JPH10231730A - Diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of excessive EGR during the rapid increase and the rapid decrease of an engine load and prevent temporary worsening of smoke. SOLUTION: A diesel engine 1 comprises a variable capacity type turbo supercharger 3 having a moving nozzle vane; an EGR device 4 having an EGR valve 15; a controller 13 to control the opening of the moving nozzle vane and the EGR valve 15 based on engine operation states Ne and Acc; and the controller 13 which, during the rapid increase of an engine load, starts control of the opening of the moving nozzle vane after control of the opening of the EGR valve 15 is started.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine obtained by combining a variable displacement turbocharger with an EGR device.

[0002]

2. Description of the Related Art Generally, in a diesel engine employing an electronically controlled injection system, a controller, which is an electronic control unit, determines an optimum target injection amount Q based on an engine operating state, and performs control in accordance with the target injection amount Q. A signal is sent to the electronic governor actuator to operate the governor actuator, so that an optimal amount of fuel is pumped from the fuel injection pump. The controller constantly detects the engine operating state from the output signals of various sensors, and among them, particularly the engine speed Ne.
The target injection amount Q is determined based on a signal indicating the accelerator opening Acc (corresponding to the engine load).

The procedure is as follows. The controller first determines the engine speed Ne and the accelerator opening A
The basic target injection amount Q _BASE is read from cc according to the map M3 shown in FIG. Here, the map M3 is created in advance by an actual machine test or the like and stored in the ROM in the controller. And Q _BASE and the previous target injection quantity Q
Calculates the difference ΔQ = Q _BASE -Q _-1 and _-1, a K × Delta] Q multiplied by the correction coefficient K to, is added to the previous target injection amount Q _-1, this new target injection The quantity Q = Q _-1 + K × ΔQ is determined.

[0004] On the other hand, a combination of such a diesel engine with a variable displacement turbocharger is known. As disclosed in Japanese Patent Application Laid-Open No. 61-237831, a variable capacity turbocharger has a plurality of movable nozzle vanes at the turbine inlet, and controls the opening degree of the nozzle vanes to increase the supercharging pressure (compressor pressure). Discharge pressure). The nozzle vanes are connected by an interlocking mechanism, and an actuator driving force is input to the interlocking mechanism to change the angle of the nozzle vanes and change the turbine inlet area. The actuator is operated based on a control signal from the controller. The controller has
The nozzle vane opening control map (map M
1) is stored in advance, and the controller uses the engine speed Ne and the target injection amount Q in accordance with the map M1 according to the map M1.
The target nozzle vane openings S _{1 to} S ₄ are determined, and a control signal is output so as to achieve the nozzle vane opening.

In the map M1, the vane opening S is
S₁, S_Two, S_Three, S_FourIt is changed to four stages of
S₁S fully opened from_FourThe degree of opening gradually
It is increased stepwise. That is, low speed and high load (fuel injection amount
Large), the intake air amount is relative to the fuel injection amount.
The vane opening S is small (S =
S ₁) To increase the exhaust gas velocity at the turbine inlet,
The number of revolutions is increased, and the supercharging pressure is increased to increase the amount of intake air.
Also, in the high-speed region where the intake air amount is sufficient, or
Conversely, in the load region, the vane opening S is increased (S = S_Four)
Reduce pump pressure and pumping loss.
You.

Furthermore, it is possible to combine an EGR device in such a diesel engine. EGR
The device circulates a part of the exhaust gas into the intake air to lower the combustion temperature and suppress the generation of NOx. In this case, the exhaust passage and the intake passage are connected by an EGR passage as a bypass passage, and the EGR passage is controlled to be opened and closed by an EGR valve. Also in this case, the controller again sets the target EGR valve opening H ₀ according to the EGR valve opening control map (map M2) as shown in FIG.
It determines to H _4, and outputs a control signal.

In the map M2, the EGR valve opening H
Is changed into five stages of H ₀ , H ₁ , H ₂ , H ₃ and H ₄ ,
Its opening As leading from H ₀ to the fully closed H ₄ to be fully opened is sequentially increased stepwise. That is, the higher the load area, the more the amount of fresh air is required. Therefore, the EGR amount (EGR rate) is reduced by reducing the valve opening H, and the amount of fresh air (relative amount) is increased, thereby increasing the amount of smoke. N while suppressing generation
The emission level of Ox is suppressed to a predetermined value (for example, a regulation value) or less. In particular, in a region where a high speed or a high load (for example, Q> 60 (%)) exceeding a predetermined value is set, the valve opening H is set to H ₀ (= 0) at which the valve is completely closed, and the EGR device is set to the same state as non-operation EGR has been discontinued. As a result, only fresh air is burned, and a high output can be obtained. In addition, even during the engine warm-up operation, since the temperature in the cylinder is low and the combustion is not stable, the valve opening H is uniform regardless of the engine operating state.
Is fixed to H ₀ and EGR is stopped.

[0008]

The electronically controlled diesel engine has a variable capacity turbocharger and an E-type diesel engine.
When combined with a GR device, the following problems occur.

That is, when the engine load suddenly increases during acceleration or climbing a steep hill, specifically when the accelerator pedal is suddenly depressed, it is necessary to obtain a high output immediately. Become. In such a case, the exhaust pressure also increases rapidly. Therefore, as shown in Japanese Patent Application Laid-Open No. 60-162048, it is necessary to reduce the degree of opening of the EGR valve and prevent the exhaust gas from circulating to prevent deterioration of smoke.

However, conventionally, the change of the opening degree is started at the same time, and the change takes a certain amount of time.
In particular, in the closing process of the EGR valve, the exhaust pressure may increase, and the exhaust gas may be circulated to temporarily deteriorate the smoke.

This will be specifically described with reference to FIG.
First, it is assumed that the accelerator pedal is depressed for acceleration at time T _A. In this case, the target injection amount Q is gradually increased, and the engine speed Ne is gradually increased. on the other hand,
Immediately after the depression, the opening change of the nozzle vane opening and the EGR valve opening is started, and the opening (the actual opening Sr, H) is changed.
r) is gradually reduced toward the minimum S ₁ and H ₀ . However, in practice the opening degree variation is completed is the time T ₁ of the after a predetermined time has elapsed, since during this time EGR valve opening Hr is not fully closed H _0, discharge with reduced small nozzle vanes opening Sr The pressure may increase, and excessive EGR may be performed to temporarily increase the smoke SM.

Further, such deterioration of the smoke may also occur when the engine load suddenly decreases. That is, FIG.
In 3, the acceleration at the time T _B is completed, and suddenly releases the accelerator pedal in order to shift to the steady running. Then, as the Q decreases, the opening degrees Sr and Hr of the nozzle vane and the EGR valve are changed in the increasing direction. However, immediately after the end of the acceleration, the exhaust pressure is in a high state.
When the valve is opened, too much EGR may occur and smoke SM may temporarily increase.

[0013]

SUMMARY OF THE INVENTION A diesel engine according to the present invention includes a variable-capacity turbocharger having a movable nozzle vane, an EGR device having an EGR valve, and the movable nozzle vane based on an engine operating state. The above EG
A controller for controlling the opening of the R valve, the controller including a controller for starting the opening control of the movable nozzle vane after starting the opening control of the EGR valve when the engine load is rapidly increased. . according to this,
When the engine load suddenly increases, the control for closing the EGR valve is started first, and then the control for closing the movable nozzle vane is started. For this reason, the EGR valve can be closed before the exhaust pressure rises, whereby deterioration of smoke during acceleration or the like can be prevented.

Further, the controller may start the opening control of the movable nozzle vane and then start the opening control of the EGR valve when the engine load suddenly decreases. By doing so, contrary to the above, the EGR valve can be opened after the exhaust pressure is reduced, thereby preventing the deterioration of smoke at the time of deceleration or the like.

Further, the controller may start the control of closing the EGR valve and start the opening control of the intake throttle valve provided in the intake passage at the same time when the engine load suddenly increases.

With this arrangement, when the engine load is rapidly increased, that is, in an accelerating state, the amount of exhaust gas supplied to the turbine is increased by controlling the closing of the EGR valve to increase the boost pressure, and the amount of intake is increased by controlling the opening of the intake throttle valve to increase the boost. The pressure increases. Since the control for closing the EGR valve and the control for opening the intake throttle valve are simultaneously performed, the boost pressure quickly rises, and the acceleration performance is improved.

Further, the controller may start the opening control of the EGR valve after starting the closing control of the intake throttle valve provided in the intake passage when the engine load suddenly decreases.

With this arrangement, when the engine load is rapidly reduced, that is, in a decelerating state, after the negative pressure is generated on the downstream side by the closing control of the intake throttle valve and the differential pressure between the intake system and the exhaust system increases, the EGR valve is activated. Since the opening control is performed, the EGR rate does not decrease and the increase in NOx can be prevented.

[0019]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a diesel engine according to the present invention. As shown in the figure, a diesel engine 1 has a variable capacity turbocharger 3
And an EGR device 4. The variable-capacity turbocharger 3 has a turbine 6 provided in the middle of the exhaust passage 5 and a compressor 8 provided in the middle of the intake passage 7. Nozzle vanes are provided so as to appropriately change the speed of exhaust gas given to the turbine wheel 9.

The nozzle vanes are driven by an actuator 10 via an interlock mechanism (not shown). As the actuator 10, a negative pressure actuator using a diaphragm is adopted here, but the type is not particularly limited. The actuator 10 is a negative pressure pipe 11
is connected to the negative pressure pump 11 via a, and drives the movable nozzle vane in the opening direction according to the supplied negative pressure value. The magnitude of the supply negative pressure is controlled by a negative pressure control valve 12, and the negative pressure control valve 12 is operated by receiving a control signal from a controller 13 which is an electronic control unit.

The EGR device 4 includes an EGR passage 14 as a bypass passage connecting the exhaust passage 5 and the intake passage 7,
An EGR valve 15 provided on the intake passage 7 side of the R passage 14. The EGR valve 15 also has a diaphragm as an actuator and is operated by negative pressure, but the type is not limited. The EGR valve 15 opens the EGR passage 14 as appropriate by operating the valve body in the opening direction according to the supplied negative pressure value. The EGR valve 15 receives a negative pressure supply from the negative pressure pump 17 through the negative pressure pipe 16 as described above, and the negative pressure value is controlled by the negative pressure control valve 18 and the controller 13.

The controller 13 detects the operating state of the engine based on the output signals of various sensors. Typically, the controller 13 determines the engine speed Ne based on the output signal of the engine speed sensor 19 and calculates the accelerator opening degree. Sensor 2
The accelerator opening Acc is detected based on the output signal of 0. Further, the controller 13 detects the actual opening Sr of the movable nozzle vane based on the output signal of the vane opening sensor 21 and outputs the EGR valve opening sensor 22.
The actual opening degree Hr of the EGR valve 15 is detected on the basis of the output signal. Further, the controller 13
Calculates the target injection amount Q based on the engine operating state, as described later, and outputs a control signal corresponding to the target injection amount Q to the electronic governor actuator 24 of the fuel injection pump 23.

In the ROM of the controller 13,
The maps M1, M2, and M3 shown in FIGS. 2, 3, and 4 are stored in advance. Note that these maps M1, M2,
M3 is created in advance through actual machine tests and the like. As described above, the map M1 shown in FIG. 2 is a nozzle vane opening control map, in which the nozzle vane opening S
, Depending on the value of the engine speed Ne and the target injection quantity Q, it is adapted to be increased sequentially 4 stages to S ₄ which is a fully open from S ₁ to be fully closed. A map M2 shown in FIG. 3 is an EGR valve opening control map of the EGR device 4, in which the opening H of the EGR valve 15 is completely controlled according to the values of the engine speed Ne and the target injection amount Q. fully closed H ₀ (= ₀₎ is adapted to be increased sequentially out until H ₄ as a fully open from. Further, the map M shown in FIG.
Reference numeral 3 denotes a basic target injection amount map, which is an engine speed Ne.
This is for reading the basic target injection amount Q _BASE according to the values of and the accelerator opening Acc.

In accordance with these maps M1, M2, M3, the controller 13 performs the following operations in accordance with the control flowchart shown in FIG.
The GR valve opening control is executed.

First, in step ST1, based on output signals from the engine speed sensor 19 and the accelerator opening sensor 20, values of the engine speed Ne and the accelerator opening Acc are input. Next, in step ST2, the basic target injection amount Q _BASE is read from the map M3, and in step ST3
And the difference ΔQ between Q _BASE and the previous target injection amount Q ₋₁ is ΔQ = Q _BASE
Calculate -Q _-1 .

Next, in step ST4, the absolute value of ΔQ |
It is determined whether ΔQ | is smaller than a predetermined determination value α. If | ΔQ | <α, it is determined that the vehicle is in a steady state in which no rapid acceleration / deceleration is performed, and in step ST5,
The target injection amount Q, the target vane opening S, and the target EGR valve opening H are determined. If | ΔQ | ≧ α, it is determined that a transition is being made during rapid acceleration / deceleration, and in step ST6, it is determined whether acceleration or deceleration is being performed. If ΔQ> 0, it is determined that the vehicle is accelerating, and in step ST7, the target injection amount Q, the target vane opening S, and the target EGR valve opening H are determined. If ΔQ ≦ 0, it is determined that the vehicle is decelerating, and in step ST8, the target injection amount Q, the target vane opening S, and the target EGR valve opening H are determined.

If the values of Q, S, and H are determined in step ST5, ST7, or ST8, in step ST9,
Control signals corresponding to the values of Q, S, and H are output to the negative pressure control valves 12, 18 and the electronic governor actuator 24, respectively, to execute predetermined fuel injection and opening degree change.

Next, steps ST5, ST7 and ST8
Will be described in detail. First, step ST5 is as shown in FIG. First, step ST51
Then, the obtained injection amount difference ΔQ is multiplied by a correction coefficient K _1, and the result is added to the previous target injection amount Q ₋₁ to obtain the current target injection amount Q = Q ₋₁ + K ₁ × ΔQ. Here, in the steady state, ΔQ
From the value is small, the correction factor K ₁ is set to 1.
At this time, the difference Q-Q _-1 between the current injection amount and the previous injection amount becomes small, and the injection amount is finely adjusted. Next, in step ST52, the engine speed N is calculated from the map M1.
e and the target injection amount Q, the target vane opening S is set to S ₁ ,
... is determined to be one of the S _4. Note that S ₁ ,..., S ₄ are collectively indicated as Sn. Further, in step ST53,
The target EGR valve opening H is determined to be one of H ₀ ,..., H ₄ from the map M2. Similarly, H ₀ ,..., H ₄ are also indicated as Hn. Thereafter, the process proceeds to step ST9 to output each control signal.

Next, the contents of step ST7 are as shown in FIG. Steps ST7 and S7 described below
The contents of T8 are also shown in the time chart shown in FIG.

When acceleration is determined in step ST6 (FIG. 9)
At time T _A ), first in step ST7,
In 71 determines the target EGR valve opening H in H _0.
As a result, the EGR valve 15 is operated toward fully closed. Next, in step ST72, the actual opening Hr of the EGR valve 15 is input based on the output signal of the EGR valve opening sensor 22. Further, in step ST73, EGR
Makes a comparison between the actual opening Hr and the target opening degree H = H ₀ of the valve 15, it is determined whether they are equal. Where EG
When the R valve opening is not currently H ₀ (Hr ≠ H ₀ )
Makes the target vane opening S this time equal to the previous target vane opening S- ₁ in step ST74. As a result, the nozzle vane is not operated at all and is fixed at the current position. After this, step ST
At 75, the target injection quantity Q is determined by the equation Q = Q _-1 + K ₀ × ΔQ. Here, since the EGR valve 15 has not been fully closed yet, the correction coefficient K ₀ is set to 0, thereby stopping the increase in the injection amount and preventing excessive fuel injection. Thus, predetermined fuel injection control and valve opening control are executed in step ST9.

During the repetition of such a flow, when a predetermined time elapses, the actual opening degree Hr of the EGR valve 15 will soon be established.
Becomes equal to the target opening degree H ₀ (time T _{1 in} FIG. 9). This happens when the process proceeds to the next step ST73 to step ST76, in turn determines the target vane opening S to S ₁ are fully closed. Then, in step ST77, Q = Q _-1 + K × ΔQ
The target injection amount Q is determined by the following equation. Here, the correction coefficient K is a constant satisfying K ₀ <K <1, and a specific value is
It is appropriately determined in consideration of the balance between the actual feeling of acceleration and the exhaust gas performance. Further, since K> 0, the increase in the fuel injection amount is also started, and substantial acceleration is started.

Next, the contents of step ST8 will be described.
Note that, here, as shown in FIG. 9, the description will be made on the assumption that a sudden deceleration is performed at time T _B after the acceleration in order to shift to the steady running.

As shown in FIG. 8, in step ST8, first, in step ST81, Q = Q _-1 + K ₁ × ΔQ
Is determined by the following equation. Here, the correction coefficient is set to K ₁ = 1 in order to quickly decelerate. Next, in step ST82, the target vane opening S is calculated from the map M1.
Is determined to be _one of S ₁ ,... S ₄ (Sn, S _{3 in} the example of FIG. 9). As a result, the nozzle vane is operated toward the determined opening degree Sn. Further, in step ST83, the actual opening Sr of the nozzle vane is input based on the output signal of the vane opening sensor 21. Thereafter, in step ST84, the actual opening Sr of the nozzle vane is compared with the target opening S = Sn, and it is determined whether or not these are equal. Here, since the right after deceleration has nozzle vanes opening has a S _1, in normally not coincide with Sn for steady running, depending on the case, the process proceeds to step ST85, the present target EGR valve opening H Is set equal to the previous target EGR valve opening H- ₁ . This EGR valve opening by is kept H _0, the EGR valve 15 becomes the fully closed state is maintained. Q, S,
Based on the value of H, predetermined fuel injection control and valve opening control are executed in step ST9.

During the repetition of such a flow, if the predetermined time elapses, the actual opening degree Sr of the nozzle vane will soon be established.
Becomes equal to the target opening Sn (time T _{2 in} FIG. 9). In this case, the process proceeds to step ST86 after step ST84, and the target EGR valve opening degree H is set to one of H ₀ ,... H ₄ based on the map M2 (Hn, H _{1 in} the example of FIG. 9).
To decide. As a result, the EGR valve 15 is turned to the fully closed position H _0.
To the predetermined opening degree Hn.

In the diesel engine 1 as described above, when the engine load is suddenly increased such as sudden acceleration, the opening control of the movable nozzle vane is started after the opening control of the EGR valve 15 is started. There are features. In particular, since the nozzle vane closing control is started after the EGR valve 15 is fully closed, EGR cannot be performed when the exhaust pressure is increased, thereby preventing excessive EGR due to the increased exhaust pressure.
Temporary deterioration of smoke can be reliably prevented.

In the diesel engine 1, when the engine load is suddenly reduced, for example, due to sudden deceleration, the opening control of the EGR valve 15 is started after the opening control of the movable nozzle vane is started. In particular, the nozzle vane opening is set to a predetermined opening S
n, and the opening of the EGR valve 15 is started after the exhaust pressure is sufficiently reduced. Therefore, the opening of the EGR valve 15 in a state where the exhaust pressure is high is reliably prevented, and the temporary deterioration of smoke can be prevented even when the engine load suddenly decreases.

On the other hand, when the engine load suddenly increases, in the above embodiment, the opening degree of the nozzle vane is reduced after the EGR valve is closed. However, it takes some time until the nozzle vane is fully closed. The nozzle vane opening reduction start may be accelerated by utilizing this. That is, E
The opening degree of the nozzle vane is reduced before the GR valve is completely closed after the start of the valve closing and before the valve is completely closed, that is, immediately before the closing of the EGR valve is completed, for example, at a timing at which excessive exhaust pressure rise and EGR do not occur. May be started. In this way, the total time from the start of closing the EGR valve to the end of the reduction in the opening of the nozzle vane is reduced, and the control time can be reduced. Similarly, when the engine load is reduced, before the end of the nozzle vane opening start and before the end, for example, immediately before the end, the E
The opening of the GR valve may be started.

Next, another embodiment will be described.
As described above, the reason for the deterioration of smoke during the transition is that a certain amount of operation time is required to change the opening degree of the nozzle vane and the EGR valve 15. Therefore, in anticipation of this time, the timer control is performed as follows. If executed, the same effects as in the above embodiment can be exerted.

That is, specifically, in steps ST5 and ST5,
7 and ST8 are changed as shown in FIGS. 10, 11 and 12, respectively. In step ST5 shown in FIG. 10, first, in step ST51a, the controller 13
The timers T _TA and T _TB built therein are reset (cleared) to the initial value 0. The timers T _TA and T _TB are sequentially added as soon as acceleration / deceleration is determined, as will be described in detail later.
This is for knowing the elapsed time from the start of acceleration / deceleration. Thereafter, in the same manner as described above, the current target injection amount Q is determined in step ST52a, the target vane opening S is determined in step ST53a, and the target EG is determined in step ST54a.
The R valve opening H is determined. And step ST9 (FIG. 5)
Thus, a predetermined control signal is output.

In step ST7 shown in FIG. 11, first, the timer T _TB is reset in step ST71a. And after determining a target EGR valve opening H in H ₀ in step ST72a, the timer T _TA determines whether the counting proceeds to step ST73a. Previous step ST51
Since the timer has been reset at a, the timer T _TA is not counting immediately after shifting from steady running to accelerated running.
This time, the program proceeds to step ST74a, starts to count the timer T _TA. Thereafter, in step ST75a, the target vane opening degree S is fixed at the previous value S- ₁ , and in step ST7.
At 6a, the target injection amount Q is determined.

On the other hand, in the next control, step ST73 is executed.
Since the timer _TTA is counting at step a, step ST
Proceeding to 77a, a comparison is made between the timer T _TA and a predetermined set time t ₁ . Here, as shown in FIG. 9, the acceleration start (time T _A) for the up closed end of the EGR valve 15 (time T ₁₎ which requires the passage of time T ₁ -T _A from the set time t ₁ Is set to be at least equal to or slightly longer than the time T ₁ -T _A. Since T _TA ≦ t ₁ immediately after the start of acceleration, at this time, the target vane opening S and the target injection amount Q are determined through steps ST75a and ST76a in the same manner as described above. As a result, the vane opening S is fixed at the previous value S- _1, and only the closing of the EGR valve 15 is performed without changing the opening of the nozzle vane.

While repeating this control, the time t ₁ elapses, and eventually T _TA > t ₁ . This happens when the flow advances from step ST77a to step ST78a, determines a target vane opening S to S ₁ so as to perform the closing control of the nozzle vanes. Then, in step ST79a, the target injection amount Q is determined, and predetermined injection control and opening degree control are executed. At this time, since the EGR valve 15 is already fully closed, even if the nozzle vane is closed, the smoke S
M does not deteriorate.

Next, in step ST8 shown in FIG. 12, first, resets the timer T _TA at step ST81a. Then, after the target injection amount Q is determined in step ST82a, the target vane opening S is determined to be Sn in order to execute the nozzle vane opening control in step ST83a. In the next step ST84a, it is determined whether or not the timer T _TB is counting. Previous step ST71a
Since the timer T _TB has been reset in step ST
At 84a, it is determined that counting is not being performed, and the next step S
The timer T _TB starts counting at T85a. Thereafter, in step ST86a, the target EGR valve opening H is set to the previous value H _-1.
And the opening control of the nozzle vanes is started while the EGR valve opening degree H is kept fully closed.

[0045] Since the timer T _TB in step ST84a in the next control is being counted, and compares the timer T _TB and the set time t ₂ proceeds to step ST87a. Here, as shown in FIG. 9, the set time t ₂ is also set to the deceleration start (time T _B) from the open control end of the nozzle vanes (time T ₂₎ until the time T ₂ -T _B equal to or slightly longer time Is done. Since T _TB ≦ t ₂ immediately after the start of acceleration, at this time, the process proceeds to step ST86a, and the target EGR valve opening H is fixed at the previous value H ₋₁ . If T _TB > t ₂ , the target EGR valve opening H is determined to be Hn in step ST88a, whereby the EGR valve 1 after the end of the nozzle vane opening control is set.
5 can be opened.

Although the preferred embodiment of the present invention has been described above, the present invention can adopt other embodiments, and the present invention is also applicable to a mechanical injection type diesel engine.

By the way, in the diesel engine shown in FIG. 1 described so far, the EGR valve is opened and the EGR valve is opened based on the map M2 in FIG. , There is a possibility that a desired EGR rate cannot be obtained.

Therefore, the inventor of the present invention has proposed, as shown in FIG. 14, the intake passage 7 of the diesel engine 1 described with reference to FIG.
In addition, an intake throttle valve 30 is provided between the compressor 8 and the EGR valve 15, and by closing the intake throttle valve 30, a negative pressure is generated downstream of the intake throttle valve 30. Was developed to increase the Here, the opening degree of the intake throttle valve 30 is changed by adjusting the negative pressure of the negative pressure pump 31 by the negative pressure control valve 32 using a diaphragm, but is not particularly limited. The negative pressure control valve 32 is controlled by the controller 13. A sensor 33 for detecting the opening of the intake throttle valve 30 and transmitting the opening to the controller 13 is arranged near the negative pressure control valve 32. The negative pressure pumps 31, 1
7 and 11 may be shared.

The intake throttle valve 30 is connected to the controller 13
The opening degree is controlled in accordance with the value of the engine speed Ne and the target injection amount Q at the time of low rotation and low load, and the opening is controlled to I ₂ (closed) according to the values of the engine rotation speed Ne and the target injection amount Q. At medium load, it becomes I ₁ (medium closed), and at other times, it becomes I _O (open). That is, at low rotation speed and low load, as described above, the differential pressure is small, so that the intake throttle valve 30 needs to be greatly throttled. At medium rotation, medium load, the differential pressure is not so small, and the throttle of the intake throttle valve 30 is small. In other cases (during high rotation, high load, etc.), since the pressure difference is large, the intake throttle valve 30 may be opened.

Here, when shifting from the steady state to the acceleration state, the concept described with reference to FIG. 9 is that the EGR valve 15 is first closed, and therefore, as shown in FIG.
After the R valve 15 is changed from H ₄ (open) to H ₀ (closed), the movable nozzle vane is changed from S ₄ (open) to S ₁ (closed), and the intake throttle valve 30 is closed at I ₂ (closed) as shown by a broken line 34. ) To I
₀ (open). However, in this case, since the intake throttle valve 30 is opened a predetermined time after the accelerator is depressed to enter an acceleration state, the boost pressure is delayed, and the acceleration performance deteriorates.

Accordingly, the present inventor has developed a technique for opening the intake throttle valve 30 simultaneously with the closing operation of the EGR valve 15 as shown by a solid line 35 in FIG. developed. By doing so, the intake throttle valve 30 is opened immediately when the accelerator is depressed and the vehicle is accelerated, so that the boost pressure quickly rises and the acceleration performance is improved. When the intake throttle valve 30 is opened, the fresh air volume increases and E
Since the GR rate decreases, the generation of smoke during acceleration can also be suppressed.

When the EGR valve 15 is closed when shifting from the steady state to the acceleration state, the amount of exhaust gas to the turbine 9 is increased, so that the boost pressure is improved and excessive EG
The generation of smoke due to R can be suppressed. Therefore, EGR
There is no problem if the closing operation of the valve 15 and the opening operation of the intake throttle valve 30 are performed simultaneously. When the movable nozzle vane is closed, the flow rate of exhaust gas to the turbine 9 is increased and the boost pressure is increased, so that the amount of fuel can be increased and the acceleration performance is improved.

Since the response delay of the opening operation of the intake throttle valve 30 differs depending on the size of the valve, the driving method, and the position in the steady state, the EGR as shown by the solid line 35 in FIG.
Although it does not completely match the valve 15, the intake throttle valve 30
Even if the response of the EGR valve 15 is indicated by the dashed-dotted line 36 or the dashed-dotted line 37 in the case of the slow response, excessive EGR is not applied during the closing operation of the EGR valve 15. When the operation of the movable nozzle vane starts, the EGR valve 15 is fully closed (H ₀ ).
It depends only on the time

On the other hand, in contrast to the above, when shifting from the acceleration state to the steady state, the concept described with reference to FIG. 9 is to open the variable nozzle vane first.
The movable nozzle vane is moved from S ₁ (closed) to S as shown in (b).
₄ (open), the EGR valve 15 is changed from H ₀ (closed) to H ₄
(Open) and set the intake throttle valve 30 to I
Change from ₀ (open) to I ₂ (closed). However, in this case, since the EGR valve 15 is opened before the intake throttle valve 30 is completely closed, the EGR is performed in a state in which the differential pressure between the intake passage 7 and the exhaust passage 5 is small. It cannot be obtained, resulting in an increase in NOx emission. This phenomenon is particularly remarkable when the response of the closing operation of the intake throttle valve 30 is slow as indicated by the one-dot chain line 39.

Therefore, when the present inventor shifts from the acceleration state to the steady state, as shown by a solid line 40 in FIG. 16 (b), a technique for closing the intake throttle valve 30 prior to the opening operation of the EGR valve 15. Was developed. By doing so, the intake throttle valve 30
Is closed (closed) and the EGR valve 15 is opened after the differential pressure between the intake passage 7 and the exhaust passage 5 becomes sufficiently large, so that the EGR rate during the response delay period X of the EGR valve 15 surely increases. However, NOx at the time of transition can be kept low.

Even when the response delay of the intake throttle valve 30 is large as indicated by the two-dot chain line 41, the EGR valve 15 is opened after a certain pressure difference is generated.
The EGR rate can be increased as compared with the case of 8 or the dashed line 39. Therefore, the start of the opening operation of the EGR valve 15 is not affected when the closing operation of the intake throttle valve 30 ends.

The EGR rate in this transient state is:
Since the predetermined EGR rate does not exceed the predetermined EGR rate in the steady state after the transition from the acceleration state is completed, the smoke is not deteriorated.

In this embodiment, as shown in FIG. 16B, the closing operation of the intake throttle valve 30 is performed simultaneously with the start of the opening operation of the movable nozzle vane. However, even when the movable nozzle vane is opened, the rotation of the compressor 8 does not rapidly decrease due to inertia force, and there is a response delay in the decrease in the amount of air sent out by the compressor 8. If the intake throttle valve 30 is controlled to close very quickly in this state, the pressure in the intake passage 7 from the compressor 8 to the intake throttle valve 30 abnormally increases, which may cause damage. As a preventive measure, a measure such as providing a relief valve that opens in the intake passage 7 at a pressure equal to or higher than a predetermined pressure or reducing the responsiveness of the intake throttle valve 30 in the closing direction can be considered. Details are omitted.

The control of the opening degree of the EGR valve 15, the movable nozzle vane and the intake throttle valve 30 in the present embodiment is specifically performed by the controller 13 in which the maps M1 to M4 are stored as shown in FIGS. It is done.

FIG. 17 is basically the same as the flowchart shown in FIG. 5, and only the steps ST5A, ST7A, ST8A and ST9A are different due to the addition of the intake throttle valve 30. That is, in steps ST5A, ST7A, and ST8A, the target intake throttle valve opening I is newly determined in addition to the target injection amount Q, the target vane opening S, and the target EGR valve opening H. In step ST9A, control signals corresponding to the values of Q, S, H, and I determined in steps ST5A, ST7A, and ST8A are output to negative pressure control valves 12, 18, 32, and electronic governor actuator 24, respectively. I did it.

FIG. 18 showing step ST5A is basically the same as the flowchart in the steady state shown in FIG.
The only difference is that 54A is added. Step ST5
4A, based on the map M4, the target intake throttle valve opening I is calculated from the engine speed Ne and the target injection amount Q as I ₀ ,
It is determined to be either I ₁ or I ₂ . Note that I ₀ , I ₁ ,
I ₂ is generally referred to as In.

FIG. 19 showing step ST7A is basically the same as the flowchart at the time of acceleration shown in FIG.
The only difference is that the step 71 is replaced with a step ST71A. In step ST71A, the target EGR valve opening H is set to H
_It is determined to be ₀ and the target intake throttle valve opening I is determined to be _I0 . Thus, the EGR valve 15 is operated toward fully closed, and the intake throttle valve 30 is operated toward fully open.

Thereafter, steps ST72A to ST72 are executed.
The T77A, until the actual opening degree Hr of the EGR valve 15 becomes equal to the target opening degree H _0, without moving while maintaining the opening degree S of the movable nozzle vanes previous opening S _-1, the actual of the EGR valve 15 If opening Hr becomes the target opening H _0, the opening degree S of the movable nozzle vane fully closed S ₁ (see the description of the flowchart of FIG. 7).

As described above, when shifting from the steady state to the acceleration state, as shown in FIG. 21, by opening the intake throttle valve 30 simultaneously with the closing operation of the EGR valve 15, when the accelerator is depressed, the acceleration state is reached. Immediately intake throttle valve 30
Is opened, the boost pressure rises quickly, and the acceleration performance is improved. Further, when the intake throttle valve 30 is opened, the amount of fresh air increases and the EGR rate decreases, so that generation of smoke during acceleration can be suppressed. Ideally, the closing operation of the movable nozzle vane is preferably started after the closing operation of the EGR valve 15 and the opening operation of the intake throttle valve 30 are completed. This is because the closing pressure of the movable nozzle vane increases the exhaust pressure and increases the EGR rate. However, even if the opening operation of the intake throttle valve 30 is delayed due to a response delay as shown by the two-dot chain line 43 in FIG. 21, there is no possibility that excessive EGR will be applied after the EGR valve 15 is fully closed. Therefore, in this embodiment, the response delay of the intake throttle valve 30 is not managed. Needless to say, it is preferable that the response delay of the intake throttle valve 30 be faster as indicated by the dashed line 44.

FIG. 20 showing step ST8A is basically the same as the flowchart at the time of deceleration shown in FIG.
The only difference is that step 82 is replaced by step ST82A. In step ST82A, and it determines from the map M1 the target vane opening S to Sn (in FIG. 21 S _3),
The target intake throttle valve opening I is determined to be In (I _{1 in} FIG. 21) from the map M4. Accordingly, the movable nozzle vane is operated toward the target opening Sn, and at the same time, the intake throttle valve is operated toward In.

Thereafter, steps ST83A to S83
The actual opening degree Sr of the movable nozzle vane is determined by T86A.
Until the target opening Sn, the opening H of the EGR valve 15 is not moved while maintaining the previous opening H ₋₁ , and the actual opening Sr of the movable nozzle vane reaches the target opening Sn, EG
The opening of the R valve 15 is determined to be the target opening Hn (see the description of the flowchart in FIG. 8). Therefore, after the opening control of the movable nozzle vane ends, the opening of the EGR valve 15 is controlled toward the target opening Hn, and after the closing operation of the intake throttle valve 30 is started, the EGR valve 15 is opened. (See FIG. 21).

As described above, by closing the intake throttle valve 30 prior to opening the EGR valve 15 during deceleration, the intake throttle valve 30 is closed, and the pressure difference between the intake passage 7 and the exhaust passage 5 is reduced. Since the EGR valve 15 is opened after it has become sufficiently large, the EGR rate can be surely increased and NOx can be kept low. Even if the response delay of the intake throttle valve 30 is large as indicated by the two-dot chain line 42, since the EGR valve 15 is opened after a certain differential pressure is generated, E
GR rate can be increased.

[0068]

In summary, according to the present invention, excessive EGR is prevented when the engine load suddenly increases or decreases,
An excellent effect of preventing temporary deterioration of smoke is exhibited.

Further, during acceleration, by opening the intake throttle valve simultaneously with the closing operation of the EGR valve, the boost pressure rises quickly, so that the acceleration performance is improved.

Further, at the time of deceleration, by closing the intake throttle valve prior to opening the EGR valve, the EGR rate can be reliably increased, and NOx can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a diesel engine according to the present invention.

FIG. 2 is a nozzle vane opening control map.

FIG. 3 is an EGR valve opening control map.

FIG. 4 is a basic target injection amount map.

FIG. 5 is a control flowchart of the diesel engine according to the present invention.

FIG. 6 is a part of a control flowchart in a steady state.

FIG. 7 is a part of a control flowchart during acceleration.

FIG. 8 is a part of a control flowchart at the time of deceleration.

FIG. 9 is a time chart showing control contents of the diesel engine according to the present invention.

FIG. 10 is a part of a control flowchart in a steady state according to another embodiment.

FIG. 11 is a part of a control flowchart at the time of acceleration according to another embodiment.

FIG. 12 is a part of a control flowchart at the time of deceleration according to another embodiment.

FIG. 13 is a time chart showing control contents of a conventional diesel engine.

FIG. 14 is a configuration diagram showing a diesel engine according to still another embodiment.

FIG. 15 is an opening degree control map of an intake throttle valve.

FIG. 16 is a time chart showing control contents of the intake throttle valve, the EGR valve, and the movable nozzle vane.

FIG. 17 is a control flowchart of the engine.

FIG. 18 is a part of a control flowchart at the time of steady operation of the engine.

FIG. 19 is a part of a control flowchart at the time of acceleration of the engine.

FIG. 20 is a part of a control flowchart when the engine is decelerated.

FIG. 21 is a time chart showing control contents of the engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diesel engine 3 Variable capacity turbocharger 4 EGR device 13 Controller 15 EGR valve 30 Intake throttle valve

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 9/02 F02D 9/02 S 311 311 315 315B 315K 21/08 301 21/08 301B 311 311B 23/00 23/00 JF 43/00 301 43/00 301K 301N 301R F02M 25/07 550 F02M 25/07 550R 570 570P 570D

Claims (4)

[Claims] 1. A variable displacement turbocharger having a movable nozzle vane, an EGR device having an EGR valve, and the movable nozzle vane and the E valve based on an engine operating state.
A controller for controlling the opening of the GR valve,
A diesel engine comprising: a controller that starts the opening control of the movable nozzle vane after the opening control of the EGR valve is started when the engine load suddenly increases. 2. The diesel engine according to claim 1, wherein the controller starts opening control of the EGR valve after starting opening control of the movable nozzle vane when the engine load suddenly decreases. 3. The diesel engine according to claim 1, wherein the controller starts opening control of the intake throttle valve provided in the intake passage at the same time as starting the closing control of the EGR valve when the engine load suddenly increases. engine. 4. The diesel engine according to claim 1, wherein the controller starts opening control of the EGR valve after starting closing control of an intake throttle valve provided in the intake passage when the engine load suddenly decreases.