JPH10325366A - Mounting method of injection valve for natural gas engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve cleanliness of exhaust gas and fuel consumption performance by making gaseous fuel collide against intake air flow, and evenly mixing air with the gas fuel. SOLUTION: In this mounting method for an injection valve of a natural gas engine, an injection valve 6 is arranged on a side wall of an intake pipe 27 in a downstream of a throttle valve 25. An injection port of the injection valve 6 is directed opposedly to intake air for injecting natural gas fuel only in the intake stroke. The injection valve 6 is arranged on the outer side of a bent portion of the intake pipe 27, and also in the downstream thereof. The natural gas fuel is injected to an area where velocity of the outer intake air is relatively higher compared to the center axis of the bent portion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mounting a fuel injection valve used in a natural gas engine.

[0002]

2. Description of the Related Art Compressed natural gas (CNG) has been increasingly used as fuel for automobiles for energy and environmental measures. Even in natural gas engines, purifying exhaust gas, improving fuel consumption rate, improving output performance,
A fuel injection system has been adopted to improve startability and the like.

FIGS. 8 and 9 show a conventional example equipped with a natural gas engine injection valve. A CNG cylinder 1 is connected to a delivery pipe 5 through a gas pipe 2, and a shutoff valve 3 and a regulator 4 are connected to the gas pipe 2. It is arranged. The CNG cylinder 1 is filled with a high-pressure natural gas (for example, a maximum filling pressure of 211 kg / cm ² (gauge pressure)), and the natural gas is depressurized by the regulator 4 (for example, 2.5 kg / c).
m to ^2). The decompressed natural gas passes through a delivery pipe 5 and is sent to an injection valve 6 arranged for each cylinder. Since the natural gas flow rate changes depending on the gas pressure and the gas temperature, it is necessary to correct the fuel injection time according to the gas pressure and the gas temperature. Therefore, the delivery pipe 5 is provided with a fuel pressure sensor 10 and a fuel temperature sensor 11.

A combustion chamber 19 is provided above the piston 18 of the engine body 17, and an intake valve is provided between the combustion chamber 19 and an intake port 20.
21 is provided, and an exhaust valve is provided between the combustion chamber 19 and the exhaust port 22.
23 are arranged. On the upstream side of the suction port 20, a throttle body 26 having a throttle valve 25 is provided with an intake pipe 27.
, And an air cleaner 28 is provided upstream of the throttle valve 25. The injection valve 6 has an intake pipe 27
Is attached to the side wall of the downstream end of the airbag with the front end directed toward the suction port 20. The intake pipe 27 has an intake pressure sensor 12
The water temperature sensor 14 is provided in the engine body 17, and the outputs of the intake pressure sensor 12 and the water temperature sensor 14 are input to an ECU (electronic control unit) 16 through wiring. Outputs of the fuel pressure sensor 10, the fuel temperature sensor 11, the crank angle sensor 13, and the throttle sensor 15 are also input to the ECU 16 through wiring. Reference numeral 7 denotes a spark plug.

As shown in FIG. 9, an injection valve 6 is arranged on the upper side wall of the downstream end of the intake pipe 27, and the natural gas fuel crosses the flow of the intake air obliquely downstream from above. Injected to. The main component of natural gas is methane, which is smaller than the specific gravity of air (0.6 to 0.7 times)
Therefore, the injected natural gas tends to gather above the intake port 20 and the intake air tends to gather below, making it difficult to uniformly mix the natural gas and air.

In an engine using natural gas fuel, a fuel injection port is formed in an intake port downstream of a throttle valve in an intake pipe of each cylinder of the engine in a direction opposite to a main flow of intake air, and only in an intake stroke of the cylinder. It is known to dispose a fuel injection valve that injects fuel from an injection port (see Japanese Utility Model Laid-Open No. 6-80825).
According to this intake system, a drift occurs due to gas fuel injected against the intake air flow, and as a result,
Tumble is generated in the combustion chamber.

[0007]

In the conventional intake system, the intake air flow is controlled by the injection pressure of gaseous fuel to produce a tumble flow. Therefore, the effect cannot be exerted in a low air amount range, and combustion may be deteriorated. There is. The present invention provides a method for mounting an injection valve for a natural gas engine, in which gas fuel collides with an intake air flow to uniformly mix air and gas fuel, thereby purifying exhaust gas and improving fuel consumption rate. As an issue.

[0008]

According to the present invention, an injection valve is provided on a side wall of an intake pipe (27, 27a, 27b) downstream of a throttle valve (25).
(6) is disposed, the injection port of the injection valve (6) is directed in a direction facing the intake air, and a natural gas engine injection valve is mounted such that natural gas fuel is injected only in an intake stroke. In the region, the injection valve (6) is arranged outside and downstream of the curved portion of the intake pipe (27, 27a, 27b), and the speed of the intake air outside the central axis (XX) of the curved portion is relatively high. The first configuration is that natural gas fuel is injected toward. In the first configuration, the natural gas fuel is directed toward a secondary flow flowing from the inside to the outside of the intake pipe (27, 27a, 27b) in a cross section perpendicular to the central axis (XX) of the bent portion in the first configuration. The configuration configured to be injected is referred to as a second configuration. According to the present invention, in the first or second configuration, the arrival time of the intake air to the bent portion is predicted based on the intake air amount and the intake valve opening timing, and the natural gas fuel is set by setting the injection timing in consideration of the fuel pressure. Injected
The third configuration is such that the intake air and the injected gas fuel collide in the bent portion. In the present invention, the bent portion of the intake pipe is interpreted to include a region downstream of the bent portion and in which the flow in the pipe axial direction is relatively fast and a region where the secondary flow exists.

[0009]

1 to 5 show a first embodiment of a method for mounting an injection valve for a natural gas engine according to the present invention.
In the description of the configuration in FIGS. 1 to 4, the same members as those in the conventional example shown in FIGS. 8 and 9 are denoted by the same reference numerals as in FIGS. 8 and 9, and the description of the configuration is omitted. First, the mounting position of the injection valve will be described. As clearly shown in FIGS. 2 and 3, in the first embodiment, a 90 ° bend bending pipe which is bent from the vertical direction to the horizontal direction is used as the intake pipe 27, and is bent from the vertical direction to the horizontal direction. The injection valve 6 is arranged on the lower wall (outer wall downstream of the curved pipe) of the finished portion. With the tip of the injection valve 6 directed upstream (in the direction opposite to the intake air), the center line of the injection valve 6 (the center line of the injection) passes outside the center axis XX in the tube axis direction of the curved pipe, and The injection valve 6 is arranged so that the center line thereof is parallel to the tangent line TT of the bent portion. Further, the injection valve 6 is disposed so that the center line thereof intersects the center axis XX in the vertical direction of the bent pipe. Here, a position where the tangent line TT of the bent portion is 45 ° with respect to the vertical center axis XX is selected.

The flow of the intake air will be described. Intake pipe
Due to the effect of viscosity and centrifugal force, the intake air flow in the 27 bent pipes has a maximum flow velocity distribution near the outer wall in the axial direction of the pipe (see Fig. 3 (a)), and the cross section perpendicular to the center axis of the bent section (tangent (Section perpendicular to TT) At AA, the intake pipe 27
A secondary flow (see FIG. 3 (b)) flowing from the inside to the outside occurs. It is said that the secondary flow is caused by an outward centrifugal force acting on the flow in the pipe axial direction at the bent portion of the bent pipe. As described above, in a region where the speed of the intake air outside the central axis of the bent portion is relatively high, in a section perpendicular to the central axis of the bent portion, toward the secondary flow flowing from the inside to the outside of the intake pipe. , Natural gas fuel is injected.

The mixing of the injected gas fuel and the intake air flow will be described. Natural gas fuel is injected from the injection valve 6 during the intake stroke so that the collision between the intake air flow and the injected gas fuel occurs outside the central axis of the bent portion of the intake pipe 27. As shown in FIG. 2, the injected gas fuel collides with the intake air flow having a relatively high flow velocity in the entire range from the low air amount to the high air amount. As described above, natural gas has a lower specific gravity than air, so it rides on the secondary flow while being pushed by the intake air flow, diffuses into the intake pipe, and is uniform in the intake pipe 27 before flowing into the combustion chamber 19. Mixing is performed to form a homogeneous mixture. Incidentally, if the collision between the intake air flow and the injected gas fuel is performed downstream of the bent portion of the intake pipe 27 and in a region where the flow in the pipe axial direction is relatively fast and a region where the secondary flow exists, A homogeneous mixture is formed. Therefore, in the present invention, the bent portion of the intake pipe 27 includes a region downstream of the bent portion and in which the flow in the pipe axis direction is relatively fast and the region where the secondary flow exists.

1 to 5 show a first embodiment of the present invention.
Will be described. First, the engine operating state is read, and the output of the intake pressure sensor 12 is input to the ECU 16 to read the intake pipe pressure (step S).
1) Similarly, the engine speed is read from the crank angle sensor 13 (step S2), the water temperature of the engine body 17 is read from the water temperature sensor 14 (step S3), and the throttle opening is read from the throttle sensor 15 (step S2).
4). Next, the intake air amount is calculated based on the data read in steps S1 to S4 (step S5).

The fuel pressure is read from the fuel pressure sensor 10 (step S6), the fuel temperature is read from the fuel temperature sensor 11 (step S7), and the state of the natural gas fuel in the delivery pipe 5 is read. The valve opening time (fuel injection time) of the injection valve 6 is calculated from the data of the intake air amount and the engine rotation speed calculated in step S5, the fuel pressure and the fuel temperature are corrected, and the valve opening time of the injection valve 6 is calculated. Set (Step S
8).

The opening timing of the intake valve 21 is set in advance from the crank angle data, and the arrival time of the intake air to the bent portion is predicted from the intake air amount and the data of the opening timing of the intake valve 21 (step). S9). Then, taking into account the difference in fuel flight time due to the fuel pressure, the injection timing is set in consideration of the fuel pressure (step S10), and the injection is executed (step S11).

FIG. 6 shows a second embodiment of the method for mounting an injection valve for a natural gas engine according to the present invention. In the description of the configuration in FIG. 6, the same members as those in the first embodiment shown in FIGS. 1 to 5 are denoted by the same reference numerals as those in FIGS. In the second embodiment, the intake pipe 27a
A bent pipe of a bent back which is bent from the horizontal direction to the vertical direction and further bent in the U-shape in the horizontal direction is used, and a horizontally long portion of the intake pipe 27a extends above the cylinder head of the engine. The injection valve 6 is disposed on the outer wall of the portion of the intake pipe 27a which has been bent from the horizontal direction to the vertical direction, and the tip of the injection valve 6 is directed upstream, and the center line of the injection valve 6 (center line of injection). Are arranged outside the central axis of the bent pipe in the pipe axis direction, and the center line of the injection valve 6 is arranged so as to be parallel to the tangential direction of the bent part (the center part of the bending from the horizontal direction to the vertical direction). Other points of the second embodiment are the same as those of the first embodiment.

FIG. 7 shows a third embodiment of the method for mounting an injection valve for a natural gas engine according to the present invention. In the description of the configuration in FIG. 7, the same members as those in the first embodiment shown in FIGS. 1 to 5 are denoted by the same reference numerals as in FIGS. 1 to 5, and the description of the configuration is omitted. In the third embodiment, the intake pipe 27b
A 90 ° bend tube bent from the vertical direction to the horizontal direction is used, and is sprayed on the lower wall (downstream of the outer wall of the bent tube) somewhat downstream from the portion where the bending from the vertical direction to the horizontal direction is completed. A valve 6 is arranged. The tip of the injection valve 6 is directed to the upstream side so that the natural gas fuel is injected into a region where the flow of the intake air outside the central axis XX in the pipe axis direction of the curved pipe is relatively fast. The other points of the third embodiment are the same as those of the first embodiment.

[0017]

According to the first to third aspects of the present invention, the collision between the intake air flow and the injected gas fuel in the entire range from the low air amount to the high air amount is more than the center axis of the bent portion of the intake pipe. Occurrence occurs in a region where the speed of the intake air on the outside is relatively high.Natural gas fuel has a lower specific gravity than air, so it is diffused into the intake pipe while being pushed by the intake air flow and riding on the secondary flow, burning. Before flowing into the chamber, uniform mixing is performed in the intake pipe to form a uniform mixture. The homogeneous air-fuel mixture is completely burned in the combustion chamber, thereby purifying the exhaust gas (particularly, reducing CO) and improving the fuel consumption rate.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a first overall embodiment of the present invention.

FIG. 2 is a diagram showing flows of intake air and gas fuel according to the first embodiment of the present invention.

FIG. 3 (a) is a view showing a velocity distribution in the pipe axis direction of the first intake air according to the first embodiment of the present invention, and FIG. 3 (b) is a view showing FIG.
It is a figure which shows the secondary flow in the AA cross section of (a).

FIG. 4 (a) is a sectional view showing the mounting of the first injection valve according to the embodiment of the present invention, and FIG. 4 (b) is a right side view of FIG. 4 (a).

FIG. 5 is a flowchart showing control of the first injection valve according to the embodiment of the present invention.

FIG. 6 (a) is a sectional view showing a second embodiment of the injection valve according to the present invention, and FIG. 6 (b) is a top view of FIG. 6 (a).

7 (a) is a cross-sectional view showing the mounting of the third injection valve according to the third embodiment of the present invention, and FIG. 7 (b) is a bottom view of a main part of FIG. 7 (a).

FIG. 8 is a system diagram of a conventional injection valve for a natural gas engine.

FIG. 9 is a diagram showing flows of intake air and gas fuel in the system shown in FIG. 8;

[Explanation of symbols]

 6 Injection valve 25 Throttle valve 27,27a, 27b Intake pipe

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masahiko Masuchi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (3)

[Claims] An injection valve is disposed on a side wall of an intake pipe on a downstream side of a throttle valve, an injection port of the injection valve is directed in a direction facing intake air, and natural gas fuel is injected only during an intake stroke. In the mounting method of the injection valve for a natural gas engine, the injection valve is arranged outside and downstream of the bent portion of the intake pipe, and in a region where the speed of the intake air outside the central axis of the bent portion is relatively high. A method for mounting a natural gas engine injection valve configured to inject a natural gas fuel toward the engine. 2. In a cross section perpendicular to the central axis of the bent portion, toward a secondary flow flowing from the inside to the outside of the intake pipe,
The method for mounting an injection valve for a natural gas engine according to claim 1, wherein the injection valve is configured to be injected with a natural gas fuel. 3. The time at which the intake air reaches a curved portion is predicted based on the intake air amount and the intake valve opening timing, and natural gas fuel is injected by setting an injection timing in consideration of fuel pressure,
3. The method for mounting an injection valve for a natural gas engine according to claim 1, wherein the intake air and the injected gas fuel collide in the bent portion.