JPH0763121A - Exhaust gas reflux controller of internal combustion engine - Google Patents

Abstract

PURPOSE:To maintain an exhaust gas reflux quantity most suitably for the operation state of an engine even in the case of foreign matters or the like having been piled up in an exhaust gas reflux pipe. CONSTITUTION:This controller possesses a reflux quantity detecting means 43 to detect an actual exhaust gas reflux quantity; and a controlling means 50 that memorizes an exhaust gas reflux quantity most suitable for the operation state of an engine and compares an actual exhaust gas reflux quantity detected by means of the reflux quantity detecting means 43 with the optimum exhaust gas reflux quantity and controls, on the basis of its result, the displacement of an exhaust gas reflux control valve 26. Preferably, the reflux quantity detecting means 43 is made up of a valve displacement detecting means 39 and a pressure difference detecting means 42.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation control device for an internal combustion engine, which recirculates the exhaust gas into an intake system of the internal combustion engine to regulate the combustion temperature and suppress the generation of harmful components in the exhaust gas.

[0002]

2. Description of the Related Art Conventionally, as an exhaust gas recirculation control device for this type of internal combustion engine, a device disclosed in Japanese Patent Publication No. 4-75388 is known. This is an exhaust gas recirculation pipe that recirculates the exhaust gas in the exhaust pipe into the intake pipe, an exhaust gas recirculation control valve disposed in the middle of the exhaust gas recirculation pipe, and a lift sensor that measures the actual displacement amount of the exhaust gas recirculation control valve, The actual displacement measured by the lift sensor is compared with the displacement of the exhaust gas recirculation control valve that is optimal for the engine operating conditions such as the temperature sensor, negative pressure sensor, and engine speed sensor, and exhaust gas recirculation control is performed based on that result. And a control means for controlling the amount of displacement of the valve.

[0003]

However, in the above-mentioned device, the actual displacement amount of the exhaust gas recirculation control valve measured by the lift sensor is compared with the displacement amount of the exhaust gas recirculation control valve which is optimum for the operating condition of the engine. Since the displacement amount of the exhaust gas recirculation control valve is controlled based on the result, foreign matter is accumulated in the exhaust gas recirculation pipe and the actual exhaust gas recirculation amount is less than the optimum exhaust gas recirculation amount for the engine operating condition. However, it cannot be detected and the displacement amount of the exhaust gas recirculation control valve cannot be increased. As a result, it becomes impossible to maintain the optimum exhaust gas recirculation amount for the operating condition of the engine, and harmful components (especially NO _x ) in the exhaust gas
May increase.

Therefore, it is a technical object of the present invention to maintain the optimum exhaust gas recirculation amount for the operating condition of the engine even when foreign matters or the like are accumulated in the exhaust gas recirculation pipe.

[0005]

The technical measures taken in the present invention to solve the above technical problems are a recirculation amount detecting means for detecting an actual exhaust gas recirculation amount, and an exhaust gas optimum for an engine operating state. And a control unit that stores the recirculation amount, compares the actual exhaust gas recirculation amount detected by the recirculation amount detection unit with the optimum exhaust gas recirculation amount, and controls the displacement amount of the exhaust gas recirculation control valve based on the result. That's what I did.

Preferably, the recirculation amount detecting means is a valve displacement amount detecting means for detecting the displacement amount of the exhaust gas recirculation control valve, the exhaust gas recirculation pipe on the exhaust pipe side of the exhaust gas recirculation control valve and the intake air of the exhaust gas recirculation control valve. And a differential pressure detecting means for detecting a pressure difference between the exhaust gas recirculation pipe on the pipe side.

[0007]

According to the first technical means, the optimum exhaust gas recirculation amount is stored in the engine operating state, and the actual exhaust gas recirculation amount detected by the recirculation amount detecting means is compared with the optimum exhaust gas recirculation amount. Then, the displacement amount of the exhaust gas recirculation control valve is controlled based on the result, so that it operates as follows.

When the actual exhaust gas recirculation amount detected by the recirculation amount detection means is larger than the optimum exhaust gas recirculation amount, the control means reduces the displacement amount (opening) of the exhaust gas recirculation control valve to determine the actual exhaust gas recirculation amount. Match the optimum exhaust gas recirculation amount. On the other hand, when the actual exhaust gas recirculation amount is smaller than the optimum exhaust gas recirculation amount, the control unit increases the displacement amount (opening) of the exhaust gas recirculation control valve to match the actual exhaust gas recirculation amount with the optimum exhaust gas recirculation amount. Therefore, even if foreign matter accumulates in the exhaust gas recirculation pipe and the actual exhaust gas recirculation amount becomes smaller than the optimum exhaust gas recirculation amount, the control device increases the displacement amount of the exhaust gas recirculation control valve to increase the actual exhaust gas recirculation amount. Is matched with the optimal exhaust gas recirculation amount, so that it is possible to maintain the optimal exhaust gas recirculation amount for the operating state of the engine. As a result, even if foreign matter or the like is deposited in the exhaust gas recirculation pipe, it is possible to reliably suppress the generation of harmful components (particularly NO _x ) in the exhaust gas.

If the recirculation amount detecting means is composed of the valve displacement amount detecting means and the differential pressure detecting means, the valve displacement detecting means detects the opening area of the exhaust gas recirculation control valve and the differential pressure detecting means detects the inside of the exhaust gas recirculation pipe. The exhaust gas flow rate is detected, and the actual recirculation amount is detected from the opening area and the exhaust gas flow rate.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of an exhaust gas recirculation control system for an internal combustion engine according to this embodiment.

In an exhaust gas recirculation control system 10 for an internal combustion engine shown in FIG. 1, a throttle valve 12 is provided in the middle of an intake pipe 11, and the amount of intake air to the internal combustion engine 13 is controlled by controlling the opening of the throttle valve 12. To be done. The opening of the throttle valve 12 is detected by a throttle opening sensor 14. A surge tank 15 for suppressing intake pulsation is formed downstream of the throttle valve 12, and an intake pressure sensor 16 is connected to the surge tank 15. The surge tank 15 can communicate with a combustion chamber 18 of the internal combustion engine 13 via an intake valve 17, and the combustion chamber 18 is formed by a piston 20 slidably arranged in a cylinder block 19. An ignition plug 21 is provided in the combustion chamber 18 so as to face it.

Further, the internal combustion engine 13 is equipped with a water temperature sensor 22 for detecting the temperature of cooling water of the internal combustion engine.

The combustion chamber 18 is connected to the exhaust pipe 2 via an exhaust valve 23.
4 is connected to the exhaust pipe 24, and the exhaust pipe 2 is provided in the middle of the exhaust pipe 24.
An exhaust gas recirculation pipe 25 is connected to recirculate the exhaust gas in 4 to the surge tank 15. An exhaust gas recirculation control valve (hereinafter referred to as an EGR valve) 2 is provided in the middle of the exhaust gas recirculation pipe 25.
6 is installed. The EGR valve 26 is divided by a valve seat 27 formed in the middle of the exhaust gas recirculation pipe 25, a needle valve body 28 that can be attached to and detached from the valve seat 27, a diaphragm 29 connected to the needle valve body 28, and a diaphragm 29. The negative pressure chamber 30 and the atmospheric chamber 31 are formed, and a spring 32 disposed in the negative pressure chamber 30 for urging the needle valve body 28 in a direction to seat it on the valve seat 27.

The negative pressure chamber 30 of the EGR valve 26 communicates with the output port 34 of the duty control valve 33, and the opening of the duty control valve 33 is duty controlled by a control means (hereinafter referred to as ECU) 50 which will be described later. The negative pressure corresponding to the duty ratio is supplied to the negative pressure chamber 30 of the EGR valve 26. On the other hand, the duty control valve 33
The input port 35 of is the output port 37 of the regulator 36.
The input port 38 of the regulator 36 communicates with the surge tank 15. This regulator 3
6 is for converting the intake negative pressure in the surge tank 15 into a predetermined negative pressure, and the predetermined negative pressure is the duty control valve 3
3 is supplied to the input port 35.

The EGR valve 26 is equipped with a stroke sensor (valve displacement amount detecting means) 39 for detecting a displacement amount (that is, an opening degree) of the EGR valve 26, and a detection signal of the stroke sensor 39 is input to the ECU 50 described above. ing. EGR
A first pressure detection port 40 is formed in the exhaust gas recirculation pipe 25 on the exhaust pipe 24 side (that is, the upstream side of the EGR valve 26) with respect to the valve 26, and the intake pipe 11 side (that is, EG) with respect to the EGR valve 26.
A second pressure detection port 41 is formed in the exhaust gas recirculation pipe 25 on the downstream side of the R valve 26. First pressure detection port 4
A differential pressure sensor (differential pressure detection means) 42 is connected to the 0 and second pressure detection ports 41, and the differential pressure sensor 42 causes E
A pressure difference (differential pressure) between the upstream side of the GR valve 26 and the downstream side of the EGR valve 26 is detected. The detection signal of the differential pressure sensor 42 is input to the ECU 50. Here, the opening area of the exhaust gas recirculation pipe 25 can be determined by the detection signal of the stroke sensor 39, and the flow velocity of the exhaust gas in the exhaust gas recirculation pipe 25 can be determined by the detection signal of the differential pressure sensor 42. The actual amount of exhaust gas recirculation inside can be detected. Therefore, the stroke sensor 39 and the differential pressure sensor 42 constitute the recirculation amount detecting means 43.

The ECU 50 includes an intake negative pressure detected by the intake pressure sensor 16 and an engine speed sensor (not shown).
The operating state of the engine such as the engine speed detected by the engine is input, and the ECU 50 previously inputs the optimal recirculation amount for the operating state of the engine, the optimal duty ratio of the duty control valve 33, and the optimal displacement amount of the EGR valve 26. Are stored as a map. Here, it is assumed that the optimum recirculation amount for the operating state of the engine is larger than the lower limit value of the recirculation amount and smaller than the upper limit value of the recirculation amount. Further, when the recirculation amount is below the lower limit value, the generation of harmful components in the exhaust gas increases, and when it is above the recirculation amount upper limit value, there is a risk of misfire in the combustion chamber 18. ECU
Reference numeral 50 compares the actual recirculation amount detected by the above-mentioned recirculation amount detection means 43 with the optimum recirculation amount for the operating state of the engine, and changes the duty ratio of the duty control valve 33 based on the result. The amount of displacement of the valve 26 is controlled.

The differential pressure sensor 42 will be briefly described with reference to FIG. The differential pressure sensor 42 shown in FIG. 2 has a first port 44 into which the high pressure of the first pressure detection port 40 is introduced.
Housing 45 having a second pressure detection port 4
Second with a second port 46 into which a low pressure of 1 is introduced
And a housing 47. The first housing 45 is fixed to the second housing 47, and the outer peripheral edge of the diaphragm 48 is supported by the fixed portion. The diaphragm 48 forms a high pressure chamber 49 that communicates with the first port 44 and a low pressure chamber 51 that communicates with the second port 46. The diaphragm 48 has a first rod 53 through the retainer 52.
Are connected. On the other hand, a third housing 56 is fixed to the second housing 47 via bolts 55, and a second rod 54 is disposed inside the third housing 56 so as to be slidable in the left-right direction in the drawing. The left end of the second rod 54 in the drawing is engageable with the first rod 53, and a movable member 57 made of resin is fixed to the right end of the second rod 54 in the drawing, and is biased to the left in the drawing by a spring 60. Has been done. A brush 58 is arranged on the movable member 57, and the brush 58 is movable on a potentiometer 59. The potentiometer 59 is connected to the terminal 61 so that the voltage can be taken out to the outside.

The operation of the differential pressure sensor 42 constructed as described above will now be described. The pressure of the exhaust gas recirculation pipe 25 on the upstream side of the EGR valve 26 is supplied to the high pressure chamber 49 via the first port 44, and the pressure of the exhaust gas recirculation pipe 25 on the downstream side of the EGR valve 26 via the second port 46. Low pressure chamber 5
1, the diaphragm 48 bends to the right in the figure, and the first and second rods 53 and 54 and the movable member 57 are moved by the spring 60 by an amount corresponding to the pressure difference between the high pressure chamber 49 and the low pressure chamber 51. It moves to the right in the figure against the biasing force. As a result, the brush 58 moves on the potentiometer 59 by an amount corresponding to the differential pressure between the high pressure chamber 49 and the low pressure chamber 51, so that the voltage corresponding to the differential pressure between the high pressure chamber 49 and the low pressure chamber 51 is applied to the terminal 61. It is output to the ECU 50 via the. As described above, the differential pressure between the upstream side and the downstream side of the EGR valve 26 is detected.

The operation of the exhaust gas recirculation control device 10 for an internal combustion engine configured as described above will be described with reference to FIG.

First, the engine speed is detected in step S1 and the intake negative pressure is detected in step S2. That is, the operating state of the engine is detected in steps S1 and S2. Next, in step S3, the duty ratio Dut of the duty control valve 33 that is optimum for the operating state of the engine stored in the map of the ECU 50 is obtained.
y (MAP), optimum exhaust gas recirculation amount Q _MAX (MAP) ≤
Q (MAP) ≦ Q _MIN (MAP) and optimum EGR valve 2
The displacement amount St (MAP) of 6 is referred to, and if the optimum duty ratio Duty (MAP) is zero in step S4, the process returns to step S1 and the optimum duty ratio Duty.
If (MAP) is not zero, the process proceeds to step S5. Here, the optimum duty ratio Duty (MAP) is zero,
This means that the EGR valve 26 is fully closed, that is, outside the EGR operating range.

In step S5, the stroke sensor 3
9 and the differential pressure sensor 42 detect the actual exhaust gas recirculation amount Q, and in step S6 the actual exhaust gas recirculation amount Q is compared with the optimum exhaust gas recirculation amount Q (MAP). That is,
In step S6, the actual exhaust gas recirculation amount Q is Q
_{If MAX} (MAP) ≤ Q ≤ Q _MIN (MAP), the process returns to step S1 and the actual exhaust gas recirculation amount Q is Q _MAX (MA
P) ≦ Q ≦ Q _MIN (MAP), the process proceeds to step S7. In step S7, the duty ratio Duty of the duty control valve 33 is changed.

If the duty ratio Duty changed in step S8 is not the upper limit (100%) or the lower limit (0%), the process returns to step S5, the actual recirculation amount Q is detected again, and the actual exhaust gas return is detected in step S6. Flow rate Q is Q
Steps S5 to S8 are repeated until _MAX (MAP) ≦ Q ≦ Q _MIN (MAP). Therefore, the changed duty ratio Duty is the upper limit (100%) or the lower limit (0
%), The actual exhaust gas recirculation amount Q finally becomes Q _MAX (MAP) ≦ Q ≦ Q _MIN (MAP), which is the optimum exhaust gas recirculation amount for the engine operating condition.

On the other hand, the duty ratio Duty changed in step S8 is the upper limit (100%) or the lower limit (0
%), The control becomes impossible and the driver is warned of the abnormality in step S9.

As shown above, in this embodiment,
When the actual exhaust gas recirculation amount detected by the recirculation amount detection means 43 is larger than the allowable range of the optimum exhaust gas recirculation amount, E
The displacement amount of the EGR valve 26 is reduced by the CU 50 to match the actual exhaust gas recirculation amount with the optimum exhaust gas recirculation amount. On the other hand, when the actual exhaust gas recirculation amount is smaller than the allowable range of the optimal exhaust gas recirculation amount, the ECU 50 increases the displacement amount (opening) of the EGR valve 26 to match the actual exhaust gas recirculation amount with the optimal exhaust gas recirculation amount. . Therefore, the exhaust gas recirculation pipe 25
Even if foreign matter accumulates inside the exhaust gas and the actual amount of exhaust gas recirculation falls below the optimum allowable range of exhaust gas recirculation, EC
It is possible to increase the duty ratio by U50 and increase the displacement amount of the EGR valve 26 so that the actual exhaust gas recirculation amount matches the optimum exhaust gas recirculation amount. Therefore, even if foreign matter or the like accumulates in the exhaust gas recirculation pipe, it is possible to maintain the exhaust gas recirculation amount that is optimal for the engine operating condition, and reliably suppress the generation of harmful components (particularly NO _x ) in the exhaust gas. be able to.

[0026]

The present invention has the following effects.

Even if a foreign substance or the like is deposited in the exhaust gas recirculation pipe, it is possible to reliably suppress the generation of harmful components (particularly NO _x ) in the exhaust gas.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an exhaust gas recirculation control device for an internal combustion engine according to a present embodiment.

FIG. 2 is a sectional view of a differential pressure sensor (differential pressure detection means) according to the present embodiment.

FIG. 3 is a flowchart illustrating the operation of an exhaust gas recirculation control device for an internal combustion engine according to this embodiment.

[Explanation of symbols]

 10 Exhaust Gas Recirculation Control Device for Internal Combustion Engine 11 Intake Pipe 24 Exhaust Pipe 25 Exhaust Gas Recirculation Pipe 26 EGR Valve (Exhaust Gas Recirculation Control Valve) 39 Stroke Sensor (Valve Displacement Detecting Means) 42 Differential Pressure Sensor (Differential Pressure Detecting Means) 43 Recirculation Quantity Detection means 50 ECU (control means)

Claims (2)

[Claims] 1. An exhaust gas recirculation control device for an internal combustion engine, comprising: an exhaust gas recirculation pipe for recirculating exhaust gas in an exhaust pipe of the internal combustion engine into an intake pipe; and an exhaust gas recirculation control valve arranged in the middle of the exhaust gas recirculation pipe. An exhaust gas recirculation amount detecting means for detecting an actual exhaust gas recirculation amount and an optimal exhaust gas recirculation amount for the engine operating state are stored, and the actual exhaust gas recirculation amount detected by the recirculation amount detecting means and the optimum exhaust gas recirculation amount. And a control means for controlling the amount of displacement of the exhaust gas recirculation control valve based on the result of the comparison. 2. The recirculation amount detection means, a valve displacement amount detection means for detecting a displacement amount of the exhaust gas recirculation control valve, the exhaust gas recirculation pipe on the exhaust pipe side of the exhaust gas recirculation control valve, and the exhaust gas recirculation control. The exhaust gas recirculation control device for an internal combustion engine according to claim 1, further comprising: a differential pressure detection means that detects a pressure difference between the exhaust gas recirculation pipe on the intake pipe side of the valve.