JP4491387B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly, to control for performing a fuel evaporative gas purge process in an internal combustion engine that directly injects fuel into a cylinder.

  An internal combustion engine equipped with an in-cylinder injector for injecting fuel into a combustion chamber of the internal combustion engine is known. In such an internal combustion engine, when the internal combustion engine is at a low load, such as during idling, the fuel is injected into the cylinder during the compression stroke to perform weak stratified combustion, and during a high load, the fuel is injected into the cylinder during the intake stroke. The homogeneous combustion is carried out by injecting the fuel into the fuel cell, thereby achieving both low fuel consumption and high output.

  In general, in vehicles including such an internal combustion engine, the evaporated fuel (vapor) from a fuel tank or the like is temporarily adsorbed to a collecting device such as a canister to operate the internal combustion engine. By purging the fuel evaporative gas adsorbed by a collecting device such as a canister according to the state and introducing it into the intake system of the internal combustion engine, the fuel evaporative gas is prevented from being diffused into the atmosphere.

  Thus, at the time of performing the purge process for purging the fuel evaporative gas and introducing it into the intake system of the internal combustion engine, the purge amount depending on the concentration of the fuel evaporative gas to be purged, so-called purge gas concentration and its flow rate, is the injector. In addition to the amount of fuel injected from the engine, it is introduced into the internal combustion engine. As a result, the air-fuel ratio fluctuates and the combustion deteriorates. Therefore, when performing such a purge process, the fuel injection amount is corrected to reduce the performance of the internal combustion engine or the emission. Is required to avoid.

  By the way, if the in-cylinder injector is given a fuel injection pulse width smaller than this, it becomes impossible to perform fuel injection stably (the fuel injection pulse width at this limit is hereinafter referred to as “minimum pulse width”). .) There is TAUmin. By selecting an in-cylinder injector having a characteristic that the amount of fuel by this TAUmin is smaller than the minimum fuel injection amount when the purge processing device is not in operation (for example, the fuel injection amount during idling), the non-purging device Even when supplying the minimum fuel injection amount during operation, the in-cylinder injector can stably perform fuel injection.

  On the other hand, there is a demand to reduce the size of the canister for the purpose of improving the mountability to the vehicle and reducing the cost. On the other hand, if the canister is small, the vapor generated in the fuel tank cannot be absorbed and released to the atmosphere. (Overflow condition) is a concern. For this reason, it is necessary to provide a canister of a certain size, and all the purge gas from the canister must be burned in the internal combustion engine, so the purge amount tends to increase.

  For this reason, in order to obtain the stoichiometric air-fuel ratio even when the purge amount is increased, the fuel reduction amount from the fuel injection valve becomes large. At this time, the injection amount after the fuel reduction commanded to the fuel injection valve is the minimum pulse. A situation occurs in which the amount of injection is less than the injection amount due to the width TAUmin. In such a situation, the fuel injection from the in-cylinder injector becomes unstable, and if the fuel injection valve cannot accurately supply the injection amount obtained from the theoretical air-fuel ratio due to the instability of the fuel injection, the actual air-fuel ratio becomes There is a problem that the theoretical air-fuel ratio deviates, the conversion efficiency of the three-way catalyst provided in the exhaust passage is lowered, and the exhaust emission is deteriorated.

  Japanese Patent Laying-Open No. 2003-120379 (Patent Document 1) discloses an engine fuel injection control device that enables purge processing even in a region where the fuel injection amount is small. The fuel injection control device of the engine includes a first injection amount calculation means for calculating an injection amount per cycle at which a target air-fuel ratio is obtained as a first injection amount, and the fuel of the first injection amount for each cycle. A fuel injection control device for an engine comprising a fuel injection valve for supplying fuel to a fuel tank, wherein fuel particles in a vapor generated in a fuel tank are adsorbed to the canister and the adsorbed fuel content in the canister is being operated in the engine An evaporative fuel treatment device that converts the purge gas into the intake passage with the suction pressure of the first and second injection amounts subtracted by the purge amount from the first injection amount so that the target air-fuel ratio is obtained even during the introduction of the purge gas. A second injection amount calculation means for calculating the injection amount, and when the second injection amount falls below the minimum injection amount of the fuel injection valve, the fuel for the injection amount for two cycles is Injected into, and a purge time control means for performing control to stop fuel injection in the next cycle. Further, the fuel injection control device of this engine reduces the injection amount for two cycles to the minimum injection amount by 2 when the injection amount for two cycles falls below the minimum injection amount of the fuel injection valve during execution of the purge control means. The fuel is expanded to the doubled value, and the control is performed to inject the fuel of the expanded two cycles of injection at a time in this cycle and stop the fuel injection in the next cycle.

According to the engine fuel injection control device of this engine, fuel of two cycles of injection amount is injected at a time in this cycle, so the margin for the minimum injection amount is doubled. In other words, since the reduction amount of the injection amount from the fuel injection valve in a range where fuel injection can be stably performed increases, the exhaust composition is not affected. In particular, even if the injection amount for two cycles is less than the minimum injection amount of the fuel injection valve due to the increase in the purge amount, the allowance for the minimum injection amount can be doubled, which makes it stable. Therefore, the reduction amount of the injection amount from the fuel injection valve in the range where fuel injection can be performed is expanded, so that the exhaust composition is not affected.
JP 2003-120379 A

  However, when the vehicle is traveling at a high altitude or when a manual transmission is mounted as a transmission of the vehicle, the fuel injection amount from the in-cylinder injector is further reduced as follows. When the vehicle is traveling on a high altitude, the atmospheric pressure is lowered, so that the pumping loss of the internal combustion engine (power loss in intake and exhaust) is reduced and the output of the internal combustion engine is reduced. In the case of a manual transmission, since the mechanical friction is small (as compared to an automatic transmission), control is performed so that the output of the internal combustion engine is reduced.

  When the output of the internal combustion engine decreases, the amount of fuel injection from the in-cylinder injector is controlled to decrease. As a result, a situation in which the injection amount after reducing the purge amount falls below the injection amount based on the minimum pulse width TAUmin can occur even if the technique of Patent Document 1 is used. In such a case, the purge process is temporarily prohibited. When the purge process is prohibited, an injection amount equal to or greater than TAUmin is injected from the in-cylinder injector, and the purge process is permitted. When the purge process is permitted, the original state is restored and the purge process is prohibited again. Hunting occurs by repeatedly executing and canceling such a purge process. The hunting of the purge process becomes a disturbance of stable control of the air-fuel ratio, and causes a rotation fluctuation.

  Further, since the fuel injection amount may be small when the load is high at high altitudes, the purge process is difficult to be permitted if the purge amount itself is large. If the purge process is not permitted, the vapor cannot be purged at all.

  The present invention has been made to solve the above-described problems, and its purpose is to perform purge processing as much as possible even in a situation where the fuel injection amount is low and below the minimum injection amount of the fuel injection means at high altitudes. It is an object of the present invention to provide a control device for an internal combustion engine that can be executed to process vapor.

  A control device according to a first aspect of the invention includes a fuel injection means for injecting fuel into a cylinder, and controls an internal combustion engine that performs a purge process of fuel evaporative gas. The control device is configured to control fuel injection means so as to inject fuel based on conditions required for the internal combustion engine, and to adjust the pressure of fuel supplied to the fuel injection means. Adjusting means. The adjusting means includes means for adjusting the fuel pressure based on the atmospheric pressure.

  According to the first aspect of the invention, when the purge process is executed, the amount of the purge amount is subtracted (decreased) from the fuel amount calculated based on the condition required for the internal combustion engine, and the fuel from the fuel injection means is obtained. An injection amount is calculated. For example, since the fuel injection amount is small at a light load, the fuel injection time is shortened as the pressure of the fuel supplied to the fuel injection means is higher. When the fuel injection time is shortened, a linear characteristic (linearity characteristic) is not established in the relationship between the fuel injection time and the fuel injection amount in the fuel injection means. In such a case, the fuel injection means may inject an amount of fuel that is different from the fuel amount commanded by the control means, and the air-fuel ratio feedback control becomes unstable, so the purge process is prohibited. The For this reason, the adjusting means adjusts so as to lower the pressure of the fuel supplied to the fuel injection means, for example, to lower the discharge pressure of the high-pressure pump. In this way, even if only the purge amount is subtracted from the fuel amount calculated based on the conditions required for the internal combustion engine, it is possible to secure a fuel injection time that can inject fuel normally. In particular, the higher the altitude, the lower the atmospheric pressure and the lower the pumping loss, so that the required fuel amount becomes smaller. For this reason, since possibility that it will be less than minimum injection time becomes high, the pressure of fuel is reduced more largely so that atmospheric pressure is low, and fuel can be normally injected from a combustion injection means. Even during light load operation at such high altitudes, the purge process can be continued and fuel can be injected normally into the cylinder. As a result, there is provided a control device for an internal combustion engine capable of processing vapor by performing purge processing as much as possible even in a situation where the fuel injection amount is low and below the minimum injection amount of the fuel injection means at high altitude. be able to.

  In the control device according to the second invention, in addition to the configuration of the first invention, the adjusting means includes means for reducing the pressure of the fuel. The amount of decrease in the fuel pressure does not fall below the pressure at which the target injection amount can be made larger than the minimum injection amount even if the injection amount is corrected to decrease.

  According to the second invention, the pressure of the fuel supplied to the fuel injection means for directly injecting the fuel into the cylinder is reduced. At this time, even if the injection amount is corrected to decrease, the fuel pressure decrease amount is larger than the minimum injection amount, so the fuel injection time can be made longer and less than the minimum injection time. The fuel can be injected into the tank.

  In the control device according to the third aspect of the invention, in addition to the configuration of the second aspect of the invention, the reduction amount correction is a purge correction.

  According to the third aspect of the present invention, the amount of decrease in the fuel pressure is such that the target injection amount is larger than the minimum injection amount even if the injection amount is corrected to decrease by the purge amount. The fuel can be normally injected without falling below the time, and the purge process does not have to be stopped.

  In addition to the configuration of the third aspect of the invention, the control device according to the fourth aspect of the invention reduces the injection amount to the minimum injection amount by the reduction correction by the purge correction even when the fuel pressure by the adjusting means is reduced. If it is below, it further includes means for reducing the purge amount.

  According to the fourth aspect of the invention, even if the fuel pressure is reduced by the adjusting means, if the injection amount falls below the minimum injection amount due to the reduction correction by the purge correction, normal fuel injection becomes difficult. To a region where the linear relationship between the fuel injection time and the fuel injection amount is not established (a region where the linearity characteristic is not established) and a region where the linear relationship may not be established (a region where the linearity characteristic may not be established) Therefore, the fuel injection time can be lengthened.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<First Embodiment>
FIG. 1 shows an overall configuration diagram of a direct injection engine controlled by a control device according to a first embodiment of the present invention.

  The engine body 10 has a cylinder head 110 covered over the cylinder block 100, and a piston 120 is slidably held in a cylinder 100A formed in the cylinder block 100. The reciprocating motion of the piston 120 in the cylinder 100A is converted into the rotational motion of the crankshaft 130 and transmitted to the transmission 300 or the like. The crankshaft 130 is connected to the starter 30 via the flywheel 140 when the engine is started. A clutch 310 is provided between the flywheel 140 and the transmission 300.

  In the present embodiment, transmission 300 is a manual transmission that is shifted by a driver's manual operation. The clutch 310 is engaged or released by a driver's operation. The transmission may be an automatic transmission. Since the manual transmission has less mechanical loss, it is assumed that the fuel injection amount from the in-cylinder injector 210 is less than the minimum injection amount defined by TAUmin in many cases.

  A combustion chamber 1000 is formed above the piston 120 with the cylinder block 100 and the cylinder head 110 as chamber walls. In the combustion chamber 1000, a mixture of fuel and air is burned, and the piston 120 moves up and down by the explosive force. Move it. The air-fuel mixture is ignited by a spark plug 150 provided through the cylinder head 110 and protruding into the combustion chamber 1000.

  Supply of air constituting the air-fuel mixture is performed by an intake passage 1010 formed in the intake pipe connected to the cylinder head 110 and the cylinder head 110. Further, exhaust from the combustion chamber 1000 is performed by an exhaust passage 1020. The cylinder head 110 is provided with an intake valve 160 for switching communication between the intake passage 1010 and the combustion chamber 1000 and an exhaust valve 170 for switching communication between the exhaust passage 1020 and the combustion chamber 1000. ing.

  A flap-like throttle valve 190 is provided in the intake pipe, and the air flow in the intake passage 1010 is adjusted according to the opening.

  The fuel constituting the mixture is supplied by an electromagnetic in-cylinder injector 210. The in-cylinder injector 210 is provided so as to penetrate the cylinder head 110, and injects fuel from the tip nozzle portion into the combustion chamber 1000 (inside the cylinder). Instead of or in addition to the in-cylinder injector 210, an injector that injects fuel into the intake port or the intake passage 1010 may be provided.

  The fuel supplied to the in-cylinder injector 210 is supplied by boosting the fuel sucked from the fuel tank 250 in two stages by a low pressure pump (feed pump) 240 and a high pressure pump 230. The high-pressure pump 230 is driven by power transmitted from the crankshaft 130 of the engine body 10 via a belt or the like. On the other hand, the low-pressure pump 240 is electrically driven, and the in-cylinder injector 210 is also supplied with fuel from the low-pressure pump 240 during startup.

  Further, an engine control computer (hereinafter referred to as an engine ECU (Electronic Control Unit)) 60 that controls each part of the engine such as the spark plug 150, the throttle valve 190, the in-cylinder injector 210, and the like is provided. The engine ECU 60 has a general configuration including a CPU (Central Processing Unit), a RAM (Random Access Memory), an SRAM (Static Random Access Memory), a ROM (Read Only Memory), and the like. Based on the above, the spark plug 150 is operated, a control signal is output to the throttle valve 190 to adjust the opening degree (throttle opening degree) of the throttle valve 190, and the in-cylinder injector 210 is energized by the control signal and supplied in a predetermined manner. At this timing, the nozzle of the in-cylinder injector 210 is opened for a predetermined time.

  Sensors input to the engine ECU 60 include an air flow meter 510, a crank angle sensor 520, an A / F sensor 530, a throttle opening sensor 540, an accelerator opening sensor 550, a vehicle speed sensor 560, a cooling water temperature sensor, and the like.

  The air flow meter 510 measures the flow rate of air flowing through the intake passage 1010. The crank angle sensor 520 outputs a pulse signal for detecting the engine speed NE, and the A / F sensor 530 measures the air-fuel ratio in the exhaust passage 1020. The throttle opening sensor 540 detects the opening of the throttle valve 190. The accelerator opening sensor 550 detects the opening (depression amount) of the accelerator pedal 420. The vehicle speed sensor 560 outputs a pulse signal for detecting the vehicle speed (wheel rotation). The cooling water temperature sensor detects an engine cooling water temperature that represents the engine temperature. A sensor (not shown) for detecting the atmospheric pressure from the intake air is provided.

  Further, when the driver operates the key at the time of starting, the ignition (IG) on signal and the starter on signal are input to engine ECU 60. When the stroke amount of the clutch pedal 430 becomes maximum, the neutral start switch 570 is turned on, and an on signal is input to the engine ECU 60.

  The engine ECU 60 controls the combustion injection amount based on the intake air amount detected by the air flow meter 510 or the like. At this time, the engine ECU 60 controls the injection amount and the injection timing according to the engine speed and the engine load so as to achieve an optimal combustion state based on signals from the sensors. In the engine main body 10, in order to inject fuel directly into the cylinder, injection timing control and injection amount control are performed simultaneously. Further, the engine ECU 60 performs ignition timing control so as to achieve an optimal ignition timing based on signals (including a knocking sensor and the like) detected by the crank angle sensor 520, the cam position sensor, and the like. Such control realizes both high output and low emission of the engine body 10.

Meanwhile, the canister 1230 is a collecting container for collecting fuel vapor generated in the fuel tank 250 is connected to the fuel tank 250 via the base over path passage 1260, further canister 1230 is collected therein The fuel evaporative gas is taken into the intake passage 101 of the engine body 10.
Connected to a purge passage 1280 for supplying zero. The purge passage 1280 communicates with a purge port 1290 opened downstream of the throttle valve 190 of the intake passage 1010. As is well known, the canister 1230 is filled with an adsorbent (activated carbon) that adsorbs fuel evaporative gas, and an atmospheric passage for introducing the atmosphere into the canister 1230 via a check valve during purging. 1270 is provided. Further, the purge passage 1280 has a purge control valve 1250 (hereinafter referred to as VSV (Vacuum Switching) for controlling the purge amount.
The amount of fuel evaporative gas to be purged in the canister 1230, and thus the engine main body, is controlled by the engine ECU 60 being duty-controlled by the opening degree of the purge control valve 1250. 10 is configured to control the amount of fuel introduced into the fuel tank 10 (hereinafter referred to as a purge amount).

  Further, the engine ECU 60 controls the pressure of fuel supplied to the in-cylinder injector 210 by controlling the high-pressure pump 230. At this time, for example, the high pressure pump 230 is controlled as follows to control the fuel pressure.

  The high-pressure pump 230 includes a pump plunger that reciprocates in the cylinder by the rotation of the cam, and a pressurizing chamber that includes the cylinder and the pump plunger. The pressurizing chamber includes a pump supply pipe that communicates with a feed pump that feeds fuel from the fuel tank, a return pipe that causes the fuel to flow out from the pressurizing chamber and return it to the fuel tank, and in-cylinder injector 210 High-pressure delivery pipes that are pumped toward are connected to each other. The high-pressure pump 230 is provided with an electromagnetic spill valve that opens and closes a pump supply pipe and a high-pressure delivery pipe and a pressurizing chamber.

  When the electromagnetic plunger spill valve is open and the pump plunger moves in the direction of increasing the volume of the pressurizing chamber, that is, when the high-pressure pump 230 is in the suction stroke, fuel is supplied from the pump supply pipe into the pressurizing chamber. Inhaled. Further, when the pump plunger moves in the direction in which the volume of the pressurizing chamber decreases, that is, when the high-pressure pump 230 is in the pumping stroke, if the electromagnetic spill valve is closed, the pump supply pipe, the return pipe, and the pressurizing chamber The gap is cut off, and the fuel in the pressurized chamber is pumped to the in-cylinder injector 210 via the high-pressure delivery pipe.

  In such a high-pressure pump 230, the fuel is pumped toward the in-cylinder injector 210 only during the closing period of the electromagnetic spill valve during the pumping stroke, and therefore, the closing timing of the electromagnetic spill valve is controlled. (By adjusting the closing period of the electromagnetic spill valve), the fuel pumping amount is adjusted. In other words, the fuel pumping amount increases by increasing the closing period by increasing the closing timing of the electromagnetic spill valve, and the fuel pumping amount by shortening the closing period by delaying the closing period of the electromagnetic spill valve. Less. When the fuel pumping amount increases, the fuel pressure in the high-pressure delivery pipe increases. When the fuel pumping amount decreases, the fuel pressure in the high-pressure delivery pipe decreases.

  In this way, the fuel delivered from the feed pump is pressurized by the high-pressure pump 230, and the pressurized fuel is pumped toward the in-cylinder injector 210 at an appropriate fuel pressure, so that the fuel directly into the combustion chamber. Even in an internal combustion engine that injects fuel, the fuel injection can be performed accurately.

  When the fuel pressure is increased by the high-pressure pump 230, the fuel injection time is shortened even for the same required fuel amount, and may be less than the minimum injection time TAUmin at which linearity is lost between the injection time and the injection amount. When the engine load is light, the required fuel amount is small, and if the purge process is being executed, the fuel injection amount from the in-cylinder injector 210 is obtained by subtracting the purge amount. Therefore, the higher the fuel pressure, the lower the minimum injection time TAUmin, and the higher the possibility that the purge process is prohibited. When the purge process is prohibited, the vapor cannot be processed, or the purge process hunts and the air-fuel ratio becomes unstable. For this reason, the engine ECU 60, which is the control device according to the present embodiment, is supplied from the high-pressure pump 230 to the in-cylinder injector 210 when a predetermined condition (light load or the like in which the purge process is easily prohibited) is satisfied. The engine is controlled so as not to prohibit the purge process by reducing the pressure of the fuel to increase the fuel injection time of the in-cylinder injector 210 to be equal to or greater than TAUmin.

  With reference to FIG. 2, a control structure of a program executed by engine ECU 60 which is a control device according to the present embodiment will be described. Note that the program described below is repeatedly executed at a predetermined cycle.

  In step (hereinafter step is abbreviated as S) 100, engine ECU 60 detects engine speed NE. In S110, engine ECU 60 calculates basic target fuel pressure P from engine speed NE.

  In S120, engine ECU 60 detects engine coolant temperature THW. In S130, engine ECU 60 detects elapsed time T after the engine is started. In S140, engine ECU 60 detects atmospheric pressure and calculates atmospheric pressure correction coefficient A. For example, during idle operation in high altitudes, the lower the atmospheric pressure, the smaller the pumping loss of intake and exhaust, so there is a higher possibility that the required amount of fuel will be less than TAUmin, so the lower the atmospheric pressure, the lower the target fuel pressure Thus, the atmospheric pressure correction coefficient A is calculated. Here, it is assumed that the atmospheric pressure correction coefficient A is calculated to be larger as the atmospheric pressure is lower, and the target fuel pressure is corrected to be lower as the atmospheric pressure correction coefficient A is larger.

  In S150, engine ECU 60 determines whether engine coolant temperature THW is equal to or greater than the cold threshold value and elapsed time T after engine start is equal to or greater than the elapsed time threshold value. If engine coolant temperature THW is equal to or greater than the cold threshold value and elapsed time T after engine startup is equal to or greater than the elapsed time threshold value (YES in S150), the process proceeds to S160. If not (NO in S150), the process proceeds to S180.

  In S160, engine ECU 60 calculates target fuel pressure correction value ΔP from engine coolant temperature THW and atmospheric pressure correction coefficient A. At this time, the higher the engine cooling water temperature THW, the smaller the engine friction loss, and the lower the atmospheric pressure, the smaller the intake / exhaust pumping loss. Therefore, the higher the engine cooling water temperature THW and the larger the atmospheric pressure correction coefficient A is. The target fuel pressure correction value ΔP is calculated to be larger as the height is higher (as the altitude is higher).

  In S170, engine ECU 60 subtracts target fuel pressure correction value ΔP from basic target fuel pressure P to calculate a highland idle fuel pressure. In S180, engine ECU 60 calculates basic target fuel pressure P as a highland idle fuel pressure.

  An operation of engine ECU 60, which is a control device according to the present embodiment, based on the above-described structure and flowchart will be described.

  It is assumed that the engine cooling water temperature THW is equal to or higher than the cold threshold after the engine is started and exceeds a predetermined elapsed time threshold.

  The engine speed NE is detected (S100), and the basic target fuel pressure P is calculated from the engine speed NE (S110). The engine coolant temperature THW is detected (S120), and the elapsed time T after the engine is started is detected (S130). An atmospheric pressure is detected, and an atmospheric pressure correction coefficient A is calculated so as to calculate a target fuel pressure correction value ΔP that corrects the target fuel pressure to be lower as the atmospheric pressure is lower (S140).

  Since engine coolant temperature THW is equal to or greater than the cold threshold value and elapsed time T after engine start is equal to or greater than the elapsed time threshold value (YES in S150), engine coolant temperature THW and atmospheric pressure correction coefficient A target fuel pressure correction value ΔP is calculated from A (S160).

  At this time, when the engine has been started for a long time and the engine is at a high temperature, the engine oil has a high viscosity and the friction loss of the engine is small (the same applies to the oil in the transmission). Also, the lower the atmospheric pressure, the lower the pumping loss. In such a case, the required fuel amount supplied to the engine becomes low, and when the purge amount is subtracted from the required injection amount, the fuel injection amount from the in-cylinder injector 210 corresponds to the minimum injection amount corresponding to TAUmin. The possibility of falling below is high. Therefore, a target fuel pressure correction value ΔP that can be corrected so that the target fuel pressure P becomes lower is calculated.

  Since the target pressure (high altitude idle fuel pressure) of the fuel supplied from the high-pressure pump 230 to the in-cylinder injector 210 is lowered, the in-cylinder injection is performed even if the required fuel amount is small and / or the purge amount is large. Since the fuel injection time from the injector 210 is not less than the minimum injection time TAUmin, the purge process is not prohibited. This state is shown in FIG. FIG. 3A shows the injection time of the in-cylinder injector 210, and FIG. 3B shows the state of the purge execution flag.

  As shown in FIG. 3 (A), when the injection time of in-cylinder injector 210 is less than TAUmin (below the purge prohibition injection time), the purge execution flag is reset as shown in FIG. 3 (B). Therefore, the purge process is prohibited. Conventionally, in high altitude where atmospheric pressure is low, the fuel pressure remains high even during idle operation with a small amount of required fuel. Therefore, when the purge process is performed, the fuel injection time of the in-cylinder injector 210 is purge-inhibited. The purge process is prohibited because the time is running out. When the purge process is prohibited, the time for injecting the required fuel amount from which the purge amount is not subtracted from the required fuel amount from the in-cylinder injector 210 becomes longer, exceeds the purge permission injection time, and the purge process is resumed. When the purge process is resumed, the fuel pressure is high, so the fuel injection time of the in-cylinder injector 210 falls below the purge prohibition injection time again, the purge process is prohibited, the purge process is hunted, and the air-fuel ratio is disturbed. As a result, exhaust emissions deteriorate.

  On the other hand, if the fuel pressure is lowered as in the present invention, the fuel injection time from the in-cylinder injector 210 does not fall below the purge prohibition injection time, as shown in FIG. For this reason, as shown in FIG. 3B, the purge process is continued. For this reason, the vapor can be sufficiently processed, and deterioration of exhaust emission due to the hunting of the purge process can be suppressed.

  As described above, according to the engine ECU that is the control device according to the present embodiment, the pressure of the fuel supplied to the in-cylinder injector is reduced during idling operation at high altitude. For this reason, the fuel injection time does not fall below the minimum injection time, the purge process becomes difficult to be prohibited, the vapor can be processed, and the purge process can be continuously executed, so that deterioration of exhaust emission can be suppressed.

<Second Embodiment>
Hereinafter, a second embodiment of the present invention will be described. Since the hardware configuration is the same as that of the first embodiment described above, detailed description thereof will not be repeated here. In the present embodiment, engine ECU 60 executes a program different from the program in the above-described embodiment. In the present embodiment, the maximum purge rate is limited so that the fuel injection time from the in-cylinder injector 210 does not fall below the minimum injection time TAUmin so that the purge process is not prohibited. is there.

  A control structure of a program executed by engine ECU 60 according to the present embodiment will be described with reference to FIG. In this flowchart, the same steps as those in the flowchart of FIG. 2 are given the same step numbers. The contents of those processes are also the same. Therefore, detailed description thereof will not be repeated here.

  In S200, engine ECU 60 determines whether atmospheric pressure correction coefficient A is smaller than a correction coefficient threshold value. For example, it is determined whether or not the atmospheric pressure correction coefficient A is smaller than 0.9. If atmospheric pressure correction coefficient A is smaller than the correction coefficient threshold value (YES in S200), the process proceeds to S210. Otherwise (NO in S200), this process ends.

  In S210, engine ECU 60 calculates guard value GUD (1) by multiplying purge rate when purge control valve 1250 (VSV) is fully opened by constant α. The constant α is 0 <α <1, and is set to 0.06 (6%), for example. The guard value GUD (1) may be calculated based on 6% of the purge rate in this way, or the purge rate is calculated based on 6% of the drive duty when the purge control valve 1250 (VSV) is fully opened. Then, it may be calculated based on the purge rate.

  In S220, engine ECU 60 detects a final limit value GUD (2) of the purge rate. This final limit value GUD (2) is limited by factors other than the factor for preventing the fuel injection time from in-cylinder injector 210 from falling below minimum injection time TAUmin.

  In S230, engine ECU 60 determines whether or not purge limit final limit value GUD (2) ≦ guard value GUD (1). If final purge limit limit value GUD (2) ≦ guard value GUD (1) (YES in S230), the process proceeds to S240. Otherwise (NO at S230), this process ends.

  In S240, engine ECU 60 substitutes guard value GUD (1) for final limit value GUD (2) of the purge rate.

  An operation of engine ECU 60, which is a control device according to the present embodiment, based on the above-described structure and flowchart will be described.

  If atmospheric pressure correction coefficient A is smaller than the correction coefficient threshold value (YES in S200), it is based on a purge rate of 6% of the purge rate when VSV 1250 is fully opened or a purge rate that realizes a driving duty of VSV 1250 of 6%. The guard value GUD (1) is calculated (S210). If guard value GUD (1) is equal to or higher than purge rate final limit value GUD (2) (YES in S230), guard value GUD (1) is employed as purge rate final limit value GUD (2). (S240).

  This state is shown in FIG. 5A shows the VSV drive duty, FIG. 5B shows the purge rate, FIG. 5C shows the injection time of the in-cylinder injector 210, and FIG. 5D shows the state of the purge execution flag. , Respectively.

  In the present invention, as shown in FIGS. 5A and 5B, the VSV drive duty is set to 6%, and the purge rate for realizing the VSV drive duty of 6% is set to the guard value GUD (1). did. For this reason, as shown in FIG. 5C, the purge rate is lowered, so the purge amount decreases, and the fuel injection amount of the in-cylinder injector 210 is calculated by subtracting the purge amount from the required fuel amount. However, as shown in FIG. 5C, since the injection amount does not fall below the minimum fuel injection amount TAUmin, the purge process is not prohibited as shown in FIG. 5D.

  As described above, according to the engine ECU that is the control device according to the present embodiment, the purge rate is limited by reducing the purge rate in the purge process. Since the purge amount is small, the injection time of the in-cylinder injector will not be less than the minimum injection time TAUmin, and the purge process will not be prohibited, vapor can be processed, and the purge process can be executed continuously. Deterioration of emissions can be suppressed.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is an overall configuration diagram of an engine controlled by a control device according to a first embodiment of the present invention. It is a flowchart which shows the control structure of the program performed by engine ECU which is a control apparatus which concerns on the 1st Embodiment of this invention. It is a timing chart when it is performed by engine ECU which is a control device concerning a 1st embodiment of the present invention. It is a flowchart which shows the control structure of the program performed by engine ECU which is a control apparatus which concerns on the 2nd Embodiment of this invention. It is a timing chart when it is performed by engine ECU which is a control device concerning a 2nd embodiment of the present invention.

Explanation of symbols

  10 engine body, 30 starter, 60 engine ECU, 150 spark plug, 160 intake valve, 170 exhaust valve, 190 throttle valve, 210 in-cylinder injector, 300 transmission, 310 clutch, 420 accelerator pedal, 430 clutch pedal, 520 crank Angular sensor, 530 A / F sensor, 540 throttle opening sensor, 550 accelerator opening sensor, 560 neutral start switch, 570 vehicle speed sensor, 1000 combustion chamber, 1010 intake passage, 1020 exhaust passage.

Claims (4)

A control device for an internal combustion engine, comprising fuel injection means for injecting fuel into a cylinder, and performing a purge process of fuel evaporative gas,
Injection of fuel by the fuel injection means based on the pressure of fuel supplied to the fuel injection means so as to inject fuel of a required fuel amount determined based on conditions required for the internal combustion engine and atmospheric pressure Control means for controlling the time ;
And a adjusting means for adjusting the pressure of the fuel supplied to the fuel injection means,
The adjusting means, the higher the atmospheric pressure is low, see contains means for adjusting so as to reduce the pressure of the fuel,
The control unit of the internal combustion engine sets the injection time so that the required fuel amount set smaller as the atmospheric pressure is lower is injected at the fuel pressure reduced by the adjusting unit. . The control means calculates a fuel injection amount by correcting the decrease in the required fuel amount with the execution of the purge process,
The adjusting means includes means for reducing the pressure of the fuel;
The amount of decrease in the pressure of the fuel is a decrease amount such that the fuel injection amount corrected for decrease in the fuel pressure after the decrease does not fall below the minimum injection amount of the fuel injection means. The internal combustion engine control device described.   The control apparatus for an internal combustion engine according to claim 2, wherein the minimum injection amount is an injection amount corresponding to a minimum injection time determined by a characteristic of the fuel injection means at the fuel pressure after the decrease. Wherein the control device, even when the pressure of the fuel by the adjusting means is reduced, if below the minimum injection quantity injection amount by decreasing correction by the purge correction is to reduce the amount of purge The control device for an internal combustion engine according to claim 3, further comprising means.

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