US3877448A

US3877448A - Carburetors for internal combustion engines

Info

Publication number: US3877448A
Application number: US431781A
Authority: US
Inventors: Werner Schmid
Original assignee: BREVEST ET D ETUDES S I B E SO
Current assignee: BREVEST ET D ETUDES S I B E SO; Industrielle De Brevest Et D'etudes Sibe Ste
Priority date: 1972-04-10
Filing date: 1974-01-08
Publication date: 1975-04-15
Anticipated expiration: 1992-04-15
Also published as: DE2366005A1; FR2214048B2; DE2313520A1; FR2180160A5; IT985621B; GB1432016A; US3934571A; FR2214048A2; AU5414873A; AU472721B2; DE2366005C2

Abstract

A carburetor has a main fuel jetting system which opens in the intake pipe upstream of the throttle and an auxiliary device for cold start which comprises a conduit for delivering a fuel mixture of predetermined richness to the intake pipe. A valve actuated responsive to the temperature of the engine coolant or lubricant moves from a position for which the conduit is open to a position where it closes the conduit when the engine reaches its normal operating temperature. In addition, a choke valve located upstream of the main fuel jetting system is controlled by a temperature responsive member which maintains it in a minimum opening position when the engine is cold and opens it shortly after start.

Description

United States Patent Schmid Apr. 15, 1975.

[ CARBURETORS FOR INTERNAL 3,361,416 1/1968 Morgan et a1. 261/39 13 COM S ENGINES 3,670,709 6/1972 Eckert 261/39 D 3,706,444 12/1972 Masak1etal..... 123/119 F Inventor: Werner schmld, Esslmgen, 3,763,837 10/1973 Orlando 123/119 F Germany [73] Assignee: Societe Industrielle de Brevest et Primary Exami'fer wenden Bums dEtudes S.I.B.E., Neuilly-sur-Seine, 48mm"! Exammer-D Reymlds France Attorney, Agent, or FzrmStevens, Davis, Miller &

Mosher [22] Filed: Jan. 8, 1974 [21] Appl. No.: 431,781 [57] ABSTRACT A carburetor has a main fuel jetting system which [30] Foreign Application Priority Data opens in the intake pipe upstream of the throttle and J H 1973 France 73 00950 an auxiliary dev1ce for cold start whlch compnses a conduit for delivering a fuel mixture of predetermined [52] U S Cl "3/119 23/1 19 123/l79 richness to the intake pipe. A valve actuated respon- 261/39 261/39 sive to the temperature of the engine coolant or lubril t C] 1 "10 cant moves from a position for which the conduit is [58] i F T open to a position where it closes the conduit when le 0 earc "56 D 39 the engine reaches its normal operating temperature. In addition, a choke valve located upstream of the main fuel jetting system is controlled by a temperature [56] References cued responsive member which maintains it in a minimum UNITED STATES PATENTS opening position when the engine is cold and opens it 2,981,245 4/1961 Sarto 123/119 F shortly after start, 3,198,185 8/1965 Wastas 123/119 F 3,246,886 4/1966 Goodyear et al 123/119 F 4 Clams, 2 Drawmg Figures PATENTEUAPR] 519. 5

SHEET 1 0f 2 CARBURETORS FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION The invention relates to carburettors for internal combustion engines comprising. in addition to a main fuel jetting system for the normal operation of the engine. which opens into the intake pipe upstream of a main throttle member actuated by the operator. an auxiliary starting device for cold starting. The auxiliary starting device is adapted to deliver a flow-rate of fuel (and possibly a flow-rate of air) into the intake pipe in addition to the flow-rate necessary for hot idling of the engine. and is directly or indirectly responsive to the temperature of the engine.

A starting device is known which consists of a starting or choke valve located in the intake pipe upstream of the main fuel jetting system. The choke valve is rotatable about an eccentric axle so that it opens under the effect of the air flow which passes into said pipe. against the action of a return spring. and it increases the underpressure prevailing at the mouth of the main jetting system and. consequently, the richness of the air/fuel mixture admitted to the engine as long as the latter has not reached a minimum temperature.

Now regulations exist which are intended to limit atmospheric pollution and impose that the flow-rates of air and fuel in the carburettor be more and more accurately metered, especially when starting a warm engine. that is to say an engine whose temperature is at least equal to about C but substantially less than the normal operating temperature of the engine. In order that a warm engine may be started and rotate at low speed. the richness of the air/fuel mixture which it receives must be slightly increased with respect to the richness corresponding to the normal running temperature of the engine. that is when the engine is hot. it is difficult to determine this slight enrichment by means of the starting valve since a slight error in the angular position of this valve involves a large modification of the richness of the slow speed mixture. and this all the more as the flow-rate of air at slow speed (idling) is smaller.

Another type of starting device is known which consists of a distributor adapted. as long as the engine has not reached its normal operating temperature. to open a passage which receives a mixture of air and of fuel in well determined proportions and which opens into the zone of the intake pipe of the carburettor situated downstream of its principal throttle member. However the enrichment of the mixture determined by a starting device of the second type diminishes when the load on the engine increases and in particular it is difficult to obtain a sufficiently rich mixture for full load operation of an engine at very low temperature.

It is an object of the invention to provide a carburettor which delivers a mixture whose richness is well adapted to the temperature ofthe engine. whatever the condition of the latter from start.

SUMMARY OF THE INVENTION The carburettor has a starting device which comprises closure valve means adapted, as long as the engine has not reached its normal operating temperature. to open a passage which receives a mixture of air and of fuel in predetermined proportions and which opens into the zone of the intake pipe situated downstream of its principal throttle member and a starting valve situated in the intake pipe upstream of the principal jetting system. the starting valve being held sufficiently open. when the engine is warm. not to substantially enrich the air/fuel mixture on slow' speed running and at very small engine loads. The starting or choke valve is controlled by a first element sensitive to temperature which is arranged to be rapidly heated up and the closure valve means is controlled by a second element sensitive to temperature which is arranged to be heated up slowly. so that the choke valve is put out of action before the closure valve means as the engine heats up.

In this way. when the engine is cold. the enrichment is determined both by the closure valve means and by the starting valve. When the engine is warm. the enrichment is determined essentially by the aforesaid valve means. Finally. when the engine is hot. both starting devices no longer act on the richness of the mixture. The choke valve is caused to open completely soon after the starting of the engine and the enrichment of the mixture which is necessary on cold operation then is due to the action of the closure valve.

The first element may be exposed to the temperature of an electrical resistance which is supplied from a voltage source on starting of the engine and the second element is exposed to the temperature of the lubricant or cooling fluid of the engine.

SHORT DESCRIPTION OF THE DRAWINGS The invention will be better understood from the de scription which follows of a particular embodiment. The description refers to the accompanying drawings, wherein:

FIGS. 1 and 2 show, in diagrammatic elevation with portions cut away. a carburettor constructed according to an embodiment of the invention, in which the posi tions of the elements correspond respectively to cold operation and to normal operation of the engine.

DESCRIPTION OF A PREFERRED EMBODIMENT The carburettor comprises an intake pipe 1 in which is arranged. upstream of a principal throttle member (or butterfly valve) 2 actuated by the driver. an eccentric starting valve 3 tending to open under the effect of the air flow in the pipe 1 against a return force transmitted through a link rod 4 to a lever 5, secured to the axle 6 ofthe valve 3. That construction is similar to that described in patent application Ser. No. 346.477 assigned to the assignee of the present invention and the content thereof is included in this application by way of reference.

A fuel jetting device 67 opens in the pipe 1 at the level of a venturi 68, downstream of the valve 3. The air intake 69 of the pipe I is connected to the portion of the pipe I situated downstream of the butterfly valve 2, in addition to the direct path. by a circuit comprising along the direction of the air stream. an air passage 70, provided with a calibrated restrictor or orifice 71, a chamber 72 and a passage 73 which connects the chamber 72 to the pipe 1 downstream of the butterfly valve 2. The chamber 72 is supplied with emulsified fuel through a passage 74 from a well 75 whose lower portion is connected. through a passage 76 with a calibrating orifice 77, to a float chamber 78. A float 79 regulates the introduction of fuel into the chamber and maintains a constant liquid level in the chamber 78. A tube 80 dips in the well 75 and is formed with orifices 81 situated below the level N. Tube 80 is supplied with air from the air intake 69 through calibrated orifices 82 and 83 located in series relation.

To control the flow-rate in the passage 73., there is inserted into the chamber 72 a casing 84 provided with connectors 85 and 86 for the cooling fluid of the engine to flow in the chamber. The casing 84 locates an element 87 responsive to the temperature of the fluid; element 87 may have a closed container locating a body of a material which undergoes a variation in volume as a function of temperature. thereby moving a stem 88. The element 87 is held in position by a nut 89. The connection between element 87 and casing 84 is rendered fluid tight by a sealing gasket 90. A spring 91, supported on the end wall of the casing, exerts on a washer 92 a resilient force which opposes forward movement of the stem 88. A frusto-conical valve member 93, slidably mounted on the stem 88, is biased into abutting engagement with the washer 92 by a spring 94. The valve 93 is adapted for sealing engagement with a seat 95 located between an inlet orifice 96 and an outlet orifice 97 which communicate respectively with the chamber 72 and with the passage 73. O-ring 98 sealingly separates the casing 84 and the carburettor and prevents direct flow between the chamber 72 and the passage 73. A cover plate 99 closes casing 84.

The valve 3 is controlled by an element sensitive to temperature which is heated by an electrical resistor 100 when an electrical current flows in the latter responsive to closure of a switch or contactor 101. That contactor may be coupled with the ignition contact of the engine. for simultaneous closure. The element may be a bimetallic spiral strip 102 one end 103 of which is stationary and the other end 104 of which is connected to an axle 105. Axle 105 carries a lever 106 to which the link rod 4 is connected.

The valve 3 is also actuatable through conventional means by a pneumatic device (not shown), which is sensitive to the pressure prevailing in the intake pipe 1 downstream of the butterfly valve 2.

The device operates as follows:

When the engine is started at low temperature (FIG. 1). the choke valve 3 is in its minimum opening position. The contactor 101 is closed and the resistor 100 heats the bi-metallic element 102 which unwinds and progressively opens the valve 3 through levers and 6 and link rod 4. As it opens, the valve 3 reduces the underpressure which prevails at the mouth of the main fuel jetting device 67 and there is thus obtained a fast reduction in the richness of the ca'rburetted mixture in the main circuit since the heating up of the bi-metallic element 102 can be fast, within a time period whose length depends on the outside temperature. Since the cooling fluid of the engine remains cold for some time after starting. the temperature of element 87 is low and the stem 88 is in the position of FIG. 1 and retains the valve 93 out of engagement with seat 95. Air therefore flows through the passages 70 and 73 and the underpressure. created in the chamber 72 by the calibrated orifice 71, causes a fuel-air emulsion to flow through the passage 74. There is thus obtained the additional air/fuel mixture which is necessary for correct operation of the engine as long as it has not reached its normal operating temperature.

When the element 87 has heated up. the projecting length of the stem 88 increases and the available crosssection between the valve 93 and its seat 95 diminishes.

By selecting the calibrated

orifices

77, 83 and 71 appropriately, the richness of the air/fuel mixture delivered to pipe 1 through the passage 73 may be made to decrease in proportion to the flow-rate of air in passage 73. that is on the heating up of the element 87. This heating. which depends on the rise in temperature of the cooling fluid flowing in the casing 84 through the connectors and 86, is generally fairly slow. Due to the invention, it is hence possible to obtain, during cold operation of the engine. an enrichment of the carburetted mixture which is important for starting and initial operation. which then decreases rapidly by a predetermined amount soon after starting, then which decreases slowly by an additonal amount until the normal operating temperature of the engine is reached.

When the engine is hot (FIG. 2). the stem 88 overcomes the force of spring 91 and moves the washer 92 forward and the spring 94 holds the valve 93 on it seat 95. The stem 88 can continue to elongate by sliding through the valve 93 without being subjected to excessive stresses. There is thus obtained an automatic starting and cold operation device, which enables great flexibility in adjustment of the carburetted mixture.

What I claim is:

l. Carburettor for an internal combustion engine.

comprising: an intake pipe; an operator actuatable main throttle member in said pipe; a main fuel jetting system which opens into said pipe upstream of said th'rottle member for providing fuel to the engine during operation thereof under load; and an auxiliary cold starting device responsive to the temperature of the engine to increase at least the flow rate of fuel delivered to the intake pipe, said auxiliary device including a passage which opens into said intake pipe downstream of the main fuel jetting system, a closure valve in said passage. means for delivering an air fuel mixture of predetermined richness to said passage upstream of said closure valve, first temperature responsive means for closing said closure valve when heated to a first predetermined temperature. a starting choke valve located in said intake pipe upstream of the main jetting system. and second temperature responsive valve actuating means for moving said starting choke valve from a min imum opening to a more broadly open position when heated to a second predetermined temperature. wherein said temperature responsive means are constructed and arranged for the choke valve to be moved from its minimum opening position before the closure valve is closed following starting of the engine.

2. Carburettor according to claim 1. wherein the starting choke valve actuating means are arranged for immediate heating thereof following starting of the engine while the means for actuating said closure valve are constructed and arranged to be heated at the same rate as the engine.

3. Carburettor according to claim 1, having an electrical resistor thermally associated with said choke valve actuating means and means for supplying electrical current to said electrical resistor upon starting of the engine.

4. Carburettor according to claim 3, wherein said second temperature responsive means are exposed to a fluid the temperature of which is modified by operation of the engine.

Claims

1. Carburettor for an internal combustion engine, comprising: an intake pipe; an operator actuatable main throttle member in said pipe; a main fuel jetting system which opens into said pipe upstream of said throttle member for providing fuel to the engine during operation thereof under load; and an auxiliary cold starting device responsive to the temperature of the engine to increase at least the flow rate of fuel delivered to the intake pipe, said auxiliary device including a passage which opens into said intake pipe downstream of the main fuel jetting system, a closure valve in said passage, means for delivering an air fuel mixture of predetermined richness to said passage upstream of said closure valve, first temperature responsive means for closing said closure valve when heated to a first predetermined temperature, a starting choke valve located in said intake pipe upstream of the main jetting system, and second temperature responsive valve actuating means for moving said starting choke valve from a minimum opening to a more broadly open position when heated to a second predetermined temperature, wherein said temperature responsive means are constructed and arranged for the choke valve to be moved from its minimum opening position before the closure valve is closed following starting of the engine.

2. Carburettor according to claim 1, wherein the starting choke valve actuating means are arranged for immediate heating thereof following starting of the engine while the means for actuating said closure valve are constructed and arranged to be heated at the same rate as the engine.