JP2006118441A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of suppressing increase of pumping loss in the internal combustion engine provided with a variable mechanism capable of changing valve characteristics of an intake valve and an exhaust valve respectively and capable of changing operating angle of the intake valve in the variable mechanism for the intake valve. <P>SOLUTION: When operating angle of the intake valve is smaller than a predetermined operating angle, an electronic control device delays valve close timing of the exhaust valve to increase valve open period te of the exhaust valve during a suction stroke as compared to the time when operating angle of the intake valve is not smaller than the predetermined operating angle. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes variable mechanisms that vary the valve characteristics of the intake valve and the exhaust valve, and among these, the variable mechanism for the intake valve varies the operating angle of the intake valve. The present invention relates to a control device.

Conventionally, as a system applied to an internal combustion engine, a system that variably controls the operating angle through a variable mechanism that makes the operating angle of an intake valve variable has been put into practical use (for example, see Patent Document 1). In an internal combustion engine employing such a system, the amount of air taken into the combustion chamber can be reduced by reducing the operating angle of the intake valve.
JP 2001-263015 A

  Incidentally, as shown in FIG. 6, in an internal combustion engine having an intake valve and an exhaust valve, the intake valve opening timing (timing when the valve is switched from the closed state) to the exhaust valve closing timing (opening state). The timing at which the valve state is switched to the valve closing state) is set close to the exhaust top dead center timing (the timing at which the piston is located at the exhaust top dead center) TDCe. For example, in the diagrams 201i and 201e illustrated in the figure, the opening timing of the intake valve is set to an advance side (within the exhaust stroke) with respect to the exhaust top dead center timing TDCe, and the closing timing of the exhaust valve is set. Is set to the retard side (within the intake stroke) from the exhaust top dead center timing TDCe. In this example, as shown in the diagram 251, the piston moves from the exhaust top dead center toward the bottom dead center, whereby the pressure in the combustion chamber is changed from the pressure Pme in the exhaust manifold to the pressure in the intake manifold (intake air). (Negative pressure) It has fallen to Pmi.

  In this way, from the exhaust stroke to the intake stroke, the pressure in the combustion chamber is about the same as the intake negative pressure Pmi from the same height as the pressure Pme in the exhaust manifold due to the opening and closing of the intake valve and the exhaust valve and the movement of the piston. It shifts to the height of.

  Here, in an internal combustion engine provided with the above-described variable mechanism that variably controls the operating angle of the intake valve, for example, as shown in a diagram 202i, when the operating angle is reduced, the opening timing of the intake valve is increased. Will be shifted to the retard side. When the valve opening timing is shifted to the retard side, the intake valve lift amount (movement amount from the seating state) at the exhaust top dead center timing TDCe decreases and the intake resistance increases.

  In such a case, in the combustion chamber, for example, as shown in a diagram 252, an excessive pressure drop may occur as the piston moves below the intake negative pressure Pmi. Although this reduced pressure in the combustion chamber then rises and returns to the same level as the intake negative pressure Pmi with an increase in the lift amount of the intake valve, pumping is caused by the excessive pressure drop in the internal combustion engine. Loss will be excessively increased.

  An object of the present invention is to provide a control device for an internal combustion engine that can suppress an increase in pumping loss in an internal combustion engine including the variable mechanism as described above.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
First, the invention according to claim 1 includes variable mechanisms that vary the valve characteristics of the intake valve and the exhaust valve, and among these, the variable mechanism for the intake valve is capable of varying the operating angle of the intake valve. A control device for an internal combustion engine, wherein when the operating angle of the intake valve is smaller than a predetermined operating angle, the intake stroke is delayed by retarding the closing timing of the exhaust valve compared to when the operating angle is not The gist of the present invention is to provide control means for increasing the valve opening period of the exhaust valve.

  According to the above configuration, the exhaust valve opening period in the intake stroke, that is, the exhaust top dead center timing that is the start timing of the same stroke (the piston is positioned at the exhaust top dead center) through the delay of the exhaust valve closing timing. From the time when the exhaust valve is closed in the same stroke (a time when the exhaust valve is switched from the open state to the closed state) is increased (including an increase from “0”). As a result, the amount of exhaust gas introduced into the combustion chamber from the exhaust port side in the intake stroke is increased, and therefore, an excessive pressure drop that is less than the intake negative pressure (negative pressure in the intake manifold) hardly occurs in the combustion chamber. Become.

  Therefore, for example, the excessive amount of the pumping loss (the amount caused by the excessive occurrence of the pressure drop) correlated with the excessive amount of the pressure drop (the amount that is lower than the intake negative pressure in the pressure drop) is allowed. By setting the “predetermined operating angle” of the intake valve so as to fall within the range, it is possible to efficiently suppress the adverse effect caused by the excessive pumping loss.

  By the way, in an internal combustion engine that rotates the crankshaft based on the reciprocating movement of the piston, the moving speed of the piston is generally the lowest at the top and bottom dead center, and the above-mentioned movement becomes closer to the middle point of the reciprocating movement range from the top and bottom dead center. Speed increases. That is, as the piston approaches the intermediate point from the exhaust top dead center, the amount of exhaust gas introduced into the combustion chamber increases per unit time. Therefore, the closing timing of the exhaust valve is retarded as in the present invention. By doing so, the generation of the excessive pumping loss can be efficiently suppressed.

  With respect to the delay angle of the closing timing of the exhaust valve, for example, as in the invention according to claim 2, in the invention according to claim 1, the variable mechanism for the exhaust valve has an operating angle center of the exhaust valve. The control means can adopt a mode in which the control means delays the valve closing timing of the exhaust valve by delaying the operation angle center of the exhaust valve.

  According to a third aspect of the present invention, in the first or second aspect of the invention, the internal combustion engine adjusts the intake air amount by cooperative control of the operating angle of the intake valve and the opening of the throttle valve. The gist of the delay of the closing timing of the exhaust valve by the control means is that it is allowed on the condition that the intake negative pressure is closer to the atmospheric pressure than the predetermined negative pressure.

  In the intake stroke, by suppressing the intake resistance to a small value, it is possible to avoid that the pressure in the combustion chamber is significantly lower than the intake negative pressure (separated from the atmospheric pressure to the negative pressure side). That is, it is possible to suppress an excessive pressure drop that is less than the intake negative pressure. By such suppression, the pumping loss in the intake stroke can be suppressed to a value substantially corresponding to the magnitude of the intake negative pressure (an excessive amount can be suppressed).

  However, if the intake resistance of the intake stroke increases due to a decrease in the operating angle of the intake valve from such a state, an excessive pressure drop is likely to occur in the combustion chamber that is lower than the intake negative pressure. If this occurs, the pumping loss excess correlated with the difference between the peak pressure in the pressure drop (the pressure value when the pressure is most separated from the atmospheric pressure to the negative pressure side) and the intake negative pressure (the pressure drop excess). Will occur.

  In an internal combustion engine that adjusts the intake air amount through control of the opening degree of the throttle valve as in the present invention, the intake negative pressure changes by changing the opening degree. Therefore, for example, in a situation where the peak pressure is lower than the intake negative pressure, the difference between the peak pressure and the intake negative pressure, and hence the excessive amount of pumping loss, changes with the change in the intake negative pressure. .

  For example, if the throttle valve opening is set to a large value and the intake negative pressure becomes small (a value close to atmospheric pressure), the excessive pumping loss increases, and conversely the throttle valve opening decreases. When the intake negative pressure becomes large (a value separated from the atmospheric pressure) by being set, an excessive amount of pumping loss is reduced.

  By the way, since the increase in the exhaust valve opening period in the intake stroke leads to an increase in the internal EGR amount, adverse effects (for example, fluctuations in engine rotation speed, etc.) due to the excessive internal EGR amount are suppressed. For this reason, it is desirable to prohibit unnecessary things regarding the delay of the closing timing of the exhaust valve.

  Accordingly, in such a case, for example, if the delay of the closing timing of the exhaust valve is prohibited when the excessive pumping loss is reduced, that is, when the intake negative pressure is large, the pumping loss is prevented. It is possible to suppress an increase in the amount of internal EGR while keeping the excessive amount of the above small. Conversely, when the excessive pumping loss is large, that is, when the intake negative pressure is small, the delay of the exhaust valve closing timing is allowed to suppress the excessive pumping loss. Will be able to.

  From this point, in the present invention, the delay of the closing timing of the exhaust valve by the control means is allowed on condition that the intake negative pressure is smaller than a predetermined negative pressure (a value close to atmospheric pressure). ing. Accordingly, it is possible to achieve both the suppression of the excessive increase in pumping loss and the suppression of the increase in the internal EGR amount.

The gist of the invention of claim 4 is that, in the invention of claim 3, the predetermined negative pressure is set to an intake negative pressure during idling.
Since the intake air amount becomes almost minimum during idle operation, the internal EGR amount rate tends to be excessive if the delay of the valve closing timing of the exhaust valve by the control means is allowed under such circumstances. Adverse effects can never be ignored. In this respect, according to the present invention, during the idling operation, the delay of the closing timing of the exhaust valve by the control means is prohibited, so that such adverse effects can be suppressed.

  Further, during idle operation, the throttle valve opening is set to a substantially minimum value, so that the intake negative pressure is substantially maximum (almost maximum on the side away from the atmospheric pressure). That is, by setting the predetermined negative pressure to such an approximately maximum intake negative pressure, the pumping loss is reduced over almost the entire range of the fluctuation of the intake negative pressure by the throttle valve opening control except during the idling operation. An excessive increase can be suppressed.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the control means sets the closing timing of the exhaust valve to the retard side as the engine speed increases. This is the gist.

  For example, when the gas in the combustion chamber is heated by heat transfer from the outside through the inner wall surface of the chamber, or the air flows into the chamber from the outside through a gap between the inner wall surface and the outer peripheral surface of the piston As a result, the pressure in the combustion chamber is increased.

  Regarding the heating, the longer the heating time, the higher the pressure in the combustion chamber tends to be. And, regarding the inflow of air, the slower the moving speed of the piston, the easier the inflow, that is, the higher the pressure in the combustion chamber. There is a tendency. The heating time tends to be longer as the engine speed is lower, and the piston moving speed tends to be lower as the engine speed is lower. That is, the pressure in the combustion chamber tends to increase as the engine speed decreases, in other words, as the engine speed increases, the pressure does not easily increase. Therefore, the pressure drop in the combustion chamber becomes more difficult to be suppressed as the engine rotational speed is higher. As a result, the degree of the pressure drop is likely to become remarkable as the engine rotational speed is higher.

  In that respect, in the present invention, the closing timing of the exhaust valve is set to the retard side as the engine speed is higher, so that the valve opening period of the exhaust valve in the intake stroke is further increased, and the engine speed is increased. Even when the pressure is high, the pressure drop is suitably suppressed.

  Further, in the present invention, when the closing timing of the exhaust valve is retarded by the control means, the valve closing timing is set to the opposite side of the retarded side, that is, the advanced side as the engine speed is lower. Therefore, an increase in the internal EGR amount when the engine speed is low (during low speed operation) can be suppressed. Therefore, during the low speed operation where the internal EGR amount rate is likely to be excessive, it is possible to suppress the occurrence of adverse effects (for example, fluctuations in engine rotation speed, engine stall, etc.) due to the increase in the internal EGR amount.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 1 shows a schematic structure of an in-vehicle internal combustion engine 10 to which the present embodiment is applied. As shown in the figure, the internal combustion engine 10 is mainly configured to include an intake passage 11, a combustion chamber 12 and an exhaust passage 13.

  An intake passage 11 of the internal combustion engine 10 is provided with an air flow meter 14 that detects the air flow rate inside the engine, and a throttle valve 15 that changes the flow area inside the air flow meter 14 to change the air flow rate. 16 is connected to the combustion chamber 12. The combustion chamber 12 is connected to the exhaust passage 13 via the exhaust valve 17. The intake valve 16 and the exhaust valve 17 are driven according to the rotation of the internal combustion engine 10 to open and close the intake passage 11 and the exhaust passage 13 with respect to the combustion chamber 12.

  Air is sucked into the combustion chamber 12 through the intake passage 11. When an ignition plug 18 ignites an air-fuel mixture composed of this air and fuel injected from a fuel injection valve (not shown), the air-fuel mixture burns and the piston 19 reciprocates to serve as an engine output shaft. The crankshaft rotates. The air-fuel mixture after combustion is sent out from the combustion chamber 12 to the exhaust passage 13 as exhaust gas. An exhaust purification catalyst 20 made of a three-way catalyst is built in the exhaust passage 13 so that the exhaust gas from the combustion chamber 12 is purified.

  The valve system of the exhaust valve 17 of the internal combustion engine 10 is provided with a variable valve timing mechanism (VT variable mechanism) 21, and the valve operating system of the intake valve 16 is provided with a variable operating angle mechanism 22.

  As shown in FIG. 2A, the variable valve timing mechanism 21 is configured as a mechanism for continuously changing the operating angle center φ of the exhaust valve 17 (that is, the operating angle center of the cam that drives the exhaust valve 17) φ. Yes. In the internal combustion engine 10, a mechanism for changing the operating angle center φ by changing the relative rotation phase of the camshaft with respect to the crankshaft is adopted as the variable valve timing mechanism 21.

  Further, the operating angle variable mechanism 22 is configured as a mechanism for continuously changing the operating angle θ of the intake valve 16 as shown in FIG. As shown in FIG. 5B, in the operating angle variable mechanism 22, the maximum lift amount of the intake valve 16 is increased / decreased along with the increase / decrease of the operating angle θ. Further, in the variable mechanism 22, the valve opening timing of the intake valve 16 (timing when the intake valve 16 switches from the closed state to the open state) is advanced / retarded in accordance with the increase / decrease of the operating angle θ. It has become. In this case, for example, when the operating angle θ is increased, the valve opening timing is advanced, and conversely, when the operating angle θ is decreased, the valve opening timing is delayed.

  Various controls such as fuel injection control and ignition timing control in the internal combustion engine 10 configured as described above are performed by the electronic control unit 30. The electronic control unit 30 includes a central processing unit (CPU) that performs various arithmetic processes related to the control of the internal combustion engine 10, a read-only memory (ROM) in which a control program and data are recorded, the calculation results and sensors of the CPU. A random access memory in which data input from the memory is recorded, an input / output port for transmitting / receiving signals to / from the outside, and the like are provided.

  In addition to the air flow meter 14, the throttle port provided in the throttle valve 15, the VT sensor provided in the variable valve timing mechanism 21, and the operation provided in the variable operating angle mechanism 22 are provided at the input port of the electronic control unit 30. An angle sensor is connected. The throttle sensor detects the opening degree (throttle opening degree) Ta of the throttle valve 15. The VT sensor detects the current operating angle center φ of the exhaust valve 17. The operating angle sensor detects the current operating angle θ of the intake valve 16.

  Further, an accelerator position sensor 31, a crank angle sensor 32, and a water temperature sensor 33 are connected to the input port. The accelerator position sensor 31 detects the amount of accelerator depression. The crank angle sensor 32 detects the rotational speed of the crankshaft, that is, the engine rotational speed Ne. The water temperature sensor 33 detects the temperature of the cooling water of the internal combustion engine 10 (engine cooling water temperature). In addition to this, various sensors for detecting the operating state of the internal combustion engine 10 and the traveling state of the vehicle are connected to the input port.

  Various actuators used for controlling the internal combustion engine 10 including the throttle valve 15, the spark plug 18, the valve timing variable mechanism 21 and the operating angle variable mechanism 22 are connected to the output port of the electronic control unit 30. The electronic control unit 30 performs various controls of the internal combustion engine 10 by driving and controlling these actuators based on the detection results of the various sensors.

  For example, the valve characteristics such as the operating angle center φ and the operating angle θ are controlled in the following manner. That is, the electronic control unit 30 first operates the exhaust valve 17 suitable for the current engine operating state based on the accelerator pedal depression amount, the engine rotational speed Ne, and the like detected by the accelerator position sensor 31 and the crank angle sensor 32. Target values for the angle center φ and the operating angle θ of the intake valve 16 are calculated. Then, the electronic control unit 30 causes the current operating angle center φ of the exhaust valve 17 and the operating angle θ of the intake valve 16 detected by the VT sensor and the operating angle sensor to coincide with the calculated target values. The valve timing variable mechanism 21 and the operating angle variable mechanism 22 are feedback-controlled. As a result, optimum valve characteristics of the valves 16 and 17 are obtained in accordance with the current engine operating state.

  By the way, in the internal combustion engine 10 configured as described above, the amount of air introduced into the combustion chamber 12 (intake air amount) varies with the change in the operating angle θ of the intake valve 16 by the operating angle variable mechanism 22. Change. Therefore, the electronic control unit 30 performs the opening degree control of the throttle valve 15 in conjunction with the variable control of the operating angle θ (cooperative control of the operating angle θ and the throttle opening degree Ta). As a result, a necessary intake air amount is ensured regardless of the change in the operating angle θ of the intake valve 16 by the operating angle variable mechanism 22.

In the present embodiment, the throttle opening degree Ta is adjusted to the minimum during idle operation.
Next, a characteristic configuration of the present embodiment will be described.

  In the intake stroke, by reducing the intake resistance, the combustion chamber pressure (pressure in the combustion chamber 12) Pc is significantly lower than the intake negative pressure (negative pressure in the intake manifold) Pmi (separates from atmospheric pressure to the negative pressure side). Can be avoided. That is, it is possible to suppress an excessive pressure drop that is lower than the intake negative pressure Pmi. As a result of such suppression, the pumping loss in the intake stroke can be suppressed to a value substantially corresponding to the magnitude of the intake negative pressure Pmi, that is, the amount that is lower than the intake negative pressure Pmi (hereinafter referred to as “pressure”). (Referred to as “excessive reduction”).

  However, when the intake resistance increases due to the valve opening timing being shifted to the retard side due to the decrease in the operating angle θ of the intake valve 16 from such a state, an excessive combustion chamber pressure that is lower than the intake negative pressure Pmi. Decrease in Pc tends to occur. In this case, also in the pumping loss, the above-mentioned “excessive pressure drop” which is the difference between the peak pressure (pressure value when most separated from the atmospheric pressure to the negative pressure side) Pcmin and the intake negative pressure Pmi in the combustion chamber pressure Pc drop. An excessive amount correlating with "will occur.

  Therefore, in the present embodiment, in order to suppress an increase in pumping loss due to such an excessive decrease in the combustion chamber pressure Pc, the operating angle center φ of the exhaust valve 17 is controlled according to the operating angle θ of the intake valve 16 through the electronic control unit 30. The “operation angle center retardation processing” is performed to retard the angle.

  This “operation angle center retardation processing” is performed through the retardation of the operation angle center φ through the valve opening period te of the exhaust valve 17 in the intake stroke, that is, the exhaust top dead center timing (the piston 19 is located at the exhaust top dead center). Timing) The period from the TDCe to the exhaust valve closing timing (timing when the exhaust valve 17 switches from the open state to the closed state) in the same stroke is increased. That is, the “operating angle center retardation process” is introduced into the combustion chamber 12 from the exhaust port side with the movement of the piston 19 from the exhaust top dead center through the increase of the valve opening period te of the exhaust valve 17 in the intake stroke. By increasing the amount of exhaust gas, the reduction of the combustion chamber pressure Pc is suppressed.

  Hereinafter, the procedure of such control processing will be described with reference to the flowchart of FIG. The control routine shown in this flowchart is executed through the electronic control unit (control means) 30 by, for example, time interruption every predetermined time.

  In this control routine, first, in step S110, it is determined whether or not the operating angle θ of the intake valve 16 is smaller than a predetermined operating angle θ1. In the present embodiment, the predetermined operating angle θ1 is set to a value that allows the magnitude of “excessive pumping loss” correlated with the “excessive pressure drop” to be within an allowable range. That is, the predetermined operating angle θ1 is a value when the magnitude of the “excessive pumping loss” becomes an allowable limit.

  Therefore, when it is determined in step S110 that the operating angle θ is smaller than the predetermined operating angle θ1 (step S110: YES), the “excessive pumping loss” cannot be within the allowable range. As soon as the opening timing of the intake valve 16 is farther from the exhaust top dead center timing TDCe, the process proceeds to step S120.

  When the determination result in step S110 is NO, that is, when it is determined that the operating angle θ of the intake valve 16 is equal to or larger than the predetermined operating angle θ1, the “excessive pumping loss” is out of the allowable range. The valve opening timing of the intake valve 16 is not retarded to the extent that it deviates, and the processing in this control routine is temporarily terminated, assuming that the “operation angle center retardation processing” is unnecessary.

  In step S120, it is determined whether or not the intake negative pressure Pmi is smaller than the predetermined negative pressure Pmi2, that is, whether or not the intake negative pressure Pmi is closer to (higher) atmospheric pressure than the predetermined negative pressure Pmi2. Incidentally, in the present embodiment, the intake negative pressure Pmi is detected by the air flow meter 14, the throttle sensor, the crank angle sensor 32, and the operating angle sensor, that is, the air flow rate in the intake passage 11, the throttle opening Ta, the engine rotation. The estimation is based on the speed Ne, the operating angle θ, and the like.

  When the determination result is YES, that is, when it is determined that the intake negative pressure Pmi is smaller than the predetermined negative pressure Pmi2, the process proceeds to step S130, that is, the “operating angle center retardation process” is allowed. The Conversely, when the determination result is NO, that is, when it is determined that the intake negative pressure Pmi is the same as or larger than the predetermined negative pressure Pmi2 (far from the atmospheric pressure), the above “operation angle center retardation processing” is allowed. The processing of this control routine is temporarily terminated without being performed, in other words, the “operation angle center retardation processing” is prohibited.

In the present embodiment, the reason why the “actuation angle center retardation processing” is switched between permissible and prohibited in accordance with the magnitude of the intake negative pressure Pmi is as described below.
That is, in the present embodiment in which the intake air amount is adjusted through the control of the throttle opening Ta, the intake negative pressure Pmi is changed by changing the throttle opening Ta. Therefore, for example, in the situation where the peak pressure Pcmin is lower than the intake negative pressure Pmi, the magnitude of the “excessive pressure drop” also changes with the change in the intake negative pressure Pmi.

  For example, when the intake negative pressure Pmi becomes small (a value close to the atmospheric pressure) by setting the throttle opening Ta large, the above “excessive pressure drop” becomes large, and conversely, the throttle opening Ta When the intake negative pressure Pmi becomes large (a value separated from the atmospheric pressure) by being set to be small, the “excessive pressure drop” becomes small.

  On the other hand, an increase in the valve opening period te of the exhaust valve 17 in the intake stroke leads to an increase in the internal EGR amount, so that adverse effects (for example, fluctuations in engine speed, etc.) due to the excessive internal EGR amount are suppressed. In order to achieve this, it is desirable to prohibit unnecessary things regarding the increase in the valve opening period te.

  Therefore, in such a case, for example, when the “excessive amount of pumping loss” is small, that is, when the intake negative pressure Pmi is large (low), the “operation angle center retardation processing” is prohibited. By doing so, it is possible to suppress an increase in the internal EGR amount while keeping the “excessive amount of pumping loss” small. Conversely, when the “excessive amount of pumping loss” becomes large, that is, when the intake negative pressure Pmi is small (high), the above “pumping loss delay processing” is allowed to allow such “pumping loss reduction”. An increase in “excess” can be suppressed.

  That is, the determination process in step S120 is provided to achieve both suppression of such an increase in “excessive amount of pumping loss” and suppression of an increase in excessive internal EGR amount.

  By the way, since the intake air amount becomes almost minimum during idle operation, the internal EGR amount rate is likely to be excessive if the “operation angle center retardation processing” is allowed under such circumstances, and the above-mentioned adverse effects are also caused. It cannot be ignored at all. From this point, in the present embodiment, the predetermined negative pressure Pmi2 is set to a value equal to the intake negative pressure Pmi during idle operation. That is, the above-described adverse effect is suppressed by prohibiting the “operation angle center retardation processing” when the intake air amount is small as in the idling operation.

  Further, since the throttle opening degree Ta is set to a substantially minimum during idle operation, the intake negative pressure Pmi becomes substantially maximum (almost maximum on the side away from the atmospheric pressure). That is, in the present embodiment, the predetermined negative pressure Pmi2 is set to a value equal to the substantially maximum intake negative pressure Pmi, so that the fluctuation of the intake negative pressure Pmi by the throttle valve opening control is excluded except during the idling operation. The increase of the “excessive amount of pumping loss” is suppressed over almost the entire range.

  As described above, in the “operating angle center delay process” in step S130, the valve closing timing of the exhaust valve 17 is retarded through the valve timing variable mechanism 21, thereby the valve opening period te of the exhaust valve 17 in the intake stroke. Increase is achieved. In the present embodiment, in the “operation angle center retardation process”, the valve closing timing of the exhaust valve 17 is set to the retard side as the engine rotational speed Ne increases. Hereinafter, this setting process will be described.

  For example, the gas in the combustion chamber 12 is heated by heat transfer from the outside through the inner wall surface of the chamber 12, or air enters the chamber 12 from the outside through a gap between the inner wall surface and the outer peripheral surface of the piston 19. In the case of inflow, the combustion chamber pressure Pc is increased by these.

  As for the heating, the longer the heating time, the higher the combustion chamber pressure Pc tends to increase, and as for the inflow of air, the slower the moving speed of the piston 19, the easier the inflow, that is, the higher the combustion chamber pressure Pc. It is in. The heating time tends to increase as the engine speed Ne decreases, and the moving speed of the piston 19 tends to decrease as the engine speed Ne decreases. That is, the combustion chamber pressure Pc is likely to increase as the engine rotational speed Ne decreases, in other words, the combustion chamber pressure Pc does not easily increase as the engine rotational speed Ne increases. Therefore, the pressure drop in the combustion chamber 12 becomes more difficult to be suppressed as the engine rotational speed Ne is higher, and as a result, the degree of the pressure drop is likely to become remarkable as the engine rotational speed Ne is higher.

  That is, in the present embodiment, the closing timing of the exhaust valve 17 is set in accordance with the engine rotational speed Ne in order to cope with the difference in the degree of pressure drop based on the difference in the engine rotational speed Ne. As described above, in this setting, the valve closing timing of the exhaust valve 17 is set to the retard side as the engine rotational speed Ne increases, so that the valve opening period te of the exhaust valve 17 in the intake stroke is set to the engine rotational speed Ne. Accordingly, it is increased so as to improve the effect of suppressing the pressure drop when the engine speed Ne is high.

  In the “operating angle center retardation processing”, for example, the closing timing of the exhaust valve 17 is set to a timing according to the difference between the current operating angle θ of the intake valve 16 and the predetermined operating angle θ1. The target operating angle center φ (target operating angle center) may be variably set. In this case, for example, as the current operating angle θ of the intake valve 16 is significantly lower than the predetermined operating angle θ1 (the difference between the operating angle θ and the predetermined operating angle θ1 is larger), the target operating angle center is more delayed. This is variably set so that it becomes the value on the corner side. According to this, since the valve closing timing of the exhaust valve 17 is set to the retard side as the valve opening timing of the intake valve 16 is on the retard side, the “excessive amount of pumping loss” is suitably set. It becomes possible to suppress.

  Further, for example, the change rate of the closing timing of the exhaust valve 17 (change per unit time toward the retard side) according to the decrease rate of the operating angle θ of the intake valve 16 (change amount per unit time in the decrease direction). (Amount) may be changed. According to this, for example, by setting these relationships so that the change rate of the valve closing timing of the exhaust valve 17 becomes higher as the decrease rate of the operating angle θ is higher, the “excessive amount of pumping loss”. Can be suitably suppressed.

  Further, for example, the predetermined operating angle θ1 may be variably set to a value corresponding to the closing timing of the exhaust valve 17. In this case, for example, the predetermined operating angle θ1 is set smaller as the valve closing timing of the exhaust valve 17 is on the retard side. According to this, since the “operating angle center delay processing” is not started unless the operating angle θ of the intake valve 16 becomes further smaller than the predetermined operating angle θ1 set to be small, the closing timing of the exhaust valve 17 is determined. It can be avoided that the angle is excessively retarded, and an excessive amount of internal EGR is prevented.

  Hereinafter, control mode examples in the present embodiment will be described with reference to FIGS. 4 and 5. FIG. 4 shows an example when the intake negative pressure Pmi is adjusted to a small intake negative pressure Pmi1 smaller than the predetermined negative pressure Pmi2 (close to atmospheric pressure) through the opening degree control of the throttle valve 15. FIG. 5 shows an example during idling, that is, when the intake negative pressure Pmi is adjusted to the predetermined negative pressure Pmi2. A diagram 101i in both figures shows a state in which the operating angle θ of the intake valve 16 is less than a predetermined operating angle θ1.

  First, FIG. 4 will be described. Lines 101e and 151 shown by solid lines in the same figure are examples in which the “operation angle center retardation process” is executed because the operation angle θ of the intake valve 16 is less than the predetermined operation angle θ1. On the other hand, a diagram 102e and a diagram 152 shown by broken lines are comparative examples with respect to the above example, and since the operating angle θ of the intake valve 16 is not less than the predetermined operating angle θ1, the “operating angle center retardation processing” is performed. Shows a mode in which is not executed.

  In this comparative example, with the movement of the piston 19 from the exhaust top dead center, the combustion chamber pressure Pc greatly decreases from the pressure Pme in the exhaust manifold beyond the small intake negative pressure Pmi1. That is, the peak pressure Pcmin is large and lower than the small intake negative pressure Pmi1. The difference between the peak pressure Pcmin and the small intake negative pressure Pmi1 corresponds to the “excessive pressure drop”. In other words, the larger the absolute value of this difference, the larger the “excessive pressure drop”, and consequently the “excessive pumping loss”.

  On the other hand, in the example shown by the solid line (lines 101e and 151), the operating angle center φ of the exhaust valve 17 is retarded by the above “operating angle center delay processing” as compared with the comparative example. Thus, the valve closing timing of the valve 17 is retarded. As a result, the valve opening period te of the exhaust valve 17 in the intake stroke is increased, and the decrease start timing of the combustion chamber pressure Pc from the pressure Pme is shifted to the retard side. As the lift amount of the intake valve 16 increases, the combustion chamber pressure Pc decreases from the pressure Pme toward the small intake negative pressure Pmi1 without significantly lowering it. That is, “excessive pressure drop” and, in turn, “excessive pumping loss” are suppressed.

  In the example shown in FIG. 5, the intake negative pressure Pmi is adjusted to the predetermined negative pressure Pmi2 as described above. Further, in this example, when the pressure in the combustion chamber 12 decreases with the movement of the piston 19 from the exhaust top dead center, the combustion chamber pressure Pc is greater than the intake negative pressure Pmi during idle operation (predetermined negative pressure Pmi2 in this example). There is a limit to the change range of the operating angle θ of the intake valve 16 (that is, the valve opening timing of the valve 16) so as not to cause the occurrence of low (larger in the negative pressure side) as much as possible. That is, in the example shown in the figure, a minimum limit is provided for the operating angle θ of the intake valve 16, so that a limit on the retard side is also set for the valve opening timing of the valve 16. Generation | occurrence | production of the combustion chamber pressure Pc fall which is less than the intake negative pressure Pmi at the time of idling operation is suppressed.

  It should be noted that a diagram 111e and a diagram 161 indicated by solid lines in the same figure indicate that the intake negative pressure Pmi is equal to the predetermined negative pressure Pmi2 even though the operating angle θ of the intake valve 16 is less than the predetermined operating angle θ1. For this reason, the “operation angle center retardation processing” is prohibited. On the other hand, a diagram 112e and a diagram 162 indicated by broken lines are comparative examples with respect to the above example, and the processing of step S120 in the flowchart of FIG. 3 is omitted. That is, this comparative example is different from the above-described solid line (diagram 111e, diagram 161) to which the flowchart of FIG. 3 is applied, on condition that the operating angle θ of the intake valve 16 is lower than the predetermined operating angle θ1. As described above, the “operation angle center retardation processing” is forcibly executed.

  In the example of both the solid line and the broken line shown in FIG. 5, the minimum limit of the operating angle θ is set, so that the combustion chamber pressure Pc is the pressure in the exhaust manifold due to the movement of the piston 19 from the exhaust top dead center. The pressure decreases from Pme toward this without falling below a predetermined negative pressure Pmi2. In this case, since the combustion chamber pressure Pc does not fall below the intake negative pressure Pmi, there is no “excessive pumping loss”.

  Here, if the operating angle θ of the intake valve 16 is further made smaller than the above minimum value so that the combustion chamber pressure Pc is lower than the intake negative pressure Pmi (in this case, equal to the predetermined negative pressure Pmi2), “ An excessive amount of pumping loss will occur. However, even in such a case, the example of FIG. 5 is different from the example of FIG. 4 in that the difference in intake negative pressure Pmi (predetermined negative pressure) as long as there is no difference in the operating angle θ of the intake valve 16, that is, the valve opening timing. The “excessive amount of pumping loss” is small by an amount corresponding to the difference between Pmi2 and the small intake negative pressure Pmi1. Further, regarding the magnitude of the pumping loss excluding such an excessive amount, the example of FIG. 5 is larger than the example of FIG. 4 by an amount corresponding to the difference in the intake negative pressure Pmi.

  Therefore, the ratio of the magnitude of the excess to the pumping loss excluding the excess (hereinafter referred to as excess ratio) is significantly smaller in the example of FIG. 5 than in the example of FIG. . That is, as the intake negative pressure Pmi is adjusted to a larger (lower) value, the excess rate becomes smaller, and as a result, the merit of executing the “operating angle center retardation processing” is diminished. Therefore, in the aspect with a small excess rate as in the example shown in FIG. 5, the “operation angle center retardation processing” is executed as in the comparative example shown by a broken line (line 112e, line 162), for example. Even so, the benefits of this are not necessarily significant.

  On the other hand, execution of the “operation angle center retardation processing” causes an increase in the internal EGR amount. When the intake air amount is small as in the idling operation, the increase in the internal EGR amount rate accompanying the increase in the internal EGR amount is likely to be remarkable, and the adverse effect becomes conspicuous. That is, for these reasons, the merit of executing the “operation angle center retardation processing” decreases as the intake negative pressure Pmi increases (lower).

  Therefore, as in the present embodiment, when the intake negative pressure Pmi is large (low), the “operation angle center retardation processing” is prohibited, thereby suppressing excessive pumping loss and the internal EGR amount. Thus, it is possible to achieve both the suppression of the increase in the amount of the increase and the reduction of the increase.

In the present embodiment, the following effects can be obtained.
(1) When the operating angle θ of the intake valve 16 is smaller than the predetermined operating angle θ1, the closing timing of the exhaust valve 17 is retarded compared to when the operating angle θ is not, thereby opening the valve 17 in the intake stroke The period te is increased. As a result, the amount of exhaust gas introduced into the combustion chamber 12 from the exhaust port side in the intake stroke is increased, so that the combustion chamber pressure Pc is less likely to be excessively reduced to be lower than the intake negative pressure Pmi.

  Therefore, by setting the predetermined operating angle θ so that the magnitude of “excessive pumping loss” correlated with this “excessive pressure drop” can be within an allowable range, The adverse effect caused by “excess” can be efficiently suppressed.

  By the way, in the internal combustion engine 10 that rotates the crankshaft based on the reciprocating movement of the piston 19, the moving speed of the piston 19 becomes the lowest at the top and bottom dead center, and the piston 19 moves from the top and bottom dead center to the middle point of the reciprocating movement range. The closer it is, the higher the moving speed becomes. That is, as the piston 19 approaches the intermediate point from the exhaust top dead center, the amount of exhaust gas introduced into the combustion chamber 12 per unit time increases, so that the exhaust valve 17 is closed as in this embodiment. By retarding the timing, the occurrence of the excessive pumping loss can be efficiently suppressed.

  (2) The “operating angle center retardation processing” is allowed on condition that the intake negative pressure Pmi is closer to the atmospheric pressure than the predetermined negative pressure Pmi2. According to this, for example, when the “excessive amount of pumping loss” is small, that is, when the intake negative pressure Pmi is large, the “operation angle center retardation processing” is prohibited. An increase in the amount of internal EGR can be suppressed while keeping the “pumping loss excess” small. On the other hand, since the “pumping loss excessive amount” becomes large, that is, when the intake negative pressure Pmi is small, the “operation angle center retardation processing” is allowed. The increase of “excess amount” can be suppressed. Accordingly, it is possible to achieve both the suppression of the occurrence of the excessive pumping loss and the suppression of the increase in the internal EGR amount.

  (3) The predetermined negative pressure Pmi2 is set to the intake negative pressure Pmi during idle operation. Since the amount of intake air is almost minimal during idle operation, the internal EGR rate is likely to be excessive if the above-mentioned “operation angle center retardation processing” is allowed under such circumstances, and the adverse effects associated therewith cannot be ignored. It will be a thing. In this respect, according to the present embodiment, the above-mentioned “operation angle center retardation processing” is prohibited during idling, so that such adverse effects can be suppressed.

  Further, since the throttle opening Ta is set to a substantially minimum during idle operation, the intake negative pressure Pmi is substantially maximized. That is, by setting the predetermined negative pressure Pmi2 to such an approximately maximum intake negative pressure Pmi, the entire range of fluctuation of the intake negative pressure Pmi by the opening degree control of the throttle valve 15 is excluded except during the idling operation. Thus, an increase in “excessive amount of pumping loss” can be suppressed.

  (4) In the “operation angle center retardation process”, the valve closing timing of the exhaust valve 17 is set to the retard side as the engine speed Ne increases. Regarding the pressure drop in the combustion chamber 12, the higher the engine rotation speed Ne, the more difficult it is to be suppressed. As a result, the higher the engine rotation speed Ne, the more likely the pressure drop becomes prominent. In that respect, according to the present embodiment, when the engine rotational speed Ne is high, the valve opening period te of the exhaust valve 17 in the intake stroke is further increased, and the pressure drop is suitably suppressed.

  Further, in the present embodiment, when the “operation angle center retardation processing” is performed, the lower the engine rotational speed Ne, the closer the valve closing timing of the exhaust valve 17 is to the opposite side to the retard side, that is, the advance side. Therefore, the increase in the internal EGR amount when the engine speed Ne is low (during low-speed operation) can be suppressed. Therefore, during the low-speed operation where the internal EGR amount rate is likely to be excessive, it is possible to suppress the occurrence of adverse effects (for example, fluctuations in the engine rotational speed Ne, engine stall, etc.) due to the increase in the internal EGR amount.

In addition, embodiment is not limited above, For example, it is good also as the following aspects.
In the above embodiment, the closing timing of the exhaust valve 17 is set to the retard side as the engine rotational speed Ne is higher in the “operation angle center retardation processing”, but such setting is not indispensable. The valve closing timing may not be variably set according to the rotational speed Ne.

  For example, in the example of FIG. 4, the “operating angle center retardation process” is executed to further retard the valve closing timing from the state where the valve closing timing of the exhaust valve 17 is already within the intake stroke. Instead, for example, the “operating angle center retardation process” may be executed to shift the valve closing timing from the exhaust stroke to the intake stroke beyond the exhaust top dead center timing TDCe.

  In the above embodiment, the predetermined negative pressure Pmi2 used for the condition of whether or not to allow execution of “operation angle center retardation processing” is set to the intake negative pressure Pmi during idle operation. For example, it may be set to a value smaller (higher) than the intake negative pressure Pmi during the idling operation.

  In the above embodiment, the “working angle center retardation processing” is allowed to be executed on condition that the intake negative pressure Pmi is a value closer (smaller) to the atmospheric pressure than the predetermined negative pressure Pmi2. The setting of the condition is not essential. For example, the execution of the “operating angle center retardation process” may be permitted only when the operating angle θ of the intake valve 16 is smaller than the predetermined operating angle θ1.

  In the above embodiment, the intake air amount is adjusted by cooperative control of the operating angle θ of the intake valve 16 and the throttle opening Ta. However, such adjustment is not essential, for example, only by the operating angle θ. The present invention may be applied to an internal combustion engine that adjusts the intake air amount.

  In the above embodiment, the advance / retard of the valve closing timing of the exhaust valve 17 is performed through the advance / retard of the operating angle center φ of the valve 17. Further, a variable mechanism that makes the operating angle of the exhaust valve 17 variable may be provided, and the exhaust angle may be decreased / increased. In this case, for example, the valve closing timing can be advanced by decreasing the operating angle, and the valve closing timing can be retarded by increasing the operating angle.

The schematic diagram which shows the control system of the internal combustion engine of one Embodiment. The figure which shows the variable aspect of the valve characteristic of the VT variable mechanism (a) applied to the embodiment, and an operating angle variable mechanism (b). The flowchart regarding the control for suppressing the increase in the pumping loss in the embodiment. The figure which shows an example of the control aspect in the embodiment. The figure which shows an example of the control aspect in the embodiment. The figure which shows the relationship between the operating angle (lift amount) of a conventional intake valve, and a combustion chamber pressure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 15 ... Throttle valve, 16 ... Intake valve, 17 ... Exhaust valve, 21 ... Valve timing variable mechanism, 22 ... Operating angle variable mechanism, 30 ... Electronic control apparatus which comprises a control means, (theta) ... Operating angle, θ1 ... predetermined operating angle, φ ... operating angle center, Ne ... engine speed, Pmi ... intake negative pressure, Pmi2 ... predetermined negative pressure, Ta ... throttle opening, te ... exhaust valve opening period in intake stroke.

Claims (5)

Each of the intake valves and the exhaust valves is provided with a variable mechanism that varies the valve characteristics, and among these, the variable mechanism for the intake valve is a control device for an internal combustion engine that varies the operating angle of the intake valve. There,
Control means for increasing the opening period of the exhaust valve in the intake stroke by retarding the closing timing of the exhaust valve when the operating angle of the intake valve is smaller than a predetermined operating angle compared to when the operating angle is not An internal combustion engine control apparatus comprising: The variable mechanism for the exhaust valve makes the operating angle center of the exhaust valve variable,
The control device for an internal combustion engine according to claim 1, wherein the control means delays the closing timing of the exhaust valve by delaying the center of the operating angle of the exhaust valve. The internal combustion engine adjusts the intake air amount by cooperative control of the operating angle of the intake valve and the opening of the throttle valve,
The internal combustion engine according to claim 1 or 2, wherein the delay of the closing timing of the exhaust valve by the control means is allowed on the condition that the intake negative pressure is a value closer to the atmospheric pressure than the predetermined negative pressure. Control device. The control device for an internal combustion engine according to claim 3, wherein the predetermined negative pressure is set to an intake negative pressure during idle operation. The control device for an internal combustion engine according to any one of claims 1 to 4, wherein the control means sets the valve closing timing of the exhaust valve to a retard side as the engine speed increases.

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