Fuel pump

Patent metadata

Field	Value
Publication number	US-12480465-B2
Application number	US-202118037538-A
Country	US
Kind code	B2
Filing date	Aug 30, 2021
Priority date	Mar 9, 2021
Publication date	Nov 25, 2025
Grant date	Nov 25, 2025

Abstract

The present invention provides a fuel pump capable of discharging fuel at high pressure and suppressing sticking between a plunger and a cylinder. A high-pressure fuel supply pump includes a plunger that reciprocates, a cylinder in which a guide hole for guiding a reciprocating motion of the plunger extends in an axial direction, and a pump body including a third room (cylinder insertion hole) into which the cylinder is press-fitted, and a pressurizing chamber that communicates with the third room and has a volume increased or decreased by the reciprocating motion of the plunger. The pressure of a fixed gap generated between the cylinder and the pump body is set to be equal to or higher than pressure of a sliding gap generated between the plunger and the cylinder.

First claim

The invention claimed is:

1 . A fuel pump comprising:
a plunger that reciprocates; a cylinder in which a guide hole for guiding a reciprocating motion of the plunger extends in an axial direction of the cylinder; a pump body including a cylinder insertion hole and a pressurizing chamber that communicates with the cylinder insertion hole, the pressurizing chamber having a volume that is increased or decreased by the reciprocating motion of the plunger; a fixed gap; a sliding gap; and at least one communication passage, wherein the cylinder comprises:
an end surface extending in a radial direction of the cylinder,
a lateral surface extending in the axial direction,
an inside surface defining the guide hole, and
a press-fitted portion;
wherein the cylinder insertion hole has an axis which is coaxial with an axis of the cylinder and the cylinder insertion hole comprises:
a bottom side adjacent to the pressurizing chamber,
a top side opposite the bottom side,
a bottom surface in the bottom side that extends radially and has an interface with the end surface of the cylinder, and
a lateral surface extending axially from the bottom surface toward the top side;
wherein the press-fitted portion of the cylinder is press-fitted into the lateral surface of the cylinder insertion hole and spans an axial length from a top side end to a bottom side end, the bottom side end is an end of the axial length that is nearest to the bottom surface of the cylinder insertion hole, wherein the press-fitted portion is disposed within an annular axial section of the cylinder insertion hole, the annular axial section extending circumferentially around the axis of the cylinder and spanning from the bottom side end to the top side end of the press-fitted portion, wherein the fuel pump has only one annular axial section; wherein the fixed gap is a substantially enclosed volume formed by the lateral surface of the cylinder, the bottom surface of the cylinder insertion hole, the lateral surface of the cylinder insertion hole, and the bottom side end of the press-fitted portion; wherein the sliding gap is formed by the plunger and the inside surface of the cylinder and has a pressure distribution that decreases proportionally with axial distance from a higher pressure at a side of the sliding gap adjacent the pressurizing chamber to a lower pressure at a side of the sliding gap opposite the pressurizing chamber; wherein each said communication passage consists of a channel disposed at the interface between the bottom surface of the cylinder insertion hole and the end surface of the cylinder to directly fluidly connect the fixed gap to the pressurizing chamber whereby pressure throughout the fixed gap and the pressurizing chamber are maintained substantially uniform; wherein the at least one communication passage is the only fluid communication between the fixed gap and the pressurizing chamber; and wherein the pressure in the fixed gap is set to be equal to or higher than the higher pressure of the pressure distribution in the sliding gap by the at least one communication passage.

2 . The fuel pump according to claim 1 ,
wherein the bottom side end of the press-fitted portion has a position set based on at least one of the pressure of the pressurizing chamber during a pressurization stroke of the plunger or a sliding range of the plunger, the sliding range of the plunger being defined by the reciprocating motion of the plunger.

3 . The fuel pump according to claim 2 , wherein the position of the bottom side end is set within an axial region of the lateral surface of the cylinder that radially corresponds to a region of the sliding gap in which, during the pressurization stroke of the plunger, the pressure in the sliding gap is between one-half and one-third of the pressure in the pressurizing chamber.

4 . The fuel pump according to claim 2 ,
wherein the plunger has a top surface that enters the pressurizing chamber during the reciprocating motion of the plunger, wherein the sliding range of the plunger has a bottom dead center position as an end position in which the top surface of the plunger is farthest away from the pressurizing chamber and inside the cylinder insertion hole, and wherein the position of the bottom side end of the press-fitted portion is set within an axial region of the lateral surface of the cylinder that radially corresponds to a region of positions of the top surface of the plunger in which the top surface of the plunger has traveled a distance between one-third and one-half of the sliding range of the plunger from the bottom dead center position toward the pressurizing chamber.

5 . A fuel pump comprising:
a plunger that reciprocates; a cylinder in which a guide hole for guiding a reciprocating motion of the plunger extends in an axial direction of the cylinder; a pump body including a cylinder insertion hole and a pressurizing chamber that communicates with the cylinder insertion hole, the pressurizing chamber having a volume that is increased or decreased by the reciprocating motion of the plunger; a fixed gap; a sliding gap; and at least one communication passage; wherein the cylinder comprises:
an end surface extending in a radial direction of the cylinder,
a lateral surface extending in the axial direction,
an inside surface defining the guide hole, and
at least one press-fitted portion,
wherein the cylinder insertion hole has an axis which is coaxial with an axis of the cylinder and the cylinder insertion hole comprises:
a bottom side adjacent to the pressurizing chamber,
a top side opposite the bottom side,
a bottom surface in the bottom side that extends radially and has an interface with the end surface of the cylinder, and
a lateral surface extending axially from the bottom surface toward the top side;
wherein the at least one press-fitted portion comprises a first press-fitted portion and a second press-fitted portion; wherein the first press-fitted portion is press-fitted into the lateral surface of the cylinder insertion hole in the top side and spans an axial length from a top side end of the first press-fitted portion to a bottom side end of the first press-fitted portion, the bottom side end of the first press-fitted portion being an end of the axial length of the first press-fitted portion that is nearest to the bottom surface of the cylinder insertion hole; wherein the second press-fitted portion is press-fitted into the lateral surface of the cylinder insertion hole in the bottom side and spans an axial length from a top side end of the second press-fitted portion to a bottom side end of the second press-fitted portion, the bottom side end of the second press-fitted portion being an end of the axial length of the second press-fitted portion that is nearest to the bottom surface of the cylinder insertion hole; wherein the fixed gap is a substantially enclosed volume formed by the lateral surface of the cylinder, the lateral surface of the cylinder insertion hole, the bottom side end of the first press-fitted portion, and the top side end of the second press-fitted portion; wherein the second press-fitted portion has a lateral surface which has an interface with the lateral surface of the cylinder; wherein the sliding gap is formed by the plunger and the inside surface of the cylinder and has a pressure distribution that decreases proportionally with axial distance form a higher pressure at a side of the sliding gap adjacent the pressurizing chamber to a lower pressure at a side of the sliding gap opposite the pressurizing chamber; wherein each said communication passage consists of a first channel disposed at the interface between the bottom surface of the cylinder insertion hole and the end surface of the cylinder and a second ch

Assignees

• Hitachi Astemo Ltd

Inventors

• Usui Satoshi
• Hashida Minoru

Classifications

• F16J10/04

  Running faces; Liners · CPC title

• F02M2200/8061

  involving press-fit, i.e. interference or friction fit · CPC title

• F04B11/0091

  using a special shape of fluid pass, e.g. throttles, ducts · CPC title

• F04B9/042

  the means being cams · CPC title

• F04B53/16 Primary

  Casings; Cylinders; Cylinder liners or heads; Fluid connections · CPC title