JPS601257Y2 - 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 heating element made of a ceramic material, and in particular to a support structure for the heating element.

When a ceramic such as barium titanate is energized, it generates heat, and when it reaches a predetermined temperature, its electrical resistance increases rapidly.

Then, at a temperature below a specific temperature (curi point), the c: yaw current is allowed and the curi point is reached instantaneously, ki, 1-1-I
When the salinity is above the J point, the electric resistance becomes extremely large and only a small current is allowed, so the temperature is self-adjusted to around the cue point without overheating.

If a ceramic with such characteristics (PTC ceramic) is used as a heating means to promote atomization of fuel contained in the intake air of an internal combustion engine, the intake air containing fuel can be instantly heated even during a cold start. Therefore, it 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 1. A casing made of a metal plate with good thermal conductivity is installed at the part directly below the throttle valve where the intake pipe branches to each cylinder so that at least a part of the casing is exposed inside the intake pipe, and a spring member etc. The heating element is pressed against the back side of the exposed portion of the casing.

By the way, the problem with this support structure is how to press-support the casing with good adhesion and whose flatness is not accurate due to processing precision without using the ceramic material.

Generally, a ground washer or a coil spring is used as a support means for crimping the heating element to the cage jig, but wave washers do not have a large spring stroke, so if the device vibrates, the heating element cannot be used. This may cause variations in the pressure applied to the casing, and the heating element may become misaligned with respect to the casing.

With coil springs, an uneven load is applied to the heating element, which may cause damage to the heating element.

In addition, in order to uniformly apply the push-up blade by the spring to the heating element surface, a method has been taken in which a metal plate is interposed between the two, but it is not possible to perfectly match the flatness of the facing surfaces of the metal plate and the heating element. It is quite difficult to process, and if the load of the coil spring acts on the unevenly touched part, the heating element is more likely to be damaged.

Therefore, the present invention aims at an intake air heating device having a support structure that supports a PTC ceramic heating element without damaging it and brings it into pressure contact with a casing. Provided is an intake air heating device having a support structure in which a heating element is supported in the direction of a casing by interposing a cushioning material such as a heat-resistant flexible rubber elastic body such as fluororubber or fluororesin containing powder of the present invention.

Therefore, in the support structure of the present invention, the cushioning material adheres well to the heating element and the casing due to its flexibility, smoothing heat transfer, and its elastic deformation absorbs uneven loads on the heating element due to springs, etc. to prevent damage to the heating element.

In addition, when electricity starts, the PTC ceramic heating element has low electrical resistance, so there is a risk that it will consume inrush current and temporarily reduce the performance of other electrical devices in the vehicle, but carbon and metal powder in the cushioning material The rush current can be suppressed by appropriately adjusting the electrical resistance depending on the mixed concentration of .

Hereinafter, the present invention will be explained based on the illustrated embodiments.

In Fig. 1, 1 is an intake pipe of an internal combustion engine, and a carburetor (not shown) is installed upstream of the intake pipe, and gasoline fuel supplied from a fuel supply port that opens in a part of the venturi of the carburetor is mixed with intake air. is connected to the intake pipe 1 via the throttle valve 2.
It is supplied to the combustion chamber of the engine (not shown).

Directly below the throttle valve 2, a circular hole 11 is provided in the pipe wall of the bent part of the intake pipe 1 constituting the heat riser part, and an intake air heating device A is installed therein.

□The casing 3 of the intake air heating device A includes a heating surface portion 31 in the shape of a circular flat plate, a plurality of legs 32 extending perpendicularly from the periphery thereof and having a flange 321 at the tip, and a side wall of the casing that wraps around the legs 32. Cylindrical support part 33 to be formed
Moreover, the support part 33 also has a flange 331 at its tip.
is formed.

The heating surface portion 31 and the leg portions 32 are integrally molded from an aluminum plate, and the support portion 33 is made of heat-resistant and electrically insulating resin.

The support part 33 is fitted into the hole 11 provided in the intake pipe 1, and at the flange 331 where the leg part 32 is embedded, together with the bottom plate 4 disposed so as to cover the lower opening of the casing 3. , is fixed to the intake pipe 1 with bolts 34.

Note that a gasket 35 is interposed between the support flange 331 and the intake pipe 1.

Inside the casing 3, a coil spring 5 is supported on a bottom plate 4, and supports a heating element 9 via an electrical insulating material 6 and an electrode plate 7.

A disc-shaped cushioning material 8 is interposed between the heating surface portion 31 and the heating element 9, and the heating element 9 is inserted into the cushioning material 8.
It is pressed into contact with the lower surface of the heating surface part 31 via.

The cushioning material 8 is made of heat-resistant fluororubber, fluororesin, or the like containing carbon powder or metal powder such as aluminum, and maintains its flexibility and cushioning properties up to high temperatures, and the contained powder allows it to be energized. Has performance.

The electrical insulating material 6 is made of resin and has a cylindrical shape, and is supported by a spring 5 from below the flange at the upper end.

The electrode plate 7 is a copper plate. An electrode terminal 71 is formed by a claw bent downward at the center thereof, and is connected to a lead wire 70 connected to a battery anode terminal (none of which is shown) via a key switch.

Note that W is an engine cooling water flow passage. In the above intake air heating device A, when the key switch is closed to start the internal combustion engine, the current from the battery is transferred to the patch anode and the lead wire 70.
, electrode plate 7, heating element 9, cushion material 8, heating plate part 31
．． It flows through the path of the leg 32, bolt 34, intake pipe 1, and battery cathode.

At this time, the temperature of the heating element 9 instantaneously rises to about 150°C due to the energization, and the heat is transferred to the heating surface part 31 through the cushion material 8 that is in close contact with the heating element 9, and the mist that flows into the intake pipe 1 at the time of cold start The atomized fuel droplets are heated by the heating surface section 31 and atomized.

By the way, the facing surfaces of the electrical insulator 6, electrode plate 7, and heating element 9 may not always have perfect flatness due to manufacturing variations, and the spring 5 may also not be able to obtain perfect vertical pushing force. Not necessarily.

Therefore, if the electrical insulator 6, electrode plate 7, and heating element 9 are simply stacked one on top of the other and supported by the spring 5, if the above-mentioned adverse conditions overlap, the stress distribution acting on the heating element will become extremely uneven, resulting in heating. Uniform adhesion between the surface portion 31 and the heating element 9 cannot be obtained, resulting in a significant decrease in thermal efficiency.

Furthermore, the heating element 9 may be damaged.

However, by interposing the cushioning material 8 between the heating element 9 and the heating surface portion 31, the uneven load of the spring 5 acting on the heating element 9 is absorbed by the deformation of the cushioning material 8, and the heating element 9 The heating surface portion 31 maintains uniform adhesion to the cushioning material 8 over the entire surface.

As a result, heat conduction is made smooth, and the heating element 9
damage is also prevented.

Furthermore, the present invention has the effect of reducing rush current when the resistance of the PTC ceramic heating element 9 becomes low.

In other words, taking the case where carbon powder is mixed into a fluororesin as an example, the relationship between the amount of the mixture and the electrical resistance value (logarithmic scale) is as shown in Figure 2, and by adjusting the amount of the mixture, any desired resistance can be obtained. Value can be set.

Furthermore, as shown in FIG. 3, this cushion material has a positive resistance temperature characteristic as shown by line A in FIG.
The composite resistance temperature characteristic with C ceramic (line B) is line A + B.
As a result, the resistance of the part that is lower temperature than the curvature point is made higher, and the rise in temperature near the curvature point does not deteriorate much.

Therefore, by using the above-mentioned cushioning material and adjusting its resistance by adjusting the amount of carbon or the like mixed therein, it is possible to appropriately suppress the rush current at the start of energization.

If a large amount of current is consumed by the intake air heating device at the start of energization, it may reduce the effectiveness of other electrical devices in the vehicle and adversely affect engine startability. This makes it possible to maintain good startability.

Note that the cushioning material is not limited to a material with a positive resistance-temperature characteristic; for example, a material with a negative resistance-temperature characteristic as shown by line C in FIG. 4 may also be used to similarly obtain the inrush current suppressing effect.

Furthermore, as the cushioning material, heat-resistant rubber such as fluororubber mixed with carbon or metal powder at high density can be used.

Therefore, as described above, the present invention interposes a heat-resistant, flexible rubber elastic body mixed with carbon or metal powder at a high density between the casing heating surface and the C ceramic heating element as a cushioning material and a heat transfer medium. As a result, the heating element is held without damage and heat conduction is performed smoothly, and the inrush current to the intake air heating device at the start of energization is suppressed to maintain good engine startability. The device also has excellent durability.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the intake air heating device according to the present invention;
FIG. 2 is a diagram showing the relationship between the amount of carbon mixed in the cushioning material and the electrical resistance value, and FIGS. 3 and 4 are diagrams showing the resistance temperature characteristics of the PTC ceramic heating element and the cushioning material. A... Intake air heating device, 1... Intake pipe,
2... Casing, 5... Coil spring, 7... Electrode plate, 8... Cushion material, 9... PTC ceramic heating element , 31
...Heating surface part (exposed part) of the casing.

Claims (1)

[Scope of utility model registration request] A casing made of a metal plate with good thermal conductivity is installed in the intake pipe, a part of which is exposed inside the intake pipe, and the casing has a positive resistance temperature characteristic and a cue point at a specific temperature and is energized. A heating element made of a ceramic material that generates heat is supported by being pressed against the back side of the exposed part of the casing through a cushioning material made of a heat-resistant flexible rubber elastic body mixed with carbon or metal powder at a high density. An intake air heating device for an internal combustion engine, characterized in that: