JP2006283712A - Freeze determination device for secondary air supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly perform freeze determination at a time of engine start and protect a secondary air supply device. <P>SOLUTION: The secondary air supply device including a secondary air piping 31, an air pump 32 and an open close valve 33 is provided in an exhaust side of an engine 10, and secondary air is supplied to an exhaust pipe 28 by the secondary air supply device. ECU 40 acquires intake air temperature and engine water temperature as temperature parameters at engine start, and determine whether the secondary air supply device freezes or not based on the acquired temperature parameters. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a freezing determination device for a secondary air supply device.

  The exhaust pipe of the engine is provided with an exhaust purification device such as a catalyst for purifying exhaust gas, and secondary air is supplied to the upstream side of the exhaust purification device in order to improve the purification efficiency of the exhaust purification device. Technology has been proposed in the past. Specifically, as the secondary air supply device, a secondary air pipe connected to the exhaust pipe of the engine is provided, and an air pump and an on-off valve are provided in the middle of the secondary air pipe. For example, when the engine is started, the air pump is driven and the on-off valve is opened to supply secondary air into the exhaust pipe.

  Further, in such a secondary air supply device, if an abnormality occurs in the air pump or the on-off valve, the purification efficiency of the exhaust gas is reduced, and the emission is deteriorated. Therefore, a technique for detecting an abnormality in the secondary air supply device has been proposed. For example, in Patent Document 1, when a failure diagnosis result during cold is predicted to be abnormal due to freezing of the secondary air supply system, re-determination is performed after warm-up. Thereby, a temporary abnormality due to freezing can be determined.

  In Patent Document 1, the following method is disclosed as a specific method for determining whether or not the secondary air supply device is frozen. That is, when starting the engine, the on-off valve is opened and the air pump is driven to supply secondary air to the exhaust pipe through the secondary air piping. Then, the pressure in the secondary air piping is detected by a pressure sensor, and whether or not each component (air pump, on-off valve, etc.) of the secondary air supply device is frozen based on the behavior of the detected pressure value. judge.

However, in the above-described prior art, when determining the freezing, the behavior of pressure must be monitored in the secondary air supply state, and it takes time for the freezing determination. In addition, since the air pump can be driven in a state where the air passage is closed due to freezing, an excessive load is applied to the air pump, which may cause a failure. Therefore, there is a demand for an improved technique that can quickly determine freezing when the engine is started and that does not hinder the air pump or the like.
JP 2003-201834 A

  The main object of the present invention is to provide a freezing determination device for a secondary air supply device that can quickly determine freezing when the engine is started and that can protect the secondary air supply device.

  In the present invention, it is assumed that a secondary air supply device having a secondary air passage, an on-off valve, and an air pump is provided, and the secondary air is supplied to the exhaust passage by the secondary air supply device. . In particular, a temperature parameter correlated with the temperature of the parts constituting the secondary air supply device at the time of starting the engine is acquired, and it is determined whether or not the secondary air supply device is frozen based on the acquired temperature parameter. To do.

  According to the present invention, the freezing determination of the secondary air supply device is performed based on the temperature parameter acquired when the engine is started (specifically, when the start switch is turned on). Can do. In this case, since it is not necessary to monitor the pressure behavior under the secondary air supply state, it does not take time for the freezing determination. Moreover, it can suppress that an excessive load is applied to the air pump. As described above, it is possible to perform the freezing determination as soon as the engine is started and to protect the secondary air supply device.

  It is preferable to determine whether the secondary air supply device is frozen based on the intake air temperature detected at the time of starting the engine, including at least the intake air temperature as a temperature parameter. Specifically, it may be determined that the secondary air supply device is frozen when the intake air temperature is lower than a predetermined freezing determination value. In this case, since an intake temperature sensor that is normally provided as an engine control system may be used, inconveniences such as a complicated configuration and an increase in cost can be avoided. The freezing judgment value is set to a low temperature value that is likely to cause the secondary air supply device to freeze, and is, for example, about -20 to 0 ° C.

  However, assuming that the secondary air supply device is frozen and the engine is once started and then stopped in the frozen state, and then the engine is restarted, the engine is once started. Thus, the temperature in the engine room rises and the intake air temperature rises, but the secondary air supply device remains frozen. That is, for example, when the valve temperature of the on-off valve is compared with the intake air temperature, the valve temperature is less than the intake air temperature (in the case where the engine stop time is sufficiently long, the valve temperature is substantially equal to the intake air temperature). Therefore, there are cases where accurate freezing determination is not performed only with the intake air temperature.

  Therefore, the stop time from the last stop of the engine is measured, and when the measured stop time is shorter than a predetermined determination value (that is, when the engine stop time is relatively short), the determination is made on the safer side. It is preferable to determine that the secondary air supply device is frozen or has a possibility of freezing. Thereby, it is possible to eliminate the omission of determination in the case of actual freezing. The determination value is a time for determining that the valve temperature of the on-off valve and the intake air temperature substantially coincide with each other, and may be about several hours (for example, 5 to 10 hours).

  Here, basically, the higher the intake air temperature detected when the engine is started, the lower the possibility of freezing of the secondary air supply device. Therefore, the determination value may be variably set according to the intake air temperature. More specifically, the determination value may be reduced as the intake air temperature increases. Thereby, the accuracy of the freezing determination of the secondary air supply device is improved. Further, if the determination value is decreased as the intake air temperature is higher, the number of cases where it is determined that the secondary air supply device is not frozen increases, so the opportunity for secondary air supply can be increased.

  Also, if it is determined that the engine stop time is shorter than the predetermined freezing occurrence time required for freezing of the secondary air supply device and the previous determination result is not frozen, the engine is also frozen this time. It is good to make a determination that there is not. Here, the freezing occurrence time is a time of about several tens of minutes (for example, 15 to 60 minutes). In other words, if the engine stop time is shorter than the freezing time, it is unlikely that a new freezing will occur in the secondary air supply device, and the state of freezing / freezing is almost unchanged from the previous engine operation. It is believed that there is. Therefore, the freezing determination similar to the previous freezing determination result may be performed.

  When it is determined that the secondary air supply device is frozen, the secondary air supply by the secondary air supply device may be prohibited. Thereby, the failure etc. by trying to drive an on-off valve and an air pump in the frozen state can be prevented.

  At the time of secondary air supply by the secondary air supply device, it is conceivable to increase the amount of fuel supplied to the engine in response to the secondary air supply. In such a case, when it is determined that the secondary air supply device is frozen, it is preferable to prohibit an increase in the fuel supply amount in accordance with the secondary air supply. Thereby, when the secondary air supply cannot be normally performed, the excessive supply of fuel is suppressed (that is, the excessive enrichment is suppressed), and the deterioration of the exhaust emission can be suppressed.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, an engine control system is constructed for an in-vehicle multi-cylinder gasoline engine that is an internal combustion engine. In the control system, an electronic control unit (hereinafter referred to as ECU) is used as a center to control the fuel injection amount. And control of ignition timing. First, an overall schematic configuration diagram of the engine control system will be described with reference to FIG.

  In the engine 10 shown in FIG. 1, an air cleaner 12 is provided at the most upstream portion of the intake pipe 11, and an air flow meter 13 for detecting the intake air amount is provided downstream of the air cleaner 12. The air flow meter 13 incorporates an intake air temperature sensor 14 for detecting the temperature of the intake air. A throttle valve 15 whose opening is adjusted by an actuator such as a DC motor and a throttle opening sensor 16 for detecting the throttle opening are provided on the downstream side of the air flow meter 13. A surge tank 17 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 18 for detecting the intake pipe pressure is provided in the surge tank 17.

  The surge tank 17 is connected to an intake manifold 19 that introduces air into each cylinder of the engine 10. In the intake manifold 19, an electromagnetically driven fuel injection that supplies fuel to the vicinity of the intake port of each cylinder. A valve 20 is attached. Fuel is supplied to the fuel injection valve 20 from a fuel tank 22, a fuel pump 23, and a delivery pipe 24 connected by a fuel pipe 21, and fuel injection is supplied to each cylinder of the engine as the fuel injection valve 20 is energized. Is done.

  An intake valve 25 and an exhaust valve 26 are respectively provided at the intake port and the exhaust port of the engine 10. When the intake valve 25 is opened, a mixture of air and fuel is introduced into the combustion chamber, and the exhaust valve 26 is opened. The exhaust after combustion is discharged to the exhaust manifold 27 by the operation. Although not shown, a spark plug is attached to each cylinder head of the engine 10 for each cylinder, and a spark discharge is generated between the opposing electrodes of the plug by application of a high voltage to the spark plug, which is introduced into the combustion chamber. The air-fuel mixture is ignited and used for combustion. An exhaust pipe 28 connected to the downstream side of the exhaust manifold 27 is provided with a catalyst 29 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas.

  As a secondary air supply device, a secondary air pipe 31 is connected upstream of the catalyst 29 in the exhaust pipe 28, and a secondary air pump 32 is provided upstream of the secondary air pipe 31. . The secondary air pump 32 is composed of, for example, a DC motor or the like and operates by receiving power from a vehicle battery (not shown). Further, an on-off valve 33 for opening or closing the secondary air pipe 31 is provided on the downstream side of the secondary air pump 32.

  Further, in the present control system, a water temperature sensor 35 that detects the temperature of the engine coolant, or a crank angle sensor 36 that outputs a rectangular crank angle signal at every predetermined crank angle of the engine 10 (for example, at a cycle of 30 ° CA). Is provided.

  The outputs of the various sensors described above are input to the ECU 40 that controls the engine. The ECU 40 is mainly composed of a microcomputer including a CPU, a ROM, a RAM, and the like, and executes various control programs stored in the ROM, so that the fuel injection amount and ignition of the fuel injection valve 20 according to the engine operating state. Controls ignition timing by plug. In addition, the ECU 40 supplies the secondary air by operating the secondary air pump 32 in order to activate the catalyst 29 at the time of engine start. When the secondary air is supplied, the fuel injection amount is increased according to the secondary air supply amount.

  The ECU 40 is provided with a soak timer 41 for measuring the elapsed time while the engine is stopped (that is, when the ignition switch is OFF). The soak timer 41 performs a counting operation by supplying a backup voltage when the ignition switch is OFF.

  By the way, in cold districts, the secondary air piping 31, the secondary air pump 32, and the on-off valve 33 constituting the secondary air supply device are frozen, and the secondary air supply cannot be performed due to the freezing. Arise. If the secondary air supply is not performed by freezing when it should be performed, there is a disadvantage that the air-fuel ratio becomes excessively rich due to the fuel increase corresponding to the secondary air supply. Therefore, in the present embodiment, the freezing determination of the secondary air supply device is performed based on the temperature parameters such as the intake air temperature Tin and the engine water temperature Tw and the time elapsed since the previous engine stop (engine stop time T_stop). Then, when it is determined that the secondary air supply device is frozen, the fuel increase corresponding to the secondary air supply is stopped, and over-rich due to the fuel increase and the accompanying deterioration in exhaust emission are avoided.

  The intake air temperature Tin is calculated from the detected value of the intake air temperature sensor 14, and the engine water temperature Tw is calculated from the detected value of the water temperature sensor 35. The engine stop time T_stop is calculated from the count value of the soak timer 41.

Next, a method for determining freezing will be described. In the present embodiment, when the engine is started, that is, when the power to the ECU 40 is turned on when the ignition switch is turned on, whether or not the next freezing determination condition is satisfied is determined, and if at least one of them is satisfied, the secondary air supply Determine that the device is frozen.
(1) The intake air temperature Tin is smaller than a predetermined freezing determination value Ka.
(2) The engine water temperature Tw is smaller than a predetermined fixed value Kb.
At this time, the intake air temperature Tin and the engine water temperature Tw correspond to temperature parameters correlated with the temperatures of the components constituting the secondary air supply device. The freezing determination values Ka and Kb are set to low temperature values that are likely to cause the secondary air supply device to freeze, and are each about -15 ° C, for example.

  If either of the above (1) and (2) is established, it can be immediately determined that it is frozen, but the secondary air supply device can be frozen even if (1) and (2) are not established. It is thought that there is sex. That is, after the engine 10 is once started in a state where the secondary air supply device is frozen in a cryogenic environment, the engine is stopped in the frozen state, and the engine 10 is restarted immediately after the stop. Assuming that In this case, once the engine 10 is started, the temperature in the engine room rises and the intake air temperature Tin rises accordingly, but the secondary air supply device remains frozen. In other words, for example, when the valve temperature of the on-off valve 33 and the intake air temperature Tin are compared, the valve temperature <the intake air temperature Tin (the valve temperature≈the intake air temperature Tin when the engine stop time is sufficiently long). Therefore, it is considered that accurate freezing determination is not performed only with the intake air temperature Tin.

  Therefore, in order to eliminate a determination omission when the vehicle is actually frozen, the secondary air supply device when the engine stop time T_stop is shorter than the predetermined first determination value α (that is, when the engine stop time is relatively short). Is determined to be frozen. When the engine stop time T_stop is equal to or longer than the first determination value α, it is basically determined that the secondary air supply device is not frozen. The first determination value α is a specified time required for the intake air temperature and the valve temperature to substantially coincide with each other, and is a value corresponding to, for example, about 5 hours.

  In addition, when the engine stop time T_stop is very short, it is considered that the engine is temporarily stopped and then restarted. In such a case, the possibility of new freezing in the secondary air supply device is low, and the state of freezing / freezing of the secondary air supply device is considered to be almost unchanged from the previous engine operation. Therefore, the result of the previous freezing determination can be used without immediately determining that the secondary air supply device is frozen. That is, when the engine stop time T_stop is less than the predetermined second determination value β, if the previous freezing determination result is freezing, that result is adopted, and the current freezing determination result is also free. The second determination value β is a time required for freezing of the secondary air supply device (freezing occurrence time), and is a value corresponding to a time of about 30 minutes, for example.

  FIGS. 2 and 3 are flowcharts showing the freezing determination process of the secondary air supply device. This process is executed only when the ECU 40 is turned on (that is, only once after the ignition switch is turned on). Note that the first determination values α1 and α2 used in this process correspond to the first determination value α described above, and the second determination values β1 and β2 correspond to the second determination value β described above.

  In FIG. 2, first, in step S101, a default value for freezing determination is set. That is, here, a determination result indicating that the image is frozen is set as a default value.

  Thereafter, the freezing determination based on the intake air temperature Tin and the engine water temperature Tw is performed. That is, in step S102, it is determined whether or not the intake air temperature Tin is equal to or higher than a predetermined freezing determination value Ka (for example, −15 ° C.). In step S103, the engine water temperature Tw is determined to be a predetermined freezing determination value Kb (for example −15). ° C) or higher. If Tin <Ka or Tw <Kb, the process proceeds to step S110, where it is determined that the secondary air supply device is frozen.

  If Tin ≧ Ka and Tw ≧ Kb, the process proceeds to step S104, and block heater determination is performed. The block heater is provided as a means for preventing freezing of engine cooling water in a cold region specification vehicle, and is attached to the engine block, for example. When the car is stored in a garage or the like at night, heat is generated by connecting to an external power source, and the engine is kept warm. Specifically, the processing in step S104 is based on temperature information (engine water temperature, intake air temperature, etc.) at the previous engine stop, temperature information (engine water temperature, outside air temperature, etc.) at the current start, and engine stop time. Then, it is estimated whether or not the block heater has been used until the current engine start.

  If the block heater is not used, step S105 is positively determined and the process proceeds to step S106. If the block heater is used, step S105 is negatively determined and the process proceeds to step S111 in FIG.

  In steps S106 to S110, the freezing determination is performed based on the engine stop time T_stop. That is, in step S106, it is determined whether the engine stop time T_stop is longer than the first determination value α1. When T_stop> α1, the process proceeds to step S109, and it is determined that the secondary air supply device is not frozen. As described above, the first determination value α1 is a value corresponding to, for example, about 5 hours.

  When T_stop ≦ α1, the process proceeds to step S107, and it is determined whether or not the engine stop time T_stop is shorter than a second determination value β1 (for example, a value corresponding to a time of about 30 minutes). When T_stop ≧ β1, the process proceeds to step S110, and it is determined that the secondary air supply device is frozen.

  In the case of T_stop <β1, since it is considered that the engine is restarting, the previous freeze determination result is adopted. At this time, in step S108, it is determined whether or not the previous freezing determination is no freezing. If the previous freezing determination is not performed, the determination of no freezing is similarly performed this time (step S109).

  Further, when it is determined that the block heater is used, in steps S111 to S115 in FIG. 3, the freezing determination is performed based on the engine stop time T_stop in the same manner as in steps S106 to S110. That is, in step S111, it is determined whether or not the engine stop time T_stop is longer than the first determination value α2. When T_stop> α2, the process proceeds to step S114, and it is determined that the secondary air supply device is not frozen. Since it is considered that the possibility of freezing is high when the block heater is used, the first determination value α2 may be larger than the first determination value α1 when the block heater is not used. The corresponding value.

  When T_stop ≦ α2, the process proceeds to step S112, and it is determined whether or not the engine stop time T_stop is shorter than a second determination value β2 (for example, a value corresponding to a time of about 30 minutes). When T_stop ≧ β2, the process proceeds to step S115, and it is determined that the secondary air supply device is frozen. Since the outside air temperature is low when the block heater is used and the possibility of new freezing is high, the second determination value β2 is set to a value smaller than the second determination value β1 when the block heater is not used (for example, 15). It may be changed to about minutes).

  In the case of T_stop <β2, since it is considered that the engine is restarting, the previous freeze determination result is adopted. At this time, in step S113, it is determined whether or not the previous freezing determination was no freezing. If the previous freezing determination was not made, the determination of no freezing is similarly performed this time (step S114).

  When it is determined that the secondary air supply device is frozen by the above freeze determination processing, the secondary air supply by the secondary air supply device is prohibited and the fuel injection amount corresponding to the secondary air supply is increased. Is prohibited.

  According to the embodiment described above in detail, the following excellent effects can be obtained.

  Since the freezing determination of the secondary air supply device is performed based on the intake air temperature Tin and the engine water temperature Tw as temperature parameters acquired at the time of starting the engine, the freezing determination can be performed as soon as the engine is started. In this case, since it is not necessary to monitor the pressure behavior under the secondary air supply state, it does not take time for the freezing determination. Moreover, it can suppress that the excessive load is applied to the secondary air pump 32. As described above, it is possible to perform the freezing determination as soon as the engine is started and to protect the secondary air supply device.

  A pressure sensor is not required for determining whether or not the secondary air supply device is frozen, thereby realizing a cost reduction effect. The temperature sensors for detecting the intake air temperature Tin and the engine water temperature Tw are usually provided as an engine control system, and the use of these temperature sensors does not complicate the configuration or increase the cost. I can say no.

  When it is determined that the secondary air supply device is frozen, secondary air supply by the secondary air supply device is prohibited, so that the secondary air pump 32 and the opening / closing valve 33 are driven in the frozen state. It is possible to prevent malfunctions and the like.

  Further, when it is determined that the secondary air supply device is frozen, an increase in the fuel injection amount corresponding to the secondary air supply is prohibited, so that excessive fuel supply is suppressed (that is, over-riching is suppressed). As a result, deterioration of exhaust emission can be suppressed.

  When the intake air temperature Tin and the engine water temperature Tw are relatively high, the presence or absence of freezing is determined according to the engine stop time T_stop. Thereby, it is possible to avoid a determination omission that the secondary air supply device is actually in a frozen state but cannot be determined.

  In addition, since the previous determination result is adopted when the engine is restarted, when the engine stop time T_stop is relatively short (when T_stop <α), it is not determined that there is freezing, but the previous determination Judgment of freezing can be performed according to the result.

  In addition, this invention is not limited to the content of description of the said embodiment, For example, you may implement as follows.

  The determination values α and β for determining the engine stop time T_stop may be variably set according to the intake air temperature Tin when the engine is started. For example, the determination values α and β are set based on the relationship shown in FIG. According to the relationship of FIG. 4, when the intake air temperature is less than 0 ° C., the lower the intake air temperature, the larger the determination value is set. When the intake air temperature is 0 ° C. or more, the determination value is 0. Fixed. By setting the determination values α and β in this manner, it is less likely that the secondary air supply device is determined to be frozen when the intake air temperature Tin at the time of starting the engine is relatively high. Thereby, the accuracy of the freezing determination of the secondary air supply device is improved. Further, if the determination value is decreased as the intake air temperature Tin at the time of starting the engine is higher, the number of cases where it is determined that the secondary air supply device is not frozen increases, so the opportunity for secondary air supply can be increased. In FIG. 4, the threshold value of the intake air temperature Tin for which the determination value = 0 can be changed to a temperature higher than 0 ° C.

  In the above embodiment, the intake air temperature Tin and the engine water temperature Tw are used as temperature parameters, and the freezing of the secondary air supply device is determined by determining these Tin and Tw. Of these, the freezing determination is performed using only the intake air temperature Tin. It is also possible to implement.

It is a block diagram which shows the outline of the engine control system in embodiment of invention. It is a flowchart which shows the freezing determination process of a secondary air supply apparatus. FIG. 3 is a flowchart illustrating a freezing determination process of the secondary air supply device, following FIG. 2. It is a figure which shows the relationship between intake temperature and determination value.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 14 ... Intake temperature sensor, 20 ... Fuel injection valve, 28 ... Exhaust pipe, 31 ... Secondary air piping, 32 ... Secondary air pump, 33 ... Open / close valve, 40 ... ECU.

Claims (7)

A secondary air supply device having a secondary air passage connected to the exhaust passage of the engine, an on-off valve and an air pump provided in the secondary air passage, and the secondary air supply device In the secondary air supply system for supplying secondary air to the exhaust passage,
Means for acquiring a temperature parameter correlated with the temperature of the parts constituting the secondary air supply device at the time of engine start;
Means for determining whether or not the secondary air supply device is frozen based on the acquired temperature parameter;
A freeze determination device for a secondary air supply device, comprising: Means for detecting the temperature of the intake air taken into the engine;
2. The freezing of the secondary air supply device according to claim 1, wherein at least the intake air temperature is included as the temperature parameter, and the freezing determination of the secondary air supply device is performed based on the intake air temperature detected when the engine is started. Judgment device. Means for calculating a stop time since the engine was last stopped;
3. The method according to claim 1, wherein when the calculated stop time is shorter than a predetermined determination value, it is determined that the secondary air supply device is frozen or has a possibility of freezing. Freezing judgment device for secondary air supply device.   The freeze determination device for a secondary air supply device according to claim 3, wherein the determination value is variably set according to an intake air temperature. Means for calculating a stop time since the engine was last stopped;
If it is determined that the engine stop time is shorter than the predetermined freezing occurrence time required for freezing of the secondary air supply device and the previous determination result is not frozen, the engine is also frozen this time as well. The freezing determination device for a secondary air supply device according to any one of claims 1 to 4, wherein a determination is made that there is no such effect.   6. The secondary air according to claim 1, wherein when it is determined that the secondary air supply device is frozen, secondary air supply by the secondary air supply device is prohibited. Freezing determination device for the supply device. Means for increasing the amount of fuel supplied to the engine in response to the secondary air supply at the time of secondary air supply by the secondary air supply device;
The secondary air supply device freezing determination according to any one of claims 1 to 6, wherein, when it is determined that the secondary air supply device is frozen, an increase in the fuel supply amount is prohibited. apparatus.

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