US 3886917 A
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United States Patent 11 1 Nakada et al. 1 June 3, 1975 CARBURETOR WITH AUTOMATIC CHOKE 1,896,390 2/1933 Carter 123/119 F 2,094,165 9/1937 Bicknell.... 26l/52  Inventors: Masahllw Nakada? 2,134,421 10/1938 Sisson 123/119 F Matsumoto; Nobuyuki Kobayashi, 2,427,030 9/1947 Swigert 123/119 F all of Toyota, Japan 2,464,328 3/ 1949 Mallory 261/52 Assigneez Toyota Jidosha gy Kabushiki 2,977,100 3/1961 Carlson 261/52 Kaisha, Japan  Filed: June 5, 1973 Primary Examiner-Wendell E. Burns Attorney, Agent, or Firm-Toren, MCgredy & Stanger  Appl. No.: 367,220
 Foreign Application Priority Data  ABSTRACT July 13, 1972 Japan 47-69620 In a carburetor equipped with an automatic choke, the 123/119 261/39 C; 261/52 throttle valve and choke valve are linked through a  Int. Cl. F02m 1/10; F02m l/O2 Spring and link mechanism whereby the Opening f the Flew of Search 261/52, 39 C, 39 B, 39 R, choke is controlled in accordance with the position of 261/64 E; 123/119 F the throttle operating through changes in the spring tension of the interconnecting spring mechanism oc- References C'ted curring with the opening of the throttle.
UNITED STATES PATENTS 1,456,502 5/1933 Hartwell 261/52 1 Claim, 6 Drawing Figures PATENTEUJUNIS ms SHEET FIG. 2
THROTTLE OPENING- LARGE THROTTLE OPENING SMALL TIME PATENTEDJUN3 SHEET FIG. 6
02- mum ll O FULLY CLOSED -FULLY OPENED THROTTLE OPENING CARBURETOR WITH AUTOMATIC CHOKE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an automatic, choke of hot air type for automotive vehicles in which a thermostatic coil operates in response to air heated by the exhaust gas to control the choke valve, and more specifically the invention relates to a novel and useful carburetor equipped with such an automatic choking mechanism.
2. Description of the Prior Art Usually automotive engines during initial warm-up require a richer air-fuel mixture and hence a greater choking effect for idling or low-speed light-load operation than for the other phases of engine operation. It has, however, been difficult to attain an optimum choking effect for every phase of engine operation with conventional automatic chokes because they are generally so controlled that they open the choke valve in response to high intake-manifold vacuum.
The present invention has for its object the provision of a carburetor equipped with an automatic choke free of the foregoing disadvantage, which is designed so that when the throttle is partly open the force with which the choke valve is closed will be intensified so that an increased choking effect is achieved during idling or low-speed light-load operation.
SUMMARY OF THE INVENTION Briefly, the present invention may be described as a carburetor assembly which is equipped with an automatic choke and which includes a choke valve controlled by thermostatic means responsive to the exhaust gas temperatures of the vehicle upon which the carburetor is mounted, said exhaust gas temperatures being utilized for controlling operation of the choke valve. More particularly, the present invention comprises the improvement wherein a control system is incorporated into the carburetor assembly whereby the choke valve may be controlled in response to the position of the throttle valve as well as by the thermostatic control means. In the present invention, a link mechanism operating in conjunction with said thermostatic means operates to render said choke valve responsive to the po-' sition of the throttle valve. The link mechanism includes spring means operatively interconnecting the throttle valve and the choke valve to render the position of the choke valve dependant upon the position of the throttle valve. The spring means are positioned to effect a smaller choke opening with smaller throttle openings through variation in the tension of the spring means thereby enabling variations in the position of the throttle valve to influence the position of the choke valve.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a carburetor which an automatic choke embodying the present invention;
FIG. 2 is a view similar to FIG. 1, showing the carburetor during a different phase of its operation;
FIG. 3 is a characteristic curve of the operation of the embodiment shown in FIG. 1;
FIG. 4 is a side view of another embodiment of the invention;
FIG. 5 is a front view of the embodiment of FIG. 4; and
FIG. 6 is a characteristic curve of the operation of the embodiment shown in FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be better understood from the following detailed description taken in conjunction with the accompanying drawings showing preferred embodiments thereof.
Referring first to FIG. I, there is shown a carburetor body 1, a choke valve 2, a choke shaft 3, a throttle valve 4, and a throttle shaft 5. Levers 6, 7 and 8 are formed as a unitary member secured to the choke shaft 3. The lever 6 is connected to the outer end of a spiraled bimetallic spring or theremostatic coil ,9, the inner end of which is fixed to a theremostat housing 10. The lever 8 is connected to a connecting rod 11, the other end of which is connected to a vacuum piston (not shown) in a choke cylinder 12. A lever pin 13 is fixedly anchored in the thermostat housing 10, and a spring lever 14 is pivotally supported by the pin 13 for smooth turning motion. One end of the spring lever is connected to the lever 7 by a spring 15. The throttle shaft 5 fixedly supports a throttle lever 16, which in turn is linked to a push rod 17 through a connecting rod 18. A guide 19 is provided for the push rod, and a stopper 20 for the spring lever 14.
With the construction above described, the carburetor equipped with the automatic choke according to the present invention operates in the following manner. Before the engine warms up, the choke is kept opened in the position where three forces are in equilibrium. These forces are (l) the force with which the thermostatic coil 9 tends to close the choke valve 2, (2) the force with which the connecting rod 11 tends to open the choke valve 2 via the lever 8 in response to the manifold vacuum applied on the underside of the vacuum piston, and (3) the force with which the spring 15 tends to close the choke valve 2.
When the engine is idling or running at low speed under light load, the throttle is slightly open as shown in FIG. 1, and the push rod 17 turns the spring lever 14 clockwise. As the end of the spring lever 14 connected to the spring 15 moves downward, the urging of the spring 15 to close the choke valve 2 increases, with a consequent decrease in the opening of the choke valve.
With the increase of the engine load, as shown in FIG. 2, the throttle valve 4 opens wider, causing the throttle lever 16 to turn counter-clockwise and thereby bring the push rod 17 downward through the guide 19. As a consequence the spring lever 14 turns counterclockwise until it hits the stopper 20. With the spring lever 14 kept in this position, its end connected to the spring 15 is at a level higher than in FIG. 1. Naturally, the tendency of the spring 15 to close the choke valve 2 weakens, and the choke valve opens wider than in FIG. 1.
As will be appreciated from the foregoing, it is possible to change the tension of the spring 15 by operatively associating the spring lever 14 with the opening of the throttle so that, while the throttle opening is small, the force with which the choke valve 2 is closed is increased, and vice versa.
Thus, during gradual warm-up of the engine after start, as shown in FIG. 3, a greater choking effect is achieved while the throttle opening is small, with the choking effect being decreased with an increase of the throttle opening.
As noted above. according to this invention, a spring whose tension varies with the opening of the throttle is installed in a conventional carburetor equipped with an automatic choke, whereby the choke opening is limited and a good choking effect is attained while the throttle opening is small. This enables the engine to be supplied with a mixture of an adequate air-fuel ratio during the initial stage of idling just after a cold start or during idling operation or low-speed light-load operation before warm-up. In this way smooth engine operation is ensured. When the opening of the throttle is large enough to require only a small choking effect. the choke opening can be increased to lessen the choking effect and feed a leaner mixture to the engine thereby reducing the noxious contents of the exhaust emissions.
Another embodiment of the invention will now be described with reference to FIGS. 4 and 5, wherein like parts as used in FIGS. 1 and 2 are designated by like numerals. In this embodiment, a spring stop 21 is fixed to the choke shaft 3, and a choke arm 22 having a cylindrical part 22a is revolvably sleeved over the choke shaft 3. One end 15'a of a coil spring 15' is hooked on the stop 21, and the other end 15'b is hooked on a spring stop 22b of the choke arm 22. When the throttle and choke are in the positions shown in FIG. 5, the spring 15' is of such characteristic that it will not apply any force on the spring stop 21 and choke arm 22. A spring stop 23 is fixed onto the throttle shaft 5, and a throttle lever 16' having an arcuate slot 16a is revolvably mounted on the throttle shaft 5. One end 24a of a coil spring 24 stronger than the spring 15 is hooked on the spring stop 23, and the other end 2412 of the spring is hooked on a spring-stop recess l6'b of the throttle lever 16'. The throttle lever 16' and choke arm 22 are connected via a link 18. The lower end of the link 18' is engaged with the arcuate slot 16a of the throttle lever 16'. A stopper 25 is provided for the throttle lever 16'.
Before the engine starts, the opening of throttle valve 4 is small as shown in FIG. 5. The choke valve 2 is almost closed, and the choke arm 22, throttle lever 16', and link 18' are in the positions shown, the throttle valve 4 exerting no force at all on the choke valve 2.
As the throttle valve 4 in the carburetor of the foregoing construction is turned open counter-clockwise, a rotational force is exerted on the throttle lever 16 via the spring 24, thus also turning the throttle lever 16 in the same direction. Until the extremity of the slot 16'a of the throttle lever 16 comes into contact with the link 18', the throttle valve 4 will not exert force upon the choke valve 2. As the throttle valve 4 is further turned open counter-clockwise, the link 18' is pulled downward and the choke arm 22 is also turned counter-clockwise. Since the choke arm 22 and choke shaft 3 are connected via the spring 15, the choke shaft 3 is also subjected to the counter-clockwise rotational force. In other words, the choke valve 2 is subjected to a force that tends to move it to the open position. As the throttle opening is further increased, the force inducing the choke valve 2 to open is gradually increased. The throttle lever 16' continues to turn counter-clockwise until it hits the stopper 25, where it no longer turns but, because the throttle shaft 5 and throttle lever 16 are connected with the spring 24, further opening of the throttle valve 4 is not in the least constrained. After the throttle lever 16' has contacted the stopper 25, further opening of the throttle valve 4 will not increase the force urging open the choke valve 2. Thus, the relationship illustrated in FIG. 6 is established between the throttle opening and the opening of the choke with the aid of spring force.
From the foregoing it will be appreciated that, in accordance with the present invention, a choke opening conforming to the characteristic of a conventional carburetor with an automatic choke is attained when the throttle opening is relatively small and that a larger choke opening than with the conventional carburetor is obtained when the throttle opening is relatively large. For example, the second embodiment of the invention just described exhibits the characteristic graphically represented in FIG. 3.
While specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.
What is claimed is:
1. In a carburetor assembly having a throttle valve and equipped with an automatic choke including a choke valve, and thermostatic means responsive to exhaust gas temperature for controlling operation of said choke valve, the improvement including means for rendering operation of said choke valve dependent upon the position of said throttle valve, said improvement comprising, in combination,
a choke valve shaft connected with said choke valve to rotate concurrently with displacement thereof,
a throttle valve shaft connected with said throttle valve to rotate concurrently with displacement thereof,
a throttle lever revolvably mounted upon said throttle valve shaft,
a choke arm revolvably mounted upon said choke valve shaft,
means defining a slot in said throttle lever,
a linkage arm connected between said choke arm and said slot in said throttle lever,
a choke valve coil spring, concentrically located about said choke valve shaft and having a pair of ends, with one of said ends connected to impart a spring force to said choke valve shaft and with the other of said ends being connected to said choke arm, and
a throttle valve coil spring concentrically located about said throttle valve shaft and having a pair of ends, one of said ends being connected with said throttle valve shaft and the other of said ends being connected with said throttle lever.
said slot in said throttle lever being configured to impart a force from said throttle lever to said linkage arm only after said throttle lever has reached a predetermined position by displacement of said throttle valve beyond a predetermined location.