GB2037894A

GB2037894A - A Heated Intake Throttle Valve Assembly for an Internal Combustion Engine

Info

Publication number: GB2037894A
Application number: GB7944353A
Authority: GB
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1978-12-25
Filing date: 1979-12-24
Publication date: 1980-07-16
Also published as: JPS5594455U; FR2445447B1; FR2445447A1; JPS5843655Y2; DE2952375C2; DE2952375A1

Abstract

An intake throttle valve assembly for an internal combustion engine comprises an intake throttle valve (3) provided with a heater (7) to promote vaporization of fuel at the upper surface of the throttle valve (3) thereby minimizing the fuel droplets falling off the circumference of the throttle valve (3) to reduce differences between air-fuel ratios in different cylinders. The heater (7) consists of tungsten covered by alumina or may be a positive temperature coefficient thermistor and may be on the upper or lower surface or embedded in the throttle valve (3). <IMAGE>

Description

SPECIFICATION An Intake Throttle Valve Assembly for an Internal Combustion Engine The present invention relates to an intake throttle valve assembly for an internal combustion engine.

With an internal combustion engine having a fuel supply device, for example, a carburetor upstream of an intake throttle valve provided in an intake passage, when the throttle valve is opened at a relatively small angle, most of the fuel delivered in the intake passage impinges against the upper surface of the throttle valve to become liquid which then flows on the surface of the throttle valve toward the downstream side thereof and falls from the circumference of the throttle valve, a part being vaporized with the aid of the intake air flow.

In case of a carburetor where the fuel including droplets delivered from a main nozzle or the like impinges against the upper surface of the throttle valve is not fixed and varies depending upon the intake air flow rate and diameter of the fuel droplets, the fuel flowing on the upper surface of the throttle valve and entering the intake passage does not necessarily fall substantially in the center of the passage. In addition, as the intake air swirls in the intake passage, if the fuel falls substantially at an eccentric position as above described, the amounts of fuel supplied to the respective cylinders are different from each other and therefore the air-fuel ratios in the respective cylinders are unequal as shown in Fig. 1.Before the engine has warmed up when the vaporization of the fuel is difficult, such uneven air-fuel ratios in the cylinders become more marked and adversely affects the stability in combustion and operation of the engine. The uneven air-fuel ratios in the cylinders also holds true in an engine injecting the fuel upstream of a throttle valve.

It is an object of the invention to provide an improved intake throttle valve assembly for an internal combustion engine which overcomes the disadvantages in the prior art above described.

It is another object of the invention to provide an intake throttle valve assembly for an internal combustion engine, capable of promoting vaporization of the fuel at an upper surface of the throttle valve to minimize the fuel droplets falling off the circumference of the throttle valve, thereby reducing unevenness in the air-fuel ratio in respective cylinders to improve stability in combustion and operation of the engine.

In order that the invention may be more clearly understood, preferred embodiments will be described, by way of example, with reference to the accompanying drawings.

Fig. 1 is a graph illustrating differences in the air-fuel ratios of respective cylinders of a prior art engine as entioned above; Fig. 2 is a sectional view of a principal part of an intake passage including a throttle valve assembly of one embodiment of the invention; Fig. 3 is a plan view of the throttle valve assembly shown in Fig. 2; Figs 4 to 1 5 show examples of patterns of the heater provided in the throttle valve assembly according to the invention; Fig. 16 is a front elevation of the valve shown in Fig. 15; Fig. 1 7 is a plan view illustrating how to incorporate the heater in the throttle valve according to the invention; Fig. 1 8 is a front elevation showing part of an intake passage including the throttle valve assembly shown in Fig. 17;; Fig. 19 is a sectional view taken along the line XlX-XlX in Fig. 18; Fig. 20 is a sectional view of a principal part of an intake passage illustrating another embodiment of the invention; Fig. 21 is a graph illustrating the uniformity of air-fuel ratios in respective cylinders according to the invention; and Fig. 22 shows an example of a circuit for electrically connecting the heater to be used in an intake throttle valve assembly according to the invention.

Referring to Figs. 2 and 3, in a throttle chamber 2 of a carburetor forming an intake passage 1 of an engine is provided a throttle valve 3, upstream of which is provided a main nozzle 4 for delivering and supplying into the intake passage 1 amounts of fuel corresponding to negative pressure in the throttle chamber or venturi tube 2 or corresponding to intake air flow controlled by the throttle valve 3 in the conventional manner.

The throttle valve 3 is provided on its circumferential periphery with a heater 7 which serves to vaporize instantaneously the fuel flowing on the surface of the throttle valve in the form of droplets or liquid films. It is preferable to provide a heater all over the surface of the throttle valve, but it may be devoid of the heater 7 at the downstream end 6 of the throttle valve because the liquid fuel failing down from the end 6 is likely to be atomized by the intake air flow which tends to concentrate in a clearance 1 9 between the end 6 and a bore 18 even if the throttle valve 3 is slightly opened and because it is possible to distribute the fuel uniformly to the respective cylinders to reduce variations in the air-fuel ratio even if the intake air flow rate changes, owing to the fact that the end 6 of the throttle valve 3 is generally immediately above the center of the intake manifold (not shown) so that the position where the fuel droplets fall is substantially fixed.

Figs. 4 to 1 6 illustrate various embodiments of arrangement of the heater provided on the throttle valve. As can be seen from these drawings, the part 8 which is adjacent the upstream end of the throttle valve 3 and the parts 9 adjacent the ends of the spindle valve 5 may be not provided with a heater 7. In short, the variation in air-fuel ratio can be prevented if only the throttle valve is so constructed that the fuel droplets fall from a constant position or the end of the valve having no heater. Fig. 6 illustrates an embodiment providing the heater 7 all over the surface of the throttle valve and further the throttle valve 3 is addditionally provided at its periphery with a ridge 10 which is cut off at the lowermost end 6 to mechanically control the position where the fuel droplets fall (Figs. 1 5 and 16).The heater 7 is not necessarily provided on the upper surface of the throttle valve 3, but the heater may be on the lower surface thereof or may be in the valve.

Figs. 1 7 to 19 illustrate one example of how to incorporate the heater in the throttle valve. In this example, the heater 7 as shown in Fig. 1 8 is embedded in the throttle valve 3 from whose ends electrodes 20 extend. The valve spindle 5 is made of an electric insulating material such as epoxy resin in which are embedded center electrodes 21 adapted to electrically contact the electrodes 20, respectively. The center electrodes may be connected to an exterior electric device by means of rings and sliding electrodes as shown in Figs. 18 and 19.The valve spindle 5 is provided on its outer surfaces with electrode rings 22 which are electrically connected through electrode ring fastening bolts 23 to the center electrodes 21 and through sliding electrodes 24 in the form of leaf springs adapted to contact the electrode rings 22 and be connected to the exterior electric device (not shown) by means of wires 25.

In this case, the electrode rings 22 may extend only over parts of the circumferential peripheries such that the electrode rings 22 are in contact with the sliding electrodes 24 to pass an electric current therebetween only during a throttle valve position from the completely closed condition to a determined open degree, for example, 500. The center electrodes may be elongated to extend from the ends of the valve spindle and the extending ends of the electrodes may be in contact with the sliding electrodes. As an alternative, the center electrodes 21 may be connected by means of flexible lead wires to the exterior electric device.

In this embodiment, a resistor of, for example, tungsten is printed on a sheet of alumina which is then coated with an insulating protective layer of alumina. Thus produced sheet is bodily sintered.

Accordingly, the resistor is completely insulated and protected from the atmosphere and can be safely used in any liquid, gaseous atmoshpere or the like. Even if the heater is brought into contact with a metal, it is never short circuited.

The heater constructed as above is superior in electric insulating property, thermal conductivity, chemical-resistant property and wear-resistant property. The resistance and shape of the resistor can easily be selected by changing the length and width of the printed pattern. The thickness of the completed heater is 0.2 to 0.3 mm.

In combining the sheet of alumina of the heater 7 with the metal throttle valve 3, various methods may be used. In one method, powdered molybdenum, molybdenum-mangan alloy or filling material which may be effective in metalizing is mixed with an organic binder to form a paste-like material. The sheet of alumina is coated with the paste-like material and sintered in a hydrogen furnace at about 1 ,5000C. The sintered sheet is then nickel-plated and brazed to the metal throttle valve with brazing filler. Instead of the brazing, the heater may be bolted to the throttle valve.

Fig. 20 illustrates a fuel supply device including a fuel injection valve 11 upstream of the throttle valve 3. In this case, the fuel injected from the fuel injection valve 11 and impinging against the upper surface of the throttle valve 3 is also vaporized by being subjected to the heating by the heater 7 provided on the throttle valve 3. The position where the fuel droplets fall is fixed so that the variation in air-fuel ratio in respective cylinders can be minimized as above described.

In other words, the fuel delivered into the intake passage 1 upstream of the throttle valve 3 is heated at the upper surface of the throttle valve 3 by the heater 7 to be vaporized, and on the other hand the fuel droplets which have not been vaporized by heating fall off the specified end of the throttle valve 3, so that the air-fuel ratios of the mixtures distributed into the respective cylinders are made substantially uniform as shown in Fig. 21, thereby improving the stability in operation and combustion in the engine.

Fig. 22 illustrates a circuit for the heater 7. The heater 7 and a battery are connected through a thermo-switch 1 3 adapted to be closed when an engine is cold, a relay 1 5 closed when an alternator or engine is operative and an ignition switch 16, so that an electric current is supplied to the heater 7 to promote the vaporization of the fuel only when the vaporization in the intake passage 1 is difficult or the engine has not warmed up sufficiently. However, the current may of course by supplied to the heater 7 all the time the engine operates. In the event that the fuel is only supplied downstream of the throttle valve 3 when idling, the energization of the heater 7 may by interrupted during idling.

The heater is preferably a plain heater consisting of a thermistor having a positive temperature coefficient. For example, if a seiftemperature controlling type heater made of mainly crystalloid resin and carbon powder is utilized the temperature control by the heater itself is effected and it is possible to design the heater 7 in any patterns in consideration of its performance because the heater can be formed by printing on the throttle valve 3.

As can be seen from the above description, according to the invention the fuel delivered upstream of the throttle valve is effectively vaporized at the throttle valve by the heater, so that even if the intake air flow rate changes, the distribution of the fuel to respective cylinders is stable and uniform to minimize the variation in air-fuel ratio, thereby improving the stability in operation and combustion in the engine resulting in better manoeuvreability and desirable exhaust gas characteristics. Moreover, as the result of the improvement of the fuel vaporization, the fuel can be effectively utilized correspondingly thereto, so that the fuel in the mixture can be reduced with resulting lower fuel consumption.

Claims

1. In an intake throttle valve assembly for an internal combustion engine with fuel supply means upstream of a throttle valve provided in an intake passage, the improvement comprising said intake throttle valve being provided with a heater.

2. An intake throttle valve assembly as set forth in claim 1, wherein said heater is provided on an upper surface of said throttle valve.

3. An intake throttle valve assembly as set forth in claim 1, wherein said heater is provided on a lower surface of said throttle valve.

4. An intake throttle valve assembly as set forth in claim 1, wherein said heater is embedded in said throttle valve.

5. An intake throttle valve assembly as set forth in claim 1, wherein said heater is arranged at least with the exception of a part of the throttle valve which becomes a downstream end of said throttle valve when opened.

6. An intake throttle valve assembly as set forth in claim 1, wherein said heater is arranged all over the throttle valve.

7. An intake throttle valve assembly as set forth in claim 1, wherein an upstream end of said throttle valve and parts thereof adjacent to a valve are not provided with a heater.

8. An intake throttle valve assembly as set forth in claim 1, wherein said heater consists of a thermistor having a positive temperature coefficient.

9. An intake throttle valve assembly as set forth in claim 1, wherein said throttle valve is provided at its periphery with a ridge which is cut off at the lowermost end of the valve when it is opened.

10. Intake throttle valve assemblies substantially as described with reference to, and as illustrated in, the accompanying drawings.