JPH10169458A - Diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always obtain optimum nozzle vane opening regardless of the operating/nonoperating state of an EGR device so as to prevent worsening of smoke and fuel consumption by controlling the opening of a movable nozzle vane at the operating time of the EGR device to smaller opening than the opening at the nonoperating time of the EGR device. SOLUTION: Output signals of sensors 19-21 for respectively detecting engine speed, engine load and cooling water temperature are inputted to a controller 13, and whether the cooling water temperature Tw is higher than the specified value T is first discriminated. In case of Tw>T, it is so judged that an engine is after warming up and an EGR device 4 is in an operating state. In case of Tw<=T, it is so judged that the engine is in process of warming up and the EGR device 4 is in a nonoperating state. In case of Tw>T, nozzle vane opening S and EGR valve opening H are respectively determined by a map, and control signals corresponding to these opening S, H are outputted to negtive pressure control valves 12, 18 so as to operate the opening of a nozzle vane and an EGR valve 15 to the optimum value.

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 There is known a variable displacement turbocharger having a movable nozzle vane at a turbine inlet and capable of changing a supercharging pressure (compressor discharge pressure) by controlling an opening degree of the nozzle vane. As described in Japanese Patent Application Laid-Open No. 61-237831, etc., a plurality of nozzle vanes are connected by an interlocking mechanism, and the angle of the nozzle vanes is changed by inputting an actuator driving force to the interlocking mechanism. Is to change. The actuator is operated based on a control signal from a controller which is an electronic control unit. The controller, nozzle vanes opening control map as shown in FIG. 3 (map M1) are advance in the memory, the controller determines a nozzle vane opening degree S ₁ to S ₄ in accordance with the map M1 from the engine speed Ne and the engine load L Then, a control signal is output such that the nozzle vane opening degree is obtained.

[0003] In map M1, the vane opening S is changed in four steps _{S 1, S 2, S 3} , S 4, the opening degree as the result in S ₄ to be fully opened from S ₁ to be fully closed sequentially It is increased stepwise. That is, in the region where the load is low and the load is high, the intake air amount tends to be relatively short with respect to the fuel injection amount. Therefore, by reducing the vane opening S (S = S ₁ ), the exhaust gas speed at the turbine inlet is reduced. , The number of revolutions is increased, and the supercharging pressure is increased to increase the intake air amount. On the other hand, in a high-speed region where the intake air amount is sufficient or a low-load region where the fuel injection amount is small, the exhaust pressure is reduced by increasing the vane opening S (S = S ₄ ), thereby reducing the pumping loss.

[0004] On the other hand, by circulating a part of the exhaust gas into the intake air, the combustion temperature is reduced and the EGR which suppresses the generation of NOx is suppressed.
Devices are also well known. In this system, 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 controls the EGR valve opening degree H ₀ to the EGR valve opening degree control map (map M2) as shown in FIG.
H ₄ is determined and a control signal is output.

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 a high-speed or high-load region (for example, L> 60 (%)) exceeding a predetermined value, the valve opening H is set to H ₀ (= 0) at which the valve is completely closed, and the EGR device is not operated. EGR is stopped in the same state as the above. As a result, only fresh air is burned, and a high output can be obtained. On the other hand, during engine warm-up operation, since the cylinder temperature is not burning stable low, the valve opening degree H is fixed to the H ₀ uniformly regardless of the engine operating condition is discontinued EGR. The warm-up state of the engine is determined based on the value of the engine cooling water temperature Tw. If the engine cooling water temperature Tw is lower than a predetermined value (for example, 20 ° C.), the controller deactivates the EGR device and fixes the valve opening H to H _0. , If it exceeds a predetermined value, the map M2
The EGR control is executed according to the following.

[0007]

When the variable displacement turbocharger and the EGR device are combined, the following problems occur. That is, the general nozzle vane opening control map M1 is created without assuming EGR. That is, when the EGR device is not operated, the optimum vane opening can be determined.
Therefore, when the EGR device is in the operating state, the optimum vane opening cannot be obtained in the map M1, and even if the vane opening control based on this is executed, smoke and fuel consumption increase. I will.

[0008] Even if the map M1 is created on the premise of EGR, an optimum vane opening cannot be obtained when the EGR device is not operated, which causes a similar problem.

This will be described in detail below. FIG.
At a constant engine speed and engine load
When the nozzle vane opening is changed, the boost pressure, exhaust pressure,
5 is a graph showing how the fuel efficiency, A / F (air-fuel ratio), smoke level, and NOx level change. In the figure, the dotted line indicates the non-operation of the EGR device, and the solid line indicates the operation thereof. In the smoke graph, the level d indicates the level of the deterioration limit. In the graph of A / F, level a indicates the A / F level at the smoke deterioration limit.

According to the graph, the fuel consumption graph shows that the vane opening S _A when not in operation and the vane opening S _B when in operation respectively produce the lowest peak fuel economy, and that the vane opening is the optimum vane opening. . Also, in each case inoperative or during operation, when a large vane opening from the optimum vane opening S _A or S _B, also decreases the excess air ratio by a decrease in the supercharging pressure, i.e. the intake air amount is insufficient, Combustion worsens, smoke increases sharply, and fuel economy worsens. If the opening degree of the vane is reduced, the supercharging pressure and the excess air ratio increase, so that the smoke is suppressed to a predetermined level d or less. However, the exhaust pressure increases, so that the fuel efficiency deteriorates. It should be noted that the NOx level does not change much with the change in the vane opening, but the larger the vane opening and the lower the supercharging pressure, the lower the NOx level due to the lower heat release rate during combustion. .

As described above, the optimum nozzle vane opening differs between when the EGR device is not operating and when it is operating. Therefore, even when the vane opening control is performed based on a map on the assumption that the EGR device is not operating, Even if the reverse is performed, the optimum vane opening cannot be obtained, and the above-described problem occurs.

[0012]

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 controlling the opening of the movable nozzle vane to be smaller than the opening when the EGR device is not operating when the EGR device is operating. Things.

According to the graph, the optimum nozzle vane opening degree S _B during EGR device actuated, it is seen that optimum nozzle vane opening degree S _A smaller value at the time of non-operation. Therefore, by executing the nozzle vane opening control as described above based on this result, an optimal nozzle vane opening can always be obtained regardless of the operation / non-operation of the EGR device, and smoke and deterioration of fuel efficiency can be prevented. .

The controller may determine whether the EGR device is activated or deactivated based on the engine coolant temperature.

[0015]

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

FIG. 1 is a configuration 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 exhaust passage 5 and a compressor 8 provided in the intake passage 7. Nozzle vanes are provided to appropriately restrict the amount of exhaust gas supplied 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 connecting the exhaust passage 5 and the intake passage 7, and an EGR passage 14.
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 engine operating state 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 engine load L is detected based on the output signal of 0, and the coolant temperature Tw is detected based on the output signal of the coolant temperature sensor 21.

3 and FIG.
The maps M1, M2, and M3 shown in FIG. 5 are stored in advance. These maps M1, M2 and M3 are created in advance through actual machine tests and the like. As described above, the map M1 shown in FIG. 3 is a nozzle vane opening control map when the EGR device 4 is not operated. In this map, the nozzle vane opening S depends on the values of the engine speed Ne and the engine load L. Te, S to be fully open from S ₁ to be fully closed
Up to _four are sequentially increased in four stages. A map M2 shown in FIG. 4 is an EGR valve opening control map of the EGR device 4, in which the opening H of the EGR valve 15 is set.
, Depending on the value of the engine speed Ne and the engine load L, it is adapted to be increased sequentially out until H ₄ to be fully opened from H ₀ to the fully closed.

In particular, a map M3 shown in FIG. 5 is a nozzle vane opening degree control map when the EGR device 4 operates. Similarly with the map M1 in this nozzle vane opening degree S is depending on the value of the engine speed Ne and the engine load L, it is increased sequentially 4 stages to S ₄ which is a fully open from S ₁ to be fully closed. However, in the map M3, the EGR region serving as a valve opening H ₁ to H ₄ map M2 (the region surrounded by the broken line b in FIG. 5), each vane opening S ₁ to S ₄
Is reduced to a lower load side than the boundary (indicated by a broken line c) in the map M1, that is, for the same engine speed Ne and the same engine load L, the nozzle vane opening S is one step smaller than in the map M1. Is formed (indicated by hatching).

In accordance with the maps M1, M2, and M3, the controller 13 executes the vane opening control and the EGR valve opening control as follows in accordance with the control flowchart shown in FIG.

First, in step ST1, the sensor 1
Based on the output signals of 9, 20, and 21, the engine speed N
e, input each value of the engine load L and the cooling water temperature Tw. Next, at step ST2, it is determined whether or not the cooling water temperature Tw is higher than a predetermined value T. If Tw> T, it is determined that the engine is warmed up, and it is determined that the EGR device 4 is operating. If Tw ≦ T, it is determined that the engine is warming up, and the EGR device 4 is not operating.
That is, it is determined that it is in a non-operation state. That is, in this step ST2, the controller 13 determines the operation / non-operation of the EGR device 4 based on the engine cooling water temperature Tw.

If it is determined in step ST2 that Tw> T, the process proceeds to step ST3, where the nozzle vane opening S is determined from the map M3. And the next step ST4
Determines the EGR valve opening degree H from the map M2. Then, in the next step ST5, these opening degrees S, H
A control signal (duty signal) corresponding to the negative pressure control valve 1
2, 18 to thereby output the nozzle vanes and EG
The opening of the R valve 15 is operated to the determined optimum values S and H, respectively.

On the other hand, if it is determined in step ST2 that Tw ≦ T, the process proceeds to step ST6, where the EGR valve opening H
Is set to H ₀ (= 0) which is fully closed. Next, in step ST7, the nozzle vane opening degree S is determined based on the map M1. Thereafter, in step ST5, a control signal corresponding to the nozzle vane opening S is output only to the negative pressure control valve 12, and only the nozzle vane opening control is executed. Since H = H ₀ , no control signal is output to the negative pressure control valve 18, whereby the EGR valve 15 is completely closed, the EGR passage 14 is completely closed, and EGR is not executed.

In step ST4, H is added to the map M2.
= H ₀ , and in this region, the state is the same as in the non-operating state. However, even in this case, H can change, so it is included in the operating state.

In such a configuration, the EGR device 4
Is characterized in that the nozzle vane opening degree control is executed based on different maps M1 and M3 between when not operating and when operating. Here the map M3 is prepared as described above, in the graph shown in FIG. 6, the optimum nozzle vane opening degree S _B during EGR device actuated, is optimum nozzle vane opening degree S _A smaller value at the time of non-operation Based on Thus, by controlling the opening degree S of the nozzle vane to be smaller than the opening degree S when the EGR device 4 is not operating when the EGR device 4 is operated, specifically, the area A of the map M3 is changed. With the formation, the nozzle vane opening degree S at the time of the operation can be optimized, and the smoke and the fuel consumption can be prevented from being deteriorated at the time of the operation. As a result, even when the EGR device 4 is not operating, an optimum vane opening can be obtained, and as a result, optimal nozzle vane opening control can always be performed regardless of whether the EGR device 4 is operating or not. Of course, by performing EGR, NOx
The effect of the reduction is also exhibited.

It is considered that S _B <S _A in FIG. 6 is based on the following reason. That is, the EGR valve 15
Is opened, the exhaust gas escapes and the exhaust pressure drops, which is substantially the same as the vane opening is increased, and it is considered that each characteristic value shifts to the small vane opening side by that much. Therefore, if the vane opening is reduced by that amount during operation, the amount of reduction in exhaust pressure is compensated, and equivalent characteristics can be obtained.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can adopt various other embodiments.

[0030]

In summary, according to the present invention, an excellent nozzle vane opening can be always obtained irrespective of the operation or non-operation of the EGR device, and an excellent effect of preventing deterioration of smoke and fuel consumption can be achieved.

[Brief description of the drawings]

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

FIG. 2 is a control flowchart for controlling the opening of a nozzle vane and an EGR valve.

FIG. 3 is a nozzle vane opening control map when the EGR device is not operated.

FIG. 4 is an EGR valve opening control map.

FIG. 5 is a nozzle vane opening control map when the EGR device is operating.

FIG. 6 is a graph showing a relationship between a nozzle vane opening and each characteristic value.

[Explanation of symbols]

 Reference Signs List 1 diesel engine 3 variable capacity turbocharger 4 EGR device 13 controller 15 EGR valve S nozzle vane opening Tw engine cooling water temperature

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 43/00 301 F02D 43/00 301R 301N F02M 25/07 570 F02M 25/07 570D 570J 570P

Claims (2)

[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 for controlling the opening of the movable nozzle vane to be smaller than the opening of the EGR device when the EGR device is not operating when the EGR device is operating. 2. The diesel engine according to claim 1, wherein the controller determines whether to activate or deactivate the EGR device based on an engine coolant temperature.