JP5187255B2 - High pressure pump - Google Patents

Description

  The present invention relates to a high-pressure pump including a cylinder and a piston, and in particular, a fuel injection equipped with a high-pressure pump capable of reducing a leak amount of a high-pressure fluid overflowing from a sliding clearance between the cylinder and the piston. It is related to the pump.

[Conventional technology]
Conventionally, a cam ring or other member for transmitting a driving force is eccentrically assembled to a drive shaft driven by an internal combustion engine (engine) such as a diesel engine, and a cam ring that revolves without rotating as the drive shaft rotates. A fuel injection pump that reciprocally moves a piston slidably received in a cylinder hole of a cylinder is known (for example, see Patent Document 1).

As shown in FIG. 14, the fuel injection pump includes a pump element in which a suction valve 101 and a discharge valve 102 are assembled. This pump element constitutes a high-pressure pump that pressurizes and feeds the fuel sucked into the pressurizing chamber 105 to the engine side as the piston 104 reciprocates in the cylinder 103.
A cylinder inner surface 106 is formed on the inner peripheral surface of the cylinder 103 so that the outer peripheral surface of the piston 104 can slide back and forth. A piston side surface 107 is formed on the outer peripheral surface of the piston 104 so as to be slidably reciprocally supported by the cylinder inner surface 106 of the cylinder 103. The piston 104 is reciprocated by a cam 109 via a cam ring and tappet 108 (or cam ring) as the drive shaft driven by the engine rotates.

Here, the high pressure pump pressurizes the fuel sucked into the pressurizing chamber 105 with the reciprocation of the piston 104 to increase the pressure, and pumps the high pressure fuel to the engine side via the discharge valve 102. It is configured. Further, the high pressure pump is configured such that a part of the high pressure fuel pressurized in the pressurizing chamber 105 passes through a sliding clearance 110 formed between the inner peripheral surface of the cylinder 103 and the outer peripheral surface of the piston 104. It is configured to leak to the room side.
At this time, as shown in FIG. 15, the cylinder inner surface 106 of the cylinder 103 is expanded radially outward by the high-pressure fuel in the pressurizing chamber 105, and the piston side surface 107 of the piston 104 is radially inward. Reduce to.

[Conventional technical problems]
Incidentally, in recent years, there has been a demand for further increase in fuel injection pressure for the purpose of improving engine output and reducing NOx and the like discharged from the engine.
However, as shown in FIG. 16, the clearance amount formed between the cylinder inner surface 106 of the cylinder 103 and the piston side surface 107 of the piston 104 increases in accordance with a request for further increasing the fuel injection pressure. For example, when the outer diameter (piston diameter) of the piston 104 is 8.5 mm and the cylinder internal pressure (fuel pressure in the pressurizing chamber 105, fuel injection pressure, and pumping pressure) is 250 MPa, the inner surface of one side of the cylinder 103 and the piston 104 The gap with the side surface on one side expands by +10 μm compared to when the cylinder internal pressure is 200 MPa.
Therefore, the leak amount of fuel leaking from the pressurizing chamber 105 to the cam chamber side through the sliding clearance 110 is exponentially caused by the increase in the clearance amount accompanying the increase in the fuel injection pressure (pumping pressure). The problem of increasing arises.
As a result, the high-pressure pump performs useless work corresponding to the leak, and the engine efficiency is reduced.

Japanese Patent Laid-Open No. 2003-074439

  An object of the present invention is to suppress an increase in the amount of fluid leaking from the pressurizing chamber through the clearance by suppressing an increase in the amount of clearance accompanying an increase in the fluid pressure of the fluid. Is to provide.

  According to the first aspect of the present invention, as the piston reciprocates in the cylinder, the fluid sucked into the pressurizing chamber formed at the tip end side of the cylinder hole is pressurized and fed. The piston (the front end portion on the pressurizing chamber side) is provided with a concave portion opened at the front end surface facing the pressurizing chamber, and an outer peripheral wall portion surrounding the periphery of the concave portion in the circumferential direction. Further, since the recess and the pressurizing chamber communicate with each other, the high pressure fluid pressurized in the pressurizing chamber, that is, leaks from the pressurizing chamber through a clearance formed between the inner surface of the cylinder and the side surface of the piston. A pressure fluid equivalent to the pressure fluid to be introduced is introduced into the recess.

As a result, the fluid pressure of the fluid leaking through the clearance from the pressurizing chamber deforms the outer surface (the side surface of the piston) of the outer peripheral wall portion of the piston in the direction in which the clearance is to be expanded (the radially inner side of the piston). On the other hand, the fluid pressure of the fluid introduced from the pressurizing chamber into the recess of the piston deforms the inner surface of the outer peripheral wall of the piston in the direction of reducing the clearance (the radially outer side of the piston). Let For this reason, the deformation | transformation of the outer surface of the outer peripheral wall part of a piston, ie, the side surface of a piston, is canceled.
Accordingly, it is possible to cancel the deformation of the side surface of the piston that forms a clearance with the inner surface of the cylinder, and it is possible to suppress an increase in the clearance amount accompanying an increase in the fluid pressure. Accordingly, it is possible to suppress the occurrence of problems such as an increase in the amount of fluid leaking from the pressurizing chamber through the clearance as the fluid pressure is increased. Further, even when the fluid pressure is high, the amount of fluid leaking from the pressurizing chamber through the clearance can be reduced.

Moreover, according to this invention , the recessed part is formed in the radial inside by the thickness of an outer peripheral wall part rather than the outer surface of the side surface or outer peripheral wall part of a piston.
The recess is formed straight along the axial direction of the piston from the tip surface of the piston to the bottom of the recess. When the piston diameter is, for example, φ8.5 mm, it is desirable that the axial depth of the recess be a predetermined value (for example, 10 to 15 mm) or more in order to achieve the effect of the first aspect. Thereby, the recessed part of a piston is formed in the radial direction inner side of the clearance by the side of a pressurization chamber among the clearances formed between the inner surface of a cylinder, and the side surface of a piston.

Moreover, according to this invention , the solid center wall part which forms a hollow pocket (recessed part) between the inner surface of an outer peripheral wall part is provided in the radial inside rather than the inner surface of the outer peripheral wall part of a piston. And the hollow pocket is formed so that the circumference | surroundings of the center wall part of a piston may be surrounded in the circumferential direction (it is continuous with a cylinder shape). As a result, the dead volume at the top dead center of the piston can be reduced by providing the central wall portion so as to fill the internal space formed in the outer peripheral wall portion of the piston. The occurrence of defects can be suppressed.

Furthermore, according to the present invention , the piston has a body portion that reciprocates in the cylinder hole of the cylinder. Moreover, the outer peripheral wall part of a piston is a sleeve which has an outer diameter equivalent to the trunk | drum part of a piston. The sleeve is formed as a separate part with respect to the body portion of the piston .
Here, an annular step portion is formed between the side surface of the body portion of the piston and the outer surface of the central wall portion of the piston. Then, the sleeve is fitted and inserted into the outer surface of the central wall portion of the piston from the front end surface side of the piston in the pressurizing chamber side until the end portion of the sleeve comes into contact with the step portion of the piston. Can be positioned.

In particular, according to the present invention , the sleeve protrudes from the both axial end sides of the sleeve to the outer surface side of the central wall portion of the piston so as to be fitted to the outer surface of the central wall portion of the piston. and have a second fitting portion, the axial length of the first fitting portion is formed shorter than the axial length of the second fitting part.
According to invention of Claim 2 , the sleeve has the circumferential groove | channel which forms a hollow pocket between two 1st, 2nd fitting parts. The space in the circumferential groove is, for example, the inner surface (groove bottom surface of the circumferential groove) of the hollow pocket forming portion (thinned outer peripheral wall portion) formed between the two first and second fitting portions and the piston. It becomes a hollow pocket formed between the outer surface of the central wall part.

According to the third aspect of the present invention, the pressurizing chamber and the hollow pocket are provided at least on the sleeve side or the central wall side on the pressurizing chamber side (fitting portion) of the two first and second fitting portions. Is formed in the pressure introduction groove.
As a result, the hollow pocket in which the communication state with the pressurizing chamber was blocked by at least the pressurizing chamber side (the fitting portion) of the two first and second fitting portions was pressurized in the pressurizing chamber. High pressure fluid (pressure fluid) can be introduced. For this reason, the deformation | transformation of the outer surface of the outer peripheral wall part of a piston, ie, the outer surface of a sleeve, is canceled.
According to the fourth aspect of the present invention, a through hole that connects the pressurizing chamber and the hollow pocket is formed between the two first and second fitting portions (the sleeve).
As a result, the hollow pocket in which the communication state with the pressurizing chamber was blocked by at least the pressurizing chamber side (the fitting portion) of the two first and second fitting portions was pressurized in the pressurizing chamber. High pressure fluid (pressure fluid) can be introduced. For this reason, the deformation | transformation of the outer surface of the outer peripheral wall part of a piston, ie, the outer surface of a sleeve, is canceled.

It is sectional drawing which showed the supply pump (Example 1). It is the schematic which showed the pump element (high pressure pump) (Example 1). It is the graph which showed the relationship between the thickness of the plunger outer peripheral wall part of the front-end | tip part of a plunger, and clearance increase (Example 1). (Example 2) which is sectional drawing which showed the supply pump. (Example 2) which is the schematic which showed the pump element (high pressure pump). (Example 3) which is the schematic which showed the pump element (high pressure pump). (Example 4) which is sectional drawing which showed the supply pump. (Example 4) which is the schematic which showed the pump element (high pressure pump). (Example 4) which is the perspective view which showed the plunger sleeve of the front-end | tip part of a plunger. (Example 4) which showed the deformation | transformation of the plunger sleeve with respect to a plunger lateral load. (Example 4) which is the perspective view which showed the plunger sleeve of the front-end | tip part of a plunger. (Example 4) which is the perspective view which showed the plunger sleeve of the front-end | tip part of a plunger. (Example 4) which is the perspective view which showed the plunger sleeve of the front-end | tip part of a plunger. It is the schematic which showed the pump element (high pressure pump) (prior art). It is explanatory drawing which showed the state which the amount of leaks expands with expansion of a clearance (conventional technique). It is the graph which showed the relationship between a pressure and the amount of leaks (conventional technique).

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
An object of the present invention is to suppress an increase in the amount of clearance that accompanies a further increase in fuel injection pressure (pumping pressure) and to suppress an increase in the amount of fuel leaking from the pressurizing chamber through the clearance. Is provided with a recess (hollow pocket) opened at the tip surface facing the pressurizing chamber, and an outer peripheral wall portion surrounding the periphery of the hollow pocket in the circumferential direction. This was realized by introducing a high-pressure fuel equivalent to the high-pressure fuel leaking through the clearance into the hollow pocket.
Of the four examples described below, only the mode shown in FIGS. 11 and 12 in the fourth example is an application example of the present invention, and other modes are the first example and the first example. 2 and Example 3 are all reference examples to which the present invention is not applied.

[Configuration of Example 1]
1 to 3 show a first embodiment , FIG. 1 is a view showing a supply pump, and FIG. 2 is a view showing a pump element (high pressure pump).

A fuel supply device for an internal combustion engine according to the present embodiment is mounted in an engine room of a vehicle such as an automobile. For example, a common rail known as a fuel injection system for an internal combustion engine (engine) such as a diesel engine having a plurality of cylinders. It is comprised by the type fuel injection system (accumulation type fuel injection device).
This common rail fuel injection system includes a fuel injection pump (fuel supply pump: hereinafter referred to as a supply pump) having a built-in feed pump (not shown) for pumping low pressure fuel from a fuel tank on the low pressure side of the fuel system, and this supply. A common rail into which high-pressure fuel (pressure fluid, high-pressure fluid) is introduced from the discharge port of the pump, and a plurality of fuel injection valves (injectors) to which high-pressure fuel is distributed and supplied from each fuel outlet of the common rail. The high-pressure fuel accumulated inside is injected and supplied into the combustion chamber of each cylinder of the engine via each injector.
Here, the amount of current supplied to each solenoid valve (injector solenoid valve) of the plurality of injectors is configured to be controlled by an engine control unit (ECU).

The supply pump of the present embodiment includes a feed pump (low-pressure fuel pump, low-pressure supply pump) having a known structure and an aluminum pump housing (housing body) 1 that rotatably supports a pump drive shaft (camshaft) (not shown). An iron-based metal cylinder head 2 that is fastened and fixed to the pump housing 1 and an iron-based iron that reciprocally slides in a plunger sliding hole (piston sliding hole, cylinder bore, cylinder hole) 3 of the cylinder head 2. A plunger 4 made of metal, and the plunger 4 reciprocates in the plunger sliding hole 3 of the cylinder head 2 so that one side of the plunger sliding hole 3 in the axial direction (of the plunger sliding hole 3 This is a high-pressure fuel pump that pressurizes and pumps fuel sucked into a pressurizing chamber 5 formed on the front end side.
The supply pump is provided with a plurality of pump elements (high-pressure pumps constituted by a cylinder head 2 and a plunger 4) radially about a cam chamber 7 formed inside the pump housing 1.

A cylinder inner surface (plunger sliding surface, piston sliding surface) 8 is formed on the inner peripheral surface of each cylinder head 2 of the plurality of pump elements so that the outer peripheral surface of the plunger 4 can slide back and forth.
Each plunger 4 of the plurality of pump elements includes a columnar plunger body portion (piston body portion, plunger shaft portion) 9 that extends straight in the axial direction. A plunger side surface (cylinder sliding surface) 11 is formed on the outer peripheral surface of the plunger body 9 to form a cylindrical sliding clearance 6 with the cylinder inner surface 8 of the cylinder head 2.
The end portion (tip portion) in the pressurizing chamber on one end side in the axial direction of the plunger body 9 opens at the tip end surface (plunger end surface 12) in the axial direction of the plunger 4, and the back side (cam) A hollow pocket (cylindrical space) 13 is formed as a recess (axial hole) extending in the axial direction (axial direction) of the plunger 4 to the chamber side. The hollow pocket 13 opens toward the pressurizing chamber 5 and communicates directly with the pressurizing chamber 5. As a result, high-pressure fuel (pressure fluid) that has been pressurized and pressurized in the pressurizing chamber 5 is introduced into the hollow pocket 13.

A cylindrical plunger outer peripheral wall portion (piston sleeve) 15 is formed at the tip end portion of the plunger 4 in the axial direction so as to surround the periphery of the hollow pocket 13. A plunger side surface (cylinder sliding surface) that forms a cylindrical sliding clearance (sliding clearance on the pressure chamber side) 6 between the outer peripheral surface of the plunger outer peripheral wall portion 15 and the cylinder inner surface 8 of the cylinder head 2. ) 16 is formed.
Here, in the supply pump of this embodiment, the cylinder head 2 and the plunger 4 constitute a pump element (high pressure supply pump). Details of the pump element will be described later.

A cam chamber 7 to which fuel is supplied from a feed pump is formed inside the pump housing 1. Both ends of the cam chamber 7 are respectively closed by the cylinder heads 2. The cam chamber 7 is connected to a fuel tank. A cam 21, a cam ring 22, a bush 23, and a coil spring 24 are accommodated in the cam chamber 7.
In the feed pump, an inner rotor and an outer rotor are accommodated in a pump cover attached to the pump housing 1.
The camshaft is rotatably supported by the pump housing 1 via a bearing and is driven to rotate by an engine crankshaft. A drive pulley (not shown) that is belt-driven by a crank pulley coupled to the crankshaft is attached to the outer periphery of the camshaft in the axial direction.
In addition, a cam 21 having a circular cross section is integrally formed eccentrically with respect to the cam shaft at an intermediate portion in the axial direction of the cam shaft. An inner rotor of a feed pump is attached to the outer periphery of the rear end portion in the axial direction of the camshaft.

The cam ring 22 revolves around the cam shaft. The cam ring 22 is slidably held on the outer periphery of the cam 21 via a bush 23. The cam ring 22 has a quadrangular prism shape and a circular through hole. Plungers 4 that reciprocate following the revolution of the cam ring 22 are disposed on both sides (upper and lower sides in the figure) of the cam ring 22.
The bush 23 is formed in a cylindrical shape and is press-fitted into the through hole of the cam ring 22.
The coil spring 24 urges the tappet 25 integrated with the cam chamber side end portion of the plunger 4 in the axial direction to press the end face of the cam ring 22. That is, the tappet 25 is pressed against the cam ring 22 by the urging force of the coil spring 24.
The contact surface between the cam ring 22 and the tappet 25 of the plunger 4 is formed in a flat shape. Thereby, since rotation of the cam ring 22 is prevented, the cam ring 22 revolves without rotating while sliding with the tappet 25 as the cam 21 rotates.

Each cylinder head 2 tightened and fixed to the pump housing 1 with a fastening bolt or the like (fastened and coupled) includes a suction valve 26 that opens and closes a fuel supply passage, a discharge valve 27 that opens and closes a fuel discharge passage, and a discharge port inside. Each of the outlets 28 formed with is installed. Further, an overflow outlet 29 is assembled to the pump housing 1.
Here, in the middle of the fuel supply passage from the feed pump to each intake valve 26, one electromagnetic fuel metering valve (solenoid valve) for metering the intake fuel amount is attached. The amount of current supplied to the electromagnetic fuel metering valve is configured to be electronically controlled by the ECU. Thereby, the fuel discharge amount discharged from the outlet 28 of the supply pump is controlled.

The intake valve 26 includes a valve 31 that opens and closes a fuel supply passage for supplying fuel from the electromagnetic fuel metering valve to the pressurizing chamber 5, a return spring 32 that biases the valve 31 in the valve closing direction, and a washer 33. C ring 34 that constitutes a stopper for holding the valve shaft on the outer periphery of the valve, plug 35 that hermetically closes the opening of cylinder head 2, and between the contact surface of cylinder head 2 and the contact surface of plug 35 It is comprised by the valve body 36 etc. which were inserted | pinched between. The return spring 32 of the suction valve 26 is compressed and held between the seat surface of the C ring 34 and the seat surface of the valve body 36.
The discharge valve 27 includes a valve 37 that opens and closes a fuel discharge passage for pumping (discharging) high-pressure fuel from the pressurizing chamber 5 to the common rail side, a return spring 38 that urges the valve 37 in the valve closing direction, and this return. A spring seat 39 for receiving the spring load of the spring 38 is used.

Here, the fuel supply passage for sucking fuel into the pressurizing chamber 5 from the feed pump via the electromagnetic fuel metering valve and the suction valve 26 is constituted by each fuel passage composed of the fuel holes 41, 42 and the like. Has been.
Further, the high-pressure fuel pressurized by the expansion and contraction of the internal volume of the pressurizing chamber 5 with the reciprocating movement of the plunger 4 is fed and supplied to the common rail via the fuel holes 43 to 45 and the discharge port 46. It is configured.
Note that the fuel discharge passage for pumping high-pressure fuel from the pressurizing chamber 5 to the common rail side is constituted by fuel passages including fuel holes 43 to 45, a discharge port 46, and the like.

Next, details of the pump element of this embodiment will be described with reference to FIGS. 1 and 2.
As described above, the pump element is sucked into the pressurizing chamber 5 by reciprocatingly sliding in the plunger sliding hole 3 of the cylinder head 2 in which a cylinder bore having a circular cross section is formed. And a plunger 4 for pressurizing and feeding the fuel.
The cylinder head 2 has a cylindrical cylinder body (cylinder wall portion) in which a plunger sliding hole 3 is formed. A cylinder inner surface 8 is formed on the inner peripheral surface of the cylinder head 2 so that the plunger side surfaces 11 and 16 of the plunger body portion 9 and the plunger outer peripheral wall portion 15 can slide back and forth. The cylinder head 2 is fastened and fixed to the outer surface of the pump housing 1 using fastening bolts or the like.
In the cylinder head 2, a fuel discharge port (fuel discharge port of the pressurizing chamber 5) that connects the pressurizing chamber 5 and the fuel hole 43 is formed on the side surface (cylinder inner surface 8) of the pressurizing chamber 5. .

Further, the cylinder head 2 is assembled with a suction valve 26, a discharge valve 27 and an outlet 28. Further, the cylinder head 2 is provided with a plug fitting portion 47 for fastening and fixing the plug 35. Inside the plug fitting portion 47, a plug hole (a fitting recess having an inner diameter larger than that of the plunger sliding hole 3) 48 is formed. The plug hole 48 is provided on the same axis as the plunger sliding hole 3 and is hermetically closed by a plug 35 that is fastened and fixed to the plug fitting portion 47.
Note that the plunger sliding hole 3 of the cylinder head 2 is opened at the bottom surface (annular step portion) of the plug hole 48 opened to the outside.

The pressurizing chamber 5 includes an axial front end surface (plunger end surface 12) of the plunger 4, a front end side (opening end side) in the axial direction of the plunger sliding hole 3 of the cylinder head 2, and an axial line of the suction valve 26. This is a variable volume space surrounded by the pressure chamber side end surface (end surface of the valve body 36 of the suction valve 26) in the direction.
The sliding clearance 6 is a cylindrical gap formed between the cylinder inner surface 8 of the cylinder head 2 and the plunger body portion 9 and the plunger side surfaces 11 and 16 of the plunger outer peripheral wall portion 15. The sliding clearance 6 has a minimum gap size that allows the plunger 4 to smoothly slide back and forth within the plunger sliding hole 3 of the cylinder head 2. However, since a part of the high-pressure fuel pressurized and pressurized in the pressurizing chamber 5 due to the sliding clearance 6 leaks from the pressurizing chamber 5 to the cam chamber side, the pump efficiency is lowered. .

The plunger 4 reciprocates linearly between the top dead center and the bottom dead center following the revolution of the cam ring 22. The plunger 4 includes a solid cylindrical plunger body 9 and the like that are fitted and supported in the plunger sliding hole 3 of the cylinder head 2 so as to be reciprocally slidable.
The plunger body 9 is inserted into the plunger sliding hole 3 of the cylinder head 2 so as to be reciprocally slidable. A hook-shaped tappet 25 is integrally formed at the end of the plunger body 9 on the cam chamber side so as to face the end surface of the cam ring 22 disposed so as to surround the cam 21. . The tappet 25 projects into the cam chamber 7 from the plunger sliding hole 3 of the cylinder head 2. The tappet 25 is the largest outer diameter portion having the largest outer diameter in the plunger 4.
The plunger 4 is integrally formed with a hollow bottomed cylindrical tip portion on one end side (tip side, pressurizing chamber side) in the plunger axis direction with respect to the plunger body portion 9. Further, a plunger side surface (cylinder sliding surface) 11 is formed on the outer peripheral surface of the plunger body portion 9 so as to face the cylinder inner surface 8 of the cylinder head 2 with a sliding clearance 6 therebetween.

The distal end portion of the plunger 4 in the axial direction is opened at the plunger end surface 12, and a concave hollow pocket (hollow portion) 13 extending straight from the opening end side to the back side (bottom side) in the plunger axial direction, and the hollow pocket 13 has a cylindrical plunger outer peripheral wall portion (a piston outer peripheral wall portion, a piston sleeve, a plunger sleeve) 15 surrounding the periphery of 13 in the circumferential direction.
The hollow pocket 13 is a cylindrical space (fuel filling chamber) having a predetermined internal volume into which high pressure fuel can be introduced from the pressurizing chamber 5 and filled with high pressure fuel. The hollow pocket 13 has a wall thickness of the plunger outer peripheral wall portion 15 that is at least radially inward of the sliding clearance 6 on the pressurizing chamber side of the sliding clearance 6 and is closer to the plunger side surface 16 of the plunger outer peripheral wall portion 15. It is formed inward in the radial direction by the amount.
The hollow pocket 13 is formed by excavating (cutting) the plunger end surface 12 of the plunger 4 in the plunger axial direction.

  The hollow pocket 13 has a round hole-shaped axial hole extending straight in the plunger axial direction. On the back side of the axial hole, a bottom portion that closes (closes) the back side of the axial hole is provided. That is, on the closed end side of the hollow pocket 13 (opposite side to the pressurizing chamber side (cam chamber side)), a bottom portion that closes (closes) the back side of the hollow pocket 13 is provided. The pressurizing chamber 5 and the hollow pocket 13 are provided between the bottom of the axial hole and the pressurizing chamber side end surface of the suction valve 26 in the axial direction (end surface of the valve body 36 of the suction valve 26). A circular bottom surface (plane) facing each other is formed. That is, an opening as a communicating portion that communicates the internal space of the hollow pocket 13 and the pressurizing chamber 5 is formed on the opening end side (pressurizing chamber side) of the hollow pocket 13.

In addition, the hollow pocket 13 of this embodiment is a hollow that is an axial hole in order to obtain an effect of suppressing deformation of the plunger side surface 16 that forms the sliding clearance 6 with the cylinder inner surface 8 of the cylinder head 2. The axial depth of the pocket 13 is set to be deeper than a set value (for example, 10 mm).
The axial depth of the hollow pocket 13 is the plunger axial depth from the plunger end surface 12 (opening of the hollow pocket 13) of the plunger outer peripheral wall 15 to the bottom surface of the axial hole (bottom surface of the hollow pocket 13). That is. Further, the axial depth of the hollow pocket 13 may be set arbitrarily (for example, to be an optimum value for obtaining a deformation suppressing effect of the plunger side surface 16) within a predetermined range (for example, 10 to 15 mm). .

The plunger outer peripheral wall portion 15 is continuously installed in a cylindrical shape so as to surround the periphery of the hollow pocket 13 in the circumferential direction, and is configured as an integral part with respect to the plunger body portion 9. The plunger outer peripheral wall portion 15 is formed on the radially inner side of the sliding clearance 6 on the pressurizing chamber side. Further, the plunger outer peripheral wall portion 15 is installed so as to partition the sliding clearance 6 and the hollow pocket 13 on the pressurizing chamber side. Further, an R-shaped chamfering or a taper-shaped chamfering is performed on the plunger end surface side of the plunger outer peripheral wall portion 15.
An annular plunger end surface 12 facing the pressurizing chamber 5 is formed on the tip end surface in the axial direction of the plunger outer peripheral wall portion 15 (opening peripheral edge portion of the hollow pocket 13). The plunger end surface 12 faces the pressurizing chamber side end surface in the axial direction of the suction valve 26 (the pressurization chamber side end surface of the valve body 36 of the suction valve 26) with the pressurizing chamber 5 therebetween.

A plunger side surface 16 that continues from the plunger side surface 11 of the plunger body 9 is formed on the outer peripheral surface of the plunger outer peripheral wall portion 15. The plunger side surface 16 faces the cylinder inner surface 8 of the cylinder head 2 with a sliding clearance 6 therebetween.
As shown in the graph of FIG. 3, the increase amount of the sliding clearance 6 (clearance increase amount) which is a sliding portion between the cylinder inner surface 8 of the cylinder head 2 and the plunger side surface 16 of the plunger 4 is the plunger Since the thickness of the outer peripheral wall portion 15 is affected, the thickness of the plunger outer peripheral wall portion 15 is set (cut) so as to be an optimum value (for example, 1 to 5 mm, 3 mm).

[Operation of Example 1]
Next, the plunger 4 reciprocates in the axial direction in the plunger sliding hole 3 of the cylinder head 2 to pressurize the fuel sucked into the pressurizing chamber 5 from the feed pump to increase the pressure, and the high-pressure fuel is changed to the common rail. The operation of a supply pump used as a high-pressure pump that supplies pressure to the engine side or the engine side (injector side) will be briefly described with reference to FIGS.

When the camshaft of the supply pump is driven by a belt driven by the crankshaft of the engine and rotates, the plurality of plungers 4 reciprocally slide in the plunger sliding holes 3 of the cylinder head 2.
For example, when one plunger 4 located at the top dead center is lowered, the fuel pressure in the pressurizing chamber 5 is lowered. When the fuel pressure in the fuel supply passage (fuel holes 41, 42, etc.) becomes larger than the resultant force of the urging force of the return spring 32 and the fuel pressure in the pressurizing chamber 5, the valve 31 of the intake valve 26 is opened. I speak. That is, the valve 31 is detached from the valve seat surface of the valve body 36 and the fuel supply passage is opened. As a result, the fuel delivered from the feed pump is sucked into the pressurizing chamber 5 from the electromagnetic fuel metering valve through the fuel supply passage (fuel holes 41 and 42).

When the plunger 4 starts to rise again after reaching the bottom dead center, the fuel pressure in the pressurizing chamber 5 is increased, and the fuel pressure in the fuel supply passage (fuel holes 41, 42, etc.) is returned to the return spring. When it becomes lower than the resultant force of the urging force of 32 and the fuel pressure in the pressurizing chamber 5, the valve 31 of the suction valve 26 is closed. That is, the valve 31 is seated on the seat surface of the valve body 36 and the fuel supply passage is closed. At the same time, the fuel pressure in the pressurizing chamber 5 further increases.
When the fuel pressure in the pressurizing chamber 5 rises above the valve opening pressure of the discharge valve 27, the valve 37 of the discharge valve 27 opens, and the fuel holes 43 to 45 → the discharge port 46 from the pressurizing chamber 5 It is pumped and supplied into the common rail through a high-pressure pump pipe (fuel pipe).

  The other plunger 4 also slides back and forth between the top dead center and the bottom dead center in the same manner as the plunger 4 described above, so that the fuel in the other pressurizing chamber 5 is discharged from the discharge valve 27 and the high-pressure pump pipe. After that, it is fed by pressure into the common rail. As described above, the supply pump is configured such that the suction process (suction process) and the discharge process (discharge process) are performed for two cycles per rotation of the camshaft. The high-pressure fuel accumulated in the common rail can be supplied to the combustion chamber of each cylinder of the engine at a predetermined timing by driving the electromagnetic valve of the injector at an arbitrary injection timing.

[Effect of Example 1]
As described above, the pump element (high pressure pump) of this embodiment includes the plunger 4 that reciprocally slides within the plunger sliding hole 3 of the cylinder head 2.
The plunger 4 is opened at the tip end in the axial direction at the plunger end surface 12 facing the pressurizing chamber 5 between the end surface of the valve body 36 of the suction valve 26 with the pressurizing chamber 5 therebetween, and is closed from this opening end side. A concave hollow pocket 13 is formed that extends straight in the plunger axis direction to the end side (back side). The hollow pocket 13 opens toward the pressurizing chamber 5 and communicates directly with the pressurizing chamber 5. As a result, high-pressure fuel (pressure fluid) that has been pressurized and pressurized in the pressurizing chamber 5 is introduced into the hollow pocket 13.

In addition, a cylindrical plunger outer peripheral wall 15 is provided at the distal end of the plunger 4 in the axial direction so as to surround the periphery of the hollow pocket 13 in the circumferential direction.
Further, as shown in the graphs of FIGS. 3 and 16, for the purpose of reducing the increase amount of the sliding clearance 6 (clearance increase amount) accompanying the further increase in the fuel injection pressure, the plunger outer peripheral wall portion (thin wall) Part) 15 should be as thin as possible. For this reason, the thickness of the plunger outer peripheral wall portion 15 formed integrally with the plunger body portion 9 is set to an optimum value.

  As a result, the fuel pressure of the high-pressure fuel leaking from the pressurizing chamber 5 through the sliding clearance 6 to the cam chamber side is increased in the direction in which the sliding clearance 6 is to be expanded (the radially inner side of the plunger 4). The outer peripheral surface of the outer peripheral wall portion 15 is deformed. On the other hand, the outer peripheral wall portion of the plunger in the direction in which the fuel pressure of the high-pressure fuel introduced from the pressurizing chamber 5 into the hollow pocket 13 attempts to reduce the sliding clearance 6 (the radially outer side of the plunger 4). The inner peripheral surface of 15 is deformed. In other words, the outer peripheral surface of the plunger outer peripheral wall portion 15 is deformed in the direction in which the plunger diameter (piston diameter) is reduced (squeezing direction), whereas the inner peripheral surface of the plunger outer peripheral wall portion 15 is enlarged in the plunger diameter. Deform it in the direction to swell. For this reason, deformation of the outer peripheral surface of the plunger outer peripheral wall portion 15, that is, the plunger side surface 16 on the pressurizing chamber side in the axial direction of the plunger 4 is offset.

Therefore, it becomes possible to cancel the deformation of the plunger side surface 16 of the plunger outer peripheral wall portion 15 of the plunger 4, and to suppress the increase in the clearance amount accompanying the further increase in the fuel injection pressure (fluid pressure). it can. This suppresses the occurrence of problems such as an increase in the amount of fuel leaking from the pressurizing chamber 5 to the cam chamber through the sliding clearance 6 in response to a request for higher fuel injection pressure. can do. That is, even when the fuel injection pressure is increased to a predetermined value (for example, 250 MPa) higher than that of the conventional technique, the increase in the amount of fuel leaking from the pressurizing chamber 5 is reliably suppressed. Can do.
Thereby, since further increase in the fuel injection pressure can be realized, it is possible to improve the output of the engine and reduce NOx and the like.
Further, it is possible to provide a pump element that has a very small amount of fuel leaking from the pressurizing chamber 5 to the cam chamber through the sliding clearance 6 even when the fuel injection pressure (pressure feeding pressure) is high. Can do.

4 and 5 show Example 2, FIG. 4 shows a supply pump, and FIG. 5 shows a pump element (high pressure pump).

Here, the pumping pressure (cylinder internal pressure) of the pump element is fixed at 250 MPa, and the wall thickness of the plunger outer peripheral wall 15 at the tip end in the axial direction of the plunger 4 is variously changed to increase the sliding clearance 6 (clearance). The amount of increase) was investigated and the experimental results are shown in the graph of FIG.
As can be confirmed from the graph of FIG. 3, the increase amount of the sliding clearance 6 that is the sliding portion between the cylinder inner surface 8 of the cylinder head 2 and the plunger side surface 16 of the plunger 4, that is, the clearance increase amount, It can be seen that the thickness of the plunger outer peripheral wall 15 provided at the tip in the axial direction has a great influence.

Specifically, as shown in the graph of FIG. 3, as the thickness of the plunger outer peripheral wall portion 15 of the plunger 4 is thicker, the clearance increase amount increases, and the thickness of the plunger outer peripheral wall portion 15 of the plunger 4 increases. The thinner, the less clearance increase. For this reason, the amount of increase in the clearance may be smaller when the thickness of the plunger outer peripheral wall portion 15 at the tip end portion in the axial direction of the plunger 4 is made as thin as possible.
However, as in the first embodiment, the plunger outer peripheral wall portion 15 has a hollow pocket 13 having a predetermined internal volume capable of introducing high-pressure fuel (same pressure as fuel passing through the sliding clearance 6) from the pressurizing chamber 5. If the plunger outer peripheral wall portion 15 is formed to be radially inward and the wall thickness of the plunger outer peripheral wall portion 15 is very thin, the hollow pocket 13 is open to the pressurizing chamber side. There is a problem in that the dead volume at the top dead center position of the plunger 4 is increased and the pump efficiency is lowered.

Therefore, in the pump element (high pressure pump) of the present embodiment, both the thinning of the plunger outer peripheral wall portion (thin portion) 15 provided at the distal end portion in the axial direction of the plunger 4 and the reduction of the dead volume are achieved. For the purpose, the structure shown in FIGS. 4 and 5 is adopted.
The distal end portion of the plunger 4 in the axial direction has a cylindrical hollow pocket between a plunger outer peripheral wall portion 15 in which a fitting concave portion 14 having a circular cross section is formed inside and an inner peripheral surface of the plunger outer peripheral wall portion 15. 17 has a plunger block 18 made of iron-based metal that forms 17. On the end surface of the plunger block 18 in the axial direction in the pressurizing chamber side, a circular plunger end surface (tip end surface of the piston block) 51 serving as the end surface in the axial direction of the plunger 4 is formed. An annular plunger end surface 52 is formed on the cam chamber side end surface of the plunger block 18 in the axial direction. A cylindrical fitting convex portion 53 that protrudes in the axial direction from the plunger end surface 52 toward the cam chamber is formed at the center of the plunger end surface 52.

The fitting recess 14 is a hollow portion that opens at the plunger end surface 12 of the plunger outer peripheral wall portion 15 and is recessed in the axial direction from the opening side to the back side. Further, a fitting recess 54 is formed at the distal end surface in the axial direction of the plunger body 9 at the bottom surface of the fitting recess 14 and is recessed in the axial direction from the opening side to the back side. The fitting projection 53 of the plunger block 18 is press-fitted into the fitting recess 54. Thereby, the plunger block 18 which is a separate member is fixed to the plunger body 9.
The plunger outer peripheral wall portion 15 is a thin-walled portion whose thickness is reduced for the purpose of reducing the increase amount of the sliding clearance 6 that expands as the fuel injection pressure increases. The plunger outer peripheral wall portion 15 is configured as an integral part with respect to the plunger body portion 9 as in the first embodiment. Further, a plunger side surface 16 is formed on the outer peripheral surface of the plunger outer peripheral wall portion 15 as in the first embodiment.

The hollow pocket 17 is a cylindrical space formed between the inner peripheral surface of the plunger outer peripheral wall portion 15 and the outer peripheral surface of the plunger block 18, and opens at the plunger end surfaces 12, 51. It is a cylindrical recess that extends straight in the plunger axis direction to the cam chamber side. An annular opening that opens toward the pressurizing chamber 5 is formed at the opening end of the hollow pocket 17, and the hollow pocket 17 and the pressurizing chamber 5 communicate directly with each other. As a result, the high-pressure fuel having the same fuel pressure as the high-pressure fuel fed under pressure in the pressurizing chamber 5 is introduced into the hollow pocket 17 as in the hollow pocket 13 of the first embodiment.
The hollow pocket 17 has an axial depth set to a depth of a predetermined value (for example, 10 to 15 mm) or more.

  The plunger block 18 is configured as a separate part (separate member) with respect to the plunger body 9. The plunger block 18 is fitted into the fitting recess 14 so that the pressurizing chamber side end surface (plane) is positioned substantially on the same plane as the plunger end surface 12 of the distal end portion of the plunger 4 in the axial direction. The plunger block 18 is fitted into the fitting recess 14 in order to reduce the volume of the dead volume (inner space of the fitting recess 14) at the top dead center position of the plunger 4 during the pressurizing and pumping process of the pump element. It is. Thereby, the hollow pocket 17 is continuously formed in a cylindrical shape so as to surround the periphery of the plunger block 18 in the circumferential direction.

An annular plunger end surface 51 is formed on the tip end surface (pressure chamber side end surface) of the plunger block 18 in the axial direction. The plunger end surface 51 is opposed to the pressurizing chamber side end surface in the axial direction of the suction valve 26 (the pressurization chamber side end surface of the valve body 36 of the suction valve 26) with the pressurizing chamber 5 therebetween.
Further, a plunger end surface 52 which is a locked portion is formed on the end surface of the plunger block 18 on the cam chamber side. From the central portion of the plunger end surface 52, a fitting convex portion 53 that is press-fitted into a fitting concave portion 54 having an inner diameter smaller than that of the fitting concave portion 14 protrudes.
Further, an annular stepped portion for locking the plunger end surface 52 of the plunger block 18 is provided between the inner peripheral surface (groove side surface) of the fitting recess 14 and the inner peripheral surface (groove side surface) of the fitting recess 54. (Locking portion) 55 is formed. In the pump element of the present embodiment, the plunger block 18 is stepped from the opening end side (pressurizing chamber side) of the fitting recess 14 at the distal end in the axial direction of the plunger 4 to the plunger end surface 52 of the plunger block 18. The plunger block 18 can be positioned at the stepped portion 55 by being inserted into the fitting recess 14 until it abuts against the portion 55.

As described above, in the pump element (high pressure pump) of the present embodiment, the inner peripheral surface of the plunger outer peripheral wall portion 15 provided at the distal end portion in the axial direction of the plunger 4 and the distal end portion in the axial direction of the plunger 4 are arranged. A hollow pocket 17 is provided between the outer peripheral surface of the plunger block 18 fitted in the fitting recess 14 so as to be located on the radially inner side of the sliding clearance 6 on the pressurizing chamber side.
Thereby, it becomes possible to cancel the deformation of the outer peripheral surface of the plunger outer peripheral wall portion 15, that is, the plunger side surface 16 of the plunger 4, and the clearance amount accompanying the further increase in the fuel injection pressure (pumping pressure) is increased. Can be suppressed. As a result, an increase in the amount of fuel leaking from the pressurizing chamber 5 to the cam chamber through the sliding clearance 6 can be reliably suppressed.
Further, a columnar shape formed in the fitting recess 14 by inserting a plunger block 18 which is a separate member with respect to the plunger body 9 into the fitting recess 14 at the tip of the plunger 4 in the axial direction. The volume of the internal space (dead volume) can be reduced by the volume of the plunger block 18. Thereby, since the volume of the dead volume at the top dead center position of the plunger 4 at the time of the pressurizing and pumping process of the pump element can be significantly reduced, it is possible to suppress a decrease in pump efficiency of the pump element.

FIG. 6 shows a third embodiment and is a view showing a pump element (high pressure pump).

In the pump element (high pressure pump) of this embodiment, for the purpose of achieving both reduction in the thickness of the outer peripheral wall portion (thin portion) 15 of the plunger provided at the distal end portion in the axial direction of the plunger 4 and reduction in dead volume. The structure as shown in FIG. 6 is adopted.
The distal end portion of the plunger 4 in the axial direction is a plunger outer peripheral wall portion (thin wall portion) 15 that forms a sliding clearance (cylindrical gap) 6 on the pressurizing chamber side with the cylinder inner surface 8 of the cylinder head 2, and A plunger central wall portion (piston block) 19 is formed between the inner peripheral surface of the plunger outer peripheral wall portion 15 to form a cylindrical hollow pocket 17.

The plunger outer peripheral wall portion 15 is configured as an integral part with respect to the plunger body portion 9 as in the second embodiment.
The hollow pocket 17 is a cylindrical space formed between the inner peripheral surface of the plunger outer peripheral wall portion 15 and the outer peripheral surface of the plunger central wall portion 19. The hollow pocket 17 opens at the plunger end surfaces 12 and 56, and from the opening end side. It is a cylindrical recess that extends straight in the plunger axis direction to the back side (cam chamber side). As in the second embodiment, an annular opening that opens toward the pressurizing chamber 5 is formed at the open end of the hollow pocket 17, and the hollow pocket 17 and the pressurizing chamber 5 communicate directly with each other. ing. As a result, the high-pressure fuel having the same fuel pressure as that of the high-pressure fuel fed under pressure in the pressurizing chamber 5 is introduced into the hollow pocket 17 as in the hollow pocket 17 of the second embodiment.
The hollow pocket 17 has an axial depth set to a depth of a predetermined value (for example, 10 to 15 mm) or more.

Unlike the plunger block 18 of the second embodiment, the plunger central wall portion 19 is configured as an integral part with respect to the plunger body 9. The plunger central wall portion 19 is integrally formed with the plunger body portion 9 so that the pressurizing chamber side end surface (planar surface) thereof is positioned substantially on the same plane as the plunger end surface 12 of the plunger outer peripheral wall portion 15. .
An annular plunger end surface 56 is formed on the axial end surface (pressure chamber side end surface) of the plunger central wall portion 19. The plunger end surface 56 faces the pressurizing chamber side end surface in the axial direction of the suction valve 26 (the pressurization chamber side end surface of the valve body 36 of the suction valve 26) with the pressurizing chamber 5 therebetween.
As described above, in the pump element (high pressure pump) of this embodiment, the same effect as that of Embodiment 2 can be achieved.

FIGS. 7 to 13 show a fourth embodiment , FIG. 7 is a view showing a supply pump, and FIG. 8 is a view showing a pump element (high pressure pump).

  In the pump element (high pressure pump) of this embodiment, for the purpose of achieving both reduction in the thickness of the outer peripheral wall portion (thin portion) 15 of the plunger provided at the distal end portion in the axial direction of the plunger 4 and reduction in dead volume. The structure shown in FIGS. 7 to 13 is employed. A plunger sleeve that forms a sliding clearance (cylindrical gap) 6 on the pressurizing chamber side between the front end of the plunger 4 in the axial direction and the cylinder inner surface 8 of the cylinder head 2 (the outer peripheral wall of the piston, the piston Sleeve) 61 and a ferrous metal-made plunger central wall 63 that forms a hollow cylindrical pocket 62 between the inner peripheral surface of the plunger sleeve 61.

The plunger sleeve 61 is configured as a separate part (separate member) with respect to the plunger body 9. The plunger sleeve 61 is fitted and held on the outer peripheral surface of the plunger central wall 63.
An annular plunger end surface 64 is formed on the tip end surface in the axial direction of the plunger sleeve 61 (end surface on the pressurizing chamber side). The plunger end face 64 faces the pressurizing chamber side end face in the axial direction of the suction valve 26 (the pressurization chamber side end face of the valve body 36 of the suction valve 26) with the pressurizing chamber 5 therebetween. Further, a plunger end surface 65 which is a locked portion is formed on the end surface of the plunger sleeve 61 on the cam chamber side. A plunger side surface 66 is formed on the outer peripheral surface of the plunger sleeve 61 so as to form a cylindrical sliding clearance 6 with the cylinder inner surface 8 of the cylinder head 2.

The hollow pocket 62 is a cylindrical space formed between the inner peripheral surface of the plunger sleeve 61 and the outer peripheral surface of the plunger central wall 63, and is opened at the plunger end surfaces 64 and 67. It is a cylindrical recess that extends straight in the plunger axis direction to the cam chamber side. An annular opening opening toward the pressurizing chamber 5 is formed at the open end of the hollow pocket 62, and the hollow pocket 62 and the pressurizing chamber 5 are in direct communication. As a result, the high pressure fuel having the same fuel pressure as that of the high pressure fuel fed under pressure in the pressurizing chamber 5 is introduced into the hollow pocket 62 as in the hollow pocket 17 of the second embodiment.
The hollow pocket 62 has a depth in the axial direction set to a depth of a predetermined value (for example, 10 to 15 mm) or more.

The plunger central wall 63 is configured as an integral part with respect to the plunger body 9. An annular plunger end surface 67 is formed on the tip end surface (pressure chamber side end surface) in the axial direction of the plunger central wall 63. The plunger end surface 67 faces the pressurizing chamber side end surface in the axial direction of the suction valve 26 (the pressurization chamber side end surface of the valve body 36 of the suction valve 26) with the pressurizing chamber 5 therebetween. The plunger central wall 63 is a small-diameter portion having an outer diameter smaller than that of the plunger body (large-diameter portion) 9.
On the outer peripheral surface of the plunger central wall 63, an outer peripheral recess (small diameter portion) 69 is formed. The inner peripheral surface of the fitting portion 72 provided on the cam chamber side of the plunger sleeve 61 is press-fitted to the bottom surface of the outer peripheral recess 69 on the cam chamber side, that is, the outer peripheral surface of the plunger central wall 63 on the cam chamber side. ing. Thereby, the plunger sleeve 61 which is a separate member is fixed to the plunger body 9.

Next, details of the plunger sleeve 61 will be described with reference to FIGS. Here, FIG. 9, FIG. 11 thru | or FIG. 13 is the figure which showed the plunger sleeve.
The plunger sleeve 61 has a thin cylindrical portion 71 for the purpose of reducing the amount of increase in the sliding clearance 6 that increases as the fuel injection pressure increases, and the cam portion side in the axial direction of the cylindrical portion 71. And has a fitting portion 72 that is a thick portion that is thicker inward in the radial direction than the cylindrical portion 71.
The cylindrical portion 71 is provided on the pressurizing chamber side in the axial direction with respect to the fitting portion 72, is a maximum inner diameter portion (inner peripheral recess) having an inner diameter larger than the inner diameter of the fitting portion 72, and the fitting portion It is a thin portion that is thinner than 72. The cylindrical portion 71 has an inner peripheral surface located closer to the plunger sliding hole side (radially outward) than the inner peripheral surface of the fitting portion 72, and between the outer peripheral surface of the plunger central wall portion 63. A pocket forming portion for forming the hollow pocket 62 is formed.
An annular plunger end surface 64 is formed on the front end surface of the cylindrical portion 71. The plunger end face 64 faces the pressurizing chamber side end face in the axial direction of the suction valve 26 (the pressurization chamber side end face of the valve body 36 of the suction valve 26) with the pressurizing chamber 5 therebetween.

The fitting portion 72 is located on the outer peripheral surface side (radially inward side) of the plunger central wall portion 63 so as to be press-fitted to at least the cam chamber side of the outer peripheral surface of the plunger central wall portion 63 (the bottom surface of the outer peripheral recess 69). ). That is, the fitting portion 72 is a fitting convex portion (inner peripheral convex portion) that protrudes toward the bottom surface side of the outer peripheral concave portion 69 so as to be fitted to the bottom surface of the outer peripheral concave portion 69 of the plunger central wall portion 63. An annular plunger end surface 65 is formed on the cam chamber side end surface of the fitting portion 72. The plunger end surface 65 is a flat surface that contacts the stepped portion 73 of the plunger 4.
Further, an annular stepped portion 74 is formed between the inner peripheral surface of the cylindrical portion 71 and the inner peripheral surface of the fitting portion 72.

A plunger end surface (locked portion) 65 of the plunger sleeve 61 is provided between the outer peripheral surface of the plunger body 9 (plunger side surface 11) and the outer peripheral surface of the plunger central wall 63 (bottom surface of the outer peripheral recess 69). An annular stepped portion (locking portion) 73 to be locked is formed.
In the pump element of this embodiment, the plunger sleeve 61 is moved from the plunger end surface side (pressure chamber side) of the plunger central wall 63 until the plunger end surface 65 of the plunger sleeve 61 contacts the stepped portion 73. The plunger sleeve 61 can be positioned at the stepped portion 73 by being fitted to the outer periphery of the wall portion 63.
As described above, in the pump element of this embodiment, the same effect as that of Embodiment 2 can be achieved.

By the way, in the pump element of the present embodiment, as shown in FIG. 9, the plunger sleeve 61 is press-fitted to the outer circumferential surface of the plunger central wall 63 (the bottom surface of the outer circumferential recess 69) on the axial pressure chamber side of the plunger sleeve 61. A cylindrical portion (thin wall portion) 71 is provided which is thinner than the fitting portion 72 to be joined.
As a result, as shown in FIG. 10, the cylindrical portion 71 of the plunger sleeve 61 is caused by the plunger lateral load (force that presses the inner peripheral surface of the cylindrical portion 71 of the plunger sleeve 61 laterally by the plunger central wall portion 63: piston lateral load). There are concerns about deformation and damage.
The plunger lateral load is such that, for example, the lower end surface of the plunger 4 (a plane perpendicular to the axial direction of the plunger 4) is perpendicular to the axial direction of the plunger sliding hole 3 of the cylinder head 2 due to a malfunction in processing of the plunger 4. In the case where the plunger 4 is inclined, there is a possibility that the plunger 4 reciprocates in the plunger sliding hole 3 while being inclined obliquely with respect to the axial direction of the plunger sliding hole 3. In this case, the plunger 4 moves diagonally, a plunger lateral load in the direction of the arrow shown in the figure acts on the cylindrical portion 71 of the plunger sleeve 61, and is formed between the cylindrical portion 71 of the plunger sleeve 61 and the fitting portion 72. There is a possibility that the cylindrical portion 71 near the stepped portion 74 is broken.

Therefore, the plunger lateral load is supported as a countermeasure against breakage of the thin cylindrical portion 71 for the purpose of reducing the increase amount of the sliding clearance 6 that expands as the fuel injection pressure increases in the plunger sleeve 61. Alternatively, it is desirable to apply a receiving structure to the plunger sleeve 61 (see FIGS. 11 to 13).
First, the plunger sleeve 61 shown in FIG . 11 and FIG. 12 as an application example of the present invention is fitted to the outer peripheral surfaces on both sides in the axial direction of the plunger central wall 63 (the bottom surfaces on both sides in the axial direction of the outer peripheral recess 69). The first fitting portion on the pressure chamber 5 side that forms two fitting portions (thick wall portion and inner circumferential convex portion) that protrude from the both end sides in the axial direction of the plunger sleeve 61 to the bottom surface side of the outer circumferential concave portion 69. 81, a second fitting portion 82 on the opposite side of the pressurizing chamber 5 , and two first and second fitting portions 81, 82 connected between the first and second fitting portions 81, 82. The cylindrical portion (pocket forming portion) 83 is made thinner than the thickness of the cylindrical portion. The axial length of the first fitting portion 81 is shorter than the axial length of the second fitting portion 82.

The two first and second fitting portions 81 and 82 have outer peripheral recesses such that their inner peripheral surfaces (inner surface, inner surface) are press-fitted to the pressurizing chamber side and the cam chamber side of the outer peripheral recess 69. 69 is a fitting convex portion (outer peripheral convex portion) projecting to the bottom surface side (radially inner side) of 69.
The cylindrical portion 83 has a circumferential groove (inner peripheral recess) 84 that forms a cylindrical hollow pocket 62 between the outer peripheral surface of the plunger central wall 63 (the bottom surface of the outer peripheral recess 69).
In addition, an annular first step portion 85 is formed between the inner peripheral surface of the first fitting portion 81 and the inner peripheral surface of the cylindrical portion 83. An annular second stepped portion 86 is formed between the inner peripheral surface of the second fitting portion 82 and the inner peripheral surface of the cylindrical portion 83.
The pressure chamber 5 and the hollow pocket 62 are provided in at least the first fitting portion 81 on the pressure chamber side of the two first and second fitting portions 81 and 82 of the plunger sleeve 61 shown in FIG. A communicating path (pressure introduction groove, slit groove) 87 that communicates is formed. As a result, high-pressure fuel that has been pressurized in the pressurizing chamber 5 and increased in pressure is introduced into the hollow pocket 62.

A cylindrical portion 83 formed between the two first and second fitting portions 81 and 82 of the plunger sleeve 61 shown in FIG. 12 has a communication passage (through hole) that allows the pressurizing chamber 5 and the hollow pocket 62 to communicate with each other. ) 88 is formed. As a result, high-pressure fuel that has been pressurized in the pressurizing chamber 5 and increased in pressure is introduced into the hollow pocket 62.
As described above, the plunger sleeve 61 shown in FIG. 11 and FIG. 12 is thick-fitted with a thicker portion than the cylindrical portion 83 of the plunger sleeve 61 (2 which is press-fitted to the outer peripheral surface of the plunger central wall portion 63. Since the first and second fitting portions 81 and 82) are provided on both end sides in the axial direction of the plunger sleeve 61, the plunger lateral load can be supported or received, so that the plunger sleeve 61 is reliably deformed or damaged. Can be prevented.

Next, the plunger sleeve 61 shown in FIG. 13 has a fitting portion (inner peripheral convex portion) that protrudes to the bottom surface side of the outer peripheral concave portion 69 so as to be fitted to the outer peripheral surface of the plunger central wall portion 63 (the bottom surface of the outer peripheral concave portion 69). 91. As for this fitting part 91, the inner peripheral surface (inner surface, inner surface) fits with the outer peripheral surface of the plunger central wall 63 on the cam chamber side in the axial direction (bottom surface of the outer peripheral recess 69 on the cam chamber side in the axial direction). A base portion to be joined and a plurality of protrusions (inner peripheral convex portions) 92 provided at predetermined intervals (for example, equal intervals) in the inner peripheral direction of the plunger sleeve 61 are provided.
The plurality of protruding portions 92 have fitting portions 91 such that inner peripheral surfaces (inner surface, inner surface) thereof are along the outer peripheral surface of a cylindrical portion 93 formed so as to surround the periphery of the hollow pocket 62 in the circumferential direction. Of the base portion of the base portion extends straight toward the pressurizing chamber side (suction valve side) in the axial direction.
A plurality of axial grooves 94 that form hollow pockets 62 are formed between the inner peripheral surface of the cylindrical portion 93 and the pressurizing chamber at least on the bottom surface of the outer peripheral recess 69. The plurality of protrusions 92 and the plurality of axial grooves 94 are alternately and repeatedly formed at predetermined intervals in the inner circumferential direction of the cylindrical portion 93 of the plunger sleeve 61.

As described above, the plunger sleeve 61 shown in FIG. 13 has a thicker portion (fitting portion 91 press-fitted and fitted to the bottom surface of the outer peripheral recess 69) thicker than the cylindrical portion 93 of the plunger sleeve 61. A thick wall portion provided on the cam chamber end side in the axial direction of the sleeve 61 and thicker than the cylindrical portion 93 of the plunger sleeve 61 (a plurality of protrusions 92 press-fitted to the bottom surface of the outer peripheral recess 69). Is installed at a predetermined interval in the circumferential direction of the cylindrical portion 93 of the plunger sleeve 61, so that the plunger lateral load can be supported or received, so that the plunger sleeve 61 can be reliably prevented from being deformed or damaged.
The plunger sleeve 61 shown in FIG. 13 is superior in strength to the plunger sleeve 61 shown in FIGS. 11 and 12.

[Modification]
In this embodiment, an example in which a supply pump (fuel supply pump) including a pump element (high pressure pump) according to the present invention is applied to a supply pump used in a common rail fuel injection system (accumulation fuel injection device) will be described. However, the supply pump (fuel supply pump) provided with the pump element (high-pressure pump) of the present invention is used as a distribution type supply pump or a column type supply pump used in a fuel supply device for an internal combustion engine or a fuel injection device for an internal combustion engine. You may apply to.
The number of pump elements (high pressure pumps) built in the supply pump, that is, the number of plungers 4 and cylinders may be one, two, three or more, and the number is arbitrary. Also, the number of intake valves 26 may be one, two, three or more according to the number of pump elements, and the number is arbitrary.
The pump element (high pressure pump) of the present invention may be applied to a high pressure pump that pressurizes and feeds fluid (liquid) such as liquid fuel (gasoline) other than diesel oil, hydraulic oil, oil, water or the like.

In the present embodiment, the position of the fuel discharge port of the pressurizing chamber 5 is opposite to the pressurizing chamber side (cam) than the position of the top dead center of the plunger end surface of the plunger 4 (plunger end surface facing the pressurizing chamber 5). The chamber side: located on the lower side in the figure or the upper side in the figure, but the position of the fuel discharge port of the pressurization chamber 5 is higher than the position of the top dead center of the plunger end surface of the plunger 4 (upper side in the figure). Alternatively, it may be located on the lower side in the figure.
When the position of the fuel discharge port of the pressurizing chamber 5 is located closer to the cam chamber than the position of the top dead center of the plunger end surface of the plunger 4, the pressurizing chamber 5 is connected to the fuel discharge passage such as the fuel hole 43. When the plunger end surface of the plunger 4 is at the top dead center, the clearance between the cylinder inner surface 8 of the cylinder head 2 and the plunger side surface 11 of the plunger 4 is greater than the sliding clearance 6. The cylinder inner surface 8 of the cylinder head 2 may be recessed radially outward so as to form a wide clearance. That is, the inner diameter (cylinder bore diameter) of the pressurizing chamber 5 may be larger on the suction valve side than on the cam chamber side (see FIGS. 1, 4 and 7).

  In the present embodiment, as shown in FIG. 9, the inner side in the radial direction from the cylindrical portion (thin portion) 71 on the opposite side (cam chamber side) to the pressurizing chamber side in the axial direction of the plunger sleeve 61. By providing a thickened fitting portion (inner peripheral convex portion) 72, and fitting the inner peripheral surface (inner surface, inner surface) of the fitting portion 72 to the bottom surface of the outer peripheral concave portion 69 of the plunger central wall portion 63, The plunger sleeve 61 is fixed to the outer peripheral surface (outer surface, outer surface) of the plunger central wall portion 63. The plunger sleeve 61 is a simple cylindrical cylindrical body, and from the bottom surface of the outer peripheral recess 69 of the plunger central wall portion 63. A fitting portion (annular or cylindrical outer peripheral convex portion) protruding on the inner peripheral surface side (inner surface side) of the plunger sleeve 61 is provided, and a plunger is provided on the outer peripheral surface (outer surface, cylindrical surface, outer surface) of this fitting portion. Fits the inner peripheral surface (inner surface, inner surface) of the sleeve 61 In Rukoto, the outer peripheral surface of the plunger center wall portion 63 (the outer surface, an outer surface) may be fixed to the plunger sleeve 61.

In the present embodiment, as shown in FIGS. 11 and 12, the two first thickenings are formed radially inwardly of the cylindrical portion (thin wall portion) 83 at both end sides in the axial direction of the plunger sleeve 61. The second fitting portions (inner peripheral convex portions) 81 and 82 are provided, and the inner peripheral surfaces (inner surface and inner side surface) of the first and second fitting portions 81 and 82 are formed on the outer peripheral concave portion 69 of the plunger central wall portion 63. By fitting the plunger sleeve 61 to the outer peripheral surface (outer surface, outer surface) of the plunger central wall 63 by fitting to the bottom surface, the plunger sleeve 61 has a structure for supporting or receiving the plunger lateral load (piston lateral load). However, the plunger sleeve 61 is a simple cylindrical cylindrical body, and both sides or one side in the axial direction of the outer peripheral recess 69 of the plunger central wall 63 (the pressure chamber side, the opposite side to the pressure chamber side (cam Room side) bottom Provided with one or a plurality of fitting portions (annular or cylindrical outer peripheral convex portions) protruding on the inner peripheral surface side (inner surface side) of the plunger sleeve 61. The inner peripheral surface (inner surface, inner surface) of the plunger sleeve 61 is fitted to the outer surface, cylindrical surface, outer surface), and the plunger sleeve 61 is fixed to the outer peripheral surface (outer surface, outer surface) of the plunger central wall 63. Thus, the plunger sleeve 61 may not be broken even if a plunger lateral load (piston lateral load) acts on the plunger sleeve 61.
In this case, a pressure introduction groove that communicates the pressurizing chamber 5 and the hollow pocket 62 is formed on either the sleeve side or the central wall side of the fitting portion of the plunger central wall portion 63, or It is desirable to form a pressure introducing hole for communicating the pressurizing chamber 5 and the hollow pocket 62. Thereby, the high pressure fuel (pressure fluid) pressurized in the pressurizing chamber can be introduced into the hollow pocket 62 in which the communication state with the pressurizing chamber 5 is blocked by the fitting portion of the plunger central wall 63. .
A circumferential groove that forms the hollow pocket 62 may be provided on the opposite side (cam chamber side) to the pressurizing chamber side in the axial direction of the plunger central wall 63 from the fitting portion.

In this embodiment, as shown in FIG. 13, a base portion of a fitting portion (inner peripheral convex portion) 91 is provided on the opposite side (cam chamber side) to the pressurizing chamber side of the plunger sleeve 61 in the axial direction. Further, a plurality of protrusions (inner peripheral convex portions) 92 are provided so as to extend from the base portion toward the pressurizing chamber side (suction valve side) in the axial direction of the plunger sleeve 61, and the inner portions of the base portions of these fitting portions 91 are provided. The peripheral surface (inner surface, inner surface) and the inner peripheral surface (inner surface, inner surface) of the plurality of protrusions 92 of the fitting portion 91 are fitted to the bottom surface of the outer peripheral recess 69 of the plunger central wall portion 63 to thereby move the plunger central wall. The plunger sleeve 61 is fixed to the outer peripheral surface (outer surface, outer surface) of the portion 63 to support or receive the plunger lateral load (piston lateral load). Cylindrical shape A cylindrical body is formed on the inner peripheral surface side (inner surface side) of the plunger sleeve 61 from the bottom surface on one side (opposite side to the pressurizing chamber side (cam chamber side)) of the outer peripheral recess 69 of the plunger central wall 63. A protruding fitting portion (annular or cylindrical outer peripheral convex portion) is provided, and from the base portion of this fitting portion to the pressurizing chamber side (suction valve side) in the axial direction of the outer peripheral concave portion 69 of the plunger central wall portion 63. A plurality of protrusions (outer peripheral protrusions) are provided to extend, and the inner peripheral surface of the plunger sleeve 61 is provided on the outer peripheral surface (cylindrical surface) of the base portion of the fitting portion and the outer peripheral surface (top surface) of the plurality of protrusions. (Inner surface, inner surface) are fitted and the plunger sleeve 61 is fixed to the outer peripheral surface (outer surface, outer surface) of the plunger central wall 63, so that a plunger lateral load (piston lateral load) acts on the plunger sleeve 61. Even then, the plunger sleeve 61 will not break. It may be so.
In this case, it is desirable to provide a plurality of axial grooves that form the hollow pocket 62 on at least the pressurizing chamber side of the bottom surface of the outer peripheral recess 69 of the plunger central wall 63 (the outer surface of the plunger central wall 63). The axial groove is formed between two protrusions adjacent in the outer peripheral direction on the bottom surface of the outer peripheral recess 69 of the plunger central wall 63 (the outer surface of the plunger central wall 63). Further, the axial pressure chamber side of the plurality of axial grooves opens toward the pressurizing chamber 5 similarly to the axial groove 94 shown in FIG. High-pressure fuel (pressure) pressurized in a pressurizing chamber in a hollow pocket 62 formed between the groove bottom surface of the directional groove 94 (outer surface of the plunger central wall 63) and the inner peripheral surface (inner surface) of the plunger sleeve 61 Fluid) can be introduced.
A plurality of protrusions extending from the base portion of the fitting portion toward the pressurizing chamber side (suction valve side) in the axial direction are installed at predetermined intervals (for example, equal intervals) in the outer peripheral direction of the plunger central wall portion 63. May be.

1 Pump housing 2 Cylinder head (cylinder)
3 Plunger sliding hole (cylinder hole, piston sliding hole)
4 Plunger (piston)
5 Pressurizing chamber 6 Sliding clearance 7 Cam chamber 8 Cylinder inner surface (cylinder inner surface)
9 Plunger body (piston body, plunger shaft)
11 Plunger side (side surface of piston body)
12 Plunger end face (piston end face)
13 Hollow pocket (recess, cylindrical space)
14 Fitting recess (hollow part)
15 Plunger outer wall (piston sleeve)
16 Plunger side surface (side surface of piston outer wall)
17 Hollow pocket (recess, cylindrical space)
18 Plunger block (piston central wall, piston block)
19 Plunger central wall (piston block)
51 Plunger end face (tip face of piston block)
52 Plunger end face (Piston locked part)
53 Fitting convex portion 54 Fitting concave portion 55 Step portion (piston locking portion)
56 Plunger end surface (tip surface of the central wall of the piston)
61 Plunger sleeve (piston outer peripheral wall, piston sleeve)
62 Hollow pocket (recess, cylindrical space)
63 Plunger central wall (piston block)
64 Plunger end face (tip face of piston sleeve)
65 Plunger end face (Piston locked part)
66 Plunger side surface (side surface of piston sleeve)
67 Plunger end face (tip face of the central wall of the piston)
69 Outer peripheral recess (small diameter part)
71 Cylindrical part 72 Fitting part 73 Step part (piston locking part)
74 Step part 81 1st fitting part (thick part)
82 Second fitting part (thick part)
83 Cylindrical part (pocket forming part, thin part)
84 Circumferential groove (inner recess)
87 Communication path (pressure introduction groove, slit groove)
88 Communication path (through hole)
91 Fitting portion 92 Projection portion 93 Cylindrical portion 94 Axial groove

Claims (4)

A cylindrical cylinder having a cylinder hole formed therein;
A piston supported in a reciprocating manner in the cylinder,
In the high-pressure pump that pressurizes and feeds the fluid sucked into the pressurizing chamber formed at the tip side of the cylinder hole by reciprocatingly sliding the piston in the cylinder,
The cylinder has an inner surface that forms a clearance with a side surface of the piston;
The piston has a recess that opens at a tip surface facing the pressurizing chamber and communicates with the pressurizing chamber, and an outer peripheral wall that surrounds the periphery of the recess in the circumferential direction .
The concave portion is formed radially inward by the thickness of the outer peripheral wall portion from the side surface of the piston or the outer surface of the outer peripheral wall portion,
The piston has a solid central wall portion radially inward of the inner surface of the outer peripheral wall portion,
The recess is a hollow pocket formed between the inner surface of the outer peripheral wall portion and the outer surface of the central wall portion,
The hollow pocket is formed so as to surround the periphery of the central wall portion in the circumferential direction,
The piston has a body portion that reciprocates in the cylinder hole,
The outer peripheral wall portion is a sleeve having an outer diameter equivalent to that of the body portion,
The sleeve is configured as a separate part with respect to the body portion,
The first fitting portion on the pressurizing chamber side that protrudes from the both end sides in the axial direction of the sleeve to the outer surface side of the central wall portion so that the sleeve is fitted to the outer surface of the central wall portion, A second fitting portion on the opposite side of the pressurizing chamber;
An axial length of the first fitting portion is formed shorter than an axial length of the second fitting portion . The high-pressure pump according to claim 1,
The high-pressure pump according to claim 1, wherein the sleeve has a circumferential groove that forms the hollow pocket between the two first and second fitting portions . The high-pressure pump according to claim 2 ,
A pressure introducing groove that communicates the pressurizing chamber and the hollow pocket is formed at least on the sleeve side or the central wall side of the two first and second fitting portions. high-pressure pump, characterized in that there. The high-pressure pump according to claim 2 ,
A through-hole that communicates the pressurizing chamber and the hollow pocket is formed between the two first and second fitting portions .

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