JP6350425B2 - Engine control device - Google Patents

Description

  The technology disclosed herein relates to an engine control device.

  Conventionally, an engine that supplies evaporated fuel generated in a fuel tank as a purge gas to an intake system is known.

  Since such purge gas affects the air-fuel ratio, it is necessary to accurately grasp the amount of evaporated fuel supplied to the intake system. For this purpose, it is necessary to accurately grasp the purge concentration, which is the fuel concentration in the purge gas.

  For example, in the engine according to Patent Document 1, air-fuel ratio feedback control is performed in which the actual air-fuel ratio is controlled to the target air-fuel ratio by adjusting the fuel injection amount based on the detection result of the oxygen sensor that detects the oxygen concentration in the exhaust gas. Yes. This engine compares the feedback correction value used in the air-fuel ratio feedback control before and after supplying the purge gas, and estimates the purge concentration from the deviation before and after that.

Japanese Patent Laid-Open No. 11-30159

  By the way, since the feedback correction value sequentially changes to adjust the actual air-fuel ratio, the deviation of the feedback correction value before and after the supply of the purge gas includes not only the fluctuation due to the purge gas but also the fluctuation for the air-fuel ratio control. Is also included. Therefore, the purge concentration estimation method of Patent Document 1 has room for improvement in the purge concentration estimation accuracy.

  However, even if the purge concentration can be accurately estimated by another estimation method, if it takes time to estimate the purge concentration, the opportunity to supply the purge gas is lost, which is not preferable. In particular, in a situation where there is a large amount of evaporated fuel, it is desirable to secure as much opportunity for supplying purge gas as possible.

  The technology disclosed herein has been made in view of such a point, and an object of the technology is to realize improvement in purge concentration estimation accuracy and securing of a purge gas supply opportunity.

  The technology disclosed herein is directed to an engine control device that includes an engine body and a purge processing unit that supplies a purge gas containing evaporated fuel from a fuel tank to an intake system of the engine body. The engine control device supplies an air-fuel ratio control unit that feedback-controls an amount of fuel supplied to the engine body using a feedback correction value calculated based on an air-fuel ratio, and supplies the intake system from the purge processing unit. A concentration estimation unit that estimates a purge concentration that is a fuel concentration in the purge gas, wherein the air-fuel ratio control unit performs air-fuel ratio learning that calculates a learning value of the fuel amount based on the feedback correction value, After the air-fuel ratio learning, the fuel amount is feedback controlled using the learned value and the feedback correction value, and the concentration estimation unit is based on the deviation of the feedback correction value before and after the purge gas is supplied by the purge processing unit. After the first concentration estimation for estimating the purge concentration and the air-fuel ratio control unit performing the air-fuel ratio learning, the purge processing unit is Purge gas is supplied, the purge concentration by selectively using the second density estimating for estimating executed based on the deviation between the feedback correction value after the supply of the initial value and a purge gas of the feedback correction value.

Then, when the air-fuel ratio learning is executed immediately before, the concentration estimating unit substitutes the air-fuel ratio learning executed immediately before as the air-fuel ratio learning of the second concentration estimation. On the other hand, when the concentration estimation is performed and the air-fuel ratio learning is not performed immediately before, the first concentration estimation and the second concentration estimation are selectively used based on the necessity of supplying the purge gas to the intake system. The first concentration estimation is executed when the purge gas supply necessity is high, and the second concentration estimation is executed when the purge gas supply necessity is low.

  According to this configuration, the fuel amount is feedback-corrected using the feedback correction value. The feedback correction value is calculated so as to reduce the variation of the air-fuel ratio during engine operation, but also includes components for correcting the constant fuel amount deviation such as the temperature characteristics of the fuel injection valve and aging deterioration. It is. These constant deviation amounts are calculated as fuel amount learning values by air-fuel ratio learning. After learning the air-fuel ratio, the feedback correction value does not include a component for correcting the constant deviation amount until the above-described constant deviation amount occurs again. Only the components that reduce the variation in the above are included.

  In the first concentration estimation, the purge concentration is estimated based on the deviation between the feedback correction value before purging and the feedback correction value after purging. For this reason, even if the feedback correction value includes a component for correcting the constant shift amount, the purge concentration can be accurately estimated by canceling the component. That is, the first concentration estimation has the advantage that the purge concentration estimation is completed earlier by that amount because it is not necessary to perform air-fuel ratio learning when estimating the purge concentration.

  In the second concentration estimation, the purge concentration is estimated on the basis of the deviation between the initial value of the feedback correction value and the feedback correction value after supply of the purge gas after the air-fuel ratio learning is executed. The purge concentration can be estimated with higher accuracy. Specifically, the feedback correction value includes a component that reduces variation in the air-fuel ratio during engine operation, and also includes a component that reduces variation in the air-fuel ratio due to causes other than the purge gas. The first concentration estimation uses two feedback correction values, that is, a feedback correction value before the purge gas supply and a feedback correction value after the purge gas supply, whereas the second concentration estimation is one of the feedback correction values after the purge gas supply. Use only. Therefore, in the second concentration estimation, the influence of the fluctuation of the feedback correction value for reducing the variation in the air-fuel ratio due to causes other than the purge gas is smaller than in the first concentration estimation, and the purge concentration is estimated with a corresponding amount with high accuracy. be able to.

As described above, the first concentration estimation is advantageous in terms of quickness of concentration estimation, and the second concentration estimation is advantageous in terms of accuracy of concentration estimation. By properly using the first concentration estimation and the second concentration estimation according to the situation, priority can be given to the speed of concentration estimation, or priority can be given to accuracy of concentration estimation .

Further , according to the above-described configuration, the first concentration estimation is performed when the necessity for supplying the purge gas is high. As a result, the time required for concentration estimation is shortened, and an opportunity to supply purge gas is secured. On the other hand, the second concentration estimation is executed when the necessity of supplying the purge gas is low. Thereby, the estimation accuracy of the purge concentration can be improved .

Further , according to the above configuration, the first concentration estimation and the second concentration estimation are selectively used in consideration of not only the necessity of supplying the purge gas but also whether or not the air-fuel ratio learning is executed immediately before. When the air-fuel ratio learning is executed immediately before, the component for correcting the constant deviation amount is excluded from the feedback correction value. In such a case, the second concentration estimation is executed by substituting the original air-fuel ratio learning of the second concentration estimation with the immediately preceding air-fuel ratio learning. Thereby, time can be shortened and 2nd density | concentration estimation can be performed. That is, it is possible to improve the accuracy of concentration estimation while ensuring the speed of concentration estimation.

  On the other hand, when the air-fuel ratio learning has not been executed immediately before, the first concentration estimation and the second concentration estimation are selectively used based on the necessity level of the purge gas supply. This usage is as described above.

  Further, the concentration estimation unit may determine a necessary degree of supply of the purge gas to the intake system based on an external atmospheric pressure.

  In general, the ease of volatilization of the fuel varies depending on the external atmospheric pressure. For example, in an environment where the external air pressure is low, such as in a highland, fuel is more volatile than in a lowland.

  According to this configuration, the concentration estimation unit accurately determines the necessity level of the purge gas supply to the intake system by determining the necessity level of the purge gas supply to the intake system based on the external atmospheric pressure. Can do. As a result, switching between the first concentration estimation and the second concentration estimation can be performed at a more appropriate timing.

  The concentration estimation unit may determine that the necessity of supplying purge gas to the intake system is high when the engine is restarted after warm operation, and execute the first concentration estimation. .

  After the warm operation of the engine, the temperature of the engine body is high and the temperature of the fuel tank tends to be high. In other words, it is an environment in which fuel is likely to volatilize. Therefore, there is a possibility that the evaporated fuel is increased at the restart after the warm operation.

  According to the above configuration, the first concentration estimation is executed when the engine is restarted after the warm operation. Therefore, it is possible to accurately determine the situation where the necessity of supplying the purge gas to the intake system is high, and to perform the concentration estimation time. The purge gas supply opportunity can be secured.

Another technique disclosed herein is directed to an engine control device having an engine body and a purge processing unit that supplies a purge gas containing evaporated fuel from a fuel tank to an intake system of the engine body. The engine control device supplies an air-fuel ratio control unit that feedback-controls an amount of fuel supplied to the engine body using a feedback correction value calculated based on an air-fuel ratio, and supplies the intake system from the purge processing unit. A concentration estimation unit that estimates a purge concentration that is a fuel concentration in the purge gas, wherein the air-fuel ratio control unit performs air-fuel ratio learning that calculates a learning value of the fuel amount based on the feedback correction value, After the air-fuel ratio learning, the fuel amount is feedback controlled using the learned value and the feedback correction value, and the concentration estimation unit is based on the deviation of the feedback correction value before and after the purge gas is supplied by the purge processing unit. After the first concentration estimation for estimating the purge concentration and the air-fuel ratio control unit performing the air-fuel ratio learning, the purge processing unit is Purge gas is supplied, the purge concentration by selectively using the second density estimating for estimating executed based on the deviation between the feedback correction value after the supply of the initial value and a purge gas of the feedback correction value.

The concentration estimation unit uses the first concentration estimation and the second concentration estimation separately based on the necessity of supplying the purge gas to the intake system, and the first estimation when the necessity of supplying the purge gas is high. Concentration estimation is performed, and the second concentration estimation is performed when the purge gas supply necessity level is low, and the concentration estimation unit determines the purge gas supply necessity level to the intake system based on the external air pressure. .

As described above, the first concentration estimation is advantageous in terms of quickness of concentration estimation, and the second concentration estimation is advantageous in terms of accuracy of concentration estimation. By properly using the first concentration estimation and the second concentration estimation according to the situation, priority can be given to the speed of concentration estimation, or priority can be given to accuracy of concentration estimation.

Further, according to the above-described configuration, the first concentration estimation is performed when the necessity for supplying the purge gas is high. As a result, the time required for concentration estimation is shortened, and an opportunity to supply purge gas is secured. On the other hand, the second concentration estimation is executed when the necessity of supplying the purge gas is low. Thereby, the estimation accuracy of the purge concentration can be improved.

In addition, as described above, in general, the ease of volatilization of the fuel varies depending on the external atmospheric pressure. For example, in an environment where the external air pressure is low, such as in a highland, fuel is more volatile than in a lowland.

According to this configuration, the concentration estimation unit accurately determines the necessity level of the purge gas supply to the intake system by determining the necessity level of the purge gas supply to the intake system based on the external atmospheric pressure. Can do. As a result, switching between the first concentration estimation and the second concentration estimation can be performed at a more appropriate timing.

  According to the engine control device, it is possible to improve the estimation accuracy of the purge concentration and secure the supply opportunity of the purge gas.

FIG. 1 is a schematic configuration diagram of an engine with a turbocharger. FIG. 2 is a functional configuration diagram of the ECU. FIG. 3 is a flowchart showing the concentration estimation method.

  Hereinafter, exemplary embodiments will be described in detail with reference to the drawings.

<Engine configuration>
FIG. 1 is a schematic configuration diagram of an engine 100 including a turbocharged engine.

  As shown in FIG. 1, the engine 100 is mainly supplied from an intake passage 10 through which intake air (air) introduced from the outside passes, intake air supplied from the intake passage 10, and a fuel injection valve 23 described later. An engine body 20 (for example, a gasoline engine) that generates a vehicle power by burning an air-fuel mixture with exhausted fuel, an exhaust passage 30 that exhausts exhaust gas generated by combustion in the engine body 20, and the energy of the exhaust Then, a turbocharger 40 that supercharges intake air, a fuel tank 50, a purge system 60 that supplies evaporated fuel generated in the fuel tank 50 to the intake passage 10, and an ECU (Electronic Control) that controls the entire engine 100 Unit) 70.

  In the intake passage 10, in order from the upstream side, an air cleaner 11 that purifies intake air introduced from the outside, a compressor 41 of a turbocharger 40 that boosts the intake air that passes through, and an intercooler 12 that cools the intake air that passes through. And a throttle valve 13 for adjusting the amount of intake air passing therethrough, and a surge tank 14 for temporarily storing intake air supplied to the engine body 20.

  The engine body 20 mainly includes an intake valve 22 that introduces intake air supplied from the intake passage 10 into the combustion chamber 21, a fuel injection valve 23 that injects fuel toward the combustion chamber 21, and a combustion chamber 21. A spark plug 24 for igniting an air-fuel mixture supplied with intake air and fuel; a piston 27 that reciprocates by combustion of the air-fuel mixture in the combustion chamber 21; a crankshaft 28 that is rotated by reciprocation of the piston 27; An exhaust valve 29 that exhausts exhaust gas generated by combustion of the air-fuel mixture in the combustion chamber 21 to the exhaust passage 30 is provided.

  The exhaust passage 30 is rotated by exhaust gas passing through in order from the upstream side, and the turbine 42 of the turbocharger 40 that rotates the compressor 41 by this rotation, and, for example, a NOx catalyst, a three-way catalyst, an oxidation catalyst, and the like. An exhaust purification catalyst 31 having an exhaust purification function is provided.

  The exhaust passage 30 is provided with a turbine bypass passage 32 that bypasses the turbine 42 of the turbocharger 40 for exhaust. The turbine bypass passage 32 is provided with a waste gate valve 33 that controls the flow rate of the exhaust gas flowing through the turbine bypass passage 32.

  The purge system 60 adsorbs and stores the evaporated fuel generated in the fuel tank 50, connects the canister 61 and the intake passage 10, and purges the purge gas containing the evaporated fuel from the canister 61 to the intake passage 10. A passage 62 and a purge valve 66 provided in the purge passage 62 are provided. The purge system 60 supplies a purge gas containing evaporated fuel and air to the intake passage 10. Supplying the purge gas to the intake passage 10 is simply referred to as “purge”. The purge system 60 is an example of a purge processing unit.

  The canister 61 contains activated carbon that removably adsorbs fuel vapor. Connected to the canister 61 are a fuel vapor pipe 61 a for introducing fuel vapor in the fuel tank 50, an air release pipe 61 b for opening the canister 61 to the atmosphere, and a purge passage 62. Although not shown, the atmosphere release pipe 61b is provided with an air filter that filters air flowing into the canister 61 and a valve that opens and closes the atmosphere release pipe 61b. The valve is opened when the evaporated fuel is purged.

  The upstream portion of the purge passage 62 is formed by a single passage and is connected to the canister 61. On the other hand, the downstream portion of the purge passage 62 branches into two passages and is connected to two portions of the intake passage 10.

  Specifically, the purge passage 62 includes a common passage 63 on the upstream side, and a first branch passage 64 and a second branch passage 65 on the downstream side. The upstream end of the common passage 63 is connected to the canister 61. The upstream end of the first branch passage 64 and the upstream end of the second branch passage 65 are connected to the downstream end of the common passage 63. The downstream end of the first branch passage 64 is connected to the surge tank 14 of the intake passage 10. A downstream end of the second branch passage 65 is connected to a portion of the intake passage 10 on the upstream side of the compressor 41 via an ejector 67 described later.

  A purge valve 66 is provided in the common passage 63. The purge valve 66 is an electronically controlled valve that is opened and closed by a control signal from the ECU 70. The first branch passage 64 is provided with a check valve 64 a that prevents a reverse flow of intake air from the intake passage 10. The second branch passage 65 is provided with a check valve 65a that prevents the backflow of the intake air from the intake passage 10.

  The ejector 67 connects the main body 67a, the introduction nozzle 67b that connects the portion of the intake passage 10 downstream of the compressor 41 and the main body 67a, and the portion of the intake passage 10 upstream of the compressor 41 and the main body 67a. And a discharge path 67c. The first branch passage 64 is connected to the main body 67 a and constitutes a part of the ejector 67. The tip of the introduction nozzle 67b is tapered, and the intake air recirculated through the introduction nozzle 67b is depressurized at the tip, and negative pressure is generated around the tip of the introduction nozzle 67b. Due to this negative pressure, the purge gas is sucked into the main body 67a from the first branch passage 64. The sucked purge gas is introduced to the upstream side of the compressor 41 in the intake passage 10 through the discharge passage 67c together with the intake air recirculated from the introduction nozzle 67b.

  When the turbocharger 40 is not supercharging intake air (hereinafter referred to as “non-supercharging”), the purge gas is introduced into the intake passage 10 via the second branch passage 65. Specifically, at the time of non-supercharging, since the pressure on the upstream side of the compressor 41 in the intake passage 10 is higher than the pressure on the downstream side of the compressor 41, the recirculation of the intake air through the ejector 67 does not occur. Therefore, the pressure at the downstream end of the first branch passage 64 becomes the pressure of the portion of the intake passage 10 to which the ejector 67 is connected, and the pressure is substantially equal to the atmospheric pressure. Since the canister 61 is open to atmospheric pressure, the differential pressure between the upstream end and the downstream end of the first branch passage 64 is substantially zero, and the purge gas does not flow through the first branch passage 64.

  On the other hand, the surge tank 14 to which the downstream end of the second branch passage 65 is connected has a negative pressure. Therefore, the purge gas flowing through the purge passage 62 is introduced into the surge tank 14 via the second branch passage 65.

  When the turbocharger 40 is supercharging intake air (hereinafter referred to as “supercharging”), purge gas is introduced into the intake passage 10 via the first branch passage 64. Specifically, at the time of supercharging, the surge tank 14 becomes positive pressure due to supercharging. As described above, since the canister 61 is open to the atmospheric pressure, the pressure at the downstream end of the second branch passage 65 is higher than the pressure at the upstream end of the second branch passage 65. Therefore, the purge gas does not flow through the second branch passage 65. In addition, since the check valve 65a is provided in the second branch passage 65, the intake air in the intake passage 10 does not enter the second branch passage 65 in the reverse direction.

  On the other hand, due to supercharging by the compressor 41, the pressure on the downstream side of the compressor 41 in the intake passage 10 is higher than the pressure on the upstream side of the compressor 41, so that the intake air recirculates via the ejector 67. As a result, the purge gas is sucked from the first branch passage 64, and the sucked purge gas is introduced to the upstream side of the compressor 41 in the intake passage 10. Thus, the purge gas flowing through the purge passage 62 is introduced into the intake passage 10 via the first branch passage 64.

  Further, during a transition such as immediately after the start of supercharging or immediately after the supercharging is stopped, the purge gas is sucked from the first branch passage 64 by the ejector 67 and the surge tank 14 is discharged from the second branch passage 65 by the negative pressure of the surge tank 14. A purge gas may be introduced into the. That is, the purge gas can be supplied to the intake passage 10 through both the first branch passage 64 and the second branch passage 65.

  The purge flow rate, which is the flow rate of the purge gas flowing through the purge passage 62, is adjusted by the purge valve 66 regardless of whether it is supercharged, non-supercharged, or transient.

Further, the engine 100 shown in FIG. 1 is provided with various sensors. Specifically, an airflow sensor 81 for detecting the amount of intake air and a temperature sensor 82 for detecting the intake air temperature are provided in a portion of the intake passage 10 between the air cleaner 11 and the compressor 41. A first pressure sensor 83 that detects the supercharging pressure is provided in a portion of the intake passage 10 between the compressor 41 and the throttle valve 13. A second pressure sensor 84 that detects intake manifold pressure is provided in a portion of the intake passage 10 on the downstream side of the throttle valve 13 (specifically, in the surge tank 14). An O ₂ sensor 85 that detects the oxygen concentration in the exhaust gas is provided in a portion of the exhaust passage 30 between the turbine 42 and the exhaust purification catalyst 31.

  The engine body 20 is provided with a crank angle sensor 86 that detects the crank angle of the crankshaft 28 and a water temperature sensor 87 that detects the temperature of the cooling water of the engine body 20.

The airflow sensor 81 outputs the detected intake air amount to the ECU 70. The temperature sensor 82 outputs the detected intake air temperature to the ECU 70. The first pressure sensor 83 outputs a detection signal corresponding to the detected supercharging pressure to the ECU 70. The second pressure sensor 84 outputs a detection signal corresponding to the detected intake manifold pressure to the ECU 70. The O ₂ sensor 85 outputs a detection signal corresponding to the detected oxygen concentration to the ECU 70. The crank angle sensor 86 outputs the detected crank angle to the ECU 70. The water temperature sensor 87 outputs the detected water temperature to the ECU 70. Further, the engine 100 is provided with an atmospheric pressure sensor 80 for detecting atmospheric pressure, and the atmospheric pressure sensor 80 outputs a detection signal corresponding to the detected atmospheric pressure to the ECU 70.

  The ECU 70 includes a CPU, a ROM for storing various programs (including a basic control program such as an OS and an application program that is activated on the OS to realize a specific function), and various data. It is comprised by the computer provided with internal memory like RAM. The ECU 70 performs various controls and processes based on the detection signals supplied from the various sensors described above. The ECU 70 is an example of a control device.

  For example, the ECU 70 performs air-fuel ratio control for feedback control of the fuel injection amount (also referred to as “fuel amount”) from the fuel injection valve 23 so as to realize a desired air-fuel ratio, and concentration estimation control for estimating the purge concentration. Run.

  The ECU 70 includes an air-fuel ratio control unit 71 that feedback-controls the fuel injection amount based on the air-fuel ratio, a purge control unit 72 that controls the supply of purge gas to the intake passage 10, and a concentration estimation unit 73 that estimates the purge concentration. Have. The purge concentration estimated by the concentration estimation unit 73 is used for opening control of the purge valve 66 and air-fuel ratio control by an air-fuel ratio control unit 71 described later.

  The air-fuel ratio control unit 71 executes air-fuel ratio feedback control that feedback-controls the amount of fuel injected from the fuel injection valve 23 based on the air-fuel ratio. The air-fuel ratio control unit 71 executes air-fuel ratio feedback control when a predetermined feedback control condition is satisfied. Examples of the feedback control conditions include (i) not when the engine 100 is started, (ii) not cutting fuel, (iii) the engine water temperature is equal to or higher than a predetermined temperature, and the like. In these cases, the fuel amount is increased or decreased (including 0), so that it is not suitable for air-fuel ratio feedback control.

Specifically, the air-fuel ratio control unit 71 controls the amount of fuel based on the oxygen concentration in the exhaust gas detected by the O ₂ sensor 85 so that the air-fuel ratio becomes a desired value. The air-fuel ratio control unit 71 calculates the fuel amount Q based on the following formula (1) in the air-fuel ratio feedback control.
Q = Q0 × Qfb × Qg (1)
Here, Q0 is a basic fuel amount, Qfb is a feedback correction value, and Qg is an air-fuel ratio learning value.

  The basic fuel amount Q0 is a basic value of the fuel amount. The air-fuel ratio control unit 71 sets the basic fuel amount Q0 based on the intake air amount detected by the airflow sensor 81 or the rotational speed of the engine body 20 and the required load so that the target air-fuel ratio can be realized. A map defining the basic fuel amount QO is stored in the memory. At this time, the air-fuel ratio control unit 71 sets the basic fuel amount Q0 in consideration of air and evaporated fuel contained in the purge gas supplied to the intake passage 10.

  The feedback correction value Qfb is a value for correcting the basic fuel amount Q0 based on the air-fuel ratio. For example, the initial value of the feedback correction value Qfb is 1. The feedback correction value Qfb is increased or decreased from the initial value based on the deviation between the target air-fuel ratio and the actual air-fuel ratio.

The air-fuel ratio learning value Qg is a value set as a learning value in order to reflect the deviation amount constantly included in the feedback correction amount Qfb in the basic fuel amount Q0. Specifically, even if the air-fuel ratio control unit 71 outputs a command signal corresponding to the basic fuel amount Q0 and causes the fuel injection valve 23 to inject fuel, the actual air-fuel ratio is caused by the temperature characteristics of the fuel injection valve 23 and aging deterioration. May deviate from the target air-fuel ratio. In such a case, the feedback correction amount Qfb constantly includes a component that corrects a deviation due to temperature characteristics or aging. Therefore, when a predetermined learning condition is satisfied, the air-fuel ratio control unit 71 acquires an average value of the feedback correction amount Qfb in a predetermined period as the air-fuel ratio learning value Qg (hereinafter, this process is referred to as “air-fuel ratio learning”).

For example, the learning conditions are (i) the air-fuel ratio feedback control is being executed, (ii) the engine water temperature is equal to or higher than a predetermined temperature, (iii) the fuel amount increase correction for high load operation is not performed, (Iv) Load fluctuation is stable (below a predetermined range), (v) The exhaust purification catalyst 31 is not being monitored, (vi) The O ₂ sensor 85 is not being monitored, (vii) The purge gas supply is stopped (Viii) a predetermined period has elapsed since the load fluctuation of the power steering device, electric load, air conditioner, etc. (ix) a predetermined period has elapsed since the fuel cut at deceleration, (x) predetermined The period has arrived. (I) is a precondition for executing the air-fuel ratio learning. (Ii) is because when the engine water temperature is low, the fuel amount may be increased, and in that case, the air-fuel ratio also deviates from an appropriate value. (Iii) is the same reason as (ii). (Iv) is because the amount of oxygen reaching the O ₂ sensor 85 is uneven at the time of transition during load fluctuation. (V) During the monitoring operation of the exhaust purification catalyst 31, in order to check the performance of the exhaust purification catalyst 31, the fuel cut is executed or the fuel injection is restarted, and the air-fuel ratio and O ₂ sensor 85 This is because the detected value is not stable. (Vi) is monitored during the operation of the O ₂ sensor 85, or the amount of fuel rich, or by the lean, the detection value of the air-fuel ratio and the O ₂ sensor 85 is because it is not stable. (Vii) This is because the purge gas becomes a disturbance for the air-fuel ratio feedback control. (Viii) is because the operating state of the engine is not stable when the load of the auxiliary machine fluctuates. (Ix) is because when the fuel is cut, the cylinder is filled with oxygen, and it takes time until the oxygen concentration in the exhaust gas reaches an appropriate value. (X) is a condition for periodically executing the air-fuel ratio learning. That is, when the conditions (i) to (ix) are satisfied, the air-fuel ratio and the detected value of the O ₂ sensor 85 are stable, and the highly accurate air-fuel ratio learning value Qg can be acquired. Further, by satisfying the condition (x), the air-fuel ratio learning can be executed periodically, and the air-fuel ratio learned value Qg can be updated to the latest value as needed.

  The purge control unit 72 controls the purge flow rate, which is the flow rate of the purge gas supplied to the intake passage 10, by adjusting the purge valve 66. For example, the purge control unit 72 sets the target opening of the purge valve 66 according to the target purge flow rate, and adjusts the opening of the purge valve 66 to the target opening. The target purge flow rate is set according to the intake air amount. Specifically, the target purge flow rate is set in proportion to the intake air amount. At the time of supercharging (when the purge gas is supplied via the first branch passage 64), the purge controller 72 determines the pressure before and after the introduction nozzle 67b determined by the pressure detected by the first pressure sensor 83 and the atmospheric pressure sensor 80. Then, the negative pressure generated around the tip of the introduction nozzle 67b is estimated, and the target opening is set based on the estimated negative pressure, the pressure upstream of the purge valve 66 (detected pressure of the atmospheric pressure sensor 80), and the target purge flow rate. Further, at the time of non-supercharging (when the purge gas is supplied via the second branch passage 65), the purge control unit 72 detects the intake manifold pressure (detected pressure of the second pressure sensor 84) and the pressure upstream of the purge valve 66 (high pressure). The target opening is set based on the detected pressure of the atmospheric pressure sensor 80) and the target purge flow rate.

  The purge controller 72 stops the supply of purge gas to the intake passage 10 when the fuel is cut or idling is stopped.

  The concentration estimation unit 73 estimates the purge concentration based on the feedback correction value Qfb. The concentration estimation unit 73 executes the first concentration estimation and the second concentration estimation separately. In the first concentration estimation, the concentration estimating unit 73 estimates the purge concentration based on the deviation of the feedback correction value Qfb before and after the supply of the purge gas. In the second concentration estimation, the concentration estimating unit 73 supplies the purge gas after learning the air-fuel ratio, and estimates the purge concentration based on the feedback correction value Qfb after the supply of the purge gas.

  The concentration estimation unit 73 estimates the purge concentration based on the fluctuation amount of the feedback correction value Qfb caused by supplying the purge gas in both the first concentration estimation and the second concentration estimation. When the purge gas is supplied to the intake passage 10, the air-fuel ratio varies depending on the air and the evaporated fuel in the purge gas. When the air-fuel ratio fluctuates, the feedback correction value Qfb changes accordingly, and the fuel amount Q is feedback-corrected so that the actual air-fuel ratio matches the target air-fuel ratio. That is, the fluctuation amount of the feedback correction value Qfb when the purge gas is supplied reflects the amount of purge gas supplied to the intake passage 10 (hereinafter referred to as “purge amount”). The concentration estimation unit 73 estimates the purge concentration based on the fluctuation amount of the feedback correction value Qfb at this time.

  In the first concentration estimation, the purge concentration is estimated based on the deviation between the feedback correction value Qfb before the purge and the feedback correction value Qfb after the purge, so that it should be reflected in the feedback correction value Qfb as the air-fuel ratio learning value Qg. Even if a component for correcting a constant deviation of the air-fuel ratio is included, the purge concentration can be estimated by canceling the component. That is, the first concentration estimation has the advantage that the purge concentration estimation is completed earlier by that amount because it is not necessary to perform air-fuel ratio learning when estimating the purge concentration.

  On the other hand, in the second concentration estimation, the purge concentration is estimated based on the deviation between the initial value of the feedback correction value Qfb and the feedback correction value Qfb after purging after executing the air-fuel ratio learning. In comparison, the purge concentration can be estimated more accurately. Specifically, since the feedback correction value Qfb is originally a value for suppressing deviation of the actual air-fuel ratio from the target air-fuel ratio, it is not only a value for suppressing fluctuation of the air-fuel ratio due to purge, but also a normal engine The value for suppressing the fluctuation | variation of the air fuel ratio in a driving | operation can also be included. The first concentration estimation uses two feedback correction values Qfb, that is, a feedback correction value Qfb before purging and a feedback correction value Qfb after purging, whereas the second concentration estimation is 1 of the feedback correction value Qfb after purging. Use only one. For this reason, in the second concentration estimation, the influence of fluctuations in the feedback correction value Qfb for suppressing fluctuations in the air-fuel ratio in normal engine operation is smaller than in the first concentration estimation, and the purge concentration is estimated with that much accuracy. can do. However, in the second enrichment estimation, since it is necessary to perform air-fuel ratio learning when estimating the purge concentration, the purge concentration estimation is prolonged by that amount.

  Therefore, the concentration estimation unit 73 executes the first concentration estimation when priority is given to the quickness of concentration estimation, and executes the second concentration estimation when priority is given to the accuracy of concentration estimation. Hereinafter, the concentration estimation method will be described in detail with reference to the flowchart of FIG.

  First, in step S1, the concentration estimation unit 73 determines whether there is a concentration estimation request. The concentration estimation request is a command output from the air-fuel ratio control unit 71, the purge control unit 72, or the like when it is necessary to execute purge concentration estimation. For example, the concentration estimation request is output when (i) the engine is started, (ii) when the periodic estimation timing arrives, (iii) when the purge starts, or the like. (I) is because the amount of evaporated fuel can change while the engine is stopped. (Ii) is for updating the purge concentration which can change with time as needed. (Iii) is because there is a possibility that the evaporated fuel increases while the purge is stopped. In this manner, a concentration estimation request is output when the purge concentration can change or when it is desired to acquire an accurate purge concentration.

  The density estimation unit 73 proceeds to step S2 when there is a density estimation request, but repeats step S1 when there is no density estimation request, and waits to accept the density estimation request.

Next, in step S2, the concentration estimation unit 73 determines whether or not air-fuel ratio learning has been executed within the most recent predetermined time. The most recent predetermined time is set to a time that can be estimated that the learned air-fuel ratio learned value Q1 has not changed substantially. That is, in step S2, it is determined whether air-fuel ratio learning has been executed immediately before. The concentration estimating unit 73 proceeds to step S5 when the air-fuel ratio learning has been performed, and proceeds to step S3 when the air-fuel ratio learning has not been performed.

  In step S3, the concentration estimation unit 73 determines whether there is a purge priority request. The purge priority request is a command that is output when the amount of evaporated fuel in the canister 61 is likely to increase or may increase. For example, the concentration estimation unit 73 (i) the atmospheric pressure is lower than a predetermined reference pressure, (ii) the current intake air temperature is higher than the predetermined reference temperature, (iii) at the time of restart after warm operation When any of the conditions is satisfied, it is determined that there is a purge priority request. Since the fuel is likely to volatilize when the atmospheric pressure decreases, the condition (i) is set. The atmospheric pressure is detected by the atmospheric pressure sensor 80. Regarding (ii), the intake air temperature is a temperature related to the temperature in the fuel tank 50. That is, a high intake air temperature means that the environmental temperature is high and that the temperature in the fuel tank 50 is also high. Therefore, the temperature in the fuel tank 50 is indirectly determined based on the intake air temperature to determine whether or not the fuel is likely to volatilize. The intake air temperature is detected by the temperature sensor 82. The condition (iii) also relates to the temperature in the fuel tank 50. After the warm operation, the temperature of the engine body 20 is high, and similarly, the temperature in the fuel tank 50 tends to be high. While the engine body 20 is stopped, the supply of purge gas to the intake passage 10 is also stopped, so that the evaporated fuel increases. Therefore, when restarting after the warm operation, it is determined that there is a high possibility that the evaporated fuel is increasing, and it is determined that there is a purge priority request. The water temperature of the engine body 20 is detected by a water temperature sensor 87.

The concentration estimating unit 73 proceeds to step S9 when there is a purge priority request, and proceeds to step S4 when there is no purge priority request.

  In step S4, the concentration estimation unit 73 executes the second concentration estimation. Specifically, in step S4, the concentration estimation unit 73 causes the air-fuel ratio control unit 71 to perform air-fuel ratio learning. During the air-fuel ratio learning, the purge by the purge control unit 72 is stopped as described above. When the air-fuel ratio learning is completed, the concentration estimation unit 73 causes the purge control unit 72 to perform a purge in step S5. Thereafter, the concentration estimation unit 73 reads the feedback correction value Qfb after purging (step S6), calculates the deviation between the initial value of the feedback correction value Qfb and the feedback correction value Qfb after purging (step S7), and the deviation Based on the above, the purge concentration is estimated (step S8).

  On the other hand, in step S9, the concentration estimation unit 73 executes the first concentration estimation. Specifically, in step S9, the concentration estimation unit 73 temporarily stops the purge by the purge control unit 72 and reads the feedback correction value Qfb before the purge. Thereafter, the concentration estimation unit 73 causes the purge control unit 72 to perform a purge (step S10), and the concentration estimation unit 73 reads the feedback correction value Qfb after the purge (step S11). Then, the concentration estimation unit 73 calculates a deviation between the feedback correction value Qfb before purging and the feedback correction value Qfb after purging (step S12), and estimates the purge concentration based on the deviation (step S13).

  In this way, the concentration estimation unit 73 uses the first concentration estimation and the second concentration estimation properly depending on whether or not there is a purge priority request. When there is a purge priority request, the concentration estimation unit 73 performs the first concentration estimation giving priority to the quickness of the concentration estimation. By shortening the time required for estimating the concentration of the purge gas, it is possible to secure the time for performing the purge. Thereby, more purge gas can be supplied to the intake passage 10. On the other hand, when there is no purge priority request, the concentration estimation unit 73 prioritizes the accuracy of concentration estimation and executes the second concentration estimation. In the second concentration estimation, it takes time to estimate the concentration as much as the air-fuel ratio learning is executed. However, in a situation where there is no purge priority request, there is no problem even if the purge is stopped for a while. Therefore, in the second concentration estimation, the accuracy of concentration estimation is improved by executing air-fuel ratio learning.

  In addition, the concentration estimation unit 73 also uses a determination as to whether or not air-fuel ratio learning has been executed immediately before the first concentration estimation and the second concentration estimation. That is, when the air-fuel ratio learning is executed immediately before, the second concentration estimation is executed, while when the air-fuel ratio learning is not executed immediately before, the second concentration estimation is executed if there is no purge priority request. If there is a purge priority request, the first concentration estimation is executed. However, in the second concentration estimation that is executed when the air-fuel ratio learning is executed immediately before, the air-fuel ratio learning that is originally performed as part of the second concentration estimation is replaced with the immediately preceding air-fuel ratio learning.

  That is, when the air-fuel ratio learning is executed immediately before, the second concentration estimation can be executed by substituting the air-fuel ratio learning, so that it is not necessary to perform the air-fuel ratio learning again. That is, it is possible to improve the accuracy of concentration estimation while ensuring the speed of concentration estimation. Therefore, when the air-fuel ratio learning is executed immediately before, the second concentration estimation is executed regardless of the presence or absence of the purge priority request. On the other hand, when the air-fuel ratio learning has not been executed immediately before, the first concentration estimation and the second concentration estimation are selectively used based on the presence or absence of the purge priority request. This usage is as described above.

  As described above, the ECU 70 controls the amount of fuel supplied to the engine main body 20 using the feedback correction value Qfb calculated based on the air-fuel ratio, and the air intake fuel passage from the purge system 60. And a concentration estimation unit 73 that estimates a purge concentration that is a fuel concentration in the purge gas supplied to the fuel gas, and the air-fuel ratio control unit 71 calculates an air-fuel ratio learning value Qg of the fuel amount based on the feedback correction value Qfb. The air-fuel ratio learning is executed, and after the air-fuel ratio learning, the fuel amount is feedback-controlled using the air-fuel ratio learned value Qg and the feedback correction value Qfb, and the concentration estimation unit 73 provides a feedback correction value before and after the purge gas is supplied by the purge system 60. First concentration estimation for estimating the purge concentration based on the deviation of Qfb, and air-fuel ratio learning to the air-fuel ratio control unit 71 After the execution, the purge gas is supplied to the purge system 60, and the second concentration estimation that estimates the purge concentration based on the deviation between the initial value of the feedback correction value Qfb and the feedback correction value Qfb after the supply of the purge gas is executed separately. To do.

  According to this configuration, in the first concentration estimation, the purge concentration is estimated based on the deviation between the feedback correction value before purging and the feedback correction value after purging. Therefore, even if the feedback correction value includes a component for correcting the constant deviation amount, the purge concentration can be estimated by canceling the component. At this time, that is, since it is not necessary to perform air-fuel ratio learning when estimating the purge concentration, the first concentration estimation has an advantage that the purge concentration estimation is completed earlier by that much.

  In the second concentration estimation, after performing air-fuel ratio learning, the purge concentration is estimated based on the deviation between the initial value of the feedback correction value and the feedback correction value after the purge gas is supplied. Therefore, in the second concentration estimation, the influence of the fluctuation of the feedback correction value Qfb for reducing the variation in the air-fuel ratio due to causes other than the purge gas is smaller than in the first concentration estimation, and the purge concentration is estimated with a corresponding amount. can do.

  As described above, the first concentration estimation is advantageous in terms of quickness of concentration estimation, and the second concentration estimation is advantageous in terms of accuracy of concentration estimation. By properly using the first concentration estimation and the second concentration estimation according to the situation, priority can be given to the speed of concentration estimation, or priority can be given to accuracy of concentration estimation.

<< Other Embodiments >>
As described above, the embodiment has been described as an example of the technique disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can also be applied to an embodiment in which changes, replacements, additions, omissions, and the like are appropriately performed. Moreover, it is also possible to combine each component demonstrated by the said embodiment and it can also be set as new embodiment. In addition, among the components described in the accompanying drawings and detailed description, not only the components essential for solving the problem, but also the components not essential for solving the problem in order to exemplify the above technique. May also be included. Therefore, it should not be immediately recognized that these non-essential components are essential as those non-essential components are described in the accompanying drawings and detailed description.

  About the said embodiment, it is good also as following structures.

  The configuration of the engine 100 is merely an example and is not limited thereto. For example, the engine 100 includes the turbocharger 40, but may not include the turbocharger 40. The purge system 60 includes a first branch passage 64 and a second branch passage 65, and is configured to be able to supply purge gas to both the upstream side and the downstream side of the turbocharger 40. It is not limited to this. Even if the purge gas is supplied to only one of the upstream side and the downstream side of the turbocharger 40, the concentration estimation in the present disclosure can be applied.

  The calculation of the fuel amount Q is not limited to that based on the formula (1). Any calculation method can be adopted as long as the fuel amount can be corrected using the feedback correction value and the learning value. Further, the feedback correction value is not limited to the case where the initial value is 1. For example, depending on the calculation method of the fuel amount Q, the initial value of the feedback correction value may be zero.

  Further, in the proper use of the first concentration estimation and the second concentration estimation, it is determined whether or not the air-fuel ratio learning is executed immediately before (step S2), but this may be omitted. That is, the first concentration estimation and the second concentration estimation may be selectively used depending on whether or not the purge priority request is present. Further, the proper use of the first concentration estimation and the second concentration estimation may be performed based on not only the purge priority request but also other factors. As described above, the first concentration estimation is excellent in the speed of density estimation, and the second density estimation is excellent in the precision of density estimation. Therefore, depending on the situation, that is, the speed of the density estimation and the precision of the density estimation are improved. The first concentration estimation and the second concentration estimation may be properly used depending on which one is required.

  The purge priority request is merely an example, and conditions other than the restart time after the atmospheric pressure, the intake air temperature, and the warm operation may be used as the purge priority request. For example, a temperature sensor may be provided in or near the fuel tank 50, and it may be determined that there is a purge priority request when the temperature detected by the temperature sensor is equal to or higher than a predetermined temperature.

  In the first concentration estimation, the feedback correction value Qfb before purging is acquired first, and the feedback correction value Qfb after purging is acquired later, but the order may be reversed.

  In addition, as long as the effect by the concentration estimation method according to the present disclosure can be realized, the steps in the flowchart may be omitted, the order may be changed, or additional steps may be added.

  As described above, the technique disclosed herein is useful for an engine control apparatus.

100 Engine System 10 Intake Passage 20 Engine Body 40 Turbocharger 50 Fuel Tank 60 Purge System (Purge Processing Section)
61 Canister 62 Purge passage 66 Purge valve 67 Ejector 70 ECU (control device)
71 Air-fuel ratio control unit 72 Purge control unit 73 Concentration estimation unit

Claims (4)

The engine body,
A control unit for an engine having a purge processing unit for supplying a purge gas containing fuel vapor in a fuel tank to an intake system of the engine body,
An air-fuel ratio controller that feedback-controls the amount of fuel supplied to the engine body using a feedback correction value calculated based on the air-fuel ratio;
A concentration estimating unit that estimates a purge concentration that is a fuel concentration in a purge gas supplied from the purge processing unit to the intake system;
The air-fuel ratio control unit executes air-fuel ratio learning for calculating a fuel amount learning value based on the feedback correction value. After the air-fuel ratio learning, the fuel amount is fed back using the learning value and the feedback correction value. Control
The concentration estimator is
A first concentration estimation for estimating the purge concentration based on a deviation of the feedback correction value before and after supply of purge gas by the purge processing unit;
After causing the air-fuel ratio control unit to execute the air-fuel ratio learning, the purge processing unit is supplied with purge gas, and the purge is performed based on a deviation between an initial value of the feedback correction value and the feedback correction value after supply of the purge gas. Execute separately using the second concentration estimation to estimate the concentration ,
The concentration estimator is
When the air-fuel ratio learning is executed immediately before, the second concentration estimation is executed by substituting the air-fuel ratio learning executed immediately before as the air-fuel ratio learning of the second concentration estimation,
If the air-fuel ratio learning has not been executed immediately before, the first concentration estimation and the second concentration estimation are selectively used based on the necessity of supplying purge gas to the intake system, and the necessity of supplying purge gas is determined. The engine control apparatus is configured to execute the first concentration estimation when the gas concentration is high, and to execute the second concentration estimation when the necessary degree of supply of the purge gas is low . The engine control device according to claim 1 ,
The engine control apparatus according to claim 1, wherein the concentration estimation unit determines a necessary degree of supply of the purge gas to the intake system based on an external air pressure. The engine control device according to claim 1 ,
The engine is characterized in that the concentration estimator determines that the necessity of supplying purge gas to the intake system is high when the engine is restarted after warm operation, and executes the first concentration estimation. Control device. The engine body,
A control unit for an engine having a purge processing unit for supplying a purge gas containing fuel vapor in a fuel tank to an intake system of the engine body,
An air-fuel ratio controller that feedback-controls the amount of fuel supplied to the engine body using a feedback correction value calculated based on the air-fuel ratio;
A concentration estimating unit that estimates a purge concentration that is a fuel concentration in a purge gas supplied from the purge processing unit to the intake system;
The air-fuel ratio control unit executes air-fuel ratio learning for calculating a fuel amount learning value based on the feedback correction value. After the air-fuel ratio learning, the fuel amount is fed back using the learning value and the feedback correction value. Control
The concentration estimator is
A first concentration estimation for estimating the purge concentration based on a deviation of the feedback correction value before and after supply of purge gas by the purge processing unit;
After causing the air-fuel ratio control unit to execute the air-fuel ratio learning, the purge processing unit is supplied with purge gas, and the purge is performed based on a deviation between an initial value of the feedback correction value and the feedback correction value after supply of the purge gas. Execute separately using the second concentration estimation to estimate the concentration ,
The concentration estimating unit selectively uses the first concentration estimation and the second concentration estimation based on the necessity of supplying purge gas to the intake system, and the first concentration estimation when the necessity of supplying purge gas is high. And executing the second concentration estimation when the necessity of supplying the purge gas is low,
The engine control apparatus according to claim 1, wherein the concentration estimation unit determines a necessary degree of supply of the purge gas to the intake system based on an external air pressure .

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