JPH11229885A - diesel engine - Google Patents

Abstract

(57) [Problem] To prevent an excessive increase in supercharging pressure when an EGR device is abnormal. SOLUTION: The diesel engine 1 according to the present invention comprises:
Variable capacity turbocharger 3 with movable nozzle vanes
An EGR device 4 having an EGR valve 15, detection means 23 for detecting an abnormality of the EGR device 4, the movable nozzle vane and the EGR based on an engine operating state.
A controller 13 for controlling the opening of the valve 15, wherein the opening of the movable nozzle vane is controlled to be smaller than the opening of the EGR valve 15 when the EGR valve 15 is opened, and Based on the detection signal of the detection means 23,
When the EGR device 4 is determined to be abnormal, the controller 13 controls the opening of the movable nozzle vane to be larger than the opening when the EGR valve 15 is opened.

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 S ₄ to be fully opened from S ₁ to be fully closed (not opening zero) As it reaches, the opening degree is gradually increased. 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 turbine speed 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 to H ₄ to be fully opened from H ₀ to the fully closed (opening zero) are sequentially increased stepwise. That is, the higher the load area, the more fresh air is needed.
Is reduced to reduce the EGR amount (EGR rate), increase the amount of fresh air (relative amount), and suppress the generation of smoke while suppressing the NOx emission level to a predetermined value (for example, a regulation value) or less. doing.

[0006] In a region where the speed is high or the load is higher than a predetermined value (for example, L> 60 (%)), the EGR valve is closed, that is, the opening degree is zero, and the EGR is stopped. As a result, only fresh air is burned, and a high output can be obtained.

[0007] Even during the engine warm-up operation, since the cylinder temperature is not burn stably even lower, the valve opening degree H is fixed to the H ₀ uniformly regardless of the engine operating condition is discontinued EGR. The controller determines whether the engine is warming up based on the value of the engine cooling water temperature Tw. If the engine cooling water temperature Tw is equal to or lower than a predetermined value (for example, 20 ° C.), the controller determines that the engine is warming up, and deactivates the EGR device. Set the valve opening H to H ₀
Fixed to. If it exceeds the predetermined value, it is determined that warm-up is over,
The EGR device is operated and the EGR is performed according to the map M2.
Execute control.

By the way, the variable displacement type turbocharger and the EG
When combined with the R device, the following problems occur. That is, a general nozzle vane opening degree control map M1
Is created without assuming EGR, that is, when the EGR device is not operated, an optimal 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.

Further, even if the map M1 is prepared on the premise of EGR, an optimum vane opening cannot be obtained when the EGR device is not operated, and the same problem occurs.

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 case where the EGR valve opening is zero and the EGR is stopped (at the time of closing), and the solid line indicates the case where the EGR valve is opened at the predetermined opening and the EGR is executed (at the time of opening). 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 this, from the graph of fuel economy, the vane opening S _A at the time of closure, the vane opening S _B at the time of opening is let each produce a fuel consumption of the lowest peak, it can be seen that the optimum vane opening. Note As a general characteristic, 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, the combustion is deteriorated, smoke It will increase sharply and fuel economy will worsen. 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. Also N
The Ox 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 the 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.

Accordingly, the present applicant has previously made a proposal for solving this problem in Japanese Patent Application No. 8-328637. This is to control the opening degree of the nozzle vane when the EGR device is operated to be smaller than the opening amount when the EGR device is not operated. According to FIG. 6, since S _B <S _A , by executing the nozzle vane opening control as described above based on this result, an optimum nozzle vane opening can always be obtained regardless of the operation or non-operation of the EGR device. Further, it is possible to prevent deterioration of fuel efficiency.

That is, during operation at the optimum nozzle vane opening when the EGR device is not operating, the EGR device is operated,
Suppose that R is executed. Then, the proportion of the fresh air amount of the intake is reduced by the amount of the EGR gas mixed into the intake. Also, because part of the exhaust gas is bypassed to the intake air, the energy of the exhaust gas is reduced, thereby reducing the workload of the turbine,
The supercharging pressure decreases accordingly. For these reasons, the amount of fresh air tends to be short, and problems such as an increase in smoke and deterioration in fuel efficiency occur.

Therefore, when the EGR device is operated or the EGR valve is opened, the gas flow rate supplied to the turbine is increased by reducing the opening degree of the nozzle vane, the work amount of the turbine is increased, and the same supercharging pressure can be maintained. In addition, problems such as an increase in smoke and deterioration in fuel efficiency due to a shortage of fresh air can be solved.

[0016]

The prior application has the following problems. That is, if an abnormality occurs in the EGR device and the nozzle vane opening is narrowed without opening the EGR valve regardless of the EGR execution region, the supercharging pressure becomes excessive, and the intake pipe or the intercooler downstream of the compressor becomes excessive. And the like, and secondary damage due to an excessive rise in the engine cylinder pressure. As such an abnormality of the EGR device, it is conceivable that the EGR valve is stuck or wiring or piping is disconnected.

[0017]

SUMMARY OF THE INVENTION A diesel engine according to the present invention includes a variable displacement turbocharger having a movable nozzle vane, an EGR device having an EGR valve, and a detection device for detecting an abnormality in the EGR device. Means for controlling the degree of opening of the movable nozzle vane and the EGR valve based on the operating state of the engine.
When the R valve is opened, the opening of the movable nozzle vane is adjusted to the EG.
When the opening degree of the R valve is controlled to be smaller than the opening degree when the R valve is closed, and the EGR device is determined to be abnormal based on the detection signal of the detecting means, the opening degree of the movable nozzle vane is set to the E degree.
And a controller for controlling the GR valve to a larger opening than the opening when the GR valve is opened.

According to this, when the EGR device is abnormal, the nozzle vane opening is increased, so that an excessive increase in the supercharging pressure is prevented, and primary and secondary damage can be prevented.

It is preferable that when the controller determines that the EGR device is abnormal, the opening of the movable nozzle vane is controlled to the opening when the EGR valve is closed. The detecting means may be a temperature sensor provided downstream of the EGR valve, and the controller may determine that the EGR device is abnormal when a value detected by the temperature sensor is less than a preset value stored in advance. Is preferred. Further, it is preferable that the set value changes in accordance with the engine operating state.

[0020]

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 middle of the exhaust passage 5 and a compressor 8 provided in the middle of the intake passage 7. A nozzle vane is provided so that the amount of exhaust gas supplied to the turbine wheel 9 can be changed as appropriate.

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, 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.

Here, the EGR passage 14 takes out a part of the exhaust gas (EGR gas) from the exhaust passage 5 on the upstream side of the turbine 6 and transfers the EGR gas downstream of the compressor 8 in the intake passage 7 in the direction indicated by the arrow. It is designed to be sent. In the EGR passage 14, downstream of the EGR valve 15 in the EGR gas flow direction, a detecting means for detecting an abnormality of the EGR device 4, that is, a temperature sensor 23 is provided. The temperature sensor 23 detects E that has passed through the EGR valve 15.
The temperature of the GR gas is detected, and an output signal corresponding to the detected temperature is sent to 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.

Also, the controller 13 has the functions shown in FIGS.
The maps M1, M2, and M3 shown in FIG. 5 are stored in advance. These maps M1, M2, and M3 are created through actual machine tests and the like, and each optimum value according to the engine speed Ne and the engine load L is input. 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 or the EGR valve 15 is closed.
, Depending on the value of the engine speed Ne and the engine load L, it is adapted to be increased sequentially four steps from S ₁ to be fully closed (not opening zero) to S ₄ which is a fully open.
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 fully closed according to the values of the engine speed Ne and the engine load L. H from full opening (H ₀ )
Up to ₄ are sequentially increased in 5 steps. The number of stages is not limited to these.

In particular, a map M3 shown in FIG. 5 is a nozzle vane opening control map when the EGR device 4 is operated or when the EGR valve 15 is opened. Also in this map M
1 similar to, the nozzle vane opening degree S is depending on the value of the engine speed Ne and the engine load L, 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), the boundary of each vane opening S ₁ to S ₄ is map M1 Is lowered to the lower load side from the boundary (indicated by the dashed line c) at
That is, for the same engine speed Ne and the same engine load L, a region A (indicated by hatching) in which the nozzle vane opening S is one step smaller than in the case of the map M1 is formed.

In accordance with these maps M1, M2, 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 has been 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 in the operating state.
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. The engine cooling water temperature Tw is an example.
The operating conditions of the GR device 4 may be determined based on other factors.

If it is determined in step ST2 that Tw> T, the process proceeds to step ST3, where EG is determined by the map M2.
The R valve opening H is determined. Then, in step ST5, a control signal (duty signal) corresponding to the opening H
Is output to the negative pressure control valve 18. As a result, the EGR valve 1
The opening of No. 5 is controlled to the set opening H.

On the other hand, if it is determined in step ST2 that Tw ≦ T, the process proceeds to step ST4, and the EGR valve opening degree H is determined to be H ₀ (= 0) which is fully closed. When this happens, step S
Even if the process proceeds to T5, no control signal is output to the negative pressure control valve 18, whereby the EGR valve 15 is completely closed, and E
The GR passage 14 is closed and EGR is not performed.

Next, it is determined whether H ≠ H ₀ or not the process proceeds to step ST6. The process proceeds to step ST7 when the H ≠ H _0, enter the EGR gas temperature Te based on the output signal of the temperature sensor 23. Next, in step ST8, it is determined whether or not the EGR gas temperature Te is equal to or higher than a preset value Tj stored in advance. Here, similarly to the maps M1 to M3, the set value Tj is given in the form of a map corresponding to the engine operating state, that is, the engine speed Ne and the engine load L, and is a value that changes according to the engine operating state. .

Here, when Te ≧ Tj, the EGR valve 15 is opened to an appropriate opening degree H in a state where the EGR gas is flowing properly, that is, in the current engine operating state, and an appropriate amount of the EGR gas is released. It passes through the valve 15 and determines that the EGR device 4 is operating normally. In this case, the process proceeds to step ST9, where the nozzle vane opening S is determined from the engine speed Ne and the engine load L according to the map M3. In step ST11, a control signal (duty signal) corresponding to the opening S is output to the negative pressure control valve 12. As a result, the nozzle vane opening is controlled to the optimal opening S at the time of EGR execution based on the map M3.

On the other hand, when H = H ₀ in step ST6, it means that the EGR valve 15 is closed and EGR is stopped. Therefore, in step ST10, the nozzle vane opening S is determined from the map M1 and then in step ST11. The nozzle vane is operated according to the opening degree S. As a result, the nozzle vane opening is controlled to the optimum opening S when EGR is stopped based on the map M1.

[0035] In particular, when the Te <Tj in step ST8, despite has issued the open command to the EGR valve 15 at H ≠ H _0, since a state in which EGR gas is not flowing properly, EGR valve 15 Is not reached or has not been opened at all, that is, the EGR device 4 is in an abnormal state, and the nozzle vane opening S is determined from the map M1 in step ST10. Then, in step ST11, the nozzle vane is operated in accordance with the opening degree S. In this way, the nozzle vane opening is controlled to be larger than the opening when the EGR valve is opened (when EGR is performed), particularly in the area A of the map M3.

As described above, the nozzle vane opening control is executed based on different maps M1 and M3 when the EGR valve 15 is closed and when it is opened. And EGR valve 1
The nozzle vane opening at the time of the EGR execution is controlled by controlling the nozzle vane opening at the time of opening of the EGR valve 15 to be smaller than the opening at the time of closing the EGR valve 15. The opening degree S can be optimized, and smoke and deterioration of fuel efficiency can be prevented. As a result, the EGR valve 15
The optimal vane opening can be obtained even when the
Opening / closing of the EGR valve 15 or operation of the EGR device 4
Optimal nozzle vane opening control is always possible regardless of non-operation. Of course, the effect of reducing NOx is also exerted by performing EGR.

On the other hand, here, when it is determined that the EGR device 4 is abnormal, the nozzle vane opening S is controlled based on the map M1. That is, particularly in the engine operating state corresponding to the area A of the map M3, the nozzle vane opening S
The opening is controlled to be larger than the opening when the R valve is opened. In this way, when the EGR device 4 is abnormal, the opening degree S of the nozzle vane is restricted and the supercharging pressure does not excessively increase.
It is possible to prevent primary damage such as an intake pipe or an intercooler (omitted in the present embodiment) downstream of the compressor and secondary damage due to an excessive increase in the engine cylinder pressure.

Here, when the EGR device 4 is abnormal, the map M
The use of 1 is for sharing the map and simplifying the control. However, as long as the nozzle vane opening S can be controlled to a large opening, another map may be used or the map M3 may be used.
Alternatively, a predetermined value may be added to the opening value obtained in step (1).

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can adopt various other embodiments. For example, a supercharging pressure sensor, an O ₂ sensor, an intake air amount sensor, an EGR valve opening degree sensor, or the like may be used as the detection means, and the abnormality of the EGR device may be determined based on the detected values.

[0040]

In summary, according to the present invention, an excellent effect that an excessive increase in the supercharging pressure can be prevented when an EGR device is abnormal is exhibited.

[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 performing opening control of a nozzle vane and an EGR valve.

FIG. 3 is a nozzle vane opening control map when the EGR valve is closed.

FIG. 4 is an EGR valve opening control map.

FIG. 5 is a nozzle vane opening control map when the EGR valve is opened.

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 23 temperature sensor L engine load Ne engine speed S nozzle vane opening Te EGR gas temperature (detected value by temperature sensor) Tj set value

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁶ Identification code FI F02D 43/00 301 F02D 43/00 301Y 301R 301N F02M 25/07 550 F02M 25/07 550L

Claims (4)

[Claims] A variable capacity turbocharger having a movable nozzle vane; an EGR device having an EGR valve;
Detecting means for detecting an abnormality of the R device; and the movable nozzle vane and the EGR based on an engine operating state.
A controller for controlling the opening degree of the valve, wherein the opening degree of the movable nozzle vane is controlled to be smaller than the opening degree of the EGR valve when the EGR valve is opened, and A diesel engine, comprising: a controller configured to control the opening of the movable nozzle vane to be larger than the opening of the EGR valve when the EGR device is determined to be abnormal based on the detection signal. 2. The diesel engine according to claim 1, wherein the controller controls the opening of the movable nozzle vane to the opening when the EGR valve is closed when the controller determines that the EGR device is abnormal. 3. The temperature control device according to claim 1, wherein the detection unit is a temperature sensor provided downstream of the EGR valve.
The EGR device is determined to be abnormal when a value detected by the temperature sensor is less than a preset value stored in advance.
The diesel engine as described. 4. The diesel engine according to claim 3, wherein said set value changes according to an engine operating state.