JP2016205172A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine that can accurately generate a target torque even in a highland where atmospheric pressure decreases relative to that in a flat ground.SOLUTION: In the control device for an internal combustion engine, CPU 31 that is an overlap amount target value calculation part of the control device 30 calculates an overlap amount target value between an intake valve 11 and an exhaust valve 12 so that an overlap amount in low atmospheric pressure is larger than that in high atmospheric pressure.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device for an internal combustion engine provided with a variable valve adjustment mechanism that changes valve opening / closing characteristics of an intake valve and / or an exhaust valve of the internal combustion engine.

  As a control method of an internal combustion engine (engine) provided with a variable valve adjustment mechanism, a control method described in Patent Document 1 is known. The control method described in Patent Document 1 below aims to estimate an internal EGR (Exhaust Gas Recirculation) amount with high responsiveness and high accuracy so that various engine controls can be performed satisfactorily. In the following Patent Document 1, the internal EGR amount is estimated based on the closing timing of the exhaust valve, the opening timing of the intake valve, and the engine speed.

JP 2001-221105 A

  By the way, in the case of an engine equipped with a throttle valve and there is a fluctuation in atmospheric pressure, if an attempt is made to obtain the same torque, the opening of the throttle valve is adjusted so that a certain amount of air passes. . However, since the exhaust side is not provided with a mechanism for adjusting the displacement according to the atmospheric pressure fluctuation, the so-called flat sea such as several meters to several tens of meters is so-called several hundred meters to several thousand meters above sea level. At high altitudes, exhaust emissions associated with lower atmospheric pressure tend to be significantly better. As described above, the intake-side condition does not change between the flat ground and the highland, but if the highland is improved with respect to the flatland only by exhaust gas exhaust, the internal EGR rate decreases, and the combustion speed increases. Therefore, at the same ignition timing, the high altitude is relatively advanced from the flat ground, and the generated torque is larger than the target value.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a control device for an internal combustion engine capable of accurately generating a target torque even in a high altitude where the atmospheric pressure falls with respect to a flat ground. May be offered.

  In order to solve the above-described problems, a control device according to the present invention includes an internal combustion engine (1) including a variable valve adjustment mechanism that changes a valve opening / closing characteristic of an intake valve (11) and / or an exhaust valve (12). An engine control device (30) comprising an overlap amount target value calculation unit (31) for calculating an overlap amount target value in which an opening period of the intake valve and an opening period of the exhaust valve overlap, The atmospheric pressure detected by the detection unit (40) includes a high atmospheric pressure and a low atmospheric pressure that is lower than the high atmospheric pressure. The overlap amount target value calculation unit is configured so that the overlap amount is larger at the low atmospheric pressure than at the high atmospheric pressure based on atmospheric pressure information indicating the atmospheric pressure detected by the atmospheric pressure detection unit. Calculate the lap amount target value.

  In the present invention, since the overlap amount target value corresponding to the low atmospheric pressure is larger than the overlap amount target value corresponding to the high atmospheric pressure, the overlap amount target value of the intake valve and the exhaust valve is calculated. The internal EGR rate when the atmospheric pressure is lower than typical setting conditions can be increased. Therefore, it is possible to suppress a decrease in the internal EGR rate due to good exhaust escape when the atmospheric pressure is low, and it is possible to generate a target torque accurately.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the internal combustion engine which can generate | occur | produce a target torque exactly also in the highland where atmospheric pressure falls with respect to a flat ground can be provided.

FIG. 1 is a schematic configuration diagram illustrating a configuration of an ECU that is a control device according to an embodiment of the present invention and a configuration of an internal combustion engine that is a control target. FIG. 2 is a flowchart showing a procedure when the ECU of FIG. 1 executes overlap amount correction. FIG. 3 is a diagram showing a change in internal EGR rate when overlap amount correction is performed in the procedure shown in FIG. FIG. 4 is a diagram illustrating an example of the relationship between the atmospheric pressure and the corrected overlap amount. FIG. 5 is a diagram illustrating an example of the relationship between the atmospheric pressure and the corrected overlap amount. FIG. 6 is a diagram illustrating a change in the valve lift amount when the overlap amount correction is performed. FIG. 7 is a diagram showing the relationship between the ignition timing and the generated torque when the overlap amount correction is performed.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same constituent elements in the drawings will be denoted by the same reference numerals as much as possible, and redundant description will be omitted.

  An ECU (Electronic Control Unit) 30 that is a control device according to an embodiment of the present invention and an engine 1 (an internal combustion engine) that is a control target will be described with reference to FIG. As shown in FIG. 1, the engine 1 is a spark ignition type four-cycle multi-cylinder internal combustion engine, and an intake pipe 2 and an exhaust pipe 3 are connected to an intake port and an exhaust port, respectively.

  The intake pipe 2 is provided with a throttle valve 4 that is linked to an accelerator pedal (not shown) and an air flow meter 5 for detecting the amount of intake air. The opening degree of the throttle valve 4 is detected by a throttle sensor 20. The throttle sensor 20 also detects the fully closed state of the throttle.

  A piston 7 that reciprocates in the vertical direction in the figure is disposed in a cylinder 6 that constitutes a cylinder of the engine 1. The piston 7 is connected to a crankshaft (not shown) via a connecting rod 8.

  A combustion chamber 10 defined by a cylinder 6 and a cylinder head 9 is formed above the piston 7. The combustion chamber 10 communicates with the intake pipe 2 and the exhaust pipe 3 via the intake valve 11 and the exhaust valve 12. The cylinder 6 is provided with a water temperature sensor 17 for detecting the temperature of the engine cooling water.

  Two catalytic converters 13 and 14 are disposed in the exhaust pipe 3. The catalytic converters 13 and 14 are formed of a three-way catalyst for purifying three components such as HC, CO, and NOx in the exhaust gas.

An A / F sensor 15 is provided on the upstream side of the catalytic converter 14. The A / F sensor 15 outputs a wide-range and linear air-fuel ratio signal in proportion to the oxygen concentration in the exhaust gas or the concentration of carbon monoxide in the unburned gas. Further, on the downstream side of the catalytic converter 14, an O ₂ sensor 16 that outputs different voltage signals on the rich side and the lean side with respect to the stoichiometric air-fuel ratio (stoichiometric) is provided.

  The electromagnetically driven injector 18 is supplied with high-pressure fuel from a fuel supply system (not shown), and the injector 18 injects and supplies fuel to the engine intake port when energized. In the present embodiment, a multipoint injection system having one injector 18 for each branch pipe of the intake manifold is configured. A spark plug 19 disposed in the cylinder head 9 is ignited by a high voltage for ignition supplied from an igniter (not shown).

  In this case, fresh air supplied from upstream of the intake pipe and fuel injected by the injector 18 are mixed at the engine intake port, and the mixture flows into the combustion chamber 10 as the intake valve 11 opens. The fuel that has flowed into the combustion chamber 10 is ignited by an ignition spark from the spark plug 19 and is used for combustion.

  An intake side camshaft 21 for opening and closing the intake valve 11 at a predetermined timing and an exhaust side camshaft 22 for opening and closing the exhaust valve 12 at a predetermined timing are connected to the crankshaft via a timing belt (not shown) or the like. Drive coupled. The intake side camshaft 21 is provided with a hydraulically driven intake side VCT (Variable Cam Timing) mechanism 23 (variable valve adjusting mechanism, displacement angle adjusting portion), and the exhaust side camshaft 22 is also provided with a hydraulically driven exhaust side. A VCT mechanism 24 (variable valve adjustment mechanism, displacement angle adjustment unit) is provided. The intake side VCT mechanism 23 and the exhaust side VCT mechanism 24 change valve opening / closing characteristics.

  The intake-side VCT mechanism 23 and the exhaust-side VCT mechanism 24 are phase-adjustable variable valve timing mechanisms for adjusting the relative rotational phases between the intake-side camshaft 21 and the exhaust-side camshaft 22 and the crankshaft, respectively. The operation is adjusted according to hydraulic control by a solenoid valve (not shown). Depending on the control amount of the intake side VCT mechanism 23 and the exhaust side VCT mechanism 24, the intake side camshaft 21 and the exhaust side camshaft 22 rotate to the retard side or the advance side with respect to the crankshaft. At the same time, the opening / closing timing of the intake valve 11 and the exhaust valve 12 shifts to the retard side or the advance side.

  The intake side camshaft 21 is provided with an intake side cam position sensor 25 for detecting the rotational position of the intake side camshaft 21. The exhaust side cam shaft 22 is provided with an exhaust side cam position sensor 26 for detecting the rotational position of the exhaust side cam shaft 22.

The ECU 30 is mainly configured by a microcomputer including a CPU 31 (overlap amount target value calculation unit), a ROM 32, a RAM 33, a backup RAM 34, and the like. The ECU 30 receives detection signals from the air flow meter 5, the A / F sensor 15, the O ₂ sensor 16, the water temperature sensor 17, the throttle sensor 20, the intake side cam position sensor 25, and the exhaust side cam position sensor 26. The The ECU 30 detects engine operating conditions such as the intake air amount Qa, the catalyst upstream and downstream air-fuel ratios (A / F), the engine water temperature Tw, the throttle opening, and the cam position based on each detection signal.

  The ECU 30 is connected to a reference position sensor 27 that outputs a pulse signal every 720 ° CA and a rotation angle sensor 28 that outputs a pulse signal every finer crank angle (for example, every 30 ° CA). . The ECU 30 detects the reference crank position and the engine speed based on each pulse signal.

  An atmospheric pressure sensor 40 (atmospheric pressure detection unit) is connected to the ECU 30. The ECU 30 detects the atmospheric pressure at the point where the vehicle is traveling based on the output signal from the atmospheric pressure sensor 40. The CPU 31 constituting the ECU 30 controls the opening timing and closing timing of the intake valve 11 and the exhaust valve 12 based on atmospheric pressure information and information acquired from other sensors.

  Next, the overlap amount control of the intake valve 11 and the exhaust valve 12 by the ECU 30 will be described with reference to FIG.

  In step S01, atmospheric pressure data of a point where the vehicle is traveling is acquired. Specifically, the atmospheric pressure signal (atmospheric pressure information) detected by the atmospheric pressure sensor 40 is output to the ECU 30. The CPU 31 acquires the current atmospheric pressure from the atmospheric pressure signal.

  In step S02 following step S01, a correction coefficient is set. This correction coefficient is used to reflect an atmospheric pressure fluctuation factor in the overlap amount target value of the intake valve 11 and the exhaust valve 12 set from other conditions.

  For example, the atmospheric pressure (high atmospheric pressure) in a coastal urban area (flat land, 10 m above sea level) is 1013 [hPa], and the atmospheric pressure (low atmospheric pressure) on a mountain road (1000 m above sea level) is 899 [hPa]. ]. In this case, the correction coefficient is determined so that the overlap amount target value in the case of the low atmospheric pressure is larger than the overlap amount target value in the case of the high atmospheric pressure. For example, the correction amount for the overlap target value at the reference atmospheric pressure is calculated based on the atmospheric pressure difference between the atmospheric pressure indicated by the atmospheric pressure signal as the atmospheric pressure information detected by the atmospheric pressure sensor 40 and a predetermined reference atmospheric pressure. By determining, a correction coefficient corresponding to the correction amount is determined, and an overlap target value when atmospheric pressure information is detected is calculated.

  As shown in FIG. 4, the correction coefficient may be set so that the atmospheric pressure and the corrected overlap amount maintain a substantially proportional relationship. Further, as shown in FIG. 5, the atmospheric pressure and the corrected overlap amount may be set so as to maintain a stepped relationship.

  The step-like relationship is a relationship in which the correction coefficient takes the same value and the corrected overlap amount keeps the same value with respect to a certain range of atmospheric pressure. As a method of determining the correction coefficient, a table corresponding to the atmospheric pressure value is stored in the ROM 32, and may be determined based on the table, or may have a threshold at a point where the corrected overlap amount is changed.

  In step S03 following step S02, a corrected overlap amount target value is calculated. In calculating the corrected overlap amount target value, the overlap amount of the intake valve 11 and the exhaust valve 12 set from other conditions is multiplied by the correction coefficient obtained in step S02.

  In step S04 following step S03, the corrected maximum overlap amount is calculated. The maximum overlap amount is a limit value of the overlap amount of the intake valve 11 and the exhaust valve 12 for continuing combustion. Similar to the overlap amount, the maximum overlap amount obtained from other conditions is multiplied by the correction coefficient calculated in step S02 to calculate the corrected maximum overlap amount.

  In step S05 following step S04, it is determined whether or not the corrected overlap amount target value obtained in step S03 is smaller than a value (limit value) indicating the corrected maximum overlap amount obtained in step S04. If the corrected overlap amount target value is smaller than the value indicating the corrected maximum overlap amount, the process proceeds to step S06, where the corrected overlap amount target value is greater than the value indicating the corrected maximum overlap amount. If not, the process proceeds to step S07.

  In step S06, a VCT target displacement angle corresponding to the corrected overlap amount target value is set. The VCT target displacement angle is a target value corresponding to the target advance amount of the intake valve 11 and / or the target retard amount of the exhaust valve 12. As shown in FIG. 6, when the exhaust side is retarded and the intake side is advanced, the overlap amount of the intake valve 11 and the exhaust valve 12 is set. In FIG. 6, the exhaust side retard angle and the intake side advance angle are executed simultaneously, but only one of them can be moved to set the overlap amount.

  When the overlap amount target value is corrected and set in this manner, the state shown in FIG. 3 is obtained. FIG. 3A shows the fluctuation of the internal EGR rate when the overlap amount is not corrected. As shown in FIG. 3A, if the overlap amount target value is not corrected, the internal EGR rate decreases at high altitude.

  FIG. 3B shows the fluctuation of the internal EGR rate when the overlap amount target value is corrected. As shown in FIG. 3B, when correction for increasing the overlap amount target value is performed, it is possible to suppress a decrease in the internal EGR rate.

  In step S07, a VCT target displacement angle corresponding to the corrected maximum overlap amount is set. Even if it does not reach the optimum correction value, by setting the VCT target displacement angle corresponding to the corrected maximum overlap amount, it is possible to ensure the continuation of combustion while suppressing the decrease in the internal EGR rate.

  As described with reference to FIG. 3, the internal EGR rate decreases at high altitude unless the overlap amount target value is corrected. When the internal EGR rate decreases, the combustion speed increases, and as shown in FIG. 7A, the ignition is relatively advanced with respect to the same ignition timing as compared to the flat ground. There is a case where the torque becomes excessive due to the ignition on the relatively advanced side.

  When the internal EGR rate is increased by correcting the overlap amount target value and the internal EGR is made equal between the flat land and the highland, the in-cylinder fresh air amount becomes equal. When the in-cylinder fresh air amount becomes equal, the in-cylinder combustion state becomes equivalent, and the torque characteristics for the same ignition timing become equivalent as shown in FIG. In the present embodiment, the in-cylinder combustion state is kept equal regardless of the atmospheric pressure variation as described above, so that the torque sensitivity with respect to the ignition timing does not change. Therefore, drivability can be improved. Further, for example, an event such as an unexpected advance of the vehicle due to an excessive creep phenomenon during idling can be avoided.

1: Engine (internal combustion engine)
11: Intake valve 12: Exhaust valve 30: ECU (control device)
31: CPU (overlap amount target value calculation unit)
40: Atmospheric pressure sensor (atmospheric pressure detector)
23: Intake side VCT mechanism (variable valve adjustment mechanism, displacement angle adjustment unit)
24: Exhaust side VCT mechanism (variable valve adjustment mechanism, displacement angle adjustment unit)

Claims (4)

A control device (30) for an internal combustion engine comprising a variable valve adjustment mechanism for changing a valve opening / closing characteristic of an intake valve (11) and / or an exhaust valve (12) of the internal combustion engine (1),
An overlap amount target value calculation unit (31) for calculating an overlap amount target value in which an opening period of the intake valve and an opening period of the exhaust valve overlap;
The atmospheric pressure detected by the atmospheric pressure detector (40) includes a high atmospheric pressure and a low atmospheric pressure lower than the high atmospheric pressure,
The overlap amount target value calculation unit is configured to increase the overlap amount at the low atmospheric pressure from the high atmospheric pressure based on atmospheric pressure information indicating the atmospheric pressure detected by the atmospheric pressure detection unit. A control device for an internal combustion engine, characterized in that a target amount is calculated.   The overlap amount target value calculation unit determines a correction amount for the overlap amount target value at the reference atmospheric pressure based on an atmospheric pressure difference between the atmospheric pressure indicated by the atmospheric pressure information and a predetermined reference atmospheric pressure. The control device for the internal combustion engine according to claim 1, wherein an overlap amount target value at the time of detecting the atmospheric pressure information is calculated. The variable valve adjustment mechanism includes a displacement angle adjustment unit (23, 24) that adjusts the advance amount of the intake valve and / or the retard amount of the exhaust valve based on the overlap amount target value.
The said displacement angle adjustment part increases the advance amount of the said intake valve and / or the retard amount of the said exhaust valve according to the said overlap amount target value, The Claim 1 or 2 characterized by the above-mentioned. Control device for internal combustion engine. Corresponding to the operating state of the internal combustion engine, a maximum overlap amount is defined which is a limit value where an opening period of the intake valve and an opening period of the exhaust valve overlap,
The internal combustion engine according to claim 1, wherein the overlap amount target value calculation unit limits a maximum overlap amount corresponding to the low atmospheric pressure so that the overlap amount target value does not exceed. Engine control device.

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