JPH0814112A - Hybrid EGR control device and control method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention relates to a control device and a control method for a hybrid EGR, and particularly to operating conditions when a part of exhaust gas of a premixed combustion engine such as a gasoline engine is returned to the intake side. To obtain the optimum exhaust gas recirculation amount, and
The present invention relates to a hybrid EGR control device and a control method therefor capable of obtaining exhaust gas recirculation over a wide range with good followability. In a diesel engine in which exhaust gas of a premixed combustion engine such as a gasoline engine is recirculated to the intake side as exhaust gas recirculation, a compressor for diesel engine supercharging is driven by the premixed combustion engine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid EGR control device and control method therefor, and more particularly to control of a hybrid EGR that recirculates part of exhaust gas of a premixed combustion engine such as a gasoline engine to the intake side. The present invention relates to a device and a control method thereof.

[0002]

2. Description of the Related Art Conventionally, in a diesel engine mounted on an automobile or the like, exhaust gas recirculation (hereinafter referred to as EGR) for recirculating a part of exhaust gas to an intake side in order to reduce NOx in exhaust gas. Already known. Also,
As disclosed in Japanese Utility Model Publication No. 1-127960,
In an engine having a plurality of cylinders, one cylinder is used as a cylinder for burning a gasoline engine, exhaust gas from this cylinder is introduced into an intake system for the other cylinders, and the pistons in the other cylinders and the inner peripheral surface of the cylinder are It is also known to suppress mixing of carbon and the like into the contact portion between the two.

[0003]

However, since the diesel fuel is not desulfurized, it contains sulfur (Sulfa S) in the exhaust gas,
That is, soot is mixed in the EGR gas in addition to SO2. When these EGR gases are introduced into the engine, SO2 is oxidized to SO3, which reacts with water to form sulfuric acid (H2 SO4), which falls into the oil pan from between the piston ring and the cylinder liner and enters the lubricating oil.
This H2 SO4 + component Ca (OH) 2 of the lubricating oil reacts to form CaSO4. At this time, the corrosion and abrasion of the cylinder liner and piston ring by sulfuric acid, and the neutralization of oil reduce the alkali value, obstructing the lubrication of tappets, camshafts, etc., resulting in the problem of impairing the durability of the engine. There is. For this reason, exhaust gas recirculation for recirculating a part of exhaust gas of a gasoline engine to the intake side is disclosed in Japanese Utility Model Laid-Open No. 1-127960. But,
According to Japanese Utility Model Laid-Open No. 1-127960, in an engine having a plurality of cylinders, one cylinder is used as a cylinder for burning a gasoline engine, and exhaust gas from this cylinder is introduced into an intake system for other cylinders. In addition, there is a problem that the optimum exhaust gas recirculation amount is not performed with the optimum followability with respect to changing conditions of the operating conditions (rotation speed, load, etc.) of the diesel engine.

The present invention focuses on the above-mentioned conventional problems and relates to a hybrid EGR control device and a control method thereof, and in particular, a portion of exhaust gas of a premixed combustion engine such as a gasoline engine is recirculated to the intake side. An object of the present invention is to provide a hybrid EGR control device and a control method thereof that can sometimes obtain an optimal exhaust gas recirculation amount for operating conditions and can obtain exhaust gas recirculation with good followability over a wide range.

[0005]

In order to achieve the above object, according to a first aspect of the hybrid EGR control device and control method of the present invention, the exhaust gas of a premixed combustion engine such as a gasoline engine is used as exhaust gas recirculation. In a diesel engine that is recirculated to the intake side, a diesel engine supercharging compressor is driven by a premixed combustion engine.

In the second aspect of the invention, the rotation speed and output torque fluctuate according to the load, accelerator, etc., and the exhaust gas of the premixed combustion engine such as a gasoline engine is recirculated to the intake side as exhaust gas recirculation. In a diesel engine, an EGR valve that controls the flow rate of exhaust gas from the premixed combustion engine to the diesel engine, a position sensor that detects the fuel injection amount to the diesel engine, and a speed sensor that detects the rotational speed of the diesel engine, The control device outputs a required exhaust gas flow rate to the EGR valve in response to a signal from the sensor.

According to the third aspect of the present invention, the diesel engine whose rotational speed and output torque fluctuate depending on the load, the accelerator, etc., and the exhaust gas of a premixed combustion engine such as a gasoline engine is recirculated to the intake side as exhaust gas recirculation. In the engine, driven by a premixed combustion engine, a compressor that supercharges intake air to the diesel engine, a position sensor that detects the fuel injection amount to the diesel engine, and a speed sensor that detects the rotation speed of the diesel engine, The control device outputs a command for varying the rotation speed to the premixed combustion engine in response to signals from both sensors.

According to the fourth aspect of the present invention, the diesel engine in which the rotational speed and the output torque fluctuate according to the load or the accelerator, and the exhaust gas of the premixed combustion engine such as a gasoline engine is recirculated to the intake side as exhaust gas recirculation. In the engine, the required boost pressure is calculated from the operating conditions of the diesel engine, and the throttle opening of the premixed combustion engine is controlled until the required boost pressure is reached.

According to a fifth aspect of the invention, which is mainly based on the fourth aspect, the EGR of the diesel engine is determined according to the rotational speed and the output torque.
The required amount of gas is calculated, the throttle opening of the premixed combustion engine that matches the required amount of EGR gas is calculated, and the EGR valve opening is controlled based on the throttle opening set from the required boost pressure.

In the sixth aspect of the present invention, the rotation speed and output torque fluctuate according to the load, the accelerator, etc., and the exhaust gas of a premixed combustion engine such as a gasoline engine is recirculated to the intake side as exhaust gas recirculation. In a diesel engine, the required amount of EGR gas of the diesel engine is calculated according to the rotation speed and output torque, and the boost pressure to the diesel engine and the oxygen amount or temperature of the intake air to the diesel engine are measured and The mixed combustion engine supplies the required amount of EGR gas to the diesel engine.

[0011]

According to the above construction, since SO2 and soot are not mixed in the exhaust gas purified by the three-way catalyst from the gasoline engine, H2 S
O4 does not enter. Therefore, the durability of the engine is improved without damaging the tappet, the camshaft and the like. Also,
Exhaust gas from the gasoline engine is supplied with the required speed controlled according to the driving conditions of the diesel engine, that is, the diesel engine, because the rotational speed of the gasoline engine is controlled separately from the diesel engine. Therefore, the amount of NOx generated is suppressed to a low amount accordingly. In addition, the response of the gasoline engine is improved because it is controlled by the valve, and when the required amount of supply is insufficient for the valve opening amount, the rotation speed of the gasoline engine is changed to handle it, so a wide range of control is possible. It is possible. Further, the oxygen concentration was measured from the amount of air supplied to the diesel engine, and the EGR rate γ [γ = (oxygen concentration Oa in the air in the atmosphere Oa
Since the oxygen concentration in the air to be supplied Oin) / (the oxygen concentration in the air in the atmosphere Oa)] is obtained and controlled, the control can be performed accurately. Further, by measuring the temperature to be supplied, the EGR rate γ [γ = specific heat of the outside air Cpnew × (temperature of the outside air Tnew-temperature Tin to be supplied to the diesel engine) / specific heat of exhaust gas from a premixed combustion engine such as a gasoline engine Cpegr × (temperature Te of mixed air
gr-Temperature Tin supplied to the diesel engine]] for control, Cpnew and Cpegr can be controlled by simple equations as constants.

[0012]

The hybrid EGR according to the present invention will be described below.
Embodiments of the control device and the control method thereof will be described in detail with reference to the drawings. FIG. 1 shows an overall system diagram showing a first embodiment or a second embodiment of a hybrid EGR control device of the present invention. In FIG. 1, the hybrid EGR control device 1 includes a diesel engine unit 10, a gasoline engine unit 30, and a control unit 40. The diesel engine unit 10 includes a diesel engine 11, an air cleaner 12, a supercharger 13,
It is composed of an intercooler 14 and an exhaust muffler 15. In the diesel engine unit 10, in the air supply circuit to the diesel engine 11 (shown by the one-dot chain line A in FIG. 1), the air cleaner 12 to the blower 13a of the supercharger 13, the compressor 32 described later, and the intercooler. 14 is provided, and the air cleaner 12 removes dust in the supply air, and the blower 13
a, and is pressurized by the compressor 32, cooled by the intercooler 14, and sent to the diesel engine 11. Exhaust gas from a gasoline engine 31, which will be described later, is added to the supply air between the air cleaner 12 and the blower 13a. The supercharger 13 can be omitted if the required intake pressure is low.

In the exhaust circuit of the exhaust gas from the diesel engine 11 (shown by the thick solid line B in FIG. 1), the supercharger 13 is provided.
The turbine 13b and the exhaust muffler 15 are provided. Further, in this embodiment, an exhaust pipe 34 from a gasoline engine 31, which will be described later, merges with the pipe 16 at a point (a) between the turbine 13b and the exhaust muffler 15. In the exhaust gas exhaust circuit, the blower 13a is driven by the exhaust gas in the turbine 13b of the supercharger 13, and the exhaust muffler 1
In No. 5, noise is reduced. A fuel injection pump 21 is arranged in the diesel engine 11 and injects fuel from a fuel tank (not shown) into the cylinder chamber 11a of the diesel engine 11. Further, the fuel injection pump 21 has a rack 2 controlled by an accelerator lever or the like (not shown).
2 is arranged to increase or decrease the injection amount to the diesel engine 11. The position of the rack 22 is detected by a position sensor 43 described later and transmitted to a control unit 40 described later.

The gasoline engine section 30 comprises a gasoline engine 31, a compressor 32 driven by the gasoline engine 31, a three-way catalyst 33, and an EGR valve 35. In the gasoline engine unit 30, an air cleaner 12 common to the diesel engine 11 is arranged in the air supply circuit to the gasoline engine 31,
The air cleaner 11 removes dust in the supply air and sends it to the gasoline engine 31.

In the exhaust circuit of the exhaust gas from the gasoline engine 31 (shown by the thick dotted line C in FIG. 1), the three-way catalyst 33 is used.
And the EGR valve 35 is arranged, and the three-way catalyst 33 is used for NO.
Part of the exhaust gas from the gasoline engine 31 from which x has been removed (the required amount to be supplied is hereinafter referred to as the EGR gas amount) passes through the EGR valve 35, and after passing, from the air cleaner 12 to the diesel engine 11 described above. It is joined with the intake air through the pipe 17 (confluence point B) of the supply circuit to the. The remaining exhaust gas from the gasoline engine 31 joins the pipe 16 connected between the turbine 13b and the exhaust muffler 15 through the pipe 34, enters the exhaust muffler 15, is reduced in noise, and is discharged to the outside air. The amount of EGR gas passing through the EGR valve 35 depends on the diesel engine 1
It is controlled by a command from the control unit 40 described later according to the required amount of 1.

The gasoline engine 31 is provided with a carburetor 36, and the carburetor 36 controls the opening / closing amount of a throttle valve (not shown) in response to a command from the control unit 40 to feed gasoline from a fuel tank (not shown) to the gasoline engine 31. Is supplied to the diesel engine 11 to control the rotation speed to generate exhaust gas to be supplied to the diesel engine 11 and
1 drives the compressor 32 which pressurizes the air pressure supplied to 1. The three-way catalyst 33 purifies carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) in the exhaust gas from the gasoline engine 31.

The controller 40 of the first embodiment shown in FIG. 1 includes a controller 41, a speed sensor 42 for detecting the rotation speed of the diesel engine 11, and a diesel engine 11
Position sensor 43 that detects the position of the rack 22 that controls the injection amount of fuel to the diesel engine 11, a pressure sensor 44 that measures the intake pressure of the air that is supplied to the diesel engine 11, and an oxygen concentration in the air that is supplied to the diesel engine 11. It is composed of an oxygen sensor 45 for measuring.

The engine speed (Nrpm) of the diesel engine 11, the fuel injection amount (Ll / min) and the boost pressure Po of the air supplied to the diesel engine 11 are input to the controller 41. By controlling the opening / closing amount of the valve 35, the EGR valve 35 is controlled according to the required amount of the diesel engine 11.
The amount of EGR gas that passes through is controlled. Also, EGR
When the opening amount of the valve 35 is maximum and the required amount of EGR gas for the diesel engine 11 is insufficient, a command is sent to the carburetor 36 of the gasoline engine 31,
The rotational speed of the gasoline engine 31 is increased by controlling the opening / closing amount of a throttle valve (not shown). Further, the diesel engine 11 is provided with a speed sensor 42 for detecting the rotation speed of the engine, and measures the rotation speed of the engine. The pressure sensor 44 is arranged between the compressor 32 and the intercooler 14 and measures the air pressure supplied to the diesel engine 11. Further, an oxygen sensor 45 is arranged between the compressor 32 and the intercooler 14, and the diesel engine 1
The oxygen concentration in the air supplied to No. 1 is measured.

Next, the operation of the above-mentioned structure will be described with reference to FIG.
The first embodiment of the flowchart of FIG. First, in step 1, the position sensor 43 attached to the fuel injection pump 21 of the diesel engine 11 is attached to the controller 41.
The fuel injection amount (Ll / min) detected at is input. In step 2, the engine rotation speed (N rpm) of the diesel engine 11 detected by the speed sensor 42 attached to the diesel engine 11 is input. In step 3, in the controller 41, as shown in FIG.
The required air pressure to be supplied to the diesel engine 11 according to the engine speed N and the fuel injection amount L, that is, the boost pressure Po is obtained from the map as shown in FIG. In step 4, the pressure sensor 44 measures the air pressure of the air pressurized by the compressor 32 supplied to the diesel engine 11, that is, the current boost pressure Pa. In step 5, the controller 41 compares the boost pressure Po obtained from the map with the currently measured boost pressure Pa, and drives the compressor 32 so that the boost pressure Po and the currently measured boost pressure Pa match. A command is output to the carburetor 36 of the gasoline engine 31. The gasoline engine 31 increases / decreases the rotation speed according to a command from the control unit 40, and the diesel engine 1
Increase or decrease the air pressure supplied to 1. In the above,
Although the air pressure supplied is adjusted by the rotation speed of the compressor 32, a variable pressure valve may be mounted to adjust the pressure according to a command from the controller.

In step 6, step 1 and step 2
The EGR gas rate supplied to the diesel engine 11 according to the engine rotation speed N and the fuel injection amount L in the controller 41 based on the engine rotation speed N and the fuel injection amount L input in Ask for Eo. In step 7, the oxygen sensor 45 determines the oxygen concentration Oin in the air supplied to the diesel engine 11, and the controller 41 determines the current EGR gas rate Eo.
To calculate. In step 8, in the controller 41, the EGR gas rate Eo obtained from the map and the current EGR
When the EGR gas rate Eo calculated from the map is compared with the gas rate Eo and is smaller than the current EGR gas rate Eo, the procedure goes to step 9, where the controller 41 causes the EGR valve 35
Outputs a command to move the valve in the closing direction. As a result, when the amount of EGR gas passing through the EGR valve 35 decreases, the oxygen concentration in the air supplied to the diesel engine 11 increases and the current EGR gas rate Eo decreases, which matches the EGR gas rate Eo obtained from the map. You can do it.

When the EGR gas rate Eo obtained from the map in step 8 is larger than the current EGR gas rate Eo, the process goes to step 10 and the controller 41 outputs a command to the EGR valve 35 to move the valve in the direction to open it. As a result, the amount of EGR gas passing through the EGR valve 35 increases, the oxygen concentration in the air supplied to the diesel engine 11 decreases, and the current EGR gas rate Eo increases, and the EGR gas rate Eo determined from the map If the gasoline EGR valve 35 is open, check this step.
At 1, the EGR gas rate Eo and the current EGR gas rate Eo are equal or not compared. If the values are the same in step 11, go to step 12 and continue the operation. Step 1
If it is not equal to 1, that is, if the EGR gas rate Eo and the current EGR gas rate Eo do not match even if the gasoline EGR valve 35 is fully opened, go to step 13 and throttle the gasoline engine 31, that is, vaporize. The opening / closing amount of a throttle valve (not shown) of the container is controlled. At this time, the boost pressure Pa obtained in step 5 does not match the throttle that matched, and priority is given to matching the EGR gas rate. After changing the throttle, the process returns to step 8 and the EGR gas ratio Eo obtained from the map and the current EG
The R gas rate Eo is compared and the opening / closing of the valve is controlled again.

In FIG. 1, in the control unit 40 of the second embodiment, temperature sensors 46, 47, 48 are used instead of the oxygen sensor 45 for measuring the oxygen concentration in the air supplied to the diesel engine 11 of the first embodiment. Is provided.
The first temperature sensor 46 includes an air cleaner 12 and an EGR.
The temperature of the outside air passing through the air cleaner 12 supplied to the diesel engine 11 is arranged between the valve 35 and the confluence point (b). Second temperature sensor 47
Is arranged downstream of the confluence point (b) with the gasoline EGR valve 35, and measures the intake temperature of the mixed air of the outside air and the exhaust gas that has passed through the EGR valve 35 from the gasoline engine 31. The third temperature sensor 48 is arranged between the three-way catalyst 33 and the EGR valve 35 and measures the temperature of the exhaust gas from the gasoline engine 31.

The operation of the second embodiment having the above-mentioned structure will be described. In the flowchart of the first embodiment shown in FIG. 2, the oxygen sensor 45 at step 7 causes the oxygen concentration in the air supplied to the diesel engine 11 to be increased. Although the current EGR gas rate Eo was calculated in the control unit 40 by obtaining Oin, in the second embodiment, the current EGR gas rate Eo is calculated in the controller 41 by measuring the temperature of the air supplied to the diesel engine 11. are doing. Since the other points are the same as those in the first embodiment, detailed description will be omitted. Although the EGR valve 35 is provided to control the current EGR gas rate Eo in the above-described embodiment, the rotation speed of the gasoline engine is directly controlled by a command from the controller to the carburetor to control the amount of exhaust gas supplied. It may be done.

[0024]

As described above, according to the present invention,
Since exhaust gas that does not contain SO2 and soot of a premixed combustion engine such as a gasoline engine is supplied into the diesel engine, the tappet, the camshaft, etc. are not damaged and the engine durability is improved. Also, since the EGR rate can be easily changed depending on the engine load,
The excellent effect is that even if the output of the engine changes, it can be easily dealt with. Further, the responsiveness is improved by controlling the valve, and the required amount of supply is controlled by changing the rotation speed of the gasoline engine, so that a wide range of control is possible and the control can be performed with a simple configuration. .

[Brief description of drawings]

FIG. 1 is an overall system diagram showing a first embodiment or a second embodiment of a hybrid EGR control device of the present invention.

FIG. 2 is a flowchart of the present invention.

FIG. 3 is a diagram for obtaining a necessary boost pressure Po to be supplied to a diesel engine according to an engine speed N and a fuel injection amount L.

FIG. 4 is a diagram for obtaining an EGR gas rate Eo supplied to a diesel engine according to an engine speed N and a fuel injection amount L.

[Explanation of symbols]

1 ... Hybrid EGR control device, 10 ... Diesel engine section, 11 ... Diesel engine, 12 ...
... Air cleaner, 13 ... Supercharger, 13a ... Blower, 13b ... Turbine, 14 ... Intercooler, 1
5 ... Exhaust muffler, 21 ... Fuel injection pump, 22 ...
… Rack, 30 …… Gasoline engine part, 31 …… Gasoline engine valve, 32 …… Compressor, 33 ……
3-way catalyst, 35 ... EGR valve, 36 ... Vaporizer, 4
0 ... control unit, 41 ... controller, 42 ... speed sensor, 43 ... position sensor, 44 ... pressure sensor,
45 ... Oxygen sensor, 46, 47, 48 ... Temperature sensor.

Claims (6)

[Claims] 1. In a diesel engine in which exhaust gas of a premixed combustion engine such as a gasoline engine is recirculated to the intake side as exhaust gas recirculation, a compressor for diesel engine supercharging is driven by the premixed combustion engine. Control device for hybrid EGR. 2. A diesel engine in which the rotational speed and output torque fluctuate according to load, accelerator, etc., and exhaust gas of a premixed combustion engine such as a gasoline engine is recirculated to the intake side as exhaust gas recirculation, EGR valve that controls the flow rate of exhaust gas from the premixed combustion engine to the diesel engine, position sensor that detects the fuel injection amount to the diesel engine, speed sensor that detects the rotational speed of the diesel engine, and signals from both sensors And a control device that receives the required exhaust gas flow rate and outputs a command to the EGR valve.
GR control device. 3. A diesel engine in which the rotational speed and output torque fluctuate according to load, accelerator, etc., and exhaust gas of a premixed combustion engine such as a gasoline engine is recirculated to the intake side as exhaust gas recirculation, Driven by a premixed combustion engine, a compressor that supercharges intake air to the diesel engine, a position sensor that detects the fuel injection amount to the diesel engine, a speed sensor that detects the rotation speed of the diesel engine, and both sensors And a control device that outputs a command for varying the rotation speed to the premixed combustion engine in response to the above signal. 4. A diesel engine in which the rotational speed and output torque fluctuate according to load, accelerator, etc., and exhaust gas of a premixed combustion engine such as a gasoline engine is recirculated to the intake side as exhaust gas recirculation, A hybrid EGR control method comprising calculating a required boost pressure from operating conditions of a diesel engine and controlling a throttle opening of a premixed combustion engine until the required boost pressure is reached. 5. The required amount of EGR gas for a diesel engine is calculated according to the rotational speed and output torque, and the throttle opening of the premixed combustion engine that matches the required amount of EGR gas is calculated according to claim 4. A hybrid EGR control method for controlling an EGR valve opening based on a throttle opening set from boost pressure. 6. A diesel engine in which the rotational speed and output torque fluctuate according to load, accelerator, etc., and exhaust gas of a premixed combustion engine such as a gasoline engine is recirculated to the intake side as exhaust gas recirculation, Rotational speed,
The required amount of EGR gas for the diesel engine is calculated according to the output torque, and the boost pressure to the diesel engine and the oxygen amount or temperature of the intake air to the diesel engine are measured to change the premixed combustion engine to the diesel engine. A hybrid EGR control method comprising supplying a required amount of EGR gas.