JPS5821094B2 - Automatic choke device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to an automatic choke device for an automobile carburetor;
More particularly, the present invention relates to an automatic choke device that provides the same engine operation regardless of air density changes due to altitude changes.

Most commercial carburetor choke devices do not have a mechanism to compensate for changes in air density due to changes in altitude.

Therefore, when a motor vehicle equipped with a conventional choke device is driven at high altitudes or at altitudes above the choke calibration point, a rich air-fuel mixture will be introduced into the engine due to the dilution of the air.

Therefore, the amount of air used for mixing with fuel is small, resulting in a decrease in output and a decrease in engine acceleration.

Therefore, in order to obtain the same acceleration as at low altitudes, it is necessary to open the throttle valve widely.

. This will reduce the vacuum in the manifold compared to the value at the choke calibration ground level.

Looking at this problem from another perspective, the pressure of the air sucked in when the engine accelerates above sea level or above the choke calibration ground is 1 atmosphere or less.

Therefore, the differential pressure between the carburetor inlet and the engine combustion chamber will be less than the value at low altitude.

This also results in lower vacuum levels in the manifold at higher altitudes.

Most commercial carburetors close the choke valve when the ambient temperature drops below the engine's normal operating level.

It has a choke device with a built-in thermostatic bimetal coil spring that increases the force.

This provides a rich mixture during the final stages of engine operation, and gradually becomes leaner as the temperature rises.

In most designs, an exhaust system draws heated air toward a coil spring and exhausts it into a manifold, gradually reducing the force of the bimetallic spring to open the choke valve. ing.

However, as altitude increases, the hot air flow through the bimetallic spring decreases as the manifold vacuum decreases.

Therefore, the hot air that warms the bimetal to maintain the opening degree of the choke valve during the final stage of running is insufficiently drawn in.

For example, if an acceleration occurs at the altitude of the choke calibration site that would normally reduce the manifold vacuum to, say, 5 crfL (2 in) Hg, the higher the speed, the more the throttle valve must be opened wider to achieve the same acceleration. If not, this would reduce the vacuum in the manifold to near atmospheric pressure levels.

Therefore, the differential pressure between the hot air source and the manifold vacuum will be very small or zero, resulting in very little hot air flow to warm the bimetallic spring.

In this case, the choke valve would be in a closer position than it should be at that temperature, resulting in the engine running with a rich mixture that would cause the engine to stall.

It is therefore an object of the present invention to provide an automatic choking device with an altitude change compensation mechanism to provide essentially the same choking action independent of air density changes.

In accordance with the present invention, an automatic carburetor for use in an internal combustion engine having an air-fuel mixture guide passage open at one end and connected to a suction manifold at the other end and subjected to a varying manifold vacuum. A choke device, wherein the guide passage is rotatably mounted across the guide passage near the other end to prevent air passing through the guide passage.
a throttle valve movable to open and close the guide passage to control the flow of the fuel mixture, and the automatic choke device is rotatable across the guide passage near the one end; an unbalancedly mounted choke valve which is mounted and moves to open and close to control the flow of air toward the throttle valve; and an unbalanced mounted choke valve which is coupled to the choke valve and which operates as the temperature of the choke valve decreases from a predetermined level. Thus, a temperature-sensitive coil spring is coupled to the choke valve that urges the choke valve toward a closed position with increasing force and is responsive to the manifold vacuum to resist the coil spring and start. means for moving the choke valve from an initial closed position toward an open position in response to operation of the engine from a state to a running state, the means comprising a movable piston actuated by vacuum pressure; Then, one end of the coil spring is connected to the exhaust system of the engine to introduce hot air so as to transfer engine heat to the coil spring, and the other end is connected to the suction manifold to suck and discharge the hot air.
a heat source including a hot air passageway for warming a spring to reduce the force with which the coil spring acts to close the choke valve; an electrically controlled temperature sensitive heating device for moving the choke valve to further open the resulting opening of the choke valve, the temperature sensitive heating device being located near the power source and the coil spring; conducts its heat output to the coil spring to reduce the force of the coil spring to close the choke valve so that the choke valve is opened by the airflow flowing through the guiding passageway; a heater having a positive temperature coefficient (PTC); and a temperature sensitive switch that is activated when the surrounding air exceeds a predetermined temperature to connect the power source to the heater and heat the heater, The internal resistance of the heater when it exceeds
.

said heater increases to a predetermined resistance value that limits further heating beyond a predetermined temperature level, thereby preventing excessive heating of said coil spring; The temperature sensitive switch is connected in parallel with the power source.

a switch controlled by an engine manifold vacuum configured to bypass the temperature sensitive switch and heat the heater when ambient air is below a predetermined temperature; the switch controlled by the manifold vacuum; , closed by a spring.

The power supply and the heater are connected, and the manifold vacuum exceeding a predetermined vacuum level opens and disconnects the power supply and the heater, the predetermined vacuum level being such that at the predetermined vacuum level, , one end of which is connected to the exhaust system of the engine to heat it.

The pressure difference in a hot air channel introducing air and connecting the other end to the suction manifold to draw it out is sufficiently large so that sufficient hot air is applied to the coil spring to warm it. An automatic choke device is provided which is characterized in that it is of a level that allows for.

Other objects, features and advantages of the invention will become more apparent from the following detailed description, taken in conjunction with the drawings illustrating the embodiments.

FIG. 1 is a cross-sectional and elevational view of approximately one side of a well-known two-tube, downward draft type carburetor.

The illustrated carburetor includes an upper air horn section 12 and an intermediate body section 1.
4, and a throttle valve flange portion 16.

All three parts of the carburetor are fixed by suitable mechanisms onto the intake manifold (indicated in part at 18) leading to the engine combustion chamber.

The main body section 14 incorporates a conventional air-combustion mixture guiding passage 20 having an atmospheric inlet in the air horn section 12 and connected at the other end to the manifold 18.

Each passageway 20 has a main venturi portion 22 containing an auxiliary venturi 24 therein.

A portion of the air flow in passageway 20 is controlled by a choke valve 28 mounted unbalanced on a shaft 30 rotatably mounted to carburetor air horn section 12 as shown.

The fuel and air flow in each passage 20 is controlled by a throttle valve 36 (1) fixed to a shaft 38 rotatably attached to the flange 16
(Only shown).

Throttle valve 36 is rotated in a known manner by depression of an accelerator pedal to move it from an idle speed position essentially blocking flow in passageway 20 to a fully open position.

The rotational position of the choke valve 28 is controlled by an automatic choke device 40.

The choke device 40 includes a hollow housing 42 formed as an extension of the flange 16 .

The housing 42 includes a choke lever actuating shaft 44.
A hole is provided to rotatably support one end of the operating shaft 4.
The other end of 4 is rotatably supported in a hole in casing 46.

A bracket 48 is secured to the left end of the shaft 44 for attaching the end of the rod 52 to which the choke valve shaft 30 is attached.

The shaft 44 is connected to the choke valve 2 to open and close the air inlet of the carburetor.
8 in either direction.

L-type thermostat spring lever 54 (7) 1 piece 5
6 is fixed to the right end of the shaft 44.

Another leg 58 of the lever 54 is secured to the outer end 59 of the thermostatic coil spring 60 through an arcuate groove provided in the insulating gasket 64 .

Leg 56 is also pivotally secured to rod 76 of piston 78.

A piston 78 is movably disposed in a hole 79 in the housing 42 . The lower surface of the piston 78 is connected to the carburetor guide passage 20 at a port 82 slightly downstream of the throttle valve 36 .
It is designed to be pulled by the vacuum in the flow path 80 connected to.

Therefore, the piston 78 is always subject to the vacuum of the suction manifold 18.

The housing 42 includes a hot air passage 68 connected to, for example, an exhaust manifold heating stove.

The cylinder on which the piston 78 slides is provided with a bypass groove (not shown) in a well-known manner, so that the piston 7
The vacuum acting on 8 will cause hot air to flow from channel 68 to channel 80 .

Hot air enters around coil spring 60 through a hole in gasket 64 and exits through another hole into a bypass groove around piston 78.

The thermostatic coil spring 60 operates as a function of the temperature change due to the hot air exiting the hot air channel 68 and when there is no flow of hot air flowing through the hot air channel 68.
4. Contracts or expands as a function of the air temperature within the chamber.

Therefore, changes in environmental temperature will cause spring lever 54 to rotate, resulting in shaft 44 and choke valve 2 in either direction.
8 rotates.

As is well known, when starting a car at the end of its life, the vaporization rate of the fuel decreases considerably, so a richer air-fuel mixture is required than when starting in a warm season.

Therefore, the choke valve 28 is closed or nearly closed in order to reduce the pressure and draw in more fuel.

However, once the engine starts, it is necessary to slightly open the choke valve 28 to dilute the mixture to prevent excess fuel.

The choke valve 28 automatically counteracts the above operation 3, i.e.
At late start, the cooler air in chamber 74 causes coil spring 60 to contract and rotate shaft 44 and choke valve 28 to the desired closed or nearly closed position.

When starting the engine, the degree of vacuum in the flow path 80 is lower than that of the piston 7.
8 to open the choke valve 28.

The engine is therefore started with a rich mixture.

As soon as the engine is started, the degree of vacuum in the passage 80 becomes high, moving the piston 78 downward and slightly rotating the shaft 44, so that the choke valve 28 opens slightly and the amount of fuel flowing into the passage 20 is reduced.

Over a period of time, as the air in the exhaust manifold stove gradually warms, the hot air from the hot air flow path 68 causes the coil spring 60 to expand a little and rotate the shaft 44 and choke valve 28 to a more open position. become.

Further details of construction and operation are not described as they are well known and are considered unnecessary for an understanding of the invention.

FIG. 2 shows thermostatic coil spring 60 held centrally to metal post 84. FIG.

The post 84 is formed as part of an aluminum disk 85.

This disk 85 is a heat conductive member and uniformly radiates heat from a heating body (heater) 86 to the coil 60.

The ceramic flat disc-shaped heating element 86 has a positive temperature coefficient (PT
C).

It is fixed to a disc 85 and has a contact lug 88 provided in the center of a spring leg type conductive member.

The rack 88 projects through a hole in a wall 89 of the insulating cover 90.

The disk 85 is grounded by a ground terminal 92 through a cover 90 to the housing 42 made by casting.

Lugs 88 are adapted to occasionally engage the surface of bimetallic switch 94.

The switch 94 is comprised of an over-center spring and is sensitive to ambient temperature.

The switch 94 has a central hole from which a conductive lug 96 projects.

The lug 96 is secured to a spring leg type conductive member 98 which is connected to a terminal 100.

Terminal 100 is connected to a suitable power source, such as an alternator, so that current can be supplied to terminal 100 as long as the vehicle is being operated.

The insulating cover 90 also has a plug-in vacuum switch 102.
It is equipped with

The switch 102 has a pair of conductive contact prongs 10 on one side.
4, 106 has a hollow housing 103 that protrudes through it.

Prongs 104 extend through electrical sockets 107 in cover 90 to abut the back side of lug 96.

When bimetallic switch 94 is in the over-center position of FIG. 2, prongs 104 are spaced apart from lugs 96.

When switch 94 moves from this over-center position to the opposite over-center position, lug 96 contacts prong 104.

Prongs 106, in turn, are in contact with a conductive connector 110 fixedly connected to lug 88 through socket 108 to conduct electrical current to heating element 86 in a manner described below.

The hollow interior of the switch 102 is an annular flexible diaphragm 1
11 into an air chamber 112 and a vacuum chamber 113.

Conduit 114 connects at one end to chamber 113. The other end (not shown) is connected to a suitable manifold vacuum port similar to port 82, for example.

Air chamber 112 communicates with the atmosphere through a hole (not shown) in the housing of switch 102.

An electrically conductive contact bridge plate 116 is attached to the diaphragm 111 on the side of the air chamber 112.

A preload spring 118 in the vacuum chamber 113 is attached to the diaphragm 1
11 is pressed into a position such that the bridge plate 116 is brought into contact with the prongs 104 and 106.

The blade of the spring 118 is such that when the degree of vacuum in the vacuum chamber 113 reaches a degree of vacuum of at least 5 crrt (2 inches) at the height of the mercury column, the diaphragm 111 is pulled to the right side, and the prongs 104 and 106 are pulled out. is selected such that the circuit is opened.

The heating element 86 has a characteristic that the internal resistance increases rapidly from a predetermined temperature (Ts) as the surface temperature of the heating element 86 rises.

The internal resistance changes not in a linear relationship with the internal temperature of the heating element 86, but in a relationship as shown in FIG.

When positive temperature coefficient (PTC) heater 86 is electrically activated by applying voltage from an alternator to terminal 100 when switch 94 or 102 is closed, Joule heating causes PTC heater 86 to quickly develops a fever.

When heating from room temperature, the resistance of the heating element 86 is initially approximately constant.

When the temperature rises to a predetermined temperature (Ts), the resistance increases rapidly as shown in FIG.

Of course, the electrical characteristics can be adjusted by changing the chemical composition and manufacturing method of the heating element 86.

A heating body 86 made of such a semiconductor provides a high resistance to electric current at high temperatures, whereupon the highest temperature.

As shown in FIG. 3, it has the unique characteristic of maintaining its temperature.

Therefore, the need to provide a separate cut-off thermostat to prevent distortion of the coil spring 60 due to excessively high temperatures necessitates the use of such semiconductors in the heating element 86.
It disappears by using 4 as 4.

The PTC heating element 86 is connected to the switch 94 or switch 1
02 provides supplemental heat to the bimetallic spring 60 in addition to the heat provided by the hot air of the exhaust manifold.

When current flows through the heating element 86 of the PTC, a change in internal temperature occurs.

The heat generated in the heating element 86 is conducted from the post 84 to the spring 60 and from the disk 85 to the spring by radiation.

The internal temperature of the heating element 86 of the PTC is a predetermined temperature, that is, the third temperature.
When Ts shown in the figure is reached, the internal resistance becomes high and the current becomes extremely small and is essentially cut off.

Therefore, the heat of the PTC heating element 86 heated by the current is balanced by the heat loss from the heating element 86 to the surroundings and to the post 84.

Therefore, the heat of the PTC heating element 86 is maintained at a constant level.

Since the overall operation is believed to be clear from the above description and drawings, it will not be repeated in detail.

In summary, as shown in FIG. 2a, below an ambient temperature level of <18 DEG C. (65 DEG F.), bimetallic switch 94 moves to a position that pulls lug 96 end away from lug 88.

Therefore, at this point, the PTC heating element 86 is connected to the switch 9.
No current flows through 4.

At this temperature level, it may be necessary to open the choke valve 28 in order to provide a suitable mixture, in which case the choke valve 28 may need to be opened slowly in conjunction with the increase in engine temperature.
When it is desired to open the housing 4
This is achieved by gradually increasing flow of hot air from the exhaust manifold stove into the exhaust manifold stove.

Therefore, there is no need to heat the PTC heating element 86 at this point unless the hot air decreases below the minimum flow rate value.

However, due to the change in altitude as described above, the manifold vacuum decreases during acceleration of the automobile, and the hot air flowing through the aforementioned housing 42 to heat the coil spring 60 and open the choke valve 28 is not sufficiently sucked in. There are times when there is a small pressure difference.

Thus, when the manifold vacuum drops below 1, for example, 5 CrrLHg, the bridge plate 116 will close the prong 104.
Spring 118 presses diaphragm 111 to the left so as to contact 106 and 106 , closing switch 102 .

This causes current to flow to the PTC heating element 86, which provides heat to the coil spring 60 to compensate for the heat loss that would be insufficient to heat it with hot air from the exhaust manifold stove.

Thus, closing the vacuum switch 102 compensates for the lack of hot air from the exhaust manifold stove.

Therefore, until such time as the manifold vacuum rises again to a level sufficient to overcome the force of the springs 118 and separate the bridge plate 116 from the prongs 104 and 106, i.e., 5 crfLHg (when hot air flow is sufficient), the PTC Heating body 86
In order to heat the vacuum switch 102, the vacuum switch 102 replaces the open switch 94 by forming a circuit with 104, 116, and 106 that conducts current to the heating element 86.

It can be seen that the switch 102 is configured to operate whenever the manifold vacuum has fallen to a level insufficient to cause exhaust manifold stove hot air to flow into the housing 42.

Of course, the specific desired level can be adjusted by selecting the preload of spring 118.

From the perspective of exhaust gas regulations, 18°C (65°F) or higher.

Using only hot air from the exhaust manifold stove to open the choke valve 28 at the coil spring 6
0 heating rate is generally unsatisfactory because it is too low.

Thus, above 18°C (65°F), in Figure 2, '
As shown, switch 94 is moved to bring lug 96 and lug 88 into contact and heat PTC heating element 86.

This movement causes the spring leg of conductive member 98 to move to the left and away from prong 104.

Thus, the bimetallic coil spring 60° is heated by the hot air from the exhaust manifold stove plus the PT
The heat from the C heating element 86 causes the choke valve 28 to open at a faster rate than when controlled by hot air alone.

Thus, at temperatures above 18°C (65°F), the vacuum
It can be seen that switch 102 does not cause current to flow to PTC heating element 86 (switch 94 does this).

From the above description, it is clear that according to the present invention, whenever the manifold vacuum drops below a predetermined level, the bimetallic
It will be seen that a simple plug-in vacuum switch is provided which can be added to a conventional choke device to ensure that the coil spring is heated below a predetermined temperature level.

Therefore, for altitude changes where the manifold vacuum is at a low level and insufficient hot air is flowing into the housing, the bimetallic coil spring heating element can be energized from a separate circuit. This can be dealt with appropriately by providing a vacuum switch.

Although the invention has been described and described in one embodiment, it will be obvious that many changes and modifications may be made thereto without departing from the scope of the invention.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional elevational view of a part of a two-cylinder carburetor embodying the present invention, Fig. 2 is an enlarged detailed view of a part of Fig.
FIG. 3 is a graph illustrating the operating characteristics of the heating element, corresponding to the figure, but with the bimetallic switch moved to an operating position other than that shown in FIG. 12... Air horn part, 14... Main body part, 16... Throttle valve flange part, 18...
...Suction manifold, 20...Mixture induction passage, 22...Main venturi, 24...Auxiliary venturi, 28...Choke valve, 30...
...Shaft, 40...Choke device, 42...
... Housing, 44 ... Choke lever operating shaft, 48 ... Bracket, 52 ...
... Rod, 54 ... Lever, 60 ... Thermostat coil spring, 64 ... Insulation gasket, 68 ... Hot air flow path, 76 ... ...
...Rod, γ8...Piston, 79...
... Hole, 80 ... Channel, 82 ... Port, 84 ... Post, 85 ... Disk,
86... Heating body, 88° 96... Lug, 90... Insulating cover, 92... Grounding terminal, 94... Bimetal. switch, 98
... Conductive member conductor, 102 ... Vacuum switch, 104 , 106 ... Prong, 1
07,108...Socket, 110...
・Connector, 111...Diaphragm, 11
2... Air chamber, 113... Manifold vacuum chamber, 114... Conduit, 116...
Bridge plate, 118... Spring.

Claims (1)

[Claims] 1 Automatic choke device for use in internal combustion engine carburetors having an air-fuel mixture guide passage open at one end and connected to the suction manifold at the other end to be subjected to a varying manifold vacuum. wherein the guide passage is rotatably mounted across the guide passage near the other end and configured to open and close the guide passage for controlling the flow of the air-fuel mixture through the guide passage. a throttle valve that moves to control the flow of air toward the throttle valve; and the self-choking device is rotatably mounted across the guide passage near the one end and moves to open and close to control the flow of air toward the throttle valve. an unbalancedly mounted choke valve which moves to move the choke valve; and a choke valve connected to the choke valve and urging the choke valve toward a closed position with a force that increases as the temperature of the choke valve decreases from a predetermined level. a temperature-sensitive coil spring connected to the choke valve and responsive to the manifold vacuum to resist the coil spring and initially activate the choke valve in response to operation of the engine from a starting condition to a running condition; from a closed position to an open position, the means having a movable piston actuated by vacuum pressure and a movable piston connected at one end of the engine to conduct engine heat to said coil spring. The coil spring is warmed by connecting it to an exhaust device to introduce hot air and connecting the other end to the suction manifold to suck and exhaust the hot air, so that the coil spring acts to close the choke valve. a heat source including a hot air flow path for reducing the force exerted by the choke valve, and further comprising: an electric power source juxtaposed with the heat source for moving the choke valve further opening provided solely by the means; a temperature-sensitive heating device that is electrically controlled, the temperature-sensitive heating device being positioned near a power source and the coil spring to conduct its heat output to the coil spring to increase the temperature of the coil spring. a heater having a positive temperature coefficient (PTC) that reduces the force acting to close the choke valve so that the choke valve is opened by the air flow flowing through the guiding passage; a temperature sensitive switch that is actuated to connect the power source to the heater to heat the heater, the internal resistance of the heater when the predetermined temperature is exceeded to cause further heating beyond the predetermined temperature level; the coil spring is increased to a predetermined resistance value such as to limit the temperature of the coil spring, thereby preventing excessive heating of the coil spring; a switch connected in parallel with the engine manifold vacuum and configured to bypass the temperature sensitive switch and heat the heater when ambient air is below a predetermined temperature, the switch being controlled by the engine manifold vacuum; a switch controlled by a spring that closes to connect the power source and the heater and opens by manifold vacuum above a predetermined vacuum level to disconnect the power source and the heater; At the predetermined vacuum level, the predetermined vacuum level is the pressure of a hot air passage whose one end is connected to the exhaust system of the engine to introduce hot air, and whose other end is connected to the suction manifold to suck and discharge the hot air. An automatic choking device characterized in that the difference is of a level sufficiently large that sufficient hot air can be applied to said coil spring to warm it.