US3503594A

US3503594A - Fuel system

Info

Publication number: US3503594A
Application number: US754180A
Authority: US
Inventors: Kenji Goto
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 1967-08-28
Filing date: 1968-08-21
Publication date: 1970-03-31
Anticipated expiration: 1987-03-31
Also published as: DE1751913B2; DE1751913C3; FR1577028A; DE1751913A1; GB1239285A

Description

KENJI GOTO March 31, 1970 FUEL SYSTEM 2 Sheets-Sheet 1 7 Filed Aug. 21, 1968 FIG. 2

INVENTOR.

KENJI GOTO FUEL SYSTEM March 31, 1970 2 Sheets-Sheet 2 Filed Aug. 21, 1968 4,000 REM.

B nooo 2,600 3600 Q WK (Yum United States Patent 3,503,594 FUEL SYSTEM Kenji Goto, Toyota-cho, Toyota-shi, Japan, assignor to Toyota Jidosha Kogyo Kabushiki Kaisha, Toyota-cho, Toyota-shi, Aichi-ken, Japan, a corporation of Japan Filed Aug. 21, 1968, Ser. No. 754,180 Claims priority, application Japan, Aug. 28, 1967, 42/ 54,814 Int. Cl. F02m 7/12 US. Cl. 26141 Claims ABSTRACT OF THE DISCLOSURE A carburetor for automobiles has an idle and lowspeed pneumatic circuit for idling or running operation at the low speed of the engine. This pneumatic circuit consists of a series of openings and holes formed in the carburetor body which connect between an upper part of the carburetor air intake passage and ports below the throttle valve. To supply an air-fuel mixture of satisfactory richness for deceleration of the automobile by the engine brake, there is provided another pneumatic circuit which connects between an opening in the intake passage wall above the throttle valve and an opening below the throttle valve and the idle and low-speed pneumatic circuit has a branch line leading into this circuit. In this circuit there is provided a valve whose opening is controlled and is dependent upon the vacuum in the intake manifold.

BACKGROUND OF THE INVENTION The present invention relates to a fuel system for automobile engines, and more particularly to a device for controlling an air-fuel mixture in the deceleration of the engine.

The opening of the throttle valve of a carburetor in the deceleration of an automobile by the engine brake is similar to that in its idling operation but, the speed of rotation of the engine is higher. Since the total amount, as well as the mixing ratio of air-fuel mixture to be fed to the engine at that time is the same as when idling, the higher the speed of rotation, the smaller the amount of the air-fuel mixture which is fed to the cylinders, and at every stroke, the amount becomes smaller. In addition to this, the remaining gas dilutes the mixture so that firing of the mixture by ignition plugs will be impossible. Consequently, there will occur what can be called an after-burn. That is to say, the gas which has not yet burnt in the cylinders is brought into combustion in the exhaust pipe, or the gas which has not fully burnt will result in air pollution.

It is Well known to hold the opening of the throttle valve in deceleration, at a larger value than in idling, and moreover to slow down the closing movement of the throttle valve. This, is effective for preventing the engine from stopping, but it has the following disadvantages in respect to misfiring:

(I) The setting of the optimum amount of air in deceleration is difficult.

(II) The range of combustible air-fuel mixture in deceleration is narrow and difficult in its setting.

(III) It is ditficult to obtain a good result during descent during which deceleration continues relatively long.

SUMMARY OF THE INVENTION The principal object of the present invention is to provide an improved fuel system in which a satisfactory air to fuel ratio in deceleration may be held independently of idling.

Another object of the invention is to provide an improved fuel system in which misfiring may be almost completely avoided.

3,503,594 Patented Mar. 31, 1970 "ice A further object of the invention is to provide an improved fuel system in which atomization as well as mixing of fuel in the low-speed pneumatic circuit may be improved also in idling, in acceleration or in normal running.

According to the present invention there is provided a device for controlling air-fuel mixture in the deceleration of the engine having an idle and low-speed pneumatic' circuit opening into the air intake passage of a carburetor below the throttle valve thereof, the device includes an additional pneumatic circuit for connecting a part of the air intake passage above the throttle valve to a part below the throttle valve and a valve assembly mounted in the additional circuit. The idle and low-speed pneumatic circuit is connected into a part of the additional circuit above the valve assembly by a branch line. The valve assembly, normally closed, is opened, when there is a vacuum formed in the air passage below the throttle valve.

Other features and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a longitudinal section of a carburetor embodying the invention;

FIG. 2 illustrates a modification of the air-inlet part in FIG. 1;

FIG. 3 is a connection diagram of the electric components of another embodiment of the invention; and,

FIG. 4 is a diagram illustrating the operation of the device according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, air sucked into the air intake passage 2 of a carburetor 1 in high speed operation mixes with fuel supplied from a high-speed nozzle 4 which opens into a secondary venturi 3, and is delivered to cylinders of an engine (not shown) through a main venturi 5. A throttle valve 6 serves to control the amount of air-fuel mixture to be delivered to the-cylinders. An idle and low-speed pneumatic circuit 9 connects on the one hand, between the upper part of the air intake passage 2 in the vicinity of the secondary venturi 3 and, on the other hand, a low-speed port 8 having the shape of a narrow slit in the vicinity of the throttle valve 6. The top of the low-speed circuit 9 is provided with a second low-speed air bleeder 7. Fuel F flowing from a float chamber (not shown) through a low-speed jet 10 mixes with air which enters from the air passage 2 through a first low-speed air bleeder 11 located at nearly the same position as the secondary low-speed air bleeder 7 in the direction of the air intake passage 2, and then flows into the idle and low-speed pneumatic circuit 9 through an economizer jet 12 to form a mixture necessary for idling or low-speed operation together with air supplied through the secondlow-speed air bleeder 7. Just below the lowspeed port 8 there is provided an idle port 13 which communicates with the idle and low-speed pneumatic circuit 9 and whose cross section is adjustable by means of an idle adjustment needle 14.

Deceleration circuit 24 consists of an upper section 2411 and a lower section 24b, and connects between an opening 21 located above venturi 3, i.e., above the throttle valve 6, and an opening 22 below the idle port 13, therefore below the throttle valve 6. In the lower section 24b there is mounted a valve assembly 23. For the opening 21 there may 'be substituted an air inlet pipe 21' which extends into the air intake passage 2 as shown in FIG. 2. 25 denotes an adjustment needle for adjusting air flowing into the upper pneumatic circuit section 24a. The

upper section 24a above the valve assembly 23 communicates with the idle and low-speed circuit 9 through a passage 26,

The valve body 31 of the valve assembly 23 is coupled to a diaphragm 33 of a vacuum responsive device 32. The diaphragm 33 separates a first diaphragm chamber 34 which is in communication with the circuit section 24b from a second diaphragm chamber 35 which communicates with an opening 37 in the intake manifold 40 so that the valve assembly 23 may cause the valve body 31 to close or open in response to vacuum in the intake manifold 40. An adjustment screw 38 serves to adjust the biasing force of a Spring 39 for biasing the diaphragm 33.

During idling, normal rumiing or acceleration of the engine, vacuum in the intake manifold 40 lies in the range from to 530 mm. Hg (with respect to an atmospheric pressure), in which the valve assembly 23 is held closed as shown. In this case, the passage consisting of

sections

21, 24a and 26 serves as a third low-speed air bleeder for the idle and low-speed pneumatic circuit 9 together with the second low-speed air bleeder 7, and promotes atomization of the fuel in the idle and lowspeed circuit. Namely, air from the opening 21 flows into the circuit 9 through the air adjustment needle 25, deceleration circuit section 24a and the fuel adjustment needle 27, and mixes with the air-fuel mixture from the economizer jet 12.

With increase of vacuum (normally in the range from 630 to 660 mm. Hg) in the intake manifold 40 due to application of engine brake, the diaphragm 33 of the vacuum responsive device 32 deflects to the right, and causes the valve body 31 to move in the same direction thereby opening the valve assembly 23 as shown. Consequently, air from the opening 21 flows into the intake manifold 40 through the deceleration circuit 24a, 2411, the then opened valve assembly 23 and the opening 22. Now, vacuum developing in the section 24b serves to suck more fuel through the jet 12. A large portion of the air-fuel mixture from the jet 12 branches off into the deceleration circuit 24, and mixes with air from the circuit section 2401, The air-fuel mixture of a satisfactory richness is now fed to the intake manifold 40 through the then opened valve assembly 23 and the opening 22. The fuel adjustment needle 27 and the air adjustment needle 25 may be adjusted to form the mixture of a desired richness.

To actuate the valve assembly there may be provided a magnet valve whose coil is connected in series with a switch which is operated mechanically by a negative responsive device. Such an embodiment is shown in FIG. 3. A diaphragm 33' of a vacuum responsive device 32', which is applied at one side with vacuum in the intake manifold 40 through an opening 37, carries a bridging contact of a switch 41 inserted in the energizing circuit of a magnet valve 23'. Upon application of engine brake, vacuum in the intake manifold 40 causes the switch 41 to close so that current flows from a battery 42 to the coil 43 of the magnet valve 23. A core 44 then magnetized attracts a valve body 31 against the force of a biasing spring 45, thereby providing communication between deceleration sections 24a and 24b. 46 denotes a pilot lamp for indicating energization of the magnet coil 43. In this embodiment, air for deceleration circuit is supplied from an air cleaner 52 having a filter 51 mounted on the carburetor body. The embodiment has the advantage that the vacuum responsive device 32 including the switch and the valve assembly 23' as well as the magnet can be separately mounted.

FIG. 4 illustrates the relation between the speed of rotation N of an engine and the vacuum P in the manifold. A solid line represents the relation while idling, while a broken line represents the relation in deceleration. If the negative responsive device in FIG. 1 or FIG. 3 is so set as to respond at A mm. Hg, it will remain operative until the engine is decelerated up to B r.p.m.

According to normal running tests of a medium-sized passenger car with a seating wpacity of 5 on which an engine having a piston displacement of 1500 cc. in streets in a city or its suburbs, deceleration occured most frequently at normal speeds, namely at speeds ranging from 40 to 60 km./hr., and, in the time required for this operation at the above speeds amount to 19 percent of the total running time. The total deceleration time in a test accounted for 31% of the total running time. On the other hand, according to observation of the engine on the test stand, it was found out that there was a strong tendency of misfiring of plugs and that the range of air to fuel ratio was very narrow at the speeds of rotation corresponding to the above normal speeds, namely at speeds ranging from 2500 to 3000 r.p.m. Such misfiring in deceleration was almost completely avoided by supplying air-fuel mixture of a proper mixing ratio according to the present invention. Further, the present invention can make improvements in atomization as well as mixing of fuel also in idling, in normal running or in acceleration.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

What is claimed is:

1. In an engine carburetor (1), including an elongated intake passage (2) terminating in an intake manifold (40), with a throttle valve (6) in said passage (2), an arrangement for controlling the air-fuel mixture during the deceleration of the engine, including an idle and lowspeed pneumatic by-pass circuit (9) opening into said air intake passage from below (8) said throttle valve therein, said arrangement comprising:

(a) having an additional pneumatic circuit (24) connecting a part of the air intake passage above the throttle valve (21) to a part of said passage below the throttle valve (22);

(b) a valve assembly (23) mounted in said additional pneumatic circuit having a vacuum responsive diaphragm therein;

(0) a branch line (26) between said idle and low-speed pneumatic circuit and said additional circuit above said valve assembly;

(d) biasing means (39) maintaining said valve assembly normally closed, said valve assembly being opened in response to a vacuum in said intake manifold (40);and

(e) at least one adjustable needle valve (25) for adjusting air flowing from said air intake passage above said throttle valve into said additional circuit.

2. An arrangement as claimed in claim 1 including an air inlet pipe for said additional circuit extending into said air intake passage.

3. An arrangement as claimed in claim 1, said branch line (26) having a needle valve (27).

4. An arrangement as claimed in claim 3, said valve assembly (23) including adjustment means (38) to adjust the biasing force of said biasing means (39).

5. A carburetor device for providing an air-fuel mixture in deceleration of an internal combustion engine having an idling and low speed circuit for the supply of an air-fuel mixture, said internal combustion engine including a carburetor with an air intake passage in the vicinity thereof, said air-intake passage having a throttle valve therein, an additional circuit having needle valves both for air and air-fuel passage, said additional circuit communicating between a part of the air intake passage upstream of the throttle valve and a part of the air intake passage downstream of the throttle valve, a valve assem- 5 6 bly mounted in the additional circuit, the idling and low- 2,824,726 2/1958 Dietrich ct a1. speed circuit being branched off into a part of the addi- 3,146,844 9/1964 Carlson. tional circuit above said valve assembly, said valve as- 3,374,991 3/1968 Walker. sembly being normally closed and being opened in de- 3,408,054 10/1968 Walker. pendence upon a vacuum condition downstream of the 5 throttle. TIM R. MILES, Primary Examiner References Cited UNITED STATES PATENTS US. Cl. X.R.

2,386,340 10/1945 Olson. 10 123-97; 26l-63, 69

2,621,911 12/1952 Lindsteadt.