JP2008169819A - Output control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an output control device of an internal combustion engine, which improves response of a supercharger at the time of low or medium revolution and high load, and suppresses exhaust of HC. <P>SOLUTION: The output control device is provided with: the supercharger 35 for obtaining rotation energy by exhaust exhausted from an engine 1; valve gears 50, 51 for driving and opening and closing a suction valve 7a and an exhaust valve 7b respectively; variable valve timing mechanisms 8a, 8b capable of varying valve overlap amounts of the suction valve and exhaust valve; and a control means 30 for determining an operation state of the engine, and controlling to operate the variable valve timing mechanisms in a direction for reducing the valve overlap amount after operating the variable valve timing mechanisms in a direction for increasing the valve overlap amount when the determined operation state is in an operation area of the low and medium revolution and the high load, which is a predetermined operation area. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an output control device for an internal combustion engine provided with a supercharger.

  Some engines that are internal combustion engines include a turbocharger as a supercharger in order to improve the output. A turbocharger is a supercharger that rotates a compressor with exhaust energy to rotate a compressor disposed on the intake side to compress the intake air.

  By the way, unburned HC exists in the exhaust gas discharged from the internal combustion engine, but most of it is included at the time of cold start. As a countermeasure, a variable valve timing mechanism that can vary the valve overlap amount between the intake valve and the exhaust valve is provided, and the valve overlap amount (open / close timing) is appropriately controlled to reduce unburned HC.

  In recent years, an internal combustion engine having both a turbocharger and a variable valve timing mechanism has been proposed. As a known document of this type of internal combustion engine, for example, Patent Document 1 can be cited. This patent document 1 discloses a technique in which the opening / closing timing of the exhaust valve is fixed in a high load region and the intake valve is retarded so that the effective compression ratio becomes smaller than the expansion ratio. And according to such control, it is supposed that an internal EGR rate can be reduced and knocking can be prevented.

JP 2006-97653 A

  In an internal combustion engine equipped with a turbocharger and a variable valve timing mechanism, because of the characteristics of the turbocharger, even if the driver depresses the accelerator pedal and enters a high-load operation region when the engine is running at low and medium speeds, the turbine is less exhausted. There is a problem that there is little energy to rotate and the response does not increase.

Therefore, it is conceivable that the valve overlap amount is widened and the intake air is blown out to the exhaust system, and the intake fuel is combusted by the compressor to increase the supercharging pressure and use it for the rotational energy of the turbine. However, if the valve overlap amount is simply increased, unburned HC blows through the exhaust system, and even if the torque increases, a large amount of HC is contained in the exhaust. For this reason, in an internal combustion engine equipped with a turbocharger and a variable valve timing mechanism, appropriate matching between the two is desired.
Here, as in Patent Document 1 described above, it is possible to achieve matching by adjusting the valve overlap amount by fixing the opening / closing timing of the exhaust valve and retarding the intake valve. However, it can be said that such valve timing adjustment is unsuitable for control because the amount of torque change with respect to the phase is large.

  The present invention provides an output control device for an internal combustion engine that can suppress HC emissions while improving the response of a supercharger at low to medium speed and high load.

  In order to achieve the above object, a first aspect of the present invention provides a supercharger that obtains rotational energy by exhaust exhausted from an internal combustion engine, a valve mechanism that opens and closes an intake valve and an exhaust valve, an intake valve, and an exhaust valve. A variable valve timing mechanism that can vary the valve overlap amount of the valve, an operation state determination unit that determines the operation state of the internal combustion engine, and the valve overlap amount when the operation state determination unit determines a predetermined operation state And a control means for operating the variable valve timing mechanism in the direction of reducing the valve overlap amount after the variable valve timing mechanism is operated in the direction.

  According to a second aspect of the present invention, in the output control device for an internal combustion engine according to the first aspect, the control means operates the variable valve timing mechanism so as to retard the opening / closing timing of the intake valve and advances the opening / closing timing of the exhaust valve. The variable valve timing mechanism is actuated so as to make the angle, and the valve overlap amount is widened.

  According to a third aspect of the present invention, in the output control device for an internal combustion engine according to the first or second aspect, the control means operates the variable valve timing mechanism so as to fix the opening / closing timing of the intake valve, and sets the opening / closing timing of the exhaust valve. The variable valve timing mechanism is operated so as to advance the valve, and the valve overlap amount is narrowed.

  According to a fourth aspect of the present invention, in the output control device for an internal combustion engine according to any one of the first to third aspects, the operating state detecting means includes a rotational speed detecting means for detecting the rotational speed of the internal combustion engine, and an internal combustion engine. A load state detecting means for detecting a load state, wherein the rotational speed detecting means detects a low / medium rotation, and when the load state detecting means detects a high load state, it is determined as a predetermined operating state. It is said.

  According to the present invention, when the operating state of the internal combustion engine is a predetermined operating state, first, the variable valve timing mechanism is operated in a direction to increase the valve overlap amount, whereby the intake air taken into the combustion chamber from the intake valve is reduced. Since it blows through the exhaust system through the exhaust valve and is combusted in the supercharger, the supercharging pressure rises and the response is improved. In addition, by increasing the valve overlap amount and then operating the variable valve timing mechanism in a direction that reduces the valve overlap amount, the intake air that blows from the intake valve to the exhaust system via the exhaust valve is reduced. Emission can be reduced.

  According to the present invention, when the valve overlap amount is increased, the variable valve timing of the intake valve is retarded, so that a large amount of intake air is blown through the exhaust system. As a result, the torque can be improved more efficiently than in the case where the variable valve timing of the exhaust valve is retarded to increase the valve overlap amount, leading to an improved response.

  According to the present invention, when the valve overlap amount is narrowed, the opening / closing timing of the intake valve is fixed, and the variable valve timing of the exhaust valve is advanced, thereby delaying the variable valve timing of the intake valve. Torque reduction can be suppressed as compared with the case where the overlap amount is narrowed, leading to an improvement in response.

  According to the present invention, the operating state detecting means includes the rotational speed detecting means for detecting the rotational speed of the internal combustion engine and the load state detecting means for detecting the load state of the internal combustion engine, and the rotational speed detecting means is in the low / medium speed. When the load state detection means detects a high load state, it is determined that the vehicle is in a predetermined operation state. Therefore, the HC discharge is improved while improving the response of the supercharger at low to medium rotation and high load. Can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, the code | symbol 1 shows the engine as an internal combustion engine which has an output control apparatus. The engine 1 is configured as an intake passage injection type engine, and a DOHC 4-valve type is adopted as the valve operating mechanism. A cylinder head 2 is mounted on an upper portion of a cylinder 2a constituting the engine 1. The intake-side valve mechanism 50 is a well-known intake camshaft 22 formed with an intake cam 3a that abuts the upper end of the intake valve 7a via a rocker arm (not shown) and a known biasing force of the intake valve 7a in the valve closing direction. And a valve spring (not shown). The exhaust-side valve mechanism 51 is a well-known exhaust camshaft 22 formed with an exhaust cam 3b that comes into contact with the upper end of the exhaust valve 7b via a rocker arm (not shown) and urges the exhaust valve 7b in the valve closing direction. And a valve spring (not shown).

  In these valve operating mechanisms 50 and 51, timing pulleys 4a and 4b are connected to front ends of the intake camshaft 21 and the exhaust camshaft 22, respectively. These timing pulleys 4 a and 4 b are connected to a crankshaft 6 of the engine 1 via a timing belt 5. The timing pulleys 4a and 4b and the camshafts 21 and 22 are rotationally driven as the crankshaft 6 rotates, and the intake valves 7a and the exhaust valves 7b are opened and closed by these camshafts 21 and 22.

  Between each of the camshafts 21 and 22 and the timing pulleys 4a and 4b, a vane type timing variable mechanism (hereinafter referred to as "intake side VVT" or "exhaust side VVT") as a variable valve timing mechanism on the intake side and exhaust side. 8a and 8b are provided. The configurations of the intake side VVT 8a and the exhaust side VVT 8b are well known in, for example, Japanese Patent Application Laid-Open No. 2000-27609, and will not be described in detail, but a vane rotor is rotatably provided in a housing provided in the timing pulleys 4a and 4b. The intake camshaft 21 or the camshaft 22 is connected to the vane rotor. Oil control valves (hereinafter referred to as OCV) 9a and 9b are connected to the intake side VVT 8a and the exhaust side VVT 8b, respectively.

  The VVTs 8a and 8b use hydraulic oil supplied from the oil pump 10 of the engine 1 to apply hydraulic pressure to the vane rotor in accordance with the switching of the OCVs 9a and 9b. As a result, the camshaft 21 to the timing pulleys 4a and 4b 22, the opening / closing timing of the intake valve 7a and the exhaust valve 7b is adjusted.

  In the engine 1, an intake passage 12 is connected to an intake port 11 provided in the cylinder head 2 and opened and closed by an intake valve 7a. Intake air is introduced into the intake passage 12 as the piston 16 reciprocates up and down in the cylinder 2a in FIG. The intake air is mixed with fuel injected from a fuel injection valve 15 as fuel injection means after the flow rate is adjusted according to the opening of a throttle valve 14 provided in the intake passage 12, and the intake valve 11 passes through an intake port 11. It flows into the cylinder when the valve 7a is opened.

  On the other hand, an exhaust passage 18 is connected to an exhaust port 17 provided in the cylinder head 2 and opened and closed by an exhaust valve 7b. The exhaust gas after being ignited and burned in the cylinder by the spark plug 19 is guided from the exhaust port 17 to the exhaust passage 18 as the piston 16 rises when the exhaust valve 7b is opened, and is provided on the exhaust passage 18. The catalyst 20 and a silencer (not shown) are discharged to the outside.

  The engine 1 is equipped with a turbocharge (supercharger) 35 that obtains rotational energy by exhaust discharged from the combustion chamber 40. The turbocharge 35 includes a turbine 36 that is provided in the exhaust passage 18 and is rotated by exhaust gas, and a compressor 37 that is provided coaxially with the turbine 36 and is disposed in a return passage 38 connected to the intake passage 12. An air cleaner 13 is disposed upstream of the compressor 37. For this reason, when the exhaust gas is guided from the exhaust port 17 to the exhaust passage 18, the turbine 36 rotates, and by this rotation, the compressor 37 rotates and the intake air is supercharged and taken into the combustion chamber 40. An intercooler 39 is arranged between the reflux path 38 and the exhaust path 12.

  In the vehicle interior, an input / output device (not shown), a storage device (ROM, RAM, etc.) used for storing control programs, control maps, etc., a central processing unit (CPU), an ECU as a control means provided with a timer counter, etc. An (engine control unit) 30 is installed and performs overall control of the engine 1. On the input side of the ECU 30, an air flow sensor 31 as an intake air amount detecting means for detecting an intake air amount, a rotational speed sensor 32 as a rotational speed detecting means for detecting an engine rotational speed Ne, and an opening degree of an accelerator pedal are detected. Various sensors such as an accelerator opening sensor 33, a throttle sensor 34 as a load state detecting means for detecting an opening TPS of the throttle valve 14 serving as an engine load, and a timer (not shown) are connected. OCVs 9a and 9b, a fuel injection valve 15, a spark plug 19 and the like are connected to the output side of the ECU 30. In this embodiment, the fuel injection valve 15 is driven at a timing at which fuel is injected in the exhaust process. In this embodiment, the operating state detecting means is composed of a rotation speed sensor 32 and a throttle sensor 34.

  The ECU 30 determines the ignition timing, the fuel injection amount, and the like based on detection information from each sensor, and controls the driving of the spark plug 19 and the fuel injection valve 15. Each map shown in FIGS. 2 to 5 is set in the ECU 30 in advance. The map shown in FIG. 2 is based on the charging efficiency acquired from the engine rotational speed Ne from the rotational speed sensor 32 and the intake air amount obtained from the airflow sensor 31, and the basic phase angle (overlap amount) of the timing variable mechanisms 8a and 8b. ). The map shown in FIG. 3 is for calculating the required charging efficiency from the engine speed Ne and the accelerator opening detected by the accelerator opening sensor 33. The map shown in FIG. 4 is for determining a region where the basic phase angle (overlap amount) is widened from the engine speed Ne and the charging efficiency. The map in FIG. 5 is used to determine whether or not the required charging efficiency is obtained from the engine speed Ne and the charging efficiency. Further, the ECU 30 stores a predetermined value for determining the engine speed and a predetermined value for determining the required charging efficiency.

  In the present embodiment, the ECU 30 sets the OCV 9a in the direction of widening the basic phase angle (overlap amount) when the operation state of the engine 1 detected by each sensor is a low / medium rotation / high load operation region where the operation state is a predetermined operation state. Operate to correct the basic phase angle (overlap amount) and at the required filling efficiency, operate the OCV 9b in a direction to narrow the widened phase angle (overlap amount) to correct the phase angle (overlap amount). Execute control.

  Here, the relationship between the valve overlap (VOL) amount by the intake side VVT 8a and the exhaust side VVT 8b, the engine torque, and the unburned HC will be described with reference to FIGS. FIG. 6A shows engine torque fluctuations when the valve overlap (VOL) amount is changed by operating the intake side VVT 8a and the exhaust side VVT 8b individually to change the phases of the intake valve and the exhaust valve. FIG. 6B shows the exhaust gas when the valve overlap (VOL) amount is changed by individually operating the intake side VVT 8a and the exhaust side VVT 8b to change the phases of the intake valve and the exhaust valve. It is a figure which shows the discharge amount change of inside HC. These characteristics are based on test data measured by the inventor of the present invention by individually operating the intake side VVT 8a and the exhaust side VVT 8b.

  6 (a) and 6 (b), the line connecting ● indicates the characteristics when the intake side VVT 8a is operated to change the intake phase, and the line connecting ▲ is the exhaust side VVT 8b operated to change the exhaust phase. The characteristics are shown. FIG. 7 is a diagram showing the operation of the intake side VVT 8a and the exhaust side VVT 8b and the change in the valve overlap (VOL) amount.

  FIG. 6 shows that when the valve overlap (VOL) is large, that is, when the valve overlap is large, the engine torque is high and the HC emission amount is increased. Further, if the valve overlap (VOL) is the same, it is understood that when the exhaust intake phase is made smaller than the intake phase, that is, the exhaust phase is made narrower, the decrease in engine torque is smaller and the HC emission amount becomes substantially the same value. .

  From this characteristic, in this embodiment, appropriate control of the valve overlap (VOL) capable of suppressing the discharge of unburned HC while improving the engine torque by adjusting the valve overlap (VOL) is executed. .

  Hereinafter, output control by the ECU 30 will be described based on a flowchart shown in FIG. In step S1 of FIG. 8, the engine speed Ne is acquired, the intake air amount is calculated from the air flow sensor 31 in step S2, and the charging efficiency is acquired from the intake air amount in step S3. In step S4, based on the engine speed Ne and charging efficiency, the basic phase (basic VVT phase) by the intake side VVT 8a and the exhaust side VVT 8b is read from the map of FIG.

  In step S5, the accelerator opening is acquired from the accelerator opening sensor 33. In step S6, the required charging efficiency, that is, the driver's acceleration request is calculated from the map of FIG. 3 based on the engine speed Ne and the accelerator opening.

  In step S7, in order to detect the operating state of the engine 1, it is determined whether or not the engine speed is within a predetermined range (operating region) set in advance. Here, when it is outside the predetermined range, the control is terminated without executing this control, and when it is within the predetermined range, the process proceeds to step S8 assuming that it is the low / medium rotation region. In step S8, it is determined whether or not the required filling efficiency exceeds a predetermined value, and if the required filling efficiency does not exceed the predetermined value, control is performed assuming that the driver does not request torque increase. Finish. However, if the required charging efficiency exceeds the predetermined value, it is determined that torque increase is requested and the process proceeds to step S9.

  In step S9, the enlargement is acquired from the map shown in FIG. 4, added to the basic phase (basic VVT phase) and corrected, and the OCV 9a is operated to enlarge the valve overlap (VOL). Here, when the engine speed is in the range of 1500 rpm to 3000 rpm and the charging efficiency is in the range of 100% to 200%, the phase of the intake side VVT 8a is retarded by 20 degrees to increase the valve overlap (VOL) amount.

  After widening the valve overlap (VOL) amount in this way, in step S10, it is determined whether or not the required charging efficiency has been reached based on the map shown in FIG. 5, and if not, the valve overlap (VOL) amount is determined. When the enlarged state is maintained and the required filling efficiency is reached, the process proceeds to step S11. In step S11, the OCV 9b is operated to advance the phase angle (overlap amount) in the direction of narrowing to the exhaust air side VVT 8b. Here, the basic phase (basic VVT phase) is corrected so that the required torque and the required HC have a phase angle (overlap amount), and this control is finished.

  That is, as shown in FIGS. 5 and 9, after the engine 1 is started (1), when the accelerator opening increases and the required charging efficiency increases (2), the intake side VVT 8a is reached so that the required charging efficiency is reached quickly. Is retarded to widen the valve overlap (VOL), thereby reducing the intake air blown from the intake valve 7a to the exhaust passage 8 through the exhaust valve 7b, thereby reducing the discharge of unburned HC, Since a large amount of intake air is blown into the exhaust passage 18, the torque can be improved more efficiently than in the case where the valve overlap (VOL) amount is increased by retarding the exhaust side VVT 8b, leading to an improved response.

  Further, when the required supercharging pressure is reached (3), the exhaust VVT 8b is advanced to narrow the valve overlap (VOL), so that the intake side VVT 8a is retarded to narrow the valve overlap (VOL). Can also reduce torque reduction, leading to improved response.

  In this embodiment, the charging efficiency is obtained from the intake air amount detected by the air flow sensor 31. However, it is of course possible to obtain the charging efficiency from the throttle opening obtained from the throttle opening sensor 34.

It is a figure which shows schematic structure of the output control apparatus of the internal combustion engine concerning this invention. It is a characteristic map for calculating | requiring a basic phase angle. It is a characteristic map for calculating | requiring required filling efficiency. It is a figure which shows the driving | operation area | region which expands a basic phase angle. It is a map for judging required filling efficiency. It is a characteristic view which shows the relationship between valve overlap, an engine torque, and HC. It is a figure which shows the motion of a valve overlap. It is a flowchart which shows one form of the output control by a control means. It is a model diagram which shows the displacement state of a valve overlap.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 7a Intake valve 8a, 8b Variable valve timing mechanism 7b Exhaust valve 30 Control means 35 Supercharger 50, 51 Valve mechanism

Claims (4)

A supercharger that obtains rotational energy by exhaust discharged from the internal combustion engine;
A valve mechanism for opening and closing the intake valve and the exhaust valve, and
A variable valve timing mechanism capable of varying a valve overlap amount of the intake valve and the exhaust valve;
Operating state determining means for determining the operating state of the internal combustion engine;
When the operation state determination means determines a predetermined operation state, the variable valve timing mechanism is operated in a direction to reduce the valve overlap amount after the variable valve timing mechanism is operated in a direction to increase the valve overlap amount. Control means for controlling to operate
An output control device for an internal combustion engine, comprising: In the internal combustion engine output control device according to claim 1,
The control means operates the variable valve timing mechanism to retard the opening / closing timing of the intake valve and operates the variable valve timing mechanism to advance the opening / closing timing of the exhaust valve, thereby An output control device for an internal combustion engine, characterized in that the wrap amount is widened. The output control apparatus for an internal combustion engine according to claim 1 or 2,
The control means operates the variable valve timing mechanism to fix the opening / closing timing of the intake valve and operates the variable valve timing mechanism to advance the opening / closing timing of the exhaust valve, thereby An output control device for an internal combustion engine, characterized in that the amount is reduced. The output control device for an internal combustion engine according to any one of claims 1 to 3,
The operating state detecting means is
A rotational speed detection means for detecting the rotational speed of the internal combustion engine;
Load state detecting means for detecting a load state of the internal combustion engine,
An output control device for an internal combustion engine, characterized in that when the rotational speed detection means detects low / medium speed and the load state detection means detects a high load state, it is determined as the predetermined operating state.

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