The power output of an internal combustion engine may be controlled in a number of ways. One method of controlling the power output of internal combustion engines is controlling the amount of fuel supplied to each engine combustion chamber. In internal combustion engines which utilize fuel injection pumps for supplying, fuel to the engine combustion chambers, the engine fuel supply may be controlled either by using a mechanical valve to restrict fuel entering the fuel injection pump, and thereby fuel delivered to the engine, or by diverting some of the high pressure flow discharged from the fuel injection pump outlet.

More precise control of fuel supplied to an internal combustion engine by a fuel injection pump has become important due to the demand for improved fuel economy and increasingly stringent legislation controlling emissions emanating from internal combustion engines.

While known mechanical valves provide sufficient control of fuel entering a fuel pump inlet for some applications, they are limited in their ability to address these increasingly stringent additional demands.

Conventional mechanical valves are also incapable of interaction with sensors to permit electronic fuel curve shaping and are not adaptable to "fly by wire"control. Engine manufacturers are forced to convert to full electronic fuel injection pumps at substantially higher cost to obtain these benefits. Typically, full electronic pump control devices control

fuel delivery via the fuel injection pump high pressure output. As a result of their use with the high pressure output, these electronic pump control devices require high force and fast response time which results in devices that are typically bulky and expensive. Further, these devices also have substantial power requirements due to of the high force and fast response time demands.

Summary of the Invention It is an object of the invention to provide an improved method for metering the 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 fuel into a high pressure fuel pump capable of finer control than traditional mechanical metering valves.

It is yet another object of the present invention to provide a method and apparatus for electronically controlling fuel inlet metering to a mechanical fuel injection pump, the method and apparatus providing an optimal combination of simplicity, reliability, efficiency and versatility.

Still another object of the present invention is to provide a method and apparatus for fuel inlet metering of a mechanical fuel injection pump which allows for closed loop control and electronic fuel curve shaping, while also providing redundant systems for engine ; shutdown and limp home capabilities.

These and other objects and advantages of the present invention are achieved by the use of a proportional solenoid control valve with an inlet fluidly connected to a fuel supply and an outlet fluidly connected to the fuel injection pump inlet. In the closed condition, the solenoid valve inlet and outlet are fluidly separated, thereby preventing fuel flow into the fuel injection pump inlet and as a consequence, into the engine

combustion chamber. In the open condition, the solenoid valve inlet and outlet are fluidly connected, thereby allowing fuel flow at a maximum predefined flow rate through the solenoid valve, into the fuel injection pump inlet and thereby into the engine combustion chamber. At any of the plurality of solenoid valve positions between closed and open, fuel flow is controlled into the fuel injection pump inlet.

The operation of the solenoid valve is controlled by an electronic control unit, thereby allowing a closed loop control scheme wherein the controller is adapted to function in conjunction with feedback from a sensor or sensors. In addition, the electronic control unit in conjunction with the proportional solenoid valve can control the fuel flowing to the fuel pump inlet, and thereby the engine, over the range of engine and vehicle operating conditions thereby allowing"fuel curve shaping".

Further, electronic control of the proportional solenoid valve allows the elimination of mechanical control connections to the high pressure fuel pump, ailowing"fly by wire"operation with a modified mechanical fuel pump. Since the fuel supply pressure is typically less than 130 psi, a proportional solenoid valve can accomplish inlet metering with a small and simple solenoid valve assembly. Further, use of the inventive proportional solenoid inlet metering method has no effect on other fuel injection sub-systems, such as cam advance mechanisms in the fuel pump.

The proportional solenoid valve may also be used in conjunction with a conventional mechanical fuel pump metering valve. The fuel supply, mechanical metering valve, solenoid metering valve and fuel injection pump inlet are all fluidly connected in series. The solenoid valve and mechanical valve are disposed between the fuel supply and fuel pump inlet, and may be in any order. This embodiment allows the finer control achievable with a proportional solenoid valve yielding

increased fuel economy and lowered emissions, while retaining a redundant mechanical valve. Since combustion ignited internal combustion engines can only be shut down by discontinuing fuel or air supply to the engine, the mechanical control valve allows a backup mechanism for controlling fuel supply to the engine in the unlikely event the solenoid valve fails. The provision of a redundant mechanical valve also allows for a"limp home"capability.

In a further embodiment, the proportional solenoid valve and a flow branch are placed in parallel between a mechanical metering valve and the fuel pump inlet. The use of a flow branch allows fuel pump inlet metering to be accomplished with a proportional solenoid valve - t having a capacity too small to transfer the desired maximum flow to the fuel pump inlet ; the flow branch providing the additional desired, capacity. A flow check valve may be incorporated in the flow branch so that as the solenoid valve closes and the branch line pressure increases, the check valve closes, thereby stopping fuel flow to the fuel injection pump inlet. When the solenoid valve opens, the flow branch pressure decreases, allowing the check valve to open and transfer fuel through the flow branch line.

Given the low pressures encountered in the vehicle fuel supply, and therefore the compact size of the proportional solenoid which may be used at these pressures, electronically controlled fuel inlet metering may be expediently accomplished with the proportional solenoid using fuel supply passages either internal or external to the fuel injection pump. Preferably, the use of a stud containing a plurality of internal fluid circuits which sealingly engages an internal fuel bore in the fuel pump would allow the solenoid to be connected to supply and transfer passages internal to the fuel injection pump via the fluid circuits within the stud. Alternatively, the stud may be externally connected to the

vehicle fuel supply, with the stud fluid circuits connecting the proportional solenoid to the supply and internal fuel pump transfer passages.

Thus, a proportional solenoid valve and associated controller allows simple, low cost and reliable inlet metering for a mechanical fuel injection pump with greater precision than traditionally used mechanical metering valves. This translates to greater precision in the metering of fuel to the engine combustion chamber, with consequently improved engine fuel economy and lowered engine emissions. The use of an electronic proportional solenoid in combination with electronic control devices also allows the benefits of closed loop control, electronic fuel curve shaping and fly by wire operation to be obtained with otherwise conventional mechanical fuel injection pumps. The use of the proportional solenoid valve in combination with a parallel flow branch allows further minimization of the capacity and therefore size of the proportional solenoid valve needed. The use of an additional mechanical metering valve provides a redundant shutdown safety device, as well as the allowing for limp home capabilities.

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 representation of a fuel injection system incorporating proportional solenoid valve fuel inlet metering; Figure 2 is a schematic representation of the fuel injection system of Figure 1 further including a flow branch in parallel with the proportional solenoid valve ;

Figure 3 is a schematic representation of the fuel injection system of Figure 1 further including an upstream redundant mechanical metering valve ; Figure 4 is a side view, partly in section and partly in phantom, of a mechanical, distributor type fuel injection pump showing a proportional solenoid valve mounted directly into a hydraulic head; Figure 5 is a view similar to Figure 4 showing an alternative embodiment of the proportional solenoid valve and mounting ; Figure 6 is a fragmentary, partly in section and partly in phantom, view showing the solenoid valve and one embodiment of a stud in a fuel bore; Figure 7 is an external side view of a conventional'mecl1anical fuel injection pump to which a proportional solenoid valve has been mounted using a stud in a fuel bore; and Figure 8 is a view similar to Figure 6 showing a different embodiment of a stud mounting the solenoid valve to the fuel bore.

Description of the Preferred Embodiments Figure 1 is a schematic representation of a fuel injection system, comprising a fuel tank 10, a low pressure transfer pump 34 with an associated pressure regulator 48, for. delivering fuel to a pumping chamber 54 within the high pressure, fuel injection pump. Within the pumping chamber 54 the fuel is pressurized to be discharged to a plurality of fuel injection nozzles 66, either by way of individual fuel injector branch lines 64 or an external common rail (not shown). A proportional solenoid valve 82 is fluidly disposed intermediate to the transfer pump 34 and pumping chamber 54, for control of the flow rate, and thereby volume, of fuel admitted to the pumping chamber 54.

Referring now to Figure 5, the pump 20 has a housing 22. A rotor 26 and rotor drive shaft 28 are coaxially mounted in a body 24 of the housing 22. The rotor 26 rotates within a sleeve 30 within a hydraulic head 32. The head 32 is mounted to the housing 22. The pump 20 is adapted to be mounted on an internal combustion engine (not shown) to drive the shaft 28 and rotor 26 with the engine, normally at one-half engine speed.

A transfer pump 34 is provided at the outer end of the rotor 26.

A feed pump (not shown) supplies fuel from a tank 10 (Figure 1) via line filters 12 (Figure 1), a housing inlet 36 and an internal screen filter 38 to a transfer pump inlet 40. A transfer pump outlet annulus 42 is connected via an inclined passage 44 through the sleeve 30 and head 32 to a fuel bore 46. The fuel bore transfer pump regulator 48, shown schematically in Figures 1-3, regulates the outlet pressure of the transfer pump 34 by returning excess fuel to the transfer pump inlet 40.

The regulator 48 operates in a conventional manner so that the regulated outlet or transfer pressure increases with increasing pump speed (e. g., increases from, for example, 40 psi at idle speed to 110 psi at maximum speed) to meet the increased fuel requirements of the engine and to provide a speed related pressure for performing certain control functions of the pump 20, including operating certain auxiliary mechanisms of the pump 20, in relation to pump speed.

The pump rotor 26 has one or more diametral bores 50, each receiving a pair of opposed pumping plungers 52. A pumping chamber 54 formed by the bore (s) 50 is supplied fuel via. the fuel bore 46, a plurality of radial inlet ports 56 in the sleeve 30 (two of which are shown in Figure 5), a pair of diagonal inlet passages 58 and an axial bore 60 in the rotor.

Fuel is delivered from the pumping chamber 54 at high pressure through the axial bore 60 and an inclined distributor bore (not shown) in the rotor 26 to a plurality of distributor outlet ports (also not shown).

The outlet ports are connected to distributor fittings 62 angularly spaced around the hydraulic head 32. Each fuel injection fitting 62 is fluidly connected to a fuel injection nozzle 66 through a high pressure fuel injection line as shown in Figures 1-3. A delivery valve 68 Figures (1 - 3) may be mounted in the axial bore 60 to provide a sharp cut-off of fuel to the nozzles and a residual pressure in the downstream fuel lines leading to the nozzles.

An annular cam ring 72 having an internal cam surface actuates the pumping plungers 52 inwardly together as the rotor 26 rotates for delivering charges of fuel from the pumping chamber 54 at high pressure. A pair of roller assemblies, each comprising a roller 74 and roller shoe 76, are mounted in radial alignment with the plungers 52 for actuating the plungers 52 inwardly with the cam ring 72. The cam ring 72 may be angularly adjustable by a timing piston mechanism 78 for varying the delivery timing of the high pressure charges of fuel.

The inlet ports 56 are located around the sleeve 30 to register with the diagonal inlet passages 58 of the rotor 26 during the outward intake strokes of the plungers 52 as the. rotor 26 rotates. Similarly, the outlet ports are located to register with the distributor passage during the inward compression strokes of the plungers 52 as the rotor 26 rotates.

While a detailed structure for a distributor type fuel injection pump has been set forth for purposes of illustration, it should be understood that the invention is not limited to the described fuel injection pump structure and can find application in other varieties of fuel injection pumps. For example, fuel inlet metering may be

advantageous in fuel pump designs which use pumping plungers reciprocated in rotationally fixed plunger bores by rotatable internal or external cams.

In one embodiment of the invention shown schematically in Figure 1, a solenoid valve 82 with an inlet 84 and an outlet 86 is fluidly connected in series with the transfer pump 34 and the diagonal inlet passages 58 in the rotor 26. The solenoid valve 82 is operably connected to an electronic control unit 88 which controls its opening and closing. Preferably the solenoid valve 82 acts in a proportional manner; that is the percentage of valve opening, and thereby flow through the va) ve for a given pressure, is directly related to a signal sent by the electronic control unit 88. Closing of the solenoid'valve 82 by the control unit 88 restricts fuel flowing through the solenoid valve 82 and thereby through the diagonal inlet passages 58, the axial bore 60, the pumping chamber 54 and ultimately unto the engine combustion chamber. With a proportional solenoid valve, the control unit 88 can continuously vary the fuel flow into the pumping chamber 54 to any flow rate between no flow and the redefined maximum solenoid flow rate.

The electronic control unit 88 may be connected to at least one sensor 90. The sensor 90 generates a varying signal based on a desired engine or other vehicle parameter, or'combination of parameters, which is transmitted to the electronic control unit 88. The parameters may include, for example, fuel flow, air flow, engine speed, engine load, temperature, vehicle speed, or any other desired variable. A person of ordinary skill in the art would be able to define a program wherein the electronic control unit 88 actuates the proportional solenoid valve 82 in a desired manner to control the fuel admitted to, and thereby discharged from, the pumping chamber 54 as a result of sensor signals based on

these parameters. The use of an electronic control unit operably connected to receive signals from a sensor 90 and actuate the solenoid valve 82 as a result of those signals allows a"closed loop control" scheme of the solenoid valve 82, and thereby the vehicle engine. In a closed loop control scheme, the control unit 88 actuates the solenoid valve 82 to a desired output. The control unit 88, via the sensor 90, monitors the actual solenoid output, and corrects the solenoid actuation based on the difference between the desired and actual outputs.

It can be appreciated that the control of the fuel supply flow imparted by the proportional solenoid valve 82 is independent of both the rotational timing of the fuel supply from the radial inlet port 56 to the diagonal inlet passage 58 and the plunger stroke timing'imparted by angular adjustment of the cam ring 72.

With reference to Figures 4 and 5, the proportional solenoid valve 82 may be positioned in or adjacent to the exterior of the fuel pump housing 22. As shown in Figure 5, the solenoid valve 82 is positioned at least partially within the fuel bore 46. The solenoid valve inlet 84 is fluidly connected to the inclined passage and the solenoid valve outlet 86 is fluidly connected to the radial inlet ports 56. In a variation shown in Figure 4, a substantially vertical transfer bore 92 in the head 32 fluidly connects the inclined passage 44 to a fuel bore 46'. A somewhat smaller solenoid 82'is positioned at least partially within the fuel bore 46'with the solenoid valve inlet 84'fluidly connected to the vertical transfer bore 92 and the solenoid valve outlet 86'fluidly connected to the radial inlet ports 56. The variation of Figure 4 allows the placement of a proportional solenoid valve 82'into the same fuel bore 46'which previously housed a mechanical metering valve, without additional modification to the fuel pump fuel passages.

In another embodiment shown schematically in Figure 3, a mechanical metering valve 94 with an inlet and outlet, 96 and 98 respectively, is disposed in series with the proportional solenoid valve 82 between the transfer pump 34 and the diagonal inlet passages 58 in the rotor 26. The solenoid valve 82 is operably connected to an electronic control unit 88. The mechanical metering valve 94 is preferably a rotary type metering valve. Rotation of the metering valve control arm 100 varies the restriction of the metering valve to fuel flow therethrough. Note that while Figure 3 shows the mechanical metering valve 94 disposed between the transfer pump 34 and solenoid valve 82, it may be just as advantageously placed downstream of the solenoid valve 82 between the solenoid valve 82 and diagonal inlet passages 58.

A centrifugal governor 104 is mounted to the shaft 28 and enclosed within the high pressure pump housing 22. The governor 104 is connected to the metering valve control arm 100 by a link mechanism 106. The centrifugal governor 104 imposes a force on the link mechanism 106, which increases with the speed of the shaft 28. A governor spring assembly 108 imposes an opposing force against the link mechanism 106. The governor spring 108 is operably connected to a throttle (not shown) to vary the. opposing force exerted. The governor 104 rotates the metering ; valve 94, via the link mechanism 106, in a closing direction to increase the fuel restriction if the pump speed increases above an equilibrium speed established by the opposing forces of the governor 104 and governor spring assembly 108.

Similarly, the governor 104 rotates the metering valve 94 in an opening direction to reduce the fuel restriction if the shaft speed falls below the equilibrium speed.

The use of both a mechanical metering valve 94 and a proportional solenoid valve 82 fluidly connected in series between the transfer pump 34 and the diagonal inlet passages 58 allows the proportional solenoid valve 82 to be retrofitted to existing mechanical fuel injection pumps. Thus, existing pumps can obtain the advantages of precise fuel metering to the pumping chamber 54 with consequent improvements in fuel economy and engine emissions; closed loop fuel injection pump control ; and electronic fuel curve shaping. Additionally, the redundant mechanical metering valve 94 allows the possibility of a high pressure fuel pump"limp home"mode. That is, the mechanical metering valve 94 in combination with the governor 1 04 and governor spring assembly 108 allows operator control of the high pressure pump 20, and thereby the engine, in the unlikely event the proportional- solenoid valve 82 should fail. Naturally, the advantages obtained from proportional solenoid 82 control of the fuel pump 20 are lost when in the limp home mode.

In a variation shown in Figure 6, the inclined passage 44 terminates in a head bore 112 generally horizontally oriented in the head 32. The bore 112 fluidly connects the inclined passage 44 to the fuel bore 46 (not shown in Figure 6). A mechanical metering valve 94 (not shown in Figure 6) is disposed in the fuel bore 46 for control of the fuel flow to the pumping chamber as previously described. A stud 114 sealingly engages the bore 112. The stud defines internal fuel passages. A stud source passage 116 fluidly connects the inclined passage 44 to an inlet 120 of a solenoid valve 118. The solenoid valve outlet 122 is fluidly connected to a stud sink passage 124, which is fluidly connected to the fuel bore 46. Thus fuel flow is controlled by both the proportional solenoid valve 118 and the mechanical metering valve 94. The use of a stud 114 in a head bore 112 allows compact

placement of a solenoid valve in existing mechanical fuel pump designs as shown in Figure 7.

In another variation, shown in Figure 8, a stud 128 sealingly engages the head bore 112. The inclined passage 44 is fluidly sealed off and not used. A supply passage 130 fluidly connects an external fuel inlet 132 to the solenoid valve inlet 120. The external inlet 132 is connected to a source of fuel from the tank 10 (see Figure 1) supplied buy an external lift pump (not shown) or external conduits from transfer pump. The stud sink passage 134 fluidly connects the solenoid outlet 1 22 to the fuel bore 46 (not shown in Figure 8). The use of a stud 1 28 allows conventional mechanics ! fue) injection pumps to be supplied with an external fuel source for solenoid control in a compact fashion.

In a further embodiment schematically shown in Figure 2, a flow branch 138 is fluidly connected in parallel with the proportional solenoid valve 82 between the transfer pump 34 and the diagonal inlet passages 58. The flow branch 138 allows the use of a proportional solenoid 82 with a flow capacity less than the desired maximum capacity of the high pressure fuel pump 20. The mechanical metering valve 94 provides control so that fuel flow to the pumping chamber 54 may be stopped.

Alternatively, the flow branch 138 may include a check valve 140 to limit flow within the branch 138. Biasing of the check valve 140 allows the valve to remain open until a pressure threshold is reached, at which point the check valve 140 closes to prevent further flow therethrough.

The resilient biasing may be, for example, by gravity or a spring 142 forcing a check ball 144 away from a seat 146. In operation, when the solenoid valve 82 is fully open, pressure upstream of the solenoid valve 82 and within the flow branch 138, is below the check valve 140 threshold, thereby allowing fuel to flow through the flow branch 138.

As the solenoid valve 82 closes, pressure upstream of the solenoid

valve 82 increases. When the pressure upstream of the solenoid valve 82 rises over the check valve 140, threshold, the check valve closes, preventing further fuel flow within the flow branch 138. Actuation of the solenoid valve 82 to the closed position will thereby terminate fuel flow through the solenoid valve 82 and through the flow branch 138.

The use of a check valve 140 may obviate the need for a mechanical valve. The flow branch 138 may also include restrictions 122 to limit the maximum flow therethrough..

While preferred 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 of ordinary skill in the art without departing from the spirit and scope of- the present invention.