Patent Application
20190040814
The present invention relates to a fuel injection valve control device that is used in an internal combustion engine such as a Gasoline engine.
Recently, demands for improvement in fuel consumption of gasoline engines in vehicles have increased and a cylinder injection type engine that directly injects fuel into a combustion chamber, ignites an air-fuel mixture of the injected fuel and sucked air with an ignition plug, and explodes the air-fuel mixture has been widely used as an engine excellent in the fuel consumption. However, in the cylinder injection type engine, because a distance from an injection point to a wall surface is short, the fuel is likely to adhere to the inside of the combustion chamber and suppression of a particle matter (PM) generated by incomplete combustion of the fuel adhered to the wall surface having a low temperature becomes a problem. To solve this problem and develop a direct injection engine with low fuel consumption and low exhaust gas, optimization of combustion in the combustion chamber is necessary.
There are various operation situations such as a high-load operation, a low-load operation, and cold starting in operations of the vehicles.
Therefore, in the cylinder injection type engine, to perform optimum combustion depending on the operation situations, homogeneous combustion for forming a homogeneous air-fuel mixture in a cylinder and burning the air-fuel mixture and stratified charge combustion for forming a thick air-fuel mixture around an ignition plug are used separately.
To achieve both the homogeneous combustion and the stratified charge combustion, a method has been suggested in which a plurality of fuel injection valves for directly injecting the fuel into the combustion chamber is provided for each cylinder. For example, PTL 1 describes technology in which two fuel injection valves are provided for each cylinder, a first fuel injection valve is used at the time of the homogeneous combustion, and a second fuel injection valve is used at the time of the stratified charge combustion. PTL 1 discloses technology in which a fuel injection valve with a large static flow is used at the time of the homogeneous combustion and a fuel injection valve with a small static flow and short penetration is used at the time of the stratified charge combustion.
PTL 1: JP 2010-196506 A
In the cylinder injection type engine, a homogeneous combustion mode in which, when a high-load operation is performed, fuel is injected in an intake stroke, a homogeneous air-fuel mixture is formed in the cylinder, and the air-fuel mixture is burned and a stratified charge combustion mode in which, when a load is relatively low, the fuel is injected at the latter stage of a compression stroke, a thick air-fuel mixture is stratified around an ignition plug and the air-fuel mixture is burned are known.
In the stratified charge combustion mode, burning is performed in a state in which an air-fuel ratio of the entire cylinder is larger than a theoretical air-fuel ratio. Therefore, to perform stable ignition, it is necessary to arrange fuel having an appropriate concentration around the ignition plug. For this reason, a spray guide system for arranging the fuel injection valve and the ignition plug in proximity to a center portion of an upper portion of the combustion chamber, injecting the fuel from the fuel injection valve to the vicinity of an electrode of the ignition plug, and igniting the fuel with the ignition plug is devised. In this system, because a distance from an injection point to the ignition plug is short, a required travel distance of the spray is very small. For this reason, a fuel injection valve having small penetration force (penetration) of the spray is required.
On the other hand, in the homogeneous combustion mode, fuel injection is performed in a state in which an intake valve is opened, the fuel is mixed by a gas flow (tumble flow) flowing from an intake port to the inside of the combustion chamber, and a homogeneous air-fuel mixture is formed. At this time, if the penetration force of the spray is not sufficient, the spray is caused to flow to the side of the wall surface in the cylinder by the tumble flow, and the homogeneous air-fuel mixture cannot be formed. For this reason, a fuel injection valve having large penetration force (long penetration) is required.
To solve such conflicting demands for the fuel injection valve, a method of providing a plurality of fuel injection valves for directly injecting the fuel into the combustion chamber for each cylinder is suggested.
In the technology disclosed in PTL 1, the two fuel injection valves are provided for each cylinder, the first fuel injection valve with the long penetration is used at the time of the homogeneous combustion, and the second fuel injection valve with the short penetration is used at the time of the stratified charge combustion, so that it is possible to form an optimum spray in each mode of the homogeneous combustion mode and the stratified charge combustion mode and achieve high performance.
In the intake stroke, the strength of the tumble flow changes depending on an engine speed. When the engine rotates at a high speed, a movement speed of a piston is high and a flow rate of gas flowing into the cylinder per unit time increases, so that the tumble flow becomes strong. For this reason, a spray with the long penetration is required to prevent the spray from being flown by the tumble flow.
On the other hand, when the engine rotates at a low speed, the movement speed of the piston is low and the flow rate of the gas flowing into the cylinder per unit time decreases, so that the tumble flow becomes weak. For this reason, mixing force by the tumble flow decreases and it is difficult to form a homogeneous air-fuel mixture in the cylinder.
In the technology disclosed in PTL 1, when the homogeneous combustion mode is set at the time of the low rotation and high load, the fuel injection valve with the long penetration is used in a state in which the tumble flow is weak and the mixing force is small. For this reason, adhesion of the fuel to the wall surface may increase and homogeneity may be deteriorated.
The present invention has been made in view of the above problem and an object thereof is to provide a fuel injection valve capable of forming a homogeneous air-fuel mixture in homogeneous combustion at a low engine speed and a control device thereof.
To solve the above problem, a control device of a fuel injection valve according to the present invention is provided with a fluid injection valve that is configured separately from the fuel injection valve and has a function of injecting a fluid and includes a control unit that performs control such that fuel is injected from the fuel injection valve and then controls the fluid injection valve such that the fluid is injected from the fluid injection valve and the fuel injected from the fuel injection valve is stirred.
According to the present invention, a homogeneous air-fuel mixture can be formed in homogeneous combustion at a low engine speed. Other configurations, functions, and effects of the present invention will be described in detail in the following embodiments.
Hereinafter, embodiments of the present invention will be described.
A control device of a fuel injection valve according to a first embodiment of the present invention will be described below using
The piston 103 is connected to a crankshaft 115 via a connecting rod 114 and an engine speed can be detected by a crank angle sensor 116. A value of the rotation speed is sent to an engine control unit (ECU) 118. A starter motor not shown in the drawings is connected to the crankshaft 115 and at the time of starting an engine, the crankshaft 115 can be rotated by the starter motor and the engine can be started. A water temperature sensor 117 is provided in the cylinder block 102 and can detect a temperature of engine cooling water not shown in the drawings. The temperature of the engine cooling water is sent to the ECU 118.
Although
Fuel is stored in a fuel tank 109 and is sent to a high-pressure fuel pump 111 by a feed pump 110. The feed pump 110 boosts fuel to about 0.3 MPa and sends the fuel to the high-pressure fuel pump 111. The fuel boosted by the high-pressure fuel pump 111 is sent to a common rail 112. The high-pressure fuel pump 111 boosts the fuel to about 30 MPa and sends the fuel to the common rail 112. A fuel pressure sensor 113 is provided in the common rail 112 to detect a fuel pressure. A value of the fuel pressure is sent to the ECU 118.
Next, a detailed shape of the fuel injection valve will be described using
Next, a control method of homogeneous combustion using the fuel injection valve according to this embodiment will be described using
In control S03, after performing injection from the fuel injection valve in the intake stroke, injection from the fluid injection valve is performed and in control S03, after performing the injection from the fluid injection valve in the intake stroke, ignition is performed by control S05 in the latter half of the compression stroke.
FIG. is a schematic diagram of current pulses to operate the fuel injection valve and the fluid injection valve in this embodiment. In the internal combustion engine according to this embodiment, the fluid injection valve that is configured separately from the fuel injection valve and has a function of injecting a fluid is provided.
Next, a form in the combustion chamber will be described.
The CPU (control unit) of the ECU 118 controls the fuel injection valve 119 by control S03 shown in
Next, the CPU (control unit) of the ECU 118 controls the fluid injection valve 121 by control S04 and causes the fluid to be injected into the combustion chamber 104. An injected fluid 302 stirs the spray 300 injected from the fuel injection valve and forms a homogeneous air-fuel mixture in the combustion chamber 104. Generally, when the engine rotates at a low speed, the air flow in the cylinder is insufficient and it is difficult to form a homogeneous air-fuel mixture. In this embodiment, the fluid injection valve is caused to be delayed compared with the fuel injection valve and injects the fluid, thereby stirring the fuel in the combustion chamber. As a result, even when the air flow in the cylinder is slow, the homogeneous air-fuel mixture can be formed. According to this embodiment, it is possible to form the homogeneous air-fuel mixture in homogeneous combustion when the engine rotates at a low speed.
The CPU (control unit) of the ECU 118 controls the ignition plug 120 by control S05 shown in
Although this embodiment does not limit the position of the fuel injection valve, the fuel injection valve 119 is arranged on the upper portion of the internal combustion engine, so that the fuel can be injected over a wider range. By injecting the fuel over the wide range, a degree of homogeneity of the air-fuel mixture can be increased. In addition, the fuel injection valve 119 is disposed in the vicinity of the ignition plug, so that combustion stability at the time of the stratified charge combustion can be increased.
Generally, in the case where the stratified charge combustion is performed by a spray guide system, if the injection is performed in the compression stroke, a spray angle decreases. When the fuel injection valve used for the stratified charge combustion is used in the intake stroke, the spray angle increases. Therefore, a spray angle θ1 is preferably designed such that the fuel does not adhere to the cylinder wall surface in the intake stroke and a sufficient spray angle is obtained when the fuel is injected in the compression stroke.
On the other hand, the fluid injection valve 121 is provided on a side surface and forms a longitudinal vortex 303 in the cylinder. By forming the longitudinal vortex, it is possible to suitably stir the spray 300 injected from the fuel injection valve 119. By maximizing a distance between the fluid injection valve 121 and the wall surface, an amount of fuel adhering to the wall surface can be reduced when the fluid injected from the fluid injection valve 121 is the fuel.
In the homogeneous combustion at the high rotation, the tumble flow forms the vortex in the longitudinal direction and the homogeneous air-fuel mixture is formed in the cylinder by the vortex. At the time of the low rotation, the tumble flow is weak and it is difficult to form the longitudinal vortex. However, the longitudinal vortex is formed by the fluid injection valve 121, so that the homogeneous air-fuel mixture obtained at the time of the high rotation can be formed.
That is, the fuel injection valve 119 is attached to the upper portion of the internal combustion engine and the fluid injection valve 121 is attached to the side surface of the internal combustion engine, so that the degree of homogeneity of the air-fuel mixture can be increased.
However, an effect of the invention does not limit the arrangement of the fuel injection valve and the arrangement of the ignition plug. For example, even when the arrangement of the fuel injection valve 119 and the fluid injection valve 121 is reversed, the effect of the invention is achieved. However, in the case where the fuel injection valve is arranged on the side portion and the ignition plug is arranged on the center, at least one spray direction may be oriented to the ignition plug to increase combustion stability at the time of the stratified charge combustion.
In this embodiment, when a top dead center is set to 0 deg, fuel injection timing is, for example, 60 deg. That is, the CPU (control unit) of the ECU 118 performs control such that the fuel is injected from the fuel injection valve 119, in a state in which the piston descends, and then controls the fuel injection valve 119 and the fluid injection valve 121 such that the fluid is injected from the fluid injection valve 121 and the fuel injected from the fuel injection valve is stirred. The piston descends as shown by a piston movement direction 305, so that the fluid flows downward into the cylinder, thereby assisting the flow of the fluid 302. As a result, the longitudinal vortex 303 in the cylinder is strengthened and the spray 300 injected from the fuel injection valve 119 can be suitably stirred.
In addition, an injection hole axis of the fuel injection valve 119 and an injection hole axis of the fluid injection valve 121 preferably intersect each other at the side of the ignition plug rather than the piston in a state in which the piston is at a bottom dead center. That is, as shown in
The fluid injection valve described above may be a fuel injection valve for stirring separated from the fuel injection valve and the CPU (control unit) of the ECU 118 may perform control such that penetration of the spray from the fuel injection valve for stirring is longer than penetration of the spray from the fuel injection valve. Thereby, the same effect of the invention is obtained. The principle thereof will be described below.
In
Next, a control method of the homogeneous combustion using the fuel injection valve for stirring according to this embodiment will be described using
When the high rotation is determined by control S12, control is preferably performed such that the fuel is injected from the fuel injection valve for stirring by control S16. This is because the tumble flow is strengthened when the engine rotates at a high speed and a spray with long penetration is required to cause the spray not to be flown by the tumble flow. For this reason, at the time of the high rotation, the fuel is injected from the fuel injection valve for stirring with long penetration, so that the homogeneous air-fuel mixture can be formed.
In addition, the length of the penetration of the fuel injection valve 121 is preferably optimized such that the degree of homogeneity increases, in a range in which the fuel does not adhere to the piston. When the engine speed is low, the air flow in the combustion chamber 104 is slow and the fuel is likely to adhere to the combustion chamber wall surface or the piston. In
Next, a method of setting the length of the penetration will be described.
The penetration can be set also by a ratio of a length L of the injection hole and an outlet diameter D; L/D. Generally, when L/D is large, the injection speed increases and the penetration becomes longer. For this reason, the fluid injection valve 121 is a fuel injection valve for stirring separated from the fuel injection valve 119 and the injection hole formed in the fuel injection valve for stirring has L/D larger than that in the fuel injection valve 119, so that it is possible to stir the spray 300 injected from the fuel injection valve 119 and form a homogeneous air-fuel mixture in the cylinder.
In addition, the penetration can be changed also in multi-stage injection using short pulse injection or short pulse injection. In the short pulse injection, because the penetration becomes short, the amount of adhesion to the wall surface can be further reduced. On the other hand, in the short pulse injection, because an injection amount per pulse decreases, a necessary amount of fuel is preferably injected by the multi-stage injection.
By using the present invention, it is possible to increase the combustion speed while increasing the degree of homogeneity of the air-fuel mixture. By improving the combustion speed, the combustion can be performed in a short period and a constant volume degree of the combustion process can be increased. By increasing the constant volume degree, heat efficiency is improved and fuel consumption efficiency is improved.
When the motion energy representing the magnitude of the average motion of the flow increases, turbulent motion energy representing the magnitude of the turbulence of the flow also increases. A propagation speed of a flame correlates with the turbulent motion energy and when the turbulence motion energy increases, an effect of improving the combustion speed can be expected.
That is, by performing control such that the fuel is injected from the fuel injection valve and then controlling the fluid injection valve such that the fluid is injected from the fluid injection valve and the fuel injected from the fluid injection valve is stirred, the turbulence motion energy in the cylinder increases and the combustion speed can be increased while the degree of homogeneity of the air-fuel mixture is increased.
This embodiment functions suitably when the engine speed is low and the air flow in the cylinder is slow. Therefore, it can be used at the time of starting the engine, for example. At the time of starting the engine, a warm-up operation may be performed for the purpose of warming up a catalyst. When the engine speed increases and a mode becomes a warm-up operation mode, control for raising the exhaust temperature is performed, for example, by retarding the ignition timing, so that the warm-up of the catalyst can be performed suitably while the degree of homogeneity of the air-fuel mixture is increased.
That is, the CPU (control unit) of the ECU 118 controls the fluid injection valve such that the fuel injected from the fuel injection valve is stirred in a state in which the piston of the internal combustion engine is at the vicinity of the bottom dead center after performing control such that injection is performed from the fuel injection valve in one stroke of piston. If the internal combustion engine enters the warming-up operation, the CPU switches the control into control for retarding the ignition timing. As a result, the warm-up of the catalyst can be suitably performed while the degree of homogeneity of the air-fuel mixture is increased.
The effect of the present invention is not limited to the case where the rotation speed is low and the same effect can be obtained when the air flow in the cylinder is slow. For example, even when the intake valve is opened in the vicinity of the top dead center and the negative pressure in the cylinder is insufficient, the same effect is obtained.
A fuel injection valve according to a second embodiment of the present invention will be described below using
In the second embodiment shown in
In the second embodiment shown in
A fuel injection valve according to a third embodiment of the present invention will be described below using
Gas fuel such as CNG is injected from the gas injection valve 501. A control method is the same as that in the first embodiment.
In addition, air may be injected from the gas injection valve 501. In the case of injecting the air, a compressor instead of the tank for storing the gas may be provided and air may be supplied from an intake port. In addition, a part of recirculated exhaust gas may be injected from the gas injection valve 501. That is, a CPU (control unit) of an ECU 118 performs control such that the air or the recirculated exhaust is injected from the gas injection valve 501 for stirring and the fuel injected from the fuel injection valve 119 is stirred. In this case, similar to the air, the recirculated exhaust gas is boosted by the compressor and is injected from the gas injection valve 501.
When the gas is injected from the gas injection valve, the fuel does not adhere to a piston. Therefore, injection timing from a fluid injection valve is not related to a position of the piston. For example, the CPU (control unit) of the ECU 118 performs control such that the fuel is injected from the fuel injection valve in a state in which the piston is at 40 deg to 60 deg and then injection is preformed from the fluid injection valve in a state in which the piston is at 60 deg to 80 deg and the fuel is mixed with the gas early and is vaporized. As a result, adhesion of the fuel to a wall surface can be suitably reduced.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-015030 | Jan 2016 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/083876 | 11/16/2016 | WO | 00 |
