JP2600521B2 - Failure diagnosis device for exhaust gas recirculation control device - Google Patents

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 recirculating a part of exhaust gas from an internal combustion engine to an intake pipe of the internal combustion engine, and more particularly to a failure diagnosis for diagnosing a failure of the exhaust gas recirculation control device. It concerns the device.

[0002]

2. Description of the Related Art Conventionally, NOx in exhaust gas of an internal combustion engine has been known.
As a means for reducing (nitrogen oxides), an exhaust gas recirculation control device (hereinafter, EGR control device) for controlling exhaust gas recirculation (hereinafter, EGR) is widely used. This EGR control device is a BPT (Back Pressure Transducer)
EGR is controlled by an exhaust pressure control method using a valve. That is, the passage area of the EGR control valve (hereinafter, EGR valve) is controlled by the BPT valve so that the EGR flow rate becomes a predetermined value.
In a system using a VT (Venturi Vaccum Transducer) valve and a system in which the control pressure of an EGR valve is controlled using a solenoid, the passage area of the EGR valve is controlled similarly to the system using the BPT valve described above. It has become.

[0003] Incidentally, as a method for diagnosing such a failure of the EGR control device, a conventional method disclosed in Japanese Patent Application Laid-Open No. Sho 62-5174 is known.
An apparatus as disclosed in Japanese Patent Laid-Open Publication No. 6-2006 has been proposed. That is, this device is operated when the EGR flow rate is present (EGR
(When ON), the intake air pressure in the intake manifold, that is, the intake manifold pressure value and the intake manifold pressure value when the EGR flow rate does not exist (when the EGR is OFF) are detected, and when the pressure difference is outside a predetermined range, an alarm is issued. This is to output.

[0004]

However, in such a conventional EGR control device that controls the EGR flow rate by making the passage area of the EGR valve variable, the EGR flow rate is originally small in a region where the intake air amount is small. / O
The intake manifold pressure difference at the FF becomes small, and failure determination becomes difficult. Also, when the intake air amount is large (or the intake manifold pressure (absolute pressure) is high or the exhaust pressure (absolute pressure) is high), the EGR flow difference between ON / OFF of EGR becomes large, but the intake manifold pressure difference becomes Since the EGR flow rate is large, the flow rate becomes small due to the pressure loss in the return line. Therefore, there has been a problem that it is difficult to determine a failure. Further, in a region where the EGR flow rate is large, the torque fluctuation at the time of ON / OFF of the EGR is large, so that there is a problem that the driver feels a shock due to drivability.

The present invention has been made in view of the above points, and has been made to solve the above-described problems.
It is an object of the present invention to provide a failure diagnosis device for an EGR control device that can increase the failure detection accuracy when detecting an abnormality in an EGR system when the abnormality is detected.

[0006]

In order to achieve the above object, a failure diagnosis apparatus according to the present invention comprises a recirculation pipe for recirculating exhaust gas of an internal combustion engine to an intake pipe, and a flow rate of the exhaust gas flowing through the recirculation pipe. And a recirculation valve passage area control means for controlling a passage area of the recirculation valve, and an EGR control device for recirculating a part of the exhaust gas through a recirculation pipe. Operating state detecting means for detecting, means for storing the first detection value detected by the operating state detecting means when the passage area of the recirculation valve is in the first state where the passage area of the recirculation valve is large, The valve passage area of the recirculation valve is small or zero by the valve passage area control means.
Means for storing a second detection value detected from the operating condition detecting means when a state, at least the first test
Determining means for performing a failure determination based on the output value and the second detection value .
The deviation between the first detection value and the second detection value is equal to or greater than a predetermined value.
The failure determination is performed within a predetermined area predicted to occur. In the failure diagnosis device according to another aspect of the present invention, in the above-described device, the determination means performs the failure determination in a region where the flow rate of the exhaust gas flowing through the return pipe is equal to or less than a predetermined value.

[0007]

According to the present invention, EGR is turned ON / OFF by EGR.
When an abnormality of the GR system is detected, the failure determination area is limited according to the load, so that a failure is detected in an EGR ON area and a large detection value area such as an EGR ON / OFF intake manifold pressure difference. it can. Further, in another aspect of the present invention, a failure is detected only when the EGR flow rate is equal to or less than a predetermined value, so that a torque fluctuation when the EGR is turned on / off can be reduced.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment when the present invention is applied to an EGR control device.
The case of an exhaust pressure control method using a T valve is shown. In FIG. 1, reference numeral 1 denotes an engine, 2 denotes an air cleaner, 3 denotes an intake pipe, 4 denotes an intake manifold, 5 denotes an injector for injecting fuel, and 6 denotes operating state detecting means for detecting an intake manifold pressure in the intake manifold 4. A pressure sensor, 7 is a throttle valve, and 8 is a throttle opening sensor for detecting the opening of the throttle valve 7. 9 is an ignition coil, 10 is an igniter, 11 is an exhaust pipe, 12 is a catalyst,
Reference numeral 13 denotes a water temperature sensor that detects the temperature of the cooling water of the engine 1.

Reference numeral 14 denotes a return pipe for returning a part of the exhaust gas in the exhaust pipe 11 to the intake pipe 3, and reference numeral 15 denotes the return pipe 14.
EG as a recirculation valve for controlling the flow rate of exhaust gas flowing through
An R valve 16 is a BPT valve for controlling a passage area of the EGR valve 15, and 17 is an EGR solenoid. The EGR solenoid 17 controls a control pressure to the BPT valve 16 and controls an EGR flow rate by the BPT valve 16. It is something to do. 21 is an electronic control unit, 22 is an ignition key switch (hereinafter referred to as IG)
Switches) and 23 are batteries, and 24 is a warning lamp for failure diagnosis.

Here, the EGR solenoid 17 is connected to a control passage 18 between the diaphragm chamber of the EGR valve 15 and the intake pipe 3, and is turned on / off by a signal from an electronic control unit 21 to the BPT valve 16. By controlling the control pressure of the EGR solenoid 1
When the switch 7 is turned off, the control pressure of the BPT valve 16 becomes the atmospheric pressure, and the EGR is cut off.

The electronic control unit 21 receives signals from the pressure sensor 6, the throttle opening sensor 8, the ignition coil 9 and the like as inputs, and when detecting a failure of the EGR system, the passage area of the EGR valve 15 is reduced. The first intake manifold pressure detected by the pressure sensor 6 when it is wide in the first state, that is, when it is ON, is stored, and the pressure is detected by the pressure sensor 6 when it is in the second state in which the passage area of the EGR valve 15 is small or zero, that is, when it is off. Remember the second intake manifold pressure,
A failure is determined based on these first and second intake manifold pressures. At the time of this failure determination, the EGR is performed in a predetermined area excluding a high load area where the intake manifold pressure of the load and the engine rotation are large in the pressure loss in the return pipe 14 and a low EGR flow rate area where the EGR flow rate flowing through the return pipe 14 is small, that is, a low load area. The system determines the failure of the system.

FIG. 2 is a detailed block diagram of the electronic control unit 21. In the figure, reference numeral 100 denotes a microcomputer, which performs EGR according to a predetermined program.
A CPU 200 for calculating a control amount of the solenoid 17; a free-running counter 201 for measuring a rotation cycle of the engine 1; a timer 202 for measuring a duty ratio of a drive signal applied to the EGR solenoid 17; A / D converter 203, input port 204, RAM 205 used as a work memory, ROM storing a program
206, an output port 207 for outputting a drive signal, a common bus 208, and the like.

Reference numeral 101 denotes a first input interface circuit for inputting a signal of the ignition coil 9 and the like, and 102 denotes a second input interface circuit.
This is an input interface circuit for inputting each signal of the pressure sensor 6, the throttle opening sensor 8 and the like and outputting the signal to the A / D converter 203. An output interface circuit 104 amplifies the drive output from the output port 207 and outputs the amplified drive output to the EGR solenoid 17. Reference numeral 105 denotes a power supply circuit to which the power of the battery 23 is supplied via the IG switch 22.
The control unit 21 is driven.

Next, the operation of the above embodiment will be described with reference to FIGS. FIG. 3 shows a relationship between the EGR rate controlled by the BPT valve of the EGR control system and the load, and shows a case where the EGR rate is controlled to be constant by the BPT valve 16. Here, the EGR rate is represented by EGR rate = EGR flow rate / (intake air quantity + EGR flow rate) × 100%. The loads are intake manifold pressure and engine speed. FIG. 4 shows the relationship between the ON / OFF intake manifold pressure difference of the EGR and the load. Here, the symbol A represents a region intake manifold pressure difference in the low EGR rate region A ₀ is less than relation to FIG. 3, the symbol B is also constant EGR rate range B ₀ even the intake air amount is small, the EGR flow rate represents less intake manifold pressure difference is small regions, further symbol C is a constant EGR rate in the EGR rate range C ₀ the high load region is large, represents an area intake manifold pressure difference is small because a large pressure loss in the return line ing.

However, according to the present invention, ON / OF of EGR is performed.
In a device for detecting an abnormality of the EGR system by F,
The failure determination of the EGR system is performed in a predetermined region D excluding the low EGR flow regions A and B where the GR flow is small and the high load region C where the loss in the recirculation pipe is large. The operation of the EGR system is shown in FIG. This will be described with reference to a failure determination flowchart.

That is, in FIG. 5, the CPU 200
When the engine 1 starts, first, at step 300, the EGR
Is in the ON area, and if it is in the ON area, the process proceeds to the next steps 301 and 302. This allows
In step 301, the intake manifold pressure Pb detected by the pressure sensor 6 is determined to be a predetermined value Pa set in advance corresponding to the low EGR flow rate regions A and B.
In 2, it is determined that the engine speed Ne is a predetermined value Nd which is also set corresponding to the low EGR flow rate region.

At this time, if those conditions are satisfied, it is determined that the load is not low, and the process proceeds to the next steps 303 and 304. Therefore, in step 303, the intake manifold pressure Pb is further determined to be a predetermined value Pc set corresponding to the high load region C, and in step 304, the engine speed Ne is determined.
Is determined to be a predetermined value Nf set corresponding to the high load region. As a result, if both conditions are satisfied, it is determined that the load is not high, the optimal region is limited by these processes, the EGR ON / OFF intake manifold pressure is detected, and a failure determination process is performed based on the intake manifold pressure. (Step 305).

As described above, according to the present embodiment, as the load condition, for example, the intake manifold pressure Pb is set to 300 to 500 mmH.
g, when the engine speed Ne is 2000-4000 rpm, the EGR ON / OFF intake manifold pressure difference is 5
By detecting the failure of the EGR system while limiting the failure to the optimum range of 0 to 60 mmHg, the failure detection accuracy can be improved as compared with the conventional example. Note that here
The appropriate range corresponds to a predetermined area.

FIG. 6 is for explaining another embodiment of the present invention. In this embodiment, when the EGR system malfunction is determined in a region where the EGR flow rate is large, an ON region of the EGR is determined as shown in FIG.
It is determined whether or not the flow rate is equal to or less than a predetermined value, that is, within the upper and lower determination values α and β, and ON / OFF of the EGR is performed only when the EGR flow rate is within the determination values as in the above-described embodiment.
The failure determination can be performed by detecting the intake manifold pressure (steps 400 to 402).

Although the above embodiment has been described with reference to the case where the load is detected by the intake manifold pressure and the engine speed, the present invention is not limited to this. The same effect can be obtained.

[0021]

As described above, according to the failure diagnosis apparatus of the present invention, when an abnormality of the EGR system is detected by turning on / off the EGR, the EGR failure determination region is limited according to the load, so that the EGR is performed. Within the ON region of the EGR and O of the EGR
Since a failure can be detected in a region where the detection value such as the N / OFF intake manifold pressure difference is large, the failure detection accuracy can be improved. Further, according to another aspect of the present invention, a failure is detected only when the EGR flow rate is equal to or less than a predetermined value, so that torque fluctuation at the time of ON / OFF of the EGR is reduced, and deterioration of drivability can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment when a failure diagnosis device of the present invention is applied to an exhaust gas recirculation control device.

FIG. 2 is a block diagram showing details of an electronic control unit of FIG. 1;

FIG. 3 is an explanatory diagram showing a relationship between an EGR rate and a load controlled by a BPT valve of an EGR control system for explaining the present invention.

FIG. 4 is an explanatory diagram showing a relationship between an EGR ON / OFF intake manifold pressure difference and a load for explaining the present invention.

FIG. 5 is a flowchart illustrating an example of an EGR failure determination process according to the embodiment.

FIG. 6 is a flowchart for explaining another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 engine 3 intake pipe 4 intake manifold 6 pressure sensor 7 throttle valve 11 exhaust pipe 14 return pipe 15 EGR valve 16 BPT valve 17 EGR solenoid 18 control passage 21 control unit 24 warning lamp

Claims (2)

(57) [Claims] A recirculation pipe for recirculating exhaust gas from an internal combustion engine to an intake pipe, a recirculation valve for controlling a flow rate of exhaust gas flowing through the recirculation pipe, and a recirculation valve passage area control for controlling a passage area of the recirculation valve. Means, an operating state detecting means for detecting an operating state of the internal combustion engine, and a first state detected by the operating state detecting means when the passage area of the recirculation valve is in the first state by the recirculation valve passage area control means. Means for storing the detected value of
Means for storing a second detection value detected by the operating state detecting means when the passage area of the recirculation valve is small or zero by the recirculation valve passage area control means; comprising a determination means for performing failure determination based on the detected value and the second detection value, the determination means set in advance
Of the first detection value and the second detection value
A failure diagnosis device for an exhaust gas recirculation control device, wherein a failure determination is performed within a predetermined region in which the deviation is predicted to be a predetermined value or more . 2. A failure diagnosis device for an exhaust gas recirculation control device according to claim 1, wherein the determination means performs the failure determination in a region where the flow rate of the exhaust gas flowing through the recirculation pipe is equal to or less than a predetermined value. .