JPS6335183Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an intake air heating device installed at the joint between a carburetor and an intake manifold in an intake system of an internal combustion engine.

Prior Art A heating device is installed at the joint between the carburetor and the intake manifold in order to heat the intake air when starting an internal combustion engine at a low temperature to improve fuel atomization and improve engine drivability. ing. Recently, positive temperature characteristic heating elements (hereinafter referred to as PTC heating elements) have come to be used as heating elements in this heating device.

As an intake air heating device using such a PTC heating element, a PTC element mainly composed of crystalline resin and conductive particles is formed into a cylindrical shape with a flange, and an electrode extraction part is installed in the flange part to connect the inside and outside of the heating cylinder. The intake air heating body, which has electrode plating on its circumferential surface to form different poles, is held at the joint between the carburetor and the intake manifold by sandwiching the flange portion between the carburetor and the intake manifold. An intake air heating device has been proposed (see Japanese Patent Laid-Open No. 135253/1983). However, in such conventional intake air heating devices, the entire inner and outer circumferential surfaces of the heating tube are plated with electrodes that constitute different poles, meaning that the entire inner and outer circumferential surfaces of the heating tube are heated. (heater surface), power consumption is relatively large. However, especially in the case of internal combustion engines of automobiles, it is necessary to ensure power consumption for various electrical systems with limited power supply, so one of the biggest requirements for intake air heating devices is power consumption. This means that there are few However, it cannot be said that conventional intake air heating devices sufficiently meet this demand.

By the way, the atomization state of the air-fuel mixture in the carburetor naturally varies depending on the outside temperature or before and after completion of warm-up. In other words, when the outside temperature is high or after warm-up is completed, there is less need to heat the intake air than when the outside temperature is low or before warm-up is completed, and therefore the degree of heating of the air-fuel mixture is reduced by such operation. It should be changed depending on the conditions. In addition, when looking at the flow of the air-fuel mixture inside the carburetor, the distribution of fuel is not uniform, and naturally the inner circumference of the carburetor body on the side where the fuel suction port (slow port, idle port, main nozzle, etc.) is installed. It is considered that the flow near the wall contains more fuel than the flow near the inner peripheral wall on the opposite side. Therefore, for the purpose of promoting atomization of the fuel, rather than uniformly heating the entire circumference of the heating cylinder, it is necessary to heat the part of the air mixture containing a large amount of fuel more intensively than other parts. Conventional intake air heating devices have not been able to meet such demands. That is, in the conventional intake air heating device, there was no concept of partial heating of the heating cylinder.

Therefore, the applicant first divided the heating surface of the heating cylinder into multiple parts to enable partial heating of the heating cylinder, and thereby selected the power supply to the heating surfaces of unnecessary parts as appropriate depending on the engine operating condition. We have proposed an intake air heating device that can reduce overall power consumption by stopping the system at certain times (hereinafter referred to as
For convenience, this type of heating cylinder is called a split plating type heating cylinder). This allows the intake air to be partially heated with a small amount of power as needed, making it possible to heat the intake air under operating conditions where heating had conventionally been forced to be suspended due to power consumption. Furthermore, apart from this, at least one electrode plating is not applied to the entire outer or inner periphery of the heat generating cylinder, but is applied to the intake flow part that contains a large amount of fuel, taking into consideration the fuel distribution in the intake air as described above. We also proposed a technique in which electrode plating is applied only partially to the heating cylinder (hereinafter, for convenience, this type of heating cylinder will be referred to as a partially plated heating cylinder).

In either case, in the split plating type heat generating cylinder or the partially plated type heating cylinder as described above, at least one electrode plating (the electrode plating having the divided plating or the partial plating) has a non-plated portion. That is, if there is a non-plated part in the split plating part or the partial plating part, the heat generating cylinder part corresponding to the non-plating part is hardly heated, so that the temperature is lower than that of the heat generating cylinder part corresponding to the plating part. Therefore, in particular, the plated part bordering the non-plated part is cooled by the non-plated part, and therefore
It was found that due to the PTC characteristics, the amount of heat generated in that area increases and heat concentration tends to occur. This concentration of heat also promotes deterioration of the area.

Purpose of the invention The purpose of the invention is to increase the wall thickness of the heating cylinder at least in the non-plated part adjacent to the plated part to be thicker than other parts in the split plating type or partially plated type heating cylinder having the non-plated part as described above. By increasing the size, it is possible to prevent heat generation from concentrating at the boundary between the plated portion adjacent to the non-plated portion, thereby preventing deterioration of these boundary portions.

Composition of the invention According to the invention, in order to achieve the above-mentioned purpose,
In a split plating type or partially plating type intake air heating device having a non-plated portion, the thickness of the heating cylinder at the boundary between the non-plated portion and the plated portion is partially increased.

Effect of the invention Since the PTC heating cylinder has a characteristic that the amount of heat generated decreases as the thickness of the cylinder increases, the above-described configuration can prevent heat generation from concentrating at the boundary.

Embodiments Examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows an intake air heating device for an internal combustion engine incorporating a PTC heating element. In the figure, 1 is a carburetor main body, which is provided on the upper part of an intake manifold 2, and a heat insulator 3 as shown in FIG. Gaskets 4 and 5 are interposed between the manifold 2 and the manifold 2, and these are joined together with bolts 21. Reference numeral 6 denotes a PTC heating element formed into a roughly cylindrical shape, which is located at the joint between the carburetor portion below the throttle valve 23 and the intake manifold 2, and is supported within the support groove 25 of the heat insulator 3. Throttle valve 2
It serves to guide the air-fuel mixture from 3 to the intake manifold 2, and also heats the intake air passing through it.

The heating element 6 includes, for example, a heating cylindrical portion 7 made of a PTC element mainly composed of crystalline resin and conductive particles, and a flange portion 8 made of a non-heat generating resin material.
It becomes more. Such PTC elements are made by, for example, melting a crystalline resin, adding carbon black particles into it, dispersing and kneading it, then finely pulverizing this kneaded material, and adding glass fiber-containing thermosetting polyester resin to the powder. It can be made into a cylindrical shape by blending and heating and molding this blend into a mold. The heat generating cylindrical part 7 formed in this way is
A flange portion 8 made of a non-heat generating resin material is integrally joined to the outer periphery of the upper end by pressure contact, adhesive, etc., thereby forming the heat generating element 6.

After joining the flange part 8 to the heat generating cylinder part 7, an electrode plating 9 forming one pole is attached to the inner peripheral surface of the heat generating cylinder part 7 and the upper surface of the flange part 8, and also to the outer peripheral surface of the heat generating cylinder part 7 and the upper surface of the flange part 8. Electrode plating 10 forming the other pole is applied over the lower surface of the flange portion 8 . Note that the lower end surface of the heat generating tube 6 is not plated.

FIG. 3 shows an example of a split plating type heating cylinder. One of the electrode platings, for example, a plurality of electrode platings 9,
For example, it is divided into two plating parts 9A and 9B.
The plated parts 9A and 9B are the non-plated parts (flange part 8
and a portion of the heat generating cylinder body) 13 electrically separate them from each other. In the illustrated embodiment, the surface area of the plated portion 9A is much larger than that of the plated portion 9B, but the area ratio is arbitrary.
Note that the number of divisions is not limited to two, but may be more than two. As the number of divisions increases, partial heating control of the heating cylinder 6 becomes possible.

Each plating part 9 is attached to the overhanging part 18 of the flange part 8.
Electrode extraction fittings 11 corresponding to A, 9B, 10
A, 11B, and 12 are embedded. Each metal fitting 11
The tips of A, 11B, and 12 are plated with the respective electrodes 9.
A, 9B, and 10, respectively, and a voltage is applied to each electrode plating via these electrode fittings.

As shown in FIG. 1, the heating element 6 configured as described above is assembled by interposing its flange portion 8 together with the heat insulator 3 at the joint between the carburetor 1 and the intake manifold 2 and fixing it with bolts 21. This constitutes an intake air heating device. Incidentally, when assembling the flange portion 8 of the heat generating tube 6 into the groove 25 of the insulator 3, sealing performance can be improved by applying a filler to the flange portion.

In the intake air heating device configured as described above, for example, the polarities of the plated parts 9A and 9B are the same (anode or cathode), and the polarity of the plated part 10 is set to be opposite (cathode or anode).

Preferably, the plating section 9B is located below the slow port 27 and the idle port 29 of the carburetor, so that as described above, the amount of liquid film fuel in the air-fuel mixture flowing near the plating section 9B is larger than in other parts. Furthermore, with this arrangement, most of the fuel sucked out from the slow port flows near the plating portion 9B even during idling operation. Although not particularly shown in the drawings, the entire surface of the heating element 6 is coated to prevent fuel from penetrating into its interior.

FIG. 5 shows an example of a partially plated heating cylinder. In FIG. 5, a partial plating 10 is shown in which the outer peripheral plating portion 10 is separated by a non-plating portion 10C.
It is composed of A and 10B. The non-plated portion 10C is also provided on the opposite side in the diametrical direction. The plating portion 10B is located at an angular position approximately corresponding to the plating portion 9B in FIG. 3, and the plating portion 10A is located on the opposite side in the diametrical direction. In the case of Fig. 5, switching control is not intended as in the case of Fig. 3, and electrode plating is not applied to the heating cylinder in the part corresponding to the intake flow where the fuel content is relatively small. This is intended to reduce power consumption.

The configurations of the split plating heating element and the partial plating heating element described above were proposed by the applicant in an earlier application and are not the subject matter of the present invention. The present invention aims to prevent heat generation from concentrating at the boundary between the non-plated part and the plated part in a heating element having such a non-plated part.

Therefore, according to the present invention, the thickness of the heating cylinder near the boundary between the plated portion and the non-plated portion is relatively thick as shown by 50 and 60 in FIGS. 6 and 7, respectively. 6 corresponds to FIG. 3, and FIG. 7 corresponds to FIG. 5.

FIG. 8 is a characteristic diagram showing the relationship between the amount of heat generated and the thickness of the PTC heating cylinder 6. As is clear from the figure, the amount of heat generated decreases as the thickness of the cylinder increases. Therefore, since the thick portions 50 and 60 in FIGS. 6 and 7 generate a relatively small amount of heat, it is possible to prevent heat generation from being concentrated in these portions. In other words, as the thickness of the non-plated part increases, the resistance between the plated electrodes increases, regardless of the influence of cooling from the non-plated part.
The resistance at the boundary with the plating part increases and the amount of heat generated is suppressed.

This is due to the property of the PTC heating element that the greater the resistance, the smaller the amount of heat generated.
The transition to the thickened portions 50, 60 preferably has a smooth curve.
Alternatively, O may be extended over the entire non-plated portion.
In the embodiment shown in FIG. 6, since the flange portion 8 does not generate heat, it is not necessary to thicken the boundary portion between the plated portion and the non-plated portion on the flange portion 8.

In addition, when the present invention is applied to a split plating type heating cylinder, since the boundary between the non-plated part and the plated part is thick, the plated part can be easily divided. In other words, generally, the entire heat generating cylinder is once plated using a shaving method, and then the unplated parts are carved out using a shaving machine, etc. However, if the parts to be scraped off are thick and protruding, only those parts can be easily removed. It can be scraped off.

Effects of the Invention As described above, according to the present invention, by making the heating tube relatively thick near the boundary between the plated part and the non-plated part, where heat concentration tends to occur, it is possible to reduce the amount of heat generated. This makes it possible to prevent deterioration of this boundary area.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view showing an example of a typical structure of an intake air heating device incorporating a heating element, and Fig.
A perspective view of the heat insulator shown in the figure, FIG. 3 is a perspective view showing an example of a split plating type heating cylinder,
Figures 4A, 4B, and 4C are cross-sectional views taken along lines A-A, B-B, and CC in Figure 3, respectively, and Figure 5 is a perspective view showing an example of a partially plated heating cylinder. , Fig. 6 is a bottom view of the heat generating cylinder shown in Fig. 3 to which the present invention is applied, Fig. 7 is a bottom view of the heat generating cylinder shown in Fig. 5 to which the present invention is applied, and Fig. 8 shows the calorific value of the heat generating cylinder - cylinder. A thickness characteristic diagram, FIG. 9 is a diagram showing a modified example of FIG. 7. 6... Heating element, 7... Heat generating cylinder part, 8... Flange part, 9A, 9B, 10... Electrode plating, 10C, 1
3...Non-plated part, 50, 60...Thick walled part.

Claims (1)

[Scope of utility model registration request] For an internal combustion engine, the inner and outer circumferential surfaces of a heating cylinder having positive temperature characteristics are plated with electrodes that form mutually different poles, and the electrode plating on at least one pole has a plated part separated by a non-plated part. An intake air heating device for an internal combustion engine, characterized in that the thickness of the heating cylinder is partially increased at the boundary between the non-plated portion and the plated portion.