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US 6,305,356 B1Granted
Common rail system
AssigneeRobert Bosch GmbH
InventorsErhard Faix, Gerd Loesch
Life of this patent
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AssigneeRobert Bosch GmbH
InventorsErhard Faix, Gerd Loesch
Estimating the term…
A common rail system having a regulated prefeed pump, which pumps a fuel flow from a fuel tank to a high-pressure pump. The fuel flow is split with the aid of a valve assembly into a lubricant flow and a high-pressure feed flow that is pumped into a high-pressure reservoir, and acted upon by high pressure. The prefeed pump has a substantially linear characteristic feed curve with a certain slope. To improve the regulating performance, the valve assembly for the lubricant flow includes a valve whose characteristic feed curve initially rises in a first portion (I) with the rpm of the prefeed pump with the same slope as the characteristic feed curve of the prefeed pump. Then in a second portion (II) rises substantially linearly, with a lesser slope than the characteristic feed curve of the prefeed pump, and in a third portion (III) finally drops again.
In a common rail system having a regulated prefeed pump, said pump pumps a fuel flow from a fuel tank to a high-pressure pump, wherein the fuel flow is split into a lubricant flow and a high-pressure feed flow that is pumped into a high-pressure reservoir and acted upon by high pressure, the prefeed pump has a substantially linear characteristic feed curve (1) with a certain slope, and the lubricant flow is controlled by a lubricant flow valve assembly, the improvement comprising:
A flow regulating valve for use in a common rail fuel system to maintain a substantially constant flow of fuel to be used as a lubricant, said regulating valve comprising an elongated valve body (4) having a bore (5) of the valve body with a constant diameter throughout its length, the bore having inserted therein a valve piston (6) which is displaceable along the bore (5) of the valve body, and a tang (7) fixedly mounted in the bore, such that one end of the tang (7) is flush with one end of the valve body (4), the tang (7) being divided into two sections by a shoulder (8), one of said sections having a diameter which is press fit into the bore, the other section having a smaller diameter so as to receive a spring (10) positioned within the bore (5) of the valve body between the shoulder (8) and the valve piston (6), which spring (10) biases the valve piston (6) away from the tang (7), the tang having a longitudinal bore (12), and the smaller diameter section having a transverse bore (11) which communicates between the longitudinal bore and the outside of the smaller diameter section of the tang (7), the smaller diameter section also having an end with a valve seat (15) and a restricted region (13), wherein the restricted region (13) of the longitudinal bore (12) of the tang has a smaller flow path compared to the rest of the longitudinal bore (12) of the tang, and the valve piston (6) has a longitudinal bore, such that as fuel is pumped into the other end of the bore (5) of the valve body, fuel can flow through the bore (5) of the valve body, the longitudinal bore of the valve piston (6), the restricted region (13) and the longitudinal bore (12) of the tang (7), and an additional portion of fuel will flow through the bore (5) of the valve body, the longitudinal bore of the valve piston (6), around the outside of the smaller diameter section of the tang (7), through the transverse bore (11) and the longitudinal bore (12) of the tang (7), such that if the fuel flow increases to a sufficient amount, the increased flow of the fuel moves the valve piston (6) against the pressure of the spring (10) into engagement with the valve seat (15) so as to block fuel from flowing past the outside of the smaller diameter section of the tang (7) and all of the fuel must flow through the restricted region (13).
A method of supplying a high pressure pump with a supply of fuel from a prefeed pump, said supply fuel being at least partially used in the high pressure pump as a lubricating medium, the method comprising:
In a common rail fuel system, a method of supplying a high pressure pump with a supply of fuel from a prefeed pump, said supply fuel being used in the high pressure pump as a lubricating medium, the method comprising:
Dependencies are inferred from the claim text.