JPH09264201A - Exhaust recirculation controller for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out exhaust recirculation without causing any damage in a compressor in an engine provided with a turbosupercharger and without any increase in pumping loss. SOLUTION: An exhaust recirculation controller 100 for an engine 1 is provided with a turbosupercharger 50 consisting of a turbine 51 arranged in an exhaust pipe 37 and a compressor 52 arranged in an intake pipe 27. A cylinder head 1C is provided with the second exhaust port 34 for exhaust recirculation, the second exhaust valve 32 opening/closing the second exhaust port 32, the third cam shaft 41 opening/closing the second exhaust valve 32, a valve opening timing regulating device 42, and the second exhaust manifold 36 connecting the second exhaust port 34 to the intake pipe 27 on the downstream side of the compressor 52. By means of an ECU 61, the second exhaust valve 32 is controlled to be opened/closed according to the engine operating condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust gas recirculation control device, and more particularly to an engine exhaust gas recirculation control device equipped with a turbocharger.

[0002]

2. Description of the Related Art Conventionally, for example, as shown in FIG.
The exhaust system 3 (exhaust manifold 3A) of the engine 1 is provided with an exhaust gas recirculation path 8 that connects the exhaust system 3 and the intake system 2 of the engine 1 (for example, the intake manifold 2A) to the exhaust gas recirculation path 8. Valve (hereinafter referred to as "EGR valve")
7 is provided and the EGR valve 7 is opened by the electronic control unit 6 in accordance with the engine load state and the like, whereby a part of the exhaust gas is returned to the intake system 2 of the engine 1 to lower the combustion temperature of the air-fuel mixture. Therefore, the exhaust gas recirculation control device 10 that reduces the amount of NOx generated is known.

[0003]

By the way, in the engine 1 equipped with the turbocharger 5 of recent years, when the exhaust gas is recirculated to the intake system 2, as shown in FIG. 4, the turbocharger 5 and the intake pipe are shown. A method of returning to the downstream of the intercooler 5C provided in 2B and a method of returning to the upstream of the turbocharger 5, although not shown in the figure, are considered. But,
In these cases, the following problems occur.

That is, when the exhaust gas is recirculated downstream of the turbocharger 5 and the intercooler 5C, the exhaust gas is recirculated to the intake system 2 pressurized by the turbocharger 5, as shown in FIG. Since it is necessary to provide a throttle 3C upstream of the turbine 5A of the exhaust system 3 (exhaust pipe 3B) to raise the pressure of the exhaust gas to some extent, the pressure of the exhaust system 3 is increased by this throttle 3C. If it is raised, the pumping loss of the engine 1 will be raised.

When the exhaust gas is recirculated upstream of the compressor 5B of the turbocharger 5 (not shown), the compressor 5B of the turbocharger 5 and the intercooler 5C are contaminated by carbon and the like mixed in the exhaust gas. Will be. The present invention has been made in view of such circumstances, and in an engine including a turbocharger, exhaust gas recirculation is performed without polluting the turbocharger and causing an increase in pumping loss of the engine. An object of the present invention is to provide an exhaust gas recirculation control device for an engine, which is equipped with a turbocharger.

[0006]

In order to achieve the above object, the invention of claim 1 is a cylinder head provided with an intake port and a first exhaust port, and an intake passage connected to the intake port, A first exhaust passage connected to the first exhaust port, an intake valve that opens and closes the intake port, and a first exhaust valve that opens and closes the first exhaust port,
A second exhaust port provided in the cylinder head in an exhaust gas recirculation control device for an engine, which includes a turbocharger including a turbine arranged in the first exhaust passage and a compressor arranged in the intake passage. A second exhaust valve for opening / closing the second exhaust port, a valve opening / closing means for opening / closing the second exhaust valve, one end connected to the second exhaust port and the other end downstream of the compressor. A second exhaust passage opening to the side intake passage, and control means for controlling the opening / closing of the second exhaust valve by performing the valve opening / closing means in accordance with the engine operating state.

According to a second aspect of the invention, the control means is
The valve opening / closing means controls opening / closing of the second exhaust valve in accordance with the engine speed and the engine load. According to the invention of claim 3, the valve opening / closing means is
It is composed of a cam shaft having a three-dimensional cam and an opening / closing timing adjusting means for axially displacing the cam shaft to determine a substantial cam shape for opening and closing the second exhaust valve.

According to a fourth aspect of the invention, the second exhaust valve is an electromagnetic valve. Further, in the invention of claim 5, the control means opens the second exhaust valve within a period in which the first exhaust valve is open.

(Operation) According to the invention of claim 1, the exhaust gas having a pressure higher than that of the intake system can be recirculated to the downstream side of the compressor of the intake system without providing a throttle valve in the exhaust passage.

According to the second aspect of the present invention, it is possible to select an engine operating state with a large amount of NOx emissions and perform an appropriate amount of exhaust gas recirculation according to the engine operating state.
Further, according to the invention of claim 3, the second exhaust valve for opening and closing the exhaust gas of a desired pressure is opened and closed in synchronization with the opening and closing of the first exhaust valve which causes the pulsation of the exhaust gas pressure. Control can be performed easily.

Further, according to the invention of claim 4, the opening / closing operation of the second exhaust valve is made completely independent of the operation of the first exhaust valve, so that the exhaust gas recirculation having a high degree of freedom and high accuracy is possible. become. Further, according to the invention of claim 5, the second exhaust valve is opened while the pressure of the exhaust gas in the exhaust passage is relatively high, so that the pressure of the exhaust gas recirculated to the exhaust can be always higher than that of the intake system. .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings. Note that the first embodiment corresponds to claims 1 to 3 and claim 5. FIG. 1 is an overall configuration diagram showing an exhaust gas recirculation control device 100 of the engine 1, and FIG. 2 is a piston (not shown) of the engine 1.
Displacement and the first and second intake valves 21, 22 and the first and second intake valves
3 is a graph showing changes in the lift amounts of the exhaust valves 31 and 32 of FIG.

First, the exhaust gas recirculation control device 10 of the engine 1
The configuration of 0 will be described. The engine 1 is, for example, 4
A cylinder (# 1 to # 4) diesel engine, the exhaust gas recirculation control device 100 of the engine 1 includes an intake system 20, an exhaust system 30, a valve system 40, a turbocharger 50, and a valve opening timing control unit 60. Is equipped with.

Specifically, the intake system 20 comprises an intake manifold 25 and an intake pipe 27 which form an intake passage.
In the intake system 20, the cylinder head 1C of the engine 1 has a first intake port 23 for each of the cylinders # 1 to # 4.
A second intake port 24 is provided, and an intake manifold 25 is provided in the first intake port 23 and the second intake port 24.
Are connected to the respective branch pipes 25a. In addition, the first
The first intake port 23 and the second intake port 24 of the first opening / closing port 23, 24 for each cylinder # 1 to # 4.
Intake valve 21 and second intake valve 22 are provided (in FIG. 1, only cylinder # 1 is shown).

In addition, the exhaust system 30 includes a first exhaust manifold 35 and an exhaust pipe 37 that form a first exhaust passage, and a second exhaust manifold 36 that forms a second exhaust passage.
In the exhaust system 30, the cylinder head 1C is provided with the first exhaust port 33 and the second exhaust port 34 for each of the cylinders # 1 to # 4. Of these, each branch pipe 35a of the first exhaust manifold 35 is connected to the first exhaust port 33, and each branch pipe 36a forming one end of the second exhaust manifold 36 is connected to the second exhaust port 34.
Is connected. The other end 36b of the second exhaust manifold 36 is connected to the connecting portion 25 of the intake manifold 25.
It is opened at c. Then, the first exhaust port 33,
The second exhaust port 34 includes a first exhaust valve 31 for opening and closing the ports 33, 34 for each of the cylinders # 1 to # 4, a second exhaust valve 31,
Exhaust valves 32 are provided respectively.

The valve operating system 40 comprises first to third valve operating devices (only the third valve operating device 40C is shown in FIG. 1).
The first valve operating device includes an intake valve camshaft and a rocker arm (both not shown) for opening and closing the first intake valve 21 and the second intake valve 22. The second valve operating device includes a first exhaust valve camshaft and a rocker arm (both not shown) for opening and closing the first exhaust valve 31. The third valve operating device 40C functions as a valve opening / closing means, and includes a second exhaust valve camshaft 41 and a rocker arm (not shown) for opening / closing the second exhaust valve 32, and opening / closing timing adjusting means. And a valve opening timing adjusting device (for example, a hydraulic actuator) 42.

The second exhaust valve camshaft 41 of the third valve operating device 40C has a three-dimensional cam.
The valve opening timing adjusting device 42 axially moves the second exhaust valve camshaft 41 having this three-dimensional cam on the basis of a signal from an electronic control device (hereinafter referred to as “ECU”) 61 described later. Displacement moves the contact point between the rocker arm and the three-dimensional cam, thus determining the substantial cam shape for opening and closing the second exhaust valve 32. When the second exhaust valve camshaft 41 is axially displaced in this way, the valve opening start timing of the second exhaust valve 32 is adjusted within the range (variable width) shown in FIG.

On the other hand, the turbine 51 of the turbocharger 50 is arranged in the middle of the exhaust pipe 37 connected to the exhaust manifold 35, and the turbo 51 in the middle of the intake pipe 27 connected to the intake manifold 25. The compressor 52 of the supercharger 50 is arranged. An intercooler 53 is arranged downstream of the compressor 52 in the intake pipe 27.

Further, the valve opening timing control unit 60 includes an ECU 61,
An engine speed (Ne) sensor 62 connected to an input port (not shown) of the ECU 61, a rack position sensor 63 for detecting a rack position as an engine load, and other sensors for detecting various other parameters indicating an engine operating state. (For example, an engine cooling temperature sensor, an intake air temperature sensor, an oxygen concentration sensor, etc.) 64.

Exhaust gas recirculation control device 1 constructed in this way
00, the ECU 61 determines that the engine speed (N
The engine operating state is detected according to e) and the rack position and the like, and the program stored in the memory (not shown) is executed according to the engine speed (Ne) and the rack position and the like to execute the engine operating state. An optimum exhaust gas recirculation amount (hereinafter referred to as "EGR gas amount") is determined. As a method of determining the EGR gas amount, for example, from the map stored in the memory (not shown) of the ECU 61, the shaft of the second exhaust valve camshaft 41 is determined based on the engine speed (Ne) and the rack position. The optimum value of the displacement amount (control value that determines the EGR gas amount) is read out, and this is read by another sensor 6
There is a method of obtaining the optimum amount of EGR gas by making a correction based on the signal from No. 4.

The ECU 61 outputs a signal representing the shaft displacement amount for obtaining the optimum EGR gas amount thus determined to the valve opening timing adjusting device 42, and the valve opening timing adjusting device 42 receiving the signal outputs the signal. The second exhaust valve cam shaft 41 is displaced according to the shaft displacement amount.
Next, the second exhaust valve 32 whose valve opening timing (particularly the valve opening start timing) is controlled by the ECU 61.
A specific operation will be described.

As shown in FIG. 2, the lift amount of the second exhaust valve 32 is set to a constant value smaller than the lift amount of the first exhaust valve 31, and the second exhaust valve 32 is also set. Is open (between t1 and t3 in FIG. 2 or t2 and t4)
Between time points; hereinafter referred to as "second valve opening period"), the period during which the first exhaust valve 31 is open (between t1 and t4 time points in FIG. 2;
Hereinafter, it is controlled so as to relatively vary with respect to the “first valve opening period” (variable range).

In this case, during the first valve opening period, the exhaust gas is efficiently supplied to the first exhaust manifold 35 and the exhaust pipe 37 when the exhaust gas is blown down at high temperature and high pressure (high energy). (The exhaust gas is efficiently sent to the turbine 51 side), in particular, the valve opening timing thereof is set. Further, during the second valve opening period, when the piston (not shown) rises in the exhaust stroke, the exhaust gas of relatively low temperature and low pressure is sent to the intake system 20 whose pressure is lower than that of the exhaust system. The valve opening is set to start at a timing later than the valve opening timing of the first exhaust valve 31.

Thus, by opening the second exhaust valve 32 in the exhaust stroke after blowdown, the EG
When the R gas is recirculated, the exhaust system 30 is connected to the intake system 20 at a higher pressure than the intake system 20,
There is no need to provide a throttle in the exhaust system 30 as in the conventional case, and the pumping loss of the engine 1 can be prevented from increasing.
By the way, in the exhaust gas recirculation control device 100, the second
The maximum amount of EGR gas that can be recirculated by the exhaust valve 32 of
The lift amount of the second exhaust valve 32 is determined so that about 30% of the exhaust gas can be obtained. Then, by adjusting the valve opening start timing of the second exhaust valve 32 within the variable width shown in FIG. 2 (between time points t1 and t2), the second exhaust valve 32 opens with the same lift amount. However, since the pressure of the exhaust gas fluctuates at each time point, the actual EGR gas amount can be made different.

By the way, when the second exhaust valve 32 is opened at an early timing (broken line in FIG. 2), when the in-cylinder pressure of the engine 1 cylinder (not shown) is relatively high, the exhaust gas becomes the second exhaust gas.
Through the exhaust manifold 36 of the intake manifold 25
Since the gas is recirculated to the side, the amount of EGR gas increases. Conversely,
If the second exhaust valve 32 is opened at a late timing (see FIG. 2).
(One-dot chain line) EGR gas amount decreases.

In this way, by simply adjusting the valve opening start timing of the second exhaust valve 32, E which is recirculated to the intake manifold 25 side through the second exhaust manifold 36.
The amount of GR gas can be adjusted. Thus, the valve opening timing of the second exhaust valve 32 is determined by the ECU 61 according to the engine speed Ne, the engine load (rack position), etc., and therefore, the optimum EGR gas according to the engine operating state. A quantity control is performed.

Such exhaust gas recirculation control can control the EGR gas amount with higher accuracy than, for example, known exhaust gas recirculation control using a negative pressure responsive valve that operates according to the pressure in the intake pipe of the engine 1. become. Note that the maximum EGR gas amount becomes substantially equal to the gas amount remaining in the cylinder (not shown) of the engine 1 when the first exhaust valve 31 is closed, and the first The maximum EGR gas amount can also be accurately determined by setting the opening / closing period of the exhaust valve 31 (designing the cam shape of the first exhaust valve camshaft).

(Second Embodiment) FIG. 3 is an overall configuration diagram of an exhaust gas recirculation control device 200 of the second embodiment. The second embodiment corresponds to claims 1, 2, 4, and 5. Incidentally, in the second embodiment,
The point that the second exhaust valve is configured by the first to fourth electromagnetic valves 73a to 73d is different from the above-described first embodiment. Therefore, the same members as those in the first embodiment include: The same reference numerals are given and detailed description thereof is omitted.

The exhaust gas recirculation control device 200 includes an intake system 20,
An exhaust system 30, a valve system 40, a turbocharger 50, and a solenoid valve control unit 70 are provided. Of these, the second exhaust ports 34 of the cylinders # 1 to # 4 of the exhaust system 30 are provided with first to fourth electromagnetic valves 73a to 73d as second exhaust valves. The valve operating system 40 includes a first valve operating device (not shown) for opening and closing the first intake valve 21 and the second intake valve 22, and a second valve operating device for opening and closing the first exhaust valve 31. A valve train (not shown) is provided.

The solenoid valve control unit 70 includes an ECU 71 and an EC.
It is composed of an engine speed (Ne) sensor 62, a rack position sensor 63, a crank angle sensor 72, and another sensor 64 connected to an input port (not shown) of U71. The solenoid valve control unit 70 controls the first to fourth solenoid valves 73a to 73d provided as the second exhaust valve as shown in FIG.
As shown in, the valve opening operation (particularly the valve opening start timing) is controlled.

ECU 7 constituting the solenoid valve controller 70
1 detects the operating state of the engine 1 based on the signals from the Ne sensor 62, the rack position sensor 63, and the other sensor 64, and E suitable for the detected engine operating state.
The amount of GR gas is determined, and a signal representing the period during which the first to fourth electromagnetic valves 73a to 73d are open (second valve opening period) is determined according to the determined amount of EGR gas. ~ Fourth
To the solenoid valves 73a to 73d. In this case, the ECU
Reference numeral 71 denotes a period in which the first exhaust valve 31 is open based on a signal from the crank angle sensor 72 (first valve opening period).
Alternatively, the piston displacement of the engine 1 is detected, and the first valve opening period or the second valve opening period relative to the detected piston displacement is determined.

The lift amounts of the first to fourth solenoid valves 73a to 73d are set smaller than the lift amount of the first exhaust valve 31, as shown in FIG. 2, as in the first embodiment. In addition, the second valve opening period is always within the first valve opening period (variable range). In this way, the first to fourth solenoid valves 7
The EGR gas amount through the second exhaust manifold 36 can be adjusted only by adjusting the valve opening timing of 3a to 73d.

Thus, the opening period of the second exhaust valve 32 is
The ECU 71 determines the EGR gas amount according to the engine speed Ne and the engine load (rack position), and controls the EGR gas amount according to the engine operating state. In this way, when the second exhaust valve is the first to fourth electromagnetic valves 73a to 73d, since the opening / closing control can be performed completely independently of the operation of the first exhaust valve 31, the degree of freedom is high and the accuracy is high. Good exhaust gas recirculation is possible.

In the second embodiment, the first to the fourth
Although the lift amounts of the electromagnetic valves 73a to 73d are made constant and only the valve opening start timing is adjusted, the lift amounts may also be variably controlled.

[0035]

According to the first aspect of the present invention described above,
Exhaust gas with a higher pressure than that of the intake system can be recirculated to the downstream side of the compressor of the intake system without providing a throttle valve in the exhaust system, which does not pollute the turbocharger and causes an increase in pumping loss of the engine. Exhaust gas recirculation can be performed without using.

According to the second aspect of the present invention, it is possible to select an engine operating state with a large amount of NOx emissions and perform an appropriate amount of exhaust gas recirculation according to the engine operating state, thereby improving the efficiency of exhaust gas recirculation control. Can be achieved. According to the third aspect of the invention, the opening / closing control of the second exhaust valve synchronized with the opening / closing of the first exhaust valve that causes the fluctuation of the exhaust gas pressure can be easily performed.

Further, according to the invention of claim 4, the opening / closing operation of the second exhaust valve is made completely independent of the operation of the first exhaust valve, so that the exhaust gas recirculation having a high degree of freedom and high accuracy is possible. become. Further, according to the invention of claim 5, the second exhaust valve is opened in a state where the pressure of the exhaust gas in the exhaust system is high, so the exhaust gas recirculated in the exhaust gas can be always higher than that in the intake system.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an exhaust gas recirculation control device 100 of a first embodiment.

FIG. 2 is a piston displacement of the engine 1 and a first exhaust valve 31.
5 is a graph showing changes in lift amount of the second exhaust valve 32.

FIG. 3 is an overall configuration diagram showing an exhaust gas recirculation control device 200 of a second embodiment.

FIG. 4 is an overall configuration diagram showing a conventional exhaust gas recirculation control device 10.

[Explanation of symbols]

 1 Engine 1C Cylinder Head 20 Intake System 21 First Intake Valve 22 Second Intake Valve 30 Exhaust System 31 First Exhaust Valve 32 Second Exhaust Valve 35 First Exhaust Manifold (First Exhaust Passage) 36th 2 exhaust manifold (second exhaust passage) 37 exhaust pipe (first exhaust passage) 40 valve operating system 40C third valve operating device (valve opening / closing means) 41 second exhaust valve camshaft 42 valve opening timing Adjusting device (opening / closing timing adjusting unit) 50 Turbocharger 51 Turbine 52 Compressor 60 Valve opening timing control unit 61 Electronic control unit (control unit) 70 Electromagnetic valve control unit 71 Electronic control unit (control unit, valve opening / closing unit) 73a to 73d 1st-4th solenoid valve (2nd exhaust valve)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F02D 13/02 F02D 13/02 H 23/00 23/00 JK F02F 1/42 F02F 1/42 K

Claims (5)

[Claims] 1. A cylinder head having an intake port and a first exhaust port, an intake passage connected to the intake port, a first exhaust passage connected to the first exhaust port, and A turbocharger including an intake valve that opens and closes an intake port, a first exhaust valve that opens and closes the first exhaust port, a turbine arranged in the first exhaust passage, and a compressor arranged in the intake passage. An exhaust gas recirculation control device for an engine, comprising a second exhaust port provided in the cylinder head, a second exhaust valve for opening and closing the second exhaust port, and a second exhaust valve. A valve opening / closing means for opening / closing, a second exhaust passage having one end connected to the second exhaust port and the other end opening to an intake passage on the downstream side of the compressor, and the valve opening / closing depending on an engine operating state. Means Exhaust gas recirculation control apparatus for an engine, characterized by comprising a control unit which occupies allowed close control of the performed in the second exhaust valve Te. 2. The control means controls the valve opening / closing means to control the opening / closing of the second exhaust valve according to the engine speed and the engine load. Exhaust gas recirculation control device for engine. 3. The valve opening / closing means includes a cam shaft having a three-dimensional cam, and an opening / closing timing that determines a substantial cam shape for opening / closing the second exhaust valve by displacing the cam shaft in the axial direction. The exhaust gas recirculation control device for an engine according to claim 1 or 2, further comprising an adjusting unit. 4. The exhaust gas recirculation control device for an engine according to claim 1, wherein the second exhaust valve is a solenoid valve. 5. The control means according to claim 1, wherein the second exhaust valve is opened within a period in which the first exhaust valve is open. An exhaust gas recirculation control device for an engine according to claim 1.