High-pressure fuel pump with pressure limiting valve arrangement

A high-pressure fuel pump for a fuel system for an internal combustion engine, the high-pressure fuel pump comprising:

• an inlet for supplying fuel;
• an outlet for dispensing compressed fuel;
• a pump housing;
• a delivery chamber arranged in the pump housing;
• a pump piston, which is displaceable in the pump housing along a longitudinal direction and limits the delivery chamber;
• an inlet valve disposed between the inlet and the delivery chamber, the inlet valve opening towards the delivery chamber;
• an outlet valve disposed between the delivery chamber and the outlet, the outlet valve opening away from the delivery chamber;
• a high-pressure region fluidly extending between the outlet valve and the outlet;
• a low-pressure region fluidly extending between the inlet and the inlet valve;
• and
• a pressure-limiting valve configured such that, when a pressure difference between fuel in the high-pressure region and fuel in the low-pressure region exceeds an opening pressure, the pressure-limiting valve fluidically connects the high-pressure region to the low-pressure region and opens towards the low-pressure region to enable fuel to flow out of the high-pressure region into the low-pressure region,
• wherein the pump piston is formed as a stepped piston having a first piston portion that faces towards the delivery chamber and has a larger diameter, and a second piston portion that has a smaller diameter and faces away from the delivery chamber,
• wherein a high-pressure seal, in which the pump piston is displaceable, and which separates the delivery chamber from the low-pressure region is disposed between the first portion and the pump housing,
• wherein a low-pressure seal, which separates the low-pressure region from space outside the high-pressure fuel pump, is disposed between the second portion, and a seal carrier fixed to the pump housing,
• wherein a stepped chamber of the low-pressure region is disposed between the seal carrier and the pump housing,
• wherein the pressure-limiting valve fluidly connects the high-pressure region to the stepped chamber of the low-pressure region and opens toward the stepped chamber, such that fuel drains from the high-pressure region into the stepped chamber, when the pressure difference between the fuel in the high-pressure region and the fuel in the low-pressure region exceeds the opening pressure,
• wherein the outlet valve is disposed in an outlet valve bore of the pump housing the outlet valve comprising:
• a movable valve element and
• a sealing seat part disposed upstream of the valve element, the sealing seat part fixed in a pump tight manner with a sealing seat part fixing portion;
• a sealing seat, which cooperates with the valve element, formed on the sealing seat part;
• and
• a fixed counter plate disposed downstream of the valve element and fixed in a pump tight manner with a counter plate fixing portion, the fixed counter plate configured to prevent mobility of the valve element in a downstream direction, and
• wherein the pressure-limiting valve is disposed in a pressure-limiting valve bore in the pump housing, the pressure-limiting valve bore extending in the longitudinal direction and, starting from the stepped chamber, opens into the outlet valve bore.

A high-pressure fuel pump for a fuel system for an internal combustion engine, the high-pressure fuel pump comprising:

• an inlet for supplying fuel;
• an outlet for dispensing compressed fuel;
• a pump housing;
• a delivery chamber arranged in the pump housing;
• a pump piston, which is displaceable in the pump housing along a longitudinal direction and limits the delivery chamber;
• an inlet valve disposed between the inlet and the delivery chamber, the inlet valve opening towards the delivery chamber;
• an outlet valve disposed between the delivery chamber and the outlet, the outlet valve opening away from the delivery chamber;
• a high-pressure region fluidly extending between the outlet valve and the outlet;
• a low-pressure region fluidly extending between the inlet and the inlet valve;
• and
• a pressure-limiting valve configured such that, when a pressure difference between fuel in the high-pressure region and fuel in the low-pressure region exceeds an opening pressure, the pressure-limiting valve fluidically connects the high-pressure region to the low-pressure region and opens towards the low-pressure region to enable fuel to flow out of the high-pressure region into the low-pressure region,
• wherein the pump piston is formed as a stepped piston having a first piston portion that faces towards the delivery chamber and has a larger diameter, and a second piston portion that has a smaller diameter and faces away from the delivery chamber,
• wherein a high-pressure seal, in which the pump piston is displaceable, and which separates the delivery chamber from the low-pressure region is disposed between the first portion and the pump housing,
• wherein a low-pressure seal, which separates the low-pressure region from space outside the high-pressure fuel pump, is disposed between the second portion, and a seal carrier fixed to the pump housing,
• wherein a stepped chamber of the low-pressure region is disposed between the seal carrier and the pump housing,
• wherein the pressure-limiting valve fluidly connects the high-pressure region to the stepped chamber of the low-pressure region and opens toward the stepped chamber, such that fuel drains from the high-pressure region into the stepped chamber, when the pressure difference between the fuel in the high-pressure region and the fuel in the low-pressure region exceeds the opening pressure,
• wherein the outlet valve is disposed in an outlet valve bore of the pump housing,
• wherein the pressure-limiting valve is disposed in a pressure-limiting valve bore in the pump housing, and extending in the longitudinal direction, the stepped chamber opening from the pressure-limiting valve bore into a high-pressure connecting bore in the pump housing, the pressure-limiting valve disposed in the high-pressure region and oriented at an angle other than 0° to the outlet valve bore,
• wherein the pump housing comprises a pump body and a pump cover, which are connected to one another,
• wherein the pump body and the pump cover delimit a damping region belonging to the low-pressure region, and
• wherein the pressure relief valve bore is configured as a through-bore through the pump body, extending from the damping area to the step chamber, and closed on a side facing the damping area by a ball pressed into the pressure relief valve bore or a plug pressed into the pressure relief valve bore.