JP5343880B2 - Diagnostic device for exhaust gas recirculation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve diagnostic accuracy, by ensuring a proper detection range relating to determination of failure in operation of a recirculation valve, according to a diagnostic device of an exhaust gas recirculation device. <P>SOLUTION: A calculation means 3 is provided to calculate a physical quantity correlating with a flow rate of recirculation gas returned to an intake side through the recirculation valve 9. A change means 5 is provided to perform a change control for changing opening of the recirculation valve 9 to be a plurality of openings. A determination means 4 is provided to determine a state of the recirculation valve 9 based on a difference in recirculation physical quantity calculated by the calculation means 3, in each of the plurality of openings changed by the change control of the change means 5. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a diagnostic apparatus for an exhaust gas recirculation device that recirculates part of exhaust gas to an intake pipe of an internal combustion engine via a recirculation valve.

  2. Description of the Related Art Conventionally, a technique for recirculating exhaust gas (also simply referred to as exhaust) from an exhaust passage side to an intake passage side has been known for the purpose of improving fuel efficiency of an internal combustion engine (engine) and improving exhaust purification performance. That is, the exhaust passage and the intake passage are connected by a recirculation passage, and a part of the exhaust gas is again introduced into the combustion chamber. A recirculation valve is provided on the recirculation path for adjusting the timing and flow rate of the recirculation gas introduced into the intake passage, and its opening degree is controlled in accordance with the operating condition of the internal combustion engine.

  By the way, in the exhaust gas recirculation apparatus that performs the control as described above, a technique for detecting malfunction of the reflux valve and clogging of the reflux path is also known. For example, there is one that determines the malfunction of the recirculation valve by detecting the intake pressure that fluctuates due to the recirculation gas flowing into the intake passage. In this case, if the closed recirculation valve is opened when the vehicle decelerates, and the differential pressure between the intake pressure at the time of closing and the intake pressure at the time of opening is less than the set value, a malfunction has occurred. Judgment is made (see Patent Document 1). By such control, it is said that the operating state of the exhaust gas recirculation device can be reliably diagnosed.

Japanese Patent Laid-Open No. 2-009937

  By the way, the recirculation gas introduced into the intake passage through the recirculation passage is particulates (particulate matter mainly composed of carbon), unburned fuel, other oil (oil), etc. generated by combustion in the combustion chamber. Containing. Therefore, they may adhere as deposits (deposits) to the valve body of the reflux valve interposed on the reflux path, gradually clogging the path, and the low opening degree side of the reflux valve may be blocked. On the other hand, since the deposit adheres sequentially from the low opening area side of the reflux valve, the reflux gas can be circulated without blocking the flow path in the high opening area.

  However, in the conventional discrimination control as described above, it is determined that a malfunction has occurred even when only the low opening range side of the reflux valve is closed, and the high opening range and the low opening range are determined. It is not possible to discriminate in consideration of the difference in the operating state of each reflux valve in the frequency range. That is, it is only possible to detect clogging of the recirculation valve at a predetermined opening degree, and as a result, there is a problem that the detection sensitivity for malfunction is inevitably set.

  Further, the intake pressure fluctuation caused by the introduction of the recirculation gas into the intake passage increases as the opening degree of the recirculation valve increases. For example, assuming that the amount of change in opening is the same, the amount of increase in reflux gas is larger when the opening is further increased from a slightly opened state than when the closed reflux valve is slightly opened. That is, not only the intake pressure but also the increasing gradient of the intake pressure changes according to the opening degree of the recirculation valve, and the value is not constant. Therefore, there is a case where it is not possible to accurately determine the operating state by comparing the intake pressure at the closing time and the intake pressure at the opening time as described in Patent Document 1 above.

Moreover, in the technique of the above-mentioned patent document 1, the determination according to the difference between the intake pressures when the recirculation valve is closed and opened is performed, and the negative pressure acting as the suction force into the combustion chamber of the internal combustion engine is determined. Since the influence is not taken into consideration, it cannot be said that the reliability is high in terms of discrimination accuracy.
One of the purposes of the present case has been devised in view of these problems, and is to improve the diagnostic accuracy by optimizing the sensitivity related to the determination of the malfunction of the reflux valve.

  The present invention is not limited to this purpose, and is a function and effect derived from each configuration shown in the embodiments for carrying out the invention described later, and other effects of the present invention are to obtain a function and effect that cannot be obtained by conventional techniques. Can be positioned.

A diagnostic device for an exhaust gas recirculation device disclosed herein is a device for diagnosing the state of an exhaust gas recirculation device in which a recirculation valve is provided in a recirculation path for returning a part of exhaust gas of an internal combustion engine to an intake side, A calculation means for calculating a physical quantity correlated with a flow rate of the reflux gas flowing through the valve through the valve as a reflux physical quantity, and a predetermined change condition based on the reflux physical quantity calculated by the calculation means is satisfied a plurality of times to, obtain Preparations changing means for performing the change control for changing the opening of the reflux valve into a plurality of opening, and a determination means having a first determination means and second determination means.
The first determination means determines the state of the reflux valve based on the difference in the return physical quantity calculated by the calculation means between the fully closed state of the reflux valve and the opened state at the first opening. To do. The second determining means is calculated by the calculating means in each of a state opened at the first opening and a state opened at the second opening larger than the first opening. The state of the reflux valve is determined based on the difference in the reflux physical quantity.
The determination means switches from the determination by the first determination means to the determination by the second determination means when the predetermined change condition is satisfied a plurality of times. The second determination means determines that the return valve is abnormal when the predetermined change condition is first established after switching to the determination by the second determination means.

In the disclosed exhaust gas recirculation apparatus diagnosis apparatus, the predetermined change condition is that the amount of change in the reflux physical quantity is less than a predetermined value.
Further, in the disclosed exhaust gas recirculation device diagnosis apparatus, the changing means opens the recirculation valve at a first opening degree that is larger than the fully closed state and a larger opening degree than the first opening degree. And the calculation means is opened at the first reflux physical quantity of the reflux gas passing through the reflux valve opened at the first opening and the second opening. The second reflux physical quantity of the reflux gas passing through the reflux valve is calculated.

In addition, the disclosed exhaust gas recirculation apparatus diagnosis apparatus further includes a rotation speed detection means for detecting the rotation speed of the internal combustion engine, and the changing means is based on the rotation speed detected by the rotation speed detection means. The opening degree of the reflux valve is changed.
In the exhaust gas recirculation device diagnosis apparatus according to the present invention, the change unit includes a learning unit that corrects a change amount of the opening degree of the recirculation valve in the change control according to the recirculation physical amount. Yes.

Further, the disclosed exhaust gas recirculation apparatus diagnostic device is characterized in that the calculation means calculates the amount of change in the intake pressure of the intake manifold of the internal combustion engine as an amount reflecting the difference in the recirculation physical quantity.
In the disclosed exhaust gas recirculation apparatus diagnostic device, the calculation means calculates the amount of change in the intake air temperature of the intake manifold of the internal combustion engine as an amount that reflects the difference in the recirculation physical quantity.

Further, in the disclosed exhaust gas recirculation apparatus diagnostic device, the calculation means calculates the amount of change in the recirculation gas temperature in the recirculation path downstream from the recirculation valve as an amount that reflects the difference in the recirculation physical amount. It is characterized by.
Further, the disclosed exhaust gas recirculation apparatus diagnosis apparatus is characterized in that the determination means determines that the recirculation valve is clogged when the amount of change in the recirculation physical quantity is less than a predetermined value.

According to the disclosed exhaust gas recirculation device diagnosis device, the sensitivity related to the determination of the malfunction of the recirculation valve can be optimized by referring to the amount of change in the recirculation physical amount before and after the opening degree change. Accuracy can be improved.
In addition, the possibility of misjudgment due to a local clogging phenomenon on the low opening range side can be reduced, and an operation failure such as clogging progressing to the high opening range side can be accurately diagnosed. .

It is a schematic diagram which shows the structure of the diagnostic apparatus of the exhaust gas recirculation apparatus which concerns on one Embodiment. It is a graph which shows the relationship between the opening degree of a recirculation | reflux valve controlled by the diagnostic apparatus of FIG. It is an opening degree map which concerns on the control implemented with the diagnostic apparatus of FIG. It is a flowchart for demonstrating the control content of the diagnostic apparatus of FIG. It is a time chart for demonstrating the control content of the diagnostic apparatus of FIG. 1, (a) is change of the implementation conditions of the control which concerns on determination, change of failure, (b) is change of the value of a counter, (c) is The opening of the recirculation valve and the change in the opening map, (d) shows the fluctuation of the change amount ΔP of the intake manifold pressure, and (e) shows the state of the notification lamp indicating the determination result. Is a distribution diagram showing the relationship between the engine speed N _e and the intake manifold pressure P when no clogged recirculation valve. It is a distribution diagram showing the relationship between the engine speed N _e and the intake manifold pressure P when the jam occurs in a low opening range of the reflux valve. It is a flowchart for demonstrating the control content of the diagnostic apparatus of the exhaust gas recirculation apparatus as a modification.

Hereinafter, an embodiment of a diagnostic device for an exhaust gas recirculation device will be described with reference to the drawings. However, the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not clearly shown in the embodiment described below. That is, the present embodiment may be variously modified and implemented without departing from the spirit of the invention.
[1. overall structure]
The diagnostic device according to one embodiment is applied to the exhaust gas recirculation device for a vehicle shown in FIG.

  An intake passage 13 and an exhaust passage 14 are connected to the engine 11 (internal combustion engine) shown in FIG. The intake passage 13 is connected to the intake port of the engine 11 via an intake manifold 15 (intake collecting pipe), and the exhaust passage 14 is connected to the exhaust port of the engine 11 through an exhaust manifold 16 (exhaust collecting pipe). The intake air introduced from the intake passage 13 flows into the combustion chamber 12 of the engine 11 from the intake port through the intake manifold 15, and is discharged from the exhaust port to the exhaust passage 14 through the exhaust manifold 16.

  The intake passage 13 and the exhaust passage 14 are connected by a recirculation path 8, and a recirculation valve 9 is provided in the middle. The recirculation path 8 is a so-called EGR (Exhaust Gas Recirculation) passage, and recirculates a part of the exhaust gas on the exhaust passage 14 side to the intake passage 13 side. One end of the reflux path 8 is connected to the downstream side (combustion chamber 12 side) of the throttle valve 17. In the example of FIG. 1, the intake manifold 15 is connected. The position of the other end of the reflux path 8 is arbitrary. Hereinafter, the exhaust gas introduced into the intake passage 13 through the recirculation path 8 is referred to as recirculation gas.

  The recirculation valve 9 is a control valve that adjusts the flow rate of the recirculation gas and the timing at which the recirculation gas is introduced into the intake passage 13, and controls the opening degree and the timing of changing the opening degree by an ECU 10 (electronic control unit) described later. Has been. For example, when the opening of the recirculation valve 9 is opened in a state where a negative pressure is generated along with the movement of the piston in the combustion chamber 12, the recirculation gas moves to the intake passage 13 side and is taken in from the outside. The air is sucked into the combustion chamber 12 together with the intake air.

  The flow characteristics of the recirculation valve 9 are shown by a solid line in FIG. Here, the larger the opening degree of the recirculation valve 9, the more the recirculation gas flow rate increases and the recirculation gas increase amount (the slope of the graph) increases. Further, the flow rate of the reflux gas increases as the opening degree of the throttle valve 17 decreases and as the negative pressure of the combustion chamber 12 of the engine 11 increases (intake increases). The broken line in FIG. 2 is a flow rate characteristic when deposits adhere to the low opening area side of the valve body of the reflux valve 9, and the flow rate is reduced in the entire opening area compared to the solid line graph. Show.

The intake manifold 15 is provided with a pressure sensor (detection means) 1. The pressure sensor 1 detects intake manifold pressure P (intake air pressure) in the intake passage 13 downstream of the throttle valve 17. The pressure sensor 1 only needs to be downstream of the throttle valve 17 and may be disposed in the intake passage 13 other than the intake manifold 15. The intake manifold pressure P detected by the pressure sensor 1 is input to the ECU 10. Further, the engine 11 speed sensor 7 (rotational speed detecting means) is provided for detecting the engine speed N _e. The engine speed N _e detected here is also input to the ECU 10.

The ECU 10 is an electronic control unit that performs control to determine whether the recirculation valve 9 is malfunctioning or clogged with deposits, and is provided as an LSI device in which a known microprocessor (CPU, MPU), ROM, RAM, etc. are integrated. Has been. ECU10 In addition to the engine speed N _e detected by the intake manifold pressure P and the rotational speed sensor 7 detected by the pressure sensor 1, on the basis of various signals inputted from an engine ECU (not shown) or the like, the opening of the recirculation valve 9 And the control for determining the operating state of the reflux valve 9 is performed.

  In addition, as said various signals, the operation state of an idle switch (throttle position sensor), the filling efficiency of the combustion chamber 12, etc. are mentioned.

[2. Control type]
The ECU 10 performs the following four types of control.
[A] Opening control for opening the closed recirculation valve 9 under a certain condition [B] First determination control for determining the operating state of the recirculation valve 9 based on the intake manifold pressure fluctuation before and after the opening control is performed [C] ] Change control for changing the opening degree of the recirculation valve 9 opened by the open control under a certain condition. [D] A process for determining the operating state of the recirculation valve 9 from the fluctuation of the intake manifold pressure before and after the execution of the change control. Two-determination control The opening control is a control for introducing the reflux gas into the intake passage 13 when the vehicle is decelerated. The opening control is repeatedly performed periodically when the start condition is satisfied. In the present embodiment, it is assumed that the throttle valve 17 is in a fully closed state and the vehicle is decelerating, the engine speed _Ne is within a predetermined range, and the like as start conditions. Hereinafter, the start condition of the opening control is also referred to as an EGR monitor execution condition.

  The first determination control is control performed immediately after each opening control. In this control, based on the intake manifold pressure P detected before and after the opening control is performed, it is determined whether there is a possibility that the recirculation valve 9 is malfunctioning or clogged. The result of the determination here is stored in the memory as a temporary determination result that means the presence or absence of a slight malfunction or the possibility of clogging.

  The change control is control that is performed when a start condition is established based on a determination result in the first determination control. This change control functions to change the amount of the recirculated gas introduced into the intake passage 13 by changing the opening of the recirculation valve 9 that is opened during the open control. For example, when the opening degree map of the recirculation valve 9 is changed in the change control, the opening control for the next time (or after the next time) is performed according to the changed opening degree map.

In the present embodiment, the number of times that a slight malfunction or possibility of clogging is detected in the first determination control is defined in the change control start condition (change condition). Then, change control is performed.
The second determination control is control that is performed immediately after the opening control after the change control is performed. In this control, based on the intake manifold pressure P detected before and after the change of the opening degree of the recirculation valve 9, it is determined whether the recirculation valve 9 is not malfunctioning or clogged. The determination result here is stored in the memory as vehicle diagnosis data, and is also notified to the occupant via the notification lamp 20 and the display device.

[3. Configuration of ECU]
As a software configuration for performing each control described above, the ECU 10 includes an opening unit 2, a calculation unit 3 (calculation unit), a determination unit 4 (determination unit), and a change unit 5 (change unit). Each software shown here is recorded in a memory or a storage device (not shown), and implements the functions described below by being read by a microprocessor as needed. In addition, it is good also as a structure which implement | achieves these functions with a hardware (for example, electronic circuit).

The opening part 2 performs opening control. The opening part 2 outputs a signal for controlling the opening degree of the reflux valve 9 from the fully closed state to a predetermined open state to the reflux valve 9 when the EGR monitor execution condition is satisfied. The predetermined open state here is roughly divided into two types of states, an open state based on the first map (first opening) and an open state based on the second map (second opening).
First map, as shown by the solid line in FIG. 3 is a control map for normal control relationship is defined between the opening and the engine speed N _e of the recirculation valve 9. This control map is appropriately set according to the characteristics of the engine 11, the shapes of the intake passage 13 and the exhaust passage 14, the shape and connection position of the return passage 8, the characteristics of the return valve 9, and the like. Note that the opening degree of the recirculation valve 9 set in the first map is larger than that in the fully closed state.

On the other hand, the second map, as shown by the dashed line in FIG. 3, a set control map so that the opening is opened larger than the first map in the same engine speed N _e. The opening unit 2 performs the opening control of the reflux valve 9 based on the first map unless a change control signal is input from the changing unit 5 described later. Further, when a change control signal is input, opening control of the reflux valve 9 based on the second map is performed.

  The calculation unit 3 (calculation means) performs a predetermined calculation on the values detected by the pressure sensor 1 and the rotation speed sensor 7 as necessary, calculates a physical quantity that reflects the flow rate of the reflux gas, and stores it in the memory. Is. The calculation unit 3 includes an intake manifold pressure calculation unit 3a (reflux physical quantity calculation means), a reference intake manifold pressure calculation unit 3b (reference reflux physical quantity calculation means), and a change amount calculation unit 3c.

The intake manifold pressure calculation unit 3a stores the intake manifold pressure P detected by the pressure sensor 1 in a memory as a variable corresponding to the state in which the intake manifold pressure P is detected. Here, the intake manifold pressures P when the reflux valve 9 is closed and opened are stored. Hereinafter, the intake manifold pressure P when the throttle valve 17 and the return valve 9 are closed is referred to as a first intake manifold pressure P _1, and the intake manifold pressure P when the throttle valve 17 is closed and the return valve 9 is opened is referred to as a second intake manifold pressure P ₁ . referred to as the intake manifold pressure P _2.

The reference intake manifold pressure calculation unit 3b calculates a correction amount corresponding to the influence of the operation state of the engine 11 on the magnitude of the intake manifold pressure P and stores it in the memory. Here, the correction amount of each impact fraction at the time and the opening closing of the recirculation valve 9 is calculated according to the engine speed N _e, it is stored. The calculation of these correction amounts, the corresponding map of the stored engine speed N _e is used in advance to the ECU 10. Incidentally, the correction amount has a decreasing (to lower the intake manifold pressure P) characteristic as the engine speed N _e is increased.

Hereinafter, the engine speed N _e when the first intake manifold pressure P ₁ is detected is referred to as the first engine speed N _e1, and the engine speed N _e when the second intake manifold pressure P ₂ is detected is the second engine speed N _e . This is called engine speed N _e2 . The correction amount at the time of detecting the first intake manifold pressure P ₁ is referred to as a reference first intake manifold pressure P (N _e1 ), and the correction amount at the time of detecting the second intake manifold pressure P ₂ is referred to as a reference second intake manifold pressure P _2. Called P (N _e2 ).

The change amount calculation unit 3c calculates the change amount ΔP according to the following expression 1 based on the calculation results of the intake manifold pressure calculation unit 3a and the reference intake manifold pressure calculation unit 3b. This change amount ΔP is a physical quantity (reflux physical quantity) correlated with the flow rate of the reflux gas.

[P (N _e2 ) −P (N _e1 )] in the equation 1 is the intake manifold pressure P that naturally changes due to the fluctuation of the engine speed N _e regardless of the opening degree of the recirculation valve 9. That is, here, [P (N _e2 ) −P (N _e1 )] is subtracted to correct the influence of fluctuations in the engine speed N _e .

The determination unit 4 (determination means) determines the operating state of the recirculation valve 9 based on the change amount ΔP calculated by the calculation unit 3. The determination unit 4 includes a first determination unit 4a (first determination unit) and a second determination unit 4b (second determination unit).
The 1st determination part 4a (1st determination means) implements 1st determination control following open control, and determines the operating state of the reflux valve 9 at the time of non-execution of change control. That is, when the opening degree of the recirculation valve 9 is controlled based on the first map, the change amount ΔP calculated by the calculation unit 3 is compared with the predetermined threshold value P ₀ . Here, if ΔP <P _0, it is determined that the recirculation valve 9 may be defective or clogged, and N _m +1 is substituted into the counter N _m and stored in the memory. On the other hand, if ΔP ≧ P ₀ , it is determined that there is no possibility of malfunction or clogging of the recirculation valve 9, and the counter N _m is reset to 0 and stored in the memory.

The counter N _m is the number of times that ΔP <P ₀ is determined in the first determination control, and the change control start condition is that the value of the counter N _m is equal to or greater than a predetermined number (for example, twice or more). It is.
The second determination unit 4b (second determination unit) performs the second determination control subsequent to the change control in the change unit 5 described later, in other words, determines the operating state of the reflux valve 9 when the change control is performed. Is. Here, when the opening degree of the recirculation valve 9 is controlled based on the second map, the change amount ΔP calculated by the calculation unit 3 is compared with the predetermined threshold value P ₀ . If ΔP <P _0, it is determined that the recirculation valve 9 is malfunctioning or clogged, and this is stored in the memory as vehicle diagnostic data. Further, the notification lamp 20 is turned on to notify the occupant of the malfunction of the reflux valve 9.

As described above, the determination unit 4 determines the state of the recirculation valve 9 based on the difference between the change amounts ΔP calculated for each of the plurality of opening states larger than the fully closed state.
Changing section 5 (changing means), the value of the counter N _m which is added by the first determination unit 4a is greater than a predetermined number of times (e.g., more than twice) when a is for implementing the change control. The changing unit 5 outputs a signal to the opening unit 2 during the change control, and causes the opening unit 2 to select the second map. On the other hand, during non-change control, the output of the signal is stopped, and the opening unit 2 is made to select the first map. That is, the changing unit 5 functions to change the opening degree of the reflux valve 9 to a plurality of open states other than the fully closed state.

[4. flowchart]
FIG. 4 is a flowchart for explaining an example of control in the ECU 10. The initial value of the counter N _m described in this flow is N _m = 0. The first intake manifold pressure P ₁ , the second intake manifold pressure P ₂ , the reference first intake manifold pressure P (N _e1 ), the reference second intake manifold pressure P (N _e2 ), and the variation ΔP are measured at the start and end of the flow. Shall be reset to

In step A1, it is determined in the opening part 2 whether or not an EGR monitor execution condition that is a start condition of the opening control is satisfied. Here, for example, the following EGR monitor execution conditions are determined.
[A-1] the idle switch is on (throttle valve 17 is fully closed) a [A-2] the engine speed N _e is within the predetermined range [A-3] charging efficiency E _c is less than a predetermined efficiency ( When the vehicle is decelerating) When the EGR monitor execution condition is satisfied in this step, the control proceeds to step A2. On the other hand, if the EGR monitor execution condition is not satisfied, this flow is once ended, and control is started again from step A1 with a predetermined time interval.

In step A2, intake manifold pressure P detected by the pressure sensor 1 is inputted to the intake manifold pressure calculation portion 3a of the calculating unit 3, are stored as a first intake manifold pressure P _1. In step A3, the engine speed N _e detected by the speed sensor 7 is input to the reference intake manifold pressure calculating unit 3b, the reference first intake manifold pressure P (N _e1) is calculated.
In the subsequent step A4, it is determined whether or not the value of the counter N _m is N _m <2, as a change control start condition. Since the initial value of the counter N _m is N _m = 0, this condition is initially satisfied (that is, the change control start condition is not satisfied), and the process proceeds to Step A5. At this time, a change control signal is not output from the changing unit 5.

In step A5, opening control based on the first map is performed in the opening unit 2. Thus, the opening of the recirculation valve 9 is opened from the fully closed state to the first opening state according to the engine speed N _e, the recirculating gas flows through the return channel 8 to the intake passage 13 side inlet To do. At this time, since the throttle valve 17 is in a fully closed state, the intake manifold pressure P increases according to the inflow amount of the reflux gas.

In step A7, the intake manifold pressure P detected by the pressure sensor 1 is inputted to the intake manifold pressure calculation portion 3a of the calculating unit 3 again, and stored as a second intake manifold pressure P _2. Moreover, In step A8, the engine speed N _e detected by the speed sensor 7 is input to the reference intake manifold pressure calculating unit 3b, the reference second intake manifold pressure P (N _e2) is calculated.
In the subsequent step A9, the change amount calculation unit 3c calculates the change amount ΔP according to Equation 1. Here, after considering the effect of changes in the engine speed N _e, the inflow of recirculated gas by opening control step A5 differential pressure ΔP of the intake manifold pressure P which is reflected is grasped.

In step A10, the first determination unit 4a of the determination unit 4, the change amount ΔP is equal to or less than a predetermined threshold value P ₀ is determined. Here, if ΔP ≧ P ₀ , the process proceeds to step A14, and the counter N _m is reset to zero. In the subsequent step A15, the first determination unit 4a determines that there is no possibility of malfunction or clogging of the recirculation valve 9, and the flow is finished as it is. That is, by subtracting the effects of changes in the engine speed N _e, the amount of increase in the intake manifold pressure P by opening control if enough, the operating state of the recirculation valve 9 is determined to be good. In this case, the control is started again from step A1 at a predetermined time interval (the execution cycle time of this flow), and the diagnosis is repeatedly performed. On the other hand, if ΔP <P ₀ in step A10, the process proceeds to step A11.

In step A11, the first determination unit 4a determines that the recirculation valve 9 may be defective or clogged, and N _m +1 is substituted into the counter N _m . In the subsequent step A12, it is determined whether or not the value of the counter N _m is N _m ≧ 3. Since the initial value of the counter N _m is N _m = 0, even if 1 is added to the counter N _m in step A11, this condition is not satisfied at first, and this flow is ended as it is. Therefore, control is started again from step A1 at predetermined time intervals, and diagnosis is repeatedly performed.

When the value of the counter N _m becomes N _m = 2 by repeating such control, the condition of step A4 is not satisfied, and the control proceeds to step A6. At this time, a change control signal is output from the changing unit 5 to the opening unit 2.
In step A6, opening control based on the second map is performed in the opening unit 2. That is, the change control and the release control are performed in an overlapping manner. Thus, the opening of the recirculation valve 9 is opened from the fully closed state to the second opening degree state according to the engine speed N _e, the opening degree is larger controlled than opening control in the preceding control cycle The Therefore, even if deposits are attached to the low opening area of the valve body of the recirculation valve 9 (light clogging has occurred), the recirculation gas passes through the recirculation path 8 to the intake passage 13 side. Strong inflow.

In subsequent steps A7 to A9, as described above, the change amount ΔP is calculated. However, since the opening control and the change control are performed overlappingly after passing through step A6, as long as there is a change in the flow rate of the reflux gas, a change amount ΔP having a value different from that when only the opening control is performed. Is calculated.
In step A10, the second determination unit 4b of the judging unit 4, the change amount ΔP is equal to or less than a predetermined threshold value P ₀ is determined. Here, if ΔP ≧ P ₀ , the process proceeds to step A14 and is reset to 0 even if the counter N _m is 2. In this case, it is considered that the deposit is attached only to the low opening degree region of the valve body of the reflux valve 9.

If ΔP <P ₀ in step A10, the process proceeds to step A11 where N _m +1 is substituted into the counter N _m . Further, in step A12, it is determined whether or not the value of the counter N _m is N _m ≧ 3. If N ≧ 3, the process proceeds to step A13. In step A13, it is determined in the second determination unit 4b that the recirculation valve 9 is malfunctioning or clogged, and the diagnosis result is stored in the memory as vehicle diagnosis data. In addition, the notification lamp 20 is controlled to be turned on by the ECU 10, and a malfunction of the reflux valve 9 is notified to the occupant.

[5. Time chart]
With reference to the time charts shown in FIGS. 5A to 5E, the diagnosis status of the above-described exhaust gas recirculation apparatus diagnosis apparatus will be described.
For example, when the EGR monitor execution condition is satisfied at time t _{0 as} shown in FIG. 5A while the vehicle is decelerating, the calculation unit 3 of the ECU 10 causes the first intake manifold pressure P ₁ and the reference first intake manifold pressure P (N _e1 ) is grasped. Since the value of the counter N _{m at} this time is N _m = 1 as shown in FIG. 5B, the change control is not started. Thereby, as shown in FIG.5 (c), the open control of the recirculation | reflux valve 9 based on a 1st map is implemented.

When the recirculation valve 9 is opened at time t ₁ , the calculation unit 3 of the ECU 10 grasps the second intake manifold pressure P ₂ and the reference second intake manifold pressure P (N _e2 ), and calculates the change amount ΔP. Here, as shown in FIG. 5D, if the change amount ΔP is equal to or greater than a predetermined threshold value P ₀ , the value of the counter N _m is reset to N _m = 0 at time t ₂ , and the opening control is performed. finish. At this time, the reflux valve 9 is closed as shown in FIG. The time T (time between time t ₁ and time t ₂ ) for opening the recirculation valve 9 is appropriately set according to the characteristics of the engine 11, required drivability, and the like.

Thereafter, the opening control as described above is repeated, and if the change amount ΔP is less than the predetermined threshold value P ₀ , the counter N _m is added at each of time t ₃ and time t ₄ . When the EGR monitor execution condition is satisfied at time t ₅ in the state where the value of the counter N _m is N _m = 2, the change control is started, and as shown in FIG. 5C, the recirculation valve based on the second map 9 open control is performed. Thereby, the opening degree of the reflux valve 9 is opened larger than the previous opening control. Here, as shown in FIG. 5D, if the change amount ΔP is equal to or greater than the predetermined threshold value P ₀ , the value of the counter N _m is reset to N _m = 0 again at time t ₆ , and the opening control is performed. Ends. At this time, the state of the valve body of the reflux valve 9 is determined to be a state in which deposits are attached only in the low opening range.

On the other hand, when the change control is started at time t ₇ in a state where the value of the counter N _m is N _m = 2 and the opening control of the recirculation valve 9 based on the second map is performed, the change amount ΔP is a predetermined amount. If it is less than the threshold value P ₀ , as shown in FIG. 5 (b), the value of the counter N _m becomes 3 at time t ₈ , and it is determined that the return valve 9 is malfunctioning or clogged. The And as shown in FIG.5 (e), the notification lamp 20 is lighting-controlled and a passenger | crew is alert | reported to the malfunctioning of the recirculation | reflux valve 9. FIG.

[6. effect]
According to the diagnostic device described above, a local clogging phenomenon in which the flow of the reflux gas is inhibited only when the opening degree of the reflux valve 9 is relatively small is erroneously determined as the malfunction of the reflux valve 9. The operating state of the reflux valve 9 can be accurately diagnosed. On the other hand, when clogging has progressed not only to the low opening area side but also to the high opening area side of the recirculation valve 9, this can be accurately diagnosed as malfunction of the recirculation valve 9.

  Further, in the above-described diagnostic device, the recirculation valve 9 having the opening characteristic as shown in FIG. 2 is subjected to opening control for diagnosing the flow rate difference of the recirculating gas between the closed state and the predetermined open state. In addition to the implementation, the recirculation gas between a plurality of states (for example, two types of opening states defined in the first map and opening states defined in the second map) as a predetermined open state The change control which makes the flow rate difference of this the object of diagnosis is also implemented.

  Therefore, it is possible to grasp the change gradient of the flow rate of the recirculation gas with respect to the change in the opening degree of the recirculation valve 9, and the sensitivity related to the determination of the state of the recirculation valve 9 can be optimized. For example, as shown in FIG. 2, it is suitable for use in the recirculation valve 9 having a flow rate characteristic such that the increase amount of the recirculation gas flow is larger than the increase amount of the recirculation amount. Characteristics can be diagnosed.

Moreover, in the above-mentioned diagnostic apparatus, the operating state of the reflux valve 9 is determined doubly by the opening control before and after the change control. That is, it is determined that the malfunction or clogging of the recirculation valve 9 occurs only when the determination conditions in both the first determination unit 4a and the second determination unit 4b are satisfied, so the determination accuracy is greatly improved. Can be made.
Moreover, since the above-mentioned diagnostic apparatus is provided with the 1st determination part 4a which determines the start condition of change control, the timing which changes an opening degree can be adjusted freely by setting the start condition beforehand. can do. Further, since the number of times that the malfunction or the possibility of clogging is detected in the recirculation valve 9 is referred to as the change control start condition, the reliability of the diagnosis result can be further improved. The diagnosis can be made more solid as the predetermined number of times (for example, two times) related to the determination by the first determination unit 4a is increased, or the diagnosis can be made more quickly as the predetermined number is decreased. . In addition, since the change control is performed only when the first determination unit 4a detects a slight malfunction or a possibility of clogging in the recirculation valve 9, the determination accuracy can be further improved. The possibility of misjudgment can be reduced.

Further, since the change control is not performed unless not change amount ΔP of the open control is small, excessively without such recirculation valve 9 is opened, adverse effects on drivability, such as reduction of the engine speed N _e Can be suppressed. In addition, since the ECU 10 can perform the change control in addition to the opening control, the ECU 10 is highly applicable to existing vehicles that perform only the opening control, and substantially improve the function only by upgrading the software. There is an advantage that it can be achieved.

Moreover, since the opening degree changed by change control is prescribed | regulated by two types of opening degree maps, a control structure can be simplified, ensuring the accuracy of determination.
Further, in the above-described embodiment, as shown in Equation 1, since the change amount ΔP is calculated after correcting the intake manifold pressure P that varies depending on the engine speed N _e , the operating state of the recirculation valve 9 is determined more accurately. can do.

Further, the opening degree of the recirculation valve 9 controlled by the opening control and change control, rather than being set as a preset fixed value, as shown in FIG. 3, the map corresponding to the engine speed N _e Therefore, the control according to the operating state of the engine 11 can be performed, the operation state can be determined more accurately, and drivability can be improved.
In addition, special engine control for the purpose of only the diagnosis of the recirculation valve 9 is unnecessary, and there is an advantage that versatility is high. Moreover, in the above-mentioned embodiment, control using the existing pressure sensor 1 is possible, and cost can be reduced. Note that the software recorded in the ECU 10 can be executed by, for example, an engine ECU, and the cost can be further reduced.

[6. Modifications etc.]
[6-1. Judgment conditions]
The distribution diagrams shown in FIGS. 6 and 7 are created based on the test results using the above-described embodiment, and are detected by the engine speed _Ne and the pressure sensor 1 detected by the speed sensor 6. The relationship with the intake manifold pressure P is shown. The white squares (□) in the distribution chart shown in FIG. 6 indicate the amount of change ΔP calculated when opening control is performed using the first map for a normal recirculation valve 9 without clogging, and the change amount ΔP at that time. It shows the relationship between the engine speed N _e.

In addition, a white circle (◯) in FIG. 7 shows the case where the opening control is performed using the first map for the recirculation valve 9 in which the valve body is slightly clogged (clogged in the low opening range). It shows the relationship of the calculated amount of change ΔP and the engine speed N _e at that time. On the other hand, filled diamonds (◆) is the same recirculation valve 9, shows the relationship between the calculated amount of change ΔP when performing opening control using the second map and the engine speed N _e at that time Yes.

  Here, the data group indicated by the white squares in FIG. In addition, a data group indicated by a white circle in FIG. 7 is referred to as a B group, and a data group indicated by a black diamond is referred to as a C group. Each data of the B group is a first reflux physical quantity that correlates with a flow rate of the reflux gas passing through the reflux valve 9 opened based on the first map, and each data of the C group is released based on the second map. It can be said that this is the second reflux physical quantity correlated with the flow rate of the reflux gas passing through the reflux valve 9.

The opening control in the above-described embodiment can be regarded as a control for making a diagnosis by determining whether or not the operating state of the reflux valve 9 is classified into the A group. That is, when a predetermined threshold value P ₀ is used as the determination criterion as the allowable lower limit value of the A group and data below this value is detected, the first determination unit 4a has malfunctioned or clogged in the reflux valve 9. There is a possibility.

  On the other hand, the change control in the above-described embodiment grasps the B group and the C group by controlling the opening degree of the reflux valve 9 using two types of opening maps, and the C group is different from the B group. Otherwise, it is considered that the recirculation valve 9 is malfunctioning or clogged. That is, when the B group that is not classified into the A group is detected, the data measurement conditions are changed, and when similar data is detected again with the B group as a reference, the second determination unit 4b performs the reflux valve 9. It is determined that there is a malfunction or clogging.

The predetermined threshold value P ₀ in this change control is used as a criterion for determining the degree of similarity between the C group and the B group. Therefore, various determination conditions in the second determination unit 4b are conceivable. For example, it is not necessary to use a condition overlapping with the determination condition in the first determination unit 4a as in the above-described embodiment.
A flowchart as a modification is shown in FIG.

Steps B1 to B15 except for step B6 in this flow are the same as steps A1 to A15 except for step A6 in the flow of FIG. That is, the control after step B6 related to the change control is different.
In step B6, opening control based on the second map is performed in the opening unit 2. Thereby, the opening degree of the reflux valve 9 is opened from the fully closed state to the second opening state, and is controlled to be larger than the previous opening control. In step B21 and B22, as in steps B7 and B8, with a second intake manifold pressure P ₂ is stored, the reference second intake manifold pressure P (N _e2) is calculated. On the other hand, in the subsequent step B23, the second change amount ΔP ′ is calculated according to Equation 1 separately from the change amount ΔP calculated in the previous opening control. That is, the second change amount ΔP ′ as the data of the C group is calculated while the change amount ΔP calculated in the previous opening control is held as the data of the B group.

In step B24, a value obtained by subtracting the amount of change [Delta] P from the second change amount [Delta] P 'is either less than a predetermined second threshold value P ₁ is determined. Here, if ΔP′−ΔP ≧ P ₁ , the process proceeds to step B26 and the counter N _m is reset to zero. In the subsequent step A27, the second determination unit 4b determines that there is no possibility of malfunction or clogging of the recirculation valve 9, and the flow is terminated as it is. That is, if the behavior in the opening control after the change control is different from the previous opening control, it is determined that the operating state of the reflux valve 9 is good.

On the other hand, if ΔP′−ΔP <P ₁ in step B24, the process proceeds to step B25, where it is determined in the second determination unit 4b that the return valve 9 is malfunctioning or clogged. It is stored in the memory as diagnostic data. That is, when the behavior change is not sufficient as compared with the previous opening control, it is determined that the operating state of the reflux valve 9 is not good.
Also in the above control, an accurate diagnosis can be performed as in the above-described embodiment, and the sensitivity relating to the determination of the state of the reflux valve 9 can be optimized.

In addition, as other determination conditions implemented by the 2nd determination part 4b, the following can be considered.
[D-1] The second change amount ΔP ′ is less than a predetermined third threshold value P _2. [D-2] The difference between the average value of the plurality of change amounts ΔP and the second change amount ΔP ′ is a predetermined value. It is less than the determination condition in the 2nd determination part 4b, The determination condition in the 1st determination part 4a can also be variously set not only in the above-mentioned embodiment. For example, the following can be considered.
Mean value of [B-1] a plurality of variation ΔP is less than a predetermined threshold value P ₀ [B-2] variation ΔP is within a predetermined range P _a to P _b

[6-2. Others]
In the above-described embodiment, in the change control, the opening degree of the reflux valve 9 is controlled in two stages using the first map and the second map, but the control mode is not limited to this. For example, by preparing in advance three or more opening map, by selecting one of those opening degree map in accordance with the value of the change amount ΔP and a counter N _m, controls the opening in multiple stages It is good also as composition to do. The change amount of the opening degree of the recirculation valve 9 in the change control may be a constant value or a fluctuation value that fluctuates (has a width) within a predetermined range. Such control makes it possible to diagnose the operating state and clogging of the recirculation valve 9 in a wide opening range.

In the above-described embodiment, the value of the change amount ΔP is calculated based on the differential pressure between the first intake manifold pressure P ₁ and the second intake manifold pressure P ₂ , but the specific calculation method is not limited to this. . Any method may be used as long as the difference between the first reflux physical quantity before the opening degree is changed by the change control and the second reflux physical quantity after the opening degree is changed, for example, the first intake manifold pressure P _1. The ratio between the second intake manifold pressure P ₂ and the index value representing the data distribution of the B group in FIG. 7 and the index value representing the data distribution of the C group in FIG. May be performed. That is, any calculation method may be used as long as it observes the difference between the B group and the C group or the change from the B group to the C group.

In the above-described embodiment, the conditions [A-1] to [A-3] are exemplified as the opening control execution conditions (EGR monitor execution conditions). However, instead of or in addition to these conditions, the air-fuel ratio Alternatively, conditions relating to the pressure in the exhaust passage 14 and the load on the engine 11 may be used.
In the embodiment described above, as the starting condition for changing control, reference is made to the value of the counter N _m, instead of this, or in addition, also the value of the change amount ΔP as a reference directly Good. For example, the following conditions can be considered.

[C-1] change amount ΔP is, the counter N is less than a predetermined threshold value P _3, which is set according to the value of _m [C-2] variation ΔP is, the threshold value of the first determination unit 4a is greater than the predetermined threshold value P ₄ than P ₀ in the above embodiment, the change amount ΔP is reset to the value of the counter N _m if the predetermined threshold value P ₀ or 0 it is, or may be configured to accumulate without resetting the value of the counter N _m.

Further, the value of the counter N _m in the above embodiment, although the possibility of minor malfunctions and jamming in the first determination unit 4a is intended to mean the number of times the detected frequency instead of such number It may be configured to refer to (number of times per unit time). Note that the greater the value of the counter N _m, the higher the frequency here, and the smaller the value of the counter N _m , the lower the frequency. Therefore, it can be said that the frequency here is a concept included in the number of times that the first determination unit 4a detects a slight malfunction or the possibility of clogging.

  Further, in the above-described embodiment, the flow rate change of the reflux gas flowing in via the reflux valve 9 is detected based on the intake manifold pressure P detected by the pressure sensor 1, but instead of the intake manifold pressure P, or In addition to this, it is also conceivable to use the reflux gas temperature in the reflux path 8 downstream from the reflux valve 9 or the intake air temperature T in the intake manifold 15. That is, as the flow rate of the recirculation gas decreases, the recirculation gas temperature or the intake air temperature T decreases, so that the operation state of the recirculation valve 9 can be grasped by the same calculation as the intake manifold pressure P. Further, when the intake air temperature T in the intake manifold 15 is used, control using an existing temperature sensor is possible, and the cost can be reduced.

  Moreover, the parameter used as the object of calculation and determination in ECU10 is not limited to this. For example, it may be configured to directly detect the flow rate of the reflux gas and determine this, or by detecting the concentration or partial pressure of a specific component contained in the reflux gas, the flow rate, temperature, pressure, etc. of the entire reflux gas can be determined. It is good also as a structure to estimate. Any physical quantity that reflects the flow rate of the reflux gas may be used.

In the above embodiment, the opening map for controlling the opening of the recirculation valve 9 is changed from the first map to the second map in the change control. It is good also as a structure which sets the valve opening degree in the opening control after the next according to variation | change_quantity (DELTA) P, and is good also as a structure which learns and corrects the valve opening degree.
In this case, it is conceivable to provide a learning unit (learning means) for newly creating or dynamically updating the second map based on the change amount ΔP calculated by the calculation unit 3 inside the ECU 10. Alternatively, the learning unit may learn by correcting the increment relative to the opening degree defined by the first map based on the change amount ΔP. For example, it is conceivable to add correction to the change amount ΔP so that the greater the degree of malfunction of the recirculation valve 9 (for example, the degree of clogging), the larger the increment. With such a configuration, it is possible to change the determination opening according to the degree of malfunction of the recirculation valve 9, and a more accurate determination of the operating state can be expected.

In the above-described embodiment, the determination result in the second determination unit 4b is notified to the occupant via the notification lamp 20, the display device, etc., but the notification method is arbitrary, and here The diagnosis result may be diverted to other control of the vehicle.
The disclosed diagnostic device can be applied not only to an exhaust gas recirculation device for a gasoline engine but also to an exhaust gas recirculation device for a diesel engine.

DESCRIPTION OF SYMBOLS 1 Pressure sensor 2 Opening part 3 Calculation part (calculation means)
3a In manifold pressure calculation part (reflux physical quantity calculation means)
3b Reference intake manifold pressure calculation unit (reference reflux physical quantity calculation means)
3c change amount calculation unit 4 determination unit (determination means)
4a 1st determination part (1st determination means)
4b 2nd determination part (2nd determination means)
5 Change part (change means)
7 Rotational speed sensor (Rotational speed detection means)
8 Reflux path 9 Reflux valve 10 ECU (electronic control unit)
11 Engine (Internal combustion engine)
12 Combustion chamber 13 Intake passage 14 Exhaust passage 15 Intake manifold 16 Exhaust manifold 17 Throttle valve 20 Notification lamp P In manifold pressure P ₀ Threshold value P ₁ First intake manifold pressure P ₂ Second intake manifold pressure P (N _e1 ) Reference first intake manifold Pressure P (N _e2 ) Reference second intake manifold pressure ΔP Amount of change N _e Engine speed N _e1 First engine speed N _e2 Second engine speed

Claims (9)

A device for diagnosing the state of an exhaust gas recirculation device in which a recirculation valve is provided in a recirculation path for returning a part of exhaust gas of an internal combustion engine to the intake side,
A calculation means for calculating a physical quantity correlated with the flow rate of the reflux gas flowing through the reflux path through the reflux valve as a reflux physical quantity;
Change means for performing change control for changing the opening degree of the reflux valve to a plurality of opening degrees when a predetermined change condition based on the reflux physical quantity calculated by the calculating means is satisfied a plurality of times ;
First determination means for determining the state of the recirculation valve based on the difference in the recirculation physical quantity calculated by the calculation means in each of the fully closed state of the recirculation valve and the state opened at the first opening; and Based on the difference in the reflux physical quantity calculated by the calculation means in each of the state opened at the first opening and the state opened at the second opening opened larger than the first opening. And a determination means having a second determination means for determining the state of the reflux valve ,
The determination means switches from determination by the first determination means to determination by the second determination means when the predetermined change condition is satisfied a plurality of times.
The second determination means determines that the reflux valve is abnormal when the predetermined change condition is first satisfied after switching to the determination by the second determination means . Diagnostic device for exhaust gas recirculation device. It the amount of change in the reflux physical quantity is less than a predetermined value, characterized in <br/> that said a predetermined change condition, diagnosis device for an exhaust gas recirculation apparatus according to claim 1. The changing means controls the opening degree of the reflux valve in at least two stages of a first opening degree that is opened larger than a fully closed state and a second opening degree that is opened larger than the first opening degree,
The calculating means includes a first reflux physical quantity of the reflux gas passing through the reflux valve opened at the first opening and a second reflux physical quantity of the reflux gas passing through the reflux valve opened at the second opening. and calculating the respective diagnostic device for an exhaust gas recirculation apparatus according to claim 1 or 2, wherein. A rotation speed detecting means for detecting the rotation speed of the internal combustion engine;
The exhaust gas recirculation according to any one of claims 1 to 3 , wherein the changing means changes the opening of the recirculation valve based on the rotation speed detected by the rotation speed detection means. A diagnostic device for circulatory devices. The change means has learning means for correcting the change amount of the opening degree of the reflux valve in the change control according to the return physical quantity, according to any one of claims 1 to 4. The diagnostic apparatus for the exhaust gas recirculation device described. The calculated output means, as an amount that reflects the differences in the reflux physical quantity, and calculates the amount of change in the intake pressure of the intake manifold of the internal combustion engine, according to any one of claims 1 to 5 Diagnostic device for exhaust gas recirculation device. The calculated output means, as an amount that reflects the differences in the reflux physical quantity, and calculates the amount of change in intake air temperature of the intake manifold of the internal combustion engine, according to any one of claims 1 to 6 Diagnostic device for exhaust gas recirculation device. The calculated output means, as an amount that reflects the differences in the reflux physical quantity, and calculates the amount of change in the recirculation gas temperature in the reflux passage downstream of the reflux valve, one of claims 1 to 7 The diagnostic apparatus for an exhaust gas recirculation device according to item 1. The exhaust according to any one of claims 1 to 8 , wherein the determination means determines that the recirculation valve is clogged when the amount of change in the recirculation physical quantity is less than a predetermined value. Diagnostic device for recirculation device.

Images