JP4918304B2 - Multi-cylinder dual fuel engine - Google Patents

Description

  The present invention relates to a multi-cylinder dual fuel engine, and more particularly, a multi-cylinder dual fuel engine that can more uniformly distribute an air-fuel mixture to each cylinder and can improve exhaust gas performance during gas fuel operation. It is about.

As a conventional multi-cylinder dual fuel engine, as in the present invention, an intake distribution passage is attached to a cylinder head, and an air-fuel mixture is distributed to a plurality of cylinders by this intake distribution passage. There is one in which a throttle body is attached and liquid fuel and gas fuel are switched and supplied to the throttle body (see, for example, Patent Document 1).
This type of multi-cylinder dual fuel engine can be mounted on a forklift or the like to ensure excellent exhaust gas characteristics using gas fuel for indoor work and liquid power for outdoor work to ensure excellent output characteristics. There are advantages you can do.

  However, the above conventional multi-cylinder dual fuel engine has a problem because a carburetor is used to supply liquid fuel to the throttle body, and the liquid fuel outlet and the gas fuel outlet face the same venturi passage. is there.

Japanese Patent Laid-Open No. 10-220295 (see FIGS. 1 and 2)

The above prior art has the following problems.
<Problem> There is a possibility that the distribution of the air-fuel mixture to each cylinder may become uneven.
Since the carburetor is used to supply the liquid fuel to the throttle body, the atomization of the liquid fuel is insufficient, and the concentration distribution of the air-fuel mixture in the intake air distribution passage tends to be uneven. Distribution may be uneven.

<< Problem >> There is a risk of reducing exhaust gas performance during gas operation.
Since the liquid fuel outlet and the gas fuel outlet face the same venturi, the liquid fuel easily enters the gas fuel outlet during the liquid fuel operation. Therefore, immediately after switching from the liquid fuel operation to the gas fuel operation, the liquid fuel that has entered the gas fuel outlet flows into the throttle intake passage together with the gas fuel, the mixture becomes excessive, and the exhaust gas during the gas fuel operation May reduce performance.

  The present invention is a multi-cylinder dual fuel engine that can solve the above problems, that is, the distribution of the air-fuel mixture to each cylinder can be made more uniform, and the exhaust gas performance during gas fuel operation can be improved. An object of the present invention is to provide a multi-cylinder dual fuel engine that can be used.

As illustrated in FIG. 6, an intake air distribution passage (2) is attached to the cylinder head (1), and the air-fuel mixture is distributed to a plurality of cylinders (3) through the intake air distribution passage (2). As illustrated, a throttle body (5) is attached to a single distribution passage inlet (4) of the intake distribution passage (2), and liquid fuel and gas fuel are switched and supplied to the throttle body (5). In a multi-cylinder dual fuel engine,
As illustrated in FIGS. 1A and 1B, a throttle intake passage (6) is provided in the throttle body (5), and a throttle valve (7) is disposed in the throttle intake passage (6). An injector (8) is attached to the throttle body (5), and the tip (9) of the injector (8) faces the throttle intake passage (6) downstream of the throttle valve (7). 8) Open the liquid fuel injection port (10) at the tip (9),
As shown in FIG. 1 (A), an intake pipe connection pipe (34) is attached to the intake passage inlet (6b) of the throttle intake passage (6) of the throttle body (5), and this intake pipe connection pipe (34) is attached. An intake pipe (35) led out from an air cleaner is connected, a gas fuel outlet (11) is provided in the intake pipe connection pipe (34), and the gas fuel outlet (11) is upstream of the throttle valve (7). It faced in the said intake pipe connection pipe (34).

As illustrated in FIG. 1A, an intake pressure detection sensor (15) for detecting the intake pressure of the throttle intake passage (6) and an engine speed sensor (16) for detecting the engine speed are controlled by a control means ( 17), the control means (17) controls the liquid fuel injection amount from the injector (8) based on the intake pressure and the engine rotational speed.

  The intake pressure detection sensor (15) is attached to the throttle body (5) together with the injector (8),

  An intake pressure introduction passage (18) for introducing the intake pressure in the throttle intake passage (6) to the intake pressure detection sensor (15) is provided in the peripheral wall of the throttle intake passage (6) of the throttle body (5),

  A multi-cylinder dual, characterized in that a passage inlet (18a) of the intake pressure introduction passage (18) is opened on the inner peripheral surface of the throttle intake passage (6) upstream of the injector (8). Fuel engine.

(Invention according to Claim 1)
< Effect > Distribution of the air-fuel mixture to each cylinder can be made more uniform.
As illustrated in FIGS. 1A and 1B, the tip end portion 9 of the injector 8 faces the throttle intake passage 6 downstream of the throttle valve 7, and the injector 8 Since the liquid fuel injection port (10) is opened at the front end portion (9) of the fuel, fine oil droplets of the liquid fuel injected from the liquid fuel injection port (10) are generated downstream of the throttle valve (7). Involved in (turbulent flow), atomization of liquid fuel is promoted, the concentration distribution of the mixture in the intake distribution passage (2) becomes more uniform, and the distribution of the mixture to each cylinder (3) becomes more uniform Can be.

< Effect > The exhaust gas performance at the time of gas operation can be improved.
As illustrated in FIG. 1A, since the gas fuel outlet (11) faces the intake pipe connection pipe (34) upstream from the throttle valve (7), a part of the liquid fuel is inhaled. Even if the pulsation causes a reverse flow upstream of the throttle intake passage (6), the liquid fuel is blocked by the throttle valve (12) and hardly enters the gas fuel outlet (11). Therefore, even when switching from the liquid fuel operation to the gas fuel operation, the problem that the liquid fuel that has entered the gas fuel outlet (11) flows out into the throttle intake passage (6) together with the gas fuel is avoided, and the exhaust gas during the gas operation is avoided. Performance can be improved.

< Effect > The fuel supply device can be made compact.
As illustrated in FIG. 1A, the injector (8) is attached to the throttle body (5), and the gas fuel outlet (11) is provided in the intake pipe connection pipe (34) attached to the throttle body (5). The fuel supply parts are integrated into the throttle body (5), and the fuel supply device can be made compact. Further, since the gas fuel outlet (11) is provided, it is not necessary to improve the throttle body (5).

<Effect> The function of distributing the air-fuel mixture more uniformly to each cylinder is high.
As illustrated in FIG. 1A, the passage inlet (18a) of the intake pressure introduction passage (18) is opened on the inner peripheral surface of the throttle intake passage (6) upstream of the injector (8). Therefore, the liquid fuel injected from the liquid fuel injection port (10) of the injector (8) is moved away from the passage inlet (18a) of the intake pressure introduction passage (18) by the flow of intake air, and the intake pressure introduction passage (18). Liquid fuel is difficult to enter. For this reason, the detection of the intake pressure by the intake pressure detection sensor (15) is stabilized, there is no problem that the fuel injection amount from the injector (8) fluctuates unnecessarily, and the air-fuel mixture is more evenly distributed to each cylinder (3). High functionality.

<Effect> The fuel supply device becomes compact.
As illustrated in FIG. 1A, since the intake pressure detection sensor (15) is attached to the throttle body (5) together with the injector (8), the fuel supply related parts are integrated into the throttle body (5) and the fuel is supplied. The supply device becomes compact.

(Invention according to Claim 2 )
In addition to the effect of the invention according to claim 1 , the following effect is achieved.
<Effect> The function of distributing the air-fuel mixture more uniformly to each cylinder is high.
Since the direction of the intake pressure introduction passage (18) is set so that the angle formed by the intake pressure introduction passage (18) is 45 ° or more with respect to the transverse extension line (19a) illustrated in FIG. 4 (A). Even if the direction of the intake pressure introduction passage (18) is closer to the tangential direction than the radial direction of the throttle intake passage (6) and the passage cross-sectional area of the intake introduction passage (18) is reduced, the intake pressure introduction passage (18) The opening area of the passage inlet (18a) can be increased. For this reason, the passage cross-sectional area of the intake introduction passage (18) is reduced to make it less susceptible to the influence of intake pressure pulsation, and at the same time, the opening area of the passage inlet (18a) of the intake passage (18) is increased. It is possible to prevent clogging of the liquid fuel at the passage inlet (18a). For this reason, the detection of the intake pressure by the intake pressure detection sensor (15) is stabilized, there is no problem that the fuel injection amount from the injector (8) fluctuates unnecessarily, and the air-fuel mixture is more evenly distributed to each cylinder (3). High functionality.

<Effect> It is easy to cut the intake pressure introduction passage.
Since the direction of the intake pressure introduction passage (18) is set so that the angle formed by the intake pressure introduction passage (18) with respect to the transverse extension line (19a) illustrated in FIG. There is no problem that the direction of the intake pressure introduction passage (18) is too close to the tangential direction of the inner peripheral surface of the throttle intake passage (6), and the intake pressure introduction passage (18) can be easily machined.

(Invention according to claim 3 )
In addition to the effect of the invention according to claim 2 , the following effect is achieved.
<Effect> It is easy to cut the intake pressure introduction passage.
As illustrated in FIG. 4 (A), the intake pressure introduction passage (18) forms the transverse extension line (19a) on the projection orthogonal to the central axis (6a) of the throttle intake passage (6). Since the direction of the intake pressure introduction passage (18) is set so that the angle (18α) is 45 ° or more, the direction of the intake pressure introduction passage (18) is too close to the axial length direction of the throttle intake passage (6). Thus, there is no problem that the intake pressure introduction passage (18) becomes unnecessarily long, and the intake pressure introduction passage (18) can be easily machined. Further, on the projection orthogonal to the central axis (6a) of the throttle intake passage (6), the angle (18α) formed by the intake pressure introduction passage (18) with respect to the transverse extension line (19a) is 75 ° or less. Thus, since the direction of the intake pressure introduction passage (18) is set, there is no problem that the direction of the intake pressure introduction passage (18) is too close to the tangential direction of the inner peripheral surface of the throttle intake passage (6). The machining of the introduction passage (18) is facilitated.

(Invention of Claim 4 )
In addition to the effect of the invention according to claim 2 or claim 3 , the following effect is achieved.
<Effect> The function of distributing the air-fuel mixture more uniformly to each cylinder is high.
As illustrated in FIG. 5B, a butterfly valve is used for the throttle valve (7), and is parallel to the central axis (6a) of the throttle intake passage (6) and the valve shaft (12) of the throttle valve (7). On the projected view, the passage inlet (18a) of the intake pressure introduction passage (18) is arranged so that the passage inlet (18a) of the intake pressure introduction passage (18) overlaps the central axis (6a) of the throttle intake passage (6). The high-speed intake air that passes by the side of the throttle valve (6) passes by the side of the passage inlet (18a) of the intake pressure introduction passage (18), and the passage inlet (18a) of the intake pressure introduction passage (18). ) Is sucked toward the throttle intake passage (18) by the negative pressure of the intake air, and the liquid fuel is not easily clogged at the passage inlet (18a) of the intake pressure introduction passage (18).
In addition, the intake pressure introduction passage (18) is inclined downward from the passage outlet (18b) toward the passage inlet (18b), and on the above projection view, with respect to the extension axis (6c) of the throttle intake passage (6). The direction of the intake pressure introduction passage (18) was set so that the angle (18β) formed by the intake pressure introduction passage (18) was 45 ° or more and 75 ° or less. For this reason, compared with the case where the angle (18β) is less than 45 °, the liquid fuel that has entered the intake pressure introduction passage (18) tends to flow out by its own weight. Further, compared with the case where the angle (18β) exceeds 75 °, the passage cross-sectional area of the intake introduction passage (18) is increased by the length of the intake pressure introduction passage (18) in the axial direction of the throttle intake passage (6). Compared to the above, the opening area of the passage inlet (18a) of the intake introduction passage (18) can be made larger, the passage cross-sectional area of the intake introduction passage (18) can be reduced, and it is less susceptible to the pulsation of the intake pressure. At the same time, the opening area of the passage inlet (18a) of the intake passage (18) can be increased to prevent clogging of liquid fuel in the passage inlet (18a).
For the above reasons, the detection of the intake pressure by the intake pressure detection sensor (15) is stabilized, the problem that the fuel injection amount from the injector (8) fluctuates unnecessarily is eliminated, and the air-fuel mixture is more evenly distributed to each cylinder (3). The function that can be distributed to is high.

(Invention according to claim 5 )
In addition to the effects of the invention according to any one of claims 1 to 4 , the following effects are provided.
<Effect> The function of distributing the air-fuel mixture more uniformly to each cylinder is high.
As illustrated in FIG. 5A, an attachment hole (20) is formed downward, an intake pressure detection sensor (15) is attached to the attachment hole (20), and a liquid fuel is provided below the attachment hole (20). Since the reservoir (21) is provided and the passage outlet (18b) of the intake pressure introduction passage (18) is opened above the liquid fuel reservoir (21), the liquid fuel that has entered the intake pressure introduction passage (18) In addition to flowing out from the passage inlet (18a) of the intake pressure introduction passage (18) to the throttle intake passage (6), it may flow out from the passage outlet (18b) of the intake pressure introduction passage (18) to the liquid fuel reservoir (21). The clogging of the liquid fuel in the intake pressure introduction passage (18) hardly occurs. Further, since the liquid fuel or dust that has entered the intake pressure introduction passage (18) is collected in the liquid fuel reservoir (21) and does not contact the intake pressure detection sensor (15), the malfunction or sensitivity of the intake pressure detection sensor (15) is reduced. Decrease can be prevented. For this reason, the detection of the intake pressure by the intake pressure detection sensor (15) is stabilized, there is no problem that the fuel injection amount from the injector (8) fluctuates unnecessarily, and the air-fuel mixture is more evenly distributed to each cylinder (3). High functionality.

(Invention of Claim 6 )
In addition to the effects of the invention according to any one of claims 1 to 5 , the following effects are provided.
<Effect> The fuel supply device becomes compact.
As illustrated in FIG. 3A, an injector (8) is arranged after the throttle input arm (22), and a mounting hole (20) of the intake pressure detection sensor (15) is placed beside the throttle input arm (22). Since the boss (20a) is arranged, the rear space and the lateral space of the throttle input arm (22) can be used effectively as the arrangement space for the injector (8) and the boss (20a), respectively, and fuel supply related parts can be used as a throttle. The fuel supply device is made compact by being integrated into the body (5).

(Invention of Claim 7 )
In addition to the effect of the invention according to claim 6 , the following effect is achieved.
<Effect> The number of parts can be reduced.
As illustrated in FIG. 3A, the boss (20a) of the mounting hole (20) of the intake pressure detection sensor (15) is also used as a stopper for swinging the throttle input arm (22). (22) It is not necessary to provide a dedicated swing stopper, and the number of parts can be reduced.

(Invention of Claim 8 )
In addition to the effect of the invention according to claim 6 or 7 , the following effect is produced.
<Effect> The gas fuel supply pipe can be easily arranged.
As illustrated in FIG. 1 (A), a throttle input arm (22) and a gas fuel outlet (11) are arranged separately on the opposite sides of the throttle intake passage (6) in the radial direction. Since the gas fuel supply pipe (23) is connected to (11), the gas fuel supply pipe (23) is connected to the throttle input arm (22), the intake pressure detection sensor (15), and the injector as shown in FIG. The gas fuel supply pipe (23) can be easily piped without interfering with (8).

(Invention according to claim 9 )
In addition to the effect of the invention of any one of claims 1 to 8 , the following effect is achieved.
<Effect> It has a high function of evenly distributing the air-fuel mixture to each cylinder regardless of the operating state.
As exemplified in FIG. 1A, the liquid fuel injected from the liquid fuel injection port (10) collides with the inner peripheral surface of the insulator (14). For this reason, during idling operation at a low intake speed, a part of the liquid fuel stays attached to the inner peripheral surface of the insulator (14) and is reserved in the insulator (14) before entering the intake distribution passage (2). Thus, the air-fuel mixture concentration in the intake air distribution passage (2) is made more uniform. In addition, during high load continuous operation at a high intake speed, part of the liquid fuel that collided with the inner peripheral surface of the insulator (14) flows into the intake distribution passage (2) by pushing in the intake air, and the temperature is increased by high load continuous operation. Is rapidly vaporized on the inner surface of the intake distribution passage (2), and the mixture concentration in the intake distribution passage (2) is made more uniform.
From the above, regardless of the operation state, the air-fuel mixture concentration in the intake air distribution passage (2) is made more uniform, and the function of evenly distributing the air-fuel mixture to each cylinder (3) is high.

(Invention of Claim 10 )
In addition to the effect of the invention of any one of claims 1 to 8 , the following effect is achieved.
<Effect> It has a high function of evenly distributing the air-fuel mixture to each cylinder regardless of the operating state.
Referring to FIG. 1 (A), the liquid fuel injected from the liquid fuel injection port (10) is supplied to the inner peripheral surface of the intake passage outlet (13) of the throttle intake passage (6) and the insulator (14). In the idling operation where the intake speed is slow, a part of the liquid fuel adheres to the inner peripheral surface of the intake passage outlet (13) and the inner peripheral surface of the insulator (14). It is preliminarily vaporized in the intake passage outlet (13) and the insulator (14) before entering the intake distribution passage (2), and the mixture concentration in the intake distribution passage (2) is made more uniform. The Further, during high load continuous operation at a high intake speed, a part of the liquid fuel colliding with the inner peripheral surface of the intake passage outlet (13) and the inner peripheral surface of the insulator (14) is pushed into the intake distribution passage (2 ) And is rapidly vaporized on the inner surface of the intake distribution passage (2) where the temperature is increased due to continuous high-load operation, and the mixture concentration in the intake distribution passage (2) is made more uniform.
From the above, regardless of the operation state, the air-fuel mixture concentration in the intake air distribution passage (2) is made more uniform, and the function of evenly distributing the air-fuel mixture to each cylinder (3) is high.

(Invention of Claim 11 )
In addition to the effects of the invention according to any one of claims 1 to 10 , the following effects are achieved.
<Effect> The function of improving exhaust gas performance during gas operation is high.
As illustrated in FIGS. 1 (A) and 2, the gas fuel outlet (11) is disposed immediately in front of the valve shaft (12) of the throttle valve (7), so that the inner peripheral surface of the throttle intake passage (6). Even if the liquid fuel adhering to the fuel flows back to the upstream side of the throttle intake passage (6) due to the pulsation pressure of the intake air, the liquid fuel is blocked by the valve shaft (12) of the throttle valve (7) and immediately before it. It is difficult for liquid fuel to enter a certain gas fuel outlet (11). Therefore, even when switching from the liquid fuel operation to the gas fuel operation, the problem that the liquid fuel that has entered the gas fuel outlet (11) flows out into the throttle intake passage (6) together with the gas fuel is avoided, and the exhaust gas during the gas operation is avoided. High function to improve performance.

(Invention of Claim 12 )
In addition to the effects of the invention according to any one of claims 1 to 11 , the following effects are provided.
<Effect> The function of more evenly distributing the air-fuel mixture to each cylinder is maintained.
As shown in FIG. 1A, the passage cross-sectional area of the minimum portion of the venturi (44) is set to be larger than the passage cross-sectional area of the minimum portion of the throttle intake passage (6). However, the air intake resistance is not increased, the liquid fuel atomization is not disturbed, and the function of more evenly distributing the air-fuel mixture to each cylinder (3) is maintained. Further, it is possible to prevent a decrease in output due to an increase in intake resistance.

<Effect> The function which can improve the exhaust-gas performance at the time of gas operation is high.
As illustrated in FIG. 1A, since the gas fuel outlet (11) faces the venturi (44), even if liquid fuel enters the gas fuel outlet (11) during the liquid fuel operation, This liquid fuel is sucked out by the negative pressure of the intake air passing through the venturi (44). Therefore, even when switching from the liquid fuel operation to the gas fuel operation, the problem that the liquid fuel that has entered the gas fuel outlet (11) flows out into the throttle intake passage (6) together with the gas fuel is avoided, and the exhaust gas during the gas operation is avoided. High function to improve performance.

(Invention of Claim 13 )
In addition to the effects of the invention according to any one of claims 1 to 12 , the following effects are provided.
<Effect> It has a high function to make the distribution of the air-fuel mixture to each cylinder more uniform regardless of the operating conditions.
As shown in FIGS. 1A and 2, the direction of the injector (8) is such that the extension axis (8b) of the injector (8) passes directly behind the valve shaft (12) of the throttle valve (7). And an angle formed by the injection axis (10a) of the liquid fuel injection port (10) with respect to the extension axis (8b) of the injector (8) is 30 ° or less. Since the direction of 10) is set, the liquid fuel injected from the liquid fuel injection port (10) passes directly behind or near the back of the valve shaft (12) of the throttle valve (7).
For this reason, under conditions where the engine speed and the throttle valve (12) are large and the intake speed increases, the spray of liquid fuel is not directly hit by high-speed intake air, and the disturbance of the spray of liquid fuel can be prevented. The concentration distribution of the air-fuel mixture can be made more uniform.
Further, under the condition that the engine speed and the opening degree of the throttle valve (12) are small and the intake speed is small, the spray of liquid fuel is generated behind the valve shaft (12) of the throttle valve (7). Entrained in (turbulent flow), the vaporization of the liquid fuel is promoted, and the concentration distribution of the air-fuel mixture in the intake air distribution passage (2) can be made more uniform.
Thus, regardless of the operating conditions, the concentration distribution of the air-fuel mixture in the intake air distribution passage (2) can be made more uniform, and the air-fuel mixture can be more evenly distributed to each cylinder (3). Is expensive.

<Effect> The function of improving exhaust gas performance during gas operation is high.
As illustrated in FIG. 2, the liquid fuel injected from the liquid fuel injection port (10) of the injector (8) is directly behind or near the back of the valve shaft (12) of the throttle valve (7). ) Collides with the inner peripheral surface. For this reason, even if the liquid fuel adhering to the inner peripheral surface or the like of the throttle intake passage (6) flows backward to the upstream side of the throttle intake passage (6) due to the pulsation of the intake air, the liquid fuel is directly in front of the throttle valve. It is blocked by the valve shaft (12) of (7) and hardly enters the gas fuel outlet (11). Therefore, even when switching from the liquid fuel operation to the gas fuel operation, the problem that the liquid fuel that has entered the gas fuel outlet (11) flows out into the throttle intake passage (6) together with the gas fuel is avoided, and the exhaust gas during the gas operation is avoided. High performance can be maintained.

(Invention according to Claim 14 )
In addition to the effect of the invention according to claim 13 , the following effect is achieved.
<Effect> It has a high function to make the distribution of the air-fuel mixture to each cylinder more uniform.
As illustrated in FIG. 1B, since a plurality of liquid fuel injection ports (10) are provided, the opening area of the liquid fuel injection port (10) is reduced, and the liquid fuel injected from the liquid fuel injection port (10) is reduced. Oil droplets can be refined. Also, the angle formed by the injection axis (10a) of each liquid fuel injection port (10) with respect to the extension axis (8b) of the injector (8) is set to 5 ° or more, so that each liquid fuel injection port The overlapping of the sprays of the liquid fuel injected from (10) is suppressed, and it is possible to suppress the oil droplets of the liquid fuel from becoming large due to the combination. For these reasons, the vaporization of the liquid fuel is promoted, the concentration distribution of the air-fuel mixture in the intake air distribution passage (2) can be made more uniform, and the distribution of the liquid air-fuel mixture to each cylinder (3) can be further improved. Highly uniform function.

<Effect> Even when the throttle opening is small, the function of evenly distributing the air-fuel mixture to each cylinder is high.
Since the liquid droplets of the liquid fuel can be miniaturized and the increase of the droplets of the liquid fuel due to the coupling can be suppressed, the fine oil droplets of the liquid fuel injected from the liquid fuel injection port (10) Is trapped in the wake formed behind the valve shaft (12) of the throttle valve (7), and even when the throttle opening is small, the vaporization of the liquid fuel is promoted and mixing in the intake distribution passage (2) is performed. The air concentration distribution can be made more uniform, and the function of making the distribution of the air-fuel mixture to each cylinder (3) more uniform is high.

  Embodiments of the present invention will be described with reference to the drawings. 1 to 7 are diagrams for explaining a multi-cylinder dual fuel engine according to an embodiment of the present invention. In this embodiment, a vertical water-cooled in-line three-cylinder dual fuel engine will be described.

The outline of the embodiment of the present invention is as follows.
As shown in FIG. 7, in this engine, the cylinder head (1) is assembled to the upper part of the cylinder block (24), the head cover (25) is assembled to the upper part of the cylinder head (1), and the lower part of the cylinder block (25) is assembled. An oil pan (26) is assembled, a gear case (27) is assembled at the front of the cylinder block (24), and a flywheel (28) is arranged at the rear of the cylinder block (24). An engine cooling fan (29) is disposed at the front of the gear case (27).

  As shown in FIG. 6, the intake air distribution passage (2) is attached to the cylinder head (1), and the air-fuel mixture is distributed to the plurality of cylinders (3) through the intake air distribution passage (2). A throttle body (5) is attached to the single distribution passage inlet (4), and liquid fuel and gas fuel are switched and supplied to the throttle body (5).

  Although the intake distribution passage (2) is generally called an intake manifold, it is particularly called the intake distribution passage (2) because it has a box shape without branch pipes. As shown in FIG. 6, the number of cylinders (3) is three, and these are called the first cylinder, the second cylinder, and the third cylinder from the engine cooling fan (29) side. The single distribution passage inlet (4) is arranged at the end of the intake distribution passage (2) on the third cylinder side, and is viewed in a direction parallel to the cylinder center axis (30) as shown in FIG. With the flywheel (28) side as the rear, it is directed obliquely at an angle of 60 ° with respect to the crankshaft central axis (31). The liquid fuel supplied to the throttle body (5) is gasoline, and the gas fuel is LPG (liquefied petroleum gas). As shown in FIG. 1A, the fuel changeover switch (32) is linked to the injector (8) and the gas valve actuator (23) via the control means (17), and the fuel changeover switch (32) is changed over. Then, liquid fuel and gas fuel are switched and supplied to the throttle body (5). The control means (17) is a microcomputer.

The structure of the fuel supply device is as follows.
As shown in FIG. 1A, a throttle intake passage (6) is provided in the throttle body (5), a throttle valve (7) is disposed in the throttle intake passage (6), and the throttle body (5 1), an injector (8) is attached, and the tip (9) of this injector (8) is placed in the throttle intake passage (6) downstream of the throttle valve (7), as shown in FIG. 1 (B). Thus, a liquid fuel injection port (10) is opened at the tip (9) of the injector (8), and the intake air in the throttle intake passage (6) of the throttle body (5) as shown in FIG. 1 (A). An intake pipe connection pipe (34) is attached to the passage inlet (6b), and an intake pipe (35) derived from an air cleaner (not shown) is connected to the intake pipe connection pipe (34), and the intake pipe connection pipe (34) Is provided with a gas fuel outlet (11), which is connected to the throttle valve (11). ) It is made to face to the intake pipe connection pipe (34) in which also the upstream. A venturi (44) is provided in the intake pipe connection pipe (34), the gas fuel outlet (11) is faced in the venturi (44), and the passage cross-sectional area of the minimum portion of the venturi (44) It is set to the same size as the cross-sectional area of the minimum portion of the throttle intake passage (6). The passage cross-sectional area of the minimum portion of the venturi (44) may be set to a size exceeding the passage cross-sectional area of the minimum portion of the throttle intake passage (6). Specifically, the inner diameter (44D) of the minimum portion of the venturi (44) having a circular cross section may be larger than the inner diameter (6D) of the minimum portion of the throttle intake passage (6) having a circular cross section. In addition, as shown in FIG. 7, the throttle valve (7) is interlockingly connected to the speed control lever (43) via the mechanical governor (42).

The relationship between the throttle valve and the injector is as follows.
As shown in FIG. 1 (A) and FIG. 2, the direction of the central axis (6a) of the throttle intake passage (6) is the front-rear direction, and the downstream side of the valve shaft (12) of the throttle valve (7) is rearward. As described above, a butterfly valve is used for the throttle valve (7), and the tip (9) of the injector (8) is disposed immediately behind the valve shaft (12) of the throttle valve (7). Assuming an extension axis (8b) of the injector (8) extending from the central axis (8a) through the tip (9) of the injector (8) into the throttle intake passage (6), this injector (8) is extended. The direction of the injector (8) is set so that the axis (8b) passes directly behind the valve shaft (12) of the throttle valve (7). As shown in FIG. 2, the rear side of the valve shaft (12) is along the central axis (6 a) of the throttle intake passage (6) from the valve shaft (12) when viewed in a direction parallel to the valve shaft (12). The position moved backward.

The configuration of the liquid fuel injection port is as follows.
As shown in FIG. 1 (B), four liquid fuel injection ports (10) are provided, and as shown in FIG. 1 (A) and FIG. 2, a throttle intake passage (6) is connected to each liquid fuel injection port (10). ) Assuming the injection axis (10a) of the liquid fuel injection port (10) extending inward, the injection axis (10a) of the liquid fuel injection port (10) with respect to the extension axis (8b) of the injector (8). The direction of the liquid fuel injection port (10) is set so that the angle formed by The liquid fuel injected from the liquid fuel injection port (10) passes directly behind or near the back of the valve shaft (12) of the throttle valve (7), making it less susceptible to direct high-speed intake, and spraying liquid fuel. From the viewpoint of preventing disturbance, the angle is desirably 30 ° or less, more desirably 25 ° or less, and most desirably 20 ° or less. Further, from the viewpoint of suppressing the overlapping of the sprays of the liquid fuel injected from the liquid fuel injection ports (10) and suppressing the oil droplets of the liquid fuel from becoming larger due to the coupling, the angle is desirably 5 ° or more. 7 ° or more is more desirable, and 10 ° or more is most desirable. Therefore, from both viewpoints, the angle is preferably 5 ° or more and 30 ° or less, more preferably 7 ° or more and 25 ° or less, and most preferably 10 ° or more and 20 ° or less. There may be a single liquid fuel injection port (10). In this case, the extension axis (8b) of the injector (8) may coincide with the injection axis (10a) of the liquid fuel injection port (10).

The structure related to the injection direction of the injector is as follows.
As shown in FIG. 1 (A), a cylindrical insulator (14) is provided between a distribution passage inlet (4) of the intake distribution passage (2) and an intake passage outlet (13) of the throttle intake passage (6). Is interposed. The injector (8) is inclined so that the tip (9) of the injector (8) having the liquid fuel injection port (10) faces the downstream side of the throttle intake passage (6), and the injector (8) With the extension axis (8b) directed toward the inner peripheral surface of the insulator (14), the liquid fuel injected from the liquid fuel injection port (10) becomes the inner periphery of the intake passage outlet (13) of the throttle intake passage (6). Colliding with the surface and the inner peripheral surface of the insulator (14).
Instead of this structure, the extension axis (8b) of the injector (8) is directed from the liquid fuel injection port (10) toward the inner peripheral surface of the intake passage outlet (13) of the throttle intake passage (6). The liquid fuel may collide with the inner peripheral surface of the intake passage outlet (13) of the throttle intake passage (6) and the inner peripheral surface of the insulator (14).

The control structure for liquid fuel injection and the like is as follows.
As shown in FIG. 1A, the control means (17) includes an intake pressure detection sensor (15) for detecting the intake pressure of the throttle intake passage (6) and an engine speed sensor (16) for detecting the engine speed. 6), the control means (17) controls the liquid fuel injection amount and liquid fuel injection timing from the injector (8) based on the intake pressure and the engine speed based on the intake pressure and the engine speed. The ignition timing of the spark plug (36) shown in FIG. The intake pressure detection sensor (15) has a function of detecting the intake air temperature, and the control means (17) corrects the liquid fuel injection amount based on the intake air temperature.

The structure related to the intake pressure detection sensor is as follows.
As shown in FIG. 1 (A), the intake pressure detection sensor (15) is attached to the throttle body (5) together with the injector (8). An intake pressure introduction passage (18) for introducing the intake pressure in the throttle intake passage (6) to the intake pressure detection sensor (15) is provided in the peripheral wall of the throttle intake passage (6) of the throttle body (5). Yes. The throttle inlet passage (6a) has a passage inlet (18a) of the intake pressure introduction passage (18) upstream of the injector (8) and downstream of the valve shaft (12) of the throttle valve (7). ).

The setting of the direction of the intake pressure introduction passage is as follows.
As shown in FIG. 4 (A), a transverse line (19) crossing the throttle intake passage (6) having a circular cross section in the radial direction and toward the passage inlet (18a) of the intake pressure introduction passage (18); Assuming a transverse extension line (19a) extending from the transverse line (19) to the outside of the throttle intake passage (6) through the passage inlet (18a) of the intake pressure introduction passage (18), this transverse extension line The direction of the intake pressure introduction passage (18) to be drilled is set so that the angle formed by the intake pressure introduction passage (18) is 60 ° with respect to (19a). Even if the direction of the intake pressure introduction passage (18) is closer to the tangential direction than the radial direction of the throttle intake passage (6) and the passage cross-sectional area of the intake introduction passage (18) is reduced, the intake pressure introduction passage (18) From the viewpoint of making it possible to increase the opening area of the passage inlet (18a), the angle is preferably 45 ° or more, more preferably 50 ° or more, and 55 ° or more. Is more desirable. Further, there is no problem that the direction of the intake pressure introduction passage (18) is too close to the tangential direction of the inner peripheral surface of the throttle intake passage (6), and from the viewpoint of facilitating the machining of the intake pressure introduction passage (18), The angle is desirably 75 ° or less, more desirably 70 ° or less, and most desirably 65 ° or less. Therefore, from both viewpoints, the angle is preferably 45 ° or more and 75 ° or less, more preferably 50 ° or more and 70 ° or less, and 55 ° or more and 65 ° or less. Most desirable.

  As shown in FIG. 4 (A), the intake pressure introduction passage (18) with respect to the transverse extension line (19a) on a projection orthogonal to the central axis (6a) of the throttle intake passage (6). The direction of the intake pressure introduction passage (18) is set so that the angle (18α) formed by The direction of the intake pressure introduction passage (18) is too close to the axial direction of the throttle intake passage (6) and the intake pressure introduction passage (18) becomes unnecessarily long. From the viewpoint of facilitating processing, the angle (18α) is desirably 45 ° or more, more desirably 50 ° or more, and most desirably 55 ° or more. Further, there is no problem that the direction of the intake pressure introduction passage (18) is too close to the tangential direction of the inner peripheral surface of the throttle intake passage (6), and from the viewpoint of facilitating the machining of the intake pressure introduction passage (18), The angle (18α) is desirably 75 ° or less, more desirably 70 ° or less, and most desirably 65 ° or less. Therefore, from both viewpoints, the angle (18α) is preferably 45 ° or more and 75 ° or less, more preferably 50 ° or more and 70 ° or less, and 55 ° or more and 65 ° or less. It is most desirable to do.

As shown in FIG. 5 (B), a butterfly valve is used for the throttle valve (7), and a central axis (6a) of the throttle intake passage (6) and a valve shaft (12) of the throttle valve (7) are provided. A passage of the intake pressure introduction passage (18) so that the passage inlet (18a) of the intake pressure introduction passage (18) overlaps the central axis (6a) of the throttle intake passage (6) on a parallel projection. An inlet (18a) is arranged.
The intake pressure introduction passage (18) is inclined downward from the passage outlet (18b) toward the passage inlet (18b), and from the central axis (6a) of the throttle intake passage (6) to the throttle intake passage (6). Assuming an extension axis (6c) extending outside the throttle intake passage (6) through the passage inlet (6b), as shown in FIG. 5 (B), the central axis (6a) of the throttle intake passage (6) is shown. And an angle formed by the intake pressure introduction passage (18) with respect to the extension axis (6c) of the throttle intake passage (6) on a projection parallel to the valve shaft (12) of the throttle valve (7) The direction of the intake pressure introduction passage (18) is set so that (18β) is 60 °.

  From the viewpoint of facilitating the flow of liquid fuel that has entered the intake pressure introduction passage (18) by its own weight, the angle (18β) is preferably 45 ° or more, more preferably 50 ° or more, and 55 °. The above is most desirable. The intake pressure introduction passage (18) is elongated in the axial direction of the throttle intake passage (6), and the opening of the passage inlet (18a) of the intake introduction passage (18) is larger than the passage cross-sectional area of the intake introduction passage (18). From the viewpoint of increasing the area, the angle (18β) is desirably 75 ° or less, more desirably 70 ° or less, and most desirably 65 ° or less. From both viewpoints, the angle (18β) is preferably 45 ° or more and 75 ° or less, more preferably 50 ° or more and 70 ° or less, and 55 ° or more and 65 ° or less. Is most desirable.

The configuration of the mounting hole of the intake pressure detection sensor is as follows.
As shown in FIG. 5 (A), a mounting hole (20) for the intake pressure detection sensor (15) is formed in the throttle body (5), and the intake pressure introduction passage (18) is formed in the mounting hole (20). Communicate. The attachment hole (20) is formed downward, an intake pressure detection sensor (15) is attached to the attachment hole (20), and a liquid fuel reservoir (21) is provided below the attachment hole (20). A passage outlet (18b) of the intake pressure introduction passage (18) is opened at an upper portion of the reservoir (21).

The arrangement of parts to be attached to the throttle body is as follows.
As shown in FIG. 3A, the direction of the central axis (6a) of the throttle intake passage (6) is the front-rear direction, and the downstream side of the valve shaft (12) of the throttle valve (7) is the rear. The injector (8) is disposed after the throttle input arm (22) with the direction orthogonal to the front-rear direction as the horizontal direction when viewed in a direction parallel to the valve shaft (12) of the valve (7), and the throttle A boss (20a) of the mounting hole (20) of the intake pressure detection sensor (15) is disposed beside the input arm (22). The boss (20a) of the mounting hole (20) of the intake pressure detection sensor (15) is also used as a stopper for swinging the throttle input arm (22).

The configuration of the gas fuel supply apparatus is as follows.
As shown in FIG. 1A, the throttle input arm (22) and the gas fuel outlet (11) are distributed between the upper part of the throttle intake passage (6) and the lower part of the intake pipe connection pipe (34). The gas fuel supply pipe (23) is connected to the gas fuel outlet (11). As shown in FIG. 4 (B), a valve chamber (37) is provided in the lower portion of the throttle body (5), and the gas flows from the valve chamber (37) toward the intake passage inlet (6b) of the throttle intake passage (6). A fuel outlet (11) is led out. The valve chamber (37) accommodates a valve seat (38) and a needle valve (39) seated on the valve seat (38). The needle valve (39) is an output shaft (40) of the gas valve actuator (33). The gas fuel supply pipe (23) is communicated with the valve port (41) of the valve seat (38).

The arrangement of the gas fuel outlet is as follows.
As shown in FIG. 1 (A) and FIG. 2, the direction of the central axis (6a) of the throttle intake passage (6) is the front-rear direction, and the upstream side of the valve shaft (12) of the throttle valve (7) is the front side. The throttle valve (7) uses a butterfly valve, and the gas fuel outlet (11) is arranged in front of the valve shaft (12) of the throttle valve (7). As shown in FIG. 2, the front of the valve shaft (12) is seen from a direction parallel to the valve shaft (12) to the central axis (6a) of the throttle intake passage (6) from the valve shaft (12). The position moved forward along.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining a throttle body and its peripheral parts of a multi-cylinder dual fuel engine according to an embodiment of the present invention, FIG. 1 (A) is a longitudinal side view, and FIG. 1 (B) is a central axis of the injector. FIG. It is the II-II sectional view taken on the line of FIG. FIG. 3A is a plan view and FIG. 3B is a side view illustrating the throttle body of FIG. 1. 4A and 4B are views for explaining the throttle body and the intake pipe connecting pipe in FIG. 1, in which FIG. 4A is a view taken in the direction of arrow IV in FIG. 3B, and FIG. . FIG. 5A is a cross-sectional view taken along line VV in FIG. 3A, and FIG. 5B is a longitudinal side view of the throttle body. 1 is a plan view of a multi-cylinder dual fuel engine according to an embodiment of the present invention. It is a side view of the engine of FIG.

(1) Cylinder head
(2) Intake distribution passage
(3) Cylinder
(4) Distribution passage entrance
(5) Throttle body
(6) Throttle intake passage
(6D) Inner diameter of the smallest part
(6a) Center axis
(6b) Inlet passage entrance
(6c) Extension axis
(7) Throttle valve
(8) Injector
(8a) Center axis
(8b) Extension axis
(9) Tip
(10) Liquid fuel injection port
(10a) Injection axis
(11) Gas fuel outlet
(12) Valve stem
(13) Inlet passage exit
(14) Insulator
(15) Intake pressure detection sensor
(16) Engine speed sensor
(17) Control means
(18) Intake pressure introduction passage
(18a) Passage entrance
(18b) Passage exit
(18α) Angle
(18β) Angle
(19) Crossing line
(19a) Transverse extension line
(20) Mounting hole
(20a) Boss
(21) Liquid fuel reservoir
(22) Throttle input arm
(23) Gas fuel supply pipe
(34) Intake pipe connection pipe
(44) Venturi
(44D) Inner diameter of the smallest part

Claims (14)

An intake distribution passage (2) is attached to the cylinder head (1), and an air-fuel mixture is distributed to a plurality of cylinders (3) through the intake distribution passage (2). A single distribution passage inlet of the intake distribution passage (2) In a multi-cylinder dual fuel engine in which a throttle body (5) is attached to (4) and liquid fuel and gas fuel are switched and supplied to the throttle body (5).
A throttle intake passage (6) is provided in the throttle body (5), a throttle valve (7) is arranged in the throttle intake passage (6), and an injector (8) is attached to the throttle body (5). The tip (9) of the injector (8) faces the throttle intake passage (6) downstream of the throttle valve (7), and a liquid fuel injection port (9) is inserted into the tip (9) of the injector (8). 10)
An intake pipe connection pipe (34) is attached to an intake passage inlet (6b) of the throttle intake passage (6) of the throttle body (5), and an intake pipe (35) led out from an air cleaner is attached to the intake pipe connection pipe (34). A gas fuel outlet (11) is provided in the intake pipe connection pipe (34), and the gas fuel outlet (11) is provided in the intake pipe connection pipe (34) upstream of the throttle valve (7). Let it come,
An intake pressure detection sensor (15) for detecting the intake pressure of the throttle intake passage (6) and an engine speed sensor (16) for detecting the engine speed are connected to the injector (8) via a control means (17). In cooperation, the control means (17) controls the liquid fuel injection amount from the injector (8) based on the intake pressure and the engine speed,
The intake pressure detection sensor (15) is attached to the throttle body (5) together with the injector (8),
An intake pressure introduction passage (18) for introducing the intake pressure in the throttle intake passage (6) to the intake pressure detection sensor (15) is provided in the peripheral wall of the throttle intake passage (6) of the throttle body (5),
A multi-cylinder dual, characterized in that a passage inlet (18a) of the intake pressure introduction passage (18) is opened on the inner peripheral surface of the throttle intake passage (6) upstream of the injector (8). Fuel engine. The multi-cylinder dual fuel engine according to claim 1 ,
The throttle intake passage (6) having a circular cross section crosses the throttle intake passage (6) in the radial direction and extends to the passage inlet (18a) of the intake pressure introduction passage (18), and the suction line from the transverse line (19). Assuming a transverse extension line (19a) extending outside the throttle intake passage (6) through the passage inlet (18a) of the pressure introduction passage (18), the intake pressure is increased with respect to the transverse extension line (19a). A multi-cylinder dual fuel engine characterized in that the direction of the intake pressure introduction passage (18) to be drilled is set so that the angle formed by the introduction passage (18) is 45 ° or more and 75 ° or less. The multi-cylinder dual fuel engine according to claim 2 ,
An angle (18α) formed by the intake pressure introduction passage (18) with respect to the transverse extension line (19a) is 45 ° or more on the projection orthogonal to the central axis (6a) of the throttle intake passage (6). The multi-cylinder dual fuel engine is characterized in that the direction of the intake pressure introduction passage (18) is set so as to be 75 ° or less. The multi-cylinder dual fuel engine according to claim 2 or 3 ,
A butterfly valve is used as the throttle valve (7), and the intake pressure is shown on a projection parallel to the central axis (6a) of the throttle intake passage (6) and the valve shaft (12) of the throttle valve (7). The passage inlet (18a) of the intake pressure introduction passage (18) is arranged so that the passage inlet (18a) of the introduction passage (18) overlaps the central axis (6a) of the throttle intake passage (6).
The intake pressure introduction passage (18) is inclined downward from the passage outlet (18b) toward the passage inlet (18b), and from the central axis (6a) of the throttle intake passage (6) to the throttle intake passage (6). Assuming an extension axis (6c) extending outside the throttle intake passage (6) through the passage inlet (6b), the central axis (6a) of the throttle intake passage (6) and the valve shaft of the throttle valve (7) On the projection parallel to (12), the angle (18β) formed by the intake pressure introduction passage (18) with respect to the extension axis (6c) of the throttle intake passage (6) is 45 ° or more and 75 °. A multi-cylinder dual fuel engine characterized in that the direction of the intake pressure introduction passage (18) is set as follows. The multi-cylinder dual fuel engine according to any one of claims 1 to 4 ,
A mounting hole (20) for the intake pressure detection sensor (15) is formed in the throttle body (5), and the intake pressure introduction passage (18) is communicated with the mounting hole (20).
The attachment hole (20) is formed downward, the intake pressure detection sensor (15) is attached to the attachment hole (20), and a liquid fuel reservoir (21) is provided below the attachment hole (20). A multi-cylinder dual fuel engine characterized in that a passage outlet (18b) of the intake pressure introduction passage (18) is opened at an upper portion of a fuel reservoir (21). The multi-cylinder dual fuel engine according to any one of claims 1 to 5 ,
The direction of the central axis (6a) of the throttle intake passage (6) is the front-rear direction, and the downstream side of the valve shaft (12) of the throttle valve (7) is the rear.
Looking in a direction parallel to the valve shaft (12) of the throttle valve (7), the direction perpendicular to the front-rear direction is defined as the left-right lateral direction.
The injector (8) is disposed after the throttle input arm (22), and the boss (20a) of the mounting hole (20) of the intake pressure detection sensor (15) is disposed beside the throttle input arm (22). Multi-cylinder dual fuel engine, characterized by that. The multi-cylinder dual fuel engine according to claim 6 ,
A multi-cylinder dual fuel engine characterized in that a boss (20a) of a mounting hole (20) of the intake pressure detection sensor (15) is also used as a stopper for swinging of the throttle input arm (22). The multi-cylinder dual fuel engine according to claim 6 or 7 ,
The throttle input arm (22) and the gas fuel outlet (11) are separately arranged at the upper part of the throttle intake passage (6) and the lower part of the intake pipe connecting pipe (34), and the gas fuel outlet (11). A multi-cylinder dual fuel engine having a gas fuel supply pipe (23) connected thereto. The multi-cylinder dual fuel engine according to any one of claims 1 to 8 ,
A cylindrical insulator (14) is interposed between the distribution passage inlet (4) of the intake distribution passage (2) and the intake passage outlet (13) of the throttle intake passage (6);
The injector (8) is inclined so that the tip (9) of the injector (8) having the liquid fuel injection port (10) faces the downstream side of the throttle intake passage (6), and the injector (8) The extension axis (8b) is directed toward the inner peripheral surface of the insulator (14) so that the liquid fuel injected from the liquid fuel injection port (10) collides with the inner peripheral surface of the insulator (14). Multi-cylinder dual fuel engine characterized by The multi-cylinder dual fuel engine according to any one of claims 1 to 8 ,
A cylindrical insulator (14) is interposed between the distribution passage inlet (4) of the intake distribution passage (2) and the intake passage outlet (13) of the throttle intake passage (6);
The injector (8) is tilted so that the tip (9) of the injector (8) faces the downstream side of the throttle intake passage (6), and the extension axis (8b) of the injector (8) is used as the throttle intake passage. The liquid fuel injected from the liquid fuel injection port (10) toward the inner peripheral surface of the intake passage outlet (13) of (6) is the inner peripheral surface of the intake passage outlet (13) of the throttle intake passage (6). And a multi-cylinder dual fuel engine characterized by colliding with the inner peripheral surface of the insulator (14). The multi-cylinder dual fuel engine according to any one of claims 1 to 10 ,
The direction of the central axis (6a) of the throttle intake passage (6) is the front-rear direction, and the upstream side of the valve shaft (12) of the throttle valve (7) is the front.
A multi-cylinder dual fuel engine characterized in that a butterfly valve is used for the throttle valve (7), and the gas fuel outlet (11) is arranged in front of the valve shaft (12) of the throttle valve (7). The multi-cylinder engine according to any one of claims 1 to 11 ,
A venturi (44) is provided in the intake pipe connection pipe (34), the gas fuel outlet (11) is faced in the venturi (44), and the passage cross-sectional area of the minimum portion of the venturi (44) A multi-cylinder dual fuel engine characterized in that it is set to have a size equal to or larger than the cross-sectional area of the minimum portion of the throttle intake passage (6). The multi-cylinder dual fuel engine according to any one of claims 1 to 12 ,
The direction of the central axis (6a) of the throttle intake passage (6) is the front-rear direction and the downstream side of the valve shaft (12) of the throttle valve (7) is the rear.
A butterfly valve is used for the throttle valve (7), and the tip (9) of the injector (8) is disposed immediately behind the valve shaft (12) of the throttle valve (7). The central axis of the injector (8) Assuming an extension axis (8b) of the injector (8) extending from the (8a) through the tip (9) of the injector (8) into the throttle intake passage (6), the extension axis of the injector (8) ( The direction of the injector (8) is set so that 8b) passes directly behind the valve shaft (12) of the throttle valve (7),
Assuming an injection axis (10a) of the liquid fuel injection port (10) extending from the liquid fuel injection port (10) into the throttle intake passage (6), with respect to the extension axis (8b) of the injector (8), A multi-cylinder dual fuel engine characterized in that the orientation of the liquid fuel injection port (10) is set so that the angle formed by the injection axis (10a) of the liquid fuel injection port (10) is 30 ° or less. . The multi-cylinder dual fuel engine of claim 13 ,
A plurality of the liquid fuel injection ports (10) are provided, and the angle formed by the injection axis (10a) of each liquid fuel injection port (10a) with respect to the extension axis (8b) of the injector (8) is 5 ° or more, respectively. A multi-cylinder dual fuel engine, characterized in that the orientation of the liquid fuel injection port (10) is set.

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