JP2962852B2 - Intake system for direct injection diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake device for a direct injection diesel engine having a combustion injection valve for directly injecting fuel into a combustion chamber.

[0002]

2. Description of the Related Art Conventionally, in a diesel engine in which fuel is spontaneously ignited by injecting fuel into a cylinder heated to a high temperature, a helical port is used as an intake port, and a mixture of the injected fuel and the intake air is swirled through the helical port. In addition, the combustion efficiency is increased to enhance the combustion efficiency, the output is improved, and the exhaust gas is purified by preventing the generation and emission of black smoke. Particularly, in a fuel supply system called a direct injection type (abbreviated as direct injection) in which fuel is injected directly into the combustion chamber without passing through the swirl chamber or the pre-combustion chamber, it is necessary to promote mixing of the injected fuel and intake air. is there.

For example, as disclosed in Japanese Patent Application Laid-Open No. Sho 62-174533, one cylinder is provided with two intake ports, and one of the intake ports is used as a helical port, and the other is used as a directional port to reduce swirl by the helical port. There is a configuration in which the air is mainly sucked from a helical port at a low rotation speed and mainly from a directional port at a high rotation speed. According to this, at the time of low rotation, the swirl by the intake from the helical port promotes the mixing of the injected fuel and the intake air, thereby increasing the combustion efficiency (air utilization rate), and reducing the excessive swirl at the high rotation. As a result, it is possible to prevent the cooling loss from increasing and improve the intake efficiency, and also to prevent ignition delay.

[0004]

However, in the conventional structure as described above, a strong swirl is generated even at a low load and a low rotation, the premixed combustion ratio is increased, the combustion temperature is increased, and as a result, nitrogen oxides are generated and discharged. There was a problem that the amount increased. or,
In recent years, from the viewpoint of pollution prevention, it has been desired to suppress the characteristic black smoke (generated by incomplete combustion due to low air usage rate) contained in the exhaust gas of diesel engines. It is what is desired.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and can obtain an optimum combustion state in accordance with an operation condition over the entire operation range, thereby improving output, purifying exhaust gas, and reducing fuel consumption. It is an object of the present invention to provide a direct-injection-type diesel engine intake device capable of being laid out compactly.

[0006]

For this reason, the intake device for a direct injection diesel engine according to the present invention includes a fuel injection valve for directly injecting fuel into a combustion chamber, and has two intake ports formed as helical ports adjacent to each other. Place an opening in the cylinder,
An on-off valve is provided in at least one of the intake passages leading to the two intake ports, an engine load detecting means for detecting an engine load, an engine speed detecting means for detecting an engine speed, and engine load information by engine load detection. A direct injection type diesel engine provided with control means for controlling the opening and closing of an on-off valve based on engine speed information obtained by the engine speed detection means. An opening / closing valve is provided in an intake passage leading to the intake port on the side, and both intake port passages leading to the helical portions of the intake ports are vertically arranged in an overlapping manner. The on-off valve is controlled to open and close so that air is taken in only from the intake port on the high side of the section. As a result, in a part of the low rotation region, a strong swirl is generated by the intake from only the intake port on the higher side of the helical portion, and the agitation and mixing of the fuel and the intake is promoted. Are arranged compactly in the vertical direction.

[0007] A part of the low rotation region may be a high load low rotation region. Thus, in a high-load low-speed range, a strong swirl is generated by intake from only the intake port on the higher side of the helical portion, and agitation and mixing of fuel and intake are promoted.

In addition, an on-off valve is provided in each of the intake passages leading to both intake ports, and the control means takes in air only from the intake port on the higher side of the helical portion in the high-load low-rotation region, and controls the low-load region and the high-rotation region. In this example, the on-off valves are controlled to open and close so that air is taken in from both intake ports, and in other operation ranges, air is taken in only from the intake port on the lower side of the helical portion. According to this configuration, in the high-load low-rotation region, a stronger swirl is generated by the intake from only the intake port on the high side of the helical portion, and the agitation and mixing of the fuel and the intake is promoted. In this case, the swirls generated by the intake air from both intake ports cancel each other, resulting in a weak swirl, and in the operating range in which the intake is performed only from the intake port on the lower side of the helical portion, the swirl is intermediate between the two.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a schematic configuration of an engine to which an embodiment of an intake device for a direct injection diesel engine according to the present invention is applied, and FIG. 2 is a plan view equivalent view showing intake and exhaust ports. It is.

The illustrated engine 10 is configured as a two-intake valve and a two-exhaust valve, and the cylinder head 12 corresponding to the opening of the cylinder 11 in the direction orthogonal to the cylinder row arrangement direction indicated by the arrow in FIG. Two intake ports (first intake port 21) are provided on one side with respect to the center line CL of the cylinder.
And the second intake port 22) has an exhaust port 3 on the other side.
Openings 1 and 32 are arranged adjacent to each other in the center line CL direction. That is, the opening positions of the intake ports 21 and 22 and the exhaust ports 31 and 32 to the cylinder 11 are arranged substantially symmetrically with respect to a center line CL orthogonal to the cylinder row arrangement direction. A recess is formed at the center of the top of the piston 16 inserted into the cylinder 11. When the piston 16 is located near the top dead center, the combustion chamber 15 is formed by the recess and the lower surface of the cylinder head 12. Is formed. The intake ports 21 and 22 are independently connected to one side surface of the cylinder head 12 parallel to the cylinder arrangement direction via port passages 21A and 22A, respectively, and the exhaust ports 31 and 32 are connected to the intake ports 21 and 22 respectively.
The side of the cylinder head 12 opposite to the two communicating side is communicated via port passages 31A and 32A.

As shown in the perspective views of FIGS. 3 and 4, the intake ports 21 and 22 are so-called helical ports in which openings (port portions 21B and 22B) toward the cylinder 11 are formed in a spiral shape. The height H (shown in FIG. 5) of the port portion 21B of the first intake port 21 far from the side surface of the cylinder head 12 communicated by the port passages 21A, 22A is the port portion of the other second intake port 22. 22B
The port passage 2 of the second intake port 22 is formed higher.
The port passage 21A of the first intake port 21 is formed in the cylinder head 12 as a positional relationship overlapping the port passage 21A above 2A. With the overlapping arrangement of the port passages 21A and 22A, the intake ports 21 and 22 can be compactly arranged, and the degree of freedom of design such as arrangement of a head bolt (not shown) for fixing the cylinder head 12 to the cylinder block is improved.

Here, as shown in FIG. 5, which corresponds to a developed view of the central longitudinal section of the passage, the first intake port 21 has a diameter d of the opening of the port B, and a horizontal line of the lower side AD of the port passage A. Angle: θ, height of the intersection of the lower side AD of the port passage A with the port portion B: H, h = πd × tan θ, where H> h, and the port passage indicated by a solid arrow in FIG. Both the upward flow along the upper side AU of A and the downward flow along the lower side AD of the port passage A indicated by the dashed arrow are swirled by the helical port portion 21B, and are formed so as to generate strong swirl. On the other hand, the second intake port 22
, The height H of the intersection of the lower side AD of the port passage A with the port portion B is set as H <h, and the upward flow indicated by the solid arrow in FIG. 5 is swirled at the port portion 22A. However, the downward flow indicated by the dashed arrow flows into the cylinder without being swirled, and as a result, a swirl weaker than the swirl of the intake air of the first intake port 21 is formed. . FIG. 5 is a diagram corresponding to the first intake port 21.

The swirls 21S and 22S generated by the intake air from the intake ports 21 and 22 are generated with their turning centers 21C and 22C shifted as shown in FIG. If
At the center position of the cylinder 11 (the center position of the combustion chamber 15), the swirl directions from both the intake ports 21 and 22 are opposed to each other, and the swirl interferes and cancels each other. As a result, the second intake port 22 alone sucks air. The swirl is weaker than the swirl in the case. Cylinder 1 of port portion 21B, 22B of each intake port 21, 22
1, poppet valves 61 and 62, which are opening and closing valves for opening and closing the intake ports 21 and 22, respectively, are disposed.
3 is pressed by a rocker arm 14 that swings in synchronization with the rotation of the crankshaft of the engine 10 to open and close the intake ports 21 and 22.

Cylinder head 1 of intake ports 21 and 22
2 are connected to respective manifold passages 71, 72 of an intake manifold 70A that is formed integrally with the surge tank 70 by branching from the surge tank 70. The respective passages 71, 72 can be opened and closed in the respective manifold passages 71, 72. Simple on-off valves 81 and 82 are provided. These on-off valves 8
1, 82 are respectively connected to diaphragms 83, 83 as actuators, and the respective diaphragms 83, 8
The vacuum pump 3 is connected to a crankshaft of the engine and is supplied with a negative pressure from a vacuum pump 84 that is rotationally driven by the crankshaft via negative pressure supply passages 86, 86 provided with solenoid valves 85, 85 on the way. The on / off valves 81, 82 are opened / closed depending on whether or not negative pressure is supplied to the diaphragms 83, 83 by opening / closing the solenoid valves 85, 85. The solenoid valves 85, 85 are driven and controlled by a control device 90 as a control means. Therefore, each of the on-off valves 81, 82 is controlled to be opened and closed by the control device 90.

On the other hand, the cylinder 11 of the cylinder head 12
In the center corresponding to the center of the combustion chamber 15, a unit injector 91 as a fuel injection valve, which is a pressure accumulating injector having a pressure accumulating tank, makes its injection nozzle 91A face the cylinder 11 (combustion chamber 15). The unit injector 91 is supplied with high-pressure fuel from a fuel injection pump 92. The fuel injection pump 92 distributes and pumps a predetermined amount of fuel to each cylinder in accordance with the load, and includes a rotating member (not shown) linked to rotate synchronously with the crankshaft of the engine 10. , And is operated by an accelerator pedal AP via a governor (not shown). In other words, the fuel is pressurized and timely distributed to each cylinder by the rotating member that rotates in synchronization with the rotation of the engine 10 (the rotation of the crankshaft), and the injection amount is adjusted using the operation amount of the accelerator pedal AP as the load information. It is something like that. In addition, the unit injector 91 is provided at the center of the cylinder 11 (combustion chamber 1) as an intake 2 valve and an exhaust 2 valve.
By arranging in the center of 5), the distance from the unit injector 91 to the end of the combustion chamber 15 can be made equal, which can contribute to improvement in combustion efficiency.

The control device 90 obtains information on the rotation speed of the engine 10 and information on the operation amount of the accelerator pedal AP from the fuel injection pump 92, and based on these information, the manifold passages 71, connected to the intake ports 21, 22. The on / off valves 81 and 82 provided in the 72 are controlled to open and close. That is, in the present embodiment, the fuel injection pump 92 serves as both the engine load detecting means and the engine speed detecting means. Here, in accordance with the control table shown in FIG. 7, the control device 90 sets the high first intake port 21 of the port 21B in the high-load low-speed range.
The opening / closing valve 81 provided in the manifold passage 71 leading to the second intake port 22 is closed while the opening / closing valve 82 provided in the manifold passage 72 leading to the second intake port 22 is closed. Both the on-off valves 81 and 82 of the manifold passages 71 and 72 that reach the intake ports 21 and 22 are both opened, and are further operated in other operating ranges (i.e., a middle load low speed range,
In a medium load middle rotation range and a high load middle rotation range), the on-off valve 81 provided in the manifold passage 71 leading to the first intake port 21 is closed, and the manifold reaching the second intake port 22 having a low port portion 22B. The on-off valve 82 provided in the passage 72 is opened.

Thus, in a high-load low-speed range where the injection pressure is low and the atomization of the injected fuel is not sufficient, the port portion 21B
Intake is performed from the first intake port 21 having a high pressure, and a strong swirl is generated in the cylinder 11 to promote the mixing of the intake air and the injected fuel, thereby improving the combustion efficiency (air utilization rate). As a result, the output is improved. In particular, the generation of black smoke at the time of starting acceleration is suppressed. In the low-load range and the high-speed range, the intake is performed from the intake ports 21 and 22, so that the swirls from the intake ports 21 and 22 cancel each other as described above, resulting in a weak swirl. , And the combustion temperature is prevented from rising due to high-speed combustion due to ignition delay, so that generation of nitrogen oxides is suppressed. Also, especially in the high rotation range, the increase in the injection pressure promotes atomization of the fuel, so strong swirl is not necessary.On the other hand, in the case of strong swirl, the fuel consumption deteriorates due to the increase in cooling loss. Can be prevented. In other operation ranges such as a middle load low rotation region, a medium load middle rotation region, and a high load middle rotation region, intake is performed from the second intake port 22 having a low port portion 22B, and a swirl intermediate between the two. Swirl is generated, and by appropriate mixing of intake air and fuel, improvement in combustion efficiency, suppression of increase in combustion temperature, and improvement in fuel efficiency can be achieved.

The structure of controlling the intake from the intake ports 21 and 22 by controlling the opening and closing of the on-off valves 81 and 82 is not limited to the above embodiment, but can be changed as appropriate. For example, in the above embodiment, the medium load low rotation range, the medium load middle rotation range,
Although the high-load medium rotation region was set to the medium swirl region, such a medium swirl region was not provided, and as shown in the control table of FIG. 8, in the high-load low rotation region, only the high first intake port 21 of the port portion 21B was used. Intake is performed to generate strong swirl, and in other operation regions, both intake ports 21 and 22 are used.
Even if a configuration is adopted in which a weak swirl is performed by performing intake from the intake port, substantially the same effect as in the above-described embodiment can be obtained. According to this configuration, intake is always supplied from the second intake port 22 having a low port portion 21B. In order to perform the operation, the on-off valve 82 provided in the manifold passage 72 leading to the second intake port 22 in the above embodiment becomes unnecessary.

[0019]

As described above, according to the intake device for a direct injection diesel engine according to the present invention, a strong swirl is generated by inhaling air from only one intake port which is a helical port in a high-load, low-speed range. Further, the stirring and mixing of the fuel and the intake air is promoted, and the combustion efficiency (air utilization rate) is improved. As a result, the output can be improved and the generation of black smoke particularly at the time of starting acceleration is suppressed. In addition, by making the helical part height of both intake ports different, and in the high-load, low-speed range, intake is performed only from the intake port on the higher side of the helical part, thereby producing a stronger swirl and promoting agitation and mixing of fuel and intake air. As a result, the combustion efficiency is improved, and the intake passages to both intake ports are vertically overlapped, so that the arrangement of the intake passages is facilitated and a compact configuration can be achieved.

Furthermore, in the high-load low-speed range, air is taken in only from the intake port on the higher side of the helical portion, in the low-load range and the high-speed range, air is taken in from both intake ports. By configuring the intake port only from the intake port, in a high-load, low-speed range, the intake from only the intake port on the higher side of the helical section produces a strong swirl, which promotes agitation and mixing of fuel and intake air, resulting in combustion efficiency. In the low-load range and the high-rev range, the swirls generated by the intake air from both intake ports interfere with each other and cancel each other out, resulting in a weak swirl. Since the increase in the combustion temperature due to the high-speed combustion is prevented, the combustion temperature is reduced and the generation of nitrogen oxides is suppressed. Also, especially in the high rotation range, the injection pressure increases to promote atomization of the fuel, so that strong swirl is not required. Conversely, weak swirl prevents deterioration of fuel efficiency due to increased cooling loss caused by strong swirl. Can be.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a schematic configuration of an engine to which an embodiment of an intake device for a direct injection diesel engine according to the present invention is applied.

FIG. 2 is a plan view-equivalent view showing intake and exhaust ports.

FIG. 3 is a perspective view of a first intake port and an intake passage leading to the first intake port.

FIG. 4 is a perspective view of a second intake port and an intake passage leading to the second intake port.

FIG. 5 is a development equivalent view of a longitudinal section at the center of the passage of the intake port.

FIG. 6 is an explanatory view corresponding to a plan view of a combustion chamber showing swirl generated by intake air from each intake port.

FIG. 7 is a control table of an on-off valve with respect to an operation range.

FIG. 8 shows another embodiment of the control table of the on-off valve for the operating range.

[Description of Signs] 10 ... Engine 21 ... First intake port (higher intake port on port) 21A ... Port passage 21B ... Port (helical) 22 ... Second intake port (lower intake on port) Port) 22A ... Port passage 22B ... Port portion (helical portion) 71,72 ... Manifold passage (intake passage) 81,82 ... Open / close valve 90 ... Control device (control means) 91 ... Unit injector (fuel injection valve) 92 ... Fuel Injection pump (engine load detecting means, engine speed detecting means)

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masaaki Kashimoto 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Co., Ltd. (56) References JP-A-61-244830 (JP, A) −28839 (JP, U) Actually open 1987-145940 (JP, U) (58) Fields investigated (Int.Cl. ⁶ , DB name) F02B 31/02 F02D 9/02 361

Claims (3)

(57) [Claims] A fuel injection valve for injecting fuel directly into a combustion chamber, wherein two intake ports formed as helical ports are provided.
An open / close valve is provided in at least one intake passage leading to both intake ports, an engine load detecting means for detecting an engine load, and an engine speed detecting means for detecting an engine speed. A direct-injection diesel engine comprising: engine load information based on the engine load detection; and control means for controlling opening and closing of the on-off valve based on engine speed information based on the engine speed detection means. The on-off valve is provided at least in an intake passage leading to the intake port on the lower side of the helical portion, and the two intake port passages leading to the helical portions of the two intake ports are vertically overlapped. The control means, only in the high-side intake port of the helical portion in a part of the low rotation range Configuration was able to open and close operation control the on-off valve to air intake apparatus for a direct injection type diesel engine according to claim. 2. The intake device for a direct injection diesel engine according to claim 1, wherein a part of the low rotation region is a high load low rotation region. 3. An on-off valve is provided in each of the intake passages leading to both of the intake ports, and the control means controls the on-off operation of each of the on-off valves, so that the higher side of the helical portion in the high-load low-rotation region. , The intake port is taken from both intake ports in the low load range and the high rotation range, and the intake port is taken only from the intake port on the lower side of the helical portion in the other operation range. An intake device for a direct injection diesel engine according to claim 2.