JP2014156852A - Compression ignition engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that, in a compression ignition engine equipped with a plurality of fuel injection valves in a cylinder, when a fuel concentration injected into a combustion chamber in a low load region is too low, ignition timing at each cycle is affected by variations in injection amount and turbulence in the cylinder and is not stable, and torque fluctuates.SOLUTION: In a compression injection engine equipped with a plurality of fuel injection valves in a cylinder, when a load is less than a first load at which a fuel amount injected from an injection valve is small and there is a possibility that combustion becomes unstable, fuel is injected from only one fuel injection valve of a plurality of fuel injection valves to secure an injection amount and attain both fuel economy and ignition stability.

Description

  The present invention relates to a compression ignition engine for injecting fuel directly into a combustion chamber in a cylinder.

Conventionally, in a direct-injection diesel engine, for example, as in Patent Document 1, a fuel injection valve is arranged at the center of the combustion chamber (center injection), a cavity is formed on the top surface of the piston, and the compression top dead center of the piston In general, fuel is injected radially into a cavity from a fuel injection valve disposed in the vicinity of the center of the combustion chamber to cause compression ignition.
In this method, a fuel injection valve is arranged in the center of the combustion chamber, and fuel is injected radially into the combustion chamber, so that air in the combustion chamber is evenly used.

FIG. 10 is a schematic diagram showing the combustion state of a diesel engine that performs conventional center injection. The fuel injected in the direction of the combustion chamber radius Rd from the fuel injection valve 205 disposed in the center of the combustion chamber 203 is compressed and ignited in the combustion chamber 203, and the flame 202 that has been compressed and ignited collides with the combustion chamber wall surface 204. The contact area of the flame 202 with respect to the combustion chamber wall surface 204 increases due to the collision, so that the heat energy of the flame 202 is transmitted from the wide range of the combustion chamber wall surface to the piston 213, resulting in a large cooling loss. Thermal efficiency will decrease.
In order to improve the cooling loss in such center injection, it is conceivable to increase the spray flight distance by increasing the distance from the fuel injection hole of the fuel injection valve to the wall surface of the combustion chamber. FIG. 11 is a schematic diagram showing a combustion state when the fuel injection valve is disposed outside the cylinder from the center of the combustion chamber (side injection). The fuel injected from the fuel injection valve 4A offset to the outside by the radius Rc from the center of the combustion chamber has a maximum spray flight distance from the fuel injection valve 4A to the combustion chamber wall surface 13a by a distance corresponding to the diameter of the combustion chamber 3. Can be secured. Therefore, as a result of suppressing direct contact between the flame 301 and the combustion chamber wall surface 13a, the cooling loss can be reduced.

  However, if the flight distance to the combustion chamber wall surface is secured as the side injection, the range in which the injection holes are arranged is limited, and the injection amount injected from the fuel injection valve is reduced.

If the fuel injection pressure is increased so as to secure the injection amount, the flow velocity at the time of the collision between the flame and the wall surface is increased, the heat transfer rate is increased, and the cooling loss is increased, so that the merit of the side injection is lost.
On the other hand, the inventors have disclosed a plurality of fuel injection valves, specifically, in order to improve the cooling loss and secure a sufficient fuel injection amount as disclosed in Japanese Patent Application No. 2013-018824. Has invented a diesel engine in which two fuel injection valves are arranged on the cylinder outer periphery and fuel is injected into the cylinder.

JP 2010-121433 A

According to the diesel engine described in the above Japanese Patent Application No. 2013-018824, the fuel is injected along the swirl flow formed in advance in the cylinder, so that fresh air is continuously supplied from the outer periphery of the cylinder to the base portion of the fuel spray. Is done. As a result, compared to the center-injected diesel engine with one commonly used fuel injection valve, the mixing of air and fuel is promoted to form a relatively lean mixture, and soot is generated. Can be suppressed.
However, in the diesel engine, since the mixing of air and fuel is promoted, the fuel concentration of the air-fuel mixture is excessively reduced in a low load region where the amount of fuel injection is small and soot generation does not become a problem. . An air-fuel mixture whose fuel concentration is too low is difficult to ignite, and is susceptible to various fluctuation factors such as variations in the injection amount, variations in the amount of air introduced into the engine cylinder, and turbulence in the cylinder. Therefore, the ignition timing for each cycle is not stable, and the torque varies. In particular, misfire may occur during cold start or operation in cold regions.

It is conceivable to increase the injection amount in order to reduce the cycle fluctuation and improve the combustion stability. However, if the injection amount is increased, an output exceeding the required output will be produced.
Therefore, in order to match the required output of the engine, it is necessary to retard the output of the engine by retarding the injection timing of injection from the fuel injection valve. However, the control for forcibly suppressing the output in this manner results in deterioration of the thermal efficiency with respect to the fuel injection amount, and the fuel efficiency is deteriorated.

  The present invention has been made in view of such a problem, and an object of the present invention is to improve fuel efficiency even in a predetermined operation region in which cycle fluctuations are large in a compression ignition engine having a plurality of injectors in a cylinder. This is where stable compression ignition combustion is performed without deteriorating.

In order to solve the above-mentioned problem, the invention according to claim 1 is a cylinder, a piston that reciprocates in the cylinder, a cylinder head that defines a combustion chamber together with the cylinder and the piston, and the cylinder of the cylinder head. A compression ignition engine having a plurality of fuel injection valves arranged on the outer peripheral side of the axis of the engine and having a controller for controlling the fuel injection valves,
Each of the plurality of fuel injection valves has a plurality of injection holes for directing fuel spray to the inner peripheral side of the cylinder from the central axis of the fuel injection valve, and the controller includes:
When the load of the compression ignition engine is equal to or higher than the first load, fuel is injected from the plurality of fuel injection valves,
When the load of the compression ignition engine is less than the first load, the plurality of fuel injection valves are controlled such that one of the plurality of fuel injection valves injects fuel. This is a compression ignition engine characterized by that.

  According to the present invention, in the low load operation region less than the first load, fuel is injected from only one fuel injection valve so that the fuel injection amount injected from one fuel injection valve is a plurality of fuel injection valves. Since the amount can be increased as compared with the case of injecting separately, it is possible to prevent the combustion from becoming unstable, and as a result, it is possible to improve the thermal efficiency.

  And in the operating region above the first load, fuel is injected by side injection from a plurality of fuel injection valves to one cylinder, thereby extending the spray flight distance from the fuel injection valves to the combustion chamber wall surface. The cooling loss from the wall surface of the combustion chamber can be reduced, and the thermal efficiency of the engine can be improved.

  As described above, in the present invention, the thermal efficiency of the engine can be improved over a wide range from the low load region to the high load region.

  Preferably, when the controller is less than the first load, the controller sets one fuel injection valve that injects fuel into the cylinder among the plurality of fuel injection valves every predetermined cycle. A compression ignition engine characterized by switching.

  According to this configuration, when fuel is injected only from a specific fuel injection valve among a plurality of fuel injection valves and the combustion cycle is repeatedly performed, the fuel injection valve that does not inject fuel will cause seizure. Can be prevented.

  The invention according to claim 3 is preferably a compression ignition engine characterized in that the controller controls the swirl control means so that the swirl flow becomes weak when the controller is less than the first load.

  According to this configuration, when the fuel injected into the cylinder is injected from only one fuel injection valve, the swirl flow generated in the cylinder is weakened, and the concentration distribution of the spray injected into the cylinder varies from cycle to cycle. Can be prevented. Therefore, combustion stability in the cylinder can be improved in a predetermined operation region, and in a region other than the predetermined operation region, the swirl flow is strengthened to improve the mixing of air and fuel in the cylinder. And the generation of wrinkles can be prevented.

  In the invention according to claim 4, preferably, two fuel injection valves are provided in the combustion chamber, and the controller offsets the sprays injected from the two fuel injection valves so that they do not collide with each other. A compression ignition engine that is controlled to inject in the same direction as a swirl flow.

  According to this configuration, the fuel injected from the two fuel injection valves provided in the cylinder is injected with an offset without colliding with each other. It is possible to prevent the air-fuel mixture from being generated, and to improve the mixing of the fuel and air in the cylinder by injecting in the same direction as the swirl flow and to prevent the generation of soot.

  As described above, according to the control device of the present invention, in a diesel engine provided with a plurality of fuel injection valves in a cylinder, the fuel consumption is stabilized over a wide region from a low load region to a high load region without deteriorating fuel consumption. Compression ignition combustion can be performed.

It is a figure showing the whole diesel engine composition figure concerning one embodiment of the present invention. It is sectional drawing which shows the structure of the engine main body of the said diesel engine. It is sectional drawing which shows the structure of the fuel injection valve (a 1st fuel injection valve and a 2nd fuel injection valve) of the said diesel engine. It is a side view of the front-end | tip part of the said fuel injection valve. It is a top view which shows the positional relationship of the said 1st fuel injection valve and the said 2nd fuel injection valve, and an injection direction. FIG. 6 is a side view corresponding to FIG. 5. It is a figure which shows the flowchart of this invention. The figure which shows the operation area | region of this invention It is a time chart figure which shows the injection timing of the said fuel injection valve. Diagram showing conventional center injection Diagram showing side injection

(1) Overall Configuration of Engine Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 and FIG. 2 show an overall configuration diagram of a diesel engine applied to this embodiment. The diesel engine shown in FIG. 1 is a four-cycle four-cylinder diesel engine mounted on a vehicle. For this diesel engine, an in-line four-cylinder engine body 1 in which four cylinders 2 are arranged in series, an intake passage 20 for introducing intake air into each cylinder, and exhaust gas generated by combustion in each cylinder And an exhaust passage 25 for discharging.
The intake passage 20 is provided with an independent intake passage 21 for distributing intake air to the intake port 6 of each cylinder 2, and a swirl control valve (for controlling the swirl flow in each cylinder) inside the independent intake passage 21. SCV) 19.
A surge tank 22 connected in common is provided in the upstream portion of each independent intake passage 21, and a single intake pipe 23 for introducing intake air to the surge tank 22 is provided in the upstream portion of the surge tank 22.

The exhaust passage 25 includes an independent exhaust passage 26 for discharging exhaust gas from the exhaust port 7 of each cylinder 2, and a collection portion 27 in which the downstream portions of the independent exhaust passages 26 are gathered together, and a collection portion 27. One exhaust pipe 28 extending from the downstream side to the downstream side is provided.
Each cylinder 2 is provided with a fuel injection valve for directly injecting fuel into the combustion chamber,
Each cylinder 2 is provided with two injectors, a first fuel injection valve 4A and a second fuel injection valve 4B.

The first fuel injection valve 4A of each cylinder 2 is connected to a common first common rail 30 extending in the column direction of the cylinders. The first common rail 30 is supplied with the fuel stored in the fuel tank 35 and made high-pressure by the first high-pressure fuel pump 32. The high-pressure fuel supplied to the first common rail 30 is injected from the first fuel injection valve 4A.
Similarly, the second fuel injection valve 4B is connected to a common second common rail 31 extending in the column direction of the cylinders. The second common rail 31 is supplied with the fuel stored in the fuel tank 35 and made the high pressure by the second high-pressure fuel pump 33. The high-pressure fuel supplied to the second common rail 31 is injected from the second fuel injection valve 4B.

As shown in FIG. 2, the configuration of each cylinder 2 of the engine body 1 includes a cylinder head 12 and a cylinder block 11 that forms each cylinder 2 below the cylinder head 12. A piston 13 is provided which is movably inserted. A combustion chamber 3 is defined above the piston 13, and the volume of the combustion chamber 3 is changed by the reciprocation of the piston 13.
In addition, an intake port 6 and an exhaust port 7 are formed in the cylinder head 12 of the engine 1 for each cylinder 2 and open to the ceiling portion of the combustion chamber 3. An intake valve 8 and an exhaust port 9 are individually provided at the opening ends of the intake port 6 and the exhaust port 7, and although not shown, the intake port 6 and the exhaust port are driven by a valve mechanism such as a camshaft. 7 are opened and closed at a predetermined timing.

  Further, the basic control of the engine 1 by the ECU 100 is not shown, but the detection values of various sensors (accelerator opening sensor, crank angle sensor, atmospheric pressure sensor, engine water temperature sensor) provided in the engine 1 are used. Based on this, the first and second fuel pumps 32 and 33 and the first and second fuel injection valves 4A and 4B are controlled. Detailed control means will be described later using the flowchart shown in FIG.

  In the combustion chamber 3, the fuel injected from the first and second fuel injection valves 4 </ b> A and 4 </ b> B is mixed with air, and the fuel is combusted by compression ignition in the combustion chamber 3. The chamber 3 is expanded and the piston 13 is reciprocated. Then, the reciprocating motion of the piston 13 is converted into the rotational motion of the crankshaft 5 that is the output shaft via the connecting rod 16. Since the diesel engine of the present embodiment is a four-cycle type, the four steps of intake, compression, expansion, and exhaust are repeatedly executed in this order in each cylinder 2 as the crankshaft 5 rotates.

(2) Configuration of Fuel Injection Valve FIG. 3 is a sectional view showing the structure of the tip of the fuel injection valve applied to this embodiment, and FIG. 4 is a side view of the fuel injection valve as viewed from the side.
As shown in the cross-sectional view of FIG. 3, the configuration of the fuel injection valve includes a tubular valve body 41 and a needle valve 43 that is movable in the axial direction at the center of the valve body 41. A fuel flow path 42 through which fuel can flow is formed by the needle valve 43. A plurality of injection holes 44 a to 44 f communicating with the internal fuel flow path 42 are formed at the distal end portion of the valve body 41. During the operation of the engine, the needle valve 43 is driven to move up and down by a solenoid (not shown). As the needle valve 43 is driven, the nozzle holes 44a to 44f are opened or closed.
In other words, when the needle valve 43 is moved downward until the end of the needle valve 43 comes into contact with the end of the valve body 41, the fuel flow path 42 is shut off and fuel is not injected from the injection holes 44a to 44f. Further, when the needle valve is moved upward, the fuel flow path 42 is released, the fuel is guided to the injection holes 44a to 44f, and the fuel is injected. The fuel injection amount is adjusted by controlling the release time of the nozzle holes 44a to 44f.

Next, the positional relationship between the first fuel injection valve 4A and the second fuel injection valve 4B in each cylinder 2 will be described with reference to plan views and side views shown in FIGS. FIG. 5 is a plan view of the first and second fuel injection valves 4A and 4B of a certain cylinder 2 as viewed from the ceiling side of the combustion chamber 3. FIG. 6 shows that the piston 13 of the cylinder 2 rises to the compression top dead center. It is a side view of the combustion chamber 3 when it did.
In FIG. 5, the peripheral edge of the cavity portion 13 a provided on the crown surface of the piston 13, that is, the boundary line between the cavity portion 13 a and the surrounding squish portion 13 b is represented by a two-dot chain line. The radius of the periphery of the cavity portion 13a is expressed as Rc.
As shown in FIGS. 5 and 6, the front end portion of the first fuel injection valve 4 </ b> A is one place on the ceiling of the combustion chamber 3 (the lower wall of the cylinder head 12), and the cavity from the center P of the combustion chamber 3 The portion 13a is disposed at a position offset to the intake side by a radius Rc.

On the other hand, the tip of the second fuel injection valve 4B is a position obtained by rotating the first injection valve 4A by 180 ° around the center P of the combustion chamber 3 in a plan view of the combustion chamber 3 as viewed from the ceiling side, that is, The first fuel injection valve 4A is disposed at a point-symmetrical position on the exhaust side across the center P of the combustion chamber 3. That is, the first injection valve 4 </ b> A and the second fuel injection valve 4 </ b> B are set to positions facing each other across the center P of the combustion chamber 4.
5 and 6, arrows a1 to a6 extending from the first fuel injection valve 4A and arrows b1 to b4 extending from the second fuel injection valve 4B are injected from the injection holes 44a to 44f of the fuel injection valve 4. It represents the center line of fuel spray.
Specifically, for the first fuel injection valve 4A, the spray from the nozzle hole 44a is a1, the spray from the nozzle hole 44b is a2, the spray from the nozzle hole 44c is a3, the spray from the nozzle hole 44d is a4, The spray from the hole 44e is a5, and the spray from the nozzle hole 44f is a6. However, in the plan view of FIG. 5, since the sprays from the nozzle holes having the same circumferential position appear to overlap each other, a set of a1, a2, a set of a3, a4, and a set of a5, a6 are shown in an overlapping manner. ing. Moreover, in the side view of FIG. 6, since the spray from the nozzle hole with the same up-down position appears to overlap, the group of a1, a3, a5 and the group of a2, a4, a6 are each overlapped and shown. The same applies to the second fuel injection valve 4B.

  In FIG. 5, lines passing through the centers of the first fuel injection valve 4A and the second fuel injection valve 4B are set, and this is defined as the symmetry axis SL. In addition, when the plane region of the combustion chamber 3 is divided into two by the symmetry axis SL, the first fuel injection valve 4A is provided at the tip of the first region D1 when the one side is the first region D1 and the other side is the second region D2. Fuel is injected radially from the six injection holes 44a to 44f toward the first region D1, and the second fuel injection valve 4B is fueled from the six injection holes 44a to 44f at the tip thereof toward the second region D2. Inject. As a result, the fuel sprays a1 to a6 injected from the first fuel injection valve 4A and the fuel sprays b1 to b6 injected from the second fuel injection valve 4B extend in directions offset from each other, and intersect in the middle. It is set not to be.

Of the six sprays a1 to a6 injected from the first fuel injection valve 4A, the sprays closest to the symmetry axis SL are the sprays a1 and a2 from the nozzle holes 44a and 44b. When the angle (spray angle) formed by the center line of the sprays a1 and a2 and the symmetry axis SL is r1, the spray angle r1 is set to 7 ° to 15 °.
Of the six sprays a1 to a6 injected from the first fuel injection valve 4A, the sprays second closest to the symmetry axis SL are the sprays a3 and a4 from the nozzle holes 44c and 44d. Further, the sprays farthest from the symmetry axis SL are the sprays a5 and a6 from the nozzle holes 44e and 44f. The average angle of these sprays, that is, the angle obtained by averaging the angle formed between the center line of the sprays a3 and a4 and the symmetry axis SL and the angle formed between the center line of the sprays a5 and a6 and the symmetry axis SL is average spray. Assuming that the angle is r2, the average spray angle r2 is set to 45 ± 10 °. The same applies to the second fuel injection valve 4B.

Further, as shown in FIG. 5, the flight directions of the sprays a1 to a6 from the first fuel injection valve 4A and the flight directions of the sprays b1 to b6 from the second injection valve 4B are formed in the combustion chamber 3, respectively. Is set to follow the flow of the swirl flow S1.
The six injection holes 44a to 44f respectively included in the first and second fuel injection valves 4A and 4B are formed so that the hole diameter is smaller as it corresponds to the spray farther from the symmetry axis SL. That is, the sprays a3, a4 (or b3, b4) that are second closest to the symmetry axis SL than the hole diameters of the injection holes 44a, 44b corresponding to the sprays a1, a2 (or b1, b2) closest to the symmetry axis SL. The corresponding nozzle holes 44c and 44d are set to have a smaller hole diameter, and the nozzle holes corresponding to the sprays a5 and a6 (or b5 and b6) farthest from the axis of symmetry SL than the hole diameter of the nozzle holes 44c and 44d. The hole diameters 44e and 44f are set to smaller values.

(3) Fuel Injection Control Means of Fuel Injection Valve Next, the fuel injection control means of the first and second fuel injection valves 4A and 4B will be described with reference to the flowchart of FIG. 7 and the first and second fuel injection valves 4A and 4A of FIG.
This will be specifically described with reference to a time chart showing the injection timing of 4B.

  First, in step S1 after the start, signals from various sensors 101 to 104 are input to the ECU, and in the subsequent step S2, an engine request output and an engine rotation speed are calculated. The engine rotation speed is calculated based on a signal from the crank angle sensor 102, and the engine request output is read from a map (not shown) stored in advance in the ECU 100 based on the engine rotation speed and the accelerator opening. The map is set so that the required engine output increases as the accelerator opening degree increases and the engine speed increases.

  In step S3, if the operating state of the engine 1 is less than the first load on the relatively low load side as shown in FIG. 8 from the engine required output and engine speed obtained in step 2, the answer is YES, and step S4 Proceed to In step S4, whether or not fuel has been injected from both the first and second fuel injection valves 4A and 4B in one cycle before the current combustion cycle for one cylinder 2 or one fuel It is determined whether fuel is injected only from the injection valve. If fuel injection is performed from both the first and second fuel injection valves 4A and 4B in the previous cycle, the answer is YES, and the process proceeds to the next step S5. In step S5, fuel injection is performed from the first fuel injection valve 4A, and the second fuel injection valve 4B maintains the valve closed state and shuts off the fuel injection before returning.

Thereby, even in an engine provided with two first and second fuel injection valves 4A and 4B in one cylinder 2 in a low load region less than the first load, fuel is injected only from the first fuel injection 4A. Thus, the combustion stability can be ensured without the concentration distribution of the spray injected into the cylinder fluctuating due to slight turbulence.
In the low-load operation region where combustion becomes unstable, for example, when the same amount of fuel is injected simultaneously from multiple fuel injection valves, combustion stability is improved by increasing the amount of fuel injected from multiple fuel injection valves can do. However, if the injection amount is increased, an output that exceeds the required output of the engine required in the low load operation region will be output.
In order to match the required output of the engine, it is necessary to perform control to retard the output of the engine by retarding the injection timing of injection from the fuel injection valve.
Forcibly suppressing the output in this manner results in a deterioration in thermal efficiency with respect to the fuel injection amount.
In the low-load operation region below the first load, fuel mixture can be formed at a concentration that ignites stably by injecting fuel only from one fuel injection valve, improving thermal efficiency while improving combustion stability It can be made.

In step S4, if fuel is injected only from one fuel injection valve in one cycle before the current combustion cycle for one cylinder 2, the determination becomes NO and the process proceeds to step S7. In step S7, it is determined whether or not the fuel is injected from the first fuel injection valve 4A in the previous cycle or whether the fuel is injected from the second fuel injection valve 4B.
Thereby, even in an engine provided with two first and second fuel injection valves 4A and 4B in one cylinder 2 in a low load region less than the first load, fuel is injected only from the first fuel injection 4A. Thus, the combustion stability can be improved without variation in the concentration distribution of the spray injected into the cylinder due to slight turbulence.

For example, in order to improve combustion stability by simultaneously injecting fuel from a plurality of fuel injection valves in a low load operation region where combustion becomes unstable, it is necessary to increase the amount of fuel injected from the plurality of fuel injection valves. is there. If the injection amount is increased, an output exceeding the required output of the engine required in the low load operation region will be output.
In order to match the required output of the engine, it is necessary to perform control to retard the output of the engine by retarding the injection timing of injection from the fuel injection valve.
Forcibly suppressing the output in this manner results in a deterioration in thermal efficiency with respect to the fuel injection amount.
That is, in a low load operation region less than the first load, it is possible to improve thermal efficiency while improving combustion stability by injecting fuel only from one fuel injection valve.

  In step S4, if fuel is injected only from one fuel injection valve in one cycle before the current combustion cycle for one cylinder 2, the determination becomes NO and the process proceeds to step S7. In step S7, it is determined whether or not the fuel is injected from the first fuel injection valve 4A in the previous cycle or whether the fuel is injected from the second fuel injection valve 4B.

  And if it is injecting from the 2nd fuel injection valve 4B by step S7, it will become NO and will progress to said step S5. Moreover, if it injects from 4 A of 1st fuel injection valves at step S7, it will become YES and will progress to step S8. In step S8, the first fuel injection valve 4A is closed to shut off fuel injection, and the second fuel injection valve 4B executes fuel injection and returns.

  Thus, the fuel injection valve on one side is seized by switching the fuel injection from the first fuel injection valve 4A and the fuel injection from the second fuel injection valve 4B for each cycle in a low load region less than the first load. Can be prevented.

  Further, if the operating state of the engine 1 is equal to or higher than the first load on the relatively high load side as shown in FIG. 8 in step S3, NO is determined, and both the first and second fuel injection valves 4A and 4B are used. The fuel is injected into one cylinder 2 and the process returns.

FIG. 9 is a time chart showing the injection timings of the first and second fuel injection valves 4A and 4B in the present embodiment.
In step S5 of the flowchart of FIG. 7, as shown in FIG. 9 (a), in the compression process, only the first fuel injection valve 4A is opened for a predetermined period from t1 to t2, and the second fuel injection valve 4B. Keeps the valve closed. In step S8, as shown in FIG. 9B, the first fuel injection valve 4A is kept closed, and only the second fuel injection valve 4B is opened for a predetermined period from t1 to t2. Fuel injection to 2 is performed.

  In step S6, as shown in FIG. 9C, fuel injection is performed by opening both the first and second fuel injection valves 4A and 4B for a predetermined period from t1 to t2.

In the above-described embodiment, the first fuel injection valve 4A and the second fuel injection valve 4B are switched every cycle, but may be switched every several cycles instead of every cycle.
Further, each injector may be a multi-stage injection in which fuel injection is performed a plurality of times during one cycle.
It goes without saying that various modifications can be made without departing from the scope of the present invention.

  The present invention relates to a compression ignition engine, and is particularly useful when performing stable combustion in a compression ignition engine having a plurality of fuel injection valves in a cylinder.

2 cylinder 3 combustion chamber 4A first fuel injection valve 4B second fuel injection valve 19 swirl control valve (SCV)
100 ECU
101 Accelerator opening sensor 102 Crank angle sensor 103 Atmospheric pressure sensor 104 Engine water temperature sensor

Claims (4)

A cylinder, a piston that reciprocates in the cylinder, a cylinder head that defines a combustion chamber together with the cylinder and the piston, and a plurality of fuel injection valves disposed on the outer peripheral side of the cylinder axis of the cylinder head. A compression ignition engine having a controller for controlling the fuel injection valve,
Each of the plurality of fuel injection valves has a plurality of injection holes that direct fuel spray to the inner peripheral side of the cylinder from the central axis of the fuel injection valve,
The controller
When the load of the compression ignition engine is equal to or higher than the first load, fuel is injected from the plurality of fuel injection valves,
When the load of the compression ignition engine is less than the first load, so that one fuel injection valve among the plurality of fuel injection valves injects fuel,
A compression ignition engine configured to control the plurality of fuel injection valves. The compression ignition engine according to claim 1,
The compression ignition engine characterized in that the controller switches one fuel injection valve that injects fuel into the cylinder among the plurality of fuel injection valves at every predetermined cycle when the controller is less than the first load. The compression ignition engine according to claim 1 or 2,
The compression ignition engine characterized by controlling the swirl control means so that the swirl flow becomes weak when the controller is less than the first load. The compression ignition engine according to any one of claims 1 to 3,
Two fuel injection valves are provided in the combustion chamber, and the controller controls the sprays injected from the two fuel injection valves to be offset so as not to collide with each other and to be injected in the same direction as the swirl flow of the intake air. A compression ignition engine characterized by that.

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