JPH08303309A - Egr device of diesel engine with supercharger - Google Patents

Abstract

PURPOSE: To prevent the suction of excessive EGR gas into a cylinder at the time of start and reduce the generation of exhaust air smoke accurately by providing a bypass valve in a bypass passage which leads gas in a collector into an exhaust system. CONSTITUTION: In a collector 38, a bypass passage 50 which leads gas in the collector 38 into an exhaust system is opened at a downstream end, a bypass valve 51 is provided in an opening, and the downstream of the bypass passage 50 is connected with an exhaust passage 32 at a lower end of an exhaust turbine 42 of a turbo charger 40. When target EGR rate is changed greatly at the time of operation when target EGR rate is reduced rapidly at the time of rapid start from idle operation, a suction throttle valve 34 and an EGR valve 36 are controlled to required degree of opening. A bypass valve 51 in the bypass passage 50 is opened fully based on change speed of the target EGR rate, and gas in the collector 38 flows out into the exhaust passage 32 on the downstream of the exhaust turbine 42 of the turbo charger 40 from the bypass passage 50. Consequently, it is possible to reduce the generation of exhaust air smoke due to excessive EGR gas accurately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR device (exhaust gas recirculation device) for a diesel engine with a supercharger.

[0002]

2. Description of the Related Art A diesel engine of a vehicle employs an EGR device for recirculating a part of exhaust gas to an intake system in order to reduce NOx in the exhaust gas.

A conventional diesel engine EGR device is shown, for example, in FIG. 21, which has an EGR valve 4 in an EGR passage 3 for guiding exhaust gas (EGR gas) from an exhaust passage 2 of an engine 1, and an EGR passage 3 in the EGR passage 3. The intake throttle valve 6 is provided in the intake passage 5 (intake passage) upstream of the opening, and the control device 7 has predetermined data. The EGR valve is set according to the engine speed and the accelerator opening (load). 4. The intake throttle valve 6 is driven via step motors 8 and 9, respectively, to control the EGR.

Further, the intake compressor 11 of the turbocharger 10 is provided in the intake passage 5 upstream of the intake throttle valve 6 and the exhaust turbine 12 is provided in the exhaust passage 2 for supercharging.

In the figure, 13 is an exhaust escape passage that bypasses the exhaust turbine 12, and 14 and 15 are wastegate valves and step motors. 16 is an intake valve, 17 is an exhaust valve,
Reference numeral 18 is a fuel injection valve, and 19 is a piston, which represents one cylinder portion.

The controller 7 obtains the fuel injection amount from the map as shown in FIG. 22 according to the engine speed and the accelerator opening, and as shown in FIG. 23 according to the fuel injection amount and the engine speed. The target EGR rate (EGR amount / fresh air amount) is obtained from the map, and the EGR valve 4 opening and the intake throttle valve 6 opening are controlled to obtain the target EGR rate (JP-A-61-21).
5426, etc.).

[0007]

However, in such a conventional EGR device, the gas sucked into the cylinder, that is, the EGR rate inside the collector (intake manifold) 20 is determined by the intake throttle valve 6 and the EGR valve 4. Since it is controlled only by means of, the delay due to the capacity of the collector 20 (delay of gas flow) causes poor responsiveness at the time of reduction control of the EGR rate.

Therefore, when performing rapid acceleration from idle, the excess air ratio is insufficient due to the EGR gas that is lately sucked from the collector 20, which causes deterioration of combustion, and exhaust smoke (black smoke) is likely to occur. . In order to suppress the generation of smoke, the fuel injection amount is limited, and as a result, the output is reduced. There was a problem.

As an example of this, consider the case of leaving the vehicle from the waiting for a traffic light, while the red light is stopped, the accelerator opening is 0 °,
The engine speed is idling (about 800 rpm), at which time the fuel injection amount is about 2.5 [mg / st] and EGR
The rate is the maximum of 76% (Figs. 22 and 23).

When the signal turns blue from this state and the accelerator is gradually opened at the time of starting, the fuel injection amount is as shown in FIG.
23, the EGR rate also gradually changes as shown by the curve A in FIG. Therefore, in this case, since the EGR rate does not change suddenly, the problem due to the response delay of the EGR rate does not occur only by controlling the EGR valve and the intake throttle valve.

On the other hand, when the accelerator is fully opened at the time of starting, the fuel injection amount becomes about 40 [mg / st] when the engine speed is near idle, which decreases as the engine speed increases. The minimum is about 25 [mg / st]. The EGR rate becomes 0% in the region where the fuel injection amount exceeds about 17 [mg / st].

That is, although the EGR rate is suddenly changed from 76% to 0% at the same time when the accelerator is fully opened, it is possible to cope with the intake of the EGR gas with a delay from the collector 20 only by controlling the EGR valve and the intake throttle valve. As a result, the aforementioned problem occurs due to the response delay of the EGR rate.

The present invention solves these problems,
The purpose is to obtain good engine performance and exhaust performance.

[0014]

As shown in FIG. 24, the first aspect of the present invention is such that an intake throttle valve 101 and a supercharger 102 are provided in an intake introduction passage 100, and an EGR valve 1 is provided in an EGR passage 103.
04, the intake throttle valve drive unit 105 that drives the intake throttle valve 101, the EGR valve drive unit 106 that drives the EGR valve 104, and the fuel injection of the fuel injection valve 107 based on the engine speed and the engine load. Means 108 for setting the amount, means 109 for setting the target EGR rate based on the fuel injection amount and engine speed, and means for calculating the target EGR valve opening and the target intake throttle valve opening based on the target EGR rate. 110, an EGR valve opening control unit 111 that controls the EGR valve drive unit 106 so that the actual EGR valve opening matches the target EGR valve opening,
An intake throttle valve opening control unit 112 that controls the intake throttle valve driving unit 105 to match the actual intake throttle valve opening with the actual intake throttle valve opening is provided. In a diesel engine with a supercharger, which mixes the EGR gas flowing in from the passage 103 with the collector 113 and supplies it to the cylinder, the collector 1
A bypass passage 114 for guiding the gas in the exhaust system 13 to the exhaust system, a bypass valve drive unit 116 for driving a bypass valve 115 provided in the bypass passage 114, and a target bypass valve opening based on the changing speed of the target EGR rate. Means 117 for calculating the degree
And a bypass valve opening control unit 118 that controls the bypass valve drive unit 116 so that the actual bypass valve opening matches the target bypass valve opening.

As shown in FIG. 25, the second aspect of the present invention is such that an intake throttle valve 101 and a supercharger 102 are provided in an intake introduction passage 100, an EGR valve 104 is provided in an EGR passage 103, and an intake throttle valve is provided. An intake throttle valve drive unit 105 for driving 101,
An EGR valve drive unit 106 that drives the EGR valve 104, a unit 108 that sets the fuel injection amount of the fuel injection valve 107 based on the engine speed and the engine load, and a target EGR rate based on the fuel injection amount and the engine speed. Means 109 for setting the target E
Means 110 for calculating the target EGR valve opening and the target intake throttle valve opening based on the GR rate, and the actual EG for the target EGR valve opening.
An EGR valve opening control unit 111 that controls the EGR valve driving unit 106 to match the R valve opening, and an intake throttle valve driving unit that matches the actual intake throttle opening to the target intake throttle opening. Intake throttle valve opening control section 112 for controlling 105
And the EG and the gas flowing from the intake introduction passage 100.
The EGR gas flowing from the R passage 103 and the collector 11
In a diesel engine with a supercharger that mixes through 3 and supplies the mixed gas to a cylinder, a bypass passage 114 for guiding the gas in the collector 113 to an exhaust system, and a bypass passage 114
A bypass valve drive unit 116 for driving the bypass valve 115 installed in the vehicle, a unit 117 for calculating a target bypass valve opening based on the change speed of the target EGR rate, and an actual bypass valve opening for the target bypass valve opening. Bypass valve opening control unit 11 that controls the bypass valve drive unit 116 so as to match the degrees
8, a means 119 for delaying the injection timing of the fuel injection valve 107 by a predetermined amount so as to prolong the ignition delay period of the injected fuel at a high EGR rate, and a means 120 for simultaneously enhancing the swirl generated in the combustion chamber. And,

In a third aspect of the invention, the supercharger 102 is a supercharger that is supercharged by driving an engine.

In a fourth aspect of the present invention, the supercharger 102 is a turbocharger which is supercharged by driving the exhaust of an engine, and a bypass flow passage 114 connects a collector 113 to the exhaust side downstream of the turbocharger.

In a fifth aspect of the invention, the bypass valve 115 is
It is controlled in two positions: fully closed and fully open.

In a sixth aspect of the invention, the intake throttle valve 101 is
It is controlled to several positions including the fully open position.

[0020]

In the first aspect of the invention, the target E is set based on the engine speed and the fuel injection amount (set based on the engine speed and the engine load).
The GR rate is set and the opening degree of the EGR valve and the opening degree of the intake throttle valve are controlled so that the target EGR rate is achieved. However, when the target EGR rate sharply decreases, it is calculated based on the changing speed of the target EGR rate. The bypass valve is opened to a different opening, and the gas in the collector is discharged from the bypass passage to the exhaust system.

Therefore, during the operation for rapidly reducing the EGR rate, the EGR gas flowing into the collector is prevented from being excessively sucked into the cylinder, and proper EGR is performed.

In the second aspect of the invention, when the target EGR rate suddenly decreases, the bypass valve is opened to the opening degree obtained based on the changing speed of the target EGR rate, so that proper EGR is performed and the high EGR rate is high. In the case of the EGR rate, the injection timing of the fuel injection valve is delayed by a predetermined amount, and at the same time the swirl generated in the combustion chamber is strengthened.

That is, if the EGR rate is high, NOx may be greatly reduced, but smoke may increase, but at this time, the swirl of the combustion chamber is strengthened and the injection timing of the fuel injection valve is delayed to delay ignition. When the period is lengthened, mixing of fuel and air is promoted, and most of the combustion is performed by so-called premixed combustion in which smoke is unlikely to occur.

In the third aspect of the invention, since supercharging is performed by the engine-driven supercharger, when the bypass valve in the bypass passage is opened, the gas in the collector is smoothly discharged into the exhaust system.

In the fourth aspect of the present invention, supercharging is performed by the turbocharger driven by the exhaust gas of the engine, and the bypass passage is connected downstream of the exhaust side of the turbocharger. Therefore, when the bypass valve of the bypass passage is opened, The gas in the collector is smoothly discharged into the exhaust system.

In the fifth aspect of the invention, the bypass valve is fully opened so that the gas in the collector is sufficiently discharged.

In the sixth aspect of the invention, the EGR rate control is performed by controlling the intake throttle valve to several positions including the fully open position.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 30 is an engine body, 31
Is an intake passage, 32 is an exhaust passage, and 33 is an EGR passage for guiding EGR gas to the intake system.

The intake throttle valve 34 provided in the intake introduction passage 31 is connected to and driven by the intake throttle valve driving step motor 35.

EGR valve 36 installed in EGR passage 33
Is connected to and driven by the EGR valve driving step motor 37.

Gas (fresh air) from the intake introduction passage 31 and E
The EGR gas from the GR passage 33 is mixed in the collector 38 and sucked into each cylinder.

In the turbocharger 40, the intake compressor 41 is installed in the intake introduction passage 31 upstream of the intake throttle valve 34, and the exhaust turbine 42 is installed in the exhaust passage 32 downstream of the opening of the EGR passage 33.

A wastegate valve 45 connected to a driving step motor 44 is interposed in the exhaust escape passage 43 of the exhaust turbine 42, and the wastegate valve 45 is provided in a high rotation region of the engine so that a part of the exhaust gas is exhausted. The opening operation is performed so as to escape to the exhaust gas escape passage 43.

Reference numeral 46 is an intake valve, 47 is an exhaust valve, 48 is a fuel injection valve, and 49 is a piston, which represents one cylinder portion.

A bypass passage 50 for guiding the gas in the collector 38 to the exhaust system is opened at the downstream end of the collector 38, and the downstream of the bypass passage 50 is in the exhaust passage 32 downstream of the exhaust turbine 42 of the turbocharger 40. Connected.

A bypass valve 51 is provided in the opening of the bypass flow passage 50, and the bypass valve 51 is connected to and driven by a bypass valve driving step motor 52.

Signals from a rotation speed sensor 53 for detecting the engine speed and crank angle and an accelerator opening sensor 54 for detecting the accelerator opening (engine load) are input to a control unit 55.

The control unit 55 is shown in FIG.
2. A fuel injection amount map and a target EGR rate map as shown in FIG. 23 are provided.

The control unit 55 obtains the fuel injection amount from the fuel injection amount map based on the signals from the rotation speed sensor 53 and the accelerator opening sensor 54, controls the fuel injection amount of the fuel injection valve 48, and Target EGR based on the fuel injection amount and the signal from the rotation speed sensor 53
The target EGR rate is obtained from the rate map, and the intake throttle valve 34 and the EGR valve 36 are drive-controlled so that the target EGR rate is obtained. Further, the bypass valve 51 of the bypass flow passage 50 is drive-controlled.

In this case, the intake throttle valve 34 and the EGR valve 36
Is the ratio (maximum valve opening area ratio) between the maximum flow rate of EGR gas and the maximum flow rate of fresh air when both valves are fully opened.
When the rate is 1, the maximum EGR rate 1 = the maximum EGR valve passage flow rate / the maximum intake throttle valve passage flow rate (1) When the target EGR rate ≤ the maximum EGR rate 1, the target intake throttle valve opening degree = fully open (2) target EGR valve opening = target EGR rate / maximum EGR rate 1 (3) and when target EGR rate> maximum EGR rate 1 target intake throttle valve opening = maximum EGR rate 1 / target EGR rate (4) target The EGR valve opening degree is fully opened (5). That is, one opening is controlled to be fully opened and the other opening is controlled to be decreased so that the target EGR rate is achieved.

Further, the bypass valve 51 is controlled to be opened when the target EGR rate sharply decreases based on the changing speed of the target EGR rate. This is because the maximum speed (absolute value) of the EGR rate change when the intake throttle valve 34 is fully opened, the bypass valve 51 is fully closed, and the EGR valve 36 is changed from fully open to fully closed. , The maximum speed (absolute value) of the EGR rate change when the intake throttle valve 34 is fully opened, the bypass valve 51 is fully opened, and the EGR valve 36 is changed from fully open to fully closed. At the same time, the rate of change of the target EGR rate in one operation cycle is obtained, and the target EGR rate change rate = (target EGR rate before one operation cycle−current target EGR rate) / sampling time (6) target EGR rate change rate When ≤ maximum EGR rate change speed 1, target bypass valve opening = fully closed (7), maximum EGR rate change speed 1 <target EGR rate change speed ≤
When the maximum EGR rate change speed is 2, the target bypass valve opening degree = (target EGR rate change speed−maximum EGR rate change speed 1) / (maximum EGR rate change speed 2−maximum EGR rate change speed 1) (8) When the maximum EGR rate changing speed 2 <target EGR rate changing speed, the bypass valve 51 is controlled so that the target bypass valve opening degree = fully opened (9). That is, the change state of the target EGR rate is determined depending on whether the change rate of the target EGR rate in one calculation cycle is greater than the change rate under each condition, and the bypass valve 51 is controlled based on this.

The target intake throttle valve opening and the target EGR valve opening may be calculated by the following method.

Fresh air flow rate through the intake throttle valve: Qw [kg / s] EGR gas flow rate through the EGR valve: Qegr [kg / s] Collector internal pressure: Pint [Pa] Pressure upstream of the intake throttle valve: Ptvo [Pa ] EGR valve upstream pressure: Pegr [Pa] gas density of the fresh air flowing through the intake throttle valve: ρw [kg / m ^3] density of EGR gas flowing through the EGR valve: ρegr [kg / m ^3] intake throttle valve opening area : Atvo [m ² ] EGR valve opening area: If Aegr [m ² ] (Pint, Pegr, ρw, ρegr may be measured values or estimated values), the target EGR rate ≤ the maximum EGR rate 1 is the target intake throttle Valve opening = fully open

[0045]

[Equation 1]

Qegr = Qw × target EGR rate

[0047]

[Equation 2]

When the target EGR rate> maximum EGR rate 1, target EGR valve opening = full open

[0049]

(Equation 3)

Qw = Qegr / target EGR rate

[0051]

[Equation 4]

Set to

Next, E by the control unit 55
The GR control will be described based on the flowchart of FIG.

First, in step 1, the target EGR rate obtained from the engine speed and the fuel injection amount is set to the above-mentioned maximum EGR.
Compare with rate 1.

When the target EGR rate is less than or equal to the maximum EGR rate 1, the intake throttle valve opening (= fully open) and the EGR valve opening (= target EGR rate / maximum EGR rate 1 to obtain the target EGR rate in step 2). ) Is determined, and the intake throttle valve 34, EG
The R valve 36 is controlled.

When the target EGR rate is larger than the maximum EGR rate 1, the intake throttle valve opening (= maximum EGR rate 1 / target EGR rate) for obtaining the target EGR rate in step 3, EG
The R valve opening (= fully open) is calculated, and the intake throttle valve 3
4. Control the EGR valve 36.

In step 4, the changing speed of the target EGR rate is calculated from the target EGR rate obtained this time and the target EGR rate obtained last time.

In steps 5 and 6, the target EGR rate changing speed is compared with the maximum EGR rate changing speed 1 and the maximum EGR rate changing speed 2 described above.

When the target EGR rate change speed is less than the maximum EGR rate change speed 1, that is, when the change in the target EGR rate is small, the bypass valve 51 is fully closed in step 7.

When the target EGR rate changing speed is larger than the maximum EGR rate changing speed 1 and is equal to or less than the maximum EGR rate changing speed 2, that is, when the change in the target EGR rate is medium, the bypass valve 51 is operated in step 8. The opening (=
[Target EGR rate change rate-maximum EGR rate change rate 1] /
[Maximum EGR rate change rate 2-maximum EGR rate change rate 1]).

When the target EGR rate change speed is larger than the maximum EGR rate change speed 2, that is, when the target EGR rate change is large, the bypass valve 51 is fully opened in step 9.

When the target EGR rate sharply decreases, the intake throttle valve 34 and the EGR valve 3 reach the opening corresponding to the sharply decreased target EGR rate.
6 is controlled, while the bypass valve 51 is driven to open according to the changing speed.

In steps 8 and 9, the bypass valve 5
1 is opened temporarily (for example, 0.02 seconds) and then completely closed. However, it is necessary to match the full opening time of the bypass valve 51 (same as the reference time described later) with the actual diesel engine.

With this configuration, it is possible to avoid excessive intake of the EGR gas flowing into the collector 20 into the cylinder during the operation in which the target EGR rate sharply decreases.

That is, the target EGR rate changes greatly (decreases).
Then, the intake throttle valve 34 and the EGR valve 36 are controlled to the required opening amounts, and the bypass valve 51 of the bypass flow passage 50 is fully opened based on the changing speed of the target EGR rate, so that the gas in the collector 20 is released. The bypass flow passage 50 flows out into the exhaust passage 32 downstream of the exhaust turbine 42 of the turbocharger 40.

When the change (decrease) in the target EGR rate is medium, the intake throttle valve 34 and the EGR valve 36 are controlled to the required opening degrees, and a predetermined opening rate is set based on the change rate of the target EGR rate. The bypass valve 51 of the bypass passage 50 is opened every time, and the gas in the collector 20 is exhausted from the bypass passage 50 to the exhaust passage 3 downstream of the exhaust turbine 42 of the turbocharger 40.
Spilled to 2.

In this case, due to the supercharging of the turbocharger 40, the gas in the collector 20 smoothly flows out to the exhaust passage 32 downstream of the low-pressure exhaust turbine 42 according to the opening degree of the bypass valve 51. This prevents the EGR gas in the collector 20 from being sucked into the cylinder.

FIG. 3 shows a simulation result when the target EGR rate is changed from 80% to 0%. The EGR rate is rapidly reduced when the bypass valve 51 is fully opened.

Therefore, it is possible to accurately reduce the occurrence of exhaust smoke due to excessive EGR gas when the engine is suddenly started from the idle operation, and to sacrifice the engine output, for example, by limiting the fuel injection amount. Is avoided and good engine performance and exhaust performance are secured.

Since the bypass valve 51 is temporarily opened, it does not affect the intake air amount.

FIG. 4 shows a second embodiment of the present invention. This is provided with a supercharger 60 directly driven by the engine 30 instead of the turbocharger, and the bypass flow passage 50 is connected to the exhaust passage 32 downstream of the opening of the EGR passage 33.

In this case as well, if the target EGR rate suddenly decreases,
The gas in the collector 20 smoothly flows out to the exhaust passage 32 having a low pressure according to the opening degree of the bypass valve 51.

FIG. 5 shows a third embodiment of the present invention. This controls the bypass valve 51 into two positions, fully open and fully closed.

First, in step 11, the target EGR rate obtained from the engine speed and the fuel injection amount is set to the above-mentioned maximum EG.
Compare with R rate 1.

When the target EGR rate is less than or equal to the maximum EGR rate 1, the intake throttle valve opening (= fully open), the EGR valve opening (= target EGR rate / maximum EGR rate 1 to obtain the target EGR rate in step 12). ) Is calculated and the intake throttle valve 34, E
The GR valve 36 is controlled.

When the target EGR rate is larger than the maximum EGR rate 1, the intake throttle valve opening (= maximum EGR rate 1 / target EGR rate), E, at which the target EGR rate is obtained in step 13.
The GR valve opening (= full open) is calculated, and the intake throttle valve 3 is set to the opening.
4. Control the EGR valve 36.

In step 14, the target EGR obtained this time is calculated.
The rate of change of the target EGR rate is calculated from the rate and the previously obtained target EGR rate.

In steps 15 and 16, the target EGR rate change speed is compared with the maximum EGR rate change speed 1 and the maximum EGR rate change speed 2 described above.

When the target EGR rate changing speed is less than the maximum EGR rate changing speed 1, that is, when the change in the target EGR rate is small, the bypass valve 51 is fully closed in step 17.

When the target EGR rate changing speed is larger than the maximum EGR rate changing speed 1 and is equal to or less than the maximum EGR rate changing speed 2, that is, when the change in the target EGR rate is medium, the bypass valve 51 is operated in step 18. Time to match the change speed,
Fully open.

This time is equal to [target EGR rate change speed-maximum EGR rate change speed 1] / [maximum EGR rate change speed 2-maximum EGR rate change speed 1] (reference bypass valve opening degree in the above embodiment) (Value corresponding to) is multiplied to obtain.

When the target EGR rate changing speed is larger than the maximum EGR rate changing speed 2, that is, when the target EGR rate changing is large, the bypass valve 51 is fully opened for a reference time in step 19.

When the target EGR rate sharply decreases, the intake throttle valve 34 and the EGR valve 3 reach the opening corresponding to the sharply decreased target EGR rate.
6 is controlled, the bypass valve 51 is fully opened for a predetermined time based on the changing speed.

The reference time is set to 0.02 seconds, for example.

By controlling the fully open time of the bypass valve 51 according to the changing speed of the target EGR rate in this way, the gas in the collector 20 is more smoothly discharged from the bypass flow passage 50 to the exhaust passage 32.

Since the bypass valve 51 can be controlled in two positions, it is not necessary to use a step motor or the like for the bypass valve 51, and a simple drive mechanism is sufficient.

6 and 7 show a fourth embodiment of the present invention. This controls the intake throttle valve 34 to three positions of fully open, middle and fully closed.

In this case, the EGR passing through the EGR valve 36
The ratio of the maximum flow rate of gas to the maximum flow rate of fresh air passing through the intake throttle valve 34 at each of the fully open, medium and fully closed openings is expressed by the maximum E
The GR rate, the maximum EGR rate 2 and the maximum EGR rate 3 are given in advance.

Maximum EGR rate 1 = maximum EGR valve passage flow rate / maximum passage flow rate when the intake throttle valve is fully opened (10) Maximum EGR rate 2 = maximum EGR valve passage flow rate / maximum passage rate when the intake throttle valve is in the middle position (11) Maximum EGR rate 3 = maximum EGR valve passage flow rate / maximum passage flow rate when the intake throttle valve is fully closed (12) Further, the bypass valve 51 is fully closed at each opening of the intake throttle valve 34, that is, fully open, medium and fully closed. Then, the maximum speed (absolute value) of the EGR rate change when the EGR valve 36 is changed from fully open to fully closed is the maximum EGR rate change speed 1a (when fully open) and the maximum EGR rate change speed 1b (when medium). , The maximum EGR rate changing speed 1c (when fully closed), the bypass valve 51 is fully opened and the EGR valve 36 is changed from fully open to fully closed at each opening of the intake throttle valve 34, which is fully open, medium, and fully closed. E when you let
The maximum speed (absolute value) of the GR rate change is given as the maximum EGR rate change speed 2a (when fully open), the maximum EGR rate change speed 2b (when medium), and the maximum EGR rate change speed 2c (when fully closed).

In steps 21 to 23 of FIG. 6, the target EGR rate obtained from the engine speed and the fuel injection amount is set to the maximum EG.
R rate 1, maximum EGR rate 2, maximum EGR rate 3 (maximum EGR
Rate 1 <maximum EGR rate 2 <maximum EGR rate 3).

When the target EGR rate is less than or equal to the maximum EGR rate 1, the intake throttle valve opening (= fully open), the EGR valve opening (= target EGR rate / maximum EGR rate 1 to obtain the target EGR rate in step 24). ) Is calculated and the intake throttle valve 34, E
The GR valve 36 is controlled.

When the target EGR rate is greater than the maximum EGR rate 1 and less than or equal to the maximum EGR rate 2, the intake throttle valve opening (= medium), EGR for obtaining the target EGR rate in step 25.
The valve opening degree (= target EGR rate / maximum EGR rate 2) is obtained, and the intake throttle valve 34 and the EGR valve 36 are controlled to the opening degree.

When the target EGR rate is greater than the maximum EGR rate 2 and less than or equal to the maximum EGR rate 3, the intake throttle valve opening (= fully closed), EGR for obtaining the target EGR rate in step 26.
The valve opening (= target EGR rate / maximum EGR rate 3) is obtained, and the intake throttle valve 34 and the EGR valve 36 are controlled to the opening.

When the target EGR rate is greater than the maximum EGR rate 3, the intake throttle valve opening (= fully closed), EGR valve opening (= target EGR) that obtains the target EGR rate in step 27.
Rate / maximum EGR rate 3), and the intake throttle valve 3
4. Control the EGR valve 36.

In step 31 of FIG. 7, the changing speed of the target EGR rate is calculated from the target EGR rate obtained this time and the target EGR rate obtained last time.

In steps 32 and 33, the target EGR rate change speed is set to the maximum EGR rate change speed 1 (1a or 1b or 1c) corresponding to the intake throttle opening, and the corresponding maximum EGR rate change speed 2 (2a or 2b). Or compare with 2c).

Maximum EG to which the target EGR rate change speed corresponds
When the R rate change speed is 1 or less, that is, when the change in the target EGR rate is small, the bypass valve 51 is fully closed in step 34.

Maximum EG to which the target EGR rate change speed corresponds
When the change rate is greater than the R rate change rate 1 and equal to or less than the corresponding maximum EGR rate change rate 2, that is, when the change in the target EGR rate is medium, the opening degree of the bypass valve 51 adjusted to the change rate in step 35 Open the reference time (for example, 0.02 seconds).

This opening is [target EGR rate change speed-maximum EGR rate change speed 1] / [maximum EGR rate change speed 2-
Maximum EGR rate change speed 1].

Maximum EG to which the target EGR rate change speed corresponds
If it is larger than the R rate change speed 2, that is, if the change of the target EGR rate is large, at step 36, the bypass valve 5
Open 1 for the standard time.

According to this, the intake throttle valve 34 can be easily controlled. Instead of controlling the opening degree of the bypass valve 51, the full opening time may be controlled as in the third embodiment.

8 to 14 show a fifth embodiment of the present invention. This delays the fuel injection timing of the fuel injection valve 48 in the high EGR rate operation range and enhances the swirl (swirl vortex) generated in the combustion chamber.

The fuel injection pump 65 shown in FIG. 8 is a distribution type in which the fuel injection amount and the fuel injection timing are electronically controlled.
It is known.

In FIG. 8, reference numeral 66 is a drive shaft connected to the output shaft of the engine 30, 67 is a vane type feed pump driven by the drive shaft 66, which is sucked by a feed pump 67 from a fuel inlet (not shown). The fuel is
It is supplied to the pump chamber 69 in the housing 68 and sent to the plunger chamber 72 of the plunger pump 71 via the suction passage 70 opening to the pump chamber 69.

A pawl 74a of a face cam 74 fixed to the base end of the plunger 73 is axially slidably connected to one end of the drive shaft 66, and the face cam 74 and the plunger are connected via the pawl 74a. 73 is located on the same axis as the drive shaft 66, and the plunger 73 is configured to be displaceable in the axial direction.

A roller holder 7 carrying a plurality of rollers 75 is provided on the outer periphery of the connecting portion between the drive shaft 66 and the face cam 74.
6 is arranged concentrically with the drive shaft 66, and the face cam 7
4, a cam surface 74b forming a variable speed cam corresponding to the number of cylinders is formed, and the cam surface 74b is pressed against the roller 75 by a spring 77.

The plunger 73 is provided with the same number of suction grooves 78 as the cylinders of the engine at the tip thereof, and the cam surface 74
When b travels with the drive shaft 66 and goes over the roller 75 provided in the roller holder 76 and reciprocates by a predetermined cam lift, the fuel sucked from the suction groove 78 into the plunger chamber 72 communicates with the plunger chamber 72. Not sent from the distribution port for each cylinder through the delivery valve to the fuel injection valve 48 under pressure.

Reference numeral 79 is a fuel return passage which connects the plunger chamber 72 and the low pressure pump chamber 69. The fuel return passage 79 is driven by a signal (drive pulse) from a drive circuit in accordance with the operating conditions of the engine. A high-speed response type solenoid valve 80 is installed.

The solenoid valve 80 is provided for injection control. When the solenoid valve 80 is closed during the compression stroke of the plunger 73, fuel injection starts, and when the solenoid valve 80 is opened, injection ends. . That is, the fuel injection start timing is controlled by the valve closing timing of the electromagnetic valve 80, and the injection amount is controlled by the valve closing period.

The fuel injection timing is delayed so that the ignition delay period of the injected fuel becomes longer in the operating range where the EGR rate is higher.

As shown in FIG. 9, the fuel injection timing is set to the piston top dead center (TDC) in the low speed and low load range of the high EGR rate (see FIG. 23). Due to this delay, the temperature in the combustion chamber at the ignition timing is set to a low temperature state and the premixed combustion ratio is increased, thereby suppressing the generation of smoke in the high EGR state.

On the other hand, the injection timing is advanced as the rotation and load increase. This is because even if the ignition delay time is constant, the ignition delay crank angle (a value obtained by converting the ignition delay time into a crank angle) increases in proportion to the increase in the engine speed, and the predetermined ignition occurs at low EGR. The injection timing is advanced to obtain the timing.

In order to obtain the injection timing shown in FIG. 9, the control unit 55 controls the opening / closing timing of the solenoid valve 80.

FIG. 10 shows a flow chart for controlling the fuel injection timing and injection period (injection amount).

At step 41, the engine speed Ne,
The accelerator opening Acc, the engine cooling water temperature TW, and the fuel temperature TF are read. The engine speed Ne is
Scale pulse (angle signal) that is obtained at the same time by the reference pulse sent from the fuel injection pump 65
To read the crank angle. The cooling water temperature TW and the fuel temperature TF are detected by a sensor (not shown).

In step 42, the basic fuel injection timing Itm and the basic fuel injection period Avm are obtained by looking up each map from the read engine speed Ne and the accelerator opening Acc.

The map of the basic injection timing Itm is a map (not shown) in which the accelerator opening Acc and the engine speed Ne are set as parameters so that the injection timing characteristic of FIG. 9 can be obtained. The basic injection period Avm is made longer as the accelerator opening degree Acc becomes larger as shown in FIG.

In step 43, the injection timing correction amount ΔItm is obtained from the fuel temperature TF and the cooling water temperature TW, and step 4
In 4, the injection timing is corrected by adding this to the basic injection timing Itm.

The injection timing correction amount ΔItm is two correction amounts Δ
12 is the sum of Itm ₁ and ΔItm ₂ , and FIG.
Itm ₁ characteristics, and FIG. 13 shows the water temperature correction amount ΔItm ₂ characteristics. In any of the characteristics, the reason why the advance angle correction amount is increased as the temperature becomes lower is that the combustion speed becomes slower as the temperature becomes lower.

The injection timing IT (= Itm + Δ obtained in this way
Itm) and the basic injection period Avm are stored in a predetermined address in step 45. The electromagnetic valve 80 is closed at the injection timing IT, and the electromagnetic valve 80 is opened at the timing when the basic injection period Avm has elapsed from the valve closing timing.

On the other hand, a swirl valve 83 having a predetermined cutout 82 formed in each branch pipe 81 extending from the correlator 38 of the engine 30 toward the intake port, as shown in FIG.
Is installed.

The swirl valve 83 is controlled by the control unit 55 so as to be closed in the low speed and low load region via an actuator (not shown) connected to the rotating shaft 84.

When the swirl valve 83 is closed, intake air flows in only through the notch 82, so the flow velocity of intake air taken into the combustion chamber is increased, and swirl is generated in the combustion chamber.

If one cylinder has two intake valves, the swirl may be generated by closing one intake valve in the low speed and low load region.

The structure of the entire engine and other controls are the same as those in the above-described embodiments.

Next, this operation will be described with reference to FIG.

FIG. 15 shows the N ratio with respect to the EGR rate when the fuel injection timing is before the top dead center and when the fuel injection timing is delayed until the top dead center.
The concentration characteristics of Ox and smoke are shown, and at the injection timing (IT = -8 ° ATDC) before top dead center, the NOx concentration decreases with an increase in the EGR rate, but the smoke concentration rises in a sharp curve. There is.

On the other hand, the injection timing at the top dead center (IT = T
In DC), the smoke concentration tends to decrease as the EGR rate increases. This decrease in smoke concentration means that the swirl in the combustion chamber promotes the mixing of fuel and air, and as shown in the heat generation pattern shown in the figure, the ignition timing is delayed. This is because the delay period becomes long and most of the combustion is premixed combustion.

As a result, in the operation range of high EGR rate, NO
Smoke can be significantly reduced along with x.

In this case, since the injection timing is corrected according to the fuel temperature and the cooling water temperature, a predetermined ignition delay period and ignition timing can be maintained from a low temperature to a high temperature.

In FIG. 16, a device 87 for strengthening the swirl ratio is provided instead of the swirl valve and the like.

The swirl device 87 includes a spiral passage 88 of a so-called helical intake port 88 (formed by a substantially straight intake passage 88a and a spiral passage 88b around the intake valve axis).
The rotary blade 89 is located near b and is rotatably provided, a link mechanism 90 connected to the rotary blade 89, and a negative pressure actuator 91 when the link mechanism 90 is driven. The swirl ratio can be adjusted with. For example, the blade 89 has a high swirl ratio at the position shown in FIG. 17, and has a low swirl ratio at the position shown in FIG.

This rotary blade system has a quick response and is capable of swirl control in a wide range. Therefore, it is suitable for reducing HC that reacts sensitively to the swirl ratio.

A control solenoid valve 93 is installed in the middle of introducing the negative pressure from the negative pressure source to the negative pressure chamber 92 of the negative pressure actuator 91, and the control solenoid valve 93 is the above-mentioned control unit 55.
The negative pressure to the negative pressure chamber 92 is adjusted by the signal from.

The required characteristics of swirl ratio with respect to operating conditions are shown in FIG. 19. When the medium speed or lower including the high EGR rate region and the region for delaying the injection timing (see FIG. 23, FIG. 9), the swirl ratio is high and the high speed side is high. It has a low swirl.

In the control unit 55, a map (not shown) of the swirl ratio (basic swirl ratio) allocated to the engine speed Ne and the accelerator opening Acc as shown in FIG. 20 so as to obtain this swirl ratio. Is searched for the basic swirl ratio, the opening Vb of the control solenoid valve 93 is read out according to this swirl ratio, and this is stored in a predetermined address (steps 51 to 54). Thus, the opening degree of the control solenoid valve 93 is controlled to the swirl ratio shown in FIG.

That is, due to the high EGR and the delay of the injection timing,
Although NOx and smoke can be significantly reduced, the combustion temperature lowers, so HC tends to increase. This HC is at a level where it can meet the regulation value by mounting an oxidation catalyst, but by strengthening the swirl ratio in this way and thereby promoting the mixing of air and fuel, the HC is significantly increased. It can be reduced and the regulation value can be cleared regardless of the oxidation catalyst.

Further, of course, during acceleration, smoke can be reduced by strengthening the swirl.

[0139]

As described above, according to the first aspect of the invention, the intake throttle valve and the supercharger are provided in the intake introduction passage, the EGR valve is provided in the EGR passage, and the intake throttle valve is driven. The intake throttle valve drive unit, the EGR valve drive unit that drives the EGR valve, the means for setting the fuel injection amount of the fuel injection valve based on the engine speed and the engine load, and the fuel injection amount and the engine speed based on Goal E
A means for setting the GR rate and a target EG based on the target EGR rate
A means for calculating the R valve opening and the target intake throttle valve opening; an EGR valve opening control section for controlling the EGR valve drive section so as to match the actual EGR valve opening with the target EGR valve opening; An intake throttle valve opening control unit that controls the intake throttle valve drive unit so as to match the actual intake throttle valve opening degree with the actual intake throttle valve opening degree is provided, and gas that flows in from the intake introduction passage and inflow from the EGR passage In a diesel engine with a supercharger that mixes EGR gas through a collector and supplies it to a cylinder, a bypass passage that guides the gas in the collector to an exhaust system and a bypass valve that is interposed in the bypass passage are driven. Bypass valve drive unit, means for calculating a target bypass valve opening amount based on the changing speed of the target EGR rate, and control of the bypass valve drive unit so that the actual bypass valve opening amount matches the target bypass valve opening amount. Do Since the Y-pass valve opening control section is provided, it is possible to prevent excessive EGR gas from being sucked into the cylinder after being delayed from the collector at the time of starting the vehicle, so that it is possible to accurately reduce the generation of exhaust smoke and to obtain a good engine performance. Performance can be secured.

According to the second aspect of the invention, the intake throttle valve drive section is provided in which the intake throttle valve and the supercharger are provided in the intake introduction passage, the EGR valve is provided in the EGR passage, and the intake throttle valve is driven. , EG
EGR valve drive unit for driving the R valve, means for setting the fuel injection amount of the fuel injection valve based on the engine speed and engine load, and means for setting the target EGR rate based on the fuel injection amount and the engine speed And means for calculating the target EGR valve opening and the target intake throttle opening based on the target EGR rate, and the EGR valve drive unit is controlled so that the actual EGR valve opening matches the target EGR valve opening. An EGR valve opening control section and an intake throttle valve opening control section for controlling the intake throttle valve drive section so as to match the actual intake throttle valve opening with the target intake throttle valve opening are provided. In a diesel engine with a supercharger, which mixes an inflowing gas and an EGR gas flowing in from an EGR passage through a collector and supplies the mixed gas to a cylinder, a bypass passage for guiding the gas in the collector to an exhaust system, and a bypass passage Viper intervening in A bypass valve drive section for driving the valve, a means for calculating the target bypass valve opening based on the changing speed of the target EGR rate, and a bypass valve for matching the actual bypass valve opening with the target bypass valve opening. A bypass valve opening control unit for controlling the drive unit is provided, and high EG
Since a means for delaying the injection timing of the fuel injection valve by a predetermined amount so as to lengthen the ignition delay period of the injected fuel at the R rate and a means for strengthening the swirl generated in the combustion chamber at the same time are provided at the time of starting the vehicle, etc. It is possible to reduce exhaust smoke and secure good engine performance, maintain good premixed combustion during operation at a high EGR rate, and sufficiently reduce NOx and exhaust smoke.

According to the third aspect of the present invention, by supercharging by the supercharger, the gas in the collector can smoothly flow to the exhaust system when the bypass valve is opened.

According to the fourth aspect of the present invention, the supercharge of the turbocharger allows the gas in the collector to smoothly flow out to the exhaust side of the turbocharger when the bypass valve is opened.

According to the fifth invention, the drive mechanism of the bypass valve can be simplified.

According to the sixth invention, the control of the intake throttle valve becomes easy.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment.

FIG. 2 is a flowchart showing control contents.

FIG. 3 is a characteristic diagram showing simulation results when the bypass valve is fully opened and fully closed.

FIG. 4 is a configuration diagram of a second embodiment.

FIG. 5 is a flowchart showing the control contents of the third embodiment.

FIG. 6 is a flowchart showing the control contents of the fourth embodiment.

FIG. 7 is a flowchart showing the control contents of the fourth embodiment.

FIG. 8 is a sectional view of a fuel injection pump of a fifth embodiment.

FIG. 9 is a characteristic diagram of injection timing.

FIG. 10 is a control flowchart of an injection timing and an injection period.

FIG. 11 is a characteristic diagram of a basic injection period.

FIG. 12 is a characteristic diagram of a fuel temperature correction amount.

FIG. 13 is a characteristic diagram of a water temperature correction amount.

FIG. 14 is a front view of the swirl valve.

FIG. 15 is a characteristic diagram of each concentration of smoke and NOx with respect to the EGR rate.

FIG. 16 is a configuration diagram of a main part of a swirl device.

FIG. 17 is a perspective view showing a blade position during high swirl.

FIG. 18 is a perspective view showing a blade position at a low swirl.

FIG. 19 is a characteristic diagram of swirl ratio.

FIG. 20 is a control flowchart of a swirl ratio.

FIG. 21 is a configuration diagram of a conventional example.

FIG. 22 is a characteristic diagram of a fuel injection amount.

FIG. 23 is a characteristic diagram of an EGR rate.

FIG. 24 is a block diagram of the invention.

FIG. 25 is a block diagram of the invention.

[Description of Reference Signs] 30 engine body 31 intake air intake passage 32 exhaust passage 33 EGR passage 34 intake throttle valve 35 intake throttle valve driving step motor 36 EGR valve 37 EGR valve driving step motor 38 collector 40 turbocharger 48 fuel injection valve 50 Bypass flow path 51 Bypass valve 52 Step motor for driving bypass valve 53 Rotation speed sensor 54 Accelerator opening sensor 55 Control unit 60 Supercharger 65 Fuel injection pump 80 Control solenoid valve 83 Swirl valve 87 Swirl device 89 Rotating blade 91 Negative pressure actuator 93 Control solenoid valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F02B 37/00 302 F02B 37/00 302F F02D 41/02 301 F02D 41/02 301E 41/10 335 41 / 10 335Z 43/00 301 43/00 301N 301L

Claims (6)

[Claims] 1. An intake throttle valve and a turbocharger are installed in an intake introduction passage, an EGR valve is installed in an EGR passage, and an intake throttle valve drive section for driving the intake throttle valve and an EGR valve are driven. EG
R valve drive unit, means for setting the fuel injection amount of the fuel injection valve based on the engine speed and engine load, means for setting the target EGR rate based on the fuel injection amount and engine speed, and the target EG
A means for calculating the target EGR valve opening and the target intake throttle opening based on the R ratio, and an EGR valve opening for controlling the EGR valve drive unit so that the actual EGR valve opening matches the target EGR valve opening. Control unit and an intake throttle valve opening control unit that controls the intake throttle valve drive unit so that the actual intake throttle valve opening matches the actual intake throttle opening, and gas flowing from the intake introduction passage is provided. In a diesel engine with a supercharger, which mixes a gas and an EGR gas flowing from an EGR passage through a collector and supplies the mixed gas to a cylinder, a bypass flow path for guiding the gas in the collector to an exhaust system, and a bypass flow path A bypass valve drive unit that drives the bypass valve, a unit that calculates the target bypass valve opening based on the change speed of the target EGR rate, and an actual bypass valve opening that matches the target bypass valve opening. Viper An EGR device for a diesel engine with a supercharger, comprising: a bypass valve opening control unit that controls a valve drive unit. 2. An intake throttle valve and a turbocharger are installed in the intake introduction passage, an EGR valve is installed in the EGR passage, and an intake throttle valve drive section for driving the intake throttle valve and an EGR valve are driven. EG
R valve drive unit, means for setting the fuel injection amount of the fuel injection valve based on the engine speed and engine load, means for setting the target EGR rate based on the fuel injection amount and engine speed, and the target EG
A means for calculating the target EGR valve opening and the target intake throttle opening based on the R ratio, and an EGR valve opening for controlling the EGR valve drive unit so that the actual EGR valve opening matches the target EGR valve opening. Control unit and an intake throttle valve opening control unit that controls the intake throttle valve drive unit so that the actual intake throttle valve opening matches the actual intake throttle opening, and gas flowing from the intake introduction passage is provided. In a diesel engine with a supercharger, which mixes a gas and an EGR gas flowing from an EGR passage through a collector and supplies the mixed gas to a cylinder, a bypass flow path for guiding the gas in the collector to an exhaust system, and a bypass flow path A bypass valve drive unit that drives the bypass valve, a unit that calculates the target bypass valve opening based on the change speed of the target EGR rate, and an actual bypass valve opening that matches the target bypass valve opening. Viper And a means for delaying the injection timing of the fuel injection valve by a predetermined amount so as to prolong the ignition delay period of the injected fuel when the EGR rate is high, and a bypass valve opening control section for controlling the fuel injection valve is also provided. E of a diesel engine with a supercharger, which is provided with a means for strengthening a swirl generated in a room.
GR device. 3. The EGR device for a diesel engine with a supercharger according to claim 1, wherein the supercharger is a supercharger that is supercharged by driving the engine. 4. The supercharger according to claim 1 or 2, wherein the supercharger is a turbocharger that is supercharged by driving exhaust gas of an engine, and the bypass passage connects a collector to a downstream side of an exhaust side of the turbocharger. EGR device for diesel engine. 5. The EGR device for a diesel engine with a supercharger according to claim 1 or 2, wherein the bypass valve is controlled in two positions of fully closed and fully opened. 6. The EGR device for a diesel engine with a supercharger according to claim 1, wherein the intake throttle valve is controlled to several positions including a fully open position.