CA1289827C

CA1289827C - Carburetor fuel supply control method

Info

Publication number: CA1289827C
Application number: CA000534604A
Authority: CA
Inventors: Hitoshi Yamabe; Keiichi Ishikawa; Toshio Sato; Hiroaki Iwasaki
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1986-04-15
Filing date: 1987-04-14
Publication date: 1991-10-01
Anticipated expiration: 2008-10-01
Also published as: FR2597154A1; GB2189296B; DE3712582A1; GB8709013D0; JPS62243952A; GB2189296A; FR2597154B1

Abstract

ABSTRACT OF THE DISCLOSURE

A carburetor fuel supply control method for an engine with a fluid torque converter having a clutch for mechanically connecting the input and output sides thereof, in which the clutch is engaged during speed reduction when the engine speed or the vehicular speed is over a predetermined value under a no load condition of the engine for causing engine braking. Under this method, fuel is supplied at a reduced quantity from a low speed fuel system of the carburetor during the speed reduction to avoid stalling of the engine when the clutch is released and the normal fuel supply resumed.

Description

~ 2~ 27 178/129 Patent S P E C I F I C A T I O N
CARBURETOR FUEL SUPPLY CONTROL METHOD
_ _ _ The present invention relates to a fuel supply control method for the carburetor of a vehicular engine provided with a fluid torque converter and, in particular, a method for improving operation during deceleration of the vehicle.
There are well known advantages to providing a fluid torque converter connected to an engine with a clutch that is used to mechanically connect the input and output sides of the torque converter during cruising speeds for fuel economy and further to provide engine braking by engaging the clutch during speed reduction. Engine braking results by suppressing the slip of the fluid torque converter with the clutch engaged whereby the counter driving torque is transmitted to the engine side from the driving wheel ~ide and the engine speed is kept comparatively high compared with that when the clutch is not engaged. A device for accomplishing a fuel economizing effect by stopping the fuel supply during saicl engine braking period is also known through Japanese Patent Application early opening (Kokai) No. 60-1464 (1985).
When the speed reduction is continued in the above mentioned device with the fuel supply stopped, the engine may stall. One possible solution to this stalling problem may be to release the clutch simultaneously with restarting the fuel supply when the engine peed or the vehicular speed becomes lower than a predetermined value. However, in an engine with a carburetor for the fuel 6upply, there is a tims lag until a regulator quantity of fuel i8 actually supplied to the engine cylinders through the suction line after the fuel supply is resumed in the carburetor and, in addition, the engine speed drops sbarply due to the ~' 2 ~ 7 178/129 Patent release of the clutch whereby normally it is required that above said predetermined valua be set comparatively high. This results in additional problem~ that the operational area of the clutch is very narrow during the time of speed reduction, which makes it impossible to sufficiently improve the engine braking performance in the low speed area, and also that a delay in acceleration is created due to aforesaid time lag when the reduction state is changed over to the acceleration state by stepping down on the acceleration-pedal when the engine or vehicle speed is above said predetermined value.
It is an ob;ect of the present invention to provide a fuel supply control method which eliminates such disadvantages.
According to the present invention, a fluid torque converter is connected to an engine with a carburetor in which a clutch is used for mechanically connecting the input and output sides of said fluid torgue converter, wherein said clutch is made to operate during speed reduction when the engine speed or the vehicular speed is over a predetermined value under a no load condition of the engine, characterized in that fuel is supplied at a reduced guantity from ths low speed fuel system of said carburetor during said speed reduction.
The foregoing ob~ects and advantages o~ the present invention wlll appear more fully from a considerat$on of a detailed description of a preferred embodiment as shown in the accompanying drawings, wherein:
F~g. 1 is a diagrammatic illustration of a system Rmploying the present invention.
Fig. 2 i6 a graph of the control characteristics of the present invention.

~ 2~R~ 60724-1727 Referring now to Fig. 1, the reference numeral 1 indicates a cylinder of the engine, the numeral 2 indicates an air cleaner, and the numeral 3 generally indicates a carburetor.
The carburetor 3 is provided with a low speed fuel system consisting of an idle port 6 disposed on the downstream side of a throttle valve 5 of a suction pipe 4 and a fuel line 7 lead-ing to said port 6. An idle adjusting screw 6a is disposed on the idle port 6. A pair of first and second air bleeding lines 8 and 9 communicating with the upstream portion of the suction pipe 4 are connected to the upstream and intermediate portions of the fuel line 7, whereby the fuel introduced from a float chamber 10 to the fuel line 7 is mixed with air from both air bleeding lines 8 and 9 and then discharged through the idle port 6. An electromagnetic valve 12 is connected to the second air bleeding line 9 and by opening valve 12, air is introduced into the second air bleeding line 9 from an air filter 13 through valve 12, thereby increasing the air supply to the fuel line 7 by that quantity and reducing the fuel supply quantity to the suction line 4 by the increased air quantit~.
The output torque of the engine is transmitted to the driving wheel or wheels of the vehicle through a fluid torque converter 14 and an auxiliary transmission (not shown). The fluid torque converter 14 includes, in an internal space which is defined on one side by an input case 15 connected to the crankshaft of the engine and on the other side by a pump 16 connected to the input case 15, both a turbine 18 connected to a driving shaft 17 of an auxiliary transmission and a stator 19 interposed between the pump 16 and turbine 18. The torque converter 14 also includes a clutch 20 which is operable for mechanically connecting the input case 15 on the input side of ~'. 3 Patent the torque converter 14 to the turbine 18 on the output side.
When the clutch 20 is disengaged, the rotational drive is transmitted between the engine and the auxiliary transmission by fluid torque transmission through circulation of the internal fluid between the aforesaid impellers 16, 18 and 19. The clutch 20 may be of various types, such as a multi-disc type friction clutch. In the shown example, the clutch is a single-disc type friction clutch in which there is provided a clutch disc 20a made movable in the axial direction in the gap between the input case 15 and the turbine 18 and connected to the turbine 18 through a damper spring 20b. The internal space of said torque converter 14 iR partitioned by said clutch disc 20a into an impeller housing chamber 21 on one side and a back pressure chamber 22 on the other side between the input case 15 and the clutch disc 2Oa.
Connection and disconnection of said clutch 20 are performed by a control ~alve 23.
The control valv~ 23 can be seleotively switched between a righthand side clutch released position (i.e. the shown position) and a lefthand ~icle clutch applied position. In the shown righthand side clutch released position, a first oil line Ll for the oil supply leading ~rom an oil pressure source 24 is connected to a second oil line L2 leading to the back pressure chamber 22 thereby to supply the oil to the back pressure chamber 22 and a third oil line L3 leading to the impeller housing chamber 21 is connected to a first oil drain line LDl ~hereby to drain the oil from said housing chamber 21. In the lefthand side clutch applied position, the first oil line Ll is connected to the third oil line L3 thereby to supply tha oil to the housing chamber 21 and the se¢ond oil line L2 is connected to a second oil drain line LD2 thereby to drain the oil from said back ~ Patent pressure chamber 22. In said clutch applied position, the internal p~essure of said housing chamber 21 is held at a comparatively high pressure by a check valve 25 which is disposed in the third oil drain line LD3 leading to said housing chamber 21 so that the clutch disc 20a is pressed against the input case 15 by the internal pressure thereby to achieve mechanical torque transmission due to engagement of the clutch 20.
A fourth oil line L4 branched from the first oil line Ll is connected to an oil chamber 23a at the righthand end of the control valve 23 and a branch oil line L4a. The branch oil line L4a ha~ an orifice therein and iB connected to an oil chamber 23b at the lefthand end of control valve 23. An electromagnetic type drain valve 26 is connected to oil line L4a between the orifice and chamber 23b. Thu6, when oil drain valve 26 i8 opened, the control valve 23 move~ leftward against a spring 23c by the pre3sure difference between oil chambers 23a and 23b, and changes over to the clutch applied position.
The oil drain valve 26 and aforesaid atmospheric open valve 12 are opened and closed switching the pow~r on and off, respectively, to the solenoids 12a and 26a of said respective valves 12 and 26 by a control circuit 27. To the control circuit 27 are connected a throttle opening sensor 28 which generates a signal corresponding to the opening ~ o~ the throttle valve 5 and an engine speed sensor 29 which generates a signal corresponding to the engine speed Ne. The control circuit 27 functions to apply the clutch 20 by opening ths oil drain valve 26 when the speed of rotation of the engine is higher than the line A sho~n in Fig. 2. Furthermore, the control circuit 27 functions to open the atmospheric air suppl~ valve 12 undar no load conditions of the engine in the aforesaid region, i.e. in the extremely low .

~ Patent throttle opening area below the line B in Fig. 2, in which the throttle opening ~ is below a predetermined reference opening 3-0 thereby to reduce the fuel supply from the low speed fuel system, as described above.
At the time of speed reduction with the accel~ration pedal released, as it is apparent from Fig. 2, application of the clutch 20 and fuel reduction are performed when the engine rotational speed Ne iB at and above the predetermined value Ne-0, and the release of the clutch 20 and the end of fuel reduction, i.e. the resumption of regular fuel supply from the low speed fuel system, are performed when the engine rotational speed Ne drops below Ne-0, that is, to the left of line A in Fig. 2.
When the fuel supply is stopped in the area at and above Ne-0 and the fuel supply is restarted when Ne drops below Ne-0, even the fuel which is stuck to the wall surface is inhaled into the cylinder 1 during the fuel supply suspension and the time lag until a regular quantity of fuel is supplied to the c~linder 1 is extended. When Ne-0 is set, for example, lower than 1,500 r.p.m., the engine stalls because of the lowering of the engnie speed Ne due to the release of the clutch 20 during such time lag. However, if fuel is supplied at a reduced quantity as described above in the area at and above Ne-0, the return per~ormance of the fuel supply to the cylinder 1 is superior to the situation in which the fuel supply i8 stopped when Ne becomes lower than Ne-0, and engine stall will not occur even when Ne-0 is set at a comparatively low value such as 900 r.p.m. It is also possible to determine the no load status of the engine with a negative pressure signal by utilizing, in place of the throttle opening sensor 28, a negative pressure sensor which detects the suction negative pressure on the downstream side of the throttle ? :~R~9~%'7 Patent valve 5. A vehi~ular speed sensor which detects the vehicular speed may also be utilized in place of the engine speed sensor 29 thereby to control the release of the clutch 20 and the stop of fuel reduction. The means for reducing ~uel is not limited to above-mentioned embodiment, but also can be constructed with, for example, a variable aperture means disposed in the fuel line 7.
In summary, when the engine is running under a no load condition with the acceleration pedal released, if the engine speed or the vehicular speed is over a predetermined value, the clutch is operated thereby to apply sufficient engine braking and the fuel is supplied at reduced quantity from the low speed fuel system of the carburetor at the same time. When the engine speed or the vehicular speed becomes lower than the predetermined value, the clutch i5 released and regular quantity of fuel is also supplied from the low speed fuel system, thereby preventing engine stall. According to the present invention, the fuel is supplied from the low speed fuel system during speed reduction, and the regular quantity of fuel is supplied to the cylinder immediately upon stopping the reduction of fuel supply which makes the returnability o~ the fuel supply better, thus making it possible to set the predetermined value o~ engine or vehicle speed at comparatively low value. As the result, it becomes possible to expand the operational area of the clutch at the time~ of speed reduction and to improve the engine braking performance over the low speed area.
Thus, according to the present invention, a fuel economizing effect of approximately the same extent as the conventional system which stop3 the fuel supply is obtainable and it is also possible to extend the range o~ the clutch application area toward the low speed side at the sams time, thereby making it ~12~R27 Patent possible to make the best use of the engine braking effect in a speed reduction phase of the vehicle operation, and in addition, preventing delay in acceleration in a changing-over from speed reduction to acceleration to improve the drivability.

Claims

1. A carburetor fuel supply control method for an engine with a fluid torque converter in which a clutch is provided in said fluid torque converter for mechanically connecting the input and output sides thereof and in which said clutch is engaged during speed reduction when engine or vehicular speed is over a predetermined value, characterized in that fuel is supplied at a reduced quantity from a low speed fuel system of said carburetor during said speed reduction.

2. The control method of claim 1, wherein a no load condition of engine operation is determined for said supplying of fuel at a reduced quantity.

3. The control method of claim 3, wherein the carburetor supplies a normal supply of fuel to the engine upon the engine or vehicular speed dropping below said predetermined value and said reduced quantity of fuel supply is discontinued.

4. The carburetor fuel supply control method for an engine having a torque converter with a clutch for connecting the input and output sides of the torque converter above predetermined engine or vehicle speeds, comprising the steps of determining engine or vehicle speed and selectively engaging and disengaging the clutch, determining engine load condition, and operating the carburetor for supplying a small quantity of fuel to the engine under a substantially no load condition of the engine when the clutch is engaged.

5. The control method of claim 4, including the step of operating the carburetor to discontinue said small quantity of fuel and provide a normal quantity of fuel when said clutch is disengaged during reducing engine or vehicle speed.

6. The control method of claim 4, wherein a substantially closed position of an engine throttle is detected for determin-ing said substantially no load condition.

7. The control method of claim 6, wherein a throttle opening below a predetermined value is detected as said substantially closed position.

8. The control method of claim 4, wherein an intake suction pressure is detected for determining said substantially no load condition.