JP4256771B2 - Fuel control method and apparatus for diesel engine - Google Patents

Description

  According to the present invention, high-pressure fuel pressurized to high pressure by a fuel pressurizing means including a fuel pump and an accumulator is sent to a fuel injection valve, and the high-pressure fuel is divided into a plurality of times into the combustion chamber of the engine from the fuel injection valve. The present invention relates to a fuel control method for diesel engines and an apparatus therefor.

  In a diesel engine, in addition to reducing the fuel consumption rate, in order to reduce NOx (nitrogen oxide) at high rotation and high output, fuel pressurized to a high pressure by a fuel pump is common to each cylinder. A controller is provided with a plurality of control valves (solenoid valves) for accumulating pressure in a common rail (accumulator) provided, connecting the common rail and a fuel injection valve of each cylinder, and opening and closing a fuel return pipe. In recent years, many electronically controlled fuel injection devices that control the opening and closing of the control valve have been provided.

Examples of such an electronically controlled fuel injection device include Japanese Patent Application Laid-Open No. 11-294291 and Japanese Patent Application Laid-Open No. 2003-214279.
In the technique of Patent Document 1, fuel pressurized to a high pressure by a fuel pump is accumulated in a common rail provided in each cylinder, and the high-pressure fuel is supplied to a fuel injection valve of each cylinder through a high-pressure injection pipe at a predetermined timing. The high pressure fuel is introduced into the control chamber formed facing the rear end surface of the needle valve (needle valve) of the fuel injection valve through the introduction path from the common rail, and the high pressure fuel is supplied to the needle valve. Acts in the valve closing direction.
A fuel return path connecting the control chamber and the fuel tank is provided, and at the start of fuel injection, the normally open introduction side control valve provided in the introduction path from the common rail is closed, and the high pressure fuel to the control chamber is closed. And the normally closed return side control valve provided on the fuel return path is opened to release the pressing force from the back of the needle valve. As a result, the needle valve is pushed up by the pressure of the high pressure fuel introduced into the oil sump of the fuel injection valve to open, and the high pressure fuel is injected into the cylinder.
At the end of fuel injection, the return side control valve is closed and then the introduction side control valve is opened. As a result, high-pressure fuel is introduced into the control chamber, the needle valve is pushed down to close the valve, and the injection ends.

  In Patent Document 2, two fuel return pipes connected from the high-pressure fuel injection pipe to the fuel tank are provided in the high-pressure fuel injection pipe connecting the fuel pump and the fuel injection valve. Two return valves are provided with two solenoid valves for opening and closing the fuel return line and two throttles with different passage areas, and the opening timing of the two solenoid valves is changed to control the injection timing and the injection amount. It is configured as follows.

Since the electronically controlled fuel injection device as disclosed in Patent Document 1 or Patent Document 2 can freely change the fuel injection timing and the injection amount, the electronically controlled fuel injection device is equipped to reduce NOx. In order to promote ignition of the main injection whose injection timing is significantly delayed for the purpose of performing the pilot injection, a small amount of fuel is pilot-injected at an arbitrary injection timing prior to the main injection, and a plurality of fuel injections are combined. Split injection can be performed.
Japanese Patent Laid-Open No. 11-62603 JP 2003-214279 A

  FIG. 6 shows the first to third times in the case of performing split injection combining a plurality of fuel injections using the electronically controlled fuel injection device disclosed in Patent Document 1 or Patent Document 2. Changes in the amount of oxygen in the cylinder, the viscosity coefficient of air in the cylinder, and the energy required for mixing fuel and air in the course of the injection are shown in correspondence with the crank angle.

As is clear from FIG. 6, in the initial injection (first injection), there is a sufficient amount of air in the cylinder and the oxygen amount is sufficient, but the second injection, the third injection, and the injection As the later stage of the air, the amount of air and oxygen in the cylinder decreases, and the viscosity coefficient of the air increases due to the increase in the temperature in the cylinder accompanying the combustion of the injected fuel. Decreases.
For this reason, in such a conventional fuel injection method, although the first injection → second injection → third injection and the later stage of the injection, more energy is required to mix the fuel and air. However, no means for dealing with this is provided, and therefore, the amount of oxygen in the combustion zone, particularly the late combustion zone, is insufficient, and black smoke is likely to be generated.

  In view of the problems of the prior art, the present invention reduces the generation of black smoke by maintaining the required combustion energy in the entire combustion region in a fuel injection system that performs split injection combining a plurality of fuel injections. An object of the present invention is to provide a fuel control method and a fuel control device for a diesel engine that can avoid and reduce NOx.

  The present invention achieves such an object, and the first means is that fuel pressurized to high pressure by a fuel pressurizing means including a fuel pump is sent to a fuel injection valve, and the fuel is sent from the fuel injection valve to the engine. In the fuel control method for a diesel engine, the fuel injection pump constituting the fuel pressurizing means is composed of a unit pump provided for each cylinder. The fuel is injected into the combustion chamber intermittently at approximately equal intervals and divided into three or more times, and an injection-side control valve for controlling fuel supply from the unit pump to the fuel injection valve and return fuel from the fuel injection valve A return-side control valve to be controlled is provided, and the time difference from when the injection-side control valve is closed to when the return-side control valve is opened is adjusted to control the injection pressure from the fuel injection valve and at the later stage of injection Therefore, the injection pressure is controlled so as to increase sequentially, and further, the time difference between the opening and closing of the return side control valve in the closed state of the injection side control valve is adjusted to control the injection time from the fuel injection valve. The fuel injection energy (E) (E∝Qi × Pi, Q is the fuel injection amount, P is the injection pressure, i is the injection sequence (i = 1, 2). , 3)) is set so as to increase in the later stage of injection.

In consideration of the fact that the fuel injection energy (E1 to E3) is a function of the fuel injection amount (Q) and the fuel injection pressure (P), the fuel injection energy (E1 to E3) is preferably configured as follows.
The relationship between the fuel injection amount (Q1) in the first injection, the fuel injection amount (Q2) in the second injection, and the fuel injection amount (Q3) in the third injection is expressed as Q1 <Q2 <Q3. Set to.

The second means is an apparatus for carrying out the fuel control method, wherein fuel pressurized to high pressure by a fuel pressurizing means including a fuel pump is sent to the fuel injection valve, from which the fuel injection valve In a fuel control device for a diesel engine configured to inject fuel into a combustion chamber of an engine in a plurality of times, the fuel injection pump that constitutes the fuel pressurizing means is a unit pump provided for each cylinder, An injection-side control valve for controlling the fuel supply from the unit pump to the fuel injection valve by injecting fuel into the combustion chamber intermittently at three or more times at regular intervals using the pump, and the fuel injection valve A return-side control valve that controls the return fuel from the control valve, and controls the injection pressure from the fuel injection valve by adjusting the time difference from when the injection-side control valve is closed to when the return-side control valve is opened. Injection pressure is controlled to increase sequentially, further the injection time from adjusting the time difference between the closed state of the injection-side control valve to open and close the said return side control valve to the fuel injection valve according to become injection late And the fuel injection energy (E) (E∝Qi × Pi, Q is the fuel injection amount, P is the injection pressure, i is the injection sequence (i = 1, 2, 3)) is provided with a controller for controlling the opening and closing of the injection side control valve and the return side control valve so as to increase as the latter stage of the injection.

The second means is preferably configured as follows.
The controller determines that the relationship among the fuel injection amount (Q1) in the first injection, the fuel injection amount (Q2) in the second injection, and the fuel injection amount (Q3) in the third injection is Q1 <Q2. The control valve is controlled to open and close so that <Q3.

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However, according to the first and second means, high-pressure fuel is injected from the fuel injection valve in three or more times, and the fuel injection energy (E3) in the third injection is the first and second. Preferably, the first fuel injection energy (E1), the second fuel injection energy (E2), and the third fuel injection are set to be larger than the fuel injection energy (E1 and E2) in the second injection. Since the relationship of energy (E3) is set so as to increase in the later stage of injection such that E1 <E2 <E3, fuel injection is performed in the later stage of fuel injection in which the mixed energy of fuel and air decreases. The energy (E) is increased, and the diffusion of fuel in the combustion chamber increases the energy, and the mixing of fuel and air can be promoted.

As means for controlling the fuel injection energy (E), the relationship of the fuel injection pressure (P) is P1 <P2 <P3, and the relationship of the fuel injection period (T) is T1 <T2 <T3. Therefore, the fuel injection energy (E) can be easily and accurately controlled.
Thereby, it is possible to avoid poor mixing of fuel and air particularly in the later stage of injection and the generation of black smoke due to this, and to reduce the amount of NOx generated by properly mixing air and fuel in the later stage of injection.

Preferably, in the invention, the fuel is injected from the fuel injection valve in three or more times, and the nozzle area (A) of the fuel injection valve is configured to be variable.
The relationship between the fuel injection amount (Q1) in the first injection, the fuel injection amount (Q2) in the second injection, and the fuel injection amount (Q3) in the third injection is expressed as Q1 <Q2 <Q3. And the nozzle area (A3) in the third injection is set to be larger than the nozzle areas (A1) and (A2) in the first injection and the second injection,
Alternatively, the fuel injection pressure (P3) in the third injection is set higher than the fuel injection pressure (P1) in the first injection and the fuel injection pressure (P2) in the second injection.
With this configuration, by increasing the nozzle area (A3) in the later stage of injection or increasing the fuel injection pressure (P3) in the later stage of injection, the fuel injection is improved and the injection in the later stage of the injection is improved. It is possible to avoid the deterioration of combustion due to the extended period, and the fuel consumption rate can be reduced.
In the above means, the fuel injection pressure takes an average value (that is, average injection pressure) of the injection pressure during the injection period.

As described above, according to the present invention, high-pressure fuel is injected from the fuel injection valve in three or more times, and the fuel injection energy (E3) in the third injection increases so as to increase in the later stage of injection. Since the fuel injection energy (E1 and E2) in the first and second injections is set to be larger than the fuel injection energy (E1 and E2), the fuel injection energy increases as the later stage of the fuel injection in which the mixed energy of fuel and air decreases. (E) is increased, the diffusion energy of the fuel is increased in the combustion chamber, and the mixing of fuel and air can be promoted.
Thereby, it is possible to avoid poor mixing of fuel and air particularly in the later stage of injection and the generation of black smoke due to this, and to reduce the amount of NOx generated by properly mixing air and fuel in the later stage of injection.

  Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this example are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.

  FIG. 1 is an overall configuration diagram of a fuel injection and fuel control device for a diesel engine according to an embodiment of the present invention. FIG. 2 is a timing diagram showing the injection period in the three-part divided injection in the embodiment, FIG. 3 is a timing diagram showing the needle valve lift in the three-part divided injection in the embodiment, and FIG. 4 is in the embodiment. It is a timing diagram which shows the injection pressure in 3 times division | segmentation injection. FIG. 5 is an injection mode diagram in the above embodiment.

In FIG. 1 showing the overall configuration, 200 is a fuel injection pump, 100 is a fuel injection valve made up of a pressure accumulating injector, and both are provided in pairs for each cylinder.
In the fuel injection pump 200, reference numeral 30 denotes a unit pump, which is reciprocated via a roller 34 by rotation of the fuel cam 33 interlocked with the crankshaft of the engine and the fuel in the plunger chamber 32 by high pressure. A plunger 31 for pressurizing is provided. Since the structure of the unit pump 30 is known, a detailed description of the structure is omitted.

In the fuel injection valve 100, reference numeral 1 denotes an injection nozzle, which is a needle valve 2 fitted in the main body 001 so as to be able to reciprocate, and a needle valve spring 5 urged to pressurize the needle valve 2 in the valve closing direction. The oil reservoir 4 facing the lower surface of the needle valve 2, the plurality of injection holes 3 for injecting high-pressure fuel in the oil reservoir 4 into the combustion chamber by opening the needle valve 2, and the fuel communicated with the oil reservoir 4 The passages 6 and 07 are provided with a needle valve back chamber 05 which faces the back surface of the needle valve 2 and accommodates the needle valve spring 5.
Although not shown, the injection nozzle 1 is equipped with a known needle valve lift adjustment device that adjusts the lift of the needle valve 2 to adjust the area of the nozzle hole during fuel injection (fuel passage area). Has been.
Since the structure of the injection nozzle 1 is well known, detailed description of the structure is omitted.
Reference numeral 8 denotes a fuel passage for connecting the needle valve back chamber 05 and a fuel return pipe 9 to be described later, and reference numeral 12 denotes an orifice interposed between the fuel passage 8 and the fuel passage 7.

7 is an injection pipe provided for each cylinder, and connects the outlet of the plunger chamber 32 of the unit pump 30 and the fuel passage 07 of the injection nozzle 1.
A fuel tank 15 and a fuel supply pipe 14 connected to the fuel tank 15 are provided with a fuel supply pump 16, a filter 17, a relief valve 18 and the like.
A fuel return pipe 9 connects the fuel passage 8 and the fuel tank 15. The fuel return pipe 9 is provided with a check valve 19 that allows a flow from a return side control valve 11 to the fuel tank 15 to be described later. ing. A fuel oil pipe 13 connects the fuel supply pipe 14 and the fuel return pipe 9 to the injection pipe 7.

  An injection side control valve 10 is an electromagnetic valve provided on the fuel oil pipe 13 and opens and closes the pipe of the fuel oil pipe 13 in accordance with a control operation signal from a controller 20 described later. 11 is a return-side control valve comprising an electromagnetic valve provided in the fuel return pipe 9, and opens and closes the pipe of the fuel return pipe 9 in accordance with a control operation signal from the controller 20 described later.

A controller 20 includes an arithmetic control unit 21, a storage unit 22, and the like. The controller 20 controls opening and closing of the injection side control valve 10 via a control line 090 and a control line 09 based on a detection signal of an engine operating state described later. The return-side control valve is controlled to open and close.
Reference numeral 23 denotes a rotational speed detector for detecting the engine rotational speed, reference numeral 24 denotes a load detector for detecting engine load, reference numeral 25 denotes a pressure detector for detecting engine air supply pressure, lubricating oil pressure, water pressure, etc., and reference numeral 26 denotes engine supply power. It is a temperature detector that detects an air temperature, a lubricating oil temperature, a water temperature, and the like, and detection signals from these operation state detectors are input to the controller 20.

During operation of a diesel engine equipped with a fuel injection device having such a configuration, the high-pressure fuel pressurized by the reciprocating motion of the plunger 31 in the unit pump 30 provided for each cylinder is injected into the injection pipe 7, the fuel passage 07, and The fuel is supplied to the oil sump 4 facing the lower surface of the needle valve 2 of the injection nozzle 1 through the fuel passage 6, and is throttled by the orifice 12 and introduced into the needle valve back surface chamber 05 of the injection nozzle 1 through the fuel passage 8. It acts on the back surface of the valve 2 to act in the direction of pressing the needle valve 2 in the valve closing direction.
The controller 20 receives engine operation state detection signals including engine rotation number detection signals from the engine operation state detectors 23, 24, 25, and 26.

FIG. 5 shows temporal changes of the opening degree of the injection side control valve 10 and the return side control valve 11, the injection pressure of the unit pump 30, the injection pressure of the injection nozzle 1, and the fuel injection amount in such a fuel injection device.
In FIG. 1 and FIG. 5, the injection-side control valve is closed with the fuel passage 8 and the fuel return pipe 9 closed by the return-side control valve 11 in response to a control operation signal from the controller 20 under the permission of the operation state. When the supply-side fuel oil pipe 13 connected to the injection pipe 7 by 10 is closed, the fuel passage from the injection pipe 7 to the oil sump 4 of the injection nozzle 1 is sealed, and as shown in FIG. The pressure in the passage rises proportionally.

At the start of fuel injection, when the return side control valve 11 is opened with a predetermined opening / closing time difference C from the closing timing of the injection side control valve 10 by a control operation signal from the controller 20, The high-pressure fuel that has acted on the fuel passes through the return-side control valve 11 and escapes to the fuel return pipe 9.
As a result, the needle valve 2 of the injection nozzle 1 is pushed up against the elasticity of the needle valve spring 5 by the high-pressure fuel guided to the oil sump 4 facing the lower surface of the needle valve 2, and opens. Fuel is injected into the cylinder from the injection hole 3 of the injection nozzle 1 and used for combustion.

At this time, a part of the high-pressure fuel in the injection pipe 7 is throttled by the orifice 12 by opening the return side control valve 11, and then to the fuel return pipe 9 through the return side control valve 11. Is returned. Therefore, the fuel injection amount and the injection pressure from the injection nozzle 1 are determined by the difference between the discharge amount of the unit pump 30 and the return amount returned to the fuel return pipe 9 through the return side control valve 11.
At the end of fuel injection, when the injection side control valve 10 is opened by a control operation signal from the controller 20, the fuel pressure in the injection pipe 7 and the injection nozzle 1 is released, and the needle valve 2 is turned on. The valve is pushed down by the elasticity of the spring 5 to close the valve.
In FIG. 5, the injection amount (fuel injection amount) and the nozzle injection pressure are shown to rise in a step shape in the same figure, but actually change proportionally.

  In the present invention, the high-pressure fuel generated by the fuel injection pump 200 is injected from the fuel injection valve 100 into the combustion chamber of the engine in three or more times using the fuel injection device of the diesel engine having such a configuration. The present invention relates to a fuel control method and an apparatus therefor.

In the present invention, the controller 20 injects fuel from the fuel injection valve 100 in three or more times, and sets the fuel injection energy E in the first to third injections as follows. ing.
First, the fuel injection energy E can be expressed by the following equation (1).
Ei∝Qi × Pi (1)
Here, Q is the fuel injection amount.
P is the injection pressure.
i is the injection sequence (i = 1, 2, 3), the first injection is i = 1, the second injection
The injection is i = 2 and the third injection is i = 3.
In addition, the said injection pressure P takes the average value (namely, average injection pressure) of the injection pressure during an injection period.

In the present invention, the fuel injection energy E3 in the third injection (i = 3) is set to be larger than the fuel injection energy E1 in the first injection and the fuel injection energy E2 in the second injection. ing.
That is, E1 <E3 and E2 <E3 (2)
Preferably, the relationship between the fuel injection energies E1, E2, and E3 in the first, second, and third injections is set as in the following equation (3).
E1 <E2 <E3 (3)

In order to realize the relationship of the fuel injection energy E expressed by the equation (3), the controller 20 performs the following setting.
Since the fuel injection energy E is proportional to the fuel injection amount Q as shown in equation (1), the relationship of equation (3) (E1 <E2 <E3) is realized by the following equation (4).
Q1 <Q2 <Q3 (4)
Next, the fuel injection amount Q can be expressed by the following equation (5).
Qi∝Ti × Ai × (Pi) ^0.5 (5)
Where T is the injection period
A is the nozzle hole area, and if the needle valve lift is L,
Ai∝Li (6)

Further, in order to realize the relationship of the fuel injection amount Q expressed by the equation (4), the controller 20 performs the following setting.
Since the fuel injection amount Q is proportional to the injection period T and the nozzle hole area A as expressed by the equation (5), the relationship of the equation (4) (Q1 <Q2 <is given by the following equations (7) and (8)): Q3) is realized.
Regarding the fuel injection period T,
T1 <T2 <T3 (7)
Therefore, as shown in FIG. 2, the fuel injection period T1 in the first injection, the fuel injection period T2 in the second injection, and the fuel injection period T3 in the third injection are expressed by the equation (7). By setting T1 <T2 <T3, the relationship (4) (Q1 <Q2 <Q3) and the relationship (3) (E1 <E2 <E3) can be realized.
The fuel injection period T is set by the controller 20 in FIG. 5 when the injection side control valve 10 is closed and the return side control valve 11 is opened when the injection start T01 and the return side control valve 11 is closed when the return side control valve 11 is closed. To do.

Moreover, about the nozzle hole area A,
A1 <A2 <A3 (8)
And as shown in the equation (6), the nozzle hole area A is a function of the needle valve lift L. From the equation (8),
L1 <L2 <L3 (9)
Therefore, as shown in FIG. 3, the needle valve lift L1 in the first injection, the needle valve lift L2 in the second injection, and the needle valve lift L3 in the third injection are expressed by the above equation (9). By setting L1 <L2 <L3, the relationship (4) (Q1 <Q2 <Q3) and the relationship (3) (E1 <E2 <E3) can be realized.
The needle valve lift L is set by the controller 20 by adjusting a needle valve lift adjusting device (not shown) incorporated in the fuel injection valve 100 in FIG. To do.

Next, the equation (1) Ei∝Qi × Pi and
Formula (5) Qi∝Ti × Ai × (Pi) ^0.5
From the relationship
Ei∝ (Pi) ^1.5 (10)
Therefore, since the fuel injection energy E is proportional to the injection pressure P as shown in equation (10), the following equation (11) is established.
P1 <P2 <P3 (11)
Therefore, as shown in FIG. 4, the injection pressure P1 in the first injection, the injection pressure P2 in the second injection, and the injection pressure P3 in the third injection are expressed as P1 < By setting P2 <P3, it is possible to realize the relationship (Q1 <Q2 <Q3) of the equation (4) and the relationship (E1 <E2 <E3) of the equation (3).
The injection pressure P is set by the controller 20 by adjusting the time difference C between the closing timing T01 of the injection side control valve 10 and the injection start T01 timing at which the return side control valve 11 is opened in FIG. That is, when the time difference C is increased, the degree of increase in the injection pressure is increased, and when the time difference C is decreased, the degree of increase in the injection pressure is decreased.

According to this embodiment, high-pressure fuel is injected from the fuel injection valve 100 in three or more times, and the fuel injection energy E3 in the third injection is the fuel injection energy in the first and second injections. Preferably, the relationship between the first fuel injection energy E1, the second fuel injection energy E2, and the third fuel injection energy E3 is such that E1 <E2 <E3 so as to be larger than E1 and E2. Therefore, the fuel injection energy E is increased as the later stage of the fuel injection in which the mixing energy of the fuel and air is reduced, and the diffusion energy of the fuel is increased in the combustion chamber, so that the mixing of the fuel and the air is performed. Can be promoted.
Accordingly, as in the prior art, the fuel amount is reduced by the phenomenon in which the air amount and oxygen amount in the cylinder decrease from the first injection to the second injection, the third injection, and the later stage of the injection. Decrease in the mixing energy of air and air can be prevented by increasing the fuel injection energy E. In particular, poor mixing of fuel and air in the later stage of injection and the generation of black smoke due to this can be avoided, and air in the later stage of injection can be avoided. By appropriately mixing the fuel and the fuel, the amount of NOx generated can be reduced.

  Then, the relationship of the fuel injection pressure (P) is P1 <P2 <P3, the relationship of the fuel injection period (T) is T1 <T2 <T3, or the needle valve lift (L) By setting the relationship such that L1 <L2 <L3, the fuel injection energy (E) can be controlled easily and accurately.

As another embodiment of the present invention, high-pressure fuel is injected from the fuel injection valve 100 in three or more times, and the nozzle area A of the fuel injection valve, that is, the needle valve lift L can be changed. And the relationship between the fuel injection amount Q1 in the first injection, the fuel injection amount Q2 in the second injection, and the fuel injection amount Q3 in the third injection,
Q1 <Q2 <Q3 is set, that is, after setting the fuel injection period T1 <T2 <T3,
(1) The nozzle area A3 in the third injection is set to be larger than the nozzle areas A1 and A2 in the first injection and the second injection,
That is, the needle valve lifts L1 <L3 and L2 <L3 are set.
(2) The fuel injection pressure P3 in the third injection is set higher than the fuel injection pressure P1 in the first injection and the fuel injection pressure P2 in the second injection.
That is, the injection pressures P1 <P3 and P2 <P3 are set.

  According to this embodiment, the injection valve area L3 is increased by increasing the needle valve lift L3 in the later stage of injection, or the fuel injection pressure P3 is increased in the later stage of injection, so that the fuel injection is improved. It is possible to avoid the deterioration of the combustion due to the extension of the injection period in the later stage of the injection, and the fuel consumption rate can be reduced.

  According to the present invention, generation of black smoke can be avoided by maintaining required combustion energy in the entire combustion region in a fuel injection system that performs split injection combining a plurality of fuel injections. At the same time, a diesel engine that achieves low NOx can be provided.

1 is an overall configuration diagram of a fuel injection and fuel control device for a diesel engine according to an embodiment of the present invention. It is a timing diagram which shows the injection period in the 3 times division injection in the said Example. It is a timing diagram which shows the needle valve lift in 3 times division | segmentation injection in the said Example. It is a timing diagram which shows the injection pressure in the 3 times division | segmentation injection in the said Example. It is an injection mode diagram in the example. It is action | operation explanatory drawing concerning a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection nozzle 2 Needle valve 10 Injection side control valve 11 Return side control valve 20 Controller 30 Unit pump 100 Fuel injection valve 200 Fuel injection pump

Claims (4)

Fuel of a diesel engine in which fuel pressurized to high pressure by a fuel pressurizing means including a fuel pump is sent to a fuel injection valve, and the fuel is injected into the combustion chamber of the engine in a plurality of times from the fuel injection valve In the control method,
The fuel injection pump constituting the fuel pressurizing means comprises a unit pump provided for each cylinder, and the fuel is injected into the combustion chamber intermittently at three or more times at regular intervals using the pump, An injection side control valve for controlling fuel supply from the unit pump to the fuel injection valve and a return side control valve for controlling return fuel from the fuel injection valve are provided, and the return side control is performed after the injection side control valve is closed. The time difference until the valve is opened is adjusted to control the injection pressure from the fuel injection valve, and the injection pressure is controlled to increase sequentially as the injection late, and the return side in the closed state of the injection side control valve. The time difference between opening and closing the control valve is adjusted to control the injection time from the fuel injection valve, and control is performed so that the injection time becomes longer gradually as the latter stage of the injection. Gee (E) (E∝Qi × Pi, where Q is the fuel injection amount, P is the injection pressure, and i is the injection sequence (i = 1, 2, 3)) is set to increase as the latter stage of injection. A fuel control method for a diesel engine.   The relationship between the fuel injection amount (Q1) in the first injection, the fuel injection amount (Q2) in the second injection, and the fuel injection amount (Q3) in the third injection is expressed as Q1 <Q2 <Q3. The fuel control method for a diesel engine according to claim 1, wherein A diesel engine configured to send fuel pressurized to high pressure by a fuel pressurizing means including a fuel pump to a fuel injection valve, and inject the fuel into the combustion chamber of the engine in a plurality of times from the fuel injection valve In the fuel control device of
The fuel injection pump constituting the fuel pressurizing means comprises a unit pump provided for each cylinder, and the fuel is injected into the combustion chamber intermittently at three or more times at regular intervals using the pump, An injection side control valve for controlling fuel supply from the unit pump to the fuel injection valve and a return side control valve for controlling return fuel from the fuel injection valve are provided, and the return side control is performed after the injection side control valve is closed. The time difference until the valve is opened is adjusted to control the injection pressure from the fuel injection valve, and the injection pressure is controlled to increase sequentially as the injection late, and the return side in the closed state of the injection side control valve. The time difference between opening and closing the control valve is adjusted to control the injection time from the fuel injection valve, and control is performed so that the injection time becomes longer gradually as the latter stage of the injection. Ghee (E) (EαQi × Pi, Q is the amount of fuel injection, P is the injection pressure, i is ejection order (i = 1,2,3)) The injection-side control as to increase with increasing late injection A fuel control device for a diesel engine, comprising a controller that controls opening and closing of a valve and the return side control valve.   The controller determines that the relationship among the fuel injection amount (Q1) in the first injection, the fuel injection amount (Q2) in the second injection, and the fuel injection amount (Q3) in the third injection is Q1 <Q2. 4. The fuel control device for a diesel engine according to claim 3, wherein the control valve is controlled to open and close so that <Q3.

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