US 2004/0168674 A1 · Hybrid demand control for hydraulic pump

Abstract

The invention is directed to the combination of fuel rail pressure control at lower speed using high pressure regulation plus fuel rail pressure control at higher speed using any of a variety of forms of inlet metering. The partial filing control at high speed can in one embodiment include pre-metering the quantity of feed fuel delivered to each pumping chamber, for example by modulating the feed pressure at the pumping chamber inlet. Another embodiment includes passing the feed fuel from the inlet passage through a fixed, calibrated orifice sized to pass sufficient feed fuel to fill the pumping chambers in the charging phase during operation of the engine in the low speed range, while in the high speed range the flow resistance of the orifice prevents the pumping chamber from filling in the charging phase, thereby monotonically decreasing the quantity of high pressure fuel delivered to the discharge passage in the discharge phase per engine revolution, with increasing speed above the transition speed.

Claims21

Dependent claims

In a high pressure common rail fuel supply system for delivering fuel to an internal combustion engine having a plurality of combustion cylinders and a respective plurality of fuel injectors fluidly connected to the common rail for injecting fuel into the cylinders at the pressure of the common rail for operating the engine at speeds ranging from cranking speed to a maximum speed, the system including a high pressure fuel supply pump with radial pistons reciprocating in pumping chambers and driven by the engine at a pump speed proportional to the engine speed, a method of pumping fuel to the common rail at a rail target pressure, comprising:

continuously delivering feed fuel at a low pressure, to an inlet port of the pump;
during operation of the engine in a low speed range below a transition speed, (a) (1) filling each pumping chamber during a charging phase, from inlet passages in fluid communication with the inlet port, (2) pressurizing the charged fuel in the pumping chambers by displacing the respective pistons during a discharge phase, and (3) delivering the discharged fuel to a discharge passageway in fluid communication with the common rail, and (b) maintaining the rail target pressure by continually diverting at least some of the pressurized fuel in at least one of the discharge passage or the common rail, to a low pressure sink;
during operation of the engine in a high-speed range above the transition speed, (c) (1) partially filling each pumping chamber during the charging phase, from said inlet passages, (2) pressurizing the charged fuel in the pumping chambers by displacing the respective pistons during the discharge phase, and (3) delivering the discharged fuel to the discharge passageway, and (d) maintaining the rail target pressure by continually diverting at least some of the pressurized fuel in at least one of the discharge passage or the common rail, to the low pressure sink.

A high pressure fuel supply pump for receiving fuel from a fuel tank at low feed pressure discharging high pressure fuel to a common rail for delivery to an internal combustion engine having a plurality of combustion cylinders and a respective plurality of fuel injectors fluidly connected to the common rail for injecting fuel into the cylinders at the pressure of the common rail for operating the engine at speeds ranging from cranking speed to a maximum speed, said pump comprising:

a housing, a pump shaft situated within the housing, a plurality of radial pistons mounted for reciprocation in respective pumping chambers and for actuation by the engine at a pump speed proportional to the engine speed;
an inlet port for receiving feed fuel at said feed pressure, and inlet passages fluidly connected in parallel between the inlet port and the pumping chambers for delivering feed fuel to the pumping chambers during a charging phase of operation;
a discharge port for discharging high pressure fuel to the common rail, and discharge passageways from the pumping chambers to the discharge port for delivering high pressure fuel from the pumping chambers during a pumping phase of operation;
a pressure regulator for fluidly connecting the discharge passageways to the inlet passageways to divert at least some high pressure discharged fuel to low pressure feed fuel when the discharge pressure exceeds a limit value and for maintaining full discharge flow from the discharge passageways to the outlet port when the discharge pressure is below said limit value;
and
means situated between the inlet port and the parallel fluid passages, for restricting the flow of feed fuel through the inlet passages to the pumping chambers when the pump speed exceeds a predetermined threshold value.

3 more elements

Dependencies are inferred from the claim text.

Hybrid demand control for hydraulic pump

Life of this patent

Hybrid demand control for hydraulic pump

Life of this patent

Abstract

Claims21