JPS608140Y2 - Internal combustion engine intake air heating device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an intake air heating device for an internal combustion engine using a ceramic heating element, and aims at improving heating efficiency and making the device compact and simple.

Ceramics such as barium titanate (hereinafter referred to as PTC ceramics) generate heat when electricity is applied to them, and when a certain temperature is reached, the electrical resistance increases rapidly.

At temperatures below a certain temperature (cure point), a large current is allowed and the cut point is reached instantaneously; at temperatures above the cut point, the electrical resistance becomes extremely large and only a small current is allowed, resulting in overheating. It self-adjusts its temperature to around the cue point.

Therefore, if a PTC ceramic heating element is used as a heating means to promote the atomization of the fuel mixed with air and sent to the combustion chamber, the fuel can be instantly heated during a cold start. This is more advantageous than heating means using exhaust gas or engine cooling water.

The general structure of an intake air heating device using a PTC ceramic heating element is to place at least a portion of a casing made of a metal plate with good thermal conductivity at the part where the intake pipe branches to each cylinder directly below the throttle valve. The casing is exposed inside the intake pipe and serves as a heating surface and an electrode. A PTC ceramic heating element is sandwiched within the casing, and another electrode plate facing the casing is pressed by a spring member to move the heating element to the casing. It is pressed against the back side of the exposed portion.

The fuel supplied through the intake pipe is not sufficiently mixed with the intake air during a cold start, and the fuel in the negative part becomes a liquid film flow that flows along the wall surface of the intake pipe. Atomization of the fuel is promoted by contacting the heated surface of the casing exposed in the intake pipe.

By the way, in the heating device as described above, which consists of a heating surface, a PTC ceramic heating element, an electrode, a spring member, and a support member that supports the spring member, the heating surface is heated by the heat generated by the heating element, but the heating element Some of the heat becomes useless heat that escapes from the electrode, the spring member, and its support member to the engine.

In order to reduce this useless heat, the support member is conventionally made of a heat insulating resin, but the spring member needs a set length to expand and contract, and the support member The member must have a certain thickness to provide strength, which increases the size of the device, and the end of the support member must be sealed to prevent air-fuel mixture from entering the device.

Therefore, the present invention can support the heating element and electrodes without using a spring member, making it possible to downsize the device.
To provide an intake air heating device for an internal combustion engine which increases heating efficiency by minimizing ineffective heat, has a simple structure, is easy to assemble, and has good sealing performance.

Hereinafter, the details of the present invention will be explained with reference to Examples.

The carburetor 1 and the suction pipe 2 are connected by a bolt (not shown) via a gasket 3 at 3 b and an insulating member 4 having thermal and electrical insulation properties.

Gasoline fuel supplied from a combustion supply port (not shown) that opens in a part of the venturi of the carburetor 1 is mixed with intake air, passes through the passage of the carburetor 1, passes through the throttle valve 5, and then enters the intake pipe 2.
The fuel is supplied to the combustion chamber (not shown) of the internal combustion engine.

In the intake pipe 2, an intake air heating device A supported by the insulating member 4 is disposed directly below the throttle valve 5.
The device A constitutes a passage for gasoline fuel mixed with intake air.

The heating device A includes an inner cylinder 6, a PTC ceramic heating element 7,
It is composed of an electrode 8, an elastic covering member 9, and insulating members 10 and 11.

The inner cylinder 6 is made of a thin metal plate with good conductivity, and has a cylindrical part 6a and a flange part 6b integrally formed on its upper edge.

A cylindrical heating element 7 made of fired PTC ceramic, for example, a ceramic whose main component is barium titanate, is tightly fitted into the outer periphery of the cylindrical portion 6a.

Note that the heating element 7 may be constructed of a plurality of divided members each having a shape in which a cylindrical body is divided in the vertical direction.

Like the inner tube 6, the metal thin plate electrode 8 has a tube portion 8a and a flange portion 8b integrally formed on its upper edge.

The electrode 8 is fitted onto the outer periphery of the heating element 7 at its cylindrical portion 8a.

As particularly shown in FIG. 5, the cylindrical portion 8a of the electrode 8 is provided with a plurality of triangular notches 80 from the lower end side, and the heating element 7 is fitted into the cylindrical portion 8a.

Each flange portion 6b, 8 of the inner cylinder 6 and electrode 8 facing each other
An annular insulating member 10 made of an electrically insulating material such as epoxy resin is interposed between the inner cylinder 6 and the electrode 8, thereby insulating the inner cylinder 6 and the electrode 8.

Further, an annular insulating member 11 having an L-shaped cross section is fitted to the lower end periphery of the inner cylinder 6 so as to support the lower end of the heating element 7 .

On the outer periphery of the cylindrical portion 8a of the electrode 8 and the insulating member 11,
A tubular elastic covering member 9 made of stretchable rubber or synthetic resin, which has excellent heat resistance, electrical insulation, chemical resistance that does not deteriorate due to gasoline, etc., and heat insulation, is stretched in the radial direction to apply a contractile force. covered in condition.

As this covering member 9, fluororubber or fluororesin can be suitably used.

In particular, since fluororesin has heat-shrinkability, if it is heated after installation, it will shrink and tighten the electrode 8 to the heating element 7, and if the heating element 7 acts, it will always exert a strong contraction force due to the heat. Therefore, it is most suitable as the covering member 9.

The heating device A configured as described above has a vaporizer 1
It is held by an insulating member 4 interposed between the intake pipe 2 and the intake pipe 2.

The inner cylinder 6 is disposed coaxially with the intake pipe 2 and forms a passage for the air-fuel mixture supplied via the throttle valve 5.

Note that an engine cooling water passage 12 is provided in the bottom wall of the intake pipe 2.

The inner cylinder 6 has a lead wire 14 at its flange portion 6a.
The inner cylinder 6 constitutes an intake air heating surface and also serves as a counter electrode to the electrode 8 which is pressed to the outside of the heating element 7.

Further, the electrode 8 is grounded by a lead wire 15.

In the intake air heating device configured as described above, when the internal combustion engine is started, the current from the battery 13 flows through the lead wire 1.
4 and the flange portion 6b of the inner cylinder.

A cylindrical portion 6a forming a heating surface, a PTC ceramic heating element 7,
It passes through the electrode 8 and the lead wire 15 and returns to the battery 13 via the engine body.

At this time, the temperature of the heating element 7 instantaneously rises to a temperature close to the cue point, and the heat is transferred to the inner cylindrical portion 6a, and the un-atomized fuel droplets that flow down during the cold start are heated and atomized.

However, in the intake air heating device of the present invention, since the heating surface is cylindrical and the mixed intake air passage is configured, most of the un-atomized fuel droplets flow down the heating surface as a wall flow. Fuel can be heated efficiently.

Furthermore, since no spring member is used to support the heating element, the device can be made smaller.

Further, since the heat-insulating tubular covering member is tightened from the outer periphery and the electrodes in contact with the outer surface of the heating element are configured to be deformable in the radial direction, the heating element and the electrodes can be closely pressed together.

Further, the tightening of the covering member can completely seal the end of the device by applying force.

Further, since the tube-shaped elastic covering member is used, the inner tube, the heating element, and the electrodes can be assembled extremely easily, and the structure of the heating device can also be simplified.

Furthermore, since the spring member is eliminated and the electrode is directly wrapped with the heat insulating covering member, the heat of the heating element is less likely to escape to areas other than the heating surface, improving heating efficiency.

In the above embodiment, the heating element 7 is formed into an integral cylindrical shape, but it is possible to use a plurality of divided members each having a shape in which the cylindrical body is divided in the vertical direction, and to provide a very small gap between the divided members. Alternatively, it may be brought into pressure contact with the outer circumferential surface of the inner cylinder 6.

In this way, the heat generating element dividing member is also tightened to the inner cylinder by the force of the tightening from the tubular covering member, and the adhesion between the inner cylinder and the heat generating element is improved.

Further, in the above embodiment, the electrode 8 is provided with a plurality of notches 80 to impart deformability in the radial direction, but as a deformability imparting means, for example, a band-shaped electrode is wound around the outer peripheral surface of the heating element 7. Other measures may also be taken, such as providing a small gap between opposing edges to allow tightening.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the installed state of an embodiment of the intake air heating device according to the present invention, Fig. 2 is an enlarged sectional view of the intake air heating device, and Fig. 3 is an enlarged sectional view of the intake air heating device.
The figures are an enlarged cross-sectional view taken along the line ■--■ in FIG. 2, FIG. 4 is a plan view of the metal thin plate electrode, and FIG. 5 is a cross-sectional view taken along the line ■--■ in FIG. 4. 1... Carburetor, 2... Intake pipe, A...
...Intake heating device, 6...Inner cylinder, 7...
... Heating element, 8 ... Electrode, 9 ... Covering member, 13 ... Battery.

Claims (1)

[Scope of utility model registration request] For internal combustion engines that have a fuel supply system that mixes fuel with intake air and supplies it to the combustion chamber through the intake pipe, ceramic is formed into a cylindrical shape that has positive resistance temperature characteristics that show a sudden increase in resistance at a specific temperature. An inner cylinder of a thin metal plate forming a fuel heating surface is tightly fitted on the inner peripheral surface of the heating element, and a cylindrical electrode that is deformable in the radial direction is fitted on the outer periphery of the heating element,
A heating device is constructed by fitting a flexible tube-shaped covering member made of heat-resistant rubber or synthetic resin around the outer periphery of the electrode while applying a contraction force in the radial direction. An intake air heating device for an internal combustion engine, characterized in that the cylinder is disposed in an intake pipe of the internal combustion engine so as to form a passage for an air-fuel mixture.