JPH018689Y2 - - Google Patents

Description

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

B. Prior Art Conventionally, a cylindrical positive temperature coefficient heating element (hereinafter referred to as a PTC heating element) 3 is provided between the downstream of the intake pipe 1 and the upstream of the intake manifold 2 of a carburetor. There is an intake air heating device that heats the air-fuel mixture by generating heat. In the intake air heating device, the conventional PTC heating element is gasoline,
There are some that are covered with an inner cylinder to prevent direct contact with oil, exhaust gas, etc. (for example,
However, in this case, the heat transfer efficiency to the air-fuel mixture is poor due to the presence of the inner cylinder. Therefore, in recent years, it has been proposed that the inner surface of a PTC heating element is brought into direct contact with the flowing air-fuel mixture to increase the efficiency of heat transfer to the air-fuel mixture (for example, Japanese Utility Model Publication No. 88937/1983). In this case, a flange-shaped seat 5 is provided at the lower end of the outer cylinder 4 to protrude inward, and the inner diameter of the inner end surface 5a of the seat 5 is made to match the inner diameter of the inner circumferential surface 3a of the PTC heating element 3. , by the seat 5
A heating unit is configured by supporting a PTC heating element 3. However, if the inner diameter of the inner end surface 5a of the seat 5 matches the inner diameter of the inner circumferential surface 3a of the PTC heating element 3, the accuracy of the shape and dimensions (inner diameter, outer diameter, roundness) of the PTC heating element 3 can be maintained. be difficult;
Due to variations in fitting or casting of the PTC heating element 3 into the outer cylinder 4, as shown in FIG. It may protrude outward. When the inner end surface 5a of the seat 5 protrudes in this way,
The fuel is placed on the upper surface of the protruding seat 5 as shown in FIG.
The fuel accumulates as shown in the figure, and this fuel intermittently turns into coarse particles and drips down, changing the air-fuel ratio and distribution.
Particularly in the idling range, there is a problem in that the rotation of the engine becomes unstable and drivability deteriorates.

C. Purpose of the invention In view of the above, the present invention is designed to prevent variations in the shape and dimensions of the PTC heating element and variations in fitting or casting into the outer cylinder in a device in which the inner circumferential surface of the PTC heating element is exposed so as to come into contact with the air-fuel mixture. Even when this occurs, the inner end surface of the seat in the outer cylinder is prevented from protruding from the inner circumferential surface of the PTC heating element, thereby preventing deterioration of drivability due to fuel dripping as in the conventional case. The primary purpose is to Second, we aim to ensure a stable fuel supply by avoiding eccentricity between the intake cylinder and the PTC heating element during assembly and by making the flow uniform around the PTC heating element.
The purpose of

D. Structure of the invention In order to achieve the above-mentioned purpose, the present invention
A heating unit of the heating element 3 is fixed in the outer cylinder 4 so that the entire inner circumferential surface 3a thereof is exposed to the air-fuel mixture passage, and the heating unit is fixed between the intake cylinder 1 and the intake manifold 2 via the heat insulating material 7. In this case, a seat 5 that supports the lower surface of the PTC heating element 3 is protruded inward from the lower end of the outer cylinder 4, and an inner end surface 5 of the seat 5 is provided.
The inner diameter of a is smaller than the outer diameter of the PTC heating element 3,
The inner diameter of the PTC heating element 3 is set larger than that of the PTC heating element 3. Furthermore, a collar 4a is provided on the outer circumference of the upper part of the outer cylinder 4, and an annular recess 7a that fits with the collar 4a is provided on the heat insulating material 7. It is characterized in that it is fixedly installed between the intake manifold 2 and the intake manifold 2 with bolts 8.

E. Example In Fig. 3, 3 is a PTC heating element, which is fixed to the outer cylinder 4 by fitting or casting, with its inner circumferential surface 3a exposed so as to be in direct contact with the flowing air-fuel mixture. It constitutes a heating unit 34. A brim-shaped seat 5 that protrudes inward is integrally formed at the lower end of the outer cylinder 4.
A PTC heating element 3 is supported. The inner diameter of the inner end surface 5a of the seat 5 is set to be smaller than the outer diameter of the outer peripheral surface 3b of the PTC heating element 3 and larger than the inner diameter of the inner peripheral surface 3a of the PTC heating element 3.
The PTC heating element 3 is connected to an electrode terminal 6 integrally formed on the outer cylinder 4, and generates heat when energized. The outer cylinder 4 has a collar 4 on its upper outer periphery.
It is equipped with a.

As shown in FIG. 1, such a heating unit 34 is fixedly installed between the intake pipe 1 and the intake manifold 2 of the carburetor with a heat insulating material 7 interposed therebetween. The heat insulating material 7 has an annular recess 7 that fits into the collar 4a.
The collar 4a of the outer cylinder 4 is fitted into the annular recess 7a, and the lower surface thereof is brought into contact with the upper end of the intake manifold 2 via a packing. The heat insulating material 7 is then properly fixed between the intake pipe 1 and the intake manifold 2 with bolts 8.

F. Effect of the invention As described above, in the present invention, the inner diameter of the inner end surface 5a of the seat 5 formed at the lower end of the outer cylinder 4 is set to be smaller than the outer diameter of the PTC heating element 3 and larger than the inner diameter of the PTC heating element 3. Therefore, variations in the shape and dimensions of the inner diameter, outer diameter, and roundness of the PTC heating element 3 and PTC
Even if there are variations in fitting or casting of the heating element 3 into the outer cylinder 4, the inner end surface 5a of the seat 5
The PTC heating element 3 does not protrude inward from the inner circumferential surface 3a. Therefore, the fuel adhering to the inner circumferential surface 3a of the PTC heating element 3 and the fuel flowing near the inner circumferential surface 3a do not hit the seat 5 but flow down by the intake air flow. In addition, since the heating unit 34 in which the PTC heating element 3 is integrally coupled to the outer cylinder 4 is positioned by fitting the collar 4a and the annular recess 7a, the inner circumference of the PTC heating element 3 is aligned with respect to the inner periphery of the intake cylinder 1. Since the circumferential surface 3a is accurately positioned without eccentricity, the air-fuel mixture flows uniformly and smoothly along the inner circumferential surface 3a. This eliminates the phenomenon of fuel accumulating on the protruding seat 5 and dripping as in the past, and instead is continuously supplied as fine fuel particles, with no changes in the air-fuel ratio or distribution, and the engine rotation is stabilized. It has the advantage of improving drivability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an intake air heating device equipped with a PTC heating element, FIG. 2 is a sectional view of the heating unit used in FIG. 1, and FIG. 3 is a sectional view of the heating unit according to the present invention. 1... Intake cylinder, 2... Intake manifold, 3... PTC heating element, 3a... Inner peripheral surface, 3b
...Outer peripheral surface, 4... Outer tube, 4a... Brim, 5...
Seat, 5a... Inner end surface, 7... Heat insulating material, 7a... Annular recess, 8... Bolt, 34... Heating unit.

Claims (1)

[Scope of utility model registration request] A heating unit of the PTC heating element 3 is fixed in the outer cylinder 4 so that the entire inner circumferential surface 3a thereof is exposed to the air-fuel mixture passage, and the heating unit is fixed between the intake cylinder 1 and the intake manifold 2 via the heat insulating material 7. A seat 5 for supporting the lower surface of the PTC heating element 3 is protruded inward from the lower end of the outer cylinder 4, and the inner diameter of the inner end surface 5a of the seat 5 is smaller than the outer diameter of the PTC heating element 3. The inner diameter of the PTC heating element 3 is set larger than that of the PTC heating element 3. Furthermore, a collar 4a is provided on the outer circumference of the upper part of the outer cylinder 4, and an annular recess 7a that fits with the collar 4a is provided on the heat insulating material 7. An intake air heating device for an internal combustion engine, characterized in that it is fixedly installed between an intake manifold 2 and an intake manifold 2 with bolts 8.