JP2015137619A - Control device of spark ignition type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately suppress generation of PM even when the temperature of an internal combustion engine 10 is low.SOLUTION: A control device 50 retards the valve opening timing of an intake valve 16 to retard the valve closing timing, and thereby makes an expansion ratio higher than a compression ratio. Also, the control device 50 performs retardation control to ignition timing in a case where a temperature Tc of a catalyst 32 is low. The control device 50 stops retardation control to ignition timing at the time when the catalyst 32 is partially activated. At this time, the control device 50 advances the valve opening timing of the intake valve 16 to retard the valve opening timing of an exhaust valve 26.

Description

  The present invention relates to a control device for a spark ignition type internal combustion engine that is applied to a spark ignition type internal combustion engine having a variable mechanism that makes the opening timing of an intake valve variable.

  For example, Patent Document 1 proposes a technique for performing a control for retarding the ignition timing during the warm-up control of the catalyst of the internal combustion engine mounted on the hybrid vehicle and then terminating the retard control of the ignition timing. Yes. Specifically, first, the catalyst is warmed up by retarding the ignition timing while suppressing the output of the internal combustion engine to a minimum value. When the catalyst is partially activated, the retard control is terminated, and the output of the internal combustion engine is limited but the output is increased from the minimum value. As a result, the output of the internal combustion engine can be used for traveling even before the catalyst is completely warmed up.

JP 2012-40915 A

  However, as described above, when the retard control of the ignition timing is completed before the catalyst warm-up is completed, particulate matter (in addition to hydrocarbon (HC) purified by the catalyst during exhaust of the internal combustion engine) It has been found by the inventor that a large amount of PM) may be contained.

  The present invention has been made in view of such circumstances, and an object thereof is a spark ignition type capable of suitably suppressing the generation of PM even when the ignition timing retarding control is terminated early. An object of the present invention is to provide a control device for an internal combustion engine.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
Technical idea 1: Applicable to a spark ignition type internal combustion engine having a variable mechanism that makes the opening timing of the intake valve variable, and delays the ignition timing to activate the catalyst provided with the exhaust passage of the internal combustion engine. A retard angle control unit that performs angle control, and a valve timing control processing unit that controls the valve opening timing of the intake valve by operating the variable mechanism, wherein the internal combustion engine If the intake valve is in a predetermined operating region, the valve opening timing of the intake valve is set to be retarded from the top dead center, and the internal combustion engine is in the predetermined operating region, A control device for a spark ignition type internal combustion engine that sets the valve opening timing of the intake valve to an advance side from the top dead center on the condition that the retard control of the ignition timing is finished and the temperature of the internal combustion engine is low. .

  The inventors noticed that the PM generation becomes significant when the ignition timing retarding control is terminated early, when the opening timing of the intake valve is set after top dead center. It came to the idea that it seems to be because the temperature of the inner wall of the cylinder defining the combustion chamber is low. Here, in the above apparatus, the opening timing of the intake valve is set to the retard side with respect to the top dead center in a predetermined operation region. For this reason, when the temperature of the inner wall of the cylinder is low when in the predetermined operating range, PM generation may become remarkable by terminating the retard control of the ignition timing. Therefore, in the above apparatus, when the internal combustion engine is in a predetermined operating range, the opening timing of the intake valve is set from the top dead center on the condition that the retard control of the ignition timing is finished and the temperature of the internal combustion engine is low. Also, the PM generation can be suitably suppressed by setting the angle to the advance side.

The system block diagram concerning one Embodiment. The flowchart which shows the procedure of the catalyst warm-up process concerning the embodiment. The flowchart which shows the procedure of the setting process of the valve timing concerning the embodiment. The time chart which shows the effect of the embodiment.

Hereinafter, an embodiment in which a control device for a spark ignition internal combustion engine is applied to a series / parallel hybrid vehicle will be described with reference to the drawings.
As shown in FIG. 1, a fuel injection valve 14 is provided in the intake passage 12 of the internal combustion engine 10. In the intake passage 12, an air-fuel mixture including fuel injected from the fuel injection valve 14 into the intake passage 12 and intake air is generated. This air-fuel mixture is sucked into the combustion chamber 18 as the intake valve 16 is opened. In the combustion chamber 18, when the air-fuel mixture is combusted by ignition by the spark plug 20, this combustion energy is converted into rotational energy of a crankshaft 24 that is mechanically connected to drive wheels (not shown) of the vehicle via the piston 22. Converted. Thereafter, with the opening of the exhaust valve 26, the air-fuel mixture subjected to combustion is discharged into the exhaust passage 30 as exhaust. A catalyst 32 is provided in the exhaust passage 30, and carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) in the exhaust are purified by the catalyst 32.

  The intake valve 16 is provided with an intake side variable mechanism 34 for changing the valve opening timing, and the exhaust valve 26 is provided with an exhaust side variable mechanism 36 for changing the valve opening timing. Specifically, the intake side variable mechanism 34 and the exhaust side variable mechanism 36 are mechanisms that shift valve opening timing, valve closing timing, etc. (valve timing) while the cam profile is fixed.

  A rotating shaft 40a of the motor generator 40 is mechanically coupled to the drive wheel. The motor generator 40 is connected to a DC / AC conversion circuit (inverter 42) that converts the DC voltage of the battery 44 into an AC voltage and applies the AC voltage to the motor generator 40. In the case of a series / parallel hybrid vehicle, two motor generators 40 are actually provided, but only one is shown in the figure.

  The control device 50 is a control device that controls the internal combustion engine 10 and the motor generator 40. The control device 50 receives, for example, detection values of various sensors such as a temperature sensor 52 that detects the temperature of the catalyst 32, and controls the fuel injection valve 14, the spark plug 20, the intake side variable mechanism 34, the exhaust side variable mechanism 36, and the like. By outputting operation signals to various actuators of the internal combustion engine 10, these various actuators are operated, and combustion control of the internal combustion engine 10 is performed. Control device 50 outputs an operation signal MS to inverter 42 to operate inverter 42, thereby controlling the control amount of motor generator 40.

  Particularly, when the temperature of the catalyst 32 is low, the control device 50 performs the warm-up process. Here, the warm-up process of the catalyst 32 of the internal combustion engine 10 will be described with reference to FIG. The process shown in FIG. 2 is repeatedly executed by the control device 50, for example, at a predetermined cycle.

  In this series of processing, the control device 50 first determines whether or not a catalyst warm-up request flag Fc indicating whether or not there is a warm-up request for the catalyst 32 is “1”. The catalyst warm-up request flag Fc indicates “1” when there is a warm-up request for the catalyst 32, and indicates “0” when there is no warm-up request for the catalyst 32. Specifically, the control device 50 determines that there is no warm-up request when the temperature Tc of the catalyst 32 detected by the temperature sensor 52 is equal to or higher than the activation temperature Tcat, and when the temperature is lower than the activation temperature Tcat, Judge that there is a warm-up request. Here, the activation temperature Tcat is set based on the temperature in the vicinity of the temperature sensor 52 when the entire catalyst 32 is activated.

  When determining that the catalyst warm-up request flag Fc is “1” (S10: YES), the control device 50 determines whether or not the temperature Tc of the catalyst 32 is equal to or higher than the threshold value Tcref (S16). This process is for determining whether a part of the catalyst 32 is activated. Here, the threshold value Tcref is a value lower than the activation temperature Tcat, and is set based on the temperature in the vicinity of the temperature sensor 52 when a part of the catalyst 32 is activated.

  When determining that the temperature Tc of the catalyst 32 is lower than the threshold value Tcref (S16: NO), the control device 50 performs control to retard the ignition timing (S18). Specifically, using a value obtained by adding a correction amount to be corrected to the advance side as the rotational speed of the crankshaft 24 is higher or as the load is larger, to the base value at the time of retarding control of the ignition timing, Set the ignition timing. The ignition timing set in this way is delayed from the ignition timing when the rotation speed and the load are the same after the catalyst 32 is warmed up.

  Subsequently, the control device 50 determines whether or not the upper limit value of the output of the battery 44 is greater than or equal to the required output for traveling (S20). This process is for determining whether the required output can be provided only by the battery 44 or whether the required output cannot be provided unless both the output of the internal combustion engine 10 and the output of the battery 44 are used. is there. Then, when it is determined that the upper limit value of the output of battery 44 is equal to or greater than the required output (S20: YES), control device 50 warms up the command value (rotation speed command value Ne *) of the rotation speed of internal combustion engine 10. The hourly speed Ne1 is set, and the torque command value (torque command value Te *) is set as the warm-up torque Te1 (S22). This process is for limiting the exhaust amount of the internal combustion engine 10 in view of the low purification capacity of the catalyst 32. In particular, in the present embodiment, the power that is the product of the warm-up speed Ne1 and the warm-up torque Te1 is set to a value at which work performed on the drive wheels by the internal combustion engine 10 can be ignored.

  On the other hand, when it is determined that the temperature Tc of the catalyst 32 is equal to or higher than the threshold value Tcref (S16: YES), the control device 50 ends the ignition timing retard control (S24). When the retard control of the ignition timing is finished, the control device 50 sets the ignition timing to a timing that is advanced as much as possible within a range in which knocking does not occur. Specifically, when the control device 50 finishes the retard control of the ignition timing, the control device 50 gradually sets the ignition timing to the advanced timing within a range where knocking does not occur by gradually operating the ignition timing to the advanced angle side. Migrate to

  Subsequently, the control device 50 determines whether or not the sum of the upper limit value of the output of the battery 44 and the power of the internal combustion engine 10 set when the catalyst 32 is warmed up (warm-up power Pset) is equal to or greater than the required output. Judgment is made (S26). This process is for determining whether or not the output of the internal combustion engine 10 can be set to the warm-up power Pset. Here, the warm-up power Pset is set to a value larger than the product of the warm-up speed Ne1 and the warm-up torque Te1. This is a setting for using the torque of the internal combustion engine 10 for traveling or charging the battery 44 because the catalyst 32 is partially activated. However, the warm-up power Pset is set to a value commensurate with the exhaust gas purification capacity of the catalyst 32.

  When the control device 50 determines that the sum of the upper limit value of the output of the battery 44 and the warm-up power Pset is equal to or greater than the required output (S26: YES), the command value of the output to the internal combustion engine 10 (output command value Pe). *) Is the warm-up power Pset (S28). As a result, the output of the internal combustion engine 10 is used for driving power and charging the battery 44 while being limited. The control device 50 sets the speed command value Ne * and the torque command value Te * so that the product thereof becomes the warm-up power Pset (S30). Here, each of the speed command value Ne * and the torque command value Te * is set so that the fuel consumption is minimized among those satisfying the warm-up power Pset.

  In contrast, when a negative determination is made in step S20 or step S26, control device 50 sets output command value Pe * to a value obtained by subtracting the upper limit value of the output of battery 44 from the requested output (S32). This is for satisfying the required output using the output of the internal combustion engine 10. Then, the control device 50 sets the speed command value Ne * and the torque command value Te * so that their product becomes the output command value Pe * set in step S32 (S34).

In addition, when the process of step S22, S30, S34 is completed, or when it makes a negative determination in step S10, the control apparatus 50 once complete | finishes this series of processes.
The control device 50 makes the valve timing of the intake valve 16 and the valve timing of the exhaust valve 26 variable by operating the intake side variable mechanism 34 and the exhaust side variable mechanism 36 in accordance with the operating region of the internal combustion engine 10. Here, as a parameter for specifying the operation region, for example, a parameter having a correlation with the rotational speed or the torque of the internal combustion engine 10 is used. Examples of parameters having a correlation with torque include an accelerator pedal operation amount, an intake throttle valve opening degree, an intake air amount, and a load factor.

  When performing the process of making the valve timing of the intake valve 16 and the valve timing of the exhaust valve 26 variable, the control device 50 uses an Atkinson cycle that makes the expansion ratio higher than the compression ratio as much as possible in order to reduce the fuel consumption. Realize. Specifically, by delaying the valve opening timing of the intake valve 16, the valve closing timing is delayed with respect to the timing at which the piston 22 reaches the bottom dead center BDC. Thereby, the compression ratio can be lowered without lowering the expansion ratio. However, when the catalyst 32 is warmed up, the valve timing is set from a viewpoint different from the reduction in fuel consumption. Next, this will be described with reference to FIG. The process shown in FIG. 3 is repeatedly executed by the control device 50, for example, at a predetermined cycle.

  In this series of processes, the control device 50 first determines whether or not the value of the catalyst warm-up request flag Fc is “1” (S40). When determining that the value of the catalyst warm-up request flag Fc is not “1” (S40: NO), the control device 50 sets the valve timing with the aim of reducing the fuel consumption. Specifically, as illustrated, for example, in a low load region, the valve closing timing of the intake valve 16 is delayed from the bottom dead center by delaying the valve opening timing of the intake valve 16 from the top dead center. . On the other hand, for the exhaust valve 26, the valve timing is set so that the valve opening timing is on the more advanced side than the bottom dead center and the valve closing timing is on the more retarded side than the top dead center. Thereby, a compression ratio can be reduced selectively and an expansion ratio can be made higher than a compression ratio. Note that the low load region includes a region where the output of the internal combustion engine 10 is set to the warm-up power Pset.

  When determining that the value of the catalyst warm-up request flag Fc is “1” (S40: YES), the control device 50 determines whether or not the ignition timing retardation control is being executed (S44). When the control device 50 determines that the ignition timing retarding control is being executed (S44: YES), the control valve 50 closes the intake valve 16 by delaying the opening timing of the intake valve 16 from the top dead center. Delay the timing from the bottom dead center. On the other hand, for the exhaust valve 26, the valve timing is set so that the valve opening timing is on the more advanced side than the bottom dead center and the valve closing timing is on the more retarded side than the top dead center. However, the valve opening timing of the exhaust valve 26 is set to an advance side from that shown in the case of the low load region in step S42. This is a setting aimed at reducing HC.

  On the other hand, when determining that the ignition timing retarding control is not executed (S44: NO), the control device 50 advances the valve opening timing of the intake valve 16 from the top dead center (S48). Further, the opening timing of the intake valve 16 is set to the most advanced position, and the opening timing of the exhaust valve 26 is set to the most retarded position, so that both the intake valve 16 and the exhaust valve 26 are opened. Make the period the longest.

  This treatment is for suppressing an increase in the number (PN) of the particulate matter PM. This is because the PN increases when the valve timing of the intake valve 16 and the valve timing of the exhaust valve 26 are set equal to those in step S42 and step S46 after the ignition timing retarding control is finished. Is a process provided in view of what has been found. Here, it is considered that the factor that increases PN is caused by the high temperature of the fuel adhering to the cylinder inner wall of the internal combustion engine 10. For this reason, since the combustion pressure does not increase during the ignition timing retarding control, the fuel adhering to the inner wall of the cylinder does not reach a high temperature and is unlikely to become PM. Further, since the temperature in the exhaust stroke is high during the retard control of the ignition timing, the fuel adhering to the cylinder inner wall is likely to volatilize, so that PM is not easily generated.

  On the other hand, when the retard control of the ignition timing is finished, the combustion pressure increases, so the possibility that the fuel attached to the cylinder inner wall becomes PM increases. Furthermore, since the exhaust temperature in the exhaust stroke decreases, the amount of fuel adhering to the cylinder inner wall increases.

  FIG. 4 shows the effect of reducing PN by advancing the valve opening timing of the intake valve 16 or retarding the valve opening timing of the exhaust valve 26 as the ignition timing retard control is completed. . The curve f1 shown in FIG. 4 shows the transition of PN when the opening timing of the intake valve 16 is after the top dead center, and the curves f2 and f3 are the opening timing of the intake valve 16 from the top dead center. The transition of PN when the angle is advanced is shown. In particular, the curve f3 shows the transition of the PN when the opening timing of the intake valve 16 is further advanced than the curve f2. As shown in the figure, the PN can be reduced by advancing the opening timing of the intake valve 16. The curve f4 is obtained by setting the opening timing of the intake valve 16 to be the same as that of the curve f3 and retarding the opening timing of the exhaust valve 26 from that of the curve f3.

  Here, the reason why the PN can be reduced by advancing the opening timing of the intake valve 16 with respect to the top dead center is presumed to be because the amount of fuel adhering to the inner wall of the cylinder can be reduced. That is, when the opening timing of the intake valve 16 is retarded from the top dead center, the pressure in the combustion chamber 18 decreases until the intake valve 16 opens after the piston 22 reaches the top dead center. Since it is easy, an air flow is easily generated in the combustion chamber 18. When airflow is generated, the fuel adhering to the intake passage 12 before the intake valve 16 is opened is sucked into the combustion chamber 18 when the intake valve 16 is opened, and is attached to the cylinder inner wall due to the airflow. It is assumed that it will be easier to do. On the other hand, when the opening timing of the intake valve 16 is advanced from the top dead center, the pressure in the combustion chamber 18 does not decrease when the intake valve 16 is opened. It is presumed that the adhesion of fuel to the cylinder inner wall is suppressed.

  Moreover, the reason why the PN can be reduced by expanding the overlap period in which both the intake valve 16 and the exhaust valve 26 are opened is that the temperature in the combustion chamber 18 rises due to the increase in the EGR amount. This is presumed to be due to this.

When the processing of steps S42, S46, and S48 in FIG. 3 is completed, the control device 50 once ends this series of processing.
As described above, in the present embodiment, the control device 50 advances the valve opening timing of the intake valve 16 from the top dead center when the retard control of the ignition timing is completed during the warm-up process of the catalyst 32. Therefore, suppression of PN is aimed at. Incidentally, the compression ratio increases by advancing the valve opening timing of the intake valve 16 with respect to the top dead center. For this reason, compared with the case where the valve opening timing of the intake valve 16 is retarded from the top dead center, the expansion ratio with respect to the compression ratio is lowered. For this reason, the fuel consumption reduction effect by the Atkinson cycle which makes an expansion ratio higher than a compression ratio will fall. However, the degree of reduction in the fuel consumption reduction effect in this case is compared with the case where the retard control of the ignition timing is continued in order to suppress the generation of PM while the catalyst warm-up request flag Fc is “1”. Get smaller. This is because the degree of reduction in the rate at which combustion energy is converted into rotational energy of the crankshaft 24 by retarding the ignition timing is greater than the degree of reduction in the above ratio due to the reduction in the ratio of the expansion ratio to the compression ratio. Because.

According to the present embodiment described above, the following effects can be obtained.
(1) When the catalyst warm-up request flag Fc is “1”, the opening timing of the intake valve 16 is set to be advanced from the top dead center by ending the retard control of the ignition timing. Thereby, PN can be reduced.

  (2) When the catalyst warm-up request flag Fc is “1”, the opening timing of the intake valve 16 is set to be advanced from the top dead center by ending the retard control of the ignition timing. In addition to this, the closing timing of the exhaust valve 26 is retarded. Thereby, PN can be further reduced.

  (3) When the internal combustion engine 10 is at a low temperature, the advance angle setting of the intake valve 16 is selected as the process for reducing the PN, not the retard process of the ignition timing. Thereby, the increase in the fuel consumption resulting from the process which reduces PN can be suppressed as much as possible.

<Correspondence between technical idea and embodiment>
Hereinafter, a representative correspondence relationship between the technical idea described in the above “Means for Solving the Problems” and the embodiment will be described.

Intake valve 16, variable mechanism 34, valve timing control processing unit 50, predetermined operating range ... low load operating range (including the point where the output is the warm-up power Pset), predetermined operating range As a condition ... In the process of S42 at the time of low load, the condition that the temperature of the internal combustion engine is low ... YES in S40, set before top dead center ... S48
<Other embodiments>
The above embodiment may be modified as follows.

・ "Variable mechanism"
As a variable mechanism that can set the opening timing of the intake valve 16 to both the advance side and the retard side from the top dead center, the profile of the cam that drives the intake valve 16 is fixed, and the intake valve 16 It is not limited to the shift of the valve opening amount (lift amount). For example, the cam profile may be changed. Even in this case, the valve opening timing of the intake valve 16 is retarded from the top dead center by reducing the lift amount, and the valve opening timing of the intake valve 16 is made top dead center by increasing the lift amount. If it is on the more advanced side, it is effective to make the valve opening timing of the intake valve 16 variable in the manner of the above embodiment. That is, for example, in the low load operation after the internal combustion engine 10 is warmed up, the lift amount is reduced and the valve opening timing of the intake valve 16 is set to the retard side from the top dead center. When the temperature is low, the lift amount may be increased and the valve opening timing of the intake valve 16 may be advanced from the top dead center for a predetermined period after the ignition timing retard control is finished.

・ About the valve timing control processing section
In the above embodiment, during the ignition timing retarding control, the opening timing of the exhaust valve 26 is set to the advance side compared to after the catalyst 32 is warmed up, but this is not restrictive. For example, it may be the same as the value determined according to the operating region of the internal combustion engine 10 when the ignition timing retarding control is not executed. In other words, when a positive determination is made in step S44, the process may move to step S42. Further, for example, the process of step S48 may be executed even during ignition timing retard control.

  In the above embodiment, the process of advancing the valve opening timing of the intake valve 16 from the top dead center is terminated when the catalyst warm-up request flag Fc is switched to “0”. However, the present invention is not limited to this. In short, it may be set to a timing at which the generation of PM is assumed to be suppressed when the temperature of the inner wall of the cylinder of the internal combustion engine 10 becomes high during a period in which the ignition timing is not retarded.

・ About the vehicle
For example, a parallel hybrid vehicle may be used. Even in this case, if the catalyst warm-up request flag Fc is “1”, the output of the internal combustion engine 10 is limited and the required output is covered by the motor generator 40 as shown in FIGS. It is possible to execute a process according to the process. A series hybrid vehicle may also be used. Even in this case, when starting the internal combustion engine 10 when the temperature is low, if the catalyst warm-up request flag Fc is “1” and the output of the internal combustion engine 10 is limited, FIG. 2 and FIG. The processing according to the processing shown in 3 can be executed.

  However, it is not essential to be a hybrid vehicle. For example, a vehicle in which only an internal combustion engine outputs power to the drive wheels may be used. Even in this case, in order to make the expansion ratio higher than the compression ratio at least at a low load, the opening timing of the intake valve 16 is retarded from the top dead center, and the warm-up of the internal combustion engine 10 is completed. If the ignition timing retard control is to be terminated before the ignition timing is terminated, the PM may be significantly generated after the retard control is terminated. For this reason, it is effective to advance the valve opening timing of the intake valve 16 from the top dead center even during low load operation.

“Regarding the prescribed operating range”
The low-load operation region is set as a predetermined operation region, and the valve opening timing of the intake valve 16 is not limited to the retarded side with respect to the top dead center during the low-load operation of the internal combustion engine 10. For example, even when the valve opening timing of the intake valve 16 is set to be retarded from the top dead center during high load operation, PM is generated during high load operation when the temperature of the cylinder inner wall of the internal combustion engine 10 is low. May become prominent. For this reason, if there is a period during which the shift to the high-load operation region is not performed when the temperature of the cylinder inner wall of the internal combustion engine 10 is low and the ignition timing is not retarded for any reason, during this period, the intake valve 16 It is effective to set the valve opening timing to an advance side from the top dead center.

・ "Valve timing of exhaust valves"
It is not necessary to provide a variable mechanism that makes the opening timing of the exhaust valve 26 variable.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 12 ... Intake passage, 14 ... Fuel injection valve, 16 ... Intake valve, 18 ... Combustion chamber, 20 ... Spark plug, 22 ... Piston, 24 ... Crankshaft, 26 ... Exhaust valve, 30 ... Exhaust passage, 32 ... Catalyst, 34 ... Intake side variable mechanism, 36 ... Exhaust side variable mechanism, 40 ... Motor generator, 40a ... Rotating shaft, 42 ... Inverter, 44 ... Battery, 50 ... Control device, 52 ... Temperature sensor.

Claims (1)

Applied to a spark ignition type internal combustion engine having a variable mechanism that makes the opening timing of the intake valve variable,
A retard control unit that performs retard control of the ignition timing in order to activate the catalyst provided in the exhaust passage of the internal combustion engine;
A valve timing control processing unit that controls the valve opening timing of the intake valve by operating the variable mechanism,
The valve timing control processing unit is configured to set a valve opening timing of the intake valve to a retarded angle side relative to top dead center when the internal combustion engine is in a predetermined operating range, and the internal combustion engine Even when the ignition timing is retarded and the temperature of the internal combustion engine is low, the opening timing of the intake valve is advanced from the top dead center. A control device for a spark ignition type internal combustion engine set on the side.