JPS5918139Y2 - Internal combustion engine intake air heating device - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to an intake air heating device for an internal combustion engine.

Before the engine warm-up is completed when the engine temperature is low, the fuel supplied from the carburetor is not sufficiently vaporized, and as a result, a large amount of fuel is supplied in liquid form into the engine cylinders, compared to after the engine warm-up is completed. There is a problem in that combustion is poor and, as a result, stable engine operation cannot be ensured.

Therefore, during normal warm-up operation, a richer air-fuel mixture is supplied into the engine cylinders than after completion of warm-up to ensure stable engine operation.

However, when such a rich air-fuel mixture is supplied into the engine cylinder, not only do unburned hydrocarbons HC and carbon monoxide CO, which are harmful components in the exhaust gas, increase, but also the fuel consumption rate worsens. arise.

Therefore, if the liquid fuel supplied from the carburetor can be sufficiently vaporized during engine warm-up, stable engine operation can be ensured even if the air-fuel mixture supplied to the engine cylinders is diluted. By being able to use a lean mixture, it is possible to reduce harmful components in exhaust gas and improve fuel consumption.

In order to promote the vaporization of liquid fuel during engine warm-up, there has been conventionally known an intake air heating device in which exhaust gas is guided into a part of the intake manifold riser and the part of the intake manifold riser is heated by the exhaust gas. However, such intake air heating devices that utilize exhaust gas heat not only have low thermal efficiency, but also the exhaust gas temperature does not rise until some time after the engine starts, so the vaporization of liquid fuel is promoted immediately after the engine starts. It is difficult.

In order to solve this problem, a positive temperature coefficient thermistor element (hereinafter referred to as a PTC element) with a honeycomb structure is inserted into the joint between the intake manifold and the carburetor to heat the entire air-fuel mixture supplied from the carburetor. An intake air heating device has been proposed.

However, most of the liquid fuel supplied from the vaporizer flows along the inner wall surface of the vaporizer air horn, and therefore, to promote vaporization of the liquid fuel, it is necessary to intensively heat the liquid fuel flowing along this inner wall surface. There is.

However, in the above-mentioned intake air heating device, only a small proportion of the heat emitted from the PTC element is used to heat the liquid fuel, and a considerable portion of the heat is used to heat the air.

Therefore, this intake air heating device is not satisfactory in terms of promoting the vaporization of liquid fuel, and also has the problem that the filling efficiency is reduced because the air is heated.

The present invention provides an intake air heating device that effectively uses heat emitted from a heating element to heat liquid fuel instead of heating air, thereby sufficiently promoting vaporization of liquid fuel. There is a particular thing.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, 1 is the engine body, 2 is an intake manifold, 3 is a manifold gathering part, 4 is a heat insulating member, and 5 is a carburetor fixed on the intake manifold 2 via this heat insulating member 4. .

This carburetor 5 has a primary carburetor A having a primary air horn 6 and a primary throttle valve 7 extending approximately vertically, and a secondary air horn 8 and a secondary throttle valve 9 extending approximately vertically. It is composed of a secondary side carburetor B.

As shown in FIGS. 1 and 2, a hollow cylindrical PTC element 10 having almost the same inner diameter as the primary air horn 6 is provided in the heat insulating member 4 below the primary side carburetor A.
The lower end of this PTC element 10 is the intake manifold collecting part 3.
protrude inward.

As shown in FIGS. 2 and 3, the PTC element 10 has an upper flange portion 11 extending horizontally outward at its upper end.
This upper flange portion 11 is cast into the heat insulating member 4 at the same time as the heat insulating member 4 made of synthetic resin material is molded.

Therefore, the PTC element 10 is firmly supported by the heat insulating member 4.

Before the PTC element 10 is cast into the heat insulating member 4 as described above, a plating layer made of silver or copper that constitutes an electrode is formed on the inner wall surface 12 and outer wall surface 13 of the PTC element 10.

In the embodiment shown in FIG. 1, the plating layer formed on the inner wall surface 12 is used as an anode, and the plating layer formed on the outer wall surface 13 is used as a cathode. - The plating layer on the lower end surface 14 of the PTC element 10 and the outer peripheral end surface 15 of the upper flange portion 11 is scraped off after the plating work is completed so as to prevent the PTC element 10 from being damaged.

On the other hand, when the plating layer on the lower end surface 14 of the PTC element 10 is scraped off in this manner, the PTC element 10 is directly exposed to the gasoline atmosphere.

However, since the PTC element 10 deteriorates when exposed directly to the gasoline atmosphere, an insulator 16 is attached to the lower end surface 14 of the PTC element 10 as shown in FIG.
This prevents the lower end surface 14 of the TC element 10 from being exposed to the gasoline atmosphere.

Note that this insulator 16 is made of P before firing the PTC element 10.
It is also possible to attach the PTC element 10 to the lower end surface 14 of the TC element 10 and fire the PTC element 10 with the insulator 16 attached.

Next, external lead wires 17.
18 is attached, and then the PTC element 1 is installed as described above.
0 and are cast into the heat insulating member 4 together with the lead wires 17 and 18.

Furthermore, if the inner wall surface 12 and outer wall surface 13 of the PTC element 10 are simply covered with a plating layer, there is a risk that the plating layer will peel off due to thermal expansion and contraction caused by repeated heating of the PTC element 10.

Therefore, in the embodiment shown in FIG. 2, metal coatings 19 and 20 made of, for example, an aluminum alloy are formed on the plating layers on the inner wall surface 12 and outer wall surface 13 of the PTC element 10, respectively, to protect and reinforce the plating layers. There is.

These metal coatings 19, 20 are formed, for example, by dipping the PTC element 10 having a plating layer into a molten aluminum alloy.

Note that this metal coating 19.degree. 20 is thicker than the plating layer because it also serves as reinforcement for the plating layer.

As shown in FIG. 1, the lead wire 18 is grounded, while the lead wire 17 is connected to a power source 24 via a temperature detection switch 21, a neutral point voltage detection switch 22, and an ignition switch 23.

The temperature detection switch 21 detects that the engine cooling water temperature is, for example, 60'C.
It is in the on state in the following cases, and becomes in the off state when the engine cooling water temperature reaches 60°C or higher.

On the other hand, the neutral point voltage detection switch 22 is in an off state when the neutral point voltage of the engine-driven alternator is below a predetermined level, and is in an on state when this neutral point voltage exceeds a predetermined level.

Since a large current flows through the PTC element 10 when current supply starts, it is necessary to prevent the start of current supply to the PTC element 10 when the starter motor is being driven to start the engine.

For this purpose, a neutral point voltage detection switch 22 is provided.

That is, when the engine is rotated by the starting motor, the neutral point voltage is low, and when the engine starts self-driving operation, the neutral point voltage becomes high and the neutral point voltage detection switch 22 is turned on, causing current to flow to the PTC element 10. Supply begins.

When the supply of current to the PTC element 10 is started in this way, the temperature of the PTC element 10 immediately rises, and as a result, the inner wall surface 1
2, the temperature also rises immediately.

On the other hand, when the engine starts, most of the liquid fuel supplied from the primary carburetor A descends along the inner wall surface of the primary air horn 6, and then this liquid fuel flows into the PTC element 10. It descends along the wall surface 12.

Therefore, the liquid fuel descending on the inner wall surface 12 is transferred to the PTC element 1.
0, thereby promoting vaporization of the liquid fuel.

As shown in FIG. 2, the PTC element 10 is not in contact with the intake manifold 2, and therefore a small amount of the heat emitted from the PTC element 10 is transferred to the atmosphere, the intake manifold 2, or the carburetor via the heat insulating member 4. Just run away to 5.

Most of the heat emitted from the PTC element 10 is thus used to heat the inner wall surface 12.

Furthermore, the inner wall surface 12 is covered with liquid fuel, and therefore most of the heat emitted from the PTC element 10 is used to vaporize the liquid fuel.

Furthermore, since the PTC element 10 is made of ceramic, it has an uneven surface when viewed microscopically.

However, since the plating layer and the metal coating 19.20 are formed in complete contact with the uneven surface without any gaps, the thermal conductivity between the PTC element 10 and the plating layer or metal coating 19.20 is high. , thus PTC
Heat emitted from the element 10 is efficiently transferred to the liquid fuel.

When the temperature of the engine cooling water becomes higher than 6σC some time after the engine is started, the temperature detection switch 21 is turned off and the supply of current to the PTC element 10 is stopped.

Another embodiment is shown in FIGS. 4 to 6.

In this embodiment, a mixture guide pipe 25 is attached to the lower side of the primary air horn 6, and a heating element container 26 is arranged below the guide pipe 25.

As shown in FIG. 5, this heating element container 26 includes a heat insulating container 28 made of a synthetic resin material which is inserted into an opening 27 of the intake manifold 2 and fixed to the intake manifold 2 with, for example, bolts, and this heat insulating container 28. Supported PTC
It is composed of an element 29 and a ring-shaped insulator 30 inserted so as to cover the peripheral end face of the PTC element 29.

A plating layer is formed on the inner wall surface 31 and outer wall surface 32 of the PTC element 29, and the plated inner wall surface 31 is further covered with a metal coating 33.

Further, the inner wall surface 31 of the PTC element 29 is connected to the intake manifold 2 via the lead wire 34, while the outer wall surface 3
2 is connected to the temperature detection switch 21 in FIG. 1 by a lead wire 35.

In this embodiment, the fuel supplied from the primary side carburetor A is passed through the air-fuel mixture guide pipe 25 to the inner wall surface 31 of the PTC element 29.
In this way, the vaporization of the liquid fuel is promoted.

As described above, according to the present invention, it is sufficient to simply form a plating layer on the inner wall surface and outer wall surface of the PTC element and apply a voltage between these plating layers, thereby greatly simplifying the structure of the heating element container. can.

Furthermore, by covering the end face of the PTC element with an insulator, gasoline will not enter into the PTC element, so the life of the PTC element can be greatly extended.

In addition, since the liquid fuel flowing on the inner wall surface of the PTC element is directly heated by the PTC element, the heat emitted from the dry TC element can be effectively used for vaporizing the liquid fuel, thus ensuring sufficient vaporization of the liquid fuel. can be promoted.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of the engine intake system according to the present invention, Fig. 2 is a partially enlarged side sectional view of Fig. 1, and Fig. 3 is II of Fig. 2.
4 is a side sectional view of another embodiment; FIG. 5 is a partially enlarged side sectional view of FIG. 4;
FIG. 6 is a plan view of the heating element container of FIG. 5.

Claims (1)

[Scope of utility model registration request] In an intake air heating device in which a heating element is disposed in an intake passage downstream of a fuel supply device and the heating element heats the air-fuel mixture flowing in the intake passage, the heating element is a thin-walled PTC.
The PTC element has an inner wall surface that is directly exposed to the gasoline atmosphere in the intake passage, an outer wall surface, and an end face that is directly exposed to the gasoline atmosphere in the intake passage,
Covering the end face with an insulator, forming a plating layer constituting an electrode on the inner wall surface and the outer wall surface, and applying a voltage between the plating layer formed on the inner wall surface and the plating layer formed on the outer wall surface. An intake air heating device for an internal combustion engine.