JP2010024853A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately grasp the delivery quantity of a fuel pump, in a control device for an internal combustion engine capable of changing over set fuel pressure in a delivery pipe in a plurality of steps according to an operation state of the internal combustion engine. <P>SOLUTION: The fuel pump 11 pressure-feeds fuel in a fuel tank 10 to a delivery pipe 30 connected to a fuel injection valve 31 through a main passage 20. An electronic control device 80 changes over set fuel pressure FP in the delivery pipe 30 in the plurality of steps by controlling a change over valve 40 according to the operation state of the engine 50, and controls fuel supply quantity injected from the fuel injection valve 31 through adjustment of open timing of the fuel injection valve 31 corresponding to the set fuel pressure FP. The electronic control device 80 determines fuel delivery efficiency E of the fuel pump 11 lower as changed over set fuel pressure FP is higher, and calculates delivery quantity Flow of the fuel pump 11 based on the delivery efficiency E and apply voltage to the fuel pump 11. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control device capable of switching a set fuel pressure in a delivery pipe in a plurality of stages in accordance with an operation state of the internal combustion engine.

  In general, in a configuration in which fuel is pumped by an electric fuel pump to a delivery pipe to which a fuel injection valve is connected, a part of the fuel discharged by the fuel pump is returned to the fuel tank via a pressure regulator. Thus, the fuel pressure in the delivery pipe is regulated to a predetermined pressure. Then, by controlling the fuel pressure in the delivery pipe, that is, the fuel injection pressure in this way, the fuel supply amount supplied from the fuel injection valve to the internal combustion engine is based on the fuel injection pressure and the valve opening period of the fuel injection valve. It is controlled.

In recent years, in internal combustion engines, the amount of fuel supply must be appropriately controlled when a mixed fuel of alcohol and gasoline having a lower stoichiometric air-fuel ratio than gasoline fuel is used or when high output is required. Is required. Therefore, as described in Patent Document 1, a configuration capable of switching the fuel injection pressure in a plurality of stages has been proposed. In the configuration described in Patent Document 1, a high-pressure return passage provided with a high-pressure regulator and a low-pressure regulator are provided as return passages for returning surplus fuel to the fuel tank when the fuel injection pressure exceeds a predetermined pressure. A low pressure return passage is provided, and these return passages are switched according to the operating state of the internal combustion engine. As a result, the fuel injection pressure is set to a low pressure when the engine is in a low load state, and the accuracy of the supply amount control is ensured in a region where the fuel supply amount is relatively small, while the fuel injection pressure is increased in a high load state. A large amount of fuel supply is secured.
JP-A-5-59976

  However, as described in Patent Document 1, a configuration in which the fuel injection pressure can be set in a plurality of stages, that is, a configuration in which the set fuel pressure in the delivery pipe to which the fuel injection valve is connected can be switched in a plurality of stages. In this case, even when the same voltage is applied to the fuel pump, it has been found that the discharge rate of the fuel pump decreases when the set fuel pressure of the delivery pipe increases.

  Here, the amount of air required for the internal combustion engine is supplied through the intake passage, and an amount of fuel corresponding to the required amount of air is supplied by the fuel injection valve. The amount of fuel supplied by the fuel injection valve is controlled by the fuel injection pressure corresponding to the set fuel pressure and the valve opening period of the fuel injection valve. When the amount of fuel to be pumped decreases, the actual fuel pressure in the delivery pipe does not increase to the set fuel pressure, and the fuel injection pressure decreases, or the actual fuel supply amount supplied to the engine decreases. There is a risk of this happening. When this occurs, there is a problem that the fuel supply amount is insufficient with respect to the supplied air, that is, a lean state occurs.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a control device for an internal combustion engine capable of switching a set fuel pressure in a delivery pipe in a plurality of stages in accordance with an operation state of the internal combustion engine. It is to appropriately grasp the discharge amount of the fuel pump.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 is an electric fuel pump that pumps fuel in a fuel tank through a main passage to a delivery pipe to which a fuel injection valve that supplies fuel to an internal combustion engine is connected, and a set fuel pressure of the delivery pipe And a fuel pressure switching means for switching the fuel injection valve in a plurality of stages according to the operating state of the engine, and supplying fuel by controlling a valve opening period of the fuel injection valve corresponding to the set fuel pressure switched by the fuel pressure switching means In the control device for an internal combustion engine in which the amount is controlled, the higher the set fuel pressure switched by the applied voltage detecting means for detecting the applied voltage to the fuel pump and the fuel pressure switching means, the higher the fuel discharge efficiency by the fuel pump. A discharge efficiency determining means for determining a low value, an applied voltage detected by the applied voltage detecting means, and a determination by the discharge efficiency determining means. And summarized in that and a discharge quantity calculating means for calculating the discharge amount of the fuel pump based on the discharge efficiency is.

  The discharge amount of the fuel pump decreases as the voltage applied to the fuel pump decreases, and decreases as the fuel pressure in the delivery pipe and the main passage increases. Therefore, it can be determined that the higher the set fuel pressure switched by the fuel pressure switching means, the more the discharge amount of the fuel pump tends to decrease when the same voltage is applied.

  Therefore, as described above, the applied voltage detection means for detecting the applied voltage to the fuel pump, and the discharge efficiency determination means for determining the fuel discharge efficiency by the fuel pump to be lower as the set fuel pressure switched by the fuel pressure switching means is higher. By calculating the discharge amount of the fuel pump based on the applied voltage and the discharge efficiency, it is possible to appropriately grasp the discharge amount of the fuel pump. As a result, the fuel pressure in the delivery pipe and the fuel supply amount by the fuel injection valve can be appropriately controlled based on the fuel pump discharge amount thus grasped.

  Specifically, as described in claim 2, the fuel pressure switching means is provided in the high pressure return passage for returning the fuel in the delivery pipe to the fuel tank, and the fuel pressure in the passage is provided in the high pressure return passage. A high pressure regulator that opens when the pressure is equal to or higher than 1 and discharges fuel to the fuel tank; a low pressure return passage that is branched from the main passage and returns the fuel in the main passage to the fuel tank; A low pressure regulator that is provided in the low pressure return passage and opens when the fuel pressure in the passage is equal to or higher than a second predetermined pressure lower than the first predetermined pressure, and discharges fuel to the fuel tank side; and a low pressure return passage It is possible to employ a configuration including a switching valve that switches between opening and closing of the engine according to the operating state of the engine.

  In such a configuration, when the low pressure return passage is closed by the switching valve, the fuel pressure in the delivery pipe and the main passage is adjusted to the first predetermined pressure (high pressure side) by the high pressure regulator. On the other hand, when the low pressure return passage is opened by the switching valve, the fuel pressure in the main passage is adjusted to the second predetermined pressure by the low pressure regulator, whereby the fuel pressure in the delivery pipe is adjusted to the second predetermined pressure (low pressure). Side) will be adjusted.

  According to a third aspect of the present invention, in the control device for an internal combustion engine according to the first or second aspect, a required air amount calculating means for calculating a required air amount of the engine and a discharge grasped by the discharge amount calculating means. A limit air amount calculating means for calculating a maximum air amount allowed to be supplied to the engine based on the amount as a restricted air amount, a required air amount calculated by the required air amount calculating means and the restricted air amount calculating means And an air amount control means for supplying a smaller air amount to the engine among the restricted air amount calculated by the above.

  Here, in the configuration provided with the fuel pressure switching means, it is assumed that the fuel pressure in the delivery pipe has increased to the set fuel pressure, and the fuel injection valve of the fuel injection valve corresponds to the set fuel pressure. Since the fuel supply amount is controlled by controlling the valve opening period, the actual fuel supply amount is reduced when the discharge amount of the fuel pump decreases and the actual fuel pressure in the delivery pipe does not rise to the set fuel pressure. There is a risk of lowering the desired fuel supply amount. When the fuel supply amount decreases in this way, there is a risk that the fuel will be insufficient with respect to the amount of air supplied to the engine, that is, a lean state.

  In this regard, according to the above configuration, the required air amount calculating means for calculating the required air amount of the engine, and the maximum air amount allowed to be supplied to the engine based on the discharge amount grasped by the discharge amount calculating means is limited. A limited air amount calculating means for calculating the air amount, and a smaller air amount of the required air amount calculated by the required air amount calculating means and the restricted air amount calculated by the restricted air amount calculating means is supplied to the engine Air amount control means, and when the restricted air amount exceeds the required air amount, the required air amount is supplied to the engine, and the discharge amount of the fuel pump is reduced so that the restricted air amount becomes the required air amount. When the amount is below the amount, the amount of air supplied to the engine can be limited to the restricted amount of air calculated based on the discharge amount of the fuel pump. Therefore, the amount of air supplied to the engine can be appropriately controlled according to the discharge amount of the fuel pump, and the balance between the amount of air supplied to the engine and the amount of fuel can be appropriately maintained.

  According to a fourth aspect of the present invention, in the control device for an internal combustion engine according to the third aspect, the engine is an engine capable of using a mixed fuel in which alcohol and gasoline are arbitrarily mixed, and Alcohol concentration detection means for detecting the alcohol concentration of the mixed fuel stored in the fuel tank is provided, and the limit air amount calculation means calculates the limit air amount as the alcohol concentration detected by the alcohol concentration detection means increases. The gist is to do.

  A mixed fuel in which alcohol and gasoline are arbitrarily mixed has a smaller theoretical air-fuel ratio than gasoline fuel, so in an internal combustion engine in which mixed fuel is used, compared to an internal combustion engine in which gasoline fuel is used, It is necessary to supply a large amount of fuel for the same amount of air. Therefore, in an internal combustion engine that can use such a mixed fuel, the load on the fuel pump tends to increase.

  According to the above configuration, the alcohol concentration detection unit that detects the alcohol concentration of the mixed fuel stored in the fuel tank is provided, and the limit air amount calculation unit is configured such that the higher the alcohol concentration detected by the alcohol concentration detection unit, the higher the limit air amount. Therefore, the higher the alcohol concentration, the more the amount of air supplied to the engine can be restricted, and the balance between the air amount and the fuel amount can be appropriately maintained. On the other hand, when the alcohol concentration is low, a large amount of restricted air is calculated, so that unnecessary restriction of the amount of air can be suppressed.

  Specifically, as described in claim 5, the fuel injection valve can be a port injection fuel injection valve that injects fuel into the intake port of the engine.

(First embodiment)
Hereinafter, a first embodiment in which a control device for an internal combustion engine according to the present invention is embodied in a control device for an internal combustion engine mounted on a flexible fuel vehicle (FFV) will be described with reference to FIGS. FFV refers to a vehicle that can use only alcohol fuel (alcohol concentration 100%), only gasoline fuel (alcohol concentration 0%), or a mixed fuel in which alcohol and gasoline are arbitrarily mixed.

  FIG. 1 shows an internal combustion engine 50 according to the present embodiment and its peripheral configuration. An internal combustion engine 50 shown in the figure is an engine that can use a mixed fuel in which alcohol and gasoline are arbitrarily mixed. The internal combustion engine 50 has a plurality of cylinders 51. Each is accommodated so that it can reciprocate. A combustion chamber 52 is defined by the top surface of the piston 53 and the inner peripheral surface of the cylinder 51.

  An intake passage 60 for supplying air to the combustion chamber 52 is provided with a throttle valve 61 for adjusting the flow rate of the intake air amount GA flowing through the passage 60 and a throttle valve actuator 62 for driving the throttle valve 61 to open and close. ing. The throttle valve 61 is provided with a throttle opening sensor 63 for detecting the opening TA.

  Further, in the intake passage 60, an intake port 60a is formed corresponding to each cylinder 51, and a fuel injection valve 31 for supplying fuel into the intake port 60a is provided. The fuel injected from the fuel injection valve 31 is mixed with the air flowing through the intake passage 60 and supplied to the combustion chamber 52. The air-fuel mixture supplied to the combustion chamber 52 is ignited by the spark plug 54 and burned, and the exhaust gas after combustion is discharged to the exhaust passage 70.

  The exhaust passage 70 is provided with an exhaust purification catalyst 71 for purifying the exhaust gas flowing through the exhaust passage 70, and in the upstream portion of the catalyst 71, the air-fuel mixture burned in the combustion chamber 52 is empty. An air-fuel ratio sensor 72 for detecting the oxygen concentration and the unburned fuel concentration in the exhaust gas is attached to grasp the fuel ratio.

  The fuel tank 10 stores a mixed fuel in which alcohol and gasoline are arbitrarily mixed, and a fuel pump 11 is provided in the tank 10. The fuel pump is an electric fuel pump, and continuously discharges fuel during engine operation when a voltage is applied from the battery 13. The fuel pump 11 is connected to a main passage 20 via a filter 12 that removes fine foreign matters in the fuel, and the main passage 20 is connected to a delivery pipe 30 that temporarily stores fuel. .

  A fuel injection valve 31 connected to each intake port 60a is connected to the delivery pipe 30. The delivery pipe 30 is connected to a high pressure return passage 41 for returning the fuel in the delivery pipe 30 to the fuel tank 10, and the fuel pressure P in the passage 41 is connected to the high pressure return passage 41 by the first pressure. A high pressure regulator 42 is attached that opens when the pressure is equal to or higher than a predetermined pressure Ph (for example, 400 kPa) and discharges fuel to the fuel tank 10 side.

  The main passage 20 is provided with a low-pressure return passage 43 that is branched from the main passage 20 and returns the fuel in the main passage 20 to the fuel tank 10. The low pressure return passage 43 is attached with a low pressure regulator 44 that opens when the fuel pressure in the passage 43 is equal to or higher than a second predetermined pressure Pl (for example, 284 kPa) and discharges fuel to the fuel tank 10 side. It has been.

  Further, the low pressure return passage 43 is provided with a switching valve 40 that switches between opening and closing of the low pressure return passage 43 according to the operating state of the engine 50. The switching valve 40 is a normally-open solenoid valve that closes when a voltage is applied. When the switching valve 40 is closed, the low-pressure return passage 43 is closed.

  The fuel pressure switching means is configured by such a configuration, and the set fuel pressure FP in the delivery pipe 30 is switched through switching between opening and closing of the low pressure return passage 43 by the switching valve 40. Specifically, when the set fuel pressure FP is switched to the first predetermined pressure Ph, the low pressure return passage 43 is closed by the switching valve 40, and the pressure adjustment by the high pressure regulator 42 is performed. Thus, the fuel pressure P in the high pressure return passage 41 on the upstream side of the high pressure regulator 42, the delivery pipe 30 and the main passage 20 is adjusted to the first predetermined pressure Ph (high pressure side), and the fuel injection pressure is adjusted. It is kept at a relatively high value.

  On the other hand, when the set fuel pressure FP is switched to the second predetermined pressure Pl, the low pressure return passage 43 is opened by the switching valve 40, and pressure regulation by the low pressure regulator 44 is performed. Thus, the fuel pressure P in the low pressure return passage 43 on the upstream side of the low pressure regulator 44, the main passage 20 and the delivery pipe 30 is adjusted to the second predetermined pressure Pl (low pressure side), and the fuel injection pressure is adjusted. It is kept at a relatively low value.

  The switching valve 40 is controlled by an electronic control unit 80 that comprehensively controls the operating state of the internal combustion engine 50. The electronic control unit 80 includes a calculation unit (CPU), a memory that stores various control programs, calculation maps, data calculated when the control is executed, and the like. The electronic control unit 80 also includes a voltage sensor 81 (corresponding to an applied voltage detecting means) for detecting the voltage of the battery 13 that supplies power to the fuel pump 11, that is, an applied voltage to the fuel pump 11, and an accelerator pedal by the driver. An accelerator position sensor 82 for detecting the amount of depression ACCP of the engine, an alcohol concentration sensor 83 (corresponding to alcohol concentration detection means) for detecting the alcohol concentration Conc of the fuel stored in the fuel tank 10, and a crank angle for detecting the engine speed NE A sensor 84, an intake air temperature sensor 85 for detecting the intake air temperature (intake air temperature) THA, an atmospheric pressure sensor 86 for detecting the atmospheric pressure PA, and the like are connected. The electronic control device 80 takes in the output signals of the various sensors described above, grasps the engine operating state based on these signals, and executes various controls based on the engine operating state. Specifically, the electronic control unit 80 controls the switching valve 40 described above, throttle control for driving the throttle valve actuator 62 to control the throttle opening degree TA, and the amount of air supplied to the combustion chamber 52. In contrast, fuel injection control for supplying an appropriate amount of fuel from the fuel injection valve 31 at an appropriate timing, ignition timing control for igniting the air-fuel mixture in the combustion chamber 52 by an ignition plug 54 at an appropriate timing, and the like are executed. .

  Here, the amount of fuel injected by the fuel injection valve 31 is controlled by the fuel injection pressure and the valve opening period of the fuel injection valve 31. Specifically, it is assumed that the actual fuel pressure P in the delivery pipe 30 corresponding to the fuel injection pressure has increased to the set fuel pressure FP, and the valve opening period corresponding to the set fuel pressure FP. The amount of fuel is controlled by adjusting. Therefore, when the electronic control unit 80 determines that the operating region needs to inject a large amount of fuel, such as during high load operation or engine cold start, the set fuel pressure FP is switched to the first predetermined pressure Ph. By increasing the fuel injection pressure in this way, a large amount of fuel is injected in one intake stroke. On the other hand, if it is determined that the operation region is other than that, the set fuel pressure FP is switched to the second predetermined pressure Pl to change the fuel injection pressure. The fuel supply amount is appropriately controlled by executing a precise control with respect to a relatively small amount of fuel by lowering the fuel flow rate.

  Next, with reference to FIG. 2, a procedure of processing executed by the electronic control unit 80 will be described. The flowchart shown in FIG. 2 is repeatedly executed with a predetermined cycle by the electronic control unit 80.

  In this series of processing, first, the required opening degree TAd is grasped (step S100). The required opening degree TAd is an opening degree required for the throttle valve 61 to supply the air amount GAd required for the internal combustion engine 50 to the combustion chamber 52. Specifically, the required opening degree TAd is an output signal of the accelerator position sensor 82. Is determined based on the accelerator pedal depression amount ACCP corresponding to the engine speed NE and the engine speed NE determined based on the output signal of the crank angle sensor 84. The process in step S100 corresponds to a process as a required air amount calculation unit.

  Here, even when the same battery voltage GAB is applied, the discharge efficiency of the fuel pump 11 decreases as the fuel pressure P in the delivery pipe 30 and the main passage 20 increases. That is, as shown in FIG. 3, the higher the set fuel pressure FP, the lower the discharge efficiency of the fuel pump 11 when the same battery voltage GAB is applied.

  Therefore, the discharge efficiency E is determined based on the set fuel pressure FP (step S110). The discharge efficiency E indicates the ease with which the fuel is discharged from the fuel pump 11. When the battery voltage GAB is the same, more fuel is discharged as the discharge efficiency E is higher. This set fuel pressure FP is grasped based on the control state of the switching valve 40 by the electronic control unit 80. Accordingly, when the set fuel pressure FP is the first predetermined pressure Ph (high pressure side), it is determined that the discharge efficiency E is lower than when the set fuel pressure FP is the second predetermined pressure Pl (low pressure side). The processing in step S110 corresponds to processing as ejection efficiency determination means.

  Here, the fuel pump 11 is configured to continuously discharge a certain amount of fuel when a rated voltage is applied during engine operation. However, the voltage GAB of the battery 13 that applies power to the fuel pump 11 in this way may be reduced by the driver operating various devices (such as an air conditioner) provided in the vehicle on which the internal combustion engine 50 is mounted. is there. As shown in FIG. 4, the discharge amount Flow of the fuel pump 11 decreases as the battery voltage GAB applied to the fuel pump 11 decreases.

  Therefore, the discharge amount Flow is calculated based on the discharge efficiency E and the battery voltage GAB determined in step S110 (step S120). Specifically, the battery voltage GAB is grasped based on the output signal of the voltage sensor 81. The processing in step S120 corresponds to processing as a discharge amount calculating unit. That is, when the battery voltage GAB is the same by the processing of step S110 and step S120, the discharge amount Flow is calculated to be smaller as the set fuel pressure FP is higher. When the set fuel pressure FP is the same, the battery voltage GAB is calculated. The lower the value is, the smaller the discharge amount Flow is calculated. The relationship between the set fuel pressure FP and the discharge efficiency E shown in FIG. 3 and the relationship between the battery voltage GAB and the discharge amount Flow shown in FIG. 4 are determined and stored in advance by theoretical calculation or experiment. Yes.

  By the way, as described above, the fuel pressure in the delivery pipe 30, that is, the fuel injection pressure is adjusted by switching the set fuel pressure FP by the switching valve 40. However, the actual fuel pressure P in the delivery pipe 30 changes according to the discharge amount Flow by the fuel pump 11. For example, when the discharge amount Flow of the fuel pump 11 decreases, the actual fuel pressure P in the delivery pipe 30 may not rise to the set fuel pressure FP. Due to such a change in the fuel pressure P, the fuel supply amount controlled based on the fuel injection pressure of the fuel injection valve 31 and the valve opening period changes. When the fuel supply amount actually supplied falls below the fuel supply amount corresponding to the required air amount GAd, there is a possibility that the fuel becomes insufficient with respect to the supplied air.

  Therefore, the restricted air amount GAp is calculated based on the discharge amount Flow and the alcohol concentration Conc calculated in step S120 (step S130). This limited air amount GAp corresponds to the maximum air amount allowed to be supplied to the combustion chamber 52 of the internal combustion engine 50 in correspondence with the discharge amount Flow calculated in step S120. That is, the restricted air amount GAp is an air amount corresponding to the actual fuel supply amount estimated based on the calculated discharge amount Flow, and is grasped based on the discharge amount Flow and an output signal of the alcohol concentration sensor 83. Based on the alcohol concentration Conc to be calculated, for example, by referring to a map stored in advance for each value of the discharge amount Flow. Here, since the theoretical air-fuel ratio of alcohol is smaller than the theoretical air-fuel ratio of gasoline, as shown in FIG. 5, the higher the alcohol concentration Conc, the lower the restricted air amount GAp is calculated. That is, even if the discharge amount Flow is the same, the amount of air actually supplied to the combustion chamber 52 is calculated to be smaller as the alcohol concentration Conc becomes higher. The process in step S130 corresponds to a process as a restriction air amount calculation unit.

  Next, the limit opening degree TAp is calculated based on the limit air amount GAp calculated in step S130, the intake air temperature THA, the atmospheric pressure PA, and the engine speed NE (step S140). The limit opening TAp is a throttle opening for supplying the calculated limit air amount GAp to the combustion chamber 52. Specifically, the intake air temperature THA is grasped based on the output signal of the intake air temperature sensor 85, the atmospheric pressure PA is grasped based on the atmospheric pressure sensor 86, and the engine speed NE is based on the output signal of the crank angle sensor 84. Be grasped.

  As described above, the intake air amount GA flowing through the intake passage 60 is adjusted by the throttle valve 61. When the density of the intake air adjusted by the throttle valve 61 changes in this way, the mass of air supplied to the combustion chamber 52 changes even if the volume is the same. Here, since the air-fuel ratio of the air-fuel mixture in the combustion chamber 52 is determined by the ratio of the mass of fuel and air, the throttle opening degree TA is set based on the intake air temperature THA and the atmospheric pressure PA related to the air density. Make corrections. Further, since the flow velocity of the intake air flowing through the intake passage 60 changes based on the engine speed NE, the throttle opening degree TA is adjusted by the engine speed NE. That is, the limit opening degree TAp is determined by referring to a previously stored map in consideration of the intake air temperature THA, the atmospheric pressure PA, and the engine speed NE in addition to the calculated limit air amount GAp. .

  Subsequently, the required opening degree TAd and the limit opening degree TAp are adjusted to the smaller one (step S150), and the series of processes is terminated. Specifically, the throttle valve 61 is driven by driving the throttle valve actuator 62 to a smaller one of the required opening degree TAd obtained in step S100 and the restriction opening degree TAp calculated in step S140. The opening degree TA is controlled. The processing in step S150 corresponds to processing as air amount control means.

According to 1st Embodiment described above, there can exist the following effects.
(1) The fuel discharge efficiency E by the fuel pump 11 is judged to be lower as the set fuel pressure FP is higher (step S110), and the discharge amount Flow of the fuel pump 11 is calculated based on the discharge efficiency E and the battery voltage GAB ( By step S120), the discharge amount Flow of the fuel pump 11 can be properly grasped. As a result, the fuel pressure P in the delivery pipe 30 and the fuel supply amount by the fuel injection valve 31 can be appropriately controlled based on the discharge amount Flow of the fuel pump 11 thus grasped.

  (2) In this embodiment, the fuel pressure P in the delivery pipe 30 is not directly detected by a fuel pressure sensor or the like and the fuel pressure P in the pipe 30 is not controlled, but the set fuel pressure FP is switched using the switching valve 40. It is controlled by. Then, it is assumed that the actual fuel pressure P in the delivery pipe 30 has risen to the set fuel pressure FP, and the valve opening period of the fuel injection valve 31 is controlled corresponding to the set fuel pressure FP. The fuel supply amount is controlled. Accordingly, when the discharge amount Flow of the fuel pump 11 decreases and the actual fuel pressure P in the delivery pipe 30 does not rise to the set fuel pressure FP, the actual fuel supply amount is the desired fuel supply amount, that is, the required air amount GAd. There is a risk that the fuel supply amount corresponding to In this regard, according to the present embodiment, the required air amount GAd of the engine 50 is calculated, the restricted air amount GAp is calculated based on the calculated discharge amount Flow, and the required air amount GAd and the restricted air amount GAp are calculated. The throttle opening degree TA is adjusted to the smaller one of the required opening degree TAd corresponding to the required air amount GAd and the limiting opening degree TAp corresponding to the limiting air amount GAp so that the smaller one is supplied to the engine 50. (Step S150). Accordingly, when the restricted air amount GAp exceeds the requested air amount GAd, the requested air amount GAd is supplied to the engine 50, and the discharge amount Flow of the fuel pump 11 is reduced so that the restricted air amount GAp becomes the requested air amount. When it is less than GAd, the amount of air supplied to the engine 50 can be limited to the limit air amount GAp calculated based on the discharge amount Flow of the fuel pump 11. Therefore, the amount of air supplied to the engine 50 can be appropriately controlled according to the discharge amount Flow of the fuel pump 11, and the balance between the amount of air supplied to the engine 50 and the amount of fuel can be appropriately maintained. It becomes like this.

  (3) Since the mixed fuel in which alcohol and gasoline are arbitrarily mixed has a smaller theoretical air-fuel ratio than gasoline fuel, the internal combustion engine 50 in which the mixed fuel is used is different from the internal combustion engine in which the gasoline fuel is used. In comparison, it is necessary to supply more fuel for the same amount of air. Therefore, in an internal combustion engine that can use such a mixed fuel, the load on the fuel pump 11 tends to increase. In this regard, according to the present embodiment, the alcohol concentration sensor 83 that detects the alcohol concentration Conc of the mixed fuel stored in the fuel tank 10 is provided. In step S130, the higher the alcohol concentration Conc, the smaller the restricted air amount GAp is calculated. Therefore, the higher the alcohol concentration Conc, the more the amount of air supplied to the engine 50 can be limited, and the balance between the air amount and the fuel amount can be appropriately maintained. On the other hand, when the alcohol concentration Conc is low, the restriction air amount GAp is calculated to be large, so that unnecessary restriction of the air amount can be suppressed. That is, the throttle opening degree TA can be adjusted appropriately according to the alcohol concentration Conc, and when the alcohol concentration Conc is low, an unnecessary decrease in the throttle opening degree TA can be suppressed.

  (4) When the fuel supply amount is insufficient with respect to the air supplied to the combustion chamber 52, that is, in a lean state, the ignitability of the air-fuel mixture in the combustion chamber 52 is lowered and misfire may occur. If unburned fuel discharged by such misfires burns in the exhaust passage 70, the exhaust purification catalyst 71 may be overheated. In this regard, in the present embodiment, when the restriction opening degree TAp is less than the required opening degree TAd, the amount of air supplied to the combustion chamber 52 is reduced to the restriction air amount GAp by adjusting the throttle opening degree TA to the restriction opening degree TAp. Therefore, the air-fuel mixture in the combustion chamber 52 can be prevented from entering a lean state, and such overheating of the exhaust purification catalyst 71 can be suppressed.

  (5) Since the fuel injection pressure can be controlled by switching the set fuel pressure FP through the control of the switching valve 40 according to the engine operating state, the fuel supply amount corresponding to the engine operating state can be appropriately controlled. . That is, by keeping the fuel injection pressure relatively high, it is possible to increase the amount of fuel that is injected and supplied in a single intake stroke, and to use a mixed fuel of alcohol and gasoline having a smaller theoretical air-fuel ratio than gasoline fuel. In the engine 50, the required large amount of fuel can be supplied. On the other hand, since the fuel injection pressure can be kept relatively low by switching the set fuel pressure FP through the control of the switching valve 40, the fuel supply amount is precisely controlled even when the fuel supply amount is small. Can do.

(Second Embodiment)
Hereinafter, a second embodiment of the control device for an internal combustion engine according to the present invention will be described. This embodiment differs from the first embodiment in the following points. That is, the internal combustion engine 50 in the first embodiment is an engine that can use an alcohol mixed fuel in which alcohol and gasoline are arbitrarily mixed. However, the internal combustion engine 50 in the present embodiment is a gasoline fuel. It is an institution that can only be used. In the first embodiment, the required opening degree TAd and the restricted opening degree TAp are compared in step S150. However, in the present embodiment, the required air amount GAd and the restricted air amount GAp are directly compared. The amount of air GA supplied to the combustion chamber 52 is determined by comparison. Note that detailed description of the same processing and configuration as in the above embodiment will be omitted.

  Hereinafter, the procedure of processing executed by the electronic control unit 80 will be described with reference to FIG. A series of processes shown in the flowchart of FIG. 8 is repeatedly executed by the electronic control unit 80 with a predetermined period.

In this series of processes, first, the required air amount GAd is calculated (step S200).
Then, the discharge efficiency E is determined based on the set fuel pressure FP (step S210), and the discharge amount Flow is calculated based on the discharge efficiency E thus determined and the battery voltage GAB (step S220).

  Next, the restricted air amount GAp is calculated based on the discharge amount Flow (step S230). In addition, since only the gasoline fuel is used for the internal combustion engine 50 in the present embodiment, it is not necessary to consider the alcohol concentration Conc as in step S130.

  Subsequently, the required air amount GAd and the restricted air amount GAp are adjusted to the smaller one (step S240), and the series of processing ends. Specifically, adjustment is made so that the smaller air amount GA of the required air amount GAd determined in step S200 and the restricted air amount GAp calculated in step S230 is supplied to the combustion chamber 52. Specifically, similarly to the first embodiment, the opening degree TA of the throttle valve 61 is controlled so as to correspond to the determined air amount GA. Further, in a configuration including a variable valve timing mechanism (VVT) that can variably set the valve timings of the intake valve and the exhaust valve of the internal combustion engine 50, the amount of air supplied to the combustion chamber 52 through driving of the variable valve timing mechanism. GA can also be adjusted. Further, in the configuration including the variable intake mechanism (ACIS) that optimizes the intake efficiency by changing the intake pipe length according to the engine speed NE, the amount of air supplied to the combustion chamber 52 through controlling the variable intake mechanism. GA can also be adjusted.

According to the second embodiment described above, the following operational effects can be obtained in addition to the operational effects shown in (1) above.
(6) The required air amount GAd of the engine 50 is calculated, and the maximum air amount allowed to be supplied to the engine 50 is calculated as the restricted air amount GAp based on the calculated discharge amount Flow, and these required air amounts GAd are calculated. Therefore, when the restricted air amount GAp exceeds the required air amount GAd, the smaller one of the restricted air amount GAp is adjusted as the air amount GA actually supplied to the engine 50 (step S240). When the required air amount GAd is supplied and the discharge amount Flow of the fuel pump 11 decreases and the restricted air amount GAp is less than the required air amount GAd, the amount of air supplied to the engine 50 is reduced. It can be limited to the restricted air amount GAp calculated based on the discharge amount Flow. Therefore, the amount of air supplied to the engine 50 can be appropriately controlled according to the discharge amount Flow of the fuel pump 11, and the balance between the amount of air supplied to the engine 50 and the amount of fuel can be appropriately maintained. It becomes like this.

  (7) When the restricted air amount GAp is less than the required air amount GAd, the air amount GA supplied to the combustion chamber 52 is reduced to the restricted air amount GAp, so that the air-fuel mixture in the combustion chamber 52 is prevented from entering a lean state. And overheating of the exhaust purification catalyst 71 can be suppressed.

(Other embodiments)
The control device for an internal combustion engine according to the present invention is not limited to the configuration exemplified in the above embodiment, and can be implemented as, for example, the following form obtained by appropriately modifying the embodiment. .

  In the first embodiment, the example in which the alcohol concentration Conc of the fuel is detected based on the output signal of the alcohol concentration sensor 83 is shown, but the method for detecting the alcohol concentration Conc is not limited to this example. For example, the well-known “alcohol concentration estimation process” for estimating the alcohol concentration by detecting the air-fuel ratio of the air-fuel mixture in the combustion chamber 52 based on the output signal of the air-fuel ratio sensor 72 provided in the exhaust passage 70 may be executed. Good.

  In each of the above embodiments, the example in which the set fuel pressure FP is switched to two stages has been shown. However, the stage of the set fuel pressure FP is not limited to two stages, and may include fuel pressure switching means for switching to more stages. Good. Even in this case, the higher the set fuel pressure FP, the lower the discharge efficiency E of the fuel pump 11 can be determined, and the above-described effects can be achieved. Further, the installation location of the switching valve 40 and the like in the fuel pressure switching means is not limited to the above example. For example, as shown in FIG. 7, a high pressure return passage 141 formed by branching from the main passage 120, and a fuel pressure in the high pressure return passage 141 provided in the high pressure return passage 141 is equal to or higher than a first predetermined pressure Ph. The high pressure regulator 142 that opens at this time and discharges fuel to the fuel tank 10 side, the low pressure return passage 143 that returns the fuel in the delivery pipe 30 to the fuel tank 10, and the low pressure return passage 143 that is provided in the same passage A low pressure regulator 144 that opens when the fuel pressure in the fuel tank 143 is equal to or higher than a second predetermined pressure Pl set lower than the first predetermined pressure Ph, and discharges fuel to the fuel tank 10 side; and a low pressure return passage You may employ | adopt the structure provided with the switching valve 140 which switches open | release and obstruction | occlusion of 143 according to an engine operating state. Further, as shown in FIG. 8, the high pressure return passage 241 formed by branching from the main passage 220, the high pressure regulator 242 provided in the high pressure return passage 241, and the low pressure formed by branching from the main passage 220. A configuration including a return passage 243, a low pressure regulator 244 provided in the low pressure return passage, and a switching valve 240 that switches between opening and closing of the low pressure return passage 243 depending on the engine operating state may be adopted. Even in these cases, when the set fuel pressure FP is set high and the low pressure return passages 143 and 243 are closed by the switching valves 140 and 240, the fuel pressure in the delivery pipe 30 is regulated by the high pressure regulators 142 and 242. And held at the first predetermined pressure Ph. On the other hand, when the set fuel pressure FP is set low and the low pressure return passages 143 and 243 are opened by the switching valves 140 and 240, the fuel pressure in the delivery pipe 30 is regulated by the low pressure regulators 144 and 244, and the second predetermined pressure is set. Maintained at pressure Pl.

  Further, as shown in FIG. 9, the high pressure return passage 341 for returning the fuel in the delivery pipe 30 to the fuel tank 10 and the fuel pressure in the high passage return 341 provided in the high pressure return passage 341 are changed to the first predetermined pressure Ph. The high pressure regulator 342 that opens at the above time, the low pressure return passage 343 and the intermediate pressure return passage 345 formed by branching from the main passage 320, the intermediate pressure return passage 345 and the first predetermined pressure Ph are provided. An intermediate pressure regulator 346 that opens when the pressure is equal to or higher than a second predetermined pressure Pm set lower than the second predetermined pressure Pm, and a third pressure set lower than the second predetermined pressure Pm. A low pressure regulator 344 that opens when the pressure is equal to or higher than a predetermined pressure Pl, and a first that switches between opening and closing of the low pressure return passage 343. It is also possible to employ a Kawaben 340a, a configuration and a second switching valve 340b for switching between closed and open medium pressure return passage 345. In this case, the set fuel pressure FP is switched to three stages of the first predetermined pressure Ph, the second predetermined pressure Pm, and the third predetermined pressure Pl by switching the switching valves 340a and 340b according to the engine operating state. be able to.

  In each of the above embodiments, after calculating the discharge amount Flow of the fuel pump 11, an example is shown in which processing is performed to supply an air amount GA corresponding to the discharge amount Flow to the combustion chamber 52. After appropriately calculating the discharge amount Flow of the pump 11, it is possible to arbitrarily change the process to be executed based on the calculated discharge amount Flow. That is, according to the discharge amount Flow of the fuel pump 11 thus grasped, the fuel pressure P in the delivery pipe 30 and the fuel supply amount by the fuel injection valve 31 can be appropriately controlled. Even in this case, the operational effects shown in the above (1) can be achieved.

  In each of the above embodiments, the present invention is applied to a port injection type internal combustion engine that injects fuel into the intake port of the internal combustion engine. However, the fuel in the fuel tank is connected to the delivery pipe to which the fuel injection valve is connected through the main passage. The present invention may be applied to an in-cylinder injection internal combustion engine that directly injects fuel into a cylinder as long as the engine includes an electric fuel pump that pumps the fuel.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram which shows the control apparatus of the internal combustion engine concerning 1st Embodiment which actualized this invention with the periphery structure. The flowchart which shows the process sequence about the process performed by the electronic control apparatus of the embodiment. The graph which shows the relationship between the setting fuel pressure and discharge efficiency in the same embodiment. The graph which shows the relationship between the battery voltage and discharge amount in the same embodiment. The graph which shows the relationship between the alcohol concentration in the same embodiment, and the amount of restricted air. The flowchart which shows the process sequence about the process performed by the electronic control apparatus of 2nd Embodiment. The schematic block diagram shown about the modification of the fuel pressure switching means concerning this invention. The schematic block diagram shown about the other modification of the fuel pressure switching means concerning this invention. The schematic block diagram shown about the other modification of the fuel pressure switching means concerning this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Fuel tank, 11 ... Fuel pump, 12 ... Filter, 13 ... Battery, 20, 120, 220, 320 ... Main passage, 30 ... Delivery pipe, 31 ... Fuel injection valve, 40, 140, 240, 340a, 340b ... Switching valve, 41, 141, 241, 341 ... high pressure return passage, 42, 142, 242, 342 ... high pressure regulator, 43, 143, 243, 343 ... low pressure return passage, 44, 144, 244, 344 ... low pressure regulator, 50 DESCRIPTION OF SYMBOLS Internal combustion engine 51 ... Cylinder 52 ... Combustion chamber 53 ... Piston 54 ... Spark plug 60 ... Intake passage 60a ... Intake port 61 ... Throttle valve 62 ... Throttle valve actuator 63 ... Throttle opening sensor 70 ... Exhaust passage, 71 ... Exhaust gas purification catalyst, 72 ... Air-fuel ratio sensor, 80 ... Electronic control device , 81 ... Voltage sensor (applied voltage detection means), 82 ... Accelerator position sensor, 83 ... Alcohol concentration sensor (alcohol concentration detection means), 84 ... Crank angle sensor, 85 ... Intake air temperature sensor, 86 ... Atmospheric pressure sensor, 345 ... Intermediate pressure return passage, 346, medium pressure regulator.

Claims (5)

An electric fuel pump that pumps fuel in a fuel tank through a main passage to a delivery pipe connected to a fuel injection valve that supplies fuel to the internal combustion engine, and a set fuel pressure of the delivery pipe according to the operating state of the engine A control unit for an internal combustion engine, wherein a fuel supply amount is controlled by controlling a valve opening period of the fuel injection valve corresponding to the set fuel pressure switched by the fuel pressure switching unit. In the device
Applied voltage detecting means for detecting an applied voltage to the fuel pump;
A discharge efficiency determining means for determining that the fuel discharge efficiency by the fuel pump is lower as the set fuel pressure switched by the fuel pressure switching means is higher;
A discharge amount calculating means for calculating a discharge amount of the fuel pump based on the applied voltage detected by the applied voltage detecting means and the discharge efficiency determined by the discharge efficiency determining means. Control device. The control apparatus for an internal combustion engine according to claim 1,
The fuel pressure switching means is provided in the high pressure return passage for returning the fuel in the delivery pipe to the fuel tank, and opened when the fuel pressure in the passage is equal to or higher than a first predetermined pressure. A high-pressure regulator that discharges fuel to the fuel tank side, a low-pressure return passage that is branched from the main passage and returns the fuel in the main passage to the fuel tank, and is provided in the low-pressure return passage. A low pressure regulator that opens when the fuel pressure in the passage is equal to or higher than a second predetermined pressure lower than the first predetermined pressure, and discharges fuel to the fuel tank; and opening and closing of the low pressure return passage And a switching valve that switches between the two according to the operating state of the engine. The control device for an internal combustion engine according to claim 1 or 2,
A required air amount calculating means for calculating a required air amount of the engine;
Limit air amount calculation means for calculating the maximum air amount allowed to be supplied to the engine based on the discharge amount ascertained by the discharge amount calculation means;
An air amount control means for supplying the engine with a smaller air amount of the required air amount calculated by the required air amount calculating means and the restricted air amount calculated by the restricted air amount calculating means. A control device for an internal combustion engine characterized by the above. The control apparatus for an internal combustion engine according to claim 3,
The engine is an engine that can use a mixed fuel in which alcohol and gasoline are arbitrarily mixed, and includes an alcohol concentration detection unit that detects an alcohol concentration of the mixed fuel stored in the fuel tank,
The control device for an internal combustion engine, wherein the limit air amount calculation means calculates the limit air amount as the alcohol concentration detected by the alcohol concentration detection means increases. The control apparatus for an internal combustion engine according to any one of claims 1 to 4,
The control device for an internal combustion engine, wherein the fuel injection valve is a fuel injection valve for port injection that injects fuel into an intake port of the engine.

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