US3539159A - Flow rate-responsive fuel mixture control device - Google Patents

Description

I United States Patent 1 1 3,539,159

[72] Inventors Dieter Handtmann [56] References Cited geriingglg; s n K d UNITED STATES PATENTS 1 565,972 12/1925 Stewart 26i/44X 21 A l N Egim Cannsta Germ 2,939,776 6/1960 McClain 26l/50(.1)X 1 P 2,988,345 6/196] Kolbe et al.... 26l/50(.1)X [221 PM Sew-11,1968 3,016,889 1/1962 Sweeney 26l/50(.l)X [45] Patented Nov. 10,1970 3,284,062 11/1966 Obermeyer... 26l/50(.l)X I731 AS81811 3,307,837 3/1967 Winkler 26l/50(.l)X smtgmrcermmy 3,329,413 7/1967 Date 26l/50(.l)X Pmmy 222 22 3,348,824 10/1967 Soubis 26l/5lX 5 7 2 75 Primary Examiner-Tim R. Miles Attorney-Edwin E. Greigg ABSTRACT: In a fuel injection system the metering of the fuel is controlled by a three-dimensional cam which is angu- [54] FLOW RATE'RESPONSWE FUEL MIXTURE larly displaced in unison with the arbitrary setting of a but- CONTROL DEVICE terfly valve regulating the airflow and is linearly displaced by a 13 claimssnmwingmgs linearly movable element of a pressure-responsive control [52] 0.8. CI 261/50, member. The said element is arranged in the air suction tube 261/51 of the fuel injection system and is caused to be linearly shifted [51] Int. Cl F02m 9/06 dependent upon the air pressure conditions in a flow passage, [50 Field of Search 26 1/50. 1 the cross-sectional area of which is varied due to the linear dis- 1 44 51 l f 'd l p acemento sa1 e ement.

Patented. Nov. 10, 1970 l 3,539,159

' Sh eet or a I JNVENTORS Dieter HANDTMANN Gerhard ST UMPP 3 3G Konrad ECKERT theirATTORNEY Patented Nov. 10, 1970 3,539,159

Sheet 2 or s n W: 0 I 8 "I: 8 8 R, R. w w 1 9 f 2% Q 9; Q F! Hb /%h [I f'wi i 3i%! rv .Q g Q/ 8 c g m v g C) LT. 1 I m l\ l 8 61 g m Q. INVENTORS Dieter HANDTMANN \1- a Gerhard STUMPP Konrad ECKERT m theirATTORNEY Patented Nov. 10, 1970 3,539,159

Sheet 3 of 3 i X 8 0 E I l/l INVENTORS Dieter HANDTMANN Gerhard STUMPP B Konrad ECKERT their ATTORNEY FLOW RATE-RESPONSIVE FUEL MIXTURE CONTROL DEVICE BACKGROUNDOF THE INVENTION AND PRIOR ART The invention relates to fuel injection systems for internal combustion engines, particularly for automotive vehicles, operating onindependently ignited fuel, wherein the air supply is controlled by the arbitrary actuation of a throttle valve disposed in the air suction tube.

In fuel injection systems of the aforenoted type, the butterfly valve is, as known, set according to the required power output and it is the function of a control device to meter the fuel so that always the best mixture ratio (fuel/air ratio) is obtained.

In known fuel injection systems of this type, the metering of the fuel is based on the rate of airflow in the suction tube. Such a system is described in British Pat. No. 1,066,721. Since it is not sufficient to set a constant fueI-to-air ratio, the latter is corrected, depending upon operating conditions, by means of additional devices. For example, the proportion of fuel is increased in the mixture while the engine'operates under heavy loads. In known fuel injection systems the control of the fuel/air ratio is effected:

a. by means 'of a pressure-responsive control member which automatically controls the effective cross-sectional area of an adjustable flow passage in the suction tube; said passage is arranged upstream of the throttle valve and serves, at the same time, to control the effective crosssectional area of a fuel metering nozzle functioning as an adjustable throttle; and b. by means of a pressure control device which maintains at a constant value the fuel pressure difference under constant rpm. and load conditions at the metering nozzle, but which, however, at the same time corrects this pressure difference according to the changes in air pressure in the suction tube portion between the pressure-responsive control member and the throttle valve.

Such a fuel injection system has the disadvantage that the fitting of the fuel-air curve to the engine characteristic is not point by point, but, because of the aforenoted pressure control means, follows in such-a manner that the metered fuel quantity is at its optimal value at some levels of operation, but in wide operating ranges does not correspond satisfactorily to the required quantity. l

In another known fuel injection system pertaining to the aforedescribed type, there is provided a device in which a second throttle member controls a pneumatic servomotor with which there is associated a fuel metering valve 'which, in turn, determines the fuel/air ratio as a function of the pressure prevailing in the suction tube between the throttle valve and i the second throttle member. The second throttle member is disposed in the suction tube upstream of the first throttle member (throttle valve) and is actuated in an opening direction by means of the low pressure prevailing between the throttle members and the pressure prevailing before the second throttle member. A device of the aforenoted structure is disclosed in German Pat. No. 1,l9l,l77. The previously discussed disadvantage also applies to this device.

German Pat. No. 896,867 describes a mixture control device wherein a three-dimensional cam attached to the adjusting rod of the fuel pump is displaceable as a function of the pressure in the suction tube downstream of the throttle member and dependent of the position thereof. The member responsive to the pressure prevailing in the suctiontube, how ever, is disposed externally thereof and, in addition, is acted upon exclusively by the static pressure. Consequently, the rate of airflow is only-imperfectly sensed. This is adequate since the r.p.m.*dependent variation of the fuel quantities is cffccted by a highly expensive fuel injection pump.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to provide an improved fuel injection system which, at each operational level of the internal combustion engine under the most efficient operating conditions (i.e. the smallest possible fuel consumption), meters the fuel quantity in such an accurate manner that the fuel in the engine may be almost completely combusted so that the composition of the exhaust gases satisfies the requirements relating to the nontoxic nature of the components.

The invention is based on the recognition that at each operating level of the internal combustion engine the fuel quantity, depending upon requirements, has to be very accurately metered. v I

Briefly stated, in order to achieve the aforenoted object, the air, streaming in an unmixed condition in the suction tube, flows past a control member which is at least partially disposed and displaceably held within the suction tube and is exposed to both the total and the static pressure prevailing in the suction tube. The control member, which is thus exposed the cross-sectional area of a flow passage in the suction tube dependent upon the changes in the rate of the airflow. The position of the control member is thus a measure for the rate of airflow; the fuel quantity is metered continuously and under constant pressure gradient by means of the pressure-responsive control member.

According to the invention, with the pressure-responsive control member, which is at least partially disposed in the suction tube, there is connected in a manner known per se, a long itudinally displaceable three-dimensional camwhich is, in addition, rotatable through an angle dependent upon the desired engine output which, together with the rate of airflow, described the full performance characteristic of the internal combustion engine. Thus, for example, the said cam may be rotated as a function of the pressure in the suction tube downstream of the throttle member and the pressure-responsive control member. Preferably, however, the said cam is turned dependent upon the position of the throttle member,

by means of a linkage assembly provided therebetween. In either case the cam is operatively connected to a follower pin which, in turn, is associated with a fuel metering device.

7 The invention will be better understood and further objects as well as advantages will become more apparent from the ensuing detailed speciflcation of three exemplary embodiments 7 taken in conjunction with the drawings.

BRIEF DESCRIPTION OF TI'IE DRAWINGS FIG. 4 is a partial view in section taken along line lV-IV of FIG. 3; and

FIG. 5 is an axial sectional view of a third embodiment of the invention. I

DESCRIPTION OF A FIRST EMBODIMENT Turning now to the fuel injection system shown in FIG. 1, the air necessary for-the combustion flows in the suction tube 1 in the directionof the arrow past a pressure-responsive control member generally indicated at 2 and an arbitrarily operated butterfly valve 3, to one or more cylinders of an internal combustion enginc'(not shown). The preferred location of the butterfly valve 3 is upstream of the control member 2 as shown in FIG. I; it is conceivable, however, to dispose the valve 3 downstream of member 2.

The fuel, withdrawn from a tank 4 through a filter 5 by means of a pump 6, flows past a return conduit 7 provided with a relief valve 8 and is introduced under constant pressure into a fuel metering device 9 shown only schematically. Therefrom a fuel line 10 leads to one or several nozzles 11 from which the fuel is injected into the suction tube preferably shortly before the cylinder or cylinders of the internal combustion engine.

The pressure-responsive control member 2 comprises a stepped piston 12, the terminal portion 12a of which extends into the suction tube 1. Piston 12, which is movably held in a housing 13 secured to the suction tube 1 externally thereof, is rotatable about its own axis and is axially slidable normal to the axis of the suction tube 1.

The piston 12 and the housing 13 define chambers 14 and 15. The chamber 14 communicates with the suction tube 1 upstream of the control member 2 by means of a tube 14a, the open and flared'end portion of which is directed against the airflow. Thus, in the chamber 14 the total air pressure prevails, to which there is exposed an annular shoulder 12]; of piston 12.

The chamber 15 communicates with the suction tube 1 by means of a port 15a that extends coaxially with piston 12 normal to the airflow in suction tube 1 and ends on the terminal face 12a of piston 12. Communication between port 15a and chamber 15 is established by means of openings 15a provided in port 15a. Thus, the pressure in chamber 15 is identical to the static pressure prevailing in the passage 16 of the suction tube 1. The pressure in chamber 15 is applied to the internal annular surfaces 12c, 12c and 12c" of the piston 12. Coaxially with the piston 12 there is arranged a weak compression spring 17, one end of which engages an internal wall of housing 13, while the other end of which rests against an annular inner surface 120' of piston 12. Spring 17, together with the aforedeseribcd static pressure urges the piston 12 into the suction tube 1 in a direction of reducing the cross-sectional area of flow passage 16 which is defined by the terminal portion 12a of piston 12 and an elevated portion 18 forming part of suction tube 1 opposite the central opening of port 15a in the terminal face 12a.

A push rod 19 fixedly secured at one end to piston 12 and including the aforeclescribed port 15a carries at its end remote from the piston a three-dimensional cam 20 which is contacted by a follower pin 9a associated with the fuel metering device 9. Cam 20 has a camming face both in an axial and in a circumferential direction so that follower pin 9a may be displaced due to either a linear displacement or a rotation (or both) of cam 20. The push rod 19 is connected by means of a lever and linkage assembly 21, 21a and 21b with the shaft 3a to which there is secured the butterfly valve 3 and which may be rotated at will by means of a lever arm 22. Thus, when the butterfly valve 3 is actuated by means of lever arm 22, the rotary motion is transmitted to the cam 20. The lever 21b is secured to push rod 19 by means of a carrier pin 23 extending into a longitudinal'groove 190 provided in the push rod 19. This mounting means allows a relative sliding motion, but prevents a relative rotation of the lever 21b with respect to push rod 19.

The position 'of the butterfly valve 3 in suction tube 1 depicted in FIG. 1 is more clearly shown in FIG. 2.

DESCRIPT'ON OF A SECOND EMBODIMENT Turning now to FIG. 3, the pressure-responsive control member generally indicated at 2' comprises a hollow cylinder 24 disposed coaxially within a two-part suction tube 1'. The upstream end of thecylinder 24 is closed by means of a cap 24a of a streamlined configuration. This upstream portion of the cylinder 24 extends into a funnel-shaped section la of the suction tube 1; The cylinder 24 is axially slidably and rotatably held on a guide tube 26 closed off at its downstream end by means of a plug 25. The guide tube 26 is fixedly mounted within suction tube 1 coaxially therewith by pressfitting it into a sleeve 27 affixed to the internal wall of suction tube 1 by means of radial webs 27a.

The hollow cylinder 24 has an axial bore 28 slidably surrounding, with a snug fit, the guide tube 26 and a larger axial bore 280 which is slidably engaged in a snug fit by a collar 29 keyed to the guide tube 26.

The extent of axial displacement of the hollow cylinder 24 is limited on the one hand by the terminal face 29a of the collar 29 and on the other hand by the terminal face 27b of the sleeve 27. The external surface of the upstream portion of cylinder 24 and the funnel-shaped internal wall of suction tube portion 1a defines an airflow passage 30. If the hollow cylinder 24 is in its upstream extreme position (shown in dotted lines in H6. 3) in the funnel-shaped suction tube portion la, the cross-sectional area of the air passage 30 is the smallest. lf, on the other hand, the hollow cylinder 24 is in its downstream extreme position (as shown in solid lines in FIG. 3), the cross-sectional area of the air passage 30 is at its maximum.

The wall of the cylinder 24 is provided at its upstream end (where, at any position of cylinder 24, the cross-sectional area of the flow passage 30 is the smallest) with openings 31 which establish communication between the suction tube and the inside of the cylinder, thus ensuring that the static pressure of the airflow in flow passage 30 also prevails in the inside of the cylinder 24. The static pressure within the cylinder 24 exerts a force on the inner face of the cap 24a, while the outer face thereof is exposed to the total pressure of the airflow.

In the guide tube 26 there is disposed a weak compression spring 32, one end of which is seated against the plug 25 fixedly inserted into the guide tube 26, and the other end of which engages a spring seat disc 33 secured to the cylinder 24 by means of a snap ring 34. The spring 32, together with the static pressure, tends to move the cylinder 24 against the downstream directed force of the total air pressure.

Bore 28, guide tube 26 and terminal face 29a define a dashpot chamber 281) provided with a bleeding orifice 35. This arrangement ensures that axial oscillating motions of the cylinder 24 are strongly dampened. One portion of the outer wall of the cylinder 24 is formed as a three-dimensional cam 36 which is in contact with the follower pin 9a associated with the fuel metering device 9.

The cylinder 24 is provided with a longitudinal groove 37 into which extends the carrier pin 38a ofa lever 38 secured to a shaft 39 which, in turn, is rotatably held in the suction tube 1'. Externally of the suction tube 1 the shaft 39 is secured to a lever 40 which is connected to the throttle valve 3 by means of a link 41 jointed to a lever 43 which, in turn, is fixedly secured to throttle valve shaft 42. By virtue of this linkage assembly the rotational movement of butterfly valve 3, initiated by an arbitrary external force applied to lever 22, is transmitted to the cam 36.

in the embodiment shown in FIG. 3, the butterfly valve 3 is I disposed upstream of the pressure-responsive control member The position of the butterfly valve 3 in suction tube 1 depicted in FIG. 3 is more clearly shown in PK}. 4.

DESCRlPTlON OF A THIRD EMBODIMENT In the embodiment shown in FIG. 5, the butterfly valve 3' is disposed in a narrow suction tube section lb" of the two-part suction tube 1" downstream of the pressure-responsive control member generally indicated at 2".

To the hollow cylinder 24' which rotatably and slidably ex tends into the funnel-shaped suction tube section 1a, there is fixedly secured a sleeve 44 which carries a three-dimensional cam 36 contacted by a follower pin 9a and a longitudinal groove 37 into which extends a carrier pin 38a of the lever 38.

The hollow cylinder 24 has an axial bore 28 slidably surrounding, with a snug fit, the guide tube 26' and a larger axial bore 28a which is slidably engaged in a snug fit by a collar 29' keyed to the guide tube 26. The terminal face 29a of collar 29' serves as an abutment face. The guide tube 26' is closed at collar 29 by a stud 45.

Within the guide tube 26' there is disposed a tension spring 32', one end of, which is attached to the end wall of stud 45 while its other end is hooked to a transversal pin 46 fixedly secured at both ends to the cylinder 24 and extending through longitudinal slots 47 of the guide tube 26. The length of the slots 47 provided in the guide tube 26 at diametrically opposed locations determines the extent of possible displacement of the cylinder '24. An advantage in the use of a tension spring resides in the reduction of friction.

It is seen that the structure and arrangement of the embodiment shown in FIG. 5 is generally similar to the embodiment described earlier and illustrated in FIG. 3. The coaxial arrangement of the pressure-responsive control member in the suction tube in accordance with the second (FIG. 3) and third (FIG. 5) embodiment has the advantage that the entire upstream terminal face (the external surface of cap 24a of the linearly displaceable element (cylinder 24, 24') is exposed to the total pressure of airflow; the dimensions of the control member are smaller and, consequently, the forces due to inertia are also reduced. Further, by virtue .of the streamlined structure, the eddy losses are very small which results in a higher efficiency of the engine. Further, in a coaxial arrangement. the pressurecomponents normal to the axis-of the pressure-responsive control member are compensated resulting in reduced frictional forces. Also, by disposing the pressureresponsive control member within the suction tube, longer air tubes and conduits which have a delaying effect, may be omitted.

OPERATION OF THE EMBODIMENTS munication between the flow passage and the inside of piston 12 or, respectively, the cylinder 24, 24', the static pressure therein also drops. Thus, the changed difference between the mutually counteracting forces of total pressure and static pressure causes, against the force of spring 17, 32, 32', displacement of piston 12, or respectively, of cylinder 24, 24 in the opening direction with respect to flow passage 16, 30. This displacement and, consequently, the widening of the crosssectional area of flow passage 16, 30 is in progress until the said crosssectional area reaches an enlarged dimension whereby the air velocity and thus the static pressure reach approximately their initial value. In case of decreasing the flow rate in the suctiontube, this process is reversed.

It is seen from the foregoing that the linear setting of the pressure- responsive control member 2, 2', 2" is determined by the dynamic pressure (total pressure less static pressure), the variation of which is an accurate measure of the change in the flow rate. Thus, the linear displacement of cam 20, 36is a function of the rate of airflow, while the angular displacement thereof is, due to an interconnectinglinkage assembly, effected in unison with the arbitrary setting of butterfly valve 3. Thus, the fuel is metered by means of follower pin 9a as a function of two variables: the rate of airflow and the position of the butterfly valve.

The advantages achieved by the invention reside particularly in the fact that by virtue of combining the pressureresponsive control member with a three-dimensional cam adjusted to the engine characteristic, the fuel may be metered in a very accurate manner so that even in the various ranges of operation (full load, or partial load) a desired mixture ratio (rich or lean) may be set.

As seen, the'pressure-responsive control member may be arranged either upstream or downstream of the butterfly valve. The latter arrangement is preferred, since it has the advantage that an exact metering of the fuel is possible even during the transitional period before the engine is being driven by the car and further when the engine is driven by the car, even a stoppage of fuel is possible. Also, in the range of small throttle valve openings of the butterfly valve, a larger portion of the cam face is affected which is important to ensure an accuracy in the metering. Furthermore, the suction tube does not have to be narrowed downstream of the pressure-responsive control member as in the embodiment shown in FIG. 5.

variable with the linear displacement of said hollow cylinder We claim:

1. In a fuel, injection system including a suction pipe provided with a throttle valve for the arbitrary variation of the flow of air to control the fuel-air mixture to be injected for combustion particularly in externally ignited internal combustion engines, a pressure-responsive control member associated with said suction tube and exposed to said flow of air therein, a fuel metering device responsive to both said control member and said arbitrary variation of said throttle valve, the

improvement comprising in combination:

A. a linearly slidable element fdrming part of said pressureresponsive control member and disposed at least partially in said suction tube, one part of said slidable element defining, together with a portion of said suction tube, a flow passage havingv a cross-sectional area variable with the linear displacement of said slidable element, said element adapted to be urged by the total pressure of said airflow in a direction of widening said cross-sectional area, said element adapted to be urged by the static pressure of said airflow in said flow passage in a direction of narrowing said cross-sectional area;

B. a slidable and rotatable three-dimensional cam attached to said element to be at least slidably displaced therewith;

C. means responsive to said arbitrary variation of the flow of air to rotate said cam'; and v D. cam follower means forming part of said fuel metering device and. responsive to both said linear displacement and rotational movement of said cam.

2. The improvement as defined in claim 1, wherein said slidable member is disposed downstream of said throttle valve.

3. The improvement as defined in claim 1, wherein said slidable member is hollow and includes at least one port establishingcommunication between said flow passage and the inside of said slidable element to cause the static pressure in said flow passage to prevail also in the inside of saidslidable element. I

4. The improvement as defined in claim 3, wherein said slidable element is a piston disposed in a housing externally of said suction tube and extending thereinto linearly displaceably normal to the airflow, one side of said piston is exposed in said housing to said static pressure, the other side of said piston is exposed in said housing to said total pressure.

5. The improvement as defined in claim 4, wherein said static pressure is communicated with the inside of said piston and said housing by means ofa port extending from a terminal face of said piston thcrcinto normal to the airflow in said flow passage, and said total pressure is communicated with the inside of said housing by means of a tube, the opening of which within said suction tube is directed against said airflow.

6. The improvement as defined in claim 3, wherein said slidable element is contained entirely within said suction tube and is disposed coaxially slidably therewith.

7. The improvement as defined in claim 6, wherein said slidable element is a hollow cylinder, the upstream portion of which, together with a funnel-shaped portion of said suction tube, defines said flow passage having a cross-sectional area coaxially with said suction tube, said hollowcylinder has an upstream, closed terminal face exposed to the total pressure of said airflow urging said cylinder in a direction of widening said cross-sectional area.-

8. The improvement as defined in claim 7, wherein said hollow cylinder is mounted on a guide tube fixedly and coaxially held within said suction tube.

9. The improvement as defined in claim 8, including a spring disposed in, and with one end in engagement with said guide tube, the other end of said spring engages said hollow cylinder, said spring, together with the static pressure prevailing within said cylinder, urges said cylinder against said total pressure in adi-rection of narrowing said cross-sectional area of said flow passage.

10. The improvement as defined in claim 8, wherein one part of the outer wall of said guide tube and one part of the inner wall of said hollow cylinder form a dashpot chamber of variable volume to dampen axial vibrations of said cylinder.

13. The improvement as defined in claim 11, wherein said means responsive to said arbitrary variation of the flow of air includes a linkage mechanism interconnecting said throttle valve and said hollow cylinder to rotate the latter as said throttle valve is arbitrarily moved.

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