WO1999043941A2

WO1999043941A2 - Diesel pump fuel inlet metering using proportional control valve

Info

Publication number: WO1999043941A2
Application number: PCT/US1999/004139
Authority: WO
Inventors: Ilija Djordjevic
Original assignee: Stanadyne Automotive Corp.
Priority date: 1998-02-27
Filing date: 1999-02-25
Publication date: 1999-09-02
Also published as: WO1999043941A3

Abstract

Method and system for metering a supply of a fuel into a high pressure fuel pump (24). The method varies the pressure of the fuel supply going to the high pressure fuel pump (24). The system uses a control valve (14) disposed in the inlet line (12) in parallel with the high pressure fuel to vary the pressure of the fuel supply going to the high pressure fuel pump (24).

Description

DIESEL PUMP FUEL INLET METERING USING PROPORTIONAL CONTROL VALVE

BACKGROUND OF THE INVENTION

The present invention pertains to high pressure fuel injection pumps. The invention is particularly applicable to fuel injection pumps for supplying diesel fuel at high pressure to an accumulator of a common rail fuel injection system for a diesel engine.

It is well known that fuel from a fuel tank can be pre-metered into the pumping chamber of a piston-type fuel injection pump. This allows control of the volume of fuel delivered to the pumping chamber such that essentially all of the fuel delivered during a given charging phase is discharged at high pressure. It is common for this metering to be accomplished with a valve connected in series between the fuel tank and the fuel injection pump. The valve may be under the control of, for example, an electronic control unit which is responsive to a number of system variables which affect the desired output of the fuel injection pump. The use of an electronic control unit in combination with a control valve in series with the fuel injection pump allows a rough control over the amount of fuel sent to the fuel injection pump. In turn, this control reduces the energy wasted by pumping unneeded fuel to the high pressure accumulator and also reduces the return of heated fuel to the fuel tank.

Internal combustion engines and, especially, compression ignited internal combustion engines of the diesel type, are coming under increasingly stringent emissions and economy regulations. To meet these increasingly stringent standards, a system allowing more precise control of the fuel supplied to the high pressure fuel injection pump is needed.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved method for metering a supply of fuel into a high pressure fuel pump. It is another object of the invention to provide a method for metering a supply of a fuel into a high pressure fuel pump capable of finer control than previous methods.

It is yet another object of the present invention to provide a method and apparatus for controlling a fuel inlet line pressure and thereby metering a supply of fuel into a high pressure fuel pump, the method and apparatus providing an optimal combination of simplicity, reliability, efficiency and versatility.

These and other objects and advantages of the present invention are achieved by the use of a proportional bypass control valve fluidly connected to the fuel inlet line such that the pressure difference between the transfer pump and the pumping chamber of the fuel injection pump can be varied within a range, for example, between about zero and ten bar. When the bypass control valve is opened, the fuel inlet line is fluidly connected to a return line at essentially zero pressure. Thus, the pressure in the fuel inlet line is reduced and all of the flow from the feed pump is bypassed and returned to the fuel tank. When the control valve is fully closed, the fuel inlet line is at maximum pressure and the maximum flow from the feed pump is delivered to the pumping chamber. The operation of the control valve is determined by an electronic control unit, thereby effectuating a closed control scheme for inlet metering. Preferably, the control valve has a plurality of positions between the fully closed and fully opened position, allowing a plurality of pressures, and thereby flows, to the high pressure fuel injection pump.

Further, the high pressure fuel injection pump may comprise a check valve fluidly connecting the inlet delivery line to the pumping chamber. The check valve has a closed position preventing flow therethrough and an open position allowing flow therethrough. The check valve is biased toward the closed position such that a preload closure pressure must be overcome to actuate the check valve from the closed position to the open position. As the bypass control valve moves through intermediate positions between fully opened and fully closed, the pressure in the fuel inlet line increases. As long as the fuel inlet line pressure is below the preload closure pressure, fuel continues to be routed to the fuel tank. As the bypass control valve transitions through an intermediate position whereby the fuel inlet line pressure rises above the preload closure pressure, the check valve moves toward an open position and fuel is introduced into the fuel pump pumping chamber. When the bypass control valve is fully closed, the fuel inlet line pressure is at its maximum pressure and all of the fuel is directed through the check valve to the pumping chamber. The use of a control valve in parallel with the high pressure fuel pump, especially in combination with a check valve, allows a much more precise control of fuel inlet pressure and, thereby, fuel inlet flow to the pumping chamber. The precise control over fuel inlet pressure and flow increases fuel economy and reduces emissions in compression ignition engines so equipped. In addition, these advantages are achieved without significant increases in either fuel system complexity or cost.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will be evident to one of ordinary skill in the art from the following detailed description made with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a fuel injection system with a remote supply pump incorporating the parallel control valve of the present invention; Figure 2 is a schematic diagram of a fuel injection system incorporating a fuel supply pump driven off of the high pressure fuel pump and including the parallel control valve of the present invention; and Figure 3 is a schematic representation of a fuel injection system similar to that of Figure 2 incorporating two control valves in series with each other and both in parallel with the high pressure fuel pump inlet. DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in Figure 1, in one embodiment of the invention, a fuel source line 2 has one end immersed in the fuel tank 4 and the other end is connected to a supply pump 6. The pump may be, for example, a gear pump which is driven off the vehicle engine. Alternatively, the fuel pump may be powered independently of the vehicle engine. The supply pump discharges the fuel at a pressure, for example, ten bar. Preferably, the fuel is discharged from the supply pump 6 through a fuel filter 8 and then a flow restrictor 10. The flow restrictor assures that the maximum quantity of fuel supplied to the pumping chamber is not excessive in view of the relatively high pumping volume of a typical gear pump. A fuel inlet line 12 has a first end fluidly connected to the flow restrictor 10 and an opposing second end. The second end is connected in parallel to the control valve 14 and high pressure fuel pump inlet 16.

The control valve 14 includes an outlet 22 fluidly connected to a return line 18 which may return to, for example, the fuel tank. When the control valve is in the open position, the control valve inlet 20 and outlet 22 are fluidly connected and when the control valve is in the closed position, the inlet and outlet are completely separated. If the control valve is of the proportional type, positions between the open and closed positions may be achieved. The high pressure fuel pump, generally 24 and shown within the dashed lines, may be of any type. As an example, the fuel pump described is of the internally actuated-externally pumping type although different fuel pump types may also be used. The example fuel pump uses a piston 26 reciprocating within a pumping chamber 28 which is connected to both an inlet 30 and outlet 32 check valve. The inlet check valve 30 is fluidly disposed between the high pressure fuel pump inlet 16 and the pumping bore 29. The pumping bore, in cooperation with the plunger 26 comprises a pumping chamber 29. Similarly, the outlet check valve 32 is fluidly disposed between the pumping chamber 28 and a high pressure accumulator 34. The inlet check valve typically has a preload closure pressure of about one bar. This preload closure pressure must be overcome by pressure in the fuel inlet line in order for fuel to be delivered into the pumping chamber 28. Therefore, if the control valve 14 is fully opened, exposing the fuel inlet line 12 to the essentially zero pressure in the return line 18, the pressure in the fuel inlet line will be reduced below the preload closure pressure of the inlet check valve 30. In this condition, no fuel will be delivered into the pumping chamber 28. As the control valve 14 closes, pressure within the fuel inlet line 12 will increase. When the control valve closes to a position sufficient to raise the fuel inlet line pressure above the preload closure pressure, fuel will begin to be delivered into the pumping chamber 28. As the control valve 14 continues closing to the fully closed position, the fuel inlet line pressure will increase up to the maximum pressure created by the supply pump. Therefore, the quantity of fuel can be metered into the pumping chamber of a high pressure fuel injection pump by controlling the fuel inlet line pressure with a control valve.

The balance of the schematic shown in Figure 1 is somewhat conventional. Upon rotation of the rotating cam 36, the roller 38 and shoe 40 drive the plunger 26 toward the pumping chamber 28, increasing the pressure therein, such that the pressurized fuel closes the inlet check valve 30 and opens the outlet check valve 32 for delivery to the high pressure accumulator 34. Any fuel which leaks along the plunger 26, or is otherwise diverted from the pumping chamber 28, is returned via a return line 42 to the fuel tank. The high pressure accumulator 34, injectors 44 and control associated therewith, form no direct part of the present invention. However, one of ordinary skill in the art would know how to define a control program for the electronic control unit (ECU) 46, by which characteristics of the accumulator 34, injectors 44 and other inputs are taken into account in determining the proportionality behavior to be followed by the metering control valve 14.

Further, while the present figure shows an internally actuated, externally pumping, high pressure fuel supply pump, the present invention is also applicable to other high pressure fuel injection pump designs. For example, a person skilled in the art could apply the present invention to a high pressure fuel injection pump of the externally driven, internally pumping variety.

Figure 2 schematically illustrates a different embodiment of the invention. In this embodiment, the supply pump 48 is not a gear pump, but could be a smaller volume piston-type pump which is driven from the same shaft which drives the high pressure fuel injection pump. In this embodiment, a flow restrictor is not needed in the inlet line 12, because the inlet volumes are compatible with the needs of the pumping chamber. In other respects, the invention is similar to that described with respect to Figure 1.

In yet another embodiment, a plurality of control valves can be arranged to simultaneously influence the pressure in the inlet line 12. This affords a greater degree of control than is available with a single control valve. As shown in Figure 3, two control valves 14A, 14B are arranged in series to provide an increased range of control. This also accommodates a higher volume of fuel delivery from high capacity supply pumps. Preferably, the valves 14A, 14B are incorporated within the high pressure fuel injection pump 24, which in Figure 3 is denoted by the dash line. While not shown, the control valves 14A, 14B may both be arranged in parallel with the fuel inlet line 12. Thus, in its broadest aspect, the invention can be viewed as a method and apparatus for metering fuel flowing in a fuel inlet line between a supply pump and a high pressure pumping chamber. The metering is accomplished as a result of the control of pressure within the fuel inlet line by a valve which is fluidly connected to, but not in line with, the fuel inlet line. While various embodiments of the foregoing invention have been set forth for purposes of illustration, the foregoing description should not be deemed a limitation of the invention herein. Accordingly, various modifications, adaptations and alternatives may occur to one skilled in the art without departing from the spirit and the scope of the present invention.

Claims

WHAT IS CLAIMED:

1. A method for metering a supply of a fuel into a high pressure fuel pump for a fuel injection system, comprising: providing a supply of fuel at a first pressure into a fuel inlet line; fluidly connecting said fuel inlet line in parallel to a control valve and a high pressure fuel pump; actuating said control valve to a closed position or an open position; wherein when said control valve is actuated to said closed position, said fuel is supplied to said high pressure fuel pump at said first pressure, and when said valve is actuated to said open position, said fuel is supplied to said high pressure fuel pump at a second pressure less than said first pressure.

2. The method of claim 1 , wherein: said control valve includes an inlet and an outlet fluidly connected to a return, wherein in the open position said valve outlet and inlet are fluidly connected and in the closed position said valve outlet and inlet are fluidly separated; said high pressure fuel pump includes a pumping chamber fluidly connected to both a high pressure fuel distribution system and an inlet; said step of connecting further comprises connecting said fuel inlet line in parallel to said control valve inlet and said fuel pump inlet.

3. The method of claim 2, wherein: said control valve further includes a plurality of positions intermediate said open and closed positions; and the step of actuating said control valve further includes actuating said valve to a said position; wherein when said control valve is actuated to a said intermediate position, said fuel is supplied to said high pressure fuel pump inlet at an intermediate pressure between said first and second pressures.

4. The method of claim 3, further comprising: providing a check valve fluidly disposed between said high pressure fuel pump inlet and said pumping chamber, said check valve having a closed position preventing flow therethrough, an open position allowing flow therethrough and a preload closure pressure, wherein when said intermediate pressure is below said preload closure pressure the check valve remains in the closed position and when said intermediate pressure is at or above the preload closure pressure the check valve actuates toward the open position; and actuating said control valve to a position wherein said intermediate pressure is below said preload closure pressure when said fuel is not needed by said high pressure fuel pump and actuating said control valve to a position wherein said intermediate pressure is at or above said preload closure pressure when said fuel is needed by said high pressure fuel pump.

5. The method of claim 3, further comprising: providing a control unit electrically connected to a sensor and to said control valve; monitoring said sensor with said control unit; and actuating said control valve to a position with said control unit.

6. The method of claim 5, further comprising: providing at least a second control valve fluidly connected in series between the first control valve and the return; providing a control unit connected to the sensor and to each said control valve; and actuating each said control valve to a position with said control unit.

7. The method of claim 5, further comprising: providing at least a second control valve fluidly connected to said fuel inlet line in parallel with said first control valve and said high pressure fuel pump inlet; providing a control unit connected to the sensor and to each said control valve; and actuating each said control valve to a position with said control unit.

8. A high pressure fuel pump inlet system, comprising: a control valve with an outlet and an inlet, said control valve having an open position wherein said outlet and inlet are fluidly connected and a closed position fluidly separating said outlet and said inlet; a high pressure fuel pump with a pumping chamber fluidly connected to both a fuel pump outlet and a fuel pump inlet; and a supply of a fuel at a first pressure within a fuel inlet line, said fuel inlet line fluidly connected in parallel to said control valve inlet and said fuel pump inlet; wherein when said control valve is in said closed position, said fuel is supplied to said fuel pump inlet at said first pressure, and when said valve is in said open position, said fuel is supplied to said fuel pump inlet at a second pressure less than said first pressure.

9. The high pressure fuel pump inlet system of claim 8, further comprising a control valve with a plurality of positions intermediate said open and closed positions; wherein when said control valve is actuated to said intermediate position, said fuel is supplied to said fuel pump inlet at an intermediate pressure between said first and second pressures.

10. The high pressure fuel pump inlet system of claim 9, further comprising a check valve fluidly connecting said fuel pump inlet to said pumping chamber, said check valve having a closed position preventing flow therethrough, an open position allowing flow therethrough and a preload closure pressure intermediate said first pressure and said second pressure; wherein when said intermediate pressure is below the preload closure pressure the check valve remains in the closed position and when said intermediate pressure is at or above the preload closure pressure the check valve actuates toward the open position.

11. The high pressure fuel pump inlet system of claim 9, further comprising: at least one sensor; and a control unit connected to said sensor and said control valve; wherein said control unit actuates said control valve to a said position.

12. The high pressure fuel pump inlet system of claim 11, wherein the control unit is electrically connected to the sensor and the control valve.

13. The high pressure fuel pump inlet system of claim 12, further comprising: at least a second control valve fluidly connected in series between the first control valve and the return; and a control unit connected to the sensor and to each said control valve; wherein said control unit actuates each said control valve to a said position.

14. The high pressure fuel pump inlet system of claim 12, further comprising: at least a second control valve fluidly connected to said fuel inlet line in parallel with said first control valve and said fuel pump inlet; and a control unit connected to the sensor and to each said control valve; wherein said control unit actuates each said control valve to a position.