JPH0223707B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an intake air heating device for an internal combustion engine.

[Conventional technology]

When the engine temperature is low and the engine is warmed up, the fuel supplied from the carburetor will not be sufficiently vaporized, so a large amount of fuel will be supplied in liquid form into the engine cylinders, resulting in less combustion than after engine warm-up. The problem is that stable engine operation cannot be ensured. Therefore, normally, during warm-up operation, a richer air-fuel mixture is supplied into the engine cylinders than after warm-up is completed to ensure stable engine operation. However, when such a rich mixture is supplied into the engine cylinder, not only does the amount of unburned hydrocarbons (HC) and carbon monoxide (CO), which are harmful components in the exhaust gas, increase, but also the fuel consumption rate worsens. This creates the problem of 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 air-fuel mixture, it is possible to reduce harmful components in exhaust gas and improve fuel consumption. Therefore, in order to promote the vaporization of liquid fuel during engine warm-up, the applicant first attached a hollow heating element container to the outlet of the carburetor air horn.
This hollow heating element container is composed of an inner cylinder, an outer cylinder, and a positive characteristic thermistor element (hereinafter referred to as a PTC element) inserted between the inner cylinder and the outer cylinder,
We proposed an intake air heating device in which the inner cylinder of a hollow heating element container was heated by heating the PTC element with an elastic (graphite) electrode in contact with the PTC element (Japanese Patent Application No. 169050-1986). Publication No. 46263)).

Since the present invention relates to improvements in this type of intake air heating device, and particularly to improvements in the structure of its elastic electrodes, the structure of this intake air heating device, which is the basis of the improvement of the present invention, will first be explained in Figures 1 to 1. This will be briefly explained with reference to FIG.

In FIG. 1, 1 is an engine body, 2 is an intake manifold, 3 is a manifold gathering section, 4 is a heat insulating plate made of a synthetic resin material attached to the manifold gathering section 3 via a gasket 5, and 6 is a gasket 7. The carburetors are respectively shown fixed on the heat insulating plate 4 through the
This carburetor 6 includes a primary carburetor A and a secondary carburetor B.
and has. The primary side carburetor A includes a primary side air horn 8, a primary side main nozzle 9, and a primary side throttle valve 10, and the secondary side carburetor B includes a secondary side air horn 11, a secondary side main nozzle 9, and a primary side throttle valve 10. Main nozzles 12 and 2
The next throttle valve 13 is provided. As shown in FIG. 1, the insulation plate 4 at the lower end of the primary side carburetor A
A hollow heating element container 14 is provided therein, which is aligned with the primary air horn 8 and projects into the manifold collecting section 3 . As shown in FIGS. 2 and 3, the hollow heating element container 14 is composed of an inner cylinder 15 made of a thin metal material and an outer cylinder 16 made of a thin synthetic resin material. As shown in FIG. 4, the outer cylinder 16 has a middle part 16a having a uniform inner diameter, an upper end part 16b having an inner diameter slightly larger than the middle part 16a, and a lower end part 16c having an inner diameter smaller than the middle part 16a. has. Middle part 16a
and a first annular shoulder portion 17 and a first annular shoulder portion 17 between the lower end portion 16c and the lower end portion 16c.
A second annular shoulder 18 located below the annular shoulder 17
A staircase portion 16d is formed. An annular flange 20 having a rectangular cross section is integrally formed on the back surface of the intermediate portion 16a adjacent to the upper end portion 16b. Furthermore, a flange 2 is disposed on the outer cylinder 16 from the upper end 16b.
A notch 21 is formed that extends inwardly, and a bottom surface 22 of this notch 21 is a flat surface that extends in the radial direction.

As described above, this outer cylinder 16 is integrally molded from a synthetic resin material, but it can also be formed from a metal material.

On the other hand, as shown in FIGS. 2, 3, and 5, the inner cylinder 15 has an intermediate portion (contact surface portion) 15a having a regular octagonal cross section, a cylindrical upper end portion 15b, and a cylindrical lower end portion 15c. Cylindrical upper end portion 15b and cylindrical lower end portion 15c
The intermediate portion 15a has a cylindrical upper end portion 15b and a cylindrical lower end portion 15c as a whole.
It bulges inward from. A stepped flange 23 extending outward is integrally formed at the tip of the cylindrical upper end portion 15b. This stepped flange 23 includes an inner flange portion 23a having an L-shaped cross section extending outward from the tip of the cylindrical upper end portion 15b, and an inner flange portion 23a extending outward from the tip of the cylindrical upper end portion 15b.
The outer flange portion 23b has an L-shaped cross section and extends further outward from the tip of the outer flange portion 3a. Furthermore,
An outwardly extending flange 24 having an L-shaped cross section is integrally formed at the tip of the cylindrical lower end 15c, and the flange 24 is caulked onto the lower end 16c of the outer cylinder 16, as shown in FIG.

In addition, as shown in FIG. 2, the inner cylinder 15 and the outer cylinder 16
In between is a heat-resistant fluororesin such as tetrafluoroethylene,
Alternatively, an insulating ring 25 made of a heat-resistant rubber material such as silicone rubber is inserted, and this insulating ring 25 is fitted onto the inner flange portion 23a of the inner cylinder 15.

On the other hand, as shown in FIGS. 2 and 3, an annular elastic electrode 29 made of graphite is inserted between the inner tube 15 and the outer tube 16. This elastic electrode 2
9 is a cylindrical outer peripheral surface 30 as shown in FIG.
and an inner circumferential surface 31 having a regular octahedral cross section, and are further separated by a slit 32 extending in the axial direction. As can be seen from FIG. 3, this elastic electrode 29 is arranged between the inner tube 15 and the outer tube so that each flat surface constituting the octahedron of the inner peripheral surface 31 faces each flat surface constituting the octahedron of the inner tube 15. It is inserted between 16 and 16. Also,
The axial length of the elastic electrode 29 is shorter than the length of the inner cylinder intermediate portion 15a, and the elastic electrode 29 is disposed within the region of the inner cylinder intermediate portion 15a.

A PTC element 33 is inserted between each flat outer circumferential surface portion of the inner cylinder intermediate portion 15a and the elastic electrode 29, and an insulating member 34 is further inserted so as to surround the outer circumferential wall of each PTC element 33. Insulating member 34
As shown in FIG. 7, the asbestos strip is made of a band-shaped asbestos (the band is shown rolled into an annular shape in FIG. 7), and eight openings 35 are formed at equal intervals.
On the other hand, each PTC element 33 is formed in a flat plate shape with a rectangular outline as shown in FIG.
Each of the four openings 35 has a contour shape that is approximately the same as the contour shape of the PTC element 33. Further, each opening 35 is separated by each equally spaced rib portion 36 . Each flat surface constituting the regular octagon of the insulating member 34 is connected to the inner cylinder 1.
5, respectively arranged on each flat outer peripheral surface constituting a regular octagon, and inside each opening 35 of the insulating member 34.
PTC element 33 is inserted.

An electrode unit 39 is attached to the upper end of the hollow heating element container 14 and extends radially outward. As shown in FIG. 9, this electrode unit 39 includes a metallic U-shaped ring 40 and an insulating tube 41.
A strip-shaped negative lead wire 42 covered with
, a strip-shaped positive lead wire 44 covered with an insulating tube 43, and a connector 47 with a pair of terminals 45 and 46 visible. Insulation tube 4
1 and 43 are stacked on top of each other, and a retainer 48 made of a rubber material is inserted onto the outer periphery of the stacked insulating tubes 41 and 43. As shown in FIG. 9, the inner end 4 of the negative lead wire 42
9 is bent upward at a right angle, and this bent inner end 49
are welded into the U-shaped cross-section of ring 40. Further, the outer end of the negative lead wire 42 is connected to a terminal 45 of a connector 47. On the other hand, the inner end 50 of the positive lead wire 44 is connected to the negative lead wire 4.
The outer end of the positive lead wire 44 is connected to the terminal 46 of the connector 47 . As shown in FIG. 2, the U-shaped cross section of the ring 40 is fitted onto the upper end 16b of the outer cylinder 16, and the outer flange 23b of the inner cylinder 15 is swaged onto the ring 40. On the other hand, the bent inner end portion 50 of the positive lead wire 44 is inserted between the outer cylinder intermediate portion 16a and the elastic electrode 29.

As shown in FIG. 1, a large-diameter hole 51 and a small-diameter hole 52 that are connected to each other are formed in the heat insulating plate 4, and a hollow heating element container 14 is disposed within the large-diameter hole 51. Further, the small diameter hole 52 is arranged in alignment with the secondary air horn 11. Grooves 53 and 54 having an L-shaped cross section are formed along the entire length of the lower part of the inner circumferential wall of the heat insulating plate 4 that defines the large diameter hole 51 and the small diameter hole 52. A flange 20 integrally formed on the outer peripheral wall surface of the outer cylinder 16 is fitted. Further, a dovetail groove 55 is formed on the lower wall surface of the heat insulating plate 4, and the inner part 48b of the retainer 48 is fitted into this dovetail groove 55.

Next, the operation of the above-described intake air heating device will be explained as follows.

The negative lead wire 42 is grounded, and the positive lead wire 44 is connected to a power source 113 via a temperature detection switch 110, a neutral point voltage detection switch 111, and an ignition switch 112.
The temperature detection switch 110 detects, for example, the engine cooling water temperature.
It is on when the temperature is below 60℃, and the engine cooling water temperature is
It turns off when the temperature exceeds 60℃. On the other hand, the neutral point voltage detection switch 111 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 33 when starting current supply, it is necessary to prevent the PTC element 33 from starting supplying current when the starter motor is being driven to start the engine. For this purpose, a neutral point voltage detection switch 111 is provided. That is, when the engine is rotated by the starter motor, the neutral point voltage is low, and when the engine starts operating on its own, the neutral point voltage increases and the neutral point voltage detection switch 111 is turned on.
Supply of current to the PTC element 33 is started. As described above, when the supply of current to the PTC element 33 is started, the temperature of the PTC element 33 immediately rises, and as a result, the temperature of the inner cylinder 15 also rises immediately.

On the other hand, when the engine starts, most of the liquid fuel supplied from the primary side carburetor A descends along the inner wall surface of the primary side air horn 8, and then this liquid fuel flows inside the inner cylinder 15. Descend along the wall. The outer cylinder 16 is formed of a heat insulating plate, and the outer cylinder 15 is supported by the heat insulating plate 4. Therefore, only a small amount of the heat emitted from the PTC element 33 escapes to the intake manifold 2 and the carburetor 6, and most of the heat emitted from the PTC element 33 is used to heat the inner cylinder 15. Furthermore, the inner wall surface of the inner cylinder 15 is covered with liquid fuel, and therefore most of the heat generated from the PTC element 33 is used to vaporize the liquid fuel. In addition, since the inner cylinder middle part 15a bulges inward from the inner cylinder upper end part 15b, fuel droplets floating in the air-fuel mixture tend to adhere to the inner cylinder middle part 15a, thus preventing fuel vaporization. This can be further promoted.

On the other hand, shortly after the engine started, the engine cooling water temperature was 60.
When the temperature rises above .degree. C., the temperature detection switch 110 is turned off and the supply of current to the PTC element 33 is stopped.

As is well known, the thermal conductivity of graphite is directional, and the thermal conductivity in the radial direction is lower than that in the circumferential direction. Therefore, graphite has difficulty in conducting heat in its radial direction, and the elastic electrode 29 has a heat insulating effect. As mentioned above, the outer cylinder 16 is made of a heat insulating material, and since the elastic electrode 29 has a heat insulating effect, the PTC
Most of the heat generated from the element 33 can be used to heat the inner cylinder 15. On the other hand, since graphite conducts heat relatively easily in the circumferential direction, the inner cylinder 15 can be heated uniformly.

[Problem to be solved by the invention]

However, in the above-mentioned intake air heating device, each
The quality of the adhesion between the PTC element 33 and the contact surface portion 15a of the inner cylinder 15, which has a regular octagonal cross section (generally a regular polygon), in other words, the size of the contact area has a great influence on the heat generation characteristics of the entire device. Therefore, a thin material with good heat conductivity is generally used as the inner cylinder member.
These contact surface portions 15a are required to have highly accurate flatness when press-formed into a polygonal shape, but even if accuracy is ensured during press-forming, the press-fitting process during assembly (inner cylinder 15 is Insulating member 34 into which element 33 is fitted and elastic electrode 29
(after being press-fitted into the outer cylinder 16), the polygonal plane portion 15a of the inner cylinder 15 is bent inward as shown in FIG. 10, and a gap 80 is formed between it and the PTC element 33. In this state, not only does the heat transfer efficiency decrease, but also a radial force is applied to the center of the PTC element 33 as shown by the arrow (both during and after press-fitting).
When a force in the direction of the arrow is constantly applied to the PTC element 33 by the elastic electrode 29), the PTC element easily cracks (breaks). Actually PTC
Since the element is made of a brittle ceramic material, a considerable number of such cracks occur.

Therefore, the present invention provides an escape space (recess) on the outer periphery of the insulated electrode so that the deformation and strain caused by the press-fitting load is absorbed by this escape space, thereby ensuring good heat generation characteristics and preventing cracking of the PTC element. This is an attempt to solve the above-mentioned problems.

[Means to solve the problem]

According to this invention, the hollow heating element container disposed in the intake passage leading from the fuel supply device to the engine cylinder includes an inner cylinder and an outer cylinder, and a plurality of PTC elements are arranged between the inner cylinder and the outer cylinder. are arranged in the circumferential direction at predetermined intervals, and an annular elastic electrode connected to an external power source is press-fitted between the PTC element and the outer cylinder, and the inner cylinder has a polygonal cylindrical shape; The inner circumferential surface of the elastic electrode has a polygonal shape similar to the polygonal shape of the inner tube, and the flat PTC element is arranged between the opposing surfaces of the inner tube and the elastic electrode corresponding to the sides of the polygon. In an intake air heating device for an internal combustion engine, in which the PTC element is pressed into contact with an elastic electrode by a cylinder, and the electrode is brought into contact with the PTC element from the periphery thereof, a tube is placed on the outer periphery of the elastic electrode at a position corresponding to each PTC element. An intake air heating device for an internal combustion engine is provided, which is characterized in that recesses are provided and the space formed by the recesses between the elastic electrode and the outer cylinder can absorb deformation and deflection of the elastic electrode.

[Effect]

When the annular elastic electrode is deformed due to the press-fitting load, the recess provided on the outer periphery of the electrode absorbs the deformation.

〔Example〕

As shown in FIG. 11, a plurality of recesses 90 are provided on the cylindrical outer periphery 30 of the graphite electrode 29 at predetermined intervals. The recesses 90 are provided at positions corresponding to each PTC element 33, that is, at positions corresponding to each plane of the polygonal inner peripheral surface 31 of the graphite electrode 29.
Therefore, the graphite electrode 29 is connected to the outer cylinder 16, 16a.
When the graphite electrode is press-fitted, a space 9 corresponding to the recess 90 is formed between the graphite electrode and the outer cylinder as shown in FIG.
1 is formed. The press-fitting load acting on the graphite electrode 29 acts only on the contact portion 29' with the outer cylinder 16, so the graphite electrode 29
The press-fitting load acting on the PTC element 33 via the PTC element 33 is reduced. Furthermore, the contact part, i.e. the load bearing part 2
9' is located at a position corresponding to each vertex of the polygon of the regular polygon inner circumferential surface 31, so the load from the center as shown by the arrow in FIG. 10 no longer acts on the PTC element 33, and as shown in FIG. As shown by the arrows, only the loads near both ends of each PTC element 33 act. Therefore, even if the thin inner portion 15a of the inner tube 15 bends inward as shown in FIG. 13 when the inner tube 15 is press-fitted into the outer tube 16, there is no fear that the PTC element 33 will break. This is because the amount of deflection of the PTC element is maximum when the load application point is at the arrow position shown in FIG. 10, and minimum when the load application point is at the arrow position shown in FIG.

Furthermore, in the case of FIG. 10, the press-fitting load when press-fitting the inner cylinder 15 into the outer cylinder 16 is caused by the inner cylinder 15 being bent radially inward as shown in the figure, since there is no escape route outward in the radial direction. It acts in the direction of increasing In contrast, according to the structure shown in FIG. 13, there is a space 9 between the outer circumference of the graphite electrode 29 and the outer cylinder 16
1, this acts as an escape space, and the flesh of the graphite electrode 29 transfers part of the press-fitting load to the void 9.
1 and absorbs it by escaping into the inner cylinder 15.
The amount of radial inward deflection of is reduced. Therefore, the adhesion between the inner cylinder and the PTC element is good, and the heat transfer efficiency is improved.

Furthermore, even if there is some variation in the press-fitting load, it is effectively absorbed by the recess 90, so that the press-fitting allowance range, that is, the required accuracy of the fitting dimensional tolerance of each part can be relaxed.

Incidentally, the anode 50 may be incorporated into the load bearing portion 29' of the graph isle electrode 29.

〔effect〕

According to this invention, by providing a recess on the outer periphery of the annular elastic electrode at a position corresponding to each PTC element, even if the elastic electrode is deformed during press-fitting, the deformation can be absorbed by the recess, each
While good adhesion of the PTC element to the elastic electrode is maintained, no excessive force is applied to the PTC element, making it possible to prevent cracks and cracks.

[Brief explanation of drawings]

Figure 1 is a side sectional view of the engine intake system according to the applicant's earlier application, Figure 2 is a side sectional view of the heating element container taken along the - line in Figure 3, and Figure 3 is the same as in Figure 2. 4 is a perspective view of the outer cylinder, 5 is a perspective view of the inner cylinder, 6 is a perspective view of the elastic electrode, and 7 is a perspective view of the insulating member during insertion. FIG. 8 is a perspective view of the PTC element, FIG. 9 is a side sectional view of the electrode unit, and FIG. 10 is a perspective view of the intake air heating device shown in FIGS. FIG. 11 is a cross-sectional view showing a part of the graphite electrode of the inner cylinder PTC element and the outer cylinder, FIG. 11 is a perspective view of the graphite electrode according to the present invention, and FIG.
1. FIG. 13 is a cross-sectional plan view of the heating element container incorporating the graphite electrode shown in FIG. 1, and FIG. 13 is an enlarged view of the main part of FIG. 2...Intake manifold, 4...Insulation board, 6...
Vaporizer, 14... Heating element container, 15... Inner cylinder, 1
6... Outer cylinder, 20, 23, 24... Flange, 2
5... Insulating ring, 29... Elastic electrode, 33...
PTC element, 34... Insulating member, 39... Electrode unit, 40... Ring, 90... Recess, 91...
...empty space.

Claims (1)

[Claims] 1. A hollow heating element container disposed in the intake passage leading from the fuel supply device to the engine cylinder includes an inner cylinder and an outer cylinder, and a plurality of PTC elements are arranged at predetermined intervals between the inner cylinder and the outer cylinder. Annular elastic electrodes arranged circumferentially and connected to an external power source are press-fitted between the PTC element and the outer cylinder, the inner cylinder has a polygonal cylindrical shape, and the annular elastic electrodes The inner circumferential surface has a polygonal shape similar to the polygonal shape of the inner cylinder, and the flat PTC element is arranged between the facing surface of the inner cylinder and the elastic electrode corresponding to the side of the polygon, and the PTC element is In an intake air heating device for an internal combustion engine in which the electrode is pressed so as to contact an elastic electrode and the electrode is brought into contact with the PTC element from the periphery thereof, a recess is provided on the outer periphery of the elastic electrode at a position corresponding to each PTC element. An intake air heating device for an internal combustion engine, characterized in that deformation and deflection of the elastic electrode can be absorbed by the space formed between the recess and the outer cylinder.