US3140702A - Volumetric efficiency control for fuel injection system - Google Patents

Description

; July 14, 1964 Filed April 16, 1963 B. FISHMAN ETAL 3,140,702

VOLUMETRIC EFFICIENCY CONTROL FOR FUEL INJECTION SYSTEMS 2 Sheets-Sheet 1 fvn 6. (1 Pump AN/YULUS I9 j 'Ll 3 Clo/16mm- D/5PL4CEMENT' PUMP Pu CAM/7Z6 LEVEQ 424170 I --ZO 3 7 Ti [3.1. Dim

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1N VENTORS 559M190 HsHM/w M Wanda. A QNE Y6 July 14. 1964 B. FISHMAN ETAL 3,140,702

VOLUMETRIC EFFICIENCY CONTROL FOR FUEL INJECTION SYSTEMS Filed April 16, 1963 2 Sheets-Sheet 2 INVENTORS Bap/#14 0 Fish MAN Nag/ 1 M Basra/KW United States Patent York Filed Apr. 16, 1963, Ser. No. 273,507 (Ilaims. (Cl. 123140) This invention relates in general to a means for maintaining an optimum fuel to air ratio at a wide range of engine speeds in a fuel injection system and more particularly to a technique for making the pneumatic control over fuel intake responsive to engine speed.

. The problem to which this invention is addressed resides in the fact that the fuel injection pump in a fuel injection system operates independently of the air intake rate. In each engine there is an optimum fuel to air ratio to obtain maximum power. For a given throttle position, the fuel injector pump maintains a constant rate at which the fuel is injected into the combustion chambers. By contrast, the rate at which air is sucked into the combustion chamber is a function of engine speed. As a general rule, the amount of air increases as engine speed increases up to a certain point then above that point the rate at which air is sucked into the combustion chamber gradually decreases as speed increases. Accordingly, the optimum power for a given throttle position can be obtained at only two engine speed points.

' Accordingly, it is a purpose of this invention to devise a technique for varying the fuel injector pump output as a partial function of air intake rate.

However, the major value of this invention is under open throttle conditions since that is when additional power is needed and desired. After all, under less than open throttle conditions the operator can obtain more power simply by further opening the throttle. The following description therefore is directed to what occurs at open throttle conditions.

It is thus a more specific purpose of this invention to increase the power available under open throttleconditions.

Other objects and features of this invention will be apparent from a consideration of the drawings and the following detailed discussion, in which:

FIG. 1 is a mechanical schematic illustration of an embodiment of this invention,

FIG. 2 is a graphical representation of the flow rate of air into the combustion chamber as a function of engine speed,

FIG. 3 is a plan view of the piston and lever unit portion of the system diagrammed in FIG. 1,

FIG. 4 is a section along the plane 4-4 of FIG. 3, and

FIG. 5 is an illustration of one of the fine adjustments that may be made to the operation of this invention.

A description of FIG. 1 will give the clearest and simplest explanation of this invention. The pump capsule 11 is a portion of a fuel pump which is not otherwise shown herein. In one standard fuel pump, the pump capsule 11 is mechanically linked to the other operative elements of the fuel pump so that the displacement of the pump capsule 11 along the axis X-X controls the rate at which fuel is pumped to the injector nozzle by the fuel pump. In that standard pump, the pump capsule 11 is surrounded by a pressure chamber and the inside of the capsule 11 itself communicates to ambient pressure so that as ambient pressure changes, the fuel pump output will change and thereby maintain an appropriate fuel to air ratio; appropriate, that is, to the ambient pressure.

A description of the operation of this standard fuel pump for which the invention is intended is included in snares Patented July 14, 1964 the co-pending United States patent application, Serial. No. 183,872 filed on March 30, 1962 by Leon H. Hall and assigned to Simmonds Precision Products, Inc.

It is one of the features of this invention that the volumetric control mechanism can be kept simple and relatively inexpensive by virtue of the fact that it operates on a control element (the pump capsule 11) which is already incorporated into fuel pumps. In general, this invention is readily adaptable to any fuel pump having a pneumatic device controlling the fuel pump output.

This invention adds a lever arm 12 to exert pressure along the axis X-X and thereby partially control the axial expansion of the pump capsule 11; and through such control over the pump capsule ll exert a partial control over the output of the fuel pump. The pressure exerted by the end 13 of the lever arm 12 is determined by the pressure exerted on the other end 14 of the lever arm 12 by a piston 16. The following description is directed to the control over the operation of that piston 16.

The entire device 18 of this invention may be operated off a tap to the fuel line 19 which supplies fuel to the device 18 and which drains through a connection 2% to the fuel supply. The vent restrictor 21 near the input tap 19 serves to limit the volume of fuel drawn into the device It to substantially the amount required by the operation of the device 13 of this invention. It should be recog nized that the fluid used to operate this device 18 is not limited to fuel. Fuel is normally used and mentioned herein because it is conveniently available where a fuel pump is being controlled.

A constant displacement pump 22 such as a Geroter pump located near the tap 19 to the fuel line serves to bring fuel from the fuel line into the device 18. The important characteristic of the pump 22 that dictates the selection of a pump such as the Geroter pump is that the pump 22 must exhibit a constant displacement per cycle. The pump 22 is driven by the engine so that the pump 22 speed is a direct function of engine speed. Therefore, the rate at which fuel is pumped through the device 18 by this constant displacement pump 22 will be a direct function of engine speed.

As fluid is pumped by the Geroter pump 22 into the system 13, it will be forced along the line 27 into the chamber 24 above the piston 16 forcing the piston in down against the end 14 of the lever 12. The restrictor 26 serves to create pressure in the line 27 so that there will be a pressure build up in the chamber 24. The relief valve 28 is shown in its normal position and will bar escape through the line 29 for fuel being pumped by the pump 22 until pressure reaches a certain level as will.

be described further on.

In the situation just described, as engine speed increases, pump 22 speed increases, and the volume of fuel pumped through the fuel line 27 increases. The restrictor 26 thereby causes a build up of pressure in the fuel line 27 with the corresponding build up of pressure in the cham ber 24 and a consequent increase of axial pressure at 13 on the pump capsule 11. In this fashionthe axial pressure exerted on the pump capsule 11 by the device 13 is made to increase as engine speed increases.

However, above a certain engine speed the rate at which air is taken into the engines combustion chamber starts to decrease. It is desired to have this device 18 track with a decrease in air intake as engine speed increases over a certain point. By means of the relief valve 28 and line 29 this additional goal is achieved. The relief valve 28 is a spring 30 loaded valve, the spring 30 of which can be adjusted .to retract at a desired pressure. That desired pressure can be experimentally determined as the pressure in the fuel line 27 when the engine speed is at the point where the maximum air intake rate is being achieved. At that maximum point the relief valve 28 opens and the line 27 is connected through the line 29 to the chamber 32 at the under side of the piston 16. As engine speed increases, the restrictor 34- causes pressure in the line 29, and thus in the chamber 32, to build up and oppose the pressure in the chamber 24. In this fashion, increasing engine speed will cause increasing pressure in the chamber 32 with a consequent lessening of the net downward pressure on the end 14 of the lever 12. Accordingly, the pressure exerted by the end 13 of the lever 12 on the pump capsule 11 will decrease as engine speed increases over the point at which the relief valve 28 opens. Control over the pump capsule 11 will, therefore, track with the air intake rate to the engine.

A typical curve showing the way in which the air intake rate varies with engine speed is shown in FIG. 2. This curve was taken by measuring peak pressure in the ram pipes of the engine and was plotted against engine speed in revolutions per minute. The pressure was measured in millimeters of mercury absolute. As may be seen from FIG. 2, the maximum air intake rate in the particular engine illustrated is at approximately 4400 rpm. The relief valve 28 is therefore designed to open at the pressure built up in the line 27 at such engine speed.

In order to make the volumetric efliciency control device 18 closely track with the curve 2, there are various parameters of this device 18 which can be varied and balanced off against one another. By adjusting these variables appropriately, the shape of the fuel flow volume versus engine speed curve can be matched quite closely to the shape of the air flow volume versus engine speed curve, which latter curve is shown in FIG. 2. These parameters are:

(l) The size of the constant displacement pump 22. For a given magnitude of restriction in the restrictor 26 and in the restrictor 34, the greater the size of the pump 22, the greater will be the slope of the fuel flow versus speed curve. Thus if the fuel rate versus speed curve is too shallow compared to the air intake rate versus speed curve, an increase in the size of the pump 22 will make the former curve less shallow and cause it to more closely approximate the latter curve.

(2) The magnitude of the restriction in the restrictor 26 will affect the slope of the curve at engine speeds less than speed corresponding to the maximum air intake rate.

(3) The magnitude of the restriction in the restrictor 34 will affect the slope of the descending portion of the curve. The restrictor 34 only comes into play after the relief valve 28 has opened and thus the restrictor 34 can only affect the descending portion of the fuel intake rate versus engine speed curve. Restrictor 26 will have some affect on the descending portion just as it does on the ascending portion of the curve but restrictor 26 can be designed with the ascending portion of the curve in mind and restrictor 34 should provide adequate additional design control to closely approximate the slope desired on the descending portion of the curve.

(4) As pointed out above, the pressure point in the line 27 at which the relief valve 28 opens will determine the peak point of the curve. This point can be adjusted by the selection of the spring 30 and therefore permit a selection of the speed at which the maximum fuel flow rate is obtained.

(5) The deflection rate of the spring 30 can be selected to have some control over the shape of the curve near its maximum point. A stiff spring 30 can cause a flattening out of the curve near its maximum point by providing partial leakage around the valve piston 35 before it fully opens or fully closes. More specifically, the piston 35 as it uncovers the opening to the line 29 will provide a restriction for the transmission of some but not all of the pressure in the main line 27. A spring 30 having a rapid stress build up as it deflects will cause the passage around the piston 35 to the line 29 to be kept restricted until adequate pressure is developed to completely open the valve. The result will be a flatter peak on the fuel flow versus speed curve than with a more compliant spring.

(6) Adjustment of the pivot point 36 of the lever 12 will affect the sensitivity of capsule 11 response to pressure build up on the piston 16 end 14 of the lever 12. The lever 12 illustrated has a two to one ratio between the arm terminating in point 13 and the arm terminating in point 14. A decrease in this ratio will decrease the sensitivity of capsule 11 response to a given pressure change on the piston 16 end 14 of the lever 12 and thus mean a flattening of the fuel intake rate versus engine speed curve.

There are a couple of design features which have to be kept in mind to avoid undesirable, because uncontrolled, changes in the operating characteristics of this volumetric efficiency control apparatus 13.

It is important that the tap 19 to the fuel line he to a point of constant pressure so that the output of the pump 22 will be solely a function of engine speed and not of inlet pressure. The vent restrictor 21 tends to isolate the pressure downstream of the restrictor 21 from variations in the pressure upstream of the restrictor 21. This particular design point is especially important in engines on vehicles because the pressure at other points in the fuel system will be a function of the battery voltage that runs the'entire injector system. Battery voltage is in part a function or" the particular battery used, its age and its pst history, and consequently it is important to avoid having that irrelevant factor affect the control characteristics of the volumetric efliciency control device 18.

Where fuel or other liquid is used that has a large viscosity change with temperature change, the flexibility of the above described system is somewhat limited. However, the system can be made to work with such a fuel and could be designed to take into account the viscosity versus temperature function of the fuel. As long as viscosity is repeatable with temperature, this additional factor can be taken into account. However, it might be preferable in instances where variable viscosity is used to use a liquid supply other than fuel for the purpose of operating the volumetric elficiency control device 18.

A by-pass line 37 from the restrictor 21 to the drain 26 is included solely to provide a path for excess liquid in order to avoid a build up of pressure at the input to the pump 22. This by-pass line 37 assures that the pump input will remain constant. Concerning the importance of maintaining a constant inlet pressure to the pump 22, it should be noted that a regulating valve could be inserted into the system ahead of the pump 22 if a constant pressure point were not otherwise available.

The line 40 from the underside of the piston in the relief valve 28 serves to maintain a constant pressure on the back of the piston 35. Any constant pressure outlet could be used but since there is bound to be some fluid leakage it is convenient to use the drain 20 as that outlet. Thus the line assures that the spring 36 will provide the only back pressure on the piston 35.

FIGS. 3 and 4 simply show the details of a piston mechanism which has been designed for the system of FIG. 1. As may be seen in FIG. 4, the piston 16 is suspended in its casing 38 by means of a diaphragm 39 that is bonded to the piston 16 and casing 38.

FIG. 5 illustrates a fulcrum device 44 about which the lever 12 can pivot and which may be used to change the pivot point and thus the lever 12 arm ratio to provide the kind of control discussed above. The pivot point for the lever 12 is the top of a ball 4-5 which ball 45 is eccentrically mounted on the fulcrum 44. By rotating the fulcrum 44, the ball 45 turns eccentrically and therefore changes the ratio of the lever 12 arms. In FIG. 5, the vertical axis of the ball 45 is shown displaced from the vertical axis of the fulcrum 44 by the amount D.

There are certain variations and adaptations to this invention which would be apparent to one skilled in the 5. art. The claims are accordingly intended to cover all such variations as fall within the inventive concept.

For example, the pump capsule 11 illustrated is a bellows. However, any other form of pneumatic control device in a fuel injection pump could be readily linked to the volumetric eificiency control device of this invention.

What is claimed is:

1. A volumetric efi'iciency control device adapted to provide a partial control over the output of a pneumatically controlled fuel injection jump in an internal combustion engine, wherein the pneumatic control includes a pressure responsive element responsive to energize manifold pressure for controlling the fuel pump, comprising:

a pivotally mounted lever having its first end in contact with said pneumatic control device whereby variations in the position of said first end of said lever will cause said pneumatic control device to vary the output of said pump,

a piston in contact with said second end of said lever and mounted in a casing thereby dividing said casing into a first chamber and a second chamber, said second end of said lever being in said second chamber of said casing, whereby variations in the axial position of said piston will cause said lever to rotate about its pivot point and thereby vary the position of said first end of said lever,

a substantially constant pressure source of fluid,

a secondary pump having its input connected to said source of fluid, said secondary pump being run off said engine so that the rate of said fluid pumped by said pump is a function of engine speed,

a main fluid pressure line connected to the output of said pump,

a first subsidiary fluid line connecting said first chamber of said casing to said main fluid pressure line downstream from the output of said pump,

a second subsidiary fluid line connecting said second chamber of said casing to said main fluid pressure line downstream of the main fluid line connection to said first subsidiary fluid line, and

a normally closed relief valve in said second subsidiary line, said relief valve opening at a pre-determined pressure to admit fluid from said main line to said second chamber when main line pressure is above said pre-determined value.

2. A volumetric efficiency control device adapted to provide a partial control over the output of a pneumatically controlled fuel injection pump in an internal combustion engine, wherein the pneumatic control includes a pressure responsive element responsive to engine manifold pressure for controlling the fuel pump, comprising:

a pivotally mounted lever having its first end in contact with said pneumatic control device whereby variations in the positon of said first end of said lever will cause said pneumatic control device to vary the output of said pump,

a piston in contact with said second end of said lever and mounted in a casing thereby dividing said easing into a first chamber and a second chamber, said second end of said lever being in said second chamber of said casing, whereby variations in the axial position of said piston will cause said lever to rotate about its pivot point and thereby vary the position of said first end of said lever,

a substantially constant pressure source of fluid,

a secondary pump havingits input connected to said source of fluid, said secondary pump being run off said engine so that the rate of said fluid pumped by said pump is a function of engine speed,

a main fluid line connected to the output of said a first subsidiary fluid line connecting said first chamber of said casing to said main fluid line downstream from the output of said pump,

a second subsidiary fluid line connecting said second r O chamber of said casing to said main fluid line downstream of the main fluid line connection to said first subsidiary fluid line,

' a normally closed relief valve in said second subsidiary line, said relief valve opening at a pre-determined pressure to admit fluid from said main line to said second chamber when main line pressure is above said pre-determined value, and

a first constriction in said main fluid line downstream of the connection to said second subsidiary fluid line to develop pressure in said main fluid line as a function of said secondary pump output when said relief valve is closed, and

a constricted fluid line connecting said second chamber to said main fluid line downstream of said first constriction to develop pressure in said second chamber as a function of the fluid flow rate through said second subsidiary fluid line.

3. A volumetric eificiency control device adapted to provide a partial control over the output of a pneumatically controlled fuel injection pump in an internal combustion engine, wherein the pneumatic control includes a pressure responsive element responsive to engine manifold pressure for controlling the fuel pump, comprising:

' a pivotally mounted lever having its first end in contact with said pneumatic control device whereby variations in the position of said first end will cause said pneumatic control device to vary the said output of said pump, said lever being pivotally mounted intermediate its first end and its second end,

a piston resting on said second end of said lever whereby movement of said piston will cause said lever to pivot and thereby move said first end of said lever,

a substantially constant pressure source of fluid,

a secondary pump having its input connected to said source of fluid, said secondary pump being run off said engine so that the rate of fluid pumped by said pump is a function of engine speed,

a main fluid line connected to the output of said secondary pump and in communication with a first side of said piston,

a constriction in said first fluid line downstream of said communication to said piston, whereby the output of said secondary pump will create pressure on said first side of said piston,

a second fluid line in communication with said first fluid line downstream of said communication to said first side of said secondary pump and upstream of said first constriction, said second fluid line communicating to said second side of said piston,

a normally closed relief valve in said second fluid line, said relief valve adapted to open at a pre-determined pressure to admit fluid from said first line to create pressure on said second side of said piston,

whereby increasing engine speed will increase said secondary pump output thereby increasing the pressure on said first side of said piston until said predetermined pressure is reached at which pre-determined pressure said relief valve will open and admit pressure to said second side of said piston,

whereby at pressures less than said pre-determined pressure, first line pressure on said first side of said piston will cause said lever to pivot in a first direction and at pressures above said pre-determined pressure, pressure on said second side of said piston will tend to cancel pressure on said first side of said piston causing said lever to pivot in the opposite direction.

4. A volumetric efficiency control device adapted to provide a partial control over the output of a pneumatically controlled fuel injection pump in an internal combustion engine, wherein the pneumatic control includes a pressure responsive element responsive to engine manifold pressure for controlling the fuel pump, comprising:

a pivotally mounted lever having a first end in contact with the pneumatic control of said pump whereby variations in the force applied by said first end of said lever to said pneumatic control will cause a variation in the said output of said pump,

a piston in contact with the second end of said lever and mounted in a casing thereby dividing said casing 5 into a first chamber and a second chamber, said piston being exposed to an axial force due to difierential pressure between said first and said second chambers, said second end of said lever being in said second chamber of said casing, whereby variations in 1 the axial force on the second end of said lever will cause variations in the force output of said first end of said lever, and

means for supplying pressure to said first chamber as a first function of engine speed and to said second 1 chamber as a second function of engine speed.

5. A volumetric efficiency control device adapted to provide a partial control over the output of a pneumatically controlled fuel injection pump in an internal combustion engine, wherein the pneumatic control includes a 2 pressure responsive element responsive to engine manifold pressure for controlling the fuel pump, comprising:

a pivotally mounted lever having a first end in contact with the pneumatic control of said pump whereby variations in the force applied by said first end of 2 said lever to said pneumatic control will cause a variation in the said output of said pump,

a piston in contact with the second end of said lever and mounted in a casing thereby dividing said casmeans for maintaining pressure in said second chamber constant while increasing pressure in said first chamber as engine speed increases until an engine speed is reached corresponding to the peak of the volumetric efficiency curve, and

means for maintaining pressure in said first chamber constant While increasing pressure in said second chamber as engine speed increases past said engine speed that corresponds to the peak of the volumetric eificiency curve.

References Cited in the file of this patent UNITED STATES PATENTS 2,623,509 Gold et al Dec. 30, 1952 2,876,755 Gold et al Mar. 10, 1959 2,880,714 Clark Apr. 7, 1959 2,882,880 Reggio Apr. 21, 1959 2,899,948 Groves Aug. 18, 1959 2,921,569 Gold et a1. Jan. 19, 1960 2,926,646 Prentiss Mar. 1, 1960

Claims (1)

1. A VOLUMETRIC EFFICIENCY CONTROL DEVICE ADAPTED TO PROVIDE A PARTIAL CONTROL OVER THE OUTPUT OF A PNEUMATICALLY CONTROLLED FUEL INJECTION JUMP IN AN INTERNAL COMBUSTION ENGINE, WHEREIN THE PNEUMATIC CONTROL INCLUDES A PRESSURE RESPONSIVE ELEMENT RESPONSIVE TO ENERGIZE MANIFOLD PRESSURE FOR CONTROLLING THE FUEL PUMP, COMPRISING: A PIVOTALLY MOUNTED LEVER HAVING ITS FIRST END IN CONTACT WITH SAID PNEUMATIC CONTROL DEVICE WHEREBY VARIATIONS IN THE POSITION OF SAID FIRST END OF SAID LEVER WILL CAUSE SAID PNEUMATIC CONTROL DEVICE TO VARY THE OUTPUT OF SAID PUMP, A PISTON IN CONTACT WITH SAID SECOND END OF SAID LEVER AND MOUNTED IN A CASING THEREBY DIVIDING SAID CASING INTO A FIRST CHAMBER AND A SECOND CHAMBER, SAID SECOND END OF SAID LEVER BEING IN SAID SECOND CHAMBER OF SAID CASING, WHEREBY VARIATIONS IN THE AXIAL POSITION OF SAID PISTON WILL CAUSE SAID LEVER TO ROTATE ABOUT ITS PIVOT POINT AND THEREBY VARY THE POSITION OF SAID FIRST END OF SAID LEVER, A SUBSTANTIALLY CONSTANT PRESSURE SOURCE OF FLUID, A SECONDARY PUMP HAVING ITS INPUT CONNECTED TO SAID SOURCE OF FLUID, SAID SECONDARY PUMP BEING RUN OFF SAID ENGINE SO THAT THE RATE OF SAID FLUID PUMPED BY SAID PUMP IS A FUNCTION OF ENGINE SPEED, A MAIN FLUID PRESSURE LINE CONNECTED TO THE OUTPUT OF SAID PUMP, A FIRST SUBSIDIARY FLUID LINE CONNECTING SAID FIRST CHAMBER OF SAID CASING TO SAID MAIN FLUID PRESSURE LINE DOWNSTREAM FROM THE OUTPUT OF SAID PUMP, A SECOND SUBSIDIARY FLUID LINE CONNECTING SAID SECOND CHAMBER OF SAID CASING TO SAID MAIN FLUID PRESSURE LINE DOWNSTREAM OF THE MAIN FLUID LINE CONNECTION TO SAID FIRST SUBSIDIARY FLUID LINE, AND A NORMALLY CLOSED RELIEF VALVE IN SAID SECOND SUBSIDIARY LINE, SAID RELIEF VALVE OPENING AT A PRE-DETERMINED PRESSURE TO ADMIT FLUID FROM SAID MAIN LINE TO SAID SECOND CHAMBER WHEN MAIN LINE PRESSURE IS ABOVE SAID PRE-DETERMINED VALVE.

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