JP2006250052A - Secondary air feed device of internal combustion engine and controller of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately perform trouble-shooting by increasing the reliability of a detection output by a pressure sensor 15 during a closing operation for driving an air pump 13 in the closed state of a solenoid valve 12 when the air pump 13 is trouble-diagnosed in a secondary air feed device 10 of an internal combustion engine 1. <P>SOLUTION: In the closing operation, when a closing pressure P<SB>1</SB>is higher than the set opening pressure P<SB>0</SB>of the solenoid valve 12, an air discharge capacity by the air pump 13 is lowered. Since the rise of a pressure in a closing area 11a can be suppressed, air leakage from the solenoid valve 12 to an exhaust gas passage 5 can be prevented from occurring during the closing operation. Accordingly, the pulsation of exhaust gases in the exhaust gas passage 5 due to the air leakage does not occur, and the detection output of the pressure sensor 15 in the closing operation is less varied and the closing operation is stabilized. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a secondary air supply device for an internal combustion engine and a control device for the internal combustion engine.

  In an internal combustion engine mounted on a vehicle such as an automobile, air is exhausted into an exhaust passage in order to purify carbon monoxide (CO) and hydrocarbons (HC) in exhaust gas, for example, when starting from a cold state. There is a thing provided with the secondary air supply device which supplies (for example, refer to patent documents 1 and 2).

That is, when air is supplied to the exhaust passage, oxygen in the air reacts with carbon monoxide and hydrocarbons in the exhaust, and these are oxidized to carbon dioxide (CO ₂ ) and water (H ₂ O). Purification of carbon monoxide and hydrocarbons in the exhaust gas will be achieved.

  The secondary air supply device includes a supply passage connected to the exhaust passage, an electromagnetic valve that opens or closes the supply passage, and an air pump that discharges air to the supply passage.

  By the way, a failure diagnosis may be performed on the air pump as to whether or not the back pressure (air pump discharge pressure) is equal to or higher than a specified pressure.

  When performing this failure diagnosis, a closing operation, that is, an operation of driving the air pump with the solenoid valve closed, is performed to check whether the back pressure of the air pump is equal to or higher than a specified pressure.

  Note that the back pressure of the air pump is detected by a pressure sensor provided in a shut-off region in the supply passage. Further, the electromagnetic valve has a normally closed structure in which the valve body is closed by the elastic biasing force of the coil spring when not energized and the valve body is opened against the elastic biasing force of the coil spring when energized.

For such fault diagnosis, for example, an on-board function diagnostic system (OBD) is used.
JP 2004-293426 A JP 2004-285877 A

  In the shutoff operation accompanying the failure diagnosis of the air pump, if the shutoff pressure in the shutoff region in the supply passage is higher than the set opening pressure of the solenoid valve, the air in the shutoff region leaks from the solenoid valve and flows into the exhaust passage. It will be.

  When such an air leak occurs, exhaust pulsation occurs in the exhaust passage, which causes pressure fluctuations in the deadline area due to the exhaust pulsation, causing variations in the detection output by the pressure sensor, etc. Diagnosis cannot be performed accurately.

  The present invention prevents air leakage from a valve that is closed in a shutoff operation associated with failure diagnosis of an air pump, improves the reliability of detection output by a pressure sensor, and makes it possible to accurately perform failure diagnosis. It is an object.

  A secondary air supply device for an internal combustion engine according to the present invention includes a supply passage connected to an exhaust passage of the internal combustion engine, a valve for opening or closing the supply passage, an air pump for discharging air to the supply passage, A pressure sensor provided in a supply passage from an air pump to the valve, and when the shut-off pressure in the shut-off operation accompanying the failure diagnosis of the air pump is higher than a set opening pressure of the valve, air discharge by the air pump It is configured to reduce the capacity and adjust the cutoff pressure to be equal to or lower than the set opening pressure of the valve.

  The shutoff operation of the air pump is usually an operation of driving the air pump with the valve closed, and is performed when a failure diagnosis is performed to determine whether or not the discharge pressure of the air pump is greater than a specified value.

  According to such a configuration, when the shut-off pressure becomes higher than the valve opening set pressure during the shut-off operation, the air supply to the shut-off area in the supply passage is reduced to suppress the pressure increase in the shut-off area. The discharge pressure of the air pump added to the valve is reduced, and air leakage from the valve is prevented. As a result, air leakage from the supply passage to the exhaust passage can be prevented during the closing operation, so that exhaust pulsation does not occur in the exhaust passage, and the detection output of the pressure sensor in the closing operation is less likely to vary.

  In the secondary air supply device, the valve may be configured to close the valve body with a spring biasing force of the coil spring and open the valve body against the spring spring force of the coil spring as necessary. it can.

  In this case, if the cutoff pressure becomes higher than the valve opening set pressure during the cutoff operation, the air in the cutoff region leaks through the valve and leaks into the exhaust passage. When the valve having such a structure is used in the secondary air supply device, the air supply suppressing operation in the cutoff region is particularly effective.

  In the above secondary air supply device, it has a drive means for controlling a drive voltage supplied to the drive motor of the air pump, and the drive is performed when a cutoff pressure in the cutoff operation is higher than a set opening pressure of the valve. The rotational speed of the air pump can be reduced by lowering the drive voltage supplied to the drive motor of the air pump by means.

  According to such a configuration, it is only necessary to perform a process for controlling the drive voltage for the drive motor of the air pump, which is advantageous in suppressing an increase in equipment cost.

  A control device for an internal combustion engine according to the present invention controls various operations of the internal combustion engine in accordance with an operation state of the internal combustion engine including the secondary air supply device, and includes an air pump provided in the secondary air supply device. The failure diagnosis is performed by determining whether or not the discharge pressure of the air pump is more than a specified value in a state in which the shutoff operation for driving the air pump is performed with the valve closed. During the failure diagnosis, the pressure sensor detects the cutoff pressure, and if the detected cutoff pressure is higher than the valve opening set pressure, the air discharge capacity of the air pump is reduced. An operation or an operation of lowering the drive voltage of the drive means is performed, and a process of adjusting the shut-off pressure to be equal to or less than the valve opening set pressure is executed.

  According to such a configuration, since it is sufficient to simply control the drive voltage supplied from the drive means to the drive motor of the air pump, it is advantageous in suppressing an increase in equipment cost.

  According to the present invention, it is possible to improve the reliability of the detection output by the pressure sensor in the shut-off operation associated with the failure diagnosis of the air pump, thereby enabling accurate diagnosis.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a schematic configuration of an automobile engine as an internal combustion engine. In the engine 1 shown in this figure, an air-fuel mixture composed of fuel injected from the fuel injection valve 2 and air sucked from the intake passage 3 is combusted in the combustion chamber 4, and the air-fuel mixture after combustion serves as exhaust. It is sent to the exhaust passage 5 and purified by the catalytic converter 6.

  In FIG. 1, 7 is a spark plug and 8 is an air cleaner.

  The engine 1 is provided with a secondary air supply device 10 and a control device (ECU) 20.

  The secondary air supply device 10 promotes the purification of carbon monoxide and hydrocarbons in the exhaust by supplying air to the exhaust passage 5, and includes a supply passage 11, an electromagnetic valve 12, an electric motor An air pump 13, an oxygen sensor 14, a pressure sensor 15, and a drive circuit 16 are included.

  The supply passage 11 is connected to the exhaust passage 5, and an air pump 13 is provided upstream of the supply passage 11. Although not shown, the downstream side of the supply passage 11 is branched according to the number of combustion chambers 4 of the engine.

  The electromagnetic valve 12 is provided downstream of the supply passage 11 and opens or closes the supply passage 11. Although not shown in detail, the electromagnetic valve 12 closes the valve body with the elastic biasing force of the coil spring when not energized, and opens the valve body against the elastic biasing force of the coil spring when energized. It is a normally closed structure.

  The air pump 13 supplies air to the supply passage 11, and a filter 17 is provided at the suction port of the air pump 13.

  The oxygen sensor 14 is provided upstream of the catalytic converter 6 in the exhaust passage 5 and detects the oxygen concentration in the exhaust passage 5.

  The pressure sensor 15 is provided between the electromagnetic valve 12 and the air pump 13 in the supply passage 11, and detects the pressure there.

  The drive circuit 16 drives a drive motor (not shown) of the electromagnetic valve 12 and the air pump 13 based on a signal received from the control device 20.

Such a secondary air supply device 10 is used when the amount of carbon monoxide (CO) or hydrocarbon (HC) in the exhaust gas increases, such as when the engine 1 is started in a cold state. By driving the air pump 13 with the valve 12 open, the air discharged from the air pump 13 is sent to the exhaust passage 5 through the supply passage 11. In the exhaust passage 5, oxygen in the supplied air reacts with carbon monoxide and hydrocarbons in the exhaust, which are carbon dioxide (CO ₂
) And water (H ₂ O).

  The control device 20 is mainly mounted on an automobile and performs various operation controls of the engine 1 in accordance with the operation status of the engine 1. At least the control related to the secondary air supply and the control related to the function diagnosis described below are performed. To do.

  First, the secondary air supply is performed by outputting an appropriate signal to the drive circuit 16 based on detection signals from the oxygen sensor 14, the pressure sensor 15 and the like, and driving the electromagnetic valve 12 and the air pump 13 by the drive circuit 16. An appropriate amount of air is supplied to the exhaust passage 5.

  The function diagnosis includes a failure diagnosis of the air pump 13 in the secondary air supply device 10.

  Specifically, the failure diagnosis of the air pump 13 is performed by a shut-off operation that drives the air pump 13 with the solenoid valve 12 closed, and whether or not the back pressure (discharge pressure) of the air pump 13 is equal to or higher than a predetermined specified pressure. The air pump 13 is checked to determine whether there is an abnormality.

  The back pressure of the air pump 13 is detected by a pressure sensor 15 provided in a cut-off area 11 a between the electromagnetic valve 12 and the air pump 13 in the supply passage 11.

  Incidentally, it is preferable to perform such a failure diagnosis when, for example, an engine operating condition in which it is not necessary to supply air from the secondary air supply device 10 to the exhaust passage 5.

  In this embodiment, the control device 20 is equipped with at least a failure diagnosis function of the air pump 13 among various diagnosis functions by a conventionally known on-board function diagnosis system (OBD: On-Board-Diagnostic-System). ing. However, the control device 20 may be configured to perform a failure diagnosis of the air pump 13 by externally attaching an in-vehicle function diagnosis system without providing the function by the in-vehicle function diagnosis system.

When the shut-off operation associated with the failure diagnosis of the air pump 13 is performed, the shut-off pressure P ₁ in the shut-off region 11a in the supply passage 11 becomes higher than the opening set pressure P ₀ of the solenoid valve 12. Although described in detail in the item, the air in the cut-off area 11a leaks from the electromagnetic valve 12 and flows into the exhaust passage 5, which is not preferable.

Therefore, in this embodiment, when the cutoff pressure P ₁ in the cutoff operation is higher than the opening set pressure P ₀ of the solenoid valve 12, the cutoff pressure P ₁ of the solenoid valve 12 is reduced by reducing the air discharge capacity of the air pump 13. Since it is devised to adjust to the opening set pressure P ₀ or less, it will be described in detail below.

  Specifically, the air discharge capacity of the air pump 13 is reduced by controlling the drive voltage applied from the drive circuit 16 to the drive motor (not shown) of the air pump 13.

The control device 20 detects the cutoff pressure P ₁ with the pressure sensor 15 during the failure diagnosis of the air pump 13, and drives when the detected cutoff pressure P ₁ is higher than the set opening pressure P ₀ of the electromagnetic valve 12. The circuit 16 is configured to execute a process of adjusting the cutoff pressure P ₁ to be equal to or less than the opening set pressure P ₀ of the electromagnetic valve 12 by controlling the drive voltage supplied to the drive motor (not shown) of the air pump 13. ing.

  Next, failure diagnosis will be described with reference to the flowchart of FIG. 2 and the timing chart of FIG.

  Here, a case where the time for performing the failure diagnosis of the air pump 13 is set as the end time of the secondary air supply operation will be described as an example. Of course, this time may be any time as long as the secondary air supply operation is not performed during operation of the engine 1.

First, for example, when it is necessary to supply air from the secondary air supply device 10 to the exhaust passage 5 at time T ₁ shown in FIG. 3A, the electromagnetic valve 12 is opened. Then, air is supplied to the exhaust passage 5 by driving the air pump 13.

Although the secondary air supply operation is performed a predetermined time, at time T _2, as shown in FIG. 3 (a), the supply of secondary air is not required, in order to start a subsequent fault diagnosis, 2 The control sequence is entered, and the cutoff operation is performed in step S1 of FIG.

At this time, closes the solenoid valve 12 at time T _2, as shown in (a) of FIG. 3, the air to the supply passage 11 continues to drive the so air pump 13 as shown in FIG. 3 (b) Continue discharging.

  Thereafter, in step S2 of FIG. 2, as shown in FIG. 3C, the system is started up until the pressure in the shut-off region 11a between the air pump 13 and the electromagnetic valve 12 in the supply passage 11 rises. Wait until the required time t has elapsed.

When the time t has elapsed, the shutoff pressure P ₁ of the deadline region 11a is detected by the pressure sensor 15, in step S3 in FIG. 2, open set pressure P ₀ of the shutoff pressure P ₁ solenoid valve 12 detected by the pressure sensor 15 Compare whether it is higher or not.

Normally, when the cutoff pressure P ₁ detected by the pressure sensor 15 at the time T ₃ shown in FIG. 3C becomes higher than the set opening pressure P ₀ of the electromagnetic valve 12 by the cutoff operation, the “ In step S4 of FIG. 2, the drive voltage for the drive motor of the air pump 13 is lowered to lower the air discharge capability of the air pump 13. However, this time, the air temporarily in the deadline region 11a is sometimes leaked from the solenoid valve 12 in the exhaust passage 5, whereby the cutoff pressure P ₁ is equal to or less than the opening set pressure P ₀ of the solenoid valve 12 Will fall. Since this air leakage is temporary, exhaust pulsation may temporarily occur in the exhaust passage 5, but thereafter, air leakage to the exhaust passage 5 is prevented, so that the pressure fluctuation in the cut-off region 11a. Therefore, the detection output by the pressure sensor 15 for subsequent failure diagnosis does not vary.

That is, the air discharge capacity of the air pump 13 to be set in step S4, since the cutoff pressure P ₁ is set in a range not higher than the set pressure P ₀ opening of the solenoid valve 12, as shown by a chain line in FIG. 4 During the failure diagnosis of the air pump 13, the cutoff pressure P ₁ is adjusted to be equal to or less than the set opening pressure P ₀ of the solenoid valve 12, and the air in the cutoff region 11 a leaks from the solenoid valve 12 and exhausts. Occurrence of a problem of leaking into the passage 5 can be reliably prevented.

Thus, when the cutoff pressure P ₁ becomes equal to or less than the set opening pressure P ₀ of the solenoid valve 12, “NO” is determined in step S3, and the failure diagnosis determination process of the air pump 13 is performed in step S5 of FIG. Then go out of this sequence.

Incidentally, in the discrimination process in step S5, the detection output from the pressure sensor 15 is taken in as the back pressure (discharge pressure) of the air pump 13, and it is compared whether or not the detected back pressure of the air pump 13 is equal to or higher than the specified pressure. When the comparison result is equal to or higher than the specified pressure, it is determined that the air pump 13 is normal. On the other hand, when the comparison result is less than the specified pressure, it is determined that the air pump 13 is abnormal. This determination is, for example, ends at time T ₄ shown in FIG. 3 (b), stops the driving of the air pump 13, and ends the failure diagnosis.

In the determination process, the specified pressure of the air pump 13 is set corresponding to the drive voltage supplied to the drive motor of the air pump 13 set in step S4. In general, the discharge pressure of the air pump 13 has a linear relationship with the drive voltage supplied to the drive motor of the air pump 13, so the relationship between the discharge pressure and the drive voltage in advance depends on the type and specifications of the air pump 13 to be used. If the map data to be represented is stored in the control device 20, the fault diagnosis can be performed accurately.

  As described above, according to this embodiment, it is possible to prevent air leakage from the solenoid valve 12 to the exhaust passage 5 during the shut-off operation of the secondary air supply device 10, so that the air leakage is the cause. Thus, no exhaust pulsation occurs in the exhaust passage 5.

  As a result, the detection output of the pressure sensor 15 in the deadline operation is less likely to vary and stabilizes, so that the reliability of the detection output is improved. Therefore, the failure diagnosis of the air pump 13 by the control device 20 can be performed accurately.

  In addition, during the failure diagnosis of the air pump 13, the operation of reducing the air discharge capacity of the air pump 13 can reduce the burden on the air pump 13 and suppress the temperature rise of the air pump 13, thereby contributing to improving the durability of the air pump 13. It becomes.

  Hereinafter, other embodiments of the present invention will be described.

  (1) In the above embodiment, the solenoid valve 12 can be either an on-off valve that switches between a fully open state and a fully closed state, or a flow rate adjustment valve that can arbitrarily adjust the opening.

(2) In the above embodiment, the waste pressure of the configuration is eliminated by detecting the shutoff pressure P ₁ of the air pump 13 and the back pressure of the air pump 13 by the same pressure sensor 15, but it is detected individually by separate pressure sensors. You may make it do.

  (3) In the above embodiment, the position where the pressure sensor 15 is provided may be changed as appropriate as long as it is within the deadline region 11a.

It is a schematic structure figure of an engine provided with one embodiment of the secondary air supply device concerning the present invention. It is a flowchart used for description of failure diagnosis of the air pump shown in FIG. It is a time chart used for operation | movement description of the secondary air supply apparatus shown in FIG. It is a graph which shows the flow volume characteristic (PQ characteristic) of the air pump of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 5 Exhaust passage 6 Catalytic converter 10 Secondary air supply device 11 Supply passage 11a Supply passage cut-off area 12 Solenoid valve 13 Air pump 15 Pressure sensor 16 Drive circuit 20 Control device

Claims (4)

A supply passage connected to an exhaust passage of the internal combustion engine; a valve for opening or closing the supply passage; an air pump for discharging air to the supply passage; and a pressure sensor provided in a supply passage from the air pump to the valve; A secondary air supply device comprising:
When the shut-off pressure in the shut-off operation associated with the failure diagnosis of the air pump is higher than the valve opening set pressure, the air discharge capacity of the air pump is lowered to adjust the shut-off pressure to be equal to or less than the valve opening set pressure. A secondary air supply device for an internal combustion engine, characterized in that it is configured.   2. The valve according to claim 1, wherein the valve has a structure in which the valve body is closed by a resilient urging force of a coil spring and the valve body is opened against the resilient urging force of the coil spring as necessary. Secondary air supply device for internal combustion engine. Drive means for controlling the drive voltage supplied to the drive motor of the air pump;
When the shut-off pressure in the shut-off operation is higher than the set opening pressure of the valve, the rotational speed of the air pump is lowered by lowering the drive voltage supplied to the drive motor of the air pump by the drive means. The secondary air supply device for an internal combustion engine according to claim 1 or 2. A control device that performs various types of operation control of an internal combustion engine in accordance with an operation state of the internal combustion engine including the secondary air supply device according to claim 1,
Control for failure diagnosis of the air pump provided in the secondary air supply device,
The fault diagnosis is to check whether there is an abnormality by determining whether or not the discharge pressure of the air pump is higher than a specified value in a state in which the shutoff operation for driving the air pump is performed with the valve being closed,
During the fault diagnosis, the pressure sensor detects the shut-off pressure, and when the detected shut-off pressure is higher than the valve opening set pressure, the operation of reducing the air discharge capacity by the air pump or the drive voltage of the drive means A control device for an internal combustion engine, which performs a process of adjusting the shut-off pressure to be equal to or less than an opening set pressure of the valve by performing an operation of lowering the valve.

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