US3885425A - Automatic choke tester - Google Patents

Abstract

A vortex generator is connected to the automatic choke thermostatic spring housing in place of the usual exhaust manifold heat riser tube, which is disconnected for the first portion of the test. The generator supplies very cold air to the choke housing to immediately simulate cold weather operation and rotate the choke and cooperating operating mechanisms to a closed position. The cold source of air is then disconnected and either the hot source of air from the vortex generator then applied to open the choke, at which time the operation can be checked, or the choke is permitted to warm under the prevailing ambient temperature conditions. The simulated cold weather warm-up operation permits an accurate check of operation of all the choke components, that is, the fast idle cam, dechoke and piston pulldown mechanisms, and correlation of choke opening with winding and unwinding of the thermostatic choke coil.

Description

United States Patent Hughes et al.

1 May 27, 1975 AUTOMATIC CHOKE TESTER Primary Examiner-Jerry W. M yracle Attorney, Agent, or Firm--Robert E. McCollum; Keith L. Zerschling [73] Assignee: Ford Motor Company, Dearborn, [57] ABSTRACT Mich, A vortex generator is connected to the automatic choke thermostatic spring housing in place of the [22] Flled' June 1973 usual exhaust manifold heat riser tube, which is dis- [21] Appl, NO; 368,393 connected for the first portion of the test. The generator supplies very cold air to the: choke housing to im Related Apphcamm Data mediately simulate cold weather operation and rotate Dlvlslon f Sel'. N0. NOV. 3, Pat. No. the choke and cooperating perating mechanisms to 8 3308383" closed position. The cold source of air is then disconnected and either the hot source of air from the vortex [52] U.S. Cl 73/118; 62/5 generator then applied to Open the Choke at which hit. Cl. G01m /00 time the Operation can be checked, or the choke is [58] Fleld 0f Search 73/118; 62/5; 251/310 permitted to Warm under the prevailing ambient i perature conditions. The simulated cold weather [56] References Cited warm-up operation permits an accurate check of oper- UNIT S ES PATENTS ation' of all the choke components, that is, the fast idle 2,448,206 8/1948 Bailey 251 310 x dechoke and piston pulldown mechanisms, and 2,737,028 3/1956 Machlonski.... 62/5 correlation of choke opening with winding and un- 2,819,590 1/1958 Green 62/5 winding of the thermostatic choke coil. 3,144,754 8/1964 Tilden 62/5 3 Claims, 7 Drawing Figures Z2 Z2 J6 i 7 0! a 8476 l J g, L X\\ 79 6 AUTOMATIC CHOKE TESTER This is a division of application Ser. No. 303,557, filed Nov. 3, 1972, now U.S. Pat. No. 3,808,883.

This invention relates, in general, to an automatic choke for use with an engine mounted carburetor. More particularly, it relates to a choke tester and a procedure for checking the operativeness and accuracy of operation of an automatic choke without alteration of the choke structure or removal of the choke from the carburetor.

Because an automobile engine is designed and tuned for normal operation at an elevated temperature, some auxiliary control of the air/fuel mixture and fuel metering is required for proper idling performance during the initial warming-up period following a cold start. The automatic choke mechanism performs these functions by simultaneously positioning both the choke plate or butterfly valve for the correct air flow restriction at the carburetor and the throttle linkage for proper fuel delivery rate. Engine temperature and intake manifold vacuum are used as input signals to control the mechanical choke mechanisms.

The complexity of this task, however, is significantly increased by pollution control requirements. Therefore, the correct operation of the choke mechanism is very important to the smooth, efficient performance of an automobile engine.

As an illustration of automatic choke performance, consider the operation of a typical automatic choke in use today. On a cold engine, the choke plate will initially be firmly closed by a bimetallic coiled spring temperature sensor in the choke housing. When the engine is started, the vacuum in the intake manifold pulls downward on a piston to open the choke plate to a specific opening. No matter how cold the engine, this mechanism exerts sufficient force to overcome the bimetallic cold and open the butterfly valve slightly. Without this initial choke operation, the engine would not receive enough air to run.

As the engine warms, the exhaust manifold heats engine compartment air passing through a shroud or stove surrounding the manifold. This air is continuously pulled into the choke housing by the manifold vacuum through a heat riser tube. Gradually, the bimetallic coil is warmed. It expands with increasing temperature and increases the choke plate opening by allowing air to move open the choke plate or valve.

The fast idle cam is also attached to the choke shaft and rotates with the choke plate. This action controls the minimum throttle opening in discrete steps to provide the proper fuel delivery rates corresponding to the choke plate opening under any particular idling condition.

A dechoke mechanism is required for opening wide the choke valve by overriding the normal choke operation when a large quantity of air is required to accommodate large throttle openings. This device is simply a mechanical linkage between the throttle and the choke shaft. The dechoke is only engaged and actuated by the large throttle motion. When such a motion occurs, the choke plate is forced open to a particular position providing the proper dechoke clearance.

Currently, the performance survey of an automatic choke is a rather hit-or-miss procedure. As a result, the choke mechanism usually receives attention only when severe and obvious malfunctions occur. The choke seldom undergoes a routine inspection to insure satisfactory performance. However, the need for a relatively simple, quick and efficient device for analyzing and assessing choke performance has become pre-eminent.

The development of a reliable choke testing device would serve two important functions. It would supplement the capability available in automotive diagnostic centers as well as improve the ability of a mechanic to locate and repair faulty components in a malfunctioning choke.

A primary object of the invention, therefore, is to provide a test unit and diagnostic routine for comparing automatic choke performance with design requirements under simulated operating conditions.

The automatic choke tester of the invention facilitates choke performance analyses by rapidly duplicating the natural ambient conditions of temperature and pressure which are encountered during choke operation. It cools the choke to begin the test sequence under simulated cold engine conditions, irrespective of actual engine temperature. With the choke cool, examinations can be made of the pulldown mechanism performance, dechoke operation, and the fast idle cam position. The choke tester then may be used to apply heat to the choke assembly. At a certain preselected temperature level, the tester can regulate the choke temperature at a constant value while measurements are made of the choke plate angle and fast idle cam position.

To accomplish the above, the invention employs a high velocity vortex generator to separate an incoming compressed air stream into hot and cold outlets. In one embodiment, two valves are used, an inlet valve regulating the total flow rate from the compressed air line through the vortex generator, and a hot outlet valve adjusted to obtain optimum hot or cold outlet temperatures. The hot and cold outlets are alternately connected to the choke heater tube inlet. In another embodiment, only one sleeve valve is needed.

A further object of the invention, therefore, is to provide an automatic choke tester and method of testing an automatic choke that utilizes a vortex generator to separate a source of compressed air into colder and hotter fractions, apply the colder and hotter fractions alternately to the choke to quickly cool the choke and- /or subsequently warm it faster than it would be warmed by the engine ambient temperature alone so that all of the various functions and operations of the choke structure can be checked for operativeness and accuracy of operation.

Other objects, advantages and features of the invention will become more apparent upon reference to the succeeding detailed description thereof, and to the drawings illustrating the preferred embodiments thereof; wherein;

FIG. 1 illustrates somewhat schematically a crosssectional view of a carburetor having an automatic choke connected to the tester embodying the invention;

FIG. la and lb are enlarged schematic crosssectional views taken, respectively, on planes indicated by and viewed in the directions of the arrows la-la and lb-1b of FIG. 1;

FIG. 2 is a side elevational view of a modified form of the vortex generator shown in FIG. 1;

FIG. 2a is an enlarged cross-sectional view of the FIG. 2 construction;

FIG. 2b is a cross-sectional view taken on the plane indicated by and viewed in the direction of the arrows 2b2b of FIG. 2a; and,

FIG. is an enlarged cross-sectional view taken on a plane indicated by and viewed in the direction of the arrows 2c2c of FIG. 2a.

FIG. 1 is a cross-sectional view obtained by passing a plane through approximately one-half of a known type of four barrel, downdraft type carburetor. The portion of the carburetor shown includes an upper air horn section 12, an intermediate main body portion 14, and a throttle valve flange section 16. The three carburetor sections are secured together by suitable means, not shown, over an intake manifold indicated partially at 18 leading to the engine combustion chambers.

Main body portion 14 contains the usual air-fuel mixture induction passages 20 having fresh air intakes at the air horn ends, and connected to manifold 18 at the opposite ends. The passages are each formed with a main venturi section 22 containing a booster venturi 24 suitably mounted for cooperation therewith, by means not shown.

Air flow through passages 20 is controlled in part by a choke valve 28 fixedly mounted on a shaft 30 rotatably mounted on side portions of the carburetor air horn, as shown. Flow of fuel and air through each passage 20 is controlled by a conventional throttle valve 36 fixed to a shaft 38 rotatably mounted in flange portion 16. The throttle valves are rotated in a known manner by depression of the vehicle accelerator pedal, and move from an idle speed position essentially blocking flow through passage 20 to a wide open position essentially at right angles to the position shown.

The rotative position of choke valve 28 is controlled in a known manner by a semi-automatically operating choke mechanism 40. The latter includes a hollow housing portion 42 that is formed as an extension of the carburetor throttle flange. The housing is apertured for supporting rotatably one end of a choke lever operating shaft 44, the opposite end being rotatably supported in a casting 46. A bracket or lever portion 48 is fixed on the left end portion of shaft 44 for mounting the end of a rod 52 that is pivoted to choke valve shaft 30. It will be clear that rotation of shaft 44 in either direction will correspondingly rotate choke valve 28 to open or close the carburetor air intake, as the case may be.

An essentially L-shaped thermostatic spring lever 54 has one leg 56 fixedly secured to the opposite or righthand end portion of shaft 44. The other leg portion 58 of the lever is secured to the end 59 of a coiled thermostatic spring element 60. The opposite end portion 62 of the spring is fixedly secured on the end of a nipple 64 that is formed as an integral portion of a choke cap 66 of heat insulating material. Nipple 64 is bored as shown to provide hot air passages 68 and 70, passage 68 being connected to an exhaust manifold heat stove, for example. Cap 66 is secured to housing 42 by suitable means, such as the screw 72 shown, and defines an air or fluid chamber 74 within the two.

As thus far described, it will be clear that the thermostatic spring element 60 will contract or expand as a function of the changes in ambient temperature conditions of the air entering tube 68, or, if there is no flow, the temperature of the air within chamber 74. Accordingly, changes in ambient temperature will rotate the spring lever 54 to rotate shaft44 and choke valve 28 in one or the other directions, as the case may be.

The leg 56 of spring lever 54 is pivotally fixed to the rod 76 of a piston 78. The latter is movably mounted in a bore 79 in housing 42. The under surface of piston 78 is acted upon by vacuum in a passage 80 that is con- 7 nected to the carburetor main induction passages 20 by a port 82 that is located just slightly below throttle valve 36. Piston 78, therefore, is always subject to the vacuum existing in the intake manifold passage portion 18.

As is known, a cold weather start of a motor vehicle requires a richer mixture than a warmed engine start because considerably less fuel is vaporized. Therefore, the choke valve is shut or nearly shut to admit less air. Once the engine does start, however, then the choke valve should be opened slightly to lean the mixture to prevent engine flooding as a result of an excess of fuel.

The known choke mechanisms described automatically accomplish the action described. That is, on cold weather starts, the temperature of the air in chamber 74 will be low so that spring element 60 will contract and rotate shaft 44 and choke valve 28 to a closed or nearly closed position, as desired. Upon cranking the engine, vacuum in passage 80 will not be sufficient to move piston 78 to open the choke valve. Accordingly, the engine will be started with a rich mixture. As soon as the engine is running, high vacuum in passage 80 now moves piston 78 downwardly and rotates shaft 44 a slight amount so that choke valve 28 is slightly opened to admit more air to induction passage 20. Shortly thereafter, the exhaust manifold stove air in line 68 will become progressively warmer and cause choke element 60 to unwind and rotate shaft 44 and choke valve 28 to a more open position. 84 represents a conventional fast idle cam fixed on choke shaft 44. It would include a cylindrical hub with a stepped cam face projecting radially from one side, and a weighted lever segment projecting from the opposite side. The weighted lever would cooperate with a throttle stop or screw (not shown) adjustably mounted on a lever (also not shown) that would be fixed to throttle valve shaft 38. The end of the screw would be biased by the throttle valve return spring against the stepped cam face of the fast idle cam during idle to control the idle speed position of the throttle valve. As the temperature increased, the coil 60 would rotate the fast idle cam to position other lesser steps in the path of the throttle shaft screw, to progressively decrease idle speed until it reached the normal level at normal engine operating temperature.

Further details of construction and operation are not given since they are known and believed to be unnecessary for an understanding of the invention.

As stated previously, to test the automatic choke operation for accuracy of performance and operability, the passage 68 leading to choke chamber 74 is adapted to be connected to a source of cold air to simulate cold operation of the choke even though the engine operating temperatures and ambient temperatures surrounding the choke normally would not condition the choke for cold operation. The passage 68, in this case, is shown connected to a flexible tube 68a. This tube normally would be connected to the exhaust manifold heat stove, but to test the choke would be reconnected to the cold outlet of a vortex generator 92.

In general, the vortex generator per se could be of a known type similar to that shown and described in U.S. Pat. No. 2,581,168, A. Bramley. More specifically, the

vortex generator includes a cylindrical vortex chamber 94 of a predetermined diameter having a tangential air inlet 96 (FIGS. 1a and 1b). The inlet receives compressed air therein from any suitable source, not shown. The compressed air would be controlled by an on-off valve 98.

As best seen in FIG. 1, the vortex generator has two axial outlets of differing diameters smaller than the diameter of the vortex chamber. Cold air flows from the vortex chamber 94 through the smaller outlet tube 90, while the hotter air flows axially in the opposite direction through the larger diameter tube 100. An on-off progressive control valve 102 of a known type may be used to control the hot outlet 100.

The vortex generator operates in a known manner as fully described in the Bramely patent. In brief, compressed air enters vortex chamber 94 in a tangential direction to swirl centrifugally therein and separate the flow into colder and hotter fractions. The colder portion flows along the axis through the smaller diameter tube 90 to the choke housing tube 68a, while the hotter fraction flows peripherally along the walls of the larger tube 100 in the opposite direction past the valve 102. Adjustment of valve 102 to restrict or permit freer outlet of the hot air controls the proportion of hot to cold sources of air.

When it is desired to test the choke 40 for operativeness and accuracy of operativeness, under cold weather simulated conditions, the flexible tube 68a emanating from the choke 40 will be disconnected from the engine exhaust manifold heat stove, not shown, and connected to the cold outlet 90 of the vortex generator 92, as shown. Immediately, the air in chamber 74 of the choke 40 will become quite cold, in the neighborhood of 0F., or less, for example. This will immediately cause the thermostatic spring 60 to contract and rotate the choke valve 28 to a closed position to simulate cold weather operating conditions even though the ambient temperature around the choke may be quite high.

Once the choke valve has been rotated to the closed position, the tube 680 then can be disconnected from the choke and either again connected to the exhaust manifold heat stove to again apply engine heat, or kept disconnected and the choke chamber 74 allowed to slowly rise to ambient temperature conditions. Alternatively, the tube 68a can be connected to the hot outlet end 100 of the vortex generator 92 so that the temperature conditions in chamber 74 of the choke can be brought back to warm engine operating conditions.

Under any of the conditions outlined above, initially, when the choke valve is closed, the positions of the fast idle cam 84 can be checked for accuracy of position, the pulldown piston 78 can be operated against the tension of spring 60 to check the initial opening of the choke valve, and the dechoking mechanism, not shown, can be operated to see that it is satisfactory.

For all of the above operations, as the thermostatic spring 60 is subjected to the warmer air, it progressively unwinds and, therefore, slowly rotates the choke valve 28 in a progressive manner to an open position. During this time, the degree of opening of the choke valve with changes in temperature can be checked for correlation to see if the choke is operating correctly. 1

It will be seen from the above, therefore, that the invention provides a simple procedure for checking the cold operation of a choke under simulated cold weather operating conditions regardless of the actual ambient and engine operating temperatures. The invention can provide a source of very cold air, for example 50F., or a much hotter temperature, for example, 250F., that can be quickly connected to'the choke housing to simulate both temperature and pressure conditions of the choke under both cold and hot engine operating conditions.

FIG. 2 illustrates a modified construction of the vortex generator shown in FIG. 1. More particular, FIG. 2 shows a sleeve valve type construction requiring only a single outlet instead of the dual hot-cold outlets of the vortex generator shown in FIG. 1. The FIG. 2 construction alternates the discharge of hot or cold air merely by rotating the sleeve valve to its various operative positions. It also includes a vent position in which neither hot nor cold air is connected to the outlet, but both are vented to the atmosphere.

More specifically, FIGS. 2a, 2b and 2c show the detailed construction of the vortex generator. It consists of a stepped diameter main body on which is slid ably mounted a sleeve 112. The sleeve contains a pair of through-ports 114 interconnected by a passage 116. A third through-port 118 is fitted to an adapter 120 and constitutes the main outlet of the vortex generator. The port 118 is connected by a transfer conduit 122 to an internal port 124.

The stem end 126 of main body portion 110 contains a recess or bore 128 that threadedly receives an air compressor inlet fitting 130. More particularly, a hollow adapter 132 would be connected at one end 134 to a suitable source of compressed air, not shown. Its other end is received in the recess 135 of a plug having an angled passage 136 connecting the recess to the outer peripheral portion 138 of an annular chamber 140. The chamber contains a vortex generator 92 consisting of a disc 142 (FIG. 20) having a plurality of equally circumferentially spaced tangential inlets 144 for the passage of air in inclined passage 136 inwardly into an annular vortex chamber 146 in a manner similar to that described in connection with the FIG. 1 embodiment 94.

The vortex generator in this case is fixed to a larger diameter disc 148 having a central opening 150 and formed integrally with a tube 152. The tube 152 extends through a multi-diameter opening 154 in the right hand end of main body member 1 10 to a point adjacent the opposite end, which is closed by a plug 156. A second tube 158 surrounds tube 152, which terminates slightly short of the end of tube 158. This is so any air in tube 152 will flow out of and around the end 160 of the tube and through the passage 161 formed between tubes 158 and 152. A pair of different diameter passages 162 and 164 connect with the passage 162 and each pass outwardly to the sleeve 112, for a purpose to be described.

Returning now to the vortex generator, the outer chamber 140 is sealed by an. annular rubber or elastomer ring 167 that is assembled between the disc 148 and the inner end of the plug 130. This causes all incoming compressed air in inclined passage 136 to be confined within the annular passage 140 for passage tangentially into vortex chamber 146 through the inlets 144. The plug 130 also contains an axial bore 170 that has a radial connection 172 to a cooperating port 174. The port opens to the outer periphery of the main body portion and contains a phenolic or plastic plug 176. The plug has a predetermined diameter cold air outlet 7 opening 178 communicating with the interior of vortex chamber 146.

It will be seen, like the construction shown in FIG. 1, that the vortex chamber has two outlets of different diameters and each of a smaller diameter than the vortex chamber 146 for passage of hot and cold air from the vortex generator through the tubes 152 and bore 170, respectively.

In operation, the main outlet 120 is adapted to be connected alternately to the source of colder air in bore 170 by way of passages 174 and 122, or to the hotter air source in tube 152 and passage 161 through the connecting conduit 164. Alternatively, both the hot and cold sources can be vented to atmosphere by connection through a vent 180 shown in FIG. 2b.

The lower portion of the sleeve 112 is provided with an arcuate groove 178 that slidably receives a pin 179 fixed in a hole in the main body portion 110. As best seen in FIG. 2, the pin permits rotation of sleeve 112 relative to the main body portion 110 from a cold position through the vent position to the hot position. The compressed air entering inlet 134 then will depart by the outlet 120 either as the colder or hotter source, depending upon the position of the sleeve.

When the sleeve 112 is in the hot position shown in FIG. 2, the parts will be aligned as indicated in FIGS. 2a and 2b. The source of cold air in bore 170 will pass directly to the vent openings 114, while the smaller diameter hot conduit 162 will be connected to the main outlet 120, as shown. The larger diameter outlet 164 at this time will be blocked by being at an angular position out-of-line with both the outlet 120 and the vent 114.

When the sleeve 112 is rotated to align the arrow 186 with the vent position, the vent 180 shown in FIG. 2b will be aligned with the cold outlet port 174, and the hot outlets will both be blocked.

When the sleeve valve is rotated so that the indicator 186 is aligned with the cold position, the cold outlet port 174 will be aligned with the internal port 124 so that the cold air will pass directly to the main outlet 120. At this time, the hot, larger diametered conduit 164 will be connected to the vent port 114, while the smaller passage 162 will be blocked.

From the foregoing, it will be seen that the FIG. 2 embodiment provides a single valve that alternately connects the hotter or colder source to the single outlet 120. Therefore, merely by rotating the sleeve 112, the choke 40 can be subjected alternately to cold or hotter sources of air.

From the foregoing, it will be seen that the invention provides a quick and accurate method as well as structure for accurately checking the performance of an automatic choke under simulated cold or hot Weather operating conditions.

We claim:

1. A tester for a motor vehicle type automatic choke having a housing enclosing a temperature responsive member operatively connected to an unbalance mounted, air movable choke valve for urging the same towards a position closing the upper end of a carburetor induction passage in response to decreases in temperature level below a predetermined level and movable to a position opening the induction passage in response to airflow thereagainst through the passage, comprising in combination, a rotatable sleeve valve having an air outlet adapted to be connected to the choke housing and an air vent, the sleeve valve being rotatably mounted with respect to a second sleeve closed at its ends and received therein, a vortex generator mounted within the second sleeve and separated therefrom radially by an annular chamber, an air inlet at one end of the second sleeve connected to the annular chamber and adapted to be connected to a source of compressed air, the generator having a plurality of circumferentially spaced tangentially positioned air inlets admitting compressed air to annular interior chamber for swirl of air therein around the interior chamber, a pair of axially directed and located conduits extending in opposite directions and of different diameters less than the diameter of the interior chamber whereby the generator divides the incoming air into a source of colder air flowing in one direction through the smaller diametered conduit and a source of warmer air flowing through the larger diametered conduit, the second sleeve having port means therethrough connected respectively to the colder and warmer air sources, rotation of the sleeve valve to its extreme positions alternately connecting one source to the sleeve valve outlet while connecting the other source to vent, and vice versa, whereby the choke temperature sensitive means may be quickly cooled or heated by rotation of the sleeve valve to simulate choke actual operating temperatures regardless of ambient temperature conditions.

2. A tester as in claim 1, wherein the sleeve valve includes a further vent port, movement of the sleeve valve to an intermediate position venting the colder air source while blocking the warmer air source for no delivery of air through the air outlet.

3. A tester as in claim 1, including a baffle member in the warmer air conduit to disturb the flow and inter-

Claims (3)

1. A tester for a motor vehicle type automatic choke having a housing enclosing a temperature responsive member operatively connected to an unbalance mounted, air movable choke valve for urging the same towards a position closing the upper end of a carburetor induction passage in response to decreases in temperature level below a predetermined level and movable to a position opening the induction passage in response to airflow thereagainst through the passage, comprising in combination, a rotatable sleeve valve having an air outlet adapted to be connected to the choke housing and an air vent, the sleeve valve being rotatably mounted with respect to a second sleeve closed at its ends and received therein, a vortex generator mounted within the second sleeve and separated therefrom radially by an annular chamber, an air inlet at one end of the second sleeve connected to the annular chamber and adapted to be connected to a source of compressed air, the generator having a plurality of circumferentially spaced tangentially positioned air inlets admitting compressed air to annular interior chamber for swirl of air therein around the interior chamber, a pair of axially directed and located conduits extending in opposite directions and of different diameters less than the diameter of the interior chamber whereby the generator divides the incoming air into a source of colder air flowing in one direction through the smaller diametered conduit and a source of warmer air flowing through the larger diametered conduit, the second sleeve having port means therethrough connected respectively to the colder and warmer air sources, rotation of the sleeve valve to its extreme positions alternately connecting one source to the sleeve valve outlet while connecting the other source to vent, and vice versa, whereby the choke temperature sensitive means may be quickly cooled or heated by rotation of the sleeve valve to simulate choke actual operating temperatures regardless of ambient temperature conditions.

2. A tester as in claim 1, wherein the sleeve valve includes a further vent port, movement of the sleeve valve to an intermediate position venting the colder air source while blocking the warmer air source for no delivery of air through the air outlet.

3. A tester as in claim 1, including a baffle member in the warmer air conduit to disturb the flow and interrupt swirl motion.

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