GB2189296A - Carburetor fuel supply and torque converter control - Google Patents

Description

GB 2 189 296 A 1 SPECIFICATION an engine connected to drive a f I uid

torque converter in which a clutch is provided for mechanically Carburetor fuel supply control method connecting the input and output sides of the fluid torque converter, means for engaging the clutch The present invention relates to a fuel supply control 70 during speed reduction when the engine or vehicle method forthe carburetor of a vehicle engine speed is over a predetermined value, and a provided with a fluid torque converter and, in carburetor arranged to supply a reduced quantity of particular, a method for improving operation during fuel to the engine during the speed reduction.

deceleration of the vehicle. A preferred embodiment of the invention will now There a re wel 1 known advantages to providing a 75 be described by way of example and with reference f 1 uid torque converter connected to an engine with a to the accompanying drawings, in which:- cl utch that is used to mechanically connect the input Figure 1 is a diagrammatic illustration of a system and output sides of the torque converter during employing the present invention.

cruising speeds forfuel economy and furtherto Figure2 is a graph of the control characteristics of provide engine braking by engaging the clutch 80 the present invention.

during speed reduction. Engine braking results by Referring nowto Figure 1, the reference numeral 1 suppressing the slip of thefluid torque converter indicates a cylinder of the engine,the numeral 2 with the clutch engaged wherebythe counterdriving indicates an aircleaner, and the numeral 3 generally torque istransmitted to the engine sidefrom the indicates a carburetor. The carburetor3 is provided driving wheel side and the engine speed is kept 85 with a low speed fuel system consisting of an idle comparatively high compared with thatwhen the port 6 disposed on the downstream side of a throttle clutch is not engaged. A device for accomplishing a valve 5 of a suction pipe 4 and a fuel line 7 leading to fuel economizing effect by stopping the fuel supply said port 6. An idle adjusting screw 6a is disposed on during said engine braking period is also known the idle port 6. A pair of first and second air bleeding through Japanese Patent Application early 90 lines 8 and 9 communicating with the upstream publication Kokai) No. 60-1464 (1985). portion of the suction pipe4 are connected tothe When the speed reduction is continued in the upstream and intermediate portions of the fuel line 7, above-mentioned device with the fuel supply wherebythefuel introduced f rom a float chamber 10 stopped the engine may stall. One possible solution to the fuel line 7 is mixed with airfrom both air to this stalling problem may be to release the clutch 95 bleeding lines 8 and 9 and then discharged through simultaneously with restarting the fuel supplywhen the idle port 6. An electromagnetic valve 12 is the engine speed or the vehicle speed becomes connected to the second air bleeding line 9 and by lower than a predetermined value. However, in an opening the valve air is introduced into the second engine with a carbu retorforthe fuel supply, there is a air bleeding line 9 from an airf ilter 13 through valve time lag until a regular quantity of fuel is actually 100 12, thereby increasing the air supply to the fuel line 7 supplied to the engine cylinders through the suction bythat quantity and reducing the fuel supply line afterthe fuel supply is resumed in the carburetor quantityto the suction line 4 bythe i ncreased air and, in addition, the engine speed drops sharply due quantity.

to the release of the clutch whereby normally it is The output torque of the engine is transmitted to required that above said predetermined value be set 105 the driving wheel or wheels of the vehicle through a comparatively high. This results in additional fluid torque converter 14 and an auxiliary problemsthatthe operational area of the clutch is transmission (notshown). The fluid torque converter very narrow during the time of speed reduction, 14 includes, in an internal space which is defined on which makes it impossibleto sufficiently improve one side by an input case 15 connected tothe the engine braking performance in the low speed 110 crankshaft of the engine and on the otherside by a area, and also that a delay in acceleration is created pump 16 connected to the input case 15, both a due to aforesaid time lag when the speed reduction turbine 18 connected to a driving shaft 17 of an state is changed overto the acceleration state by auxiliary transmission and a stator 19 interposed stepping down on the acceleration pedal when the between the pump 16 and turbine 18. The torque engine or vehicle speed is above said predetermined 115 converter 14 also includes a clutch 20 which is value. operable for mechanically connecting the input case It is desirable to provide a fuel supply control 15 on the input side of the torque converter 14to the method which eliminates such disadvantages. turbine on the outputside. When the clutch 20 is Viewed from one aspeetthe invention provides a disengaged, the rotational drive is transmitted carburetorfuel supply control method for an engine 120 between the engine and the auxiliary transmission with a fluid torque converter in which a clutch is byfluid torque transmission through circulation of provided for mechanically connecting the input and the internal fluid between the aforesaid impellers 16, output sides of the fluid torque converter and in 18 and 19. The clutch 20 may be of various types, which said clutch is engaged during speed reduction such as a m ulti-disc type friction clutch. In theshown when engine orvehicle speed is overa 125 example,the clutch is a single- disctype friction predetermined value, wherein fuel is supplied ata clutch in which there is provided a clutch disc20a reduced quantityfrom a lowspeed fuel system of made movable in the axial direction in the gap said carburetor during said speed reduction. between the input case 15 and the turbine 18 and Viewed from another aspect the invention connected to the turbine 18through a damper spring provides apparatus for driving a vehicle, comprising 13020b. The internal space of said torque converter 14 is 2 GB 2 189 296 A 2 partitioned by said clutch disc 20a into an impeller acceleration pedal released as is apparentfrom housing chamber 21 on one side and a back pressure Figure 2, application of the clutch 20 and fuel chamber 22 on the other side between the input case reduction are performed when the engine rotational and the clutch disc 20a, connection and speed Ne is at and above the predetermined value disconnection of said clutch 20 are performed by a 70 Ne-0, and the release of the clutch 20 and the end of control valve 23. the fuel reduction, i.e. the resumption of regularfuel The control valve 23 can be selectively switched supply from the low speed fuel system, are between a righthand side clutch released position performed when the engine rotational speed Ne (i.e. the shown position) and a lefthand side clutch drops below Ne-0, that is, to the left of line A in Figure applied position. In the shown righthand side clutch 75 2.

released position, a first oil line L1 forthe oil supply If thefuel supply is stopped in the area atand leading from an oil pressure source 24 is connected above Ne-0 and thefuel supply is restarted when Ne to a second oil line L2 leading to the backpressure;lrops below Ne-0, even thefuel which is stuckto the chamber 22 thereby to supplythe oil to the back wall surface would be inhaled into the cylinder 1 pressure chamber22 and a third oil line L3 leadingto 80 during thefuel supply suspension and thetime lag the impeller housing chamber21 is connected to a until a regularquantity of fuel is supplied tothe first oil drain line LD1 therebyto drain the oil from cylinder 1 would be extended. When Ne-0 is setJor said housing chamber21. In the lefthand side clutch example, lowerthan 1, 500 r.p.m.,the engine stalls applied position,the first oil line L1 is connected to because of the lowering of the engine speed Ne due thethird oil line L3 therebyto supplythe oil tothe 85 tothe release of the clutch 20 during such time lag.

housing chamber21 and the second oil line L2 is However, if fuel is supplied at a reduced quantity as connected to a second oil drain line LD2 therebyto described above in the area at and above Ne-O,the drain the oil from said back pressure chamber 22. In return performance of the fuel supplyto the cylinder said clutch applied position, the internal pressure of 1 is superiorto the situation in which thefuel supply said housing chamber 21 is held ata comparatively 90 is stopped when it becomes lowerthan Ne-0, and high pressure by a checkvalve 25 which is disposed engine stall will not occur even when Ne-0 is set at a in the third oil drain line LD3 leading to said housing comparatively low value such as 000 r.p.m. It is also chamber 21 so thatthe clutch disc 20a is pressed possible to determine the no load status of the againstthe input case 15 by the internal pressure engine with a negative pressure signal by utilizing, in therebyto achieve mechanical torque transmission 95 place of the throttle opening sensor 28, a negative due to engagement of the clutch 20. pressure sensorwhich detects the suction negative Afourth oil line L4 branched from the first oil line pressure on the downstream side of thethrottle L1 is connected to an oil chamber 23a atthe valve 5. A vehicular speed sensor which detects the righthand end of the control valve 23 and a branch oil vehicular speed may also be utilized in place of the line L4a. The branch oil line L4a has an orifice therein 100 engine speed sensor 29 thereby to control the and is connected to an oil chamber 23b atthe release of the clutch 20 and the end of thefuel lefthand end of control valve 23.An electromagnetic reduction condition. The means for reducing fuel is type drain valve 26 is connected to oil line L4a not limited to the above- m.entioned embodiment between the orifice and chamber 23b. Thus, when oil but also can be constructed withjor example, a drain valve 26 is opened,the control valve 23 moves 105 variable aperture means disposed in thefuel line 7.

leftward againsta spring 23c bythe pressure In summary, when the engine is running undera difference between oil chambers 23a and 23b, and no load condition with the accelerator pedal changes overto the clutch applied position. released, if the engine speed orthe vehicularspeed The oil drain valve 26 and aforesaid atmospheric is over a predetermined value, the clutch is engaged open valve 12 are opened and closed switching the 110 therebyto apply sufficient engine braking and the power on and off, respectively, to the solenoids 12a fuel is supplied at reduced quantityfrom the low and 26a of said respective valves 12 and 26 by a speed fuel system of the carburetor atthe sametime.

control circuit 27. To the control circuit 27 are When the engine speed orthe vehicular speed connected a throttle opening sensor 28 which becomes lowerthan the predetermined value, the generates a signal corresponding to the opening 0 of 115 clutch is released and regular quantity of fuel is also the throttle valve 5 and an engine speed sensor 29 supplied from the low speed fuel system, thereby which generates a signal corresponding to the preventing engine stall. The fuel is thus supplied engine speed Ne. The control circuit 27 functions to from the low speed fuel system during speed applythe clutch 20 by opening the oil drain valve 26 reduction, and the regular quantity of fuel is supplied when the speed of rotation of the engine is higher 120 to the cylinder immediately upon stopping the than the line A shown in Figure 2. Furthermore, the reduction of fuel supply which makes the control circuit 27 functions to open the atmospheric returnability of the fuel supply better, thus making it air supplyvaive 12 under no load conditions of the possible to setthe predetermined value of engine or engine in the aforesaid region, i.e. in the extremely vehicle speed at a comparatively lowvalue. As a lowthrottle opening area belowthe line B in Figure 2, 125 result, it becomes possible to expand the operational in which the throttle opening 0 is below a area of the clutch at the time of speed reduction and predetermined reference opening 0-0 therebyto to improve the engine braking performance overthe reduce thefuel supplyfrom the low speed fuel low speed area.

system, as described above. Thus a fuel economizing effect of approximately Atthetime of speed reduction with the 130 the same extent as the conventional system which 3 GB 2 189 296 A 3 stops the fuel supply is obtainable and it is also 10. Acarburetorfuel supply control method possible to extend the range of the clutch application substantially as hereinbefore described with area toward the low speed side at the same time, reference to the accompanying drawings.

thereby making it possible to make the best use of 11. Apparatus ford riving a vehicle substantially the engine braking effect in a speed reduction phase 70 as hereinbefore described with referencetothe of the vehicle operation, and in addition preventing accompanying drawings.

delay in acceleration in changing-over from speed reduction to acceleration to improve performance during driving. 10 Modifications of the invention both in its broad Printed for Her Majesty's Stationery Office by Croydon Printing Company (UK) Ltd,8187, D8991685. aspects and its specific embodiments may be Published byThePatentoffice,25 Southampton Buildings, London, WC2A lAY, apparentto those skilled in the art and it is intended from which copies maybe obtained. that such modif ications are within the scope of this disclosure, regardless of whether anyfeatures presently described and/or claimed may be omitted.

Claims (9)

1. A carburetorfuel supply control method for an engine with a fluid torque converter in which a clutch is provided for mechanically connecting the input and output sides of the fluid torque converter and in which said clutch is engaged during speed reduction when engine orvehicle speed is over a predetermined value, wherein fuel is supplied ata reduced quantityfrom a low speed fuel system of said carburetor during said speed reduction.

2. A control as claimed in claim 1, wherein a no load condition of engine operation is determined for the supply of fuel at a reduced quantity.

3. A control method as claimed in claim 2, wherein a substantially closed position of an engine throttle is detected for determining the no load condition.

4. A control method as claimed in claim 3, wherein a throttle opening below a predetermined value is detected as said substantially closed position.

5. Acontroi method as claimed in claim 2, wherein an intake suction pressure is detected for determining said substantially no load condition.

6. A control method as claimed in any preceding claim, wherein the carburetor supplies a normal supply of fuel to the engine upon the engine or vehicle speed dropping below said predetermined value and said reduced quantity of fuel supply is discontinued.

7. A control method as claimed in any preceding claim, wherein engine or vehicle speed is determined selectively to engage and disengagethe clutch.

8. Apparatus for driving a vehicle, comprising an engine connected to drive a fluid torque converter in which a clutch is provided for mechanically connecting the input and output sides of thefluid torque converter, means for engaging the clutch during speed reduction when the engine orvehicle speed is over a predetermined value, and a carburetor arranged to supply a reduction quantity of fuel to the engine during the speed reduction.

9. Apparatus as claimed in claim 8, including means for determining a. no load condition of the engine, wherein the carburetor is operable to supply the reduced fuel quantity during the speed reduction and the no load condition.