JP2009156154A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the deterioration of combustion and improve drivability by securing appropriate air density according to a change of fuel pressure in a control device for an internal combustion engine. <P>SOLUTION: An ECU 71 corrects a throttle valve 33 in a close direction by an electronic throttle device 34 to reduce the density of air flowing in a combustion chamber 18 while keeping a fuel injection quantity and an air quantity constant when fuel pressure in the delivery pipe 46 is raised to a predetermined designated value, and corrects the throttle valve 33 in an open direction by the electronic throttle device 34 to raise the density of air flowing into the combustion chamber 18 while keeping the fuel injection quantity and the air quantity constant when fuel pressure is raised from the designated value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that estimates a required torque in accordance with an accelerator operation amount and can control opening and closing of a throttle opening.

  In a general internal combustion engine, a throttle opening is set according to an accelerator pedal operation amount (accelerator opening) depressed by a driver, and an air weight (hereinafter referred to as an air amount) corresponding to the throttle opening is set. While being introduced into the combustion chamber, an injection weight (hereinafter referred to as an injection amount) is set based on the intake air amount, and a predetermined amount of fuel is injected from the injector into the combustion chamber. In this case, the control device calculates the driver's required driving torque based on the accelerator opening, and sets the throttle opening based on this required driving torque. However, since the air density varies depending on the atmospheric pressure and the intake air temperature, the atmospheric pressure and the intake air temperature are usually detected, and the throttle opening is corrected based on the atmospheric pressure and the intake air temperature.

  By the way, in a direct injection type internal combustion engine that directly injects fuel into a combustion chamber, it is known that the efficiency of air charging into the combustion chamber increases due to the latent heat of vaporization effect at a constant throttle opening. Further, it is known that when the fuel pressure rises, atomization of the fuel spray is promoted and the air filling efficiency increases. Therefore, since the air filling efficiency increases as the fuel pressure increases, it can be considered that the throttle opening is corrected in a direction that decreases as the fuel pressure increases.

  In addition, there exists a thing described in the following patent document 1 as such a control apparatus of an internal combustion engine. In the control apparatus for an internal combustion engine described in Patent Document 1, the electronic control unit determines that the required energization time of the fuel injection valve corresponding to the required fuel injection amount according to the operating state of the engine is the operation of the fuel injection valve. The required energization time is limited when the fuel pressure from the high-pressure fuel pump to the fuel injection valve is higher than the required fuel pressure according to the operating state of the engine. Sometimes, the throttle valve is driven to the open side to increase the intake air amount in accordance with the increase in the fuel injection amount caused by the restriction.

JP 2005-337201 A

  However, if correction is made so that the throttle opening decreases in accordance with the increase in fuel pressure, the throttle opening (intake air amount) becomes insufficient above the predetermined fuel pressure, the drive torque decreases, and drivability deteriorates. End up. That is, when the fuel pressure is higher than the predetermined pressure, the fuel injection time of the injector is shortened, the area where the fuel spray cannot be sufficiently diffused and contacted with the air is reduced, the vaporization latent heat effect is lowered, and the air filling efficiency is reduced. As a result, the combustion efficiency decreases. When the fuel pressure is higher than the predetermined pressure, the fuel injection speed of the injector is increased, the temperature of the fuel spray collides with the bore wall surface, the temperature rises, the latent heat of vaporization deprived from the air decreases, and the combustion efficiency of the air decreases. .

  The present invention is intended to solve such a problem, and an internal combustion engine that improves drivability by suppressing deterioration of combustion by ensuring an appropriate air density in accordance with fluctuations in fuel pressure. An object of the present invention is to provide a control device.

  In order to solve the above-described problems and achieve the object, a control device for an internal combustion engine according to the present invention includes a fuel injection unit that injects a fuel injection amount corresponding to a required torque into a combustion chamber, and an air amount corresponding to the required torque. Air supply means for supplying fuel to the combustion chamber, fuel pressure detection means for detecting fuel pressure by the fuel injection means, and air density adjustment means for adjusting the density of air flowing into the combustion chamber. When the fuel pressure increases from a predetermined value, while the fuel density increases and the air density flowing into the combustion chamber decreases by the air density adjusting means, while the fuel pressure increases from a predetermined value. The air density flowing into the combustion chamber is increased by the air density adjusting means while keeping the fuel injection amount and the air amount constant.

  In the control apparatus for an internal combustion engine according to the present invention, when the fuel pressure is a predetermined value, the adjustment amount for decreasing the air density flowing into the combustion chamber by the air density adjusting means is set to a maximum value. Yes.

  In the control device for an internal combustion engine of the present invention, the air density adjusting means is a throttle valve provided in an intake system, and corrects the throttle valve in the closing direction when the fuel pressure rises to a predetermined value, while When the pressure rises from a predetermined value, the throttle valve is corrected in the opening direction.

  In the control apparatus for an internal combustion engine of the present invention, the air density adjusting means is an intake variable valve mechanism provided in an intake system, and corrects the closing timing of the intake valve according to the fuel pressure.

  According to the control apparatus for an internal combustion engine of the present invention, when the fuel pressure rises to a predetermined value set in advance, the fuel injection amount and the air amount are made constant, the air density flowing into the combustion chamber is reduced, while the fuel pressure is reduced. When rising from a predetermined value, the fuel injection amount and the air amount are kept constant, and the density of air flowing into the combustion chamber is increased. Therefore, the deterioration of combustion can be suppressed by ensuring an appropriate air density according to the fluctuation of the fuel pressure, and as a result, drivability can be improved.

  Embodiments of an internal combustion engine control apparatus according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this Example.

  FIG. 1 is a schematic configuration diagram illustrating a control device for an internal combustion engine according to a first embodiment of the present invention, FIG. 2 is a schematic configuration diagram illustrating a fuel system in the control device for the internal combustion engine according to the first embodiment, and FIG. FIG. 4 is a correction map showing a throttle opening correction amount with respect to the fuel pressure, FIG. 5 is an air density corresponding to a change in fuel pressure, FIG. 4 is a flowchart showing correction control of the throttle opening by the control device for the internal combustion engine of Example 1. It is explanatory drawing showing a vaporization latent heat effect, a surge tank density, and a throttle opening.

  In the control apparatus for an internal combustion engine according to the first embodiment, as shown in FIG. 1, a cylinder head 12 is fastened on a cylinder block 11, and pistons 14 are vertically moved to a plurality of cylinder bores 13 formed in the cylinder block 11. Fits freely. A crankcase 15 is fastened to the lower part of the cylinder block 11, and a crankshaft 16 is rotatably supported in the crankcase 15. Each piston 14 is connected to the crankshaft 16 via a connecting rod 17. Has been.

  The combustion chamber 18 is constituted by the wall surface of the cylinder bore 13 in the cylinder block 11, the lower surface of the cylinder head 12, and the top surface of the piston 14, and the combustion chamber 18 has a high central portion at the upper portion (lower surface of the cylinder head 12). It has a pent roof shape that is slanted. An intake port 19 and an exhaust port 20 are formed on the upper portion of the combustion chamber 18, that is, the lower surface of the cylinder head 12, and the intake valve 19 and the exhaust valve 20 are opposed to the intake port 19 and the exhaust port 20. The lower end portions of 22 are respectively positioned. The intake valve 21 and the exhaust valve 22 are supported by the cylinder head 12 so as to be movable in the axial direction, and are urged and supported in a direction (upward in FIG. 1) for closing the intake port 19 and the exhaust port 20. ing. An intake cam shaft 23 and an exhaust cam shaft 24 are rotatably supported on the cylinder head 12, and the intake cam and the exhaust cam are in contact with upper ends of the intake valve 21 and the exhaust valve 22.

  Although not shown, the crankshaft sprocket fixed to the crankshaft 16 and the camshaft sprockets respectively fixed to the intake camshaft 23 and the exhaust camshaft 24 are wound with endless timing chains. The crankshaft 16, the intake camshaft 23, and the exhaust camshaft 24 can be interlocked.

  Accordingly, when the intake camshaft 23 and the exhaust camshaft 24 rotate in synchronization with the crankshaft 16, the intake cam and the exhaust cam move up and down the intake valve 21 and the exhaust valve 22 at a predetermined timing. The exhaust port 20 can be opened and closed to allow the intake port 19 and the combustion chamber 18 to communicate with the combustion chamber 18 and the exhaust port 20. In this case, the intake camshaft 23 and the exhaust camshaft 24 are set to rotate once (360 degrees) while the crankshaft 16 rotates twice (720 degrees). Therefore, the engine performs four strokes of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke while the crankshaft 16 rotates twice. At this time, the intake camshaft 23 and the exhaust camshaft 24 rotate once. Will be.

  The valve mechanism of the engine is a variable intake valve timing mechanism (VVT: Variable Valve Timing-intelligent) 25 that controls the intake valve 21 and the exhaust valve 22 at an optimal opening / closing timing according to the operating state. The intake variable valve mechanism 25 is configured by providing a VVT controller 26 at the shaft end of the intake camshaft 23, and the hydraulic pressure from the oil control valve 27 is supplied to an advance chamber and a retard chamber (not shown) of the VVT controller 26. By acting on this, the phase of the intake camshaft 23 with respect to the cam sprocket can be changed, and the opening / closing timing of the intake valve 21 can be advanced or retarded. In this case, the intake variable valve mechanism 25 advances or retards the opening / closing timing while keeping the operating angle (opening period) of the intake valve 21 constant. The intake camshaft 23 is provided with a cam position sensor 28 for detecting the rotational phase.

  A surge tank 30 is connected to the intake port 19 via an intake manifold 29, and an intake pipe 31 is connected to the surge tank 30. An air cleaner 32 is attached to an air intake port of the intake pipe 31. . An electronic throttle device 34 having a throttle valve 33 is provided on the downstream side of the air cleaner 32. The intake port 19 is provided with a bypass passage 35 that bypasses the throttle valve 33, and an idle speed control valve 36 is provided in the bypass passage 35.

  An exhaust pipe 38 is connected to the exhaust port 20 via an exhaust manifold 37, and the exhaust pipe 38 has a three-way catalyst 39 for purifying harmful substances contained in the exhaust gas and a NOx occlusion reduction type catalyst 40. Is installed. The three-way catalyst 39 simultaneously purifies HC, CO, and NOx contained in the exhaust gas by an oxidation-reduction reaction when the air-fuel ratio (exhaust air-fuel ratio) is stoichiometric. The NOx occlusion reduction type catalyst 40 is in a rich combustion region or stoichiometric combustion region where the NOx contained in the exhaust gas is temporarily stored when the air-fuel ratio (exhaust air-fuel ratio) is lean, and the oxygen concentration in the exhaust gas is reduced. Sometimes, the stored NOx is released and NOx is reduced by the added fuel as a reducing agent.

  An exhaust gas recirculation passage (EGR passage) 41 is provided between the downstream side of the surge tank 30 in the intake pipe 31 and the upstream side of the three-way catalyst 39 in the exhaust pipe 38. Are provided with an EGR valve 42 and an EGR cooler 43. Further, an EGR gas temperature sensor 44 that detects the temperature of the EGR gas is provided on the intake pipe 31 side of the EGR passage 41 from the EGR valve 42.

  The cylinder head 12 is provided with an injector 45 that directly injects fuel into the combustion chamber 18. The injector 45 is positioned on the intake port 19 side and is inclined at a predetermined angle downward from the horizontal upper end. . An injector 45 attached to each cylinder is connected to a delivery pipe 46, and a high pressure fuel pump 48 is connected to the delivery pipe 46 via a high pressure fuel supply pipe 47. The high pressure fuel pump 48 is supplied with a low pressure fuel supply. A low-pressure fuel pump (feed pump) 51 in the fuel tank 50 is connected via a pipe 49. Accordingly, the low-pressure fuel pump 51 pressurizes the fuel in the fuel tank 50 to a predetermined low pressure and supplies it to the low-pressure fuel supply pipe 49, and the high-pressure fuel pump 48 supplies the low-pressure fuel in the low-pressure fuel supply pipe 49 to a predetermined high pressure. The fuel can be pressurized and supplied to the delivery pipe 46 via the high-pressure fuel supply pipe 47, and the injector 45 can inject the high-pressure fuel in the delivery pipe 46 into the combustion chamber 18. The cylinder head 12 is provided with a spark plug 52 that is positioned above the combustion chamber 18 and ignites the air-fuel mixture.

  A canister 53 is provided in the fuel tank 50, and the canister 53 is connected to the upstream side of the surge tank 30 in the intake pipe 31 through a purge passage 54. A purge valve 55 is provided in the purge passage 54. The canister 53 adsorbs purge gas including vapor (evaporated fuel) generated in the fuel tank 50, and opens the purge valve 55 to discharge the adsorbed purge gas to the intake pipe 31 through the purge passage 54. be able to.

  Here, the fuel system of the internal combustion engine described above will be described in detail. In the fuel system of the internal combustion engine of the first embodiment, as shown in FIG. 2, an injector 45 and a spark plug 52 are provided for the combustion chamber 18 provided corresponding to four cylinders. Each injector 45 is connected to the delivery pipe 46 at the base end, and can inject the high-pressure fuel in the delivery pipe 46 into the combustion chamber 18.

  The fuel tank 50 has a vertical shape divided into a first chamber 50a and a second chamber 50b, and a predetermined amount of gasoline fuel (hereinafter referred to as fuel) can be stored in each chamber 50a, 50b. A low-pressure feed pump 51 is mounted in the first chamber 50a. The low-pressure feed pump 51 is connected to a high-pressure fuel pump 48 via a low-pressure fuel supply pipe 49. The high-pressure fuel pump 48 is connected to a high-pressure fuel supply pipe 47. It is connected to one end portion of the delivery pipe 46 via. The high pressure fuel pump 48 can be driven by the intake camshaft 23, a pulsation damper 56 is attached to the low pressure fuel supply pipe 49, and a check valve 57 is attached to the high pressure fuel supply pipe 47.

  A jet pump 58 is provided in the second chamber 50b. A fuel return pipe 60 having a pressure regulator 59 branched from the low-pressure fuel supply pipe 49 is connected to the jet pump 58, and the first pump 58 is connected to the first chamber 50b. A fuel transfer pipe 61 extending to the chamber 50a is connected. Further, the other end portion of the delivery pipe 46 is connected to the base end portion of the fuel discharge pipe 62, and a relief valve 63 is attached to the discharge portion of the delivery pipe 46 in the fuel discharge pipe 62. The leading end of 62 is connected to the second chamber 50 b in the fuel tank 50.

  Therefore, when the internal combustion engine is started, the low pressure feed pump 51 is driven to increase the pressure of the fuel in the first chamber 50a in the fuel tank 50, and the low pressure fuel is supplied to the high pressure fuel pump 48 through the low pressure fuel supply pipe 49. The pump 48 can increase the pressure of the low-pressure fuel and supply the high-pressure fuel to the delivery pipe 46 through the high-pressure fuel supply pipe 47. The injector 45 can inject the high-pressure fuel in the delivery pipe 46 into the combustion chamber 18. When the fuel pressure in the delivery pipe 46 becomes greater than a predetermined pressure, the relief valve 63 is opened and high pressure fuel is discharged through the fuel discharge pipe 62 to the second chamber 50b in the fuel tank 50.

  The high-pressure fuel pump 48 described above can be driven by a pump cam 23 a fixed to the intake camshaft 23. That is, when the intake camshaft 23 rotates and the plunger 64 descends by the pump cam 23a, the low-pressure fuel in the low-pressure fuel supply pipe 49 is sucked, and then when the plunger 64 rises, at a timing according to the required discharge amount. When the metering valve 66 is raised by the electromagnetic solenoid 65 and the suction port with the low-pressure fuel supply pipe 49 is closed, the low-pressure fuel is boosted and the high-pressure fuel boosted to a predetermined pressure is passed from the discharge port through the check valve 57. It can be pumped to the high-pressure fuel supply pipe 47. In this case, when the plunger 64 is raised, the timing of raising the metering valve 66 by the electromagnetic solenoid 65 can be adjusted to adjust the discharge amount to the delivery pipe 46 and the fuel pressure of the delivery pipe 46 is adjusted. be able to.

  The vehicle is equipped with an electronic control unit (ECU) 71, which can control the fuel injection timing of the injector 45, the ignition timing of the spark plug 52, the throttle opening of the electronic throttle device 34, and the like. Various controls are executed on the basis of engine operating conditions such as the detected intake air amount, intake air temperature, throttle opening, accelerator opening, engine speed, and cooling water temperature.

  That is, an air flow sensor 72 and an intake air temperature sensor 73 are mounted on the upstream side of the intake pipe 31, and the measured intake air amount and intake air temperature are output to the ECU 71. The electronic throttle device 34 is provided with a throttle position sensor 74, and the accelerator pedal is provided with an accelerator position sensor 75, which outputs the current throttle opening and accelerator opening to the ECU 71. The crankshaft 16 is provided with a crank angle sensor 76 and outputs the detected crank angle to the ECU 71. The ECU 71 discriminates an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke in each cylinder based on the crank angle, and an engine. Calculate the number of revolutions. The cylinder block 11 is provided with a water temperature sensor 77 and outputs the detected engine cooling water temperature to the ECU 71. The cylinder block 11 is provided with a knock sensor 78 and outputs a detected knocking signal to the ECU 71. The vehicle is provided with an atmospheric pressure sensor 79 and outputs the detected atmospheric pressure to the ECU 71. Further, the delivery pipe 46 communicating with each injector 45 is provided with a fuel pressure sensor 80 that detects the fuel pressure, and outputs the detected fuel pressure to the ECU 71.

An air-fuel ratio (A / F) sensor 81 is provided upstream of the three-way catalyst 39 in the exhaust pipe 38, and an oxygen (O ₂ ) sensor 82 is provided downstream of the three-way catalyst 39. The A / F sensor 81 and the O ₂ sensor 82 detect the exhaust air-fuel ratio (oxygen amount) of the exhaust gas exhausted from the combustion chamber 18 through the exhaust port 20 and the exhaust manifold 37 to the exhaust pipe 38, and the detected exhaust air is detected. The fuel ratio is output to the ECU 71. The ECU 71 feeds back the exhaust air-fuel ratio detected by the A / F sensor 81 and the O ₂ sensor 82 and compares it with the target air-fuel ratio set according to the engine operating state, thereby correcting the learning of the fuel injection amount. .

  Therefore, in the fuel injection control by the ECU 71, the required fuel injection pressure (fuel pressure) is set based on the engine operating state such as the engine speed, load (intake air amount, etc.) rate, engine cooling water temperature, and the like. The high-pressure fuel pump 48 is driven and controlled so that the fuel pressure detected by the fuel pressure sensor 80 matches the fuel pressure detected by the fuel pressure sensor 80. Further, the fuel injection amount and the fuel injection timing are set based on the engine operating state such as the intake air amount, intake air temperature, throttle opening, accelerator opening, engine speed, and cooling water temperature detected by various sensors. In this case, the target air-fuel ratio is set according to the fuel properties, and the fuel injection amount is set so as to be the target air-fuel ratio. The ECU 71 controls the injector 45 to inject predetermined use fuel into the combustion chamber 18 at a predetermined pressure at a predetermined fuel injection timing.

  Further, in the ignition timing control by the ECU 71, an ignition timing map is set according to the engine operating state such as the engine speed and the intake air amount detected by various sensors, and the ECU 71 controls the ignition plug 52 for driving. Thus, ignition can be performed at a predetermined ignition timing. At this time, the ECU 71 performs advance angle correction or delay angle correction at the time of ignition based on the knocking signal detected by the knock sensor 78.

  Further, in the throttle control by the ECU 71, the required throttle opening is set based on the detected accelerator opening and the engine operating state, and the required throttle opening and the throttle opening detected by the throttle position sensor 74 coincide with each other. The electronic throttle device 34 is driven and controlled.

  The ECU 71 can control the intake variable valve mechanism 25 based on the engine operating state. That is, when the temperature is low, the engine is started, the engine is idle, or the load is light, the exhaust gas blows back into the intake port 19 or the combustion chamber 18 by eliminating the overlap between the exhaust valve 22 closing timing and the intake valve 21 opening timing. Reduce the amount to enable stable combustion and improved fuel efficiency. Further, at the time of medium load, by increasing the overlap, the internal EGR rate is increased to improve the exhaust gas purification efficiency, and the pumping loss is reduced to improve the fuel consumption. Further, at the time of high-load low-medium rotation, the closing timing of the intake valve 21 is advanced, thereby reducing the amount of intake air that blows back to the intake port 19 and improving the volume efficiency. At the time of high load and high rotation, the closing timing of the intake valve 21 is retarded in accordance with the rotation speed, so that the timing is adjusted to the inertial force of the intake air and the volume efficiency is improved.

  By the way, when the fuel injection pressure by the injector 45, that is, the fuel pressure in the delivery pipe 46 rises, atomization of the fuel spray in the combustion chamber 18 is promoted, and the air filling efficiency increases due to the vaporization latent heat effect. Therefore, it is desirable to correct in the direction to decrease the throttle opening according to the increase in fuel pressure. However, when the fuel pressure is higher than the predetermined pressure, the fuel injection time of the injector 45 is shortened, the fuel spray cannot be sufficiently diffused, the area in contact with air is reduced, and the combustion efficiency is lowered. Further, when the fuel pressure becomes higher than the predetermined pressure, the fuel injection speed of the injector increases, the fuel spray collides with the bore wall surface, the temperature rises, and the combustion efficiency decreases.

  Therefore, in the control apparatus for the internal combustion engine of the first embodiment, the injector 45 as fuel injection means for injecting the fuel injection amount corresponding to the required torque into the combustion chamber 18 and the air amount corresponding to the required torque are supplied to the combustion chamber 18. An electronic throttle device 34 is provided as an air supply means for adjusting the air density and an air density adjusting means for adjusting the density of air flowing into the combustion chamber 18, and a fuel pressure sensor 80 is provided as a fuel pressure detection means for detecting a fuel injection pressure (fuel pressure) by the injector 45. When the fuel pressure rises to a predetermined value set in advance, the ECU 71 reduces the density of air flowing into the combustion chamber 18 by the electronic throttle device 34 while keeping the fuel injection amount and the air amount constant, while the fuel pressure is a predetermined value. The air-tight air flowing into the combustion chamber 18 by the electronic throttle device 34 with the fuel injection amount and the air amount being constant when rising from It is to raise the.

  That is, when the fuel pressure is a predetermined value set in advance, the ECU 71 sets the adjustment amount for reducing the density of air flowing into the combustion chamber 18 by the electronic throttle device 34 to the maximum value. Here, the ECU 71 corrects the throttle valve 33 in the closing direction by the electronic throttle device 34 when the fuel pressure increases to a predetermined value, and corrects the throttle valve 33 in the opening direction when the fuel pressure increases from the predetermined value. Like to do.

  Here, the throttle opening correction control by the control apparatus for the internal combustion engine of the first embodiment will be described based on the flowchart of FIG.

  In the throttle opening correction control by the control apparatus for the internal combustion engine according to the first embodiment, as shown in FIG. 3, in step S11, the ECU 71 sets a target request based on the accelerator opening detected by the accelerator position sensor 75. The throttle opening TH is calculated. In step S12, the ECU 71 reads the fuel pressure PF of the delivery pipe 46 detected by the fuel pressure sensor 80. In step S13, the ECU 71 calculates the throttle opening correction amount KTHPF from the fuel pressure PF using the throttle correction map. .

As shown in FIG. 4, this throttle correction map is a correction map representing the throttle opening correction amount with respect to the fuel pressure, and the throttle opening correction amount in the direction in which the throttle valve 33 is closed as the fuel pressure PF increases. When KTHPF increases, the throttle opening correction amount KTHPF becomes the maximum correction amount KTHPFmax at the predetermined fuel pressure PF ₀ , and when the fuel pressure PF further increases, the throttle opening correction amount KTHPF in the direction to close the throttle valve 33 decreases. It has become a thing.

  In step S13, the ECU 71 calculates the throttle opening correction amount KTHPF from the throttle correction map using the fuel pressure PF. In step S14, the ECU 71 adds the throttle opening correction amount KTHPF (to the throttle opening TH calculated in step S11. The throttle opening TH is corrected by adding a negative value. In step S <b> 15, the ECU 71 executes throttle operation control using the electronic throttle device 34.

Here, the throttle opening correction control will be described in detail. As shown in FIGS. 1 and 5, when the fuel pressure (fuel pressure) of the delivery pipe 46 is low and the fuel pressure is low, the injector 45 causes the fuel with low fuel pressure to flow. Even if it is injected into the combustion chamber 18, the effect of latent heat of vaporization in the combustion chamber 18 is small and the air density is low. Therefore, in order to obtain a predetermined air weight, the throttle opening is increased (opened), Increase air density. When the pressure (fuel pressure) of the fuel in the delivery pipe 46 rises to the intermediate fuel pressure (predetermined fuel pressure PF ₀ ), the injector 45 injects fuel at the intermediate fuel pressure into the combustion chamber 18. Since the effect is increased and the air density is increased, the predetermined air weight can be obtained, so that the throttle opening is decreased (closed), and the air density of the surge tank 30 is decreased. Furthermore, when the fuel pressure (fuel pressure) in the delivery pipe 46 rises from the medium fuel pressure (predetermined fuel pressure PF ₀ ) to a high fuel pressure, the injector 45 injects fuel with a high fuel pressure into the combustion chamber 18. Therefore, in order to obtain a predetermined air weight, the throttle opening is increased (opened), and the air density of the surge tank 30 is increased. Therefore, the fuel injection weight and the air weight can be controlled to be constant regardless of the change in the fuel pressure, and a desired torque required by the driver can be ensured.

  As described above, in the control apparatus for the internal combustion engine of the first embodiment, the ECU 71 sets the fuel injection amount and the air amount to be constant when the fuel pressure in the delivery pipe 46 rises to a predetermined value. The device 34 corrects the throttle valve 33 in the closing direction to reduce the density of air flowing into the combustion chamber 18. On the other hand, when the fuel pressure rises from a predetermined value, the fuel injection amount and the air amount are kept constant by the electronic throttle device 34. The throttle valve 33 is corrected in the opening direction to increase the density of air flowing into the combustion chamber 18.

  Therefore, when the fuel pressure rises to a predetermined fuel pressure, the injector 45 injects high-pressure fuel into the combustion chamber 18, so that the effect of latent heat of vaporization in the combustion chamber 18 increases and the air density increases. In order to maintain the weight, the throttle valve 33 is operated to the closed side, the throttle opening is reduced, and the air density of the surge tank 30 is reduced. When the fuel pressure further rises from the predetermined fuel pressure, the injector 45 injects high fuel pressure fuel into the combustion chamber 18, but if the fuel pressure is too high, the fuel injection time is shortened and the fuel spray can be sufficiently diffused. In addition, the fuel injection speed is increased, the fuel spray temperature is increased, and the combustion efficiency is decreased. That is, since the effect of latent heat of vaporization in the combustion chamber 18 is reduced and the air density is reduced, the throttle valve 33 is operated on the open side to secure a predetermined air weight, the throttle opening is increased, and the surge tank Increase the air density of 30. Therefore, by ensuring an appropriate air density regardless of fluctuations in the fuel pressure, the fuel injection weight and the air weight can be controlled constantly at a constant level, the desired torque required by the driver can be ensured, and the high Accurate air-fuel ratio control becomes possible, and deterioration of combustion can be suppressed. As a result, drivability can be improved.

In this case, in the control device for the internal combustion engine of the first embodiment, when the fuel pressure is the predetermined fuel pressure PF ₀ , the throttle opening correction amount KTHPF is set to the maximum correction amount KTHPFmax. That is, the throttle correction map of FIG. 4 varies depending on the shape of the combustion chamber 18, the fuel properties, the performance of the high-pressure fuel pump 48, and the like, and the throttle opening maximum correction amount KTHPFmax increases or decreases depending on the above-described parameters. The predetermined fuel pressure PF ₀ that becomes the throttle opening maximum correction amount KTHPFmax also varies.

  In the control apparatus for an internal combustion engine of the first embodiment, the air density adjusting means of the present invention is the electronic throttle device 34 (throttle valve 33), and when the fuel pressure rises to a predetermined fuel pressure, the throttle valve 33 is corrected in the closing direction. On the other hand, when the fuel pressure rises from the predetermined fuel pressure, the throttle valve 33 is corrected in the opening direction. Therefore, the air density can be easily adjusted by an existing device, and the device can be simplified and easily controlled.

  FIG. 6 is an explanatory diagram showing air density, vaporization latent heat effect, surge tank density, intake valve closing timing according to fuel pressure fluctuations by the control device for an internal combustion engine according to Embodiment 2 of the present invention, and FIG. It is a graph showing the closing timing and intake air volume of an intake valve by a variable valve mechanism. The overall configuration of the control apparatus for an internal combustion engine of the present embodiment is substantially the same as that of the first embodiment described above, and will be described with reference to FIG. 1 and members having the same functions as those described in this embodiment. Are denoted by the same reference numerals, and redundant description is omitted.

  In the control apparatus for an internal combustion engine according to the second embodiment, as shown in FIG. 1, an injector 45 as fuel injection means for injecting a fuel injection amount corresponding to the required torque into the combustion chamber 18 and an air amount corresponding to the required torque are burned. As an air supply means for supplying air to the chamber 18 and an air density adjusting means for adjusting the density of air flowing into the combustion chamber 18, a variable intake valve mechanism 25 and a fuel pressure detecting means for detecting the fuel injection pressure (fuel pressure) by the injector 45 As the fuel pressure sensor 80 is provided, the ECU 71 reduces the volume of air flowing into the combustion chamber 18 by the intake variable valve mechanism 25 while keeping the fuel injection amount and the air amount constant when the fuel pressure rises to a predetermined value set in advance. On the other hand, when the fuel pressure rises from a predetermined value, the fuel injection amount and the air amount are made constant, and flow into the combustion chamber 18 by the intake variable valve mechanism 25. So that to increase the air volume.

  That is, when the fuel pressure is a predetermined value that is set in advance, the ECU 71 sets the adjustment amount for reducing the volume of air flowing into the combustion chamber 18 by the intake variable valve mechanism 25 to the maximum value. Here, the ECU 71 corrects the closing timing of the intake valve 21 by the variable intake valve mechanism 25 according to the fuel pressure. In this embodiment, the intake variable valve mechanism 25 performs control to advance or retard the closing timing of the intake valve 21. In this case, there are two effects. That is, as shown in FIG. 7, the intake air volume is reduced by closing the intake valve 21 during intake and by opening the intake valve 21 even after the piston 14 is lifted (hereinafter referred to as an effect A). Called). Further, if the closing timing of the intake valve 21 is delayed, a large amount of air can be taken into the combustion chamber 18 due to the inertia supercharging effect (hereinafter referred to as “effect B”). When the intake valve 21 closing timing C has the largest effect A + B of the intake air volume with respect to the actual closing timing of the intake valve 21 in which the effects A and B are combined, the operating range of the closing timing of the intake valve 21 is the air valve. When the angle is advanced from the closing timing C of 21, the control A in FIG. 6 is used, and when the angle is retarded, the intake control in FIG. 6 is used.

That is, as shown in FIGS. 1 and 6, when the fuel pressure (fuel pressure) of the delivery pipe 46 is low and the fuel pressure is low, even if the injector 45 injects fuel with a low fuel pressure into the combustion chamber 18, Therefore, in control A, the closing timing of the intake valve 33 is retarded, and in control B, the closing timing of the intake valve 33 is advanced to increase the intake air volume. Let When the pressure (fuel pressure) of the fuel in the delivery pipe 46 rises to the intermediate fuel pressure (predetermined fuel pressure PF ₀ ), the injector 45 injects fuel at the intermediate fuel pressure into the combustion chamber 18. Since the effect is increased and the air density is increased, in control A, the closing timing of the intake valve 33 is advanced, and in control B, the closing timing of the intake valve 33 is delayed to reduce the intake air volume. Furthermore, when the fuel pressure (fuel pressure) in the delivery pipe 46 rises from the medium fuel pressure (predetermined fuel pressure PF ₀ ) to a high fuel pressure, the injector 45 injects fuel with a high fuel pressure into the combustion chamber 18. In the control A, the closing timing of the intake valve 33 is retarded, and in the control B, the closing timing of the intake valve 33 is advanced to reduce the intake air volume. increase.

  Thus, in the control device for the internal combustion engine of the second embodiment, the ECU 71 allows the intake air with the fuel injection amount and the air amount to be constant when the fuel pressure in the delivery pipe 46 rises to a predetermined value set in advance. While the density of air flowing into the combustion chamber 18 is reduced by the variable valve mechanism 25, when the fuel pressure rises from a predetermined value, the fuel injection amount and the air amount are kept constant and the intake variable valve mechanism 25 flows into the combustion chamber 18. The air density is increased.

  Therefore, when the fuel pressure further rises from the predetermined fuel pressure, the injector 45 injects fuel with a high fuel pressure into the combustion chamber 18, but if the fuel pressure is too high, the fuel injection time is shortened and the fuel spray can be sufficiently diffused. In addition, the fuel injection speed is increased, the fuel spray temperature is increased, and the combustion efficiency is decreased. That is, the effect of latent heat of vaporization in the combustion chamber 18 is reduced and the air density is reduced. Therefore, in order to secure a predetermined air weight, the intake valve closing timing is corrected by the intake variable valve mechanism 25, and the surge tank 30 Increase the air density. Therefore, by ensuring an appropriate air density regardless of fluctuations in the fuel pressure, the fuel injection weight and the air weight can be controlled constantly at a constant level, the desired torque required by the driver can be ensured, and the high Accurate air-fuel ratio control becomes possible, and deterioration of combustion can be suppressed. As a result, drivability can be improved.

  As described above, the control device for an internal combustion engine according to the present invention is intended to improve the drivability by suppressing the deterioration of combustion by securing an appropriate air density according to the fluctuation of the fuel pressure. It is also useful for internal combustion engines.

1 is a schematic configuration diagram illustrating a control device for an internal combustion engine according to Embodiment 1 of the present invention. 1 is a schematic configuration diagram illustrating a fuel system in a control device for an internal combustion engine according to a first embodiment. 3 is a flowchart illustrating a throttle opening correction control performed by the internal combustion engine control apparatus according to the first embodiment. It is a correction map showing the throttle opening correction amount with respect to fuel pressure. It is explanatory drawing showing the air density according to the fluctuation | variation of fuel pressure, the vaporization latent heat effect, the surge tank density, and the throttle opening. It is explanatory drawing showing the air density according to the fuel pressure fluctuation | variation by the control apparatus of the internal combustion engine which concerns on Example 2 of this invention, a vaporization latent heat effect, a surge tank density, and an intake valve closing time. It is a graph showing the closing timing and intake air volume of an intake valve by an intake variable valve mechanism.

Explanation of symbols

18 Combustion chamber 19 Intake port 20 Exhaust port 25 Intake variable valve mechanism (air supply means, air density adjustment means)
30 Surge tank 31 Intake pipe 33 Throttle valve 34 Electronic throttle device (air supply means, air density adjustment means)
38 Exhaust pipe 45 Injector (fuel injection means)
46 Delivery pipe 52 Spark plug 71 Electronic control unit, ECU
72 Airflow sensor 74 Throttle position sensor 75 Accelerator position sensor 76 Crank angle sensor 77 Water temperature sensor 80 Fuel pressure sensor (fuel pressure detection means)

Claims (4)

Fuel injection means for injecting a fuel injection amount corresponding to the required torque into the combustion chamber;
Air supply means for supplying an amount of air corresponding to the required torque to the combustion chamber;
Fuel pressure detection means for detecting fuel pressure by the fuel injection means;
An air density adjusting means for adjusting the air density flowing into the combustion chamber,
When the fuel pressure rises to a predetermined value set in advance, the fuel injection amount and the air amount are made constant, the air density adjusting means lowers the air density flowing into the combustion chamber, while the fuel pressure rises from the predetermined value When the fuel injection amount and the air amount are constant, the air density adjusting means increases the air density flowing into the combustion chamber.
A control device for an internal combustion engine.   2. The internal combustion engine according to claim 1, wherein when the fuel pressure is a predetermined value set in advance, the adjustment amount for decreasing the air density flowing into the combustion chamber by the air density adjusting means is set to a maximum value. Control device.   The air density adjusting means is a throttle valve provided in the intake system, and corrects the throttle valve in the closing direction when the fuel pressure rises to a predetermined value, while when the fuel pressure rises from the predetermined value, 3. The control device for an internal combustion engine according to claim 1, wherein the throttle valve is corrected in the opening direction.   3. The internal combustion engine according to claim 1, wherein the air density adjusting unit is a variable intake valve operating mechanism provided in an intake system, and corrects the closing timing of the intake valve in accordance with fuel pressure. Control device.

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