JP2015042853A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the performance exerted by an internal combustion engine by sufficiently mixing two fluids used in the internal combustion engine.SOLUTION: A control device controls an internal combustion engine which is equipped with a first fluid flow passage and a second fluid flow passage joining with the first flow passage. The control device, when opening a valve provided in the second flow passage to mix the fluid flowing in the flow passage with the fluid flowing in the first flow passage, executes high-speed opening and closing operation of operating the valve to an opening deviated from a target opening of the same and then quickly returning the valve to the target opening.

Description

  The present invention relates to a control device that controls an internal combustion engine mounted on a vehicle or the like. In particular, the present invention relates to a control device for an internal combustion engine attached with an EGR (Exhaust Gas Recirculation) device.

While lowering the combustion temperature of the mixture in the cylinders of the internal combustion engine to reduce emissions of NO _x, a EGR device known to reduce the pumping loss (e.g., see Patent Document). The EGR device connects an exhaust passage and an intake passage of an internal combustion engine via an EGR passage, and recirculates a part of combustion gas generated in the cylinder to the intake passage via the EGR passage and mixes it with fresh air. .

JP 2012-241575 A

  When EGR is performed, depending on the ratio (EGR rate) of EGR gas in the air-fuel mixture filled in the cylinder, the ignition and combustion of the air-fuel mixture may become unstable, leading to misfire. In particular, if the fresh air and the EGR gas are not sufficiently mixed and there is local unevenness in the concentration of the EGR gas in the air-fuel mixture, the risk of combustion instability or misfire increases.

In order to reliably prevent misfire, it is necessary to provide an upper limit with a large safety margin added to the EGR rate. However, by that amount, so that the original utility that improved of the NO _x emission reduction and fuel efficiency of the offset.

  In addition to EGR, in an internal combustion engine, a process of mixing two fluids is performed. For example, in the crank chamber of an internal combustion engine, combustion gas and unburned gas leaked from the combustion chamber of the cylinder accumulate as blow-by gas. The blow-by gas in the crank chamber is discharged into the intake passage through a PCV passage that connects the crank chamber and the intake passage, and is filled into the cylinder as a part of the intake air, and finally recombusted in the combustion chamber. Even in this case, the problem of uneven mixing of fresh air and blow-by gas may occur.

  The present invention made in view of the above is intended to enhance the performance exhibited by the internal combustion engine by sufficiently mixing two fluids handled by the internal combustion engine.

  In the present invention, an internal combustion engine including a first fluid flow path and a second fluid flow path that merges with the first flow path is controlled and provided in the second flow path. When the fluid flowing through the flow passage is mixed with the fluid flowing through the first flow passage by opening the valve, the target is opened immediately after the valve is operated to an opening deviating from the target opening. A control device for an internal combustion engine is provided, which performs a high-speed opening / closing operation to return to normal.

  If the first flow passage is an intake passage that is a fresh air flow passage and the second flow passage is an EGR passage that is a flow passage for EGR gas, then an EGR that is a valve provided on the EGR passage. When performing EGR in which the valve is opened and EGR gas is mixed with fresh air, a high-speed opening / closing operation for quickly returning to the target opening after operating the EGR valve to an opening deviating from the target opening, At least once each time the intake stroke comes in, the operation is executed.

  According to the present invention, it is possible to sufficiently mix the two fluids handled by the internal combustion engine and improve the performance exhibited by the internal combustion engine.

The figure which shows schematic structure of the internal combustion engine in one Embodiment of this invention. The timing diagram which shows the pattern of the control which the control apparatus of the embodiment performs. The timing diagram which shows one of the modifications of this invention.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. The internal combustion engine in the present embodiment is a spark ignition type four-stroke engine and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes spark discharge between the center electrode and the ground electrode. The ignition coil is integrally incorporated in a coil case together with an igniter that is a semiconductor switching element.

  The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

  The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  An external EGR device 2 is attached to the internal combustion engine of the present embodiment. The external EGR device 2 realizes a so-called high-pressure loop EGR. The EGR device 21 communicates the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3, and the EGR passage 21. The EGR cooler 22 provided in the EGR passage and the EGR valve 23 that opens and closes the EGR passage 21 and controls the flow rate of the EGR gas flowing through the EGR passage 21 are used as elements.

  The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined location downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3, specifically to a surge tank 33. Therefore, the EGR gas to be distributed to all the cylinders 1 once flows into the surge tank 33 and then travels to each cylinder 1 via the intake manifold 34.

  The EGR cooler 22 is a heat exchanger that lowers the temperature of the EGR gas by exchanging high heat of the EGR gas that circulates through the EGR passage 21 with cooling water (coolant) of the internal combustion engine.

  The blow-by gas recirculation device 6 is for sending blow-by gas generated in the inner chambers 7 and 8 of the internal combustion engine to the intake passage 3, and includes the PCV passage 61, the PCV valve 62, and the blow-by passage 63 as elements. .

  One end of the PCV passage 61 is connected to the crank chamber 7, and the other end is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3, specifically, to the surge tank 33, and the crank chamber 7 is connected to the intake passage. Communicate to 3. Blow-by gas in the crank chamber 7 is discharged to the intake passage 3 via the PCV passage 61.

  A PCV valve 62 provided on the PCV passage 61 increases or decreases the flow rate of blow-by gas flowing through the PCV passage 61. In the present embodiment, the PCV valve 62 is disposed at or near the connection point of the PCV passage 61 to the crank chamber 7.

  An oil separator (not shown) is interposed between the crank chamber 7 and the PCV valve 62. The oil separator has a labyrinth structure and performs a gas-liquid separation action for separating the lubricating oil contained in the flowing gas from the gas, and prevents the lubricating oil from being lost from the crank chamber 7.

  One end of the blow-by passage 63 is connected to the cam chamber 8 in the cylinder head cover of the internal combustion engine, and the other end is connected to a predetermined location upstream of the throttle valve 32 in the intake passage 3, and the cam chamber 8 is connected to the intake passage 3. Communicate with. An oil separator is also provided at a location where the blow-by passage 63 is connected to the cam chamber 8.

  When the PCV valve 62 is open, blow-by gas in the cam chamber 8 and the crank chamber 7 is sent out to the intake passage 3 via the PCV valve 62 and the PCV passage 61. At the same time, fresh air flows into the cam chamber 8 and the crank chamber 7 from the intake passage 3 via the blow-by passage 63, and the cam chamber 8 and the crank chamber 7 are ventilated. The blow-by gas returned to the surge tank 33 in the intake passage 3 is filled in the cylinder 1 and recombusted.

  An ECU (Electronic Control Unit) 0 that is a control device for an internal combustion engine is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and depression of an accelerator pedal. The accelerator opening signal c output from a sensor that detects the amount or the opening of the throttle valve 32 as an accelerator opening (so-called required load), the intake air charged in the cylinder 1 (particularly in the surge tank 33) From an intake air temperature / intake pressure signal d output from a temperature / pressure sensor that detects temperature and pressure, from an outside air temperature signal e output from an air temperature sensor that detects the temperature of outside air, from a water temperature sensor that detects a cooling water temperature of the internal combustion engine From the output coolant temperature signal f and the sensor (or shift position switch) to know the range of the shift lever Shift range signal g is the force, the cam angle signal h or the like to be output from the cam angle sensor is input in a plurality of cam angle of the intake camshaft or an exhaust camshaft.

  From the output interface, the ignition signal i for the igniter of the spark plug 12, the fuel injection signal j for the injector 11, the opening operation signal k for the throttle valve 32, and the opening operation signal l for the EGR valve 23. , An opening operation signal m or the like is output to the PCV valve 62.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed, the intake air amount, etc., the required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR rate) Various operating parameters such as volume). The ECU 0 applies various control signals i, j, k, l and m corresponding to the operation parameters via the output interface.

  Based on the current engine speed and accelerator opening (required load), that is, the operating range of the internal combustion engine, the ECU 0 sets an EGR rate at which the air-fuel mixture can be burned without misfiring as the required EGR rate. The required EGR rate is greatest in a region where the required load is medium, and decreases as the required load decreases from the region, and decreases as the required load increases from the region. In an extremely high load operation region and an extremely low load operation region (including during idling), the required EGR rate is 0 (EGR is not performed). In the memory of the ECU 0, map data that defines the relationship between the engine speed and the accelerator opening and the required EGR rate is stored in advance. The ECU 0 searches the map using the current engine speed and the accelerator opening as keys to know the required EGR rate to be set.

  Then, the EGR valve 23 is caused to follow a target opening degree that achieves the above-described required EGR rate. At this time, the ECU 0 of the present embodiment sets the EGR valve 23 to the target opening as shown in FIG. After operating to an opening deviating from the opening, a high-speed opening / closing operation for quickly returning to the target opening is executed. In FIG. 2, the thin broken line represents the target opening of the EGR valve 23, and the thick solid line represents the actual opening of the EGR valve 23 operated by the ECU 0. Due to the high-speed opening / closing operation, the transition of the actual opening degree of the EGR valve 23 appears to vibrate up and down around the target opening degree.

  As a result of the high-speed opening / closing operation, pulsation occurs in the EGR gas flowing through the EGR passage 21 toward the surge tank 33, and when this EGR gas and fresh air flowing through the intake passage 3 are mixed, the dynamic pressure of the EGR gas Fresh air comes into the low part of. Therefore, mixing of fresh air and EGR gas is promoted, and the air-fuel mixture filled in the cylinder 1 is made uniform. That is, local unevenness does not occur in the concentration of the EGR gas in the air-fuel mixture, and the risk of falling into unstable combustion or misfire is reduced.

  In the high-speed opening / closing operation, the opening degree of the EGR valve 23 may be opened larger than the target opening degree or may be narrowed smaller than the target opening degree. Preferably, an operation of opening the opening of the EGR valve 23 larger than the target opening and an operation of narrowing the opening of the EGR valve 23 smaller than the target opening are alternately repeated. The maximum value (larger than the target opening) and the minimum value (smaller than the target opening) of the opening of the EGR valve 23 are set so that the average value of the actual opening of the EGR valve 23 matches the target opening. Set. For example, the difference | Δα | between the maximum value of the opening degree of the EGR valve 23 and the target opening degree and the difference | Δβ | between the minimum value and the target opening degree are made substantially equal.

  The magnitudes of the differences | Δα | and | Δβ | may be changed according to the operating region of the internal combustion engine. For example, | Δα | and | Δβ | are increased as the required load is increased or increased as the engine speed is increased. When the engine speed and the required load are high (the intake air amount and the fuel injection amount charged into the cylinder 1 are large), the EGR misfire resistance is large. Therefore, even if | Δα | is increased, that is, the opening degree of the EGR valve 23 is targeted. Even if it deviates greatly from the opening, no misfire occurs in the cylinder 1.

  The high-speed opening / closing operation for quickly returning to the target opening after operating the EGR valve 23 to an opening deviating from the target opening is executed at least once each time the intake stroke of each cylinder comes. When the opening degree of the EGR valve 23 is vibrated as shown in FIG. 2, the frequency (Hz) of the vibration is set to the frequency of intake strokes of any cylinder 1 (the number of cylinders × (1/2)). X (engine speed (rpm) / 60) several times to several tens of times, so that several to several tens of pulsations are generated in EGR gas for one intake stroke of a cylinder 1 .

  In the present embodiment, the flow passage (intake passage) 3 for the first fluid (fresh air) 3 and the flow passage (EGR passage) 21 for the second fluid (EGR gas) that merges with the first flow passage 3 are provided. An internal combustion engine provided is controlled, and a valve (EGR valve) 23 provided on the second flow passage 21 is opened to allow fluid flowing through the flow passage 21 to flow through the first flow passage 3. A control device for an internal combustion engine, which performs a high-speed opening / closing operation for quickly returning to the target opening after operating the valve 23 to an opening deviating from the target opening when mixing with fluid flowing through 0 was configured.

According to the present embodiment, it is possible to sufficiently mix two fluids handled by the internal combustion engine and improve the performance exhibited by the internal combustion engine. That is, the fresh air to be charged into the cylinder 1 and the EGR gas can be uniformly mixed, and local unevenness does not occur in the concentration of the EGR gas in the air-fuel mixture, and the ignition combustion can be stabilized. Since the risk of misfire of the air-fuel mixture in the cylinder 1 is reduced, it is allowed to raise the upper limit of the EGR rate and the advance amount of the ignition timing, further reducing the NO _x emission amount, and further improving the fuel consumption performance Can contribute to improvement.

  The present invention is not limited to the embodiment described in detail above. As shown in FIG. 3, the high-speed opening / closing operation of the EGR valve 23 may be executed only when the target opening degree is reduced, that is, when the deceleration request for reducing the opening degree of the throttle valve 32 is requested. Then, the opportunity to change the opening degree of the EGR valve 23 is reduced, and the power consumption by the stepper motor that drives the EGR valve 23 is reduced. Reduction of power consumption leads to reduction of fuel consumption of an internal combustion engine that generates power.

  The application target of the present invention is not limited to the EGR device 2. For example, it is conceivable to apply the technical idea of the present invention to the operation of the PCV valve 62 of the blow-by gas recirculation device 6. That is, an internal combustion engine having a flow passage (intake passage) 3 for the first fluid (fresh air) and a flow passage (PCV passage) 61 for the second fluid (blow-by gas) that merges with the first flow passage 3. In controlling the engine, the ECU 0 as a control device opens a valve (PCV valve) 62 provided on the second flow path 61 to allow fluid flowing through the flow path 61 to flow through the first flow path 3. When ventilating the blow-by gas mixed with the fluid flowing through the valve, the valve 62 is operated to an opening deviating from the target opening, and then a high-speed opening / closing operation for quickly returning to the target opening is executed.

  The target opening degree of the PCV valve 62 increases as the differential pressure between the pressure in the crank chamber 7 and the pressure in the intake passage 3 (surge tank 33) increases. However, if the pressure in the intake passage 3 becomes very small (the intake negative pressure is very large) and the pressure difference between the crank chamber 7 pressure and the pressure in the intake passage 3 exceeds a predetermined value, the pressure difference becomes The larger the value is, the smaller the target opening degree of the PCV valve 62 is. When the pressure in the intake passage 3 is equal to or higher than the atmospheric pressure (the intake pressure is positive), the target opening is set to 0 (the PCV valve 62 is closed) and the blow-by gas through the PCV passage 61 is set. Or block backflow of intake air.

  It is also conceivable to apply the technical idea of the present invention to a cooling water system of a water-cooled internal combustion engine. A cooling water system for an internal combustion engine includes a first flow passage that circulates without passing through a radiator for radiating the cooling water, a first branch passage that branches from the flow passage, passes through the radiator, and then rejoins the flow passage. It is customary to have two flow paths. The second flow passage is provided with a valve for prohibiting / inhibiting the flow of cooling water into the flow passage and the radiator, and when the temperature of the cooling water is low, the valve is closed while the temperature of the cooling water is When the temperature becomes higher than a predetermined temperature, the valve is opened to suppress the temperature rise of the cooling water.

  Therefore, the opening / closing of the valve is controlled by the ECU as a control device, and the valve deviates from its target opening (may be fully open) when the temperature of the cooling water is higher than a predetermined temperature. After operating to the opening (which may be fully closed), a high-speed opening / closing operation is performed to quickly return to the target opening. Then, the temperature of the cooling water circulating through the cooling water system can be made sufficiently uniform, and it becomes easier to keep the internal combustion engine at a temperature suitable for exhibiting its performance.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to control of an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
21 ... Second flow passage (EGR passage)
23 ... Valve (EGR valve)
3 ... First flow passage (intake passage)

Claims (2)

Controlling an internal combustion engine comprising a first fluid flow path and a second fluid flow path that merges with the first flow path,
When opening the valve provided in the second flow passage to mix the fluid flowing through the flow passage with the fluid flowing through the first flow passage, the opening deviates from the target opening. A control device for an internal combustion engine, which performs a high-speed opening / closing operation for quickly returning to a target opening after the operation. The first flow passage is an intake passage that is a fresh air flow passage, and the second flow passage is an EGR passage that is a flow passage of EGR gas,
When the EGR valve, which is a valve provided on the EGR passage, is opened and the EGR gas is mixed with fresh air, the EGR valve is quickly operated after the opening is deviated from the target opening. The control device for an internal combustion engine according to claim 1, wherein the high-speed opening / closing operation for returning to the target opening degree is performed at least once each time an intake stroke comes in the cylinder.

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