A pump body of a high-pressure pump includes a pressure chamber formed in a deep portion of a cylinder. A plunger reciprocates within the cylinder to vary a volume of the pressure chamber. A discharge path and a supply path are formed in the pump body and extend in a radial direction of the cylinder from the pressure chamber. A pin provided at an end of the plunger in the pressure chamber protrudes in one radial direction of the plunger to the outside of an inner circumference of the cylinder. In this case, the pin is engaged with a step portion between the cylinder and the pressure chamber in a state before attachment of the high-pressure pump to an internal combustion engine. Accordingly, separation of the plunger from the cylinder is avoidable.

A direct-injection, supercharged internal combustion engine having at least one cylinder, in which each cylinder is equipped with a direct injection apparatus, a fuel supply system comprising a high-pressure side and a low-pressure side, and a high-pressure piston pump comprising a piston displaceable in translational fashion between a bottom dead center and a top dead center of a pressure chamber of variable volume. The displaceable piston jointly delimits the pressure chamber with variable volume in such a way that a displacement of the piston causes a change in the volume of the pressure chamber via actuation of least one movable actuation element.

A high-pressure fuel pump includes a pump housing which defines a pumping chamber, a fuel inlet which allows low-pressure fuel into the pumping chamber, a fuel outlet which allows high-pressure fuel out of the pumping chamber, and a plunger bore which extends along an axis and opens into the pumping chamber. The high-pressure fuel pump also includes a pumping plunger which reciprocates within the plunger bore along the axis such that reciprocation of the pumping plunger within the plunger bore increase and decreases a volume of the pumping chamber. The pumping plunger includes a sealing ring groove which is concentric with the plunger bore, the sealing ring groove including a sealing ring therein which engages the plunger bore in an interference fit. A diametric clearance greater than 12 microns is provided between the pumping plunger and the plunger bore.

A high-pressure fuel pump includes a pump housing, a pump piston accommodated in a receiving opening of the pump housing, a high-pressure seal which surrounds the pump piston in a sealing manner and which seals off a high-pressure region from a low-pressure region, and a guide device which comprises at least two guide portions that are axially spaced apart from one another and guide the pump piston with a sliding fit. The at least two guide portions are arranged in the receiving opening of the pump housing. A first guide portion is arranged, as seen in an axial direction, on a side of the high-pressure seal facing toward the delivery space. And a second guide portion is arranged, as seen in the axial direction, on a side of the high-pressure seal facing away from the delivery space.

An injector apparatus (310) for injecting fluid under pressure into an associated chamber (332) is provided. The injector apparatus (310) includes a first piston (314) defining a first working area facing an associated chamber (332), a high pressure piston (318) defining a high pressure working area facing a high pressure chamber (319), and a control piston (317) defining a control piston working area facing a control chamber (315). The first piston (314) is moveable with a body of the injector apparatus (310) to compress fluid in the high pressure chamber (319) using the high pressure piston (318), while movement of the first piston (314) is selectively controllable by controlling the fluid in the control chamber (315). The first working area is larger than the control piston working area and the control piston (317) working area is larger than the high pressure working area.

A plunger is provided for reciprocating inside the barrel of a fuel pump. The plunger has a proximal end and a distal end. The proximal end of the plunger includes a cavity that defines a depressed volume within the plunger. A volume filler is disposed in the cavity, where the volume filler is constrained in the cavity by a retaining element.

A plunger is provided for reciprocating inside the barrel of a fuel pump. The plunger has a proximal end and a distal end. The proximal end of the plunger includes a cavity that defines a depressed volume within the plunger. A volume filler is disposed in the cavity, where the volume filler is constrained in the cavity by a retaining element.

A fuel pump includes a pump housing with a pumping chamber an inlet valve bore. An inlet valve selectively provides and prevents fluid communication between an inlet of the fuel pump and the pumping chamber. The inlet valve includes an inner housing received within the inlet valve bore such that an outer periphery of the inner housing is sealed to an inner periphery of the inlet valve bore. An outer housing circumferentially surrounds the inner housing. An annular chamber is defined radially between the inner housing and the outer housing and axially between the outer housing and the pump housing. A sealing ring is located within the annular chamber such that the sealing ring is compressed axially against the pump housing and the outer housing.

A fuel pump includes a fuel pump housing with a pumping chamber and an inlet valve bore which extends along an inlet valve bore axis. The inlet valve bore is stepped such that the inlet valve bore includes a shoulder which is traverse to the inlet valve bore axis. A pumping plunger reciprocates within a plunger bore along a plunger bore axis such that an intake stroke of the pumping plunger increases volume of the pumping chamber and a compression stroke of the pumping plunger decreases volume of the pumping chamber. An inlet valve assembly includes a valve seat with a valve seat flow passage extending therethrough, the valve seat abuts the shoulder and is urged toward the shoulder by pressure within the pumping chamber during the compression stroke. The inlet valve assembly also includes a valve member which is moveable between an unseated position and a seated position.

A high-pressure fuel pipe is a pipe disposed between an injector and a high-pressure fuel pump, the high-pressure fuel pump is provided on a downstream side of a low-pressure fuel pump, an engine is a single cylinder or a two-cylinder, the high-pressure fuel pump is a plunger type that performs pressurization once or twice per rotation in synchronization with a camshaft of the engine, and a volume of the high-pressure fuel pipe is k×Q/ΔP/1000×n or less, where k is a volume modulus of fuel, Q is a maximum discharge amount of the fuel in one reciprocation of the high-pressure fuel pump, ΔP is a difference between a target fuel pressure boosted by the high-pressure fuel pump and a feed fuel pressure boosted by the low-pressure fuel pump, and n is the number of times of boosting in one rotation of the high-pressure fuel pump.