JPH05256209A - Carburetor for internal combustion engine - Google Patents

Abstract

PURPOSE: To set and optimize the maximum fuel supply quantity by connecting fixed throttles to a main nozzle and an idling chamber at the downstream end and providing an adjustable throttle for reducing the entire flow cross section up to a pregiven minimum value. CONSTITUTION: A throttle valve 4 arranged in an intake duct 2 and a main nozzle 23 communicating with the intake duct 2 in front of the throttle valve 4 in the flow direction 6 of intake air are provided. The maximum flow cross section for fuel supply, in particular, is pregiven by at least one fixed throttle 25, 28. The fixed throttles 25, 28 are connected to the main nozzle 23 and an idling chamber 30 at the downstream end. An adjustable throttle 27 is provided for reducing the entire flow cross section up to a pregiven minimum value. Thus, the maximum fuel supply quantity can be set without the need for a special test in a factory and the fuel supply quantity can be suitably optimized by an operator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a throttle valve arranged in an intake duct, at least one main nozzle leading to the intake duct in front of the throttle valve in the direction of intake air flow, and an area of the throttle valve. In the intake duct, the main nozzle communicates with the adjustment chamber filled with fuel through the fuel duct, and the hole has the adjustment chamber filled with fuel through the idling chamber. The present invention relates to a carburetor for an internal combustion engine, which is in communication with.

[0002]

2. Description of the Related Art German Patent Publication No. 3929025 discloses a carburetor for an internal combustion engine in which a throttle valve is arranged in an intake duct. In the intake duct, at least one idle outflow hole is connected in the area of the throttle valve,
The main nozzle communicates in front of the throttle valve in the suction air flow direction. This main nozzle communicates with the adjustment chamber filled with fuel via a fuel duct, and the idling chamber communicates with the adjustment chamber via a duct provided with a fixed throttle. Between the adjusting chamber and the main nozzle, there is provided a hole whose cross-sectional area can be varied. In this case, the cross-sectional area can be changed by an externally adjustable adjusting screw. The adjusting screw is used to determine the amount of fuel supplied to the intake duct per short time.

In this known arrangement, the maximum and / or minimum allowable fuel quantity must be adjusted when the engine is operating and the operating temperature is at normal temperature.
This means that the work is troublesome. Later, when the operator changes the adjusting screw while the engine is running,
The previously adjusted maximum fuel quantity is not met and a new carburetor must be adjusted with a new measurement.

[0004]

The object of the present invention is to improve this type of carburetor in the following manner, that is to say, it is possible to set the maximum fuel supply amount without requiring a special test process in the factory, It is to improve so that it can be properly optimized by the operator.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides that the maximum flow cross-sectional area for fuel supply is given in advance by at least one fixed throttle, and the fixed throttle is mainly provided downstream. It is characterized in that the nozzle is connected to the idling chamber and that an adjustable throttle is provided to reduce the total flow cross-sectional area to a predetermined minimum value.

According to an advantageous development of the invention, the adjustable throttle is formed by a valve cone formed integrally with the front end of the main adjusting screw and a valve seat provided in the fuel duct.
With this design of the adjustable throttle, a slight rotation of the screw allows fine adjustment of the cross-flow cross-section and thus of the fuel throttle.

Particularly advantageous is the provision of a first fuel duct with a fixed throttle and a second fuel throttle with an adjustable throttle, the second fuel throttle being a fixed throttle of the first fuel duct. Is to form a bypass for. The minimum fuel supply, ie the fuel depletion limit, is set by arranging a fixed throttle in the first fuel duct, and the mixture is controlled by the adjustable throttle in the bypass. Can be thickened in the direction. The maximum aperture of the adjustable diaphragm is achieved, for example, by limiting the distance of the main adjusting screw. However, this is not preferable in all respects. It is therefore expedient to provide the second fuel throttle with a fixed throttle which is functionally arranged in series with respect to the adjustable throttle. As a result, even if the adjustable throttle is opened so as to exceed a certain cross-sectional flow area, the maximum allowable fuel supply amount is not exceeded.

As an alternative to the arrangement described above, a fuel duct is provided which has a fixed throttle which limits the total cross-sectional area and an adjustable throttle which is arranged behind the fixed throttle and which surrounds the adjustable throttle. It is also possible that a flow duct with a cross-sectional area smaller than the cross-sectional area of the fixed throttle is provided. In this configuration, the total amount of fuel is guided by the fixed throttle, so that the fixed throttle has a larger opening cross-section than in the case of the two throttles arranged in parallel. Since the production of a diaphragm with a very small cross-section is difficult and expensive, the arrangement with only one diaphragm has special significance, especially for cost reasons. The flow duct surrounding the adjustable throttle is formed by a hole provided in the center of the front part of the main adjusting screw and a radial hole intersecting this hole.

In another arrangement, two main nozzles are arranged in the region of the Venturi section, a fixed throttle is connected in front of the first main nozzle and an adjustable throttle is connected in front of the second main nozzle. ing. As a result, one of the two main nozzles is not affected by the adjustable diaphragm at all. In such a configuration, the fuel duct extends between the adjustment chamber and the Venturi portion, the fuel duct ends at the first main nozzle, and a fixed throttle is provided in the fuel duct adjacent to the adjustment chamber. A fixed throttle with a smaller cross-sectional area is arranged in front of the first main nozzle, parallel fuel ducts branch between the throttles, the fuel duct leading to the second main nozzle, Advantageously, an adjustable diaphragm is arranged in the duct. Alternatively to this, another fixed throttle and an adjustable throttle are arranged in a second fuel duct which extends parallel to the first fuel duct and leads to the second main nozzle. You can also In order for both main nozzles to be subjected to the same dynamic conditions in the Venturi section, it is advantageous if both main nozzles are provided in one plane with respect to the cross section of the Venturi section.

By virtue of the arrangement of the adjustable iris at the front end of the main adjusting screw, the adjustable iris is between a fully closed first position and a fully open second position. It can be adjusted steplessly. The purpose is to construct the adjustable diaphragm as follows: the effective adjustment range of the adjustable diaphragm between the two positions is approximately 1 of the main adjusting screw.
It corresponds to rotation.

In order to keep all the fuel as accurate as possible, the idling chamber is not directly connected to the regulating chamber as in the past, but rather via a duct, a fuel duct between the fixed throttle and the main nozzle. The purpose is to communicate with the area of. This results in a dependent supply of fuel to the idling chamber, which has no effect on the maximum total supply of fuel. A fixed throttle is provided at an end of the duct for connecting the idling chamber on the fuel duct side, and a throttle adjustable by an adjusting screw is provided after the fixed throttle.

[0012]

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

FIG. 1 shows a vaporizer 1 according to the invention. The carburetor 1 includes an intake duct 2. The intake duct 2 has a Venturi portion 3. Inside the intake duct 2, a throttle valve 4 which is rotatably supported around a shaft 5 is arranged. The carburetor 1 communicates with an intake hole of a cylinder (not shown) of the two-cycle engine. The suction air is sucked in in the flow direction 6 via the Venturi portion 3. The carburetor 1 communicates with a fuel tank via a fuel pipe 10, and is provided with a diaphragm pump 11 for transporting fuel into the control chamber 7 of the carburetor 1. The working chamber 11a of the diaphragm pump 11 is
It communicates with the crankcase of the two-cycle engine via a pipe (not shown), so that the diaphragm pump 11 is driven by the alternating pressure in the crankcase. Diaphragm 11c when negative pressure is present in the crankcase
Is displaced in the direction of the working chamber 11a and, as a result, the pump chamber 11
A negative pressure is generated in c, and the fuel is sucked from the fuel pipe 10 through the check valve 12. When the pressure in the crankcase is excessive, the diaphragm 11c is displaced toward the pump chamber 11b, so that the check valve 12 is closed and the check valve 13 is opened. The fuel is pumped into the pump chamber 11b through the open check valve 13.
Is conveyed to the adjustment chamber 7 through the fuel supply pipe 14.

The outflow end 15 of the fuel supply pipe 14 in the adjusting chamber 7 is closed by a valve body 16. Disc 16
Are supported by lever arms 17. Lever arm 1
7 is rotatably supported by a pin 18, in which case a compression spring 19 biases a lever arm 17 to close the valve body 16. Furthermore, the compression spring 19 presses the free end of the lever arm 17 against a stopper provided in the center of the adjusting diaphragm 20 which defines the adjusting chamber 7. The adjusting diaphragm 20 communicates with the atmosphere or another reference pressure level through an opening 21 provided in the carburetor 1.

The adjusting chamber 7 communicates with the main nozzle 23 by the first fuel duct 22. The main nozzle 23 communicates with the intake duct 2 in the region of the Venturi portion 3. A non-return plate 24, which is not added, is attached to the main nozzle 23. The check plate 24 prevents a change in the pressure of the intake duct 2 from exerting a reaction on the adjustment chamber 7. First
A fixed throttle 25 is provided in the fuel duct 22. The cross-sectional area of the fixed throttle 25 is chosen such that its fuel supply is sufficient to operate the internal combustion engine with as little fuel / air mixture as possible.

Further, a second fuel duct 26 is provided. The second fuel duct 26 leads from the adjusting chamber 7 to the region of the first fuel duct 22 between the fixed throttle 25 and the check plate 24. As can be seen from the enlarged view of FIG.
An adjustable throttle 27 is arranged in the second fuel duct 26. The throttle 27 includes a valve seat 27a and a valve cone portion 2
7b. In this case, the valve cone 27b is integrally formed with the end 8'of the main adjusting screw 8. Although the valve cone 27b is shown in this embodiment, other shapes may be used as long as they achieve the same purpose. By rotating the main adjusting screw 8, the cross-sectional area of the adjustable throttle 27 can be changed, and more strictly, it can be changed until the second fuel duct 26 is completely closed. When the main adjusting screw 8 is rotated in the opposite direction, the valve cone portion 27b is separated from the valve seat 27a. A fixed throttle 28 is provided in front of the adjustable throttle 27 so that the fuel supply does not exceed a predetermined maximum value. The cross-sectional area of the fixed diaphragm 28 determines the effective rotation angle of the main adjusting screw 8. The effective rotation angle of the main adjusting screw 8 is, for example, an angle at which the closing position of the diaphragm 27 is completely rotated, that is, 3
60 ° is the maximum. Further rotation of the main adjusting screw 8 in the "open" direction does not affect the fuel supply to the main nozzle 23.

From the first fuel duct 22, the duct 29
Leads to the idling chamber 30. Idling room 3
A fixed diaphragm 31 and an adjustable diaphragm 32 arranged in series with respect to the fixed diaphragm 31 are provided in the zero position. The idling chamber 30 communicates with the intake duct 2 through the holes 9a, 9b, 9c. Adjustable diaphragm 32
Is formed by a tip portion integrally formed with the end portion of the adjusting screw 33 and a shoulder portion of the duct 29, whereby the amount of fuel supplied to the idling chamber 30 can be adjusted. Since the duct 29 is connected to the first fuel duct 22, the amount of fuel supplied to the idling chamber 30 passes through the fixed throttle 25 and the adjustable throttle 27 or the fixed throttle 28 provided in front thereof. It also depends on the amount of fuel reaching the first fuel duct 22.

The arrangement of the fixed throttles 25 and 28 or the cross-sectional area of their openings determines the maximum supply of fuel and thus also the fuel concentration limit FG of the fuel / air mixture in the intake duct 2. This open position of the adjustable diaphragm 27 is shown in FIG. 3 by the upper half of the main adjusting screw 8. By rotating the main adjusting screw 8, the diaphragm 2
7 through stepless reduction of the cross-flow cross-sectional area of the valve cone 27
b can be brought into contact with the valve seat 27a. In the position shown by the lower half of the main adjusting screw 8, the diaphragm 27 is closed,
The fuel reaches the first fuel duct 22 exclusively through the fixed throttle 25. This corresponds to the fuel depletion limit value MG of the fuel / air mixture.

FIG. 2 shows a modified example of the lower portion of the carburetor 1, which includes an adjusting chamber 7, an outflow end 15 of a fuel supply pipe, a valve body, and
A spring-biased lever arm 17 is shown. The configurations and functions of these components illustrated in FIG. 2 are the same as those in FIG. 1, and thus the same reference numerals are given.
The main nozzle 23 communicates with the control chamber 7 via a fuel duct 34. A fixed throttle 35 is provided at the end of the fuel duct 34 on the adjustment chamber side. An adjustable throttle 27 is located in series with the fixed throttle 35 when viewed in the flow direction.
The adjustable throttle 27 has, according to FIG. 4, a valve seat 27a and a valve cone 27b. Inside the valve cone 27b,
That is, inside the front part 8'of the main adjusting screw 8, a hole 36 is provided in the center and a radial hole 37 intersecting with this hole 36 is provided, so that the through-flow cross section is constant. A flow duct is formed parallel to the adjustable throttle 27. Also in this embodiment, the effective rotation angle of the main adjusting screw 8 is limited, and for example, it is completely 1 from the closed position to the "open" direction.
Limited to rotate. Further rotation of the main adjusting screw 8 renders the above limitation ineffective because the maximum cross-sectional area is determined by the fixed throttle 35. When the adjustable throttle 27 is fully open, the engine has the richest fuel mixture. That is, the allowable fuel concentration limit value FG
Is achieved. This state is shown in FIG.
Shown by the upper half. However, the adjustable throttle 27 is closed further, and a smaller amount of fuel is
The fuel-air mixture, which flows through the fuel cell 7, may be adjusted to a fuel-deficient state. The flow duct formed by the holes 36 and 37 remains constant, ensuring sufficient fuel supply at the fuel depletion limit MG even when the adjustable throttle 27 is closed.

As shown in FIG. 5, two main nozzles 41 and 41 'are arranged in the region of the venturi portion 3. These main nozzles 41, 41 'are connected to the fuel duct 43.
Alternatively, it communicates with the adjustment chamber 7 via 43 '. The fuel duct 43 is provided with a fixed throttle 45 extending from the adjusting chamber 7. The fixed throttle 45 determines the maximum fuel supply amount. On the downstream side of the fixed throttle 45, the fuel duct 43 ′ and the duct 29 including the fixed throttle 31 are branched. The duct 29 communicates with the idling chamber. Another fixed throttle 40 is provided at another portion of the fuel duct 43. The fixed throttle 40 determines the minimum fuel supply and therefore has a smaller cross-sectional area than the fixed throttle 45. At the end of the fuel duct 43, the first main nozzle 4
1 is arranged. An adjustable throttle 42 is provided in the parallel fuel ducts 43 '. Depending on the opening degree of this adjustable throttle 42, fuel is additionally supplied to the second main nozzle 4
It is supplied to the venturi section 3 via 1 '.

Instead of disposing the duct 29 communicating with the idling chamber, a duct 29 'can be connected between the fixed throttle 40 and the first main nozzle 41 as shown by the broken line in FIG. The flow direction of the Venturi part 3 is
This corresponds to the direction indicated by arrow 6 in FIG. That is, the main nozzles 41 and 41 'are located in series in the flow direction of the intake air.

FIG. 6 shows two main nozzles 41 or 41 '.
The main nozzles 41, 41 ′ are in one plane with respect to the shape of the cross section of the venturi portion 3. A fixed throttle 40 is provided in the fuel duct 43 which is not branched in this embodiment. This fixed throttle 40 determines the minimum fuel flow and thus the fuel depletion limit of the mixture. A parallel fuel duct 43 ′ extends from the regulating chamber 7 to the second main nozzle 41 ′, in this case the fuel duct 4 ′.
A fixed diaphragm 46 and an adjustable diaphragm 42 are arranged in series at 3 '. Therefore, the air-fuel mixture can be adjusted between the fuel depletion limit value and the fuel concentration limit value according to the opening degree of the adjustable throttle 42. Between the fixed throttle 46 and the adjustable throttle 42 of the fuel duct 43 ′ is the connecting part of the duct 29 leading to the idling chamber.

FIG. 7 shows the relationship between the fuel supply amount (kg / h) and the rotation of the adjustable throttle or the main adjusting screw. With the adjustable diaphragm closed, the main adjusting screw is in position "0". This means that the fuel supply amount is the smallest, and M is different from that of the different embodiment.
Shown as G1 and MG2. As you can see from Figure 7,
The maximum effective diaphragm opening is achieved when the main adjusting screw has made almost one revolution. This is shown by the fuel concentration limit values FG1 and FG2. The curve extends approximately proportionally between the fuel depletion limit value MG1 or MG2 and the associated fuel concentration limit value FG1 or FG2.

Next, advantageous structures of the present invention will be listed.

(1) Adjustable throttles (27) are provided on the valve cone (27b) and the fuel ducts (26, 34) integrally formed on the front end (8 ') of the main adjusting screw (8). Vaporizer for an internal combustion engine, characterized in that it is formed by a valve seat (27a).

(2) A first fuel duct (22) with a fixed throttle (25) and a second fuel throttle (26) with an adjustable throttle (27) are provided for the second fuel. The throttle (26) is a fixed throttle (2) of the first fuel duct (22).
5) A carburetor for an internal combustion engine according to item 1 above, characterized in that it forms a bypass for 5).

(3) The second fuel throttle (26) is provided with a fixed throttle (28) which is functionally arranged in series with respect to the adjustable throttle (27). A carburetor for an internal combustion engine according to item 2.

(4) Fuel duct (34) with fixed throttle (35) limiting the total cross-sectional area and adjustable throttle (27) arranged behind the fixed throttle (35).
Is provided and surrounds the adjustable throttle (27) and is provided with a flow duct with a cross-sectional area smaller than the cross-sectional area of the fixed throttle (35). Vaporizer for internal combustion engine.

(5) The flow duct has a hole (36) provided at the center of the front portion (8 ') of the main adjusting screw (8) and a radial hole intersecting with this hole (36). (37) The carburetor for an internal combustion engine as described in the above item 4, characterized in that:

(6) Two main nozzles (41, 41 ') are arranged in the region of the venturi portion (3), a fixed throttle (40) is connected in front of the first main nozzle (41), and a second main nozzle (41) is connected.
Carburetor for an internal combustion engine, characterized in that an adjustable throttle (42) is connected in front of the main nozzle (41 ') of the.

(7) A fuel duct (43) extends between the adjusting chamber (7) and the venturi portion (3), the fuel duct (43) ending at the first main nozzle (41). A fixed throttle (45) is arranged in the fuel duct (43) adjacent to the adjusting chamber (7), and the first main nozzle (41)
A fixed throttle (40) with a smaller cross-sectional area is located in front of the fuel duct (43 ') in parallel between the throttles (40, 45).
3 ') leads to a second main nozzle (41') and an adjustable throttle (42) is arranged in the fuel duct (43 '). Carburetor of the engine.

(8) Another fixed throttle (46) in the second fuel duct (43 ') extending parallel to the first fuel duct (43) and communicating with the second main nozzle (41'). ) And an adjustable diaphragm (42) are arranged,
The carburetor for an internal combustion engine according to the above item 6.

(9) In the above item 6 or 8, the main nozzles (41, 41 ') are provided in one plane with respect to the cross section of the venturi portion (3). Vaporizer for an internal combustion engine as described.

(10) Adjustable diaphragm (27, 42)
Is steplessly adjustable between a fully closed first position and a fully open second position, any of the above items 1 to 9 A carburetor for an internal combustion engine according to any one of the above.

(11) The effective adjustment range of the adjustable diaphragm (27) between the two positions corresponds to about one revolution of the main adjusting screw (8). A carburetor for an internal combustion engine according to the item.

(12) The idling chamber (30) is connected to the fixed throttle (25, 35, 45, 4) via the duct (29).
6) and the main nozzles (23, 41, 41 ') are communicated with the region of the fuel ducts (22, 34, 43, 43'), characterized by the above items 1 to 12 A carburetor for an internal combustion engine according to any one of 1.

(13) A fixed throttle (31) is provided at the end of the duct (29) on the fuel duct side.
1) A diaphragm (32) adjustable by an adjusting screw (33) is provided after 1).
A carburetor for an internal combustion engine according to item 2.

[0038]

The main advantages of the present invention are that the carburetor is set to the maximum fuel supply amount in the factory, that is, the so-called fuel concentration limit value, and the fuel supply amount is set to the minimum value. In the direction of the so-called fuel depletion limit. In this way, the power machine meets stringent emission regulations.

[Brief description of drawings]

1 is a cross-sectional view of a vaporizer according to the present invention.

FIG. 2 is a diagram showing a modified embodiment of a diaphragm.

FIG. 3 is an enlarged view of the diaphragm of FIG.

FIG. 4 is an enlarged view of the diaphragm of FIG.

FIG. 5 is a diagram showing a modification of FIG. 4 in which two main nozzles are provided.

FIG. 6 is a diagram showing a modified example of FIG.

FIG. 7 is a graph showing a relationship between a fuel consumption amount and a main adjusting screw.

[Explanation of symbols]

1 Vaporizer 2 Intake duct 4 Throttle valve 6 Suction air flow direction 7 Adjustment chamber 22, 26, 34, 43, 43 'Fuel duct 23, 41, 41' Main nozzle 25, 28, 35, 40, 45, 46 Fixed throttle 27,42 Adjustable diaphragm 30 Idling chamber

Claims (1)

[Claims] 1. A throttle valve (4) arranged in the intake duct (2) and at least one communicating with the intake duct (2) in front of the throttle valve (4) in the intake air flow direction (6). Having one main nozzle (23, 41, 41 ') and a hole (9a) leading to the intake duct (2) in the area of the throttle valve (4), the main nozzle (23, 41, 41')
Through the fuel ducts (22, 26, 34, 43, 43 ') to the adjustment chamber (7) filled with fuel, and the hole (9a) through the idling chamber (30) In a carburetor of an internal combustion engine, which communicates with a regulating chamber (7) which is filled with a fixed throttle (25, 28, 35, 40, 45, 46) having a maximum flow cross-sectional area for fuel supply of at least one. Given in advance by the fixed diaphragm (25, 2
8, 35, 40, 45, 46) downstream of which the main nozzle (23, 41, 41 ') is connected to the idling chamber (30), reducing the total flow cross-sectional area to a predetermined minimum value Vaporizer for an internal combustion engine, characterized in that an adjustable throttle (27, 42) is provided.