Single solenoid floating piston distributor pump

Abstract

 A pump including a metering chamber (40) and a timing chamber (50) formed on either side of a floating piston (56) slidably mounted in an axially extending bore. An electromagnetic control valve (18) controls the discharge of fuel from the timing chamber (50) for creating a variable hydraulic link between a plunger (58) and the floating piston (56) to thereby control the injection timing. In order to vary the quantity of fuel stored in the metering chamber (40) during the downward movement of the floating piston (56), the control valve (18) is variably opened for the admission of fuel at supply pressure into the timing chamber (50), thereby arresting the metering piston (56) in a predetermined position.

Description

Related Applications

[0001] The instant application is related to U.S. Serial Numbers 6,948 and 6,949, both of which were filed on January 25, 1979, Serial No. 6,949 having issued 'as Patent No. 4,235,374. The instant application is also related to _US Serial No. 219 299 filed in the name of Frank Woodruff, and to US Serial No. 217 298 filed in the name of Edwin Ben Watson.

[0002] Further, this application is related to application Serial No. 203,827, Serial No. 203,830 and Serial No. 203,831, all filed on November 4, 1980. The above-referenced applications and patent are specifically incorporated herein by reference.

Background of the Invention

[0003] This invention is generally related to distributor type fuel injection pumps for controlling the quantity and timing of injection of fuel into the cylinder of an engine, and in particular is related to a distributor type fuel injection pump in which the metering and timing of injection of fuel is controlled by a single electromagnetic control valve.

[0004] Distributor fuel injection pumps in which the time of injection and the period of injection are' both controlled mechanically or hydraulically are well known in the art. However, recent advances in electronics have resulted in the development of electronic fuel control systems which are capable of very accurately computing fuel quantity and timing requirements in response to one or more operational parameters of the engine. These electronic control systems include electronic control units which are capable of not only computing the required fuel quantity, but also the time at which the fuel is to be injected into the cylinder to optimize the engine's performance. One such electronic control unit is disclosed in application Serial No. 945,988. Another electronic control unit is disclosed in Patent No. 4,219,154. Both disclosures are incorporated herein by reference. Also recently, the invention described in the above-referenced application Serial Numbers 6,948 and 6,949 were developed, the application of the invention being initially in the field of unit injectors, however, it has been discovered that inventive concepts described in the above-referenced application could also be applied to distribution pumps to great advantage. The resulting application of that unit injector technology to distribution pumps has resulted in the invention of the present application.

Summary of the Invention

[0005] The invention is a distributor type fuel injection pump in which the injection timing and fuel metering is controlled by a single electromagnetic control device, wherein the fuel for an injection into a particular cylinder is premetered prior to that injection. In a cycle of operation, the rotation of the engine causes the rotation of a cam mounted on a shaft which is rotating at a speed which is half the speed of a four-stroke-cycle engine rotation. The cam operates to drive a piston in a cavity, the cavity also forming a metering chamber and a timing chamber, the two chambers being separated by a free piston. As the piston is being driven into the chamber, in particularly the timing chamber, the point of injection is selected by an electronic control unit and a pulse is generated to either energize or de-energize a control valve. This creates a hydraulic link between the driving piston or primary piston and the free piston, thereby driving the floating piston into the chamber.

[0006] This pressurizes the fuel in the metering chamber, which fuel is then .injected to a particular cylinder determined by the position of the distributor head. After injection has taken place, the driving piston is allowed to move out of the chamber, thereby permitting the free piston to move away from the bottom of the chamber under influence of the supply pressure., This allows fuel to flow into the metering chamber. The fuel may flow into the metering chamber in accordance with a pressure-time metering concept with a restricted oriface or a volumetric metering concept determined by the position of the piston. When the proper amount of fuel has been allowed into the metering chamber, the control valve is de-energized and the subsequent movement of the driving piston out of the chamber allows fuel to enter into the timing chamber. Thus, the system is prepared for the next injection of fuel into a different cylinder of the engine.

[0007] With the system of the present invention, a single control solenoid, and a single pulse from an electronic control unit, is utilized to control the initiation of injection of fuel into a particular cylinder and also to control the amount of fuel that is to be injected into the next cylinder of the engine. The control valve may be very fast acting and thus precise control of timing and metering may be accomplished with the system of the present invention.

Brief Description of the Drawings

[0008] 

FIGURE 1 is a perspective view, partially in cross section, of a distributor fuel pump for an internal combustion engine incorporating the features of the present invention; and

FIGURE 2 is a cross-sectional view of a modified form of the inventive concepts of FIGURE 1 and particularly showing the control assembly and distribution assembly of the system of the present invention.

Detailed Description of a Preferred and Modified Embodiment of the Present Invention

[0009] Referring now to Figure 1, there its illustrated a distribution type fuel pump 10 which is particularly adapted to be utilized in conjunction with controlling the time of injection and amount of injection of fuel into an internal combustion engine, particularly of the diesel type. Specifically, the pump 10 includes a gear type driving mechanism 12, a timing and premetering assembly 14, the fuel output from the timing and premetering assembly 14 being fed to a distribution head 16 which controls the particular cylinder to which each pulse of fuel is fed in the internal combustion engine. The control of the timing and premetering assembly 14 is accomplished by a electromagnetic solenoid control unit 18.

[0010] Referring to the specific details of the various sections of the distribution pump shown in Figure 1, it is seen that the driving mechanism 12 is basically a gear assembly including a main gear 20 which is driven from the engine with which the distribution pump is associated. The gear 20 is driven at half the speed of the engine thereby rotating one revolution per two revolutions of the engine. The gear 20 is mounted on a shaft (not shown) which drives a second gear 22 which can be of reduced diameter relative to the gear 20. Gear 22 in turn drives a gear 24 which is mounted on a shaft 26, the shaft.26 rotating at the same speed as that of the gear 20, the particular application illustrated being utilized in a four cycle engine. The rotation of the shaft 26 will drive a cam 28.

[0011] The cam is utilized to drive the timing and premetering assembly 14 in a manner to be described. It should be noted that the configuration and operation of the timing and premetering section 14 is very similar to that described in the above-referenced application 6,948 and U.S. Patent No. 4,235,374. For a very detailed description of the operation of the timing a premetering section., reference is made to that application and U.S. Patent. However, for purposes of illustration, certain details of the assembly 14 will be described herein.

[0012] Fuel is introduced to the distribution pump by means of a conduit 36, the conduit 36 supplying fuel to the internal case of the distribution pump. The supply of fuel is fed from conduit 36 through a passageway 38 formed in the body of the timing and premetering section 14. As is seen from the drawing, this fuel is fed to a timing chamber 40 by means of a passageway 42 through a check valve 44. Fuel is also fed to the control valve 18 by means of a passageway 48, the output of the control valve being fed to a timing chamber 50 by means of a passageway 52. The metering chamber 40 and the timing chamber 50 are separated by means of a floating piston 56. The rotational motion of the shaft 26 and cam 28 are translated into reciprocating motion by means of a driving piston 58. The piston 58 is urged toward the cam element 28 by means of a spring 62. The fuel pulse output from the metering chamber is fed to the distribution head 16 by means of a passageway 64.

[0013] The distribution head is driven by the same shaft which is driving the gear 22. Thus, the output of the distribution head 16 is synchronized with the opration of the cam 28.

[0014] The distribution head 16 includes a plurality of output connectors 70, one connector being connected to each cylinder of the internal combution engine being controlled. An embodiment of a distribution head will be described in conjunction with the description of Figure 2.

[0015] In operation, and assuming that a preselected amount of fuel has been metered into metering chamber 40, and the piston 58 is at its downmost position, the shaft 26 is rotated and the cam surface forces driving piston upwardly against the action of the spring 62. During this part of the operation, the control valve 18 is in a state such that fuel can flow from the timing chamber 50 out through passageway 52 and back to the source of fuel supply. At the point in the rotation of the engine at which injection is to occur, the control solenoid 18 is energized to preclude fuel flow out of the timing chamber and thus pressurize the fuel in the timing chamber. The continued motion of the driving piston 58 pressurizes the fuel in the metering chamber 40 and causes pressurized fuel to be injected from an injection connected to a line (not shown) connected to one of the output connectors 70, depending on the position of the distributor head. This drives piston 56 upwardly until such time as a passageway 72 is put into fluid communication with the passageway shown in the free piston 56. This dumps fuel from the metering chamber 40 and reduces the pressure therein. At approximately the same time, the passageway- which contains the check valve 74 is put into fluid communication with the-timing chamber to permit fuel to be dumped from the timing chamber as the piston 58 is driven further into the timing chamber.

[0016] When the piston 58 is fully extended into the timing chamber, the cam surface then starts to permit the piston 58 to be withdrawn. With -the control solenoid still in the energized state, the withdrawing of piston 58 creates a reduced pressure in the timing chamber to cause the floating piston 56 to follow the downward motion of the driving piston 58. The draws fuel into the metering chamber 40 through the passageway 42. When the desired amount of fuel is metered into the metering chamber 40, the control solenoid 18 is de-energized which stops the downward motion of the free piston 56 and thereby stops metering of fuel into the metering chamber 40. Further downward motion of the piston 58 causes fuel to be metered into the timing chamber by means of passageway 52. The cycle is then complete and ready for the next timing and injection cycle for the next cylinder.

[0017] Referring now to Figure 2, there is illustrated some schematic details of the control solenoid 18 and the distribution head 16, the details being shown in schematic fashion to illustrate the principle of the present invention. As was described in conjunction with Figure 1, a cam 80, shown schematically for a single injection cycle, drives piston 58 upwardly into the timing chamber 50. The control solenoid 18 is illustrated as having a coil 82 which electromagnetically controls the position of an armature 84, the end of the armature having formed thereon a control valve shown in the form of a ball 86. In the position shown, the coil 82 is de-energized and piston 58 is driven upwardly into the timing chamber 50. At the point that injection is to occur, solenoid 82 is energized to pull ball 86 to the right and shut off a passageway 90. Prior to the ball shutting off the passageway 90, fuel is permitted to flow from the timing chamber, through passageway 42 and back to the supply by means of a passageway 38. When ball 86 is seated, the fuel in the timing chamber 50 is pressurized which in turn pressurizes the fuel in metering chamber 40. With further upward movement of piston 58, the free piston -56 is driven upwardly to cause fuel to be pressurized in the distribution head 16. This pressurized fuel causes a valve, including a ball 92, which ball 92 is unseated to force pressurized fuel out to the engine cylinder by means of a passageway 96. The distribution head includes a shaft 98 which is rotated in synchronism with the cam 80, thus distributing each pulse of fuel to the respective cylinders. In the particular embodiment illustrated in Figure 2, the cylinder associated with conduit 96 is provided a pulse of fuel and the cylinder associated with a conduit 100 is provided a pulse of fuel one engine revolution later than that provided in the cylinder connected to 96.

[0018] It will be readily apparent to the skilled artesian that the foregoing description of the embodiments of the present invention may be modified in many ways and the invention should not be limited by the above description. Rather, the scope of the invention should be determined by the scope of the appended claims.

Claims

1. A fuel control system for a multicylinder internal combustion engine comprising a housing having a fuel inlet and a plurality of fuel outlets, one for each cylinder of the engine, means operatively connected to the engine for pressurizing fuel between said inlet and outlet ports, said pressurizing means including a cam element;

a body having an axially extending central bore;

a primary pumping plunger operatively associated with said cam element and a secondary free element positioned within said body for at least partial axial movement therein;

a passageway situated at the end of said central bore remote from said primary pumping plunger and in fluid communication, with each of said fluid outlets in sequence;

a timing chamber defined in said body between said primary pumping plunger and said secondary element;

a metering chamber defined in said body between said secondary element and said nozzle;

passages in said body for receiving pressurized fuel and transmitting said fuel into said timing chamber and said metering chamber;

means for controlling (1) the timing of the discharge of fuel from the metering chamber through the nozzle and (2) the quantity of fuel stored in said metering chamber subsequent to said discharge of fuel;

a distribution head assembly having an inlet passage in communication with said passageway and having a portion thereof rotated in synchronism with said cam element and adapted to distribute fuel from said metering chamber to each of said fuel outlets, in succession.

2. The system of Claim 1 wherein said control means controls the admission of fuel into said timing chamber for creating a hydraulic link between said primary plunger and secondary element to selectively hydraulically connect said primary pumping plunger and said secondary element.

3. The system of Claim 2 wherein said distribution head is continuously in fluid communication with said metering chamber.

4. The system of Claim 3 wherein said secondary element is a floating piston adapted to move and control the volume of said metering chamber.

5. The system of Claim 2 wherein said control means directly controls the flow of-fuel into said timing chamber and indirectly controls the flow of fuel into said metering chamber.

Drawing