FIELD OF INVENTION:

The invention relates to the control mechanism for a port controlled high pressure pump.

BACKGROUND OF THE INVENTION:

An injector having a dual function of pressurizing the fuel and injecting the fuel into a cylinder of an internai combustion engine is already known. US patent 6336443 discloses one such injector. The patent discloses an injection pump in which the supply onset can be set freely for two différent operating modes of the engine. The supply onset is attained in the cylinder by use of a second control bore, which cooperates with a plunge eut in the cylinder and with a piston stop groove that extends longitudinally along the pump piston from the upper control edge. The piston in the injector is rotated to control the amount of fuel injected. The piston is rotated using a mechanical control rod.

ADVANTAGES OF THE INVENTION:

By using a motor to control the alignment of the piston in the high pressure pump, the high pressure pump is controlled more accurately. The mechanical coupling is eliminated thereby reducing the wear and tear of the pump.

BRIEF DESCRIPTION OF THE DRAWINGS:

Figure 1: Shows the schematic of the high pressure pump according to the invention.

Figure 2 and Figure 3: Shows sections of the high pressure pump

DESCRIPTION OF THE INVENTION:

Shown in fig. 1 is the schematic of a high pressure pump 100. The high pressure pump 100 is referred as pump in the rest of the document. The pump 100 comprises a housing 102, the piston 103 moving in a bore 104. An inlet 106 supplies fuel to the pump 100 and the pump* 100 delivers the pressurized fuel through an outlet 108. The fuel is pressurized in the pump chamber 110. A Spill port 112 carries the excess fuel back to the reservoir which is not shown. The piston 100 is moved in the pumping direction by a cam which is shown in fig. 2. The piston 100 is retracted by a spring 113 which is shown in fig. 2. The pump housing comprises a motor 114. The motor 114 is shown as comprising stator and rotor. An Electronic control unit (ECU) 116 controls the motor 114. The ECU 116 receives engine operating conditions 118 and computes the amount of fuel to be delivered by the pump 100.

Shown in fig. 2 and fig. 3 are cross sections of the pump 100. The same reference numbers are used to indicate the same parts as in fig. 1. The piston 103 has a spill passage 214 and a helical grove 216. The spill passage 214 opens to the pump chamber 110. When the spill passage 214, the helical grove 216 and the spill port 112 are aligned communicatively, the fuel flows from the pump chamber 110 to the spill port 112.

The stroke of the piston 103 is not variable. Also the fuel supplied through the inlet 106 is of constant pressure. Hence the fuel entering into the pump chamber 110 for a given pumping cycle is of constant volume, the pumping cycle comprising a suction stroke and a pumping stroke. The amount of fuel delivered by the pump 100 is regulated by the effective stroke of the piston 103. The effective stroke of the piston is the length of the movement of the piston 103 before the spill passage 214 gets connected to the spill port 112.

One method to regulate the amount of fuel delivered through the outlet 108 is by varying the effective stroke of the piston 103, which is achieved by rotating the piston 103. By rotating the piston 103, the spill passage 106 is connected to the spill port 112 through the helical grove 216 either early or late in the pumping stroke of the piston 103. The moment the spill passage 214 is connected to the spill port 112, a part of the fuel starts flowing from the pump chamber 110 through the spill port 112, thereby reducing the pressure in the pumping chamber 110.

If the spill passage 214 is connected to the spill port 112 early in the pumping stroke of the piston 103, the pressure in the pumping chamber 110 drops early in the pumping stroke, thereby delivering lesser fuel through the outlet 108.

If the spill passage 214 is connected to the spill port 112 late in the pumping stroke of the piston 103, high pressurization of the fuel occurs for more time in the pumping chamber 110 thereby delivering more fuel through the outlet 108.

So by connecting the spill passage 214 to the spill port 112 either early or late in the pumping stroke, the amount of the fuel delivered through the outlet 108 is controlled.
The effective stroke of the pump is determined by the orientation of the piston 103 in radial direction. At one extreme position of the piston 103 in radial direction, the spill passage 214 is continuously in connection with the spill port 112 for the entire duration of the pumping stroke of the piston 103. Under this position, the fuel is not delivered through the outlet 108 because the fuel continuously escapes through the spill port 112 and pressurization of the fuel is not possible in the pump chamber 110.

This position is used for no load condition of the engine.

At the other extreme position of the piston 103 in the radial direction, the spill passage 214 is connected to the spill port 112 very late in the pumping stroke so that the fuel is pressurized for the maximum duration of the pumping stroke thereby delivering maximum fuel through the outlet 108. This position is used for the full load condition of the engine.

Any other position of the piston 103 between the no load condition and the full load condition is used to deliver différent amount of fuel.

The working of the pump is well known and not explained in this document.

The amount of fuel injected by the pump 100 is determined by the length of the effective stroke of the piston 103. The length of the effective stroke of the piston is controlled by rotating the piston 103 in appropriate direction.

The invention proposes a motor to rotate the piston in the radial direction. The piston is an extended shaft of the motor.

The ECU 116 controls the rotation of the motor 114. The ECU receives engine operating conditions 118 which comprise engine speed, vehicle speed, and accelerator pedal position. This list is provided only for reference and do not form the complété list. The ECU computes the amount of fuel to be delivered by the pump 100. The amount of rotation of the motor and the direction of the rotation of the motor is computed in dependence of the amount of fuel to be delivered by the pump 100. The ECU rotâtes the motor by required amount and in required direction. The rotation of the motor causes the piston to rotate. The rotation of the piston varies the effective stroke of the piston thereby varying the amount of pressurized fuel delivered by the pump 100 through the outlet 108. The ECU which is referred here, can also be an engine control unit which is already present in the vehicle or it may be a dedicated ECU built into the housing of the pump.

In this document the spill port, the spill passage, the helical grove etc. are said to be connected to each other if they facilitate flow of fluid from one to another. This is true with other elements where the fluid can flow.

By providing a motor integrated into the pump 100, the rotation of the piston is accurately controlled. The ECU controls the rotation of the motor depending upon the engine operating conditions.

Unlike in the prior arts where the similar pump was controlled by a control rod rotating the piston causing wear and tear of the mechanical couplings, the proposed invention has the advantage that the mechanical couplings are eliminated. The ECU computes the amount of fuel to be delivered and accurately controls the motor.

WE CLAIM:

1. A high pressure fuel pump (100) for delivering fuel under high pressure for an internai combustion engine, the high pressure fuel pump comprising a piston (103), the piston (103) reciprocating in a cylinder bore (104), a pump chamber (110) to pressurize the fuel, an inlet (106) to receive fuel from a fuel reservoir, an outlet (108) to deliver fuel under high pressure, a spill port (112) to return the excess fuel to the reservoir, a spill passage in the piston; the said spill passage opening to the pump chamber; a helical grove on the surface of the piston; the pump chamber, the spill passage and the helical grove communicatively alignable to the spill port; the piston (103) adapted to rotate with respect to its axis, the said piston (103) coupled to a shaft of a motor (114).

2. A high pressure fuel pump according to claim 1 wherein the motor (114) is controlled by an electronic control unit - ECU (116).

3. A high pressure fuel pump according to claim 1 wherein rotation of the motor (114) causes the piston (103) to rotate with respect to the axis of the piston (103).

4. A high pressure fuel pump according to claim 1 wherein effective stroke of the piston is the length of the piston movement during the pumping stroke before the spill passage, the helical grove and the spill port are communicatively aligned to transfer the fuel from pump chamber to the spill port.

5. A high pressure fuel pump according to claim 1 wherein rotation of the motor in a first direction increases the effective stroke of the high pressure fuel pump

6. A high pressure fuel pump according to claim 1 wherein rotation of the motor in a second direction decreases the effective stroke of the high pressure fuel pump

7. An electronic control unit to control the motor of a high pressure fuel pump in order to control the effective stroke of a piston of the high pressure fuel pump thereby controlling the amount of fuel delivered by the high pressure fuel pump

8. An electronic control unit according to claim 7 rotâtes the motor in a first direction to increase the effective stroke of the piston of the high pressure fuel pump.

9. An electronic control unit according to claim 7 rotâtes the motor in a second direction to decrease the effective stroke of the high pressure fuel pump.

10. An electronic control unit according to claim 7 wherein the ECU détermines the current position of the motor shaft.

11. An electronic control unit according to claim 7 adapted to read engine operating conditions, the said operating conditions being at least one of engine speed, engine load, engine temperature, ambient temperature, ambient pressure, amount of air in the intake.

12. An electronic control unit according to claim 7 and 11 adapted to determine the required position of the motor shaft depending upon the engine operating conditions.