 35. As a result, the valve member 35 is moved toward the valve seat 34 (i.e., in the closing direction) by the elastic force of the spring 21 and the force applied to the valve member 35 by the flow of the low-pressure fuel discharged from the pressurization chamber 121 toward the fuel chamber 16. Thus, the valve member 35 moves onto the valve seat 34. Due to the closing of the valve member 35, the flow of the fuel flowing through the fuel passage 100 is shut off. The metering stroke in which low-pressure fuel is discharged from the pressurization chamber 121 to the fuel chamber 16 is thereby terminated. When the plunger 13 ascends, the space between the pressurization chamber 121 and the fuel chamber 16 is closed, so that the amount of the low-pressure fuel returned from the pressurization chamber 121 to the fuel chamber 16 is adjusted. As a result, the amount of the fuel pressurized in the pressurization chamber 121 is determined.

Next, the pressurization stroke will be described. When the plunger 13 further ascends toward the top dead center while the space between the pressurization chamber 121 and the fuel chamber 16 closed, the pressure of the fuel in the pressurization chamber 121 increases. When the pressure of the fuel in the pressurization chamber 121 equals or exceeds a predetermined pressure, the check valve 92 moves away from the valve seat 95 against the elastic force of the spring 94 of the discharge valve portion 90 and the force received by the check valve 92 from the fuel downstream of the valve seat 95. Thus, the discharge valve portion 90 opens, and the pressurized fuel in the pressurization chamber 121 is discharged from the high-pressure pump 1 through the discharge passage 114. The fuel discharged from the high-pressure pump 1 is supplied to the high-pressure fuel system delivery pipes 308a and 308b, accumulated therein, and then supplied to the in-cylinder direct injection injectors 306.

Once the plunger 13 is at top dead center, energization of the coil 71 ends, and the valve member 35 moves away from the valve seat 34 again. Then, the plunger 13 moves downward in FIG. 2, and the pressure of the fuel in the pressurization chamber 121 falls. Thus, fuel is drawn into the pressurization chamber 121 from the fuel chamber 16.

It should be noted that the coil 71 may be stopped from being energized when the valve member 35 closes and the pressure of the fuel in the pressurization chamber 121 rises to a predetermined value. When the pressure of the fuel in the pressurization chamber 121 rises, the force exerted on the valve member 35 to move the valve member 35 toward the valve seat 34 by the fuel from the pressurization chamber 121 exceeds the force exerted on the valve member 35 to move the valve member 35 away from the valve seat 34. Thus, even when energization of the coil 71 ceases, the valve member 35 is held on the valve seat 34 by the force exerted by the fuel from the pressurization chamber 121. By thus stopping energization of the coil 71 at a predetermined timing, the power consumption of the electromagnetic drive portion 70 is reduced.

This embodiment of the invention is characterized in that a return passage 310, through which the fuel in the fuel chamber 16 of the high-pressure pump 1 is returned toward the fuel tank 301, is connected to the fuel chamber 16, and that the fuel chamber 16 is connected to the return passage 310 via a connection passage 68, in which a throttle 69 is provided. The connection passage 68 may serve as the connecting portion of the invention. The return passage 310 will be described below in detail with reference to FIGS. 1 to 3.

The fuel supply system 300, shown in FIG. 1, includes the return passage 310, through which the fuel in the fuel chamber 16 is returned toward the fuel tank 301.

In the high-pressure pump 1 shown in FIGS. 2 and 3, the lid 12 provided above the housing 11 closes the opening 7 of the fuel chamber 16. The lid 12 is formed integrally with a connection member 67 having the connection passage 68. The connection passage 68 connects the fuel chamber 16 to the return passage 310. The fuel in the fuel chamber 16 is directed to flow to the return passage 310 via the connection passage 68, and then is returned to the fuel tank 301.

In this embodiment of the invention, the throttle 69 is formed somewhere along the connection passage 68 formed inside the connection member 67. More specifically, as shown in FIG. 3, the connection passage 68 has an inlet-side passage 681 and an outlet-side passage 682. The inlet-side passage 681 extends vertically (in a longitudinal direction in FIG. 3), and an upstream end 683 of the inlet-side passage 681 opens to the fuel chamber 16. The outlet-side passage 682 extends in a direction perpendicular to the inlet-side passage 681 (in a lateral direction in FIG. 3), and a downstream end of the outlet-side passage 682 is connected to the return passage 310. In addition, a downstream end of the inlet-side passage 681 is connected to an upstream end of the outlet-side passage 682 a via the throttle 69. The cross-section of the throttle 69 is smaller the area before and behind the throttle 69. It should be noted that the passage cross-sectional area of the throttle 69 may be smaller than that of both the downstream end of the inlet-side passage 681 and the upstream end of the outlet-side passage 682. Further, the passage cross-sectional area of the throttle 69 may be equal to or smaller than both half of the passage cross-sectional area of the downstream end of the inlet-side passage 681 and half of the passage cross-sectional area of the upstream end of the outlet-side passage 682.

As described above, the connecting passage 68 between the fuel chamber 16 and the return passage 310 is provided with the throttle 69. Therefore, pressure pulsation of the fuel flowing through the return passage 310 is suppressed, and the pulsation absorbing function of the pulsation damper 50 is restrained from deteriorating. This will be described in further detail below.

First, the fuel in the high-pressure pump 1 absorbs heat from the engine, so that the temperature of the fuel increases. For example, the fuel in the high-pressure pump 1 absorbs heat from engine oil that lubricates the roller lifter 27, the drive cam 281, and the like, so that the temperature of the fuel rises. In contrast, when the fuel in the high-pressure pump 1 is supplied to the high-pressure fuel system delivery pipes 308a and 308b and injected from the in-cylinder direct injection injectors 306, heat is released (heat is discharged) as a result of the injection of the fuel. However, for example, when fuel cut is carried out or when the engine is stopped from a high-load operation state (at the time of so-called high-temperature dead soak), the injection of fuel from the in-cylinder direct injection injectors 306 is stopped, and hence the amount of heat released decreases. Therefore, the temperature of the fuel remaining in the high-pressure pump 1 is high. As a result, vapors are generated in the high-pressure pump 1, and the discharge amount control of the high-pressure pump 1 may be adversely affected.

In the embodiment of the invention described above, heat is efficiently released (heat is efficiently discharged) by returning the fuel in the fuel chamber 16 to the fuel tank 301 via the return passage 310, so that increases in the temperature of the fuel in the high-pressure pump 1 are restrained. The generation of vapor in the high-pressure pump 1 is suppressed to restrain the discharge amount control of the high-pressure pump 1 from being adversely affected. However, in the configuration in which the fuel in the fuel chamber 16 is returned to the fuel tank 301 via the return passage 310, pressure pulsation may occur in the fuel flowing through the return passage 310 and cause a detriment to the pulsation absorbing function of the pulsation damper 50. Thus, in this embodiment of the invention, the throttle 69 is provided in the connection passage 68 between the fuel chamber 16 and the return passage 310. The throttle 69 damps fuel pulsation. Therefore, fuel pulsation in the return passage 310 is suppressed, and deterioration in the pulsation absorbing function of the pulsation damper 50 is restrained.

The upstream end 683 of the inlet-side passage 681 may communicate with the fuel chamber 16 at a position on the other side of the fuel supply port 311 for supplying fuel to the fuel chamber 16 in a horizontal direction (in a lateral direction in FIG. 4) as in the case of the modified example 1 shown in FIG. 4. More specifically, the fuel supply port 311 communicates with the fuel chamber 16 on one side (on the left side in FIG. 4) in the horizontal direction. The upstream end 683 of the inlet-side passage 681, through which the fuel in the fuel chamber 16 is returned toward the fuel tank 301, communicates with the fuel chamber 16 on the other side (on the right side in FIG. 4) in the horizontal direction. That is, the upstream end 683 of the inlet-side passage 681 is provided on the other side of the fuel supply port 311 in the horizontal direction across a lateral center C1 of the pulsation damper 50. In this manner, the fuel supply port 311 and the upstream end 683 of the inlet-side passage 681 are arranged at diagonal positions across the lateral center C1 of the pulsation damper 50, so that the pulsation absorbing function of the pulsation damper 50 can be efficiently brought out.

Further, as in the case of the second modified example shown in FIG. 5, a guide member 58 that diverts the flow of the fuel in the fuel chamber 16 from the fuel supply port 311 toward the upstream end 683 of the inlet-side passage 681, may be provided in the fuel chamber 16. The guide member 58 diverts the flow of fuel introduced into the fuel chamber 16 from the fuel supply port 311 around the pulsation damper 50 and toward the upstream end 683 of the inlet-side passage 681. More specifically, the guide member 58 is configured so that the fuel from the fuel supply port 311 flows, in order, through a space 162, located below the pulsation damper 50, a space 163, located beside the pulsation damper 50 and on the other side of the fuel supply port 311 across the pulsation damper 50 (on the right side in FIG. 5), and a space 161, located above the pulsation damper 50, to the upstream end 683 of the inlet-side passage 681.

The guide member 58 is a plate-like member that vertically partitions the space between the fuel chamber 16 and the pulsation damper 50, and is provided between an inner face of the fuel chamber 16 and an outer face of the pulsation damper 50. The space 161, located above the pulsation damper 50, is partitioned from the space 162, located below the pulsation damper 50, by the guide member 58. The fuel supply port 311 communicates with the space 162 located below the pulsation damper 50, beside the pulsation damper 50 (on the left side in FIG. 5). The upstream end 683 of the inlet-side passage 681 communicates with the space 161 located above the pulsation damper 50, beside the pulsation damper 50 and on the same side as the fuel supply port 311.

An opening portion 581 is provided in the guide member 58 through which the space 161, located above the pulsation damper 50, is communicated with the space 162, located below the pulsation damper 50. The opening portion 581 is provided in the space 163 located beside the pulsation damper 50. In this case, the space 161 is communicated with the space 162 beside the pulsation damper 50 and only on the side of the fuel supply port 311 opposite the pulsation damper 50.

In the above configuration, the fuel returned to the fuel tank 301 is directed to flow through the space 162 located below the pulsation damper 50, the space 163 located beside the pulsation damper 50, and then the space 161 located above the pulsation damper 50 and guided to the upstream end 683 of the inlet-side passage 681 by the guide member 58. Thus, both the upper face of the pulsation damper 50 and the lower face of the pulsation damper 50 are utilized in damping the pulsation of fuel. Therefore, the pulsation absorbing function of the pulsation damper 50 is maximized.

Although the throttle 69 is provided at some point in the connection passage 68 in the above-described embodiment of the invention, the throttle 69 may be provided at an upstream end (at an end connected to the fuel chamber 16) or at a downstream end (at an end connected to the return passage 310) of the connection passage 68.

Although the above embodiment of the invention is described in the context of a V-6 engine, the invention is not restricted to the particulars of the described embodiment. The invention may be applied to other engines of any type and with any number of cylinders, such as, for example, inline four-cylinder engines. The invention is not restricted to gasoline engines, but may also be applied to other engines such as diesel engines. Furthermore, although the invention is described in the context of an engine equipped with port injection injectors and in-cylinder direct injection injectors in the preceding embodiment, the invention may also be applied to an engine equipped with in-cylinder direct injection injectors alone.

The invention may be employed in a high-pressure pump that includes a reciprocating plunger, a pressurization chamber in which fuel is pressurized by the plunger, and a housing having a fuel chamber which accommodates a pulsation damper and through which fuel flows.

Claims

1. A high-pressure pump comprising:

a plunger that moves in a reciprocating manner;

a pressurization chamber in which fuel is pressurized by the plunger;

a fuel chamber which accommodates a pulsation damper and through which fuel flows;

a housing in which the fuel chamber is formed;

a return passage through which fuel in the fuel chamber is returned toward a fuel tank, and which is connected to the fuel chamber; and

a connecting portion, which is provided with a throttle, and which connects the fuel chamber with the return passage.

2. The high-pressure pump according to claim 1, wherein the fuel chamber is provided with a fuel supply port for supplying fuel to this fuel chamber, and

the connecting portion is provided at a position on the other side of the fuel supply port across the pulsation damper.

3. The high-pressure pump according to claim 1, wherein a guide member, which directs fuel flowing from the fuel supply port toward the connecting portion, is provided in the fuel chamber and

the guide member is configured such that fuel introduced into the fuel chamber from the fuel supply port flows around the pulsation damper to reach the connecting portion.

4. The high-pressure pump according to claim 3, wherein the guide member directs fuel from the fuel supply port to flow sequentially through a space below the pulsation damper; a space beside the pulsation damper, on the opposite side of the fuel supply port across the pulsation damper; and a space above the pulsation damper before reaching the connecting portion.

5. The high-pressure pump according to claim 1, wherein the connecting portion includes an inlet-side passage and an outlet-side passage,

the throttle is provided between the inlet-side passage and the outlet-side passage, and

the throttle is smaller in passage cross-sectional area than both a downstream end of the inlet-side passage and an upstream end of the outlet-side passage.