Fuel pump

Abstract

This invention provides a fuel pump that prevents cavitation near a seat member in a valve mechanism. The fuel pump has a reciprocating plunger, a pressurized chamber whose volume increases or decreases due to the reciprocating motion of the plunger, and an overflow valve mechanism that returns fuel to the pressurized chamber. The overflow valve mechanism includes an overflow valve and a seat member having a valve contact portion for the overflow valve to sit on. The overflow valve is disposed on the plunger side relative to the seat member. The seat member has an annular groove forming a space communicating with the pressurized chamber between itself and a second chamber (fixed portion) surrounding the outer peripheral surface of the seat member. The space is located away from the plunger relative to the valve contact portion.

Description

Technical Field

[0001] This invention relates to a fuel pump that supplies fuel to an engine under high pressure. Background Technology

[0002] As a fuel pump, for example, it is described in Patent Document 1. The high-pressure fuel supply pump described in Patent Document 1 includes a housing, a suction valve, a discharge valve, and a relief valve.

[0003] The housing has a cylinder liner that slidably holds the plunger and serves as a stepped cylindrical space forming a pressurized chamber. The intake valve is open when no current is supplied to the solenoid coil, and opens when current is supplied to the solenoid coil to draw fuel into the pressurized chamber.

[0004] The discharge valve is assembled in the discharge valve housing of the housing, which is connected to the pressurization chamber via a fuel discharge port. High-pressure fuel, pressurized in the pressurization chamber, is supplied to the discharge valve. The discharge valve opens when the pressure of the supplied fuel reaches a predetermined pressure, and the fuel passing through the discharge valve is pressurized to the accumulator.

[0005] Furthermore, an overflow valve is assembled in the overflow valve housing of the housing, which is connected to the high-pressure area downstream of the discharge valve and is also connected to the pressurization chamber via a connecting passage. The overflow valve opens when the fuel pressure in the high-pressure area reaches a certain level, allowing the high-pressure fuel to flow back to the pressurization chamber.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2018 / 186219 Summary of the Invention

[0009] The technical problem to be solved by the invention

[0010] However, the high-pressure fuel supply pump described in Patent Document 1 repeatedly raises and lowers the pressure in the pressurization chamber by moving the plunger up and down. In such a high-pressure fuel supply pump, when the plunger descends and the pressure in the pressurization chamber decreases, cavitation may occur near the overflow valve plate on the depth side of the pressurization chamber. The cavitation ruptures when the plunger rises and the pressure in the pressurization chamber increases.

[0011] Cavitation occurs repeatedly near the relief valve plate, which is located away from the plunger. Therefore, corrosion can occur in the relief valve plate, potentially leading to loss of its sealing function. The susceptibility to cavitation varies with the plunger's movement speed. Therefore, cavitation is more likely to occur under conditions requiring high fuel flow rates or high engine speeds.

[0012] The object of the present invention is to provide a fuel pump that prevents cavitation from occurring near the seat component in the valve mechanism, in view of the above-mentioned problems.

[0013] Technical solutions for solving the problem

[0014] To address the aforementioned problems and achieve the objective of this invention, the fuel pump of this invention includes: a reciprocating plunger; a pressurized chamber whose volume increases or decreases due to the reciprocating motion of the plunger; and an overflow valve mechanism for returning fuel to the pressurized chamber. The overflow valve mechanism includes an overflow valve and a seat member having a valve contact portion for the overflow valve to sit on. The overflow valve is disposed on the plunger side relative to the seat member. The seat member has an annular groove portion forming a space communicating with the pressurized chamber between itself and a fixing portion surrounding the outer peripheral surface of the seat member. The space is disposed at a position away from the plunger relative to the valve contact portion.

[0015] Invention Effects

[0016] The fuel pump with the above structure can prevent cavitation from occurring near the seat component in the overflow valve mechanism.

[0017] Furthermore, issues, structures, and effects other than those mentioned above can be clarified through the following description of the implementation methods. Attached Figure Description

[0018] Figure 1 This is an overall structural diagram of a fuel supply system using a high-pressure fuel supply pump according to one embodiment of the present invention.

[0019] Figure 2 This is a longitudinal cross-sectional view (1) of a high-pressure fuel supply pump according to one embodiment of the present invention.

[0020] Figure 3 This is a longitudinal cross-sectional view (2) of a high-pressure fuel supply pump according to one embodiment of the present invention.

[0021] Figure 4 This is a horizontal cross-sectional view of a high-pressure fuel supply pump according to one embodiment of the present invention, viewed from above.

[0022] Figure 5 This is a longitudinal cross-sectional view (3) of a high-pressure fuel supply pump according to one embodiment of the present invention.

[0023] Figure 6 This is a longitudinal cross-sectional view of the periphery of the overflow valve mechanism according to one embodiment of the present invention.

[0024] Figure 7 This is an explanatory diagram showing the location of cavitation generation around the overflow valve mechanism according to one embodiment of the present invention. Detailed Implementation

[0025] 1. Implementation Method

[0026] The following describes a high-pressure fuel supply pump according to one embodiment of the present invention. Furthermore, common components in all figures are labeled with the same reference numerals.

[0027] [Fuel Supply System]

[0028] First, use Figure 1 This describes a fuel supply system using the high-pressure fuel supply pump (fuel pump) of this embodiment.

[0029] Figure 1 This is an overall structural diagram of the fuel supply system using the high-pressure fuel supply pump of this embodiment.

[0030] like Figure 1 As shown, the fuel supply system includes a high-pressure fuel supply pump (fuel pump) 100, an ECU (Engine Control Unit) 101, a fuel tank 103, a common rail 106, and multiple injectors 107. The components of the high-pressure fuel supply pump 100 are integrally assembled into the pump body 1.

[0031] Fuel in fuel tank 103 is drawn by feed pump 102 driven by a signal from ECU 101. The drawn fuel is pressurized to the appropriate pressure by a pressure regulator (not shown) and delivered to the low-pressure fuel inlet 51 of high-pressure fuel supply pump 100 via low-pressure piping 104.

[0032] A high-pressure fuel supply pump 100 pressurizes the fuel supplied from the fuel tank 103 and delivers it to the common rail 106. Multiple injectors 107 and a fuel pressure sensor 105 are installed on the common rail 106. The multiple injectors 107 are installed according to the number of cylinders (combustion chambers) and inject fuel according to the drive current output from the ECU 101. The fuel supply system of this embodiment is a so-called direct injection engine system in which the injectors 107 directly inject fuel into the cylinders of the engine.

[0033] The fuel pressure sensor 105 outputs the detected pressure data to the ECU 101. The ECU 101 calculates the appropriate fuel injection quantity (target fuel injection duration) and the appropriate fuel pressure (target fuel pressure) based on engine state quantities (such as crankshaft rotation angle, throttle valve opening, engine speed, fuel pressure, etc.) obtained from various sensors.

[0034] Furthermore, the ECU 101 controls the driving of the high-pressure fuel supply pump 100 and the multiple injectors 107 based on calculations of fuel pressure (target fuel pressure), etc. That is, the ECU 101 has a pump control unit that controls the high-pressure fuel supply pump 100 and an injector control unit that controls the injectors 107.

[0035] The high-pressure fuel supply pump 100 includes a pressure pulsation reduction mechanism 9, an electromagnetic suction valve mechanism 3 as a variable capacity mechanism, and an overflow valve mechanism 4 (see reference). Figure 2 ) and discharge valve mechanism 8. Fuel flowing in from low-pressure fuel inlet 51 passes through pressure pulsation reduction mechanism 9 and intake passage 10b to reach intake port 31b of electromagnetic intake valve mechanism 3.

[0036] Fuel flowing into the electromagnetic intake valve mechanism 3 passes through the valve section 32, flows through the intake passage 1d formed in the pump body 1, and then flows into the pressurization chamber 11. In the pressurization chamber 11, a plunger 2 is reciprocally inserted. The plunger 2 passes through the engine cam 91 (see reference). Figure 2 It conveys power and performs reciprocating motion.

[0037] In the pressurization chamber 11, fuel is drawn in from the electromagnetic intake valve mechanism 3 during the downward stroke of the plunger 2, and pressurized during the upward stroke. When the fuel pressure in the pressurization chamber 11 exceeds a specified value, the discharge valve mechanism 8 opens, and the high-pressure fuel is pumped to the common rail 106 via the discharge passage 12a. The discharge of fuel by the high-pressure fuel supply pump 100 is operated by opening and closing the electromagnetic intake valve mechanism 3. The opening and closing of the electromagnetic intake valve mechanism 3 is controlled by the ECU 101.

[0038] [High-pressure fuel supply pump]

[0039] Next, use Figures 2-6 Explain the structure of the high-pressure fuel supply pump 100.

[0040] Figure 2 This is a longitudinal section view (1) of the high-pressure fuel supply pump 100, taken from a section orthogonal to the horizontal direction. Figure 3 This is a longitudinal section view (Figure 2) of the high-pressure fuel supply pump 100, which is orthogonal to the horizontal direction. Figure 4 This is a horizontal cross-sectional view of the high-pressure fuel supply pump 100, taken from a section orthogonal to the vertical direction. Figure 5 This is a longitudinal section view (3) of the high-pressure fuel supply pump 100, taken from a section orthogonal to the horizontal direction. Figure 6 This is an explanatory diagram showing the overflow valve mechanism 4 in an enlarged form.

[0041] like Figure 2 As shown, the pump body 1 of the high-pressure fuel supply pump 100 is formed in a generally cylindrical shape. Figure 2 and Figure 3 As shown, the pump body 1 has a first chamber 1a, a second chamber 1b, a third chamber 1c, and a suction passage 1d inside. In addition, the pump body 1 is tightly attached to the fuel pump mounting part 90 and fixed with a plurality of bolts (screws) not shown.

[0042] The first chamber 1a is a cylindrical space provided in the pump body 1, and the center line 1A of the first chamber 1a is aligned with the center line of the pump body 1. One end of the plunger 2 is inserted into the first chamber 1a, and the plunger 2 reciprocates within the first chamber 1a. The first chamber 1a and one end of the plunger 2 form a pressurization chamber 11.

[0043] The second chamber 1b is a cylindrical space within the pump body 1, and its centerline is orthogonal to the centerline of the pump body 1 (the first chamber 1a). An overflow valve chamber, housing the overflow valve mechanism 4, is formed within this second chamber 1b. Furthermore, the diameter of the second chamber 1b (overflow valve chamber) is smaller than the diameter of the first chamber 1a. The first chamber 1a and the second chamber 1b are connected via a circular connecting hole 1e. Fuel passing through the overflow valve mechanism 4 returns to the pressurization chamber 11 through the connecting hole 1e.

[0044] The third chamber 1c is a cylindrical space provided in the pump body 1, continuous with the other end of the first chamber 1a. The centerline of the third chamber 1c coincides with the centerline 1A of the first chamber 1a and the centerline of the pump body 1, and the diameter of the third chamber 1c is larger than the diameter of the first chamber 1a. A cylinder 6, which guides the reciprocating motion of the plunger 2, is disposed in the third chamber 1c. As a result, the end face of the cylinder 6 can abut against the stepped portion (flat portion) between the first chamber 1a and the third chamber 1c, preventing the cylinder 6 from shifting towards the first chamber 1a.

[0045] Cylinder 6 is cylindrical and is pressed into the third chamber 1c of pump body 1 on its outer periphery. One end of cylinder 6 abuts against the top surface of the third chamber 1c (the step between the first chamber 1a and the third chamber 1c). Plunger 2 is in slidable contact with the inner circumferential surface of cylinder 6.

[0046] A fixing part 1x is provided in the pump body 1, which engages approximately at the center of the cylinder 6 along its axial direction. The fixing part 1x is formed to be plastically deformable. The fixing part 1x pulls the cylinder 6 upward ( Figure 2 (Push from above)

[0047] An O-ring 93, representing one specific example of a mounting bracket, is inserted between the fuel pump mounting section 90 and the pump body 1. This O-ring 93 prevents engine oil from leaking out of the engine (internal combustion engine) through the space between the fuel pump mounting section 90 and the pump body 1.

[0048] A tappet 92 is provided at the lower end of the plunger 2. The tappet 92 converts the rotational motion of the cam 91 mounted on the engine camshaft into up-and-down motion, which is transmitted to the plunger 2. The plunger 2 applies force to the cam 91 side via the retainer 15 and spring 16, pressing it against the tappet 92. The tappet 92 reciprocates along with the rotation of the cam 91. The plunger 2 and the tappet 92 reciprocate together, causing the volume of the pressure chamber 11 to change.

[0049] Furthermore, a sealing retainer 17 is disposed between the cylinder 6 and the retainer 15. The sealing retainer 17 is formed into a cylindrical shape into which the plunger 2 can be inserted, and has a secondary chamber 17a at its upper end, which is the cylinder 6 side. In addition, the sealing retainer 17 retains the plunger seal 18 at its lower end, which is the retainer 15 side.

[0050] The plunger seal 18 slidably contacts the outer periphery of the plunger 2, sealing the fuel in the auxiliary chamber 17a during the reciprocating motion of the plunger 2, preventing the fuel in the auxiliary chamber 17a from flowing into the engine. Furthermore, the plunger seal 18 prevents lubricating oil (including engine oil) that lubricates the sliding parts inside the engine from flowing into the pump body 1.

[0051] exist Figure 2 In the process, the plunger 2 reciprocates in the up-down direction. When the plunger 2 descends, the volume of the pressurization chamber 11 expands; when the plunger 2 rises, the volume of the pressurization chamber 11 decreases.

[0052] That is, the plunger 2 is configured to reciprocate in the direction that expands and contracts the volume of the pressurized chamber 11.

[0053] The plunger 2 has a large-diameter portion 2a and a small-diameter portion 2b. When the plunger 2 reciprocates, the large-diameter portion 2a and the small-diameter portion 2b are located in the secondary chamber 17a. As a result, the volume of the secondary chamber 17a increases or decreases due to the reciprocating motion of the plunger 2.

[0054] Sub-chamber 17a is connected to fuel passage 10c (see reference). Figure 5 It is connected to the low-pressure fuel chamber 10. When the plunger 2 descends, fuel flows from the auxiliary chamber 17a to the low-pressure fuel chamber 10, and when the plunger 2 rises, fuel flows from the low-pressure fuel chamber 10 to the auxiliary chamber 17a. This reduces the fuel flow to and from the pump during the suction or return stroke of the high-pressure fuel supply pump 100, and reduces pressure pulsations generated inside the high-pressure fuel supply pump 100.

[0055] like Figure 3 As shown, a low-pressure fuel chamber 10 is provided on the upper part of the pump body 1 of the high-pressure fuel supply pump 100. A suction connector 5, communicating with the low-pressure fuel chamber 10, is installed on the side of the pump body 1. The suction connector 5 connects to the fuel tank 103 (see reference 103). Figure 1 The fuel supplied is connected to the low-pressure piping 104. Fuel from the fuel tank 103 is supplied to the interior of the pump body 1 through the suction connector 5.

[0056] The suction connector 5 has a low-pressure fuel inlet 51 connected to the low-pressure piping 104 and a suction flow path 52 communicating with the low-pressure fuel inlet 51. Fuel passing through the suction flow path 52 is supplied to the low-pressure fuel chamber 10 through a suction filter 53 disposed inside the pump body 1. The suction filter 53 removes foreign matter present in the fuel, preventing foreign matter from entering the high-pressure fuel supply pump 100.

[0057] The low-pressure fuel chamber 10 is provided with a low-pressure fuel flow path 10a and an intake passage 10b (see reference). Figure 2 A pressure pulsation reduction mechanism 9 is provided in the low-pressure fuel flow path 10a. When fuel flowing into the pressurization chamber 11 returns to the suction passage 10b through the solenoid suction valve mechanism 3 in the open state, pressure pulsation is generated in the low-pressure fuel chamber 10. The pressure pulsation reduction mechanism 9 reduces the pressure pulsation waves generated in the high-pressure fuel supply pump 100 and the low-pressure piping 104.

[0058] The pressure pulsation reduction mechanism 9 is formed by a metal diaphragm damper with two corrugated disc-shaped metal plates attached to its outer periphery and an inert gas such as argon injected inside. The metal diaphragm damper of the pressure pulsation reduction mechanism 9 absorbs or reduces pressure pulsations through expansion / contraction.

[0059] The suction passage 10b and the suction port 31b of the electromagnetic suction valve mechanism 3 (see reference) Figure 2 The fuel flowing from the low-pressure fuel flow path 10a is connected to the intake port 31b of the electromagnetic intake valve mechanism 3 via the intake passage 10b.

[0060] like Figure 2 and Figure 4 As shown, the electromagnetic suction valve mechanism 3 is inserted into the suction valve chamber 30 formed in the pump body 1. The suction valve chamber 30 is located on the upstream side (suction passage 10b side) of the pressurization chamber 11 and is formed in a horizontally extending transverse hole. The electromagnetic suction valve mechanism 3 includes a suction valve seat 31, a valve part 32, a valve stem 33, a rod force spring 34, an electromagnetic coil 35, and an armature 36 that are pressed into the suction valve chamber 30.

[0061] The intake valve seat 31 is cylindrical, and a seating portion 31a is provided on its inner periphery. Furthermore, an intake port 31b is formed on the intake valve seat 31, extending from the outer periphery to the inner periphery. This intake port 31b communicates with the intake passage 10b in the aforementioned low-pressure fuel chamber 10.

[0062] A limiter 37 is provided in the suction valve chamber 30, opposite to the seating portion 31a of the suction valve seat 31. A valve portion 32 is disposed between the limiter 37 and the seating portion 31a. Furthermore, a valve force spring 38 is provided between the limiter 37 and the valve portion 32. The valve force spring 38 applies force to the valve portion 32 toward the seating portion 31a.

[0063] The valve section 32, by abutting against the seat section 31a, locks the connection between the suction port 31b and the pressurization chamber 11. When the valve section 32 locks the connection between the suction port 31b and the pressurization chamber 11, the electromagnetic suction valve mechanism 3 is in a closed state. On the other hand, the valve section 32, by abutting against the limiter 37, opens the connection between the suction port 31b and the pressurization chamber 11. When the valve section 32 opens the connection between the suction port 31b and the pressurization chamber 11, the electromagnetic suction valve mechanism 3 is in an open state.

[0064] The valve stem 33 passes through the cylindrical hole of the suction valve seat 31, and one end abuts against the valve part 32. The rod-applying spring 34 applies force to the valve part 32 in the opening direction, which serves as the limiter 37, through the valve stem 33. One end of the rod-applying spring 34 engages with the other end of the valve stem 33. The other end of the rod-applying spring 34 engages with the magnetic core 39, which is arranged to surround the rod-applying spring 34.

[0065] The end faces of the armature 36 and the magnetic core 39 are opposite each other. Furthermore, the armature 36 engages with a flange located in the middle of the valve stem 33. The electromagnetic coil 35 is arranged to wind around the magnetic core 39. A terminal component 40 is electrically connected to the electromagnetic coil 35, through which current flows.

[0066] When no current flows through the electromagnetic coil 35 and the coil is de-energized, the valve stem 33 is forced in the opening direction by the force of the rod-applying spring 34. This pushes the valve portion 32 in the opening direction. As a result, the valve portion 32 moves away from the seat portion 31a and abuts against the limiter 37, and the electromagnetic suction valve mechanism 3 is in the open state. That is, the electromagnetic suction valve mechanism 3 is a normally open type that opens when not energized.

[0067] In the open state of the electromagnetic suction valve mechanism 3, fuel from the suction port 31b passes between the valve section 32 and the seat section 31a, flows into the pressurization chamber 11 through multiple fuel passage holes (not shown) of the limiter 37 and the suction passage 1d. In the open state of the electromagnetic suction valve mechanism 3, the valve section 32 is in contact with the limiter 37, thus restricting the position of the valve section 32 in the opening direction. The gap between the valve section 32 and the seat section 31a in the open state of the electromagnetic suction valve mechanism 3 is the movable range of the valve section 32, which is called the opening stroke.

[0068] When current flows through the electromagnetic coil 35, the armature 36 is attracted towards the closing valve direction by the magnetic attraction of the magnetic core 39. As a result, the armature 36 moves against the force applied by the lever spring 34 and comes into contact with the magnetic core 39. When the armature 36 moves towards the closing valve direction, which is the side of the magnetic core 39, the valve stem 33 engaged by the armature 36 moves together with the armature 36. As a result, the valve part 32 is released from the force applied in the opening valve direction and moves towards the closing valve direction by the force applied by the valve spring 38. When the valve part 32 contacts the seat portion 31a of the suction valve seat 31, the electromagnetic suction valve mechanism 3 enters the closed valve state.

[0069] like Figure 4 and Figure 5 As shown, the discharge valve mechanism 8 is disposed in the discharge valve chamber 80 located on the outlet side (downstream side) of the pressurization chamber 11. The discharge valve mechanism 8 has a discharge valve seat 81 communicating with the pressurization chamber 11, a valve part 82 that contacts / separates from the discharge valve seat 81, a discharge valve spring 83 that applies force to the valve part 82 toward the discharge valve seat 81, and a discharge valve limiter 84 that determines the stroke (travel distance) of the valve part 82.

[0070] Furthermore, the discharge valve mechanism 8 has a plug 85 that prevents fuel leakage to the outside. A discharge valve limiter 84 is pressed into the plug 85. The plug 85 is welded to the pump body 1 at a welded portion 86. The discharge valve chamber 80 is opened and closed by a valve portion 82. This discharge valve chamber 80 communicates with a discharge valve chamber passage 87. The discharge valve chamber passage 87 is formed in the pump body 1.

[0071] Pump body 1 is equipped with a... Figure 2 A horizontal hole communicating with the second chamber 1b (overflow valve chamber) is shown, and a discharge connector 12 is inserted into this horizontal hole. The discharge connector 12 has the aforementioned discharge passage 12a communicating with the horizontal hole of the pump body 1 and the discharge valve chamber passage 87, and a fuel outlet 12b as one end of the discharge passage 12a. The fuel outlet 12b of the discharge connector 12 communicates with the common rail 106. In addition, the discharge connector 12 is fixed to the pump body 1 by welding via a welding part 12c.

[0072] When there is no fuel pressure difference (fuel pressure differential) between the pressurization chamber 11 and the discharge valve chamber 80 (discharge valve chamber passage 87), the valve part 82 is pressed against the discharge valve seat 81 by the force applied by the discharge valve spring 83, and the discharge valve mechanism 8 is in the closed state. When the fuel pressure in the pressurization chamber 11 is greater than the fuel pressure in the discharge valve chamber 80 (discharge valve chamber passage 87), the valve part 82 moves against the force applied by the discharge valve spring 83, and the discharge valve mechanism 8 is in the open state.

[0073] When the discharge valve mechanism 8 is in the open state, the (high-pressure) fuel in the pressurized chamber 11 passes through the discharge valve mechanism 8 and reaches the discharge valve chamber 80 (discharge valve chamber passage 87). The fuel reaching the discharge valve chamber passage 87 flows through the fuel discharge port 12b of the discharge connector 12 to the common rail 106 (see reference). Figure 1 Discharge. Based on the above structure, the discharge valve mechanism 8 functions as a check valve to restrict the direction of fuel flow.

[0074] Figure 2 and Figure 6The overflow valve mechanism 4 shown is configured to operate in the event that a problem occurs in the common rail 106, or in a component upstream of it, causing the common rail 106 to exceed a predetermined pressure and become high, thus returning fuel in the discharge passage 12a to the pressurization chamber 11. The discharge passage 12a is connected to the discharge valve chamber 80 via the discharge valve chamber passage 87. Therefore, the pressure in the discharge passage 12a is the same as the pressure in the discharge valve chamber 80.

[0075] The overflow valve mechanism 4 becomes open when the pressure difference between the discharge valve chamber 80 (discharge valve chamber passage 87) and the pressure in the second chamber 1b (overflow valve chamber) exceeds a set value.

[0076] The overflow valve mechanism 4 includes an overflow valve spring 41, an overflow valve retainer 42, an overflow valve 43, and a seat component 44. The overflow valve mechanism 4 is inserted from the discharge connector 12 and is disposed in the second chamber 1b (overflow valve chamber).

[0077] The relief valve spring 41 is a coil-shaped spring, with one end abutting against the pump body 1 (one end of the second chamber 1b). Furthermore, the other end of the relief valve spring 41 abuts against the relief valve retainer 42. The relief valve retainer 42 engages with the relief valve 43. The relief valve spring 41, when compressed, exerts a force on the relief valve retainer 42 and the relief valve 43 towards the seat member 44.

[0078] The seat component 44 is pressed into the second chamber 1b (overflow valve chamber). The seat component 44 has a fuel passage 44a opposite to the overflow valve 43. The side of the fuel passage 44a opposite to the overflow valve 43 communicates with the discharge passage 12a. The overflow valve 43 is pushed by the force applied by the overflow valve spring 41 and contacts the seat component 44. Thus, the overflow valve 43 blocks the fuel passage 44a of the seat component 44. The movement of fuel between the pressurized chamber 11 (upstream side) and the seat component 44 (downstream side) is blocked by the overflow valve 43 contacting (pressing against) the seat component 44 and blocking the fuel passage 44a.

[0079] When the pressure in the discharge valve chamber 80 (discharge valve chamber passage 87) and the component in front of the common rail 106 increases, the pressure difference with that in the second chamber 1b (relief valve chamber) exceeds a set value. As a result, the fuel on the seat component 44 side pushes against the relief valve 43, resisting the force applied by the relief valve spring 41, causing the relief valve 43 to move. Consequently, the relief valve 43 opens, and the fuel in the discharge passage 12a returns to the pressurization chamber 11 via the fuel passage 44a of the seat component 44. Thus, the pressure that causes the relief valve 43 to open is determined by the force applied by the relief valve spring 41.

[0080] [Operation of the high-pressure fuel pump]

[0081] Next, use Figure 2 , Figure 4 This describes the operation of the high-pressure fuel pump in this embodiment.

[0082] exist Figure 2 When the plunger 2 descends, fuel flows from the intake passage 1d into the pressurization chamber 11 when the electromagnetic intake valve mechanism 3 opens. Hereinafter, the stroke of the plunger 2 descending will be referred to as the intake stroke. Conversely, when the plunger 2 rises, fuel in the pressurization chamber 11 is pressurized when the electromagnetic intake valve mechanism 3 closes, and the fuel flows through the discharge valve mechanism 8 (see reference 8). Figure 4 And towards common orbit 106 (refer to) Figure 1 ) Pressurization. Hereinafter, the step in which the plunger 2 rises will be referred to as the rising stroke.

[0083] As described above, if the electromagnetic intake valve mechanism 3 closes during the ascending step, the fuel drawn into the pressurization chamber 11 during the intake stroke is pressurized and discharged towards the common rail 106 side. On the other hand, if the electromagnetic intake valve mechanism 3 opens during the ascending step, the fuel in the pressurization chamber 11 is pushed back towards the intake passage 1d side and is not discharged towards the common rail 106 side. Thus, the discharge of fuel by the high-pressure fuel supply pump 100 is operated by the opening and closing of the electromagnetic intake valve mechanism 3. The opening and closing of the electromagnetic intake valve mechanism 3 is controlled by the ECU 101.

[0084] During the intake stroke, the volume of the pressurized chamber 11 increases, and the fuel pressure within the pressurized chamber 11 decreases. As a result, the fluid pressure difference between the intake port 31b and the pressurized chamber 11 (hereinafter referred to as the "fluid pressure difference before and after the valve section 32") decreases. When the force exerted by the lever spring 34 is greater than the fluid pressure difference before and after the valve section 32, the valve stem 33 moves in the valve opening direction, the valve section 32 moves away from the seat portion 31a of the intake valve seat 31, and the electromagnetic intake valve mechanism 3 enters the open state.

[0085] When the electromagnetic intake valve mechanism 3 is in the open state, fuel from the intake port 31b passes between the valve section 32 and the seat section 31a, through multiple fuel passage holes (not shown) of the limiter 37, and flows into the pressurization chamber 11 from the intake passage 1d. In the open state of the electromagnetic intake valve mechanism 3, the valve section 32 is in contact with the limiter 37, thus restricting the position of the valve section 32 in the opening direction. The gap between the valve section 32 and the seat section 31a in the open state of the electromagnetic intake valve mechanism 3 is the movable range of the valve section 32, which is called the opening stroke.

[0086] After the intake stroke ends, the process transitions to the rising stroke. At this time, the electromagnetic coil 35 remains de-energized, and there is no magnetic attraction between the armature 36 and the magnetic core 39. For the valve section 32, the force in the valve-opening direction corresponding to the difference between the force applied by the rod force spring 34 and the valve force spring 38, and the force in the valve-closing direction caused by the fluid force generated when fuel flows backward from the pressurized chamber 11 to the low-pressure fuel flow path 10a, come into play.

[0087] In this state, to keep the electromagnetic suction valve mechanism 3 open, the difference in force applied by the lever force spring 34 and the valve force spring 38 is set to be greater than the fluid force. The volume of the pressurization chamber 11 decreases as the plunger 2 rises. Therefore, the fuel sucked into the pressurization chamber 11 will pass back through the valve section 32 and the seat section 31a, returning to the suction port 31b, and the pressure inside the pressurization chamber 11 will not rise. This stroke is called the return stroke.

[0088] In the return process, when from ECU101 (reference) Figure 1 When a control signal is applied to the electromagnetic suction valve mechanism 3, current flows through the terminal component 40 into the electromagnetic coil 35. When current flows into the electromagnetic coil 35, a magnetic attraction force acts between the magnetic core 39 and the armature 36, attracting the armature 36 (valve stem 33) towards the magnetic core 39. As a result, the armature 36 (valve stem 33) moves in the valve-closing direction (away from the valve section 32) against the force applied by the lever spring 34.

[0089] When the armature 36 (valve stem 33) moves toward the closing direction, the valve part 32 is released from the force applied in the opening direction and moves toward the closing direction due to the force applied by the valve force spring 38 and the fluid force caused by the fuel flowing into the suction passage 10b. When the valve part 32 contacts the sitting part 31a of the suction valve seat 31 (the valve part 32 sits on the sitting part 31a), the electromagnetic suction valve mechanism 3 becomes closed.

[0090] After the electromagnetic intake valve mechanism 3 is in the closed state, the fuel in the pressurization chamber 11 is pressurized along with the rising plunger 2. When the pressure reaches a specified level, it is discharged through the discharge valve mechanism 8 to the common rail 106 (see reference). Figure 1 The discharge stroke is referred to as the discharge stroke. That is, the upward stroke of the plunger 2 between the bottom dead center and the top dead center consists of the return stroke and the discharge stroke. The amount of high-pressure fuel discharged can be controlled by controlling the timing of energizing the solenoid coil 35 of the solenoid intake valve mechanism 3.

[0091] If the timing of energizing the solenoid coil 35 is advanced, the proportion of the return stroke in the rising stroke becomes smaller, and the proportion of the discharge stroke becomes larger. As a result, less fuel returns to the intake passage 10b, and more fuel is discharged under high pressure. Conversely, if the timing of energizing the solenoid coil 35 is delayed, the proportion of the return stroke in the rising stroke becomes larger, and the proportion of the discharge stroke becomes smaller. As a result, more fuel returns to the intake passage 10b, and less fuel is discharged under high pressure. Thus, by controlling the timing of energizing the solenoid coil 35, the amount of fuel discharged under high pressure can be controlled to the amount required by the engine (internal combustion engine).

[0092] [Seat assembly of the overflow valve mechanism]

[0093] Next, use Figure 6 and Figure 7 The seat component 44 of the overflow valve mechanism 4 in this embodiment is described.

[0094] Figure 7 This is an explanatory diagram showing the location of cavitation around the overflow valve mechanism 4.

[0095] As described above, the relief valve 43 is pushed against the seat member 44 by the spring force of the relief valve spring 41. The seat member 44 has a valve contact portion 44b in which the relief valve 43 contacts (seated). The relief valve mechanism 4 has a sealing function by the tight contact between the relief valve 43 and the valve contact portion 44b of the seat member 44. Therefore, when the relief valve 43 is in tight contact with the valve contact portion 44b of the seat member 44, the pressurized chamber 11, which includes the second chamber 1b, and the discharge passage 12a are liquid-tightly sealed.

[0096] Because the overflow valve mechanism 4 has a sealing function, in the plunger 2 (refer to...) Figure 6 When the pressure rises, the fuel in the pressurization chamber 11 can be pressurized. Furthermore, because the relief valve mechanism 4 has a sealing function, even after the plunger 2 stops moving, the pressure of the fuel in the discharge valve chamber 80 and the fuel pressure in the common rail 106 can be maintained. Therefore, the sealing function of the valve contact portion 44b is important in order to maintain the fuel pressure in the common rail 106.

[0097] Therefore, the valve contact portion 44b of the seat component 44 is located at the deepest part of the pressurization chamber 11, furthest from the plunger 2. In this case, when the plunger 2 descends and the fuel in the pressurization chamber 11 is depressurized, cavitation is generated in the space 47 near the valve contact portion 44b. When the plunger 2 rises and the fuel in the pressurization chamber 11 is pressurized, the cavitation ruptures.

[0098] In space 47, if cavitation occurs repeatedly near the valve contact 44b, corrosion will occur in a radially transverse annular manner across the valve contact 44b. As a result, there is a possibility of loss of the sealing function of the valve contact 44b. The susceptibility to cavitation varies depending on the movement speed of the plunger 2. Therefore, it is more likely to occur when the required fuel flow rate is high or when the engine (internal combustion engine) is rotating at high speed.

[0099] like Figure 7 As shown, an annular groove 45 is provided on the outer peripheral surface of one end of the seat member 44. By providing the annular groove 45, a generally circular flange 46 is formed at one end of the seat member 44.

[0100] The flange portion 46 is opposite to the overflow valve retainer 42. The diameter of the flange portion 46 is smaller than the diameter of the second chamber 1b. A valve contact portion 44b, continuous with the fuel passage 44a, is provided at the center of the flange portion 46. The valve contact portion 44b is formed as an annular tapered portion continuous with the fuel passage 44a. By providing the flange portion 46, even with the annular groove portion 45, the volume of the pressurized chamber 11 can be reduced, and the decrease in discharge efficiency can be suppressed.

[0101] Near the valve contact portion 44b of the flange portion 46, a space 47 is formed, which is surrounded by the overflow valve retainer 42, the overflow valve 43, and the flange portion 46. Furthermore, a space 48 is formed between the annular groove portion 45 and the second chamber 1b. The annular groove portion 45 and the space 48 are located at a position farther from the plunger 2 than the valve contact portion 44b.

[0102] As the plunger 2 descends, the fuel in the pressurization chamber 11 is depressurized. This depressurization begins at the deepest part of the pressurization chamber 11, furthest from the plunger 2. That is, the fuel in the pressurization chamber 11 is drawn from the deepest part during depressurization. As a result, cavitation can preferentially occur in the space 48. This prevents cavitation from occurring in the space 47 near the valve contact portion 44b.

[0103] A gap 61a is formed between the flange portion 46 and the overflow valve retainer 42. The area of ​​the peripheral surface of the gap 61a opposite to the second chamber 1b becomes the area of ​​the opening that connects the space 47 generated near the valve contact portion 44b to the plunger 2 side of the pressurization chamber 11. Hereinafter, the area of ​​the peripheral surface of the gap 61a will be referred to as the "opening area of ​​the gap 61a".

[0104] A gap 61b is formed between the outer peripheral surface 46a of the flange portion 46 and the inner peripheral surface of the second chamber 1b. The area of ​​the surface of the gap 61b orthogonal to the centerline of the second chamber 1b becomes the area of ​​the opening that connects the space 48 to the plunger 2 side of the pressurization chamber 11. Hereinafter, the area of ​​the surface of the gap 61b orthogonal to the centerline of the second chamber 1b will be referred to as the "opening area of ​​the gap 61b".

[0105] The opening area of ​​gap 61b is set to be larger than that of gap 61a. Increasing the opening area reduces pressure loss. The portion with smaller pressure loss experiences pressure change preferentially compared to the portion with larger pressure loss. That is, pressure change occurs preferentially in gap 61b compared to gap 61a.

[0106] As a result, cavitation can be preferentially generated in space 48. Therefore, in this embodiment, cavitation corrosion can be preferentially generated in any portion 45x of the annular groove 45. The opening area of ​​gap 61b is preferably set to, for example, at least 1.25 times the opening area of ​​gap 61a.

[0107] Furthermore, the volume of the space 48 formed by the annular groove 45 is larger than the volume of the space 47 generated near the valve contact portion 44b. This allows the locations where cavitation occurs to be dispersed within the space 48. As a result, the generation / rupture of cavitation does not repeatedly occur in the same location, thus suppressing the amount of cavitation corrosion occurring in the annular groove 45.

[0108] The gap 61b is set to a size that prevents foreign matter from detaching from the annular groove 45 due to cavitation corrosion from passing through. That is, the gap 61b is determined based on the size of foreign matter that is not desired to flow from the space 48 to the plunger 2 side of the pressurization chamber 11.

[0109] If the foreign matter is less than 0.2 mm, the impact of biting in the relief valve 43 on the valve seat performance is minimal. Therefore, the gap 61b can be set to, for example, less than 0.2 mm. This prevents foreign matter larger than 0.2 mm from flowing into the plunger 2 side of the pressurization chamber 11. As a result, the deterioration of the valve seat performance of the relief valve 43 can be suppressed, improving the quality of the high-pressure fuel supply pump 100.

[0110] Here, let distance 62a be the distance from the second chamber 1b (pump body 1) to the valve contact portion 44b in a direction orthogonal to the centerline of the second chamber 1b (the direction of movement of the overflow valve 43). Furthermore, let distance 62b be the distance from the end face of the flange portion 46 of the seat member 44 to the end of the annular groove portion 45 opposite to the flange portion 46 in a direction parallel to the centerline of the second chamber 1b.

[0111] As the plunger 2 descends, the fuel in the pressurization chamber 11 is depressurized. This depressurization begins at the deepest part of the pressurization chamber 11, furthest from the plunger 2. Therefore, the distance 62b is set longer than the distance 62a. Consequently, the fuel in the space 48 formed by the annular groove 45 begins to depressurize earlier than the fuel in the space 47. As a result, air pockets can be actively generated in the space 48.

[0112] In this embodiment, the overflow valve mechanism 4 is positioned in the pressurization chamber 11 at the position furthest from the plunger 2. Therefore, cavitation occurs in the overflow valve mechanism 4. However, if the suction valve mechanism or discharge valve mechanism is positioned in the pressurization chamber at the position furthest from the plunger, cavitation also occurs in the suction valve mechanism or discharge valve mechanism. In this case, the same space as the space 48 in this embodiment can be provided in the suction valve mechanism or discharge valve mechanism.

[0113] 2. Summary

[0114] As explained above, the high-pressure fuel supply pump 100 (fuel pump) of the above embodiment has a reciprocating plunger 2, a pressurized chamber 11 whose volume increases or decreases due to the reciprocating motion of the plunger 2, and an overflow valve mechanism 4 that returns fuel to the pressurized chamber 11. The overflow valve mechanism 4 includes an overflow valve 43 and a seat member 44 having a valve contact portion 44b on which the overflow valve 43 is seated. The overflow valve 43 is disposed on the plunger 2 side compared to the seat member 44. The seat member 44 has an annular groove 45 forming a space 48 communicating with the pressurized chamber 11 between a second chamber 1b (fixed portion) surrounding the outer peripheral surface of the seat member 44. The space 48 is located further away from the plunger 2 than the valve contact portion 44b. As a result, cavitation can preferentially occur in the space 48. Consequently, cavitation can be prevented from occurring in the space 47 near the valve contact portion 44b.

[0115] Furthermore, the overflow valve mechanism 4 of the high-pressure fuel supply pump 100 (fuel pump) in the above embodiment includes an overflow valve retainer 42 that holds the overflow valve 43. A space 47 (valve contact side space) is formed in the overflow valve mechanism 4, surrounded by the overflow valve 43, the overflow valve retainer 42, and the seat member 44. The area of ​​the opening connecting the space 48 to the plunger 2 side of the pressurization chamber 11 (the opening area of ​​gap 61b) is larger than the area of ​​the opening connecting the space 47 to the plunger 2 side of the pressurization chamber 11 (the opening area of ​​gap 61a). Therefore, pressure changes occur preferentially at the opening (gap 61b) connecting the space 48 to the plunger 2 side of the pressurization chamber 11 compared to the opening (gap 61a) connecting the space 47 to the plunger 2 side of the pressurization chamber 11. As a result, cavitation is more likely to occur in the space 48 than in the space 47.

[0116] Furthermore, in the above-described embodiment, the volume of space 48 in the overflow valve mechanism 4 is larger than the volume of space 47 (valve contact side space). This allows for the dispersion of cavitation sites within space 48, preventing repeated occurrences of cavitation in the same location within space 48. Consequently, the amount of cavitation corrosion occurring in the annular groove 45 can be suppressed.

[0117] Furthermore, the seat member 44 of the overflow valve mechanism 4 in the above embodiment has a flange portion 46 opposite to the overflow valve retainer 42. The flange portion 46 forms an opening that communicates the space 48 with the plunger 2 side of the pressurization chamber 11. By providing the flange portion 46, even if the annular groove portion 45 is provided, the volume of the pressurization chamber 11 can be reduced, and the decrease in discharge efficiency can be suppressed.

[0118] Furthermore, in the above embodiment, the gap between the outer peripheral surface 46a of the flange portion 46 and the second chamber 1b (fixed portion) is 0.2 mm or less. This prevents foreign objects larger than 0.2 mm from flowing into the plunger 2 side of the pressurization chamber 11. As a result, it is possible to suppress the deterioration of the valve seat performance of the overflow valve 43 and improve the quality of the high-pressure fuel supply pump 100.

[0119] Furthermore, in the moving direction of the overflow valve 43 in the above embodiment, the distance (distance 62b) from the end face of the seat member 44 opposite to the overflow valve holder 42 (end face of the flange portion 46) to the end of the annular groove portion 45 opposite to the overflow valve holder 42 side is longer than the distance (distance 62a) from the second chamber 1b (fixed portion) to the valve contact portion 44b in a direction orthogonal to the moving direction of the overflow valve 43. As a result, the fuel in the space 48 formed by the annular groove portion 45 begins to depressurize earlier than the fuel in the space 47. Consequently, air pockets can be actively generated in the space 48.

[0120] Furthermore, in the above-described embodiment, the seat component 44 of the overflow valve mechanism 4 is fixed to the second chamber 1b of the pump body 1. Therefore, compared to the case where a housing is provided in which the seat component and the overflow valve are assembled as a single unit, the number of components can be reduced.

[0121] Furthermore, the overflow valve mechanism 4 in the above-described embodiment can also be structured with a housing that integrally assembles the overflow valve spring, overflow valve retainer, overflow valve, and seat assembly. In this case, the overflow valve mechanism is fixed to the pump body of the high-pressure fuel supply pump as a single assembly component. In this case, a space that preferentially generates cavitation is formed between the housing and the seat assembly. As a result, the assembly of the overflow valve mechanism can be easily performed.

[0122] The embodiments of the fuel pump of the present invention, including their effects, have been described above. However, the fuel pump of the present invention is not limited to the above embodiments and various modifications can be made without departing from the spirit of the present invention. Furthermore, the above embodiments have been described in detail to make the present invention easy to understand, but are not limited to including all the structures described.

[0123] Explanation of reference numerals in the attached figures

[0124] 1: Pump body; 1a: Chamber 1; 1b: Chamber 2; 1c: Chamber 3; 1d: Suction passage; 1e: Connecting hole; 1x: Fixing part; 2: Plunger; 3: Electromagnetic suction valve mechanism; 4: Overflow valve mechanism; 5: Suction connector; 6: Cylinder; 8: Discharge valve mechanism; 9: Pressure pulsation reduction mechanism; 10: Low-pressure fuel chamber; 11: Pressurization chamber; 12: Discharge connector; 15: Retainer; 17: Sealing retainer; 17a: Secondary chamber; 18: Plunger seal; 30: Suction valve chamber; 42: Overflow valve retainer; 43: Overflow valve. Valve, 44: Seat component, 44a: Fuel passage, 44b: Valve contact, 45: Annular groove, 46: Flange, 46a: Outer peripheral surface, 47, 48: Space, 51: Low-pressure fuel intake, 52: Suction flow path, 53: Suction filter, 61a, 61b: Gap, 62a, 62b: Distance, 100: High-pressure fuel supply pump, 101: ECU, 102: Feed pump, 103: Fuel tank, 104: Low-pressure piping, 105: Fuel pressure sensor, 106: Common rail, 107: Injector.

Claims

1. A fuel pump comprising: a plunger reciprocating; a pressurized chamber whose volume increases or decreases due to the reciprocating motion of the plunger; and an overflow valve mechanism for returning fuel to the pressurized chamber, characterized in that: The relief valve mechanism includes a relief valve, a seat component having a valve contact portion for the relief valve to sit on, and a relief valve retainer for holding the relief valve. The overflow valve is positioned on the plunger side relative to the seat component. The seat component has an annular groove forming a space communicating with the pressurization chamber between itself and a fixing portion surrounding the outer peripheral surface of the seat component. The space is located away from the plunger compared to the valve contact portion. A valve contact side space is formed, surrounded by the overflow valve, the overflow valve retainer, and the seat component. The area of ​​the opening connecting the space to the plunger side of the pressurization chamber is greater than the area of ​​the opening connecting the valve contact side space to the plunger side of the pressurization chamber.

2. The fuel pump as claimed in claim 1, characterized in that: The volume of the space is greater than the volume of the space on the valve contact side.

3. The fuel pump as claimed in claim 1, characterized in that: The seat component has a flange portion opposite to the overflow valve retainer. The flange portion forms an opening that connects the space to the plunger side of the pressurized chamber.

4. The fuel pump as claimed in claim 3, characterized in that: The gap between the outer peripheral surface of the flange and the fixing part is less than 0.2 mm.

5. The fuel pump as claimed in claim 1, characterized in that: In the direction of movement of the overflow valve, the distance from the end face of the seat member opposite to the overflow valve holder to the end of the annular groove opposite to the overflow valve holder is greater than the distance from the fixing part to the valve contact part in a direction orthogonal to the direction of movement of the overflow valve.

6. The fuel pump as claimed in claim 1, characterized in that: The fixing part is a body component into which the plunger is inserted.

7. The fuel pump as claimed in claim 1, characterized in that: The overflow valve mechanism includes a housing that integrally assembles the overflow valve with the seat component. The fixing part is the housing.

8. A fuel pump comprising: a reciprocating plunger; a pressurized chamber whose volume increases or decreases due to the reciprocating motion of the plunger; and a valve mechanism communicating with said pressurized chamber, characterized in that: The valve mechanism includes a valve, a seat component having a valve contact portion for the valve to sit on, and a valve retainer for holding the valve. The valve is positioned on the plunger side relative to the seat component. The seat component has an annular groove forming a space communicating with the pressurization chamber between itself and a fixing portion surrounding the outer peripheral surface of the seat component. The space is located away from the plunger compared to the valve contact portion. A valve contact side space is formed, surrounded by the valve, the valve retainer, and the seat component. The area of ​​the opening connecting the space to the plunger side of the pressurization chamber is greater than the area of ​​the opening connecting the valve contact side space to the plunger side of the pressurization chamber.

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