CA1078281A - Air-fuel ratio control apparatus for a fuel supply system of an internal combustion engine - Google Patents
Air-fuel ratio control apparatus for a fuel supply system of an internal combustion engineInfo
- Publication number
- CA1078281A CA1078281A CA309,895A CA309895A CA1078281A CA 1078281 A CA1078281 A CA 1078281A CA 309895 A CA309895 A CA 309895A CA 1078281 A CA1078281 A CA 1078281A
- Authority
- CA
- Canada
- Prior art keywords
- fuel
- air
- metering
- valve
- pressure
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000000446 fuel Substances 0.000 title claims abstract description 139
- 238000002485 combustion reaction Methods 0.000 title claims abstract description 9
- 230000002093 peripheral effect Effects 0.000 claims abstract description 10
- 230000007246 mechanism Effects 0.000 claims abstract description 9
- 238000011144 upstream manufacturing Methods 0.000 claims description 5
- 230000004044 response Effects 0.000 claims description 4
- 238000002347 injection Methods 0.000 abstract description 2
- 239000007924 injection Substances 0.000 abstract description 2
- 230000000875 corresponding effect Effects 0.000 description 7
- 230000008859 change Effects 0.000 description 5
- 230000007423 decrease Effects 0.000 description 5
- 238000006073 displacement reaction Methods 0.000 description 4
- 239000002828 fuel tank Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000006870 function Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M69/00—Low-pressure fuel-injection apparatus ; Apparatus with both continuous and intermittent injection; Apparatus injecting different types of fuel
- F02M69/16—Low-pressure fuel-injection apparatus ; Apparatus with both continuous and intermittent injection; Apparatus injecting different types of fuel characterised by means for metering continuous fuel flow to injectors or means for varying fuel pressure upstream of continuously or intermittently operated injectors
- F02M69/18—Low-pressure fuel-injection apparatus ; Apparatus with both continuous and intermittent injection; Apparatus injecting different types of fuel characterised by means for metering continuous fuel flow to injectors or means for varying fuel pressure upstream of continuously or intermittently operated injectors the means being metering valves throttling fuel passages to injectors or by-pass valves throttling overflow passages, the metering valves being actuated by a device responsive to the engine working parameters, e.g. engine load, speed, temperature or quantity of air
- F02M69/22—Low-pressure fuel-injection apparatus ; Apparatus with both continuous and intermittent injection; Apparatus injecting different types of fuel characterised by means for metering continuous fuel flow to injectors or means for varying fuel pressure upstream of continuously or intermittently operated injectors the means being metering valves throttling fuel passages to injectors or by-pass valves throttling overflow passages, the metering valves being actuated by a device responsive to the engine working parameters, e.g. engine load, speed, temperature or quantity of air the device comprising a member movably mounted in the air intake conduit and displaced according to the quantity of air admitted to the engine
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Control Of Throttle Valves Provided In The Intake System Or In The Exhaust System (AREA)
- Fuel-Injection Apparatus (AREA)
- Control Of The Air-Fuel Ratio Of Carburetors (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An air-fuel control apparatus for an injection type internal combustion engine has an air valve of butterfly type disposed in an engine intake passage up-stream of a throttle valve to define therewith an air pressure chamber and automatically operated to maintain the air pressure in the air pressure chamber substantially constant. A fuel supply circuit includes an injector at the downstream end thereof and a fuel-metering orifice between the injector and a fuel source. The fuel-metering orifice is defined by an opening in a peripheral wall of a cylinder and a fuel-metering rod slidably received in the cylinder to vary the fuel-flowing sectional area of the orifice. The air valve is operatively connected to the fuel-metering rod by means of a link mechanism such that the rotational motion of the air valve is converted into a linear motion of the fuel-metering rod. The fuel-metering orifice formed by the cylinder and the linearly movable fuel-metering rod can be more precisely and in-expensively manufactured as compared with a fuel-metering orifice formed by relatively rotatable members and, in addition, operative to more accurately meter the fuel.
An air-fuel control apparatus for an injection type internal combustion engine has an air valve of butterfly type disposed in an engine intake passage up-stream of a throttle valve to define therewith an air pressure chamber and automatically operated to maintain the air pressure in the air pressure chamber substantially constant. A fuel supply circuit includes an injector at the downstream end thereof and a fuel-metering orifice between the injector and a fuel source. The fuel-metering orifice is defined by an opening in a peripheral wall of a cylinder and a fuel-metering rod slidably received in the cylinder to vary the fuel-flowing sectional area of the orifice. The air valve is operatively connected to the fuel-metering rod by means of a link mechanism such that the rotational motion of the air valve is converted into a linear motion of the fuel-metering rod. The fuel-metering orifice formed by the cylinder and the linearly movable fuel-metering rod can be more precisely and in-expensively manufactured as compared with a fuel-metering orifice formed by relatively rotatable members and, in addition, operative to more accurately meter the fuel.
Description
~(~7l~
FIE~D OF THE INVENTION
The present invention relates to an air-fuel ratio control apparatus for a fuel supply system of a fuel injection type internal combustion engine.
DES~RIPTION OF THE PRIOR ART
There has been knowm an air-fuel ratio control apparatus which comprises an air valve disposed in an intake passage of an associated internal combustion engine upstream of a throttle valve to cooperate therewith to define an air pressure ohamber, pressure control means operative in response to variation in the air pressure in the air pressure chamber to control the degree of opening of the air valve thereby to maintain the pressure difference across the air valve substantially constant, a fuel supply circuit including an injector at the dowm-stream end thereof for injecting the fuel into the intake passage, and fuel metering means including a variable fuel-metering orifice means provided in the fuel supply circuit and having a fuel-flowing sectional area variable in dependence on the variation in the degree of opening of the air ~alve and a differential fuel pressure means normally to maintain the fuel pressure difference across the variable fuel-metering orifice means substantially constant. The kno~m apparatus is disclosed in Japanese Pre-Examination Publications Nos. 48-83220 (83220/73) and 52-3925 (3925/77), for example.
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~ 10~81 ` l Of the air-fuel ratio control apparatus of the type specified above, the apparatus to which the present invention is directed is of a so-called butterfly type in which the air valve is formed by a plate rotatable about an axis extending transversely of the flow of the air through the intake passage into engine cylinders.
As is known in the art, the air-fuel ratio of - an air-fuel mixture to be fed into an engine is related to the ratio of the air-flowing opening area of the air valve (i.e., the cross-sectional area of air passage defined between the inner peripheral wall of the intake passage and the outer peripheral edge of the air valve) to the fuel-flowing opening area of the variable fuel-metering orifice (i.e., the cross-sectional area of the variable fuel-metering orifice). In the air-fuel ratio control apparatus of the class to which the present inven-tion belongs, since the plate forming the air valve is rotated about an axis extending transversely of the flow of the air through the intake passage, the air-flowing opening area of the air valve is not in proportion to the angle of rotation of the air valve plate. For this reason, . it has been porposed in connection with the air-fuel ratio control apparatus having the air valve of the above-discussed type that the variable fuel-metering orifice means is formed by a stationary member and a rotary member rotatable rela-tive to the stationary member so as to make the opening area of the air valve proportional to the opening area of the fuel-metering orifice. However, such rotary type .
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. ~ ~ 1078281 1 fuel metering device has encountered difficulties in manufacturing the device at a low cost and with a reasonable precision. From the view point of cost of manufacture and attainable precision, it is advantageous that the variable fuel-metering orifice of the air-fuel ratio control apparatus is formed by a stationary member and a second member which is linearly movable relative to the stationary member.
SUMMARY OF ~HE INVENTION
An object of the present invention, therefore, is to make it possible, in an air-fuel ratio control apparatus of the type that is provided with an air valve in the form of a rotatable plate, to use a fuel-metering orifice which comprises a linearly movable fuel-metering member which can be easily, inexpensively and precisely machined and is capable of metering fuel with a high accuracy.
So as to achieve this object, the present in-vention provides an air-fuel ratio control apparatus of the class discussed above and in which the air valve is formed by a butterfly valve having a shaft. rotatable therewith and the variable fuel-metering orifice means includes a fuel-metering rod linearly movable to vary the fuel-flowing sectional area of the fuel-metering orifice means, and in which a link mechanism is provided between the shaft and the fuel-metering rod to translate the rotation of the shaft into a linear motion and to :
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, 1 transmit the linear motion to the fuel-metering rod, the link mechanism being arranged such that the fuel-flowing sectional area of the variable fuel-metering orifice means is varied in dependence on the variation in the F degree of opening of the air valve.
The l nk mechanism may preferably include a lever member secured to the shaft of the air valve, a pin mounted on the lever member and projecting therefrom, and a link member having one end portion engaged with the lC pin such that the rotational movement of the pin about the axis of the shaft is translated into the linear movement of the link member, the other end of the link member being connected to the fuel-metering rod.
The fuel metering means may further include a cylinder disposed in the fuel circuit in slidable engage-ment with the fuel-metering rod. Advantageously, the cylinder may have a fuel-flowing opening formed in the peripheral wall, while the fuel-metering rod may be formed therein with at least one slit cooperating with the fuel-flowing opening in the cylinder wall to define the variable fuel-metering orifice. Preferably, the fuel-flowing opening in the cylinder wall may constitute an outlet for the fuel. The fuel inlet may preferably be formed in the end wall of the cylinder opposite to the - 25 inner end of the fuel-metering rod.
- The pin may be positioned in a plane in which the butterfly valve lies. This positioning of the pin causes the opening area of the air valve to be substantially . . . . .
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~07~81 1 proportional to the displacement of the fuel-metering rod and thus to the opening area of the variable fuel-flowing orifice, with a result that the air-fuel ratio is kept always substantially constant. The pin may alter-natively be offset from the plane in which the butterflyvalve lies. With this alternative embodiment, the in-crease in the opening area of the air valve causes an increase in the opening area of the fuel-metering variable - orifice. The rate of the increase in the opening area of the fuel-metering variable orifice is in non-linear rela-tionship to the increase in the opening area of the air valve. This non~linear characteristic may be employed in combination with a proper angular positioning of the pin relative to the air valve to obtain an air-fuel control characteristic suited to a particular application of the associated internal combustion engine.
The above and other objects, features and advantages of the present invention will be made more apparent by the following desc-ription with reference to the accompanying drawings.
~RIEF DESCRIPTION OF THE DRAWIN~S
Fig. 1 is a partly sectional diagrammatic illustration of an embodiment of an air-fuel ratio control apparatus according to the present invention;
Fig. 2 schematically illustrates various angular positionings of a pin of the link mechanism relative to the plane in which an air valve lines;
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1 Fig. 3 graphically illustrates the air-fuel ratio control characteristics of the apparatus according to the present invention with the positions of the pin varied as shown in Fig. 2; and Fig. 4 graphically illustrates the air-fuel ratios obtainable from the apparatus according to the invention with the angle ~ being maintained 15 and with the angle ~1 of the pin relative to the plane of the air valve being varied.
Referr1ng to Fig. 1, reference numeral 10 indicates an intake passage provided upstream of an intake manifold 102 of an internal combustion engine (not shown). There are disposed in the intake passage 10 a conventional throttle valve 12 operated by an engine accelerator (not shown) to control the flow of air fed into the engine and an air valve 16 located upstream of the throttle valve l2 to cooperate therewith to define an air pressure chamber 14. Air is caused to flow from an air cleaner (not shown) in a direction indicated by an arrow A into the~intake passage 10 by intake vacuum produced in the engine. The air flows through the passage 10 past the air valve 16 into the air pressure chamber 14 and hence passes through the throttle 25 valve 12 into the intake manifold 102 as indicated by an arrow Al and thus into respective engine cylinders (not shown).
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107~'~81 The air valve 16 is formed by a butterfly valve having a shaft 18 which extends transversely of the axis of the intake passage 10 and is rotatably mounted on the peripheral wall of . the inta]ce passa~e 10. One end portion of the shaft 18 extends outwardly from the intake passage 10 and is connected to a link 22 extending from a pressure controller 20 which is so arranged and constructed as to rotate the air valve 16 through the link 22 and the shaft 18 in response to variation in the pressure in the air pressure chamber 14 thereby to control the degree of opening of the air valve 16 so that the pressure in the air pressure chamber 14 and hence the pressure difference across the air valve 16 is maintained substantially constant irrespec-tive of the variation in the intake air flow to the engine. Such a pressure controller itself is known to those skilled in the . art, as is disclosed in U.S. Patent No. 3,739,762, for example.
In the case of the illustrated embodiment of the present inven-tion, the pressure controller 20 may be the one disclosed in the U.S. patent referred to. In any case, the degree of the air valve opening is controlled by the pressure controller 20 such that the pressure in the air pressure chamber 14 remains sub-stantially constant. Consequently, the difference in pressure between the air pressure chamber 14 and the atmosphere, i.e., the pressure difference across ~' , ' ~ ' ' .
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1 the air valve 16, is also maintained substantially constant.
Thus, the intake air flow Ga is determined in dependence on the opening area of the air valve 16; that is, the cross-sectional area Aa of the passage defined between 5 the peripheral edge of the air valve 16 and the inner peripheral surface of the intake passage 10 (i.e., Ga is proportional to Aa).
A lever 24 is secured at one end thereof to the aforementioned projecting end portion of the shaft 18 of the air valve 16, while the other end of the lever 24 has a pin 26 secured thereto and projecting therefrom in the same direction as the shaft 18. A fuel metering means 30 is provided outside the intake passage 10 and includes a cylinder 32 accommodating a fuel-metering rod 15 34 for axial slidable movement therein. The rod 34 is connected at its outer end to the pin 26 through a link member 28. More specifically, the link member 28 has a slot 29 formed therein at an upper end portion thereof.
The pin 26 loosely extends through, or is loosely engaged with, the slot 29 in the link member 28 so that the rota-tional motion of the shaft 18 and hence the lever 24 together with the air valve 16 is translated into a linear movement of the fuel-metering rod 34 in the direc-tion indicated by an arrow B.
A fuel chamber 36 is defined by the cooperation of the inner end face of the fuel-metering rod 34 and the cylinder 32 and connected to a fuel tank 42 by a fuel supply line 40 provided with a fuel pump 38 therein.
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1078~1 1 A line 46 having a pressure relief valve 44 is branched from the fuel supply line 40 at a point downstream of the pump 46 so that the fuel supplied into the fuel chamber 36 is maintained at a constant pressure level higher than the atmospheric pressure by the cooperation of the pump 38 and the pressure relief valve 44.
An axial bore 34a is formed in the inner end portion of the fuel-metering rod 34. A pair of slits 34b are formed longitudinally in the peripheral wall of the bore 34_ in diametrically opposite relationship with each other. On the other hand, a circumferential groove 32a is formed in the inner peripheral surface of the cylinder 32 at a position substantially aligned with the inner end portions (left end portions as viewed in Fig. 1) of the slits 34a to cooperate with the slits 34b to define a variable fuel-metering orifice. The annular groove 32a is connected to a fuel passage 48 leading to a f`uel injector 50 which is of a known structure a~d has a fuel-discharge orifice open to the intake passage 10 downstream of the throttle valve 12.
In the illustrated embodiment of the invention, there is provided a differential fuel pressure means 52 in the fuel passage 48 between the injector 50 and the fuel metering means 30. The differential pressure means 52 has first and second fuel pressure chambers 56 and 58 partitioned by a diaphragm 54. The fuel metered by the fuel metering means 30 and flowing out of the cyl nder 32 enters the second fuel pressure chamber 58 through an - _ 9 _ .
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l inlet port 58a and flows to the injector 50 from an out-let port 58b. The outlet or exit port 58b is defined by a valve seat member 62 having an annular valve seat 60 disposed in opposite and close contacting relation-" 5 ship with the diaphragm 54. A coil spring 64 is disposed around the valve seat member 62 and resiliently urges the diaphragm 54 away from the valve seat 60. On the other hand, the first fuel pressure chamber 56 of the differential fuel pressure means 52 is supplied with a fuel pressure in the fuel feed passage 40 by way of abranch passage 66 having a fixed restriction 68 provided therein. A fuel return passage 70 is connected to the branch passage 66 downstream of the fixed restriction 68 and extends to the fuel tank 42. There is provided in the return passage 70 a pressure control valve 72 which is operative to vary the return of the fuel through the .; . .
passage 70 to the fuel tank 42 thereby to vary the pressure in the chamber 56. The pressure control valve 72 is formed by a variable restriction, the degree of the opening of which is varied in dependence on changes in an operation parameter of the engine (e.g. temperature of the engine).
; The differential fuel pressure means 52 func-tions to maintain a constant pressure difference across the variable fuel-metering orifice (32a, 3~b) during normal engine operation. More specifically, since the opening degree of the pressure control valve 72 is maintained constant during the ;10~nal engine operation, ` the pressure of fuel introduced into the first fuel -. ' - 10 -.
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1 pressure chamber 56 through the fixed restriction 68 from the fuel supply passage 40 is maintained constant by constant flow resistances (pressure loss) provided by the fixed restriction 68 and the pressure control valve 72. Consequently, the space between the diaphragm 54 and the valve seat 60 is increased as the pressure in the second fuel pressure chamber 58 is increased so that the flow resistance of the gap between the diaphragm 54 and the val~e seat 60 is reduced, and vice versa. Thus, the fuel pressure in the second fuel pressure chamber 58 is maintained at a level which is lower than that of the first fuel pressure chamber 56 by a constant value determined by the spring constant of the coil spring 64 irrespectively cf the quantity of fuel flowing out of the exit port 58b of the second fuel pressure chamber 58. On the ^ther hand, the fuel pressure in the fuel chamber 36 of the fuel metering means 30 is equal to that of the fuel supply passage 40 and higher than that of the pressure in the first fuel pressure chamber 56 by a predetermined constant value. Thus, the pressure difference across the variable fuel-metering orifice (32a, 34b) remains constant. The situation as brought about by variation in the opening degree of the pressure control valve 72 will be described hereinafter.
With the arrangement of the air-fuel ratio control apparatus described above, when the 1;hrottle valve 12 is rotated towards its full open position by the engine accelerator thereby to increase the rate of , ' ' ' .., .~
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1 intake air flow, the pressure in the air pressure chamber 14 will tend to be reduced. This tendency will be sensed by the pressure controller 20 which then actuates the link 22 to rotate the shaf~ 18 and thus the air valve 16 towards its open position so as to maintain the pressure in the air pressure chamber 14 constant. The rotation of the air valve 16 is transmitted to the fuel metering rod 34 through the shaft 18, lever 24, pin 26 and the link 28, resulting in the axial movement of the rod 34 to the left as viewed in Fig. 1. Consequently, the area of overlap of the slits 34a with the annular groove 32a, that is, the fuel-flowing sectional area of the variable fuel-metering orifice, is correspondingly increased. The flow of fuel through the fuel-metering orifice (32a, 34b) is determined by the flow sectional area thereof and the fuel pressure difference across the fuel metering orifice. Now, assuming that the engine is in the normal operation with the pressure difference across the fuel metering orifice (32a, 34b) being con-stant, the fuel flow through the fuel metering orificewill be proportional to the fuel-flowing sectional area thereof. Thus, it can be said that the fuel flow through the fuel-metering orifice (32_, 34b) will increase as the area Aa of the opening of the air valve 16 is in-creased. In this connection, it will be noted that thefuel-flowing area of the fuel-metering orifice (32a, 34b) is exactly proportional to the displacement x of the fuel-metering rod 34 in the direction indicated by an --- 1()78'~8~
1 arrow ~.
~or mathematical analysis, assuming that an angle formed between a plane P extending perpendicularly : to the axis of the intake passage 10 and containing the axis of the shaft 18 of the air valve 16 and a plane of the air valve 16 in its fully closed position shown by a broken line (this angle will be hereinafter referred to as "angle of fully closed position") is represented by 90, an angle between a plane containing the plate of the air valve 16 and a plane containing both the axes of the pin 26 and the shaft 18 is represented by ~1~ an angle of the air valve between its fully closed and partly opened positions is represented by ~, the radius of the pin 26 (the distance between the axes of the shaft : 15 18 and the pin 26) is represented by _, and the inner diameter of the intake passage 10 is represented by D, the following relations apply valid in the case where ; l~l equals to zero (0) (i.e., in an embodiment in which the axis of the pin 26 is disposed in the plane of the air valve 16):
Aa = ~ [cos 90 - cos ( ~o + ~ )~ .-- (1) x = r ~ccs ~o - cos ( ~o + ~)~ ................ (2) Hence, Aa = ~C D2 1 = constant ................ (3) x 4 cos ~o r ' ' - ': , ' .. : , . :: . :
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1 In the equation (3), the axial displacement x of the fuel-metering rod 34 is exactly proportional to the flow sectional area of the variable fuel-metering orifice (32a, 34b). Consequently, the air-fuel ratio represented by Aa/x in the above equation (3) remains constant (refer to Fig. 3).
As will be appreciated from the above dis-cussion, the air-fuel ratio remains always constant irrespective of variation in the flow of engine intake air in the case where ~1 = - Such operation characteristic is advantageous when applied to an internal combustion engine designed to be driven at a constant speed under a constant load. However, for the engines designed to be operated under the circumstances in which the rotational speed as well as the engine load undergo variations, such as engines installed on motor cars, it is preferred from the view point of drivability of this type of engines to control the air-fuel ratio such that the air fuel ratio is relatively small ~i.e., mixture is sl-ghtly enriched) during part-load, low speed operating range of the engine and such that the air-fuel ratio is matched with the power air-fuel ratio in the full-load operating range. To this end, the lever 24 may be secured to the shaft 18 so that 'he axis of the pin 26 is angularly offset from the plane of the air valve 16 by an angle ~ 1~ as shown by broken lines in Fig. 2. In the case of the embodiment shown in Fig. 1, the mounting of the lever 24 on the shaft 18 is such that the angle ~1 takes 1~78~Bl 1 a positive value.
In the case where the angle ~1 is selected to j be a value other than zero, the ratio of the displacement x of the fuel-metering rod 34 to the air-flowing area Aa of the air valve is not always constant in contrast to the case of the embodiment in which ~1 is selected to ~e equal to zero. When the angle ~1 is of a positive value, the ratio Aa/x will be increased as the area Aa of the air valve (and hence the degree ~ of opening of the air valve) is increased. In other words, the air-fuel ratio takes a relatively small value (i.e. the fuel is enriched) for a relatively small intake air flow, and becomes greater (i.e. mixture becomes leaner) as the intake air flow is increased, as is shown in Fig. 3. On the other hand, when the angle ~1 is selected to be a negative value, the ratio Aa/x becomes smaller as the opening degree ~ of the air valve is increased, with the result that the air-fuel ratio is large for a relatively small intake air flow and decreases as the latter is increased, as can also be seen in Fig. 3. ~y way of example, Fig. 4 graphically illustrates the rela-; tionships of the air-fuel ratio to various preset values of the angle ~1 with the angle ~o Of the fully closed position of the air valve 16 being set to be 15. In this figure, the rate of intake air is taken along the abscissa, while the air-fuel ratio is scaled along the ordinate. ~he curves (a), (b), (c), (d) and (e) represent the air-fuel ratios for the preset angles ~1 cf -3~
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107~Zf~l 1 -1, 0, 1 and 3, respectively. In this connection, it - should be mentioned that the position of the pin 26 and hence the ratio betwesn the radius r of the pin 26 and the inner dlameter D is changed in combination with the variation in the value of ~1 Accordingly, the curves (a), (b), (d) and (e) all lie below the straight line (c), indicating that the corresponding air-fuel ratios are smaller than the one obtained in the case where ~1 = (the straight line c). However, by changing the position of the pin 26, it is possible to obtain an operation characteristic that the curves (a), (b), (d) and (e) all lie above the line (c) to provide air-fuel ratios larger than that represented by the straight line (c). At any rate, the air-fuel ratio is decreased as the intake air flow is increased in the case where ~1 < ~
while the air-fuel ratio tends to be increased as the intake air flow increases in the case where ~1 >
When the opening degree of the pressure control valve 72 of the differential fuel pressure means 52 is varied in response to a change in the engine operation parameter, the fuel pressure in the first fuel pressure chamber 56 of the differential fuel pressure means 52 will undergo a corresponding variation, because the ratio between the flow resistances (pressure loss) pro-vided by the fixed restriction 68 and the pressure controlvalve 72 is changed. Since the fuel pressure in the second fuel pressure chamber 58 is maintained at a level lower than the pressure level in the first chamber ~(~7~3Z81 l 56 by a predetermined value, the pressure in the second fuel pressure chamber 58 will also undergo a corresponding change. For example, when the opening degree of the variable restriction or pressure control valve 72 is reduced, the fuel pressure in the first pressure chamber 56 will be increased, resulting in a corresponding increase in the pressure within the second fuel pressure chamber 58. On the contrary, the increase in the opening degree of the pressure control valve 72 will result in the corresponding decrease in the pressure within the first fuel pressure chamber 56 and hence in the decrease in the pressure within the second fuel pressure chamber 58.
Variation in the fuel pressure within the second fuel pressure chamber 58 as a function of the opening degree of the pressure control valve 72 provided in the fuel return passage 70 in turn brings about a correspond-ing change in the fuel pressure in the passage 48 downstream of the fuel-metering variable orifice (32a, 34b) of the ~uel metering means 30. In contrast, the fuel pressure upstream of the fuel-metering orifice (32_, 34b), i.e., within the fuel chamber 36 in the cylinder 32, remains constant, as described hereinbefore. Consequently, z variation in the fuel pressure downstream of the variable fuel-metering orifice will result in a change in the pressure difference across the fuel-metering orifice and hence in the rate of fuel flow therethrough. More specifically, even when the fuel-flowing cross-sectional area of the variable fuel-metering orifice remains constant, , .. , . -:, , ' ' ' ' ' 107gZf~l 1 the reduction in the degree of opening of the pressure control valve 72 in the fuel return passage 70 will cause a decrease in the pressure difference across the fuel-metering orifice with a resultant decrease in the fuel supply to the injector 50. On the contrary, an increase - in the degree of opening of the pressure control valve 72 will cause a corresponding increase in the pressure difference across the variable fuel-metering orifice (32a, 34b) and hence in the fuel flow to the injector 50. In this manner, the air-fuel ratio is corrected in dependence on variation in the engine operation para-meter by virtue of variation in the fuel flow through f the variable fuei-metering orifice of the fuel metering means 30.
As will be appreciated from the foregoing description of the preferred embodiments of the invention, the rotational movement of the air valve 16 ln the intake passage 10 is translated into a linear movement of the fuel-metering rod 34 through the link mechanism (24, 26 and 28) to meter and adjust the supply of the fuel into the engine. ~his enables the variable fuel-metering orifice (32a, 34_) of the fuel metering means to be manu-factured at a reduced cost and with a high precision.
Further, the angle ~1 cf the pin 26 relative to the plane of the air valve 16 may be set at an appro-priate value in consideration of the situation in which the engine to be equipped with the air-fuel ratio control apparatus of the invention is operated so that smooth and - 18 ~
1078~8~
1 continuous variation in the air-fuel ratio demanded by the engine is assured at a transition between different operating conditions of the engine, such as from idle or low-load operation to a part-load or full-load opera-tion. In addition, change in the coefficient of fuelflow rate in dependence on the opening degree of the air valve 16 can advantageously be corrected.
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FIE~D OF THE INVENTION
The present invention relates to an air-fuel ratio control apparatus for a fuel supply system of a fuel injection type internal combustion engine.
DES~RIPTION OF THE PRIOR ART
There has been knowm an air-fuel ratio control apparatus which comprises an air valve disposed in an intake passage of an associated internal combustion engine upstream of a throttle valve to cooperate therewith to define an air pressure ohamber, pressure control means operative in response to variation in the air pressure in the air pressure chamber to control the degree of opening of the air valve thereby to maintain the pressure difference across the air valve substantially constant, a fuel supply circuit including an injector at the dowm-stream end thereof for injecting the fuel into the intake passage, and fuel metering means including a variable fuel-metering orifice means provided in the fuel supply circuit and having a fuel-flowing sectional area variable in dependence on the variation in the degree of opening of the air ~alve and a differential fuel pressure means normally to maintain the fuel pressure difference across the variable fuel-metering orifice means substantially constant. The kno~m apparatus is disclosed in Japanese Pre-Examination Publications Nos. 48-83220 (83220/73) and 52-3925 (3925/77), for example.
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~ 10~81 ` l Of the air-fuel ratio control apparatus of the type specified above, the apparatus to which the present invention is directed is of a so-called butterfly type in which the air valve is formed by a plate rotatable about an axis extending transversely of the flow of the air through the intake passage into engine cylinders.
As is known in the art, the air-fuel ratio of - an air-fuel mixture to be fed into an engine is related to the ratio of the air-flowing opening area of the air valve (i.e., the cross-sectional area of air passage defined between the inner peripheral wall of the intake passage and the outer peripheral edge of the air valve) to the fuel-flowing opening area of the variable fuel-metering orifice (i.e., the cross-sectional area of the variable fuel-metering orifice). In the air-fuel ratio control apparatus of the class to which the present inven-tion belongs, since the plate forming the air valve is rotated about an axis extending transversely of the flow of the air through the intake passage, the air-flowing opening area of the air valve is not in proportion to the angle of rotation of the air valve plate. For this reason, . it has been porposed in connection with the air-fuel ratio control apparatus having the air valve of the above-discussed type that the variable fuel-metering orifice means is formed by a stationary member and a rotary member rotatable rela-tive to the stationary member so as to make the opening area of the air valve proportional to the opening area of the fuel-metering orifice. However, such rotary type .
.
.
. ~ ~ 1078281 1 fuel metering device has encountered difficulties in manufacturing the device at a low cost and with a reasonable precision. From the view point of cost of manufacture and attainable precision, it is advantageous that the variable fuel-metering orifice of the air-fuel ratio control apparatus is formed by a stationary member and a second member which is linearly movable relative to the stationary member.
SUMMARY OF ~HE INVENTION
An object of the present invention, therefore, is to make it possible, in an air-fuel ratio control apparatus of the type that is provided with an air valve in the form of a rotatable plate, to use a fuel-metering orifice which comprises a linearly movable fuel-metering member which can be easily, inexpensively and precisely machined and is capable of metering fuel with a high accuracy.
So as to achieve this object, the present in-vention provides an air-fuel ratio control apparatus of the class discussed above and in which the air valve is formed by a butterfly valve having a shaft. rotatable therewith and the variable fuel-metering orifice means includes a fuel-metering rod linearly movable to vary the fuel-flowing sectional area of the fuel-metering orifice means, and in which a link mechanism is provided between the shaft and the fuel-metering rod to translate the rotation of the shaft into a linear motion and to :
.
:.
, 1 transmit the linear motion to the fuel-metering rod, the link mechanism being arranged such that the fuel-flowing sectional area of the variable fuel-metering orifice means is varied in dependence on the variation in the F degree of opening of the air valve.
The l nk mechanism may preferably include a lever member secured to the shaft of the air valve, a pin mounted on the lever member and projecting therefrom, and a link member having one end portion engaged with the lC pin such that the rotational movement of the pin about the axis of the shaft is translated into the linear movement of the link member, the other end of the link member being connected to the fuel-metering rod.
The fuel metering means may further include a cylinder disposed in the fuel circuit in slidable engage-ment with the fuel-metering rod. Advantageously, the cylinder may have a fuel-flowing opening formed in the peripheral wall, while the fuel-metering rod may be formed therein with at least one slit cooperating with the fuel-flowing opening in the cylinder wall to define the variable fuel-metering orifice. Preferably, the fuel-flowing opening in the cylinder wall may constitute an outlet for the fuel. The fuel inlet may preferably be formed in the end wall of the cylinder opposite to the - 25 inner end of the fuel-metering rod.
- The pin may be positioned in a plane in which the butterfly valve lies. This positioning of the pin causes the opening area of the air valve to be substantially . . . . .
-.
..
.
. ... . . .
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~07~81 1 proportional to the displacement of the fuel-metering rod and thus to the opening area of the variable fuel-flowing orifice, with a result that the air-fuel ratio is kept always substantially constant. The pin may alter-natively be offset from the plane in which the butterflyvalve lies. With this alternative embodiment, the in-crease in the opening area of the air valve causes an increase in the opening area of the fuel-metering variable - orifice. The rate of the increase in the opening area of the fuel-metering variable orifice is in non-linear rela-tionship to the increase in the opening area of the air valve. This non~linear characteristic may be employed in combination with a proper angular positioning of the pin relative to the air valve to obtain an air-fuel control characteristic suited to a particular application of the associated internal combustion engine.
The above and other objects, features and advantages of the present invention will be made more apparent by the following desc-ription with reference to the accompanying drawings.
~RIEF DESCRIPTION OF THE DRAWIN~S
Fig. 1 is a partly sectional diagrammatic illustration of an embodiment of an air-fuel ratio control apparatus according to the present invention;
Fig. 2 schematically illustrates various angular positionings of a pin of the link mechanism relative to the plane in which an air valve lines;
:' .
.. .. . . : . :
.... . . . . . : .
.. . . . . . . .
, : .. . . ..
~:
:
1 Fig. 3 graphically illustrates the air-fuel ratio control characteristics of the apparatus according to the present invention with the positions of the pin varied as shown in Fig. 2; and Fig. 4 graphically illustrates the air-fuel ratios obtainable from the apparatus according to the invention with the angle ~ being maintained 15 and with the angle ~1 of the pin relative to the plane of the air valve being varied.
Referr1ng to Fig. 1, reference numeral 10 indicates an intake passage provided upstream of an intake manifold 102 of an internal combustion engine (not shown). There are disposed in the intake passage 10 a conventional throttle valve 12 operated by an engine accelerator (not shown) to control the flow of air fed into the engine and an air valve 16 located upstream of the throttle valve l2 to cooperate therewith to define an air pressure chamber 14. Air is caused to flow from an air cleaner (not shown) in a direction indicated by an arrow A into the~intake passage 10 by intake vacuum produced in the engine. The air flows through the passage 10 past the air valve 16 into the air pressure chamber 14 and hence passes through the throttle 25 valve 12 into the intake manifold 102 as indicated by an arrow Al and thus into respective engine cylinders (not shown).
. , . . ~ - , , .
~ `\
107~'~81 The air valve 16 is formed by a butterfly valve having a shaft 18 which extends transversely of the axis of the intake passage 10 and is rotatably mounted on the peripheral wall of . the inta]ce passa~e 10. One end portion of the shaft 18 extends outwardly from the intake passage 10 and is connected to a link 22 extending from a pressure controller 20 which is so arranged and constructed as to rotate the air valve 16 through the link 22 and the shaft 18 in response to variation in the pressure in the air pressure chamber 14 thereby to control the degree of opening of the air valve 16 so that the pressure in the air pressure chamber 14 and hence the pressure difference across the air valve 16 is maintained substantially constant irrespec-tive of the variation in the intake air flow to the engine. Such a pressure controller itself is known to those skilled in the . art, as is disclosed in U.S. Patent No. 3,739,762, for example.
In the case of the illustrated embodiment of the present inven-tion, the pressure controller 20 may be the one disclosed in the U.S. patent referred to. In any case, the degree of the air valve opening is controlled by the pressure controller 20 such that the pressure in the air pressure chamber 14 remains sub-stantially constant. Consequently, the difference in pressure between the air pressure chamber 14 and the atmosphere, i.e., the pressure difference across ~' , ' ~ ' ' .
: . . ' . .
' ' ' ' ' :. ,' : .:
.
1 the air valve 16, is also maintained substantially constant.
Thus, the intake air flow Ga is determined in dependence on the opening area of the air valve 16; that is, the cross-sectional area Aa of the passage defined between 5 the peripheral edge of the air valve 16 and the inner peripheral surface of the intake passage 10 (i.e., Ga is proportional to Aa).
A lever 24 is secured at one end thereof to the aforementioned projecting end portion of the shaft 18 of the air valve 16, while the other end of the lever 24 has a pin 26 secured thereto and projecting therefrom in the same direction as the shaft 18. A fuel metering means 30 is provided outside the intake passage 10 and includes a cylinder 32 accommodating a fuel-metering rod 15 34 for axial slidable movement therein. The rod 34 is connected at its outer end to the pin 26 through a link member 28. More specifically, the link member 28 has a slot 29 formed therein at an upper end portion thereof.
The pin 26 loosely extends through, or is loosely engaged with, the slot 29 in the link member 28 so that the rota-tional motion of the shaft 18 and hence the lever 24 together with the air valve 16 is translated into a linear movement of the fuel-metering rod 34 in the direc-tion indicated by an arrow B.
A fuel chamber 36 is defined by the cooperation of the inner end face of the fuel-metering rod 34 and the cylinder 32 and connected to a fuel tank 42 by a fuel supply line 40 provided with a fuel pump 38 therein.
.
:
t . . : .
.
1078~1 1 A line 46 having a pressure relief valve 44 is branched from the fuel supply line 40 at a point downstream of the pump 46 so that the fuel supplied into the fuel chamber 36 is maintained at a constant pressure level higher than the atmospheric pressure by the cooperation of the pump 38 and the pressure relief valve 44.
An axial bore 34a is formed in the inner end portion of the fuel-metering rod 34. A pair of slits 34b are formed longitudinally in the peripheral wall of the bore 34_ in diametrically opposite relationship with each other. On the other hand, a circumferential groove 32a is formed in the inner peripheral surface of the cylinder 32 at a position substantially aligned with the inner end portions (left end portions as viewed in Fig. 1) of the slits 34a to cooperate with the slits 34b to define a variable fuel-metering orifice. The annular groove 32a is connected to a fuel passage 48 leading to a f`uel injector 50 which is of a known structure a~d has a fuel-discharge orifice open to the intake passage 10 downstream of the throttle valve 12.
In the illustrated embodiment of the invention, there is provided a differential fuel pressure means 52 in the fuel passage 48 between the injector 50 and the fuel metering means 30. The differential pressure means 52 has first and second fuel pressure chambers 56 and 58 partitioned by a diaphragm 54. The fuel metered by the fuel metering means 30 and flowing out of the cyl nder 32 enters the second fuel pressure chamber 58 through an - _ 9 _ .
..
.
.
; . :
: 1078Z8~
, . .
l inlet port 58a and flows to the injector 50 from an out-let port 58b. The outlet or exit port 58b is defined by a valve seat member 62 having an annular valve seat 60 disposed in opposite and close contacting relation-" 5 ship with the diaphragm 54. A coil spring 64 is disposed around the valve seat member 62 and resiliently urges the diaphragm 54 away from the valve seat 60. On the other hand, the first fuel pressure chamber 56 of the differential fuel pressure means 52 is supplied with a fuel pressure in the fuel feed passage 40 by way of abranch passage 66 having a fixed restriction 68 provided therein. A fuel return passage 70 is connected to the branch passage 66 downstream of the fixed restriction 68 and extends to the fuel tank 42. There is provided in the return passage 70 a pressure control valve 72 which is operative to vary the return of the fuel through the .; . .
passage 70 to the fuel tank 42 thereby to vary the pressure in the chamber 56. The pressure control valve 72 is formed by a variable restriction, the degree of the opening of which is varied in dependence on changes in an operation parameter of the engine (e.g. temperature of the engine).
; The differential fuel pressure means 52 func-tions to maintain a constant pressure difference across the variable fuel-metering orifice (32a, 3~b) during normal engine operation. More specifically, since the opening degree of the pressure control valve 72 is maintained constant during the ;10~nal engine operation, ` the pressure of fuel introduced into the first fuel -. ' - 10 -.
. .
' 107~328~
1 pressure chamber 56 through the fixed restriction 68 from the fuel supply passage 40 is maintained constant by constant flow resistances (pressure loss) provided by the fixed restriction 68 and the pressure control valve 72. Consequently, the space between the diaphragm 54 and the valve seat 60 is increased as the pressure in the second fuel pressure chamber 58 is increased so that the flow resistance of the gap between the diaphragm 54 and the val~e seat 60 is reduced, and vice versa. Thus, the fuel pressure in the second fuel pressure chamber 58 is maintained at a level which is lower than that of the first fuel pressure chamber 56 by a constant value determined by the spring constant of the coil spring 64 irrespectively cf the quantity of fuel flowing out of the exit port 58b of the second fuel pressure chamber 58. On the ^ther hand, the fuel pressure in the fuel chamber 36 of the fuel metering means 30 is equal to that of the fuel supply passage 40 and higher than that of the pressure in the first fuel pressure chamber 56 by a predetermined constant value. Thus, the pressure difference across the variable fuel-metering orifice (32a, 34b) remains constant. The situation as brought about by variation in the opening degree of the pressure control valve 72 will be described hereinafter.
With the arrangement of the air-fuel ratio control apparatus described above, when the 1;hrottle valve 12 is rotated towards its full open position by the engine accelerator thereby to increase the rate of , ' ' ' .., .~
,', ' , ~ , ~".
107~
1 intake air flow, the pressure in the air pressure chamber 14 will tend to be reduced. This tendency will be sensed by the pressure controller 20 which then actuates the link 22 to rotate the shaf~ 18 and thus the air valve 16 towards its open position so as to maintain the pressure in the air pressure chamber 14 constant. The rotation of the air valve 16 is transmitted to the fuel metering rod 34 through the shaft 18, lever 24, pin 26 and the link 28, resulting in the axial movement of the rod 34 to the left as viewed in Fig. 1. Consequently, the area of overlap of the slits 34a with the annular groove 32a, that is, the fuel-flowing sectional area of the variable fuel-metering orifice, is correspondingly increased. The flow of fuel through the fuel-metering orifice (32a, 34b) is determined by the flow sectional area thereof and the fuel pressure difference across the fuel metering orifice. Now, assuming that the engine is in the normal operation with the pressure difference across the fuel metering orifice (32a, 34b) being con-stant, the fuel flow through the fuel metering orificewill be proportional to the fuel-flowing sectional area thereof. Thus, it can be said that the fuel flow through the fuel-metering orifice (32_, 34b) will increase as the area Aa of the opening of the air valve 16 is in-creased. In this connection, it will be noted that thefuel-flowing area of the fuel-metering orifice (32a, 34b) is exactly proportional to the displacement x of the fuel-metering rod 34 in the direction indicated by an --- 1()78'~8~
1 arrow ~.
~or mathematical analysis, assuming that an angle formed between a plane P extending perpendicularly : to the axis of the intake passage 10 and containing the axis of the shaft 18 of the air valve 16 and a plane of the air valve 16 in its fully closed position shown by a broken line (this angle will be hereinafter referred to as "angle of fully closed position") is represented by 90, an angle between a plane containing the plate of the air valve 16 and a plane containing both the axes of the pin 26 and the shaft 18 is represented by ~1~ an angle of the air valve between its fully closed and partly opened positions is represented by ~, the radius of the pin 26 (the distance between the axes of the shaft : 15 18 and the pin 26) is represented by _, and the inner diameter of the intake passage 10 is represented by D, the following relations apply valid in the case where ; l~l equals to zero (0) (i.e., in an embodiment in which the axis of the pin 26 is disposed in the plane of the air valve 16):
Aa = ~ [cos 90 - cos ( ~o + ~ )~ .-- (1) x = r ~ccs ~o - cos ( ~o + ~)~ ................ (2) Hence, Aa = ~C D2 1 = constant ................ (3) x 4 cos ~o r ' ' - ': , ' .. : , . :: . :
. .:
,, , , : :
~1~78Z81 .
1 In the equation (3), the axial displacement x of the fuel-metering rod 34 is exactly proportional to the flow sectional area of the variable fuel-metering orifice (32a, 34b). Consequently, the air-fuel ratio represented by Aa/x in the above equation (3) remains constant (refer to Fig. 3).
As will be appreciated from the above dis-cussion, the air-fuel ratio remains always constant irrespective of variation in the flow of engine intake air in the case where ~1 = - Such operation characteristic is advantageous when applied to an internal combustion engine designed to be driven at a constant speed under a constant load. However, for the engines designed to be operated under the circumstances in which the rotational speed as well as the engine load undergo variations, such as engines installed on motor cars, it is preferred from the view point of drivability of this type of engines to control the air-fuel ratio such that the air fuel ratio is relatively small ~i.e., mixture is sl-ghtly enriched) during part-load, low speed operating range of the engine and such that the air-fuel ratio is matched with the power air-fuel ratio in the full-load operating range. To this end, the lever 24 may be secured to the shaft 18 so that 'he axis of the pin 26 is angularly offset from the plane of the air valve 16 by an angle ~ 1~ as shown by broken lines in Fig. 2. In the case of the embodiment shown in Fig. 1, the mounting of the lever 24 on the shaft 18 is such that the angle ~1 takes 1~78~Bl 1 a positive value.
In the case where the angle ~1 is selected to j be a value other than zero, the ratio of the displacement x of the fuel-metering rod 34 to the air-flowing area Aa of the air valve is not always constant in contrast to the case of the embodiment in which ~1 is selected to ~e equal to zero. When the angle ~1 is of a positive value, the ratio Aa/x will be increased as the area Aa of the air valve (and hence the degree ~ of opening of the air valve) is increased. In other words, the air-fuel ratio takes a relatively small value (i.e. the fuel is enriched) for a relatively small intake air flow, and becomes greater (i.e. mixture becomes leaner) as the intake air flow is increased, as is shown in Fig. 3. On the other hand, when the angle ~1 is selected to be a negative value, the ratio Aa/x becomes smaller as the opening degree ~ of the air valve is increased, with the result that the air-fuel ratio is large for a relatively small intake air flow and decreases as the latter is increased, as can also be seen in Fig. 3. ~y way of example, Fig. 4 graphically illustrates the rela-; tionships of the air-fuel ratio to various preset values of the angle ~1 with the angle ~o Of the fully closed position of the air valve 16 being set to be 15. In this figure, the rate of intake air is taken along the abscissa, while the air-fuel ratio is scaled along the ordinate. ~he curves (a), (b), (c), (d) and (e) represent the air-fuel ratios for the preset angles ~1 cf -3~
. ~' :
107~Zf~l 1 -1, 0, 1 and 3, respectively. In this connection, it - should be mentioned that the position of the pin 26 and hence the ratio betwesn the radius r of the pin 26 and the inner dlameter D is changed in combination with the variation in the value of ~1 Accordingly, the curves (a), (b), (d) and (e) all lie below the straight line (c), indicating that the corresponding air-fuel ratios are smaller than the one obtained in the case where ~1 = (the straight line c). However, by changing the position of the pin 26, it is possible to obtain an operation characteristic that the curves (a), (b), (d) and (e) all lie above the line (c) to provide air-fuel ratios larger than that represented by the straight line (c). At any rate, the air-fuel ratio is decreased as the intake air flow is increased in the case where ~1 < ~
while the air-fuel ratio tends to be increased as the intake air flow increases in the case where ~1 >
When the opening degree of the pressure control valve 72 of the differential fuel pressure means 52 is varied in response to a change in the engine operation parameter, the fuel pressure in the first fuel pressure chamber 56 of the differential fuel pressure means 52 will undergo a corresponding variation, because the ratio between the flow resistances (pressure loss) pro-vided by the fixed restriction 68 and the pressure controlvalve 72 is changed. Since the fuel pressure in the second fuel pressure chamber 58 is maintained at a level lower than the pressure level in the first chamber ~(~7~3Z81 l 56 by a predetermined value, the pressure in the second fuel pressure chamber 58 will also undergo a corresponding change. For example, when the opening degree of the variable restriction or pressure control valve 72 is reduced, the fuel pressure in the first pressure chamber 56 will be increased, resulting in a corresponding increase in the pressure within the second fuel pressure chamber 58. On the contrary, the increase in the opening degree of the pressure control valve 72 will result in the corresponding decrease in the pressure within the first fuel pressure chamber 56 and hence in the decrease in the pressure within the second fuel pressure chamber 58.
Variation in the fuel pressure within the second fuel pressure chamber 58 as a function of the opening degree of the pressure control valve 72 provided in the fuel return passage 70 in turn brings about a correspond-ing change in the fuel pressure in the passage 48 downstream of the fuel-metering variable orifice (32a, 34b) of the ~uel metering means 30. In contrast, the fuel pressure upstream of the fuel-metering orifice (32_, 34b), i.e., within the fuel chamber 36 in the cylinder 32, remains constant, as described hereinbefore. Consequently, z variation in the fuel pressure downstream of the variable fuel-metering orifice will result in a change in the pressure difference across the fuel-metering orifice and hence in the rate of fuel flow therethrough. More specifically, even when the fuel-flowing cross-sectional area of the variable fuel-metering orifice remains constant, , .. , . -:, , ' ' ' ' ' 107gZf~l 1 the reduction in the degree of opening of the pressure control valve 72 in the fuel return passage 70 will cause a decrease in the pressure difference across the fuel-metering orifice with a resultant decrease in the fuel supply to the injector 50. On the contrary, an increase - in the degree of opening of the pressure control valve 72 will cause a corresponding increase in the pressure difference across the variable fuel-metering orifice (32a, 34b) and hence in the fuel flow to the injector 50. In this manner, the air-fuel ratio is corrected in dependence on variation in the engine operation para-meter by virtue of variation in the fuel flow through f the variable fuei-metering orifice of the fuel metering means 30.
As will be appreciated from the foregoing description of the preferred embodiments of the invention, the rotational movement of the air valve 16 ln the intake passage 10 is translated into a linear movement of the fuel-metering rod 34 through the link mechanism (24, 26 and 28) to meter and adjust the supply of the fuel into the engine. ~his enables the variable fuel-metering orifice (32a, 34_) of the fuel metering means to be manu-factured at a reduced cost and with a high precision.
Further, the angle ~1 cf the pin 26 relative to the plane of the air valve 16 may be set at an appro-priate value in consideration of the situation in which the engine to be equipped with the air-fuel ratio control apparatus of the invention is operated so that smooth and - 18 ~
1078~8~
1 continuous variation in the air-fuel ratio demanded by the engine is assured at a transition between different operating conditions of the engine, such as from idle or low-load operation to a part-load or full-load opera-tion. In addition, change in the coefficient of fuelflow rate in dependence on the opening degree of the air valve 16 can advantageously be corrected.
.
':
Claims (5)
1. An air-fuel ratio control apparatus for a fuel supply system of an internal combustion engine having an intake passage with throttle valve disposed therein, said apparatus comprising:
an air valve disposed in said intake passage upstream of said throttle valve to cooperate with said throttle valve to define an air pressure chamber in said intake passage;
pressure control means operative in response to variation in the air pressure in said air pressure chamber to control the degree of opening of said air valve so that the pressure difference across said air valve is maintained substantially constant;
a fuel supply circuit including an injector at the downstream end thereof for injecting fuel into said intake passage; and fuel metering means including variable fuel-metering orifice means provided in said fuel supply circuit and having a fuel-flowing area adapted to be varied in dependence on variation in the degree of opening of said air valve and a differential fuel pressure means normally to maintain the pressure difference across said variable fuel-metering orifice means substantially constant;
wherein said air valve is formed by a butterfly valve having a shaft rotatable therewith and said variable fuel-metering orifice means includes a fuel-metering rod linearly movable to vary the fuel-flowing sectional area of said fuel-metering orifice means, and wherein a link mechanism is provided between said shaft and said fuel-metering rod to translate the rotation of said shaft into a linear motion and to transmit the linear motion to said fuel-metering rod, said link mechanism being arranged such that the fuel-flowing sectional area of said variable fuel-metering orifice means is varied in dependence on the variation in the degree of opening of said air valve.
an air valve disposed in said intake passage upstream of said throttle valve to cooperate with said throttle valve to define an air pressure chamber in said intake passage;
pressure control means operative in response to variation in the air pressure in said air pressure chamber to control the degree of opening of said air valve so that the pressure difference across said air valve is maintained substantially constant;
a fuel supply circuit including an injector at the downstream end thereof for injecting fuel into said intake passage; and fuel metering means including variable fuel-metering orifice means provided in said fuel supply circuit and having a fuel-flowing area adapted to be varied in dependence on variation in the degree of opening of said air valve and a differential fuel pressure means normally to maintain the pressure difference across said variable fuel-metering orifice means substantially constant;
wherein said air valve is formed by a butterfly valve having a shaft rotatable therewith and said variable fuel-metering orifice means includes a fuel-metering rod linearly movable to vary the fuel-flowing sectional area of said fuel-metering orifice means, and wherein a link mechanism is provided between said shaft and said fuel-metering rod to translate the rotation of said shaft into a linear motion and to transmit the linear motion to said fuel-metering rod, said link mechanism being arranged such that the fuel-flowing sectional area of said variable fuel-metering orifice means is varied in dependence on the variation in the degree of opening of said air valve.
2. An air-fuel ratio control apparatus as defined in Claim 1, wherein said link mechanism includes a lever member secured to said shaft of said air valve, a pin mounted on said lever member and projecting therefrom, and a link member having one end port-on engaged with said pin such that the rotational movement of said pin about the axis of said shaft is translated into the linear movement of said link member, the other end of said link member being connected to said fuel-metering rod.
3. An air-fuel ratio control apparatus as defined in Claim 2, wherein said fuel metering means further in-cludes a cylinder disposed in said fuel circuit in slidable engagement with said fuel-metering rod, said cylinder having a fuel-flowing opening formed in the peripheral wall of said cylinder, said fuel-metering rod being formed there-in with at least one slit which copperates with said fuel-flowing opening in said cylinder wall to define said variable fuel-metering orifice.
4. An air-fuel ratio control apparatus as defined in Claim 2, wherein said pin is positioned in a plane in which said butterfly valve lies.
5. An air-fuel ratio control apparatus as defined in Claim 2, wherein said pin is offset from a plane in which said butterfly valve lies, the offset of said pin from said plane being so determined as to satisfy the requirement by said internal combustion engine in respect of the air-fuel ratio.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10407577A JPS5438441A (en) | 1977-08-30 | 1977-08-30 | Air fuel ratio controller for internal combustion engine fuel feeder |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1078281A true CA1078281A (en) | 1980-05-27 |
Family
ID=14371025
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA309,895A Expired CA1078281A (en) | 1977-08-30 | 1978-08-23 | Air-fuel ratio control apparatus for a fuel supply system of an internal combustion engine |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS5438441A (en) |
| CA (1) | CA1078281A (en) |
| DE (1) | DE2837190C2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5623562A (en) * | 1979-08-01 | 1981-03-05 | Toyota Motor Corp | Fuel injecting carburetor |
| DE3232606C2 (en) * | 1982-09-02 | 1984-06-28 | Daimler-Benz Ag, 7000 Stuttgart | Fuel injection system for mixture-compressing, externally ignited internal combustion engines with continuous injection into the intake manifold |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2596429A (en) * | 1946-08-08 | 1952-05-13 | George M Holley | Automotive pressure carburetor |
| US3068849A (en) * | 1959-05-22 | 1962-12-18 | Robert H Thorner | Speed regulating mechanism |
| FR1360294A (en) * | 1963-03-26 | 1964-05-08 | Sibe | Improvements made to supply devices for internal combustion engines operating by injection |
| DE2203018C3 (en) * | 1972-01-22 | 1974-11-28 | Bosch Gmbh Robert | Fuel injection system |
| US3739762A (en) * | 1972-01-24 | 1973-06-19 | Petrol Injection Ltd | Fuel injection systems |
| US3807710A (en) * | 1972-03-16 | 1974-04-30 | L Bergamini | Carburetor system |
| DE2403276C3 (en) * | 1974-01-24 | 1981-03-12 | Robert Bosch Gmbh, 7000 Stuttgart | Fuel injection system |
| FR2279935B1 (en) * | 1974-07-25 | 1977-01-07 | Sibe | IMPROVEMENTS TO FUEL SUPPLY DEVICES FOR INTERNAL COMBUSTION ENGINES |
| JPS523925A (en) * | 1975-06-25 | 1977-01-12 | Nippon Soken Inc | Fuel control device for internal combustion engine |
| JPS53134116A (en) * | 1977-04-27 | 1978-11-22 | Toyota Motor Corp | Fuel feeder for internal combustion engine |
| JPS587825B2 (en) * | 1977-05-04 | 1983-02-12 | トヨタ自動車株式会社 | Internal combustion engine fuel supply system |
-
1977
- 1977-08-30 JP JP10407577A patent/JPS5438441A/en active Pending
-
1978
- 1978-08-23 CA CA309,895A patent/CA1078281A/en not_active Expired
- 1978-08-25 DE DE19782837190 patent/DE2837190C2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5438441A (en) | 1979-03-23 |
| DE2837190C2 (en) | 1985-06-20 |
| DE2837190A1 (en) | 1979-03-15 |
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