JPS6221731Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a butterfly throttle valve type carburetor, and more particularly to a carburetor that is provided with anti-freezing measures in the fuel injection area during low-load operation of an engine.

In a butterfly-type throttle valve carburetor equipped with a pilot fuel supply system, when the engine is operating at low load, the tip of the throttle valve in the carburetor intake passage is located close to the bypass port opening into the intake passage. Due to the negative pressure generated in the gap between the tip of the throttle valve and the intake passage, pilot fuel is injected from the pilot fuel supply system into the intake passage through the bypass port and is atomized. During this low-load operation, if the atmosphere is low and humid, moisture contained in the intake air may freeze near the bypass port due to the latent heat of vaporization of the fuel ejected from the pilot port. In other words, when moisture freezes and accumulates in the gap between the inner surface of the intake passage and the outer peripheral tip of the throttle valve, the ratio of pilot fuel to intake air becomes large, and as a result, the air-fuel mixture supplied to the engine becomes too rich, causing engine damage. Makes low load operation malfunction. In addition, if water freezes on the bypass port itself, the amount of pilot fuel supplied will decrease or become zero, resulting in a lean mixture supplied to the engine, which will cause the engine to malfunction or become inoperable at low load. or

Therefore, as a means to prevent moisture from freezing inside the bypass port and from freezing moisture in the gap between the inner surface of the intake passage and the tip of the throttle valve, the entire outer circumference of the housing at the location where the bypass port is formed is One idea was to install a heater in the pilot fuel passage, or to insert a heat transfer member into the pilot fuel passage and heat one end of the heat transfer member with a heater. However, in the former case, in order for the heater to heat the bypass port and intake passage, it is necessary to heat the entire wall thickness of the housing, and the heat from the heater cannot be efficiently applied to the designated area, and furthermore, The heating effect could not be achieved. In the latter case, the heat transfer member is placed closer to the bypass port or throttle valve, but the structure is complicated and the amount of heat is limited, making it impossible to achieve the purpose.

For this reason, an improvement was proposed in U.S. Pat.
No. 170962. An embodiment of the vaporizer according to this application is shown in FIG. 1 as a partially sectional front view.

The carburetor housing 10 has an intake passage 12 therein, a vent 14 is formed in the center of the intake passage 12, and a main nozzle 18 for supplying fuel from a fuel chamber 16 projects from its throat. There is. A throttle valve 22 rotatably supported by a throttle valve shaft 20 is provided in the intake passage 12 on the downstream side of the ventilate 14 . Throttle valve shaft 20
A through hole 24 having a larger diameter on the outside and a smaller diameter on the inside is formed in the housing 10 perpendicularly to the axial direction of the intake passage 12 from the outer circumferential wall of the housing 10 toward the intake passage 12 . A pilot fuel passage 26 is formed within the housing 10 and communicates with the fuel chamber 16, and communicates with an idle port 28 which traverses the hole 24 and opens into the intake passage 12 at a position downstream of the throttle shaft 20.

In the hole 24 of the housing 10, there is a passage 30 for communicating the pilot fuel passage 26 and the idle port 28, and an intake passage 1 branching from the passage 30.
a bypass block 36 having two bypass ports 32 opening to the bypass ports 32 and a recess 34 bored on the opposite side of the bypass port 32 with the passage 30 as the center, and the recess 3 of the bypass block 36;
A heater unit 42 is installed, which includes a heater 38 disposed within the bypass block 36 and a heat insulating material 40 attached to cover the vicinity of the housing position of the heater 38 in the bypass block 36. The outer shape of the bypass block 36 also has a large diameter portion and a small diameter portion corresponding to the hole 24 so that the heater unit 42 engages with the housing 10. That is, bypass block 3
6 is separated from the housing 10 by a heat insulating material 40 at its large diameter portion, but is in contact with the housing 10 at its stepped portion and small diameter portion. The bypass block 36 is made of a highly thermally conductive material such as steel, copper, zinc, or aluminum. A hole 44 is formed in the heat insulating material 40 at a position corresponding to the pilot fuel passage 26. The heater 38 is connected to a power source (not shown) through a lead wire 46.

In this way, the bypass block with the bypass port is made of a material with high thermal conductivity, and by covering the area around the bypass block's heater installation position with a heat insulating material, the heat of the heater is not dissipated to the outside, and the bypass port etc. can be given to Therefore, it was possible to heat the bypass port etc. in a short time and with a small amount of electric power, and the above-mentioned drawbacks could be solved.

However, even in this configuration, since the small-diameter portion and step portion of the bypass block are in contact with the housing, a portion of the heat from the heater escapes from the bypass block to the housing. Therefore, although the heat transferred to the housing helps to melt the ice between the throttle valve and the housing wall of the intake passage, a large amount of heat is lost by conduction from the bypass block to the housing, causing A problem occurred in which it took time for the ice in the bypass port to melt. The present invention improves the above structure by eliminating the direct contact between the housing and the bypass block so that the heat of the heater can be applied to the bypass port etc. more efficiently.Next, the present invention will be explained based on the drawings. do.

FIG. 2 is an enlarged cross-sectional view of an embodiment showing essential parts of a vaporizer according to the present invention, and the same reference numerals as in FIG. 1 indicate the same parts. From the outer peripheral wall of the housing 10 to the intake passage 1
Through hole 2 with a larger diameter on the outside and a smaller diameter on the inside
4' is formed. Heater unit 42'
includes a passage 30 leading to the pilot fuel passage 26 and two bypass ports 3 branching from the passage 30.
2 and the bypass port 3 centered on the above passage 30.
a bypass block 36' having a recess 34 bored on the opposite side of the bypass block 2; a heater 38 disposed in the recess 34 of the bypass block; material 40', and is installed in the hole 24'. The heater unit 42' is connected to the housing 10.
The bypass block 36' is also formed with a large diameter part and a small diameter part so as to be locked in the hole 24' in the housing 10. However, the bypass block 36' has an O-ring 5 for preventing fuel leakage at its step.
0 to the housing 10. That is,
Step of bypass block 36' and housing 10
Direct contact with the step of the inner hole 24' is avoided. Also, between the small diameter portion of the bypass block 36' and the housing 10, there is an O-
A gap 52 extending to the lower side of the ring 50 is formed. On the other hand, the heat insulating material 40' covers a large diameter portion of the side surface of the bypass block 36', and its lower end contacts and covers the outer periphery of the O-ring 50. A hole 54 is formed in the heat insulating material 40' at a position corresponding to the pilot fuel passage 26, and an O-ring 56 for preventing fuel leakage is arranged on the outer periphery of the insulating material 40' above the position where the hole is formed.

With the structure described above, the bypass block 36' is separated from the housing 10 by the heat insulating material 40' and the O-
They are separated by a ring 50 and a gap 52, so they do not come into direct contact. Therefore, the heat from the heater 38 is not conducted to the housing 10 and is accumulated only in the bypass block 36', so that the bypass port etc. can be heated in a shorter time and with less electric power. In addition, instead of covering the small diameter portion of the bypass block 36' near the intake passage 12 with the heat insulating material 40', the gap 52 is
Since the bypass block 36' is separated from the housing 10 by radiation, the heat of the bypass block 36' can be transferred to the housing 10 by radiation, and the ice between the throttle valve 22 and the housing wall of the intake passage 12 can be melted. It can be promoted. As a result, the portion of the housing 10 near the bypass block 36' is slightly warmed, and freezing can be prevented between the slot valve 22 and the bypass block 36' and the housing 10 in the vicinity.

As a result of the experiment, the gap of the gap 52 is the minimum value.
It is appropriate that it be within the range of 0.035 mm and a maximum value of 0.115 mm. If this distance is smaller than the minimum value above, heat will escape to the housing,
On the other hand, if the gap exceeds the above-mentioned maximum value, intake air will enter the gap, disrupting the airflow and impairing uniformity.

Although there are no particular limitations on the above-mentioned heater, a ceramic heater based on a ceramic substrate made of barium, titanium, or the like having positive electrical resistance to temperature may be used. This ceramic heater has a characteristic that its resistance value is small at low temperatures and its resistance value is large at high temperatures, so the lower the temperature of the atmosphere, the higher the heat it emits. Therefore, the use of a ceramic heater is suitable for the purpose of the present invention, which requires rapid heating at low temperatures.

Note that in order to automatically start heating the heater, the electric circuit closing operation of the heater may be performed in conjunction with the operation of the main switch of the engine.

[Brief explanation of drawings]

Fig. 1 is a partial front sectional view showing a conventional carburetor;
FIG. 2 is an enlarged sectional view of the main parts of the vaporizer according to the present invention. 10...Housing, 24'...Through hole, 32
...Bypass port, 36, 36'... Bypass block, 38... Heater, 40, 40'...
Insulation material, 42, 42'...Heater unit, 5
0...O-ring, 52...Gap.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A stepped through hole is formed in a carburetor body having an intake passage, the diameter being large on the outside side leading from the outside of the body to the intake passage, and the diameter being small on the intake passage side. In the carburetor, a bypass block having a heater built therein and a heat insulating material attached to the outside is installed in the through hole, and a slow system fuel bypass port opening to the intake passage is formed inside the bypass block. A heat insulating material is interposed between the bypass block and the housing on the outside side of the through hole, and a gap communicating with the intake passage is formed between the wall surface of the through hole and the bypass block on the intake passage side of the through hole, A carburetor characterized in that the gap and the heat insulating material separate the bypass block and the housing so that they do not come into direct contact with each other. (2) A stepped portion consisting of a large diameter portion and a small diameter portion is formed on the outer surface of the bypass block, and a sealing member is provided between the stepped portion of the bypass block and the stepped portion of the through hole. A vaporizer according to claim 1 of the utility model registration claim. (3) The width of the gap is from 0.035mm to 0.115mm
The vaporizer according to claim 1, characterized in that the vaporizer is between millimeters. (4) The vaporizer according to claim 1, wherein the heater is a ceramic heater.