JP4062883B2 - In-cylinder internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technology for raising the temperature of a catalyst in a direct injection internal combustion engine, particularly in a direct injection internal combustion engine capable of adjusting the opening / closing timing of an exhaust valve and / or an intake valve.
[0002]
[Prior art]
A catalyst provided in an internal combustion engine of a vehicle has an effect of purifying harmful components (HC, CO, NOx, etc.) in exhaust gas. However, in order to obtain this exhaust gas purification effect, it is necessary that the catalyst has reached a predetermined activation temperature, and a sufficient effect cannot be obtained in a state where the catalyst temperature is low as in cold start. This is the same in a cylinder injection internal combustion engine that has been put into practical use in recent years. However, in a cylinder injection internal combustion engine, there are various catalyst temperature raising techniques that take advantage of the characteristic that the fuel injection timing can be arbitrarily controlled. Proposed.
[0003]
For example, Japanese Patent Laid-Open No. 2000-240485 discloses a technique for performing stratified combustion by injecting fuel during a compression stroke so that the air-fuel ratio is close to the stoichiometric air-fuel ratio when a temperature increase of the catalyst is required. Has been. In this technology, a region where the air-fuel ratio is rich and a region where the air-fuel ratio is rich are locally generated by stratified combustion. In the rich air-fuel ratio region, a large amount of CO, H₂In the lean air-fuel ratio region.₂Is generated. That is, according to this technology, a large amount of CO, H₂And O₂Can be supplied to the catalyst simultaneously, and CO, H on the catalyst₂And O₂Thus, the temperature of the catalyst can be efficiently raised by the heat of reaction due to the oxidation reaction.
[0004]
Further, in a cylinder injection type internal combustion engine, a technique for raising the temperature of a catalyst by injecting additional fuel during an expansion stroke after injection of main fuel is also known. The additional fuel injected during the expansion stroke does not contribute to the output of the internal combustion engine, and much of its energy becomes heat and raises the exhaust temperature. To efficiently raise the temperature of the catalyst.
[0005]
[Problems to be solved by the invention]
All of the above prior arts take advantage of the characteristics of the in-cylinder injection internal combustion engine that the fuel injection timing can be arbitrarily controlled, and control the combustion state of the internal combustion engine by the fuel injection timing to increase the temperature of the catalyst. . However, parameters for controlling the combustion state of the internal combustion engine include ignition timing, exhaust valve opening / closing timing, and intake valve timing in addition to the fuel injection timing. Therefore, it is considered that more efficient temperature rise control of the catalyst can be achieved by controlling the combustion state of the internal combustion engine using not only the fuel injection timing but also control parameters other than these fuel injection timings.
[0006]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a direct injection internal combustion engine that can efficiently raise the temperature of a catalyst.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the direct injection internal combustion engine of the present invention executes the following temperature increase control by the control means when the temperature increase of the catalyst provided in the exhaust passage and purifying the exhaust gas is required. It is characterized by that. That is, when the temperature of the catalyst is required to be raised, the fuel is injected into the combustion chamber during the compression stroke by driving the fuel injection means so that the air-fuel ratio is close to the stoichiometric air-fuel ratio or slightly leaner than the stoichiometric air-fuel ratio. In addition to direct injection, the valve timing adjustment means is driven to reduce the overlap between the exhaust valve and the intake valve during the normal operation, and the ignition timing by the ignition means is set after the top dead center. Yes.
[0008]
Normally, the retarded ignition timing can be expected to increase the exhaust temperature due to afterburning combustion. However, if the ignition timing is too late, combustion becomes unstable and drivability such as torque fluctuations deteriorates. There is a fear. However, in the cylinder injection internal combustion engine of the present invention, stratified combustion with a high combustion speed is realized by injecting fuel during the compression stroke, thereby improving combustion stability. In addition, the internal EGR of the internal combustion engine is reduced by reducing the overlap of the valve opening period, thereby improving the combustion stability. Therefore, even when the ignition timing is largely retarded and set after the top dead center as described above, the exhaust temperature is reliably increased by ensuring stable post-combustion combustion, and the CO, H generated by the compression stroke injection₂And surplus O₂In combination with the reaction on the catalyst, the temperature of the catalyst can be raised efficiently.
[0009]
Note that when the temperature of the catalyst is required to be raised, the temperature of the catalyst is not more than the activation temperature, such as when idling or lean operation continues for a certain period of time in addition to the cold start of the internal combustion engine. For example, when it is reduced or is in a situation where it is likely to decrease. The determination of whether or not there is a temperature increase request may be performed by, for example, detecting or estimating the catalyst temperature and determining that there is a temperature increase request when the catalyst temperature is equal to or lower than a predetermined temperature. The type of the catalyst is not limited, and an occlusion type NOx catalyst, a selective reduction type NOx catalyst, or the like can be applied in addition to a three-way catalyst. Further, the position of the catalyst is not limited, and it may be an underfloor catalyst or a proximity catalyst.
[0010]
If the air-fuel ratio (A / F) at the time of temperature increase control is too rich, the degree of incomplete combustion is too high and a large amount of unburned HC is generated, and the cause of smoldering of the spark plug as the ignition means Therefore, there is a risk of causing smoke. On the other hand, when the amount is too lean, the amount of CO generated is insufficient, and the fuel consumption is deteriorated and the drivability is reduced. Therefore, the air-fuel ratio (A / F) at the time of temperature rise control is preferably set in the range of 14 to 18, more preferably in the range of 14.5 to 16. Similarly, the air-fuel ratio in the rich region that is locally generated around the ignition means is preferably in the range of 8-10. Further, the air-fuel ratio control may be open loop control, but more preferably, an O 2 installed upstream of the catalyst.₂When the sensor is activated, feedback control of the air-fuel ratio is performed.
[0011]
Further, the valve timing adjusting means may adjust the opening / closing timing of the intake valve or may adjust the opening / closing timing of the exhaust valve. Further, the opening / closing timing of both the intake / exhaust valves may be adjusted. The valve timing adjusting mechanism may be any mechanism that can change at least the valve timing, such as a switching type, a phase switching type, an eccentric type, or an electromagnetic valve type. Preferably, a mechanism that can continuously change the valve timing, such as a vane type timing variable mechanism, is used. In this case, it is more preferable to increase the amount of valve overlap during the temperature increase control in accordance with the degree of increase in the water temperature (or oil temperature) and catalyst temperature (or exhaust temperature) of the internal combustion engine. The valve overlap at the time of temperature increase control should be at least smaller than that during normal operation (temperature state), but the crank angle is 0 degrees or less, that is, there is no overlap or the exhaust valve is also an intake valve Alternatively, an open period may be provided. In this way, the internal EGR can be completely eliminated by providing a state in which there is no overlap.
[0012]
Further, in the compression stroke injection in the temperature increase control, preferably, the injection timing is advanced within the compression stroke range in comparison with the injection timing in the compression stroke injection during the normal operation when compared with the same load and the same rotation speed. Let By advancing the injection timing in this way, fuel can be injected when the combustion chamber space is relatively wide, and it becomes possible to promote fuel diffusion and further improve combustion stability. In addition, the generation of smoke can be suppressed by ensuring a sufficient atomization time for the injected fuel.
[0013]
The ignition timing is preferably set in a range of 30 degrees from the top dead center. More preferably, the ignition timing is set in a range of 5 to 20 degrees after top dead center. By setting the ignition timing within such a range, the exhaust gas temperature can be raised without causing deterioration of fuel consumption or drivability. Furthermore, it is also preferable to increase the amount of intake air in accordance with the retarded timing of the ignition timing in order to compensate for the decrease in output due to the retarded ignition timing.
[0014]
In the above-described cylinder injection internal combustion engine, more preferably, the ignition timing is changed from the top dead center to the top dead center at a predetermined time after the start of the temperature raising control (air-fuel ratio, fuel injection timing, and valve opening period). With respect to the overlap, the control means is configured to maintain the temperature rise control setting. In the above temperature increase control, CO, H by supply of high-temperature exhaust gas by retarding the ignition timing and compression stroke injection₂And surplus O₂However, if the catalyst temperature rises to a certain level and even a part of the catalyst is activated, then CO, H by compression stroke injection₂And surplus O₂The catalyst can be sufficiently heated to the activation temperature only by supplying the catalyst. Therefore, by changing (advancing) the ignition timing from the top dead center to the top dead center after the start of the temperature raising control in this way, it is possible to suppress a decrease in fuel consumption due to the retard of the ignition timing. become.
[0015]
The predetermined time point at which the ignition timing is changed from the top dead center to the top dead center is preferably the time when the catalyst temperature reaches the predetermined temperature. The catalyst temperature may be detected directly from the catalyst, or may be estimated from the exhaust temperature that can be detected by a high temperature sensor. Further, the ignition timing may be changed when the cooling water temperature (or oil temperature) of the internal combustion engine reaches a predetermined temperature. Further, the relationship between the elapsed time from the start of the temperature increase control and the catalyst temperature is obtained in advance by experiments or the like, and a predetermined time (the time estimated that the catalyst temperature has reached the predetermined temperature) from the start of the temperature increase control is obtained. ) May be changed at the time when elapses. In this case, the ignition timing may be changed stepwise from the top dead center to the top dead center, but preferably gradually from the top dead center to the top dead center (more preferably continuously). Advance the ignition timing. More preferably, the ignition timing is advanced in accordance with the detected or estimated catalyst temperature (or the elapsed time from the start of the temperature increase control or the water temperature).
[0016]
  Further, prior to the execution of the temperature increase control, the control means is configured to execute the following temperature increase start control (first and second temperature increase start control).The
  First, in the first temperature increase start control, when the temperature increase of the catalyst is required, the fuel injection means is driven for a predetermined period to inject fuel in the intake stroke prior to the execution of the temperature increase control. At the same time, the ignition timing by the ignition means is retarded from that during normal operation. In this way, during the first predetermined period, by performing the intake stroke injection with a small amount of CO generated, the ignition timing is retarded from that during normal operation, so that the CO emission amount can be reduced and the activation of the catalyst can be activated early. Can be achieved. In this case, preferably, the overlap of the valve opening period between the exhaust valve and the intake valve is made smaller than that during normal operation.
[0017]
  Further, in the second temperature increase start control, when the temperature increase of the catalyst is required, the fuel injection means is driven for a predetermined period before the temperature increase control is executed, and the main fuel is being compressed during the compression stroke. After the fuel is injected, additional fuel is injected after the expansion stroke. In this way, the temperature of the catalyst is increased to some extent by so-called two-stage combustion of the main fuel and the additional fuel, and then the temperature increase control is executed, so that the catalyst can be efficiently heated while reducing the CO emission amount. Is possible. In this case, preferably, the overlap of the valve opening period between the exhaust valve and the intake valve is made smaller than that during normal operation. Further, it is preferable that the ignition timing is retarded from that during normal operation. Further, the injection timing of the additional fuel is preferably after the middle stage of the expansion stroke.
  Moreover, it is preferable to provide a reaction type exhaust manifold having a volume part for positively interfering with the exhaust gas discharged from the combustion chamber.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the outline of the direct injection internal combustion engine according to the first embodiment of the present invention will be described. The direct injection internal combustion engine includes intake, compression, expansion, and exhaust strokes in one operation cycle. The cycle engine is a spark ignition type and is configured to be able to directly inject fuel into the combustion chamber. More specifically, the direct injection internal combustion engine is configured as shown in the schematic configuration diagram of FIG.
[0019]
As shown in FIG. 1, an intake passage 4 and an exhaust passage 5 are connected to a cylinder head 2 of an in-cylinder injection internal combustion engine (hereinafter referred to as an engine) 1 so as to communicate with a combustion chamber 3. The intake passage 4 and the combustion chamber 3 are controlled to communicate with each other by an intake valve 6, and the exhaust passage 5 and the combustion chamber 3 are controlled to communicate with each other by an exhaust valve 7. Among these, the intake valve 6 is provided with a valve timing adjusting device 10 that variably adjusts the opening / closing timing of the intake valve 6. Since the mechanism of the valve timing adjusting device (valve timing adjusting means) 10 is well known, detailed description thereof is omitted here. For example, the vane rotor is rotated in a housing of a timing pulley connected to a crankshaft via a timing belt. The intake camshaft is connected to the vane rotor. The hydraulic pressure applied to the vane rotor is controlled to adjust the phase of the intake camshaft with respect to the timing pulley so that the opening / closing timing of the intake valve 6 can be adjusted continuously.
[0020]
The cylinder head 2 is provided with a fuel injection valve (fuel injection means) 9 for each cylinder. The fuel injection valve 9 is arranged so that its opening faces the combustion chamber 3 so that fuel can be directly injected into the combustion chamber 3. The fuel injection valve 9 is supplied with fuel pressurized by a low pressure fuel pump and a high pressure fuel pump (not shown). Further, a spark plug (ignition means) 8 is provided at the center of the top of the combustion chamber 3 of each cylinder of the cylinder head 2.
[0021]
The intake passage 4 is provided with an intake manifold 11 for introducing intake air into the combustion chamber 3 of each cylinder. The cylinder head 2 is provided with an intake port relatively upright with respect to the combustion chamber 3 for each cylinder, and the intake manifold 11 is connected to the cylinder head 2 so as to communicate with each intake port. A throttle valve 12 for adjusting the amount of intake air is provided upstream of the intake manifold 11.
[0022]
On the other hand, the exhaust passage 5 is provided with an exhaust manifold 17 that collects exhaust gases discharged from the combustion chambers 3 of the respective cylinders. The cylinder head 2 is provided with an exhaust port in a relatively horizontal direction for each cylinder, and the exhaust manifold 17 is connected to the cylinder head 2 so as to communicate with each exhaust port. As the exhaust manifold 17, a dual type exhaust manifold is employed in order to prevent interference of exhaust gas discharged from the combustion chamber 3 of each cylinder and improve engine output. Further, a catalyst device 18 and a muffler (not shown) are provided below the vehicle floor on the downstream side of the exhaust manifold 17. The catalyst device 18 is a device that purifies harmful components (CO, unburned HC, NOx) in the exhaust gas, and has a structure in which the three-way catalysts 18B, 18C are arranged upstream and downstream of the storage-type NOx catalyst 18A. .
[0023]
Further, an electronic control unit (ECU) 30 as a control means for controlling the engine 1 is provided in the vehicle interior. The ECU 30 includes an input / output device, a ROM, a RAM, a CPU, a timer counter, and the like, and performs overall control of the engine 1 based on detection information from various sensors connected to the input side.
As a sensor connected to the input side of the ECU 30, first, in the intake passage 4, a throttle position sensor (TPS) 20 for detecting the opening θth of the throttle valve 12 is attached to the portion where the throttle valve 12 is disposed. ing. Further, the exhaust passage 5 has O 2 in the upstream portion of the catalyst device 18.₂A sensor 21 and a high temperature sensor 22 are provided. O₂The sensor 21 is a sensor for detecting the oxygen concentration in the exhaust gas, and has a characteristic that its output changes greatly with the stoichiometric air-fuel ratio (stoichio) as a boundary. The high temperature sensor 22 is a sensor that detects the temperature of the exhaust gas. Further, as other sensors, a water temperature sensor 23 for detecting the coolant temperature WT of the engine 1, a crank angle sensor 24 for outputting a signal in synchronization with rotation of the crankshaft, an accelerator opening sensor and an air flow sensor (not shown). Etc. are provided. The signal from the crank angle sensor 24 is used for calculating the engine speed Ne.
[0024]
On the other hand, an ignition plug 8, a fuel injection valve 9, a valve timing adjusting device 10 and the like are connected to the output side of the ECU 30. The ECU 30 determines the ignition timing of the spark plug 8, the fuel injection timing and fuel injection amount from the fuel injection valve 9, the intake valve 6 by the valve timing adjustment device 10 based on the detection information from the various sensors 20 to 24. Controls the opening and closing timing, etc.
[0025]
The fuel injection mode (fuel injection mode) of the engine 1 according to the present embodiment includes an intake stroke injection mode in which fuel is injected during the intake stroke and premixed combustion is performed, and fuel is injected during the compression stroke. Two modes having different fuel injection timings in the compression stroke injection mode in which stratified combustion is performed are provided. More specifically, as the intake stroke injection mode, O₂Intake air O that is feedback-controlled using the signal from the sensor 21 so that the air-fuel ratio becomes stoichiometric.₂-F / B mode, intake lean mode in which open-loop control is performed to obtain a leaner air-fuel ratio (lean air-fuel ratio) than stoichio, and open-loop control in which a rich air-fuel ratio (rich air-fuel ratio) is provided. An intake O / L mode is provided. On the other hand, the compression stroke injection mode includes a compression lean mode in which the open loop control is performed so that the air / fuel ratio is further leaner than that in the intake lean mode, and a slightly lean air / fuel ratio (A / F = 15 to 16) that is slightly leaner than stoichiometric. A compressed light lean mode (compressed S / L mode) for open loop control is provided.
[0026]
Of the above-described injection modes, the intake stroke injection mode and the compression lean mode are used for fuel injection control during normal times, and the ECU 30 responds to the operating state of the engine 1 determined by the accelerator opening and the engine rotational speed Ne. Thus, an appropriate fuel injection mode is selected. On the other hand, the compression S / L mode is used for fuel injection control during temperature increase control, which will be described later. The temperature increase control is a control method of the engine 1 that is selected when a temperature increase of the catalyst device 18 is required, that is, in a situation where the temperature of the catalyst device 18 is lowered, and the engine 1 according to the present embodiment. The ECU 30 is realized by comprehensively controlling the ignition timing of the spark plug 8 and the opening / closing timing of the intake valve 6 by the valve timing adjusting device 10 in addition to the fuel injection mode.
[0027]
Hereinafter, the temperature rise control according to the first embodiment of the present invention will be described with reference to the flowchart of FIG. 2 and the time chart of FIG. Here, temperature increase control when the engine 1 is cold-started will be described.
First, in step S10, the ECU 30 sets a timer value T used in this control routine when a start switch (for example, an ignition key) is operated to turn it on, that is, when it is determined that the engine 1 has started. Reset to 0 to start counting [ie, timer on, see FIG. 3 (d)]. In step S20, it is determined that the engine rotational speed Ne has reached a predetermined value Ne0 (Ne0> idle rotational speed). When the start determination is completed, the process proceeds to the next step S30. As shown in FIG. 3A, after the engine 1 is started, until the engine speed Ne reaches a predetermined value Ne0, the fuel injection mode is the intake O / L mode to supply sufficient fuel for starting. Selected.
[0028]
In step S30, the ECU 30 determines whether or not the temperature increase control may be executed. Specifically, the cooling water temperature (simply referred to as the water temperature) WT, the engine rotational speed Ne, the target average effective pressure Pe (estimated from the accelerator opening and the engine rotational speed Ne), and the vehicle speed V respectively correspond to predetermined values WT1, Ne1. , Pe1, V1 or less. Under the condition that any one of the engine rotational speed Ne, the target average effective pressure Pe, and the vehicle speed V is high, the operating state of the engine 1 is out of the compression stroke injection region and can be regarded as a normal traveling state where the exhaust temperature is high. The temperature of the catalyst device 18 can be increased without using the temperature increase control. Conversely, if the temperature increase control is executed, the exhaust purification catalyst device 18 may be excessively heated. Further, it is determined whether or not the coolant temperature WT detected by the water temperature sensor 23 is equal to or lower than a predetermined value, that is, the warm-up temperature WT1 at which the engine 1 is warmed up. This is to prevent temperature.
[0029]
Therefore, when any of the water temperature WT, the engine rotational speed Ne, the target average effective pressure Pe, and the vehicle speed V is larger than the corresponding predetermined values WT1, Ne1, Pe1, and V1 (No route), the ECU 30 controls the temperature increase. In step S40, the normal control is executed. That is, the fuel injection mode, the ignition timing, and the intake valve 6 opening / closing timing corresponding to the operating state of the engine 1 are selected. On the other hand, when the water temperature WT, the engine rotational speed Ne, the target average effective pressure Pe, and the vehicle speed V are equal to or less than the corresponding predetermined values WT1, Ne1, Pe1, V1 (Yes route) [FIG. 3 (h)], the process proceeds to the next step S50, and the temperature rise control is executed.
[0030]
As described above, the temperature raising control is realized by the overall control of the fuel injection mode, the ignition timing, and the opening / closing timing of the intake valve 6. Specifically, the ECU 30 selects the compression S / L mode as the fuel injection mode, and retards the ignition timing after the compression top dead center (see FIGS. 3A and 3B). Further, as shown in FIG. 4, the opening / closing timing of the intake valve 6 is retarded so that the overlap (valve overlap) of the valve opening period between the exhaust valve 7 and the intake valve 6 is smaller than that during normal operation [FIG. 3 (c)].
[0031]
When the catalyst temperature is low and the purification capacity of the catalyst device 18 is low as in the cold start, it is more effective to reduce the unburned HC by making the air-fuel ratio lean as much as possible within a range where the combustion does not deteriorate. At that time, the compression stroke injection is faster than the intake stroke injection because of the stratified combustion, and the combustion stability is excellent, and the drivability is also good. In addition, when the compression stroke injection is performed by controlling the air-fuel ratio to near the stoichio or slightly leaner than the stoichiometric air-fuel ratio, the rich region where the fuel concentration is extremely high and the lean region where the fuel concentration is low. A region is formed in the combustion chamber 3. In the rich region, oxygen is locally insufficient, so incomplete combustion occurs and a relatively large amount of CO, H₂O, which does not contribute to combustion in the lean region₂Is surplus O₂As many will exist.
[0032]
Therefore, by selecting the compression S / L mode as the fuel injection mode as described above, the highly reactive CO, H₂And surplus O₂Can be simultaneously supplied to the catalyst device 18 via the exhaust passage 5, and CO, H due to an oxidation reaction in the exhaust passage 5 and the catalyst device 18.₂And O₂The temperature of the catalyst device 18 is increased by the reaction heat. If the air-fuel ratio is too rich, the degree of incomplete combustion is too high and a large amount of unburned HC is generated, which may cause smoldering of the spark plug 8 and generate smoke. Conversely, if the air-fuel ratio is too lean, CO, H₂As a result, the generation amount of the fuel becomes insufficient, and the fuel consumption deteriorates and the drivability decreases. Therefore, the air-fuel ratio in the temperature rise control is preferably set in the range of 14 to 18, more preferably in the range of 14.5 to 16. The air-fuel ratio in the rich region that is locally generated around the spark plug 8 is preferably in the range of 8-10.
[0033]
Further, the ECU 30 selects the compression S / L mode as the fuel injection mode, and at the same time, retards the ignition timing until after the compression top dead center. In this way, the ignition timing is retarded until after the compression top dead center, so that sufficient afterburning in the expansion stroke becomes possible, and the temperature of the catalyst device 18 is more quickly raised by the rise in the exhaust temperature due to afterburning. It will be illustrated. In particular, CO, H₂And O₂When the catalysts 18A to 18C are not activated at all or the degree of activation is low, it takes time until the catalysts 18A to 18C are activated, but the ignition timing is increased as described above. The exhaust temperature can be increased by being retarded until after the dead center, and the catalysts 18A to 18C (particularly 18B) can be sufficiently heated and activated. As a result, CO, H supplied by fuel injection in the compressed S / L mode₂And O₂Can be effectively reacted on the catalysts 18A to 18C (especially 18B), and the heat of reaction enables further early activation of the catalysts 18A to 18C (especially 18B).
[0034]
Here, FIG. 5 shows the time variation (a) of the temperature Tex at the inlet and the center of the three-way catalyst 18B in the catalytic device 18 after the cold start, NOx purification efficiency (b), CO purification efficiency (c ), And the time variation of the HC purification efficiency (d), when the above temperature increase control is executed (solid line) and when the normal control is executed without executing the temperature increase control (dashed line) It is shown in comparison. Since the catalyst device 18 according to the present embodiment is far from the main body of the engine 1, the exhaust temperature tends to decrease before the exhaust gas reaches the catalyst device 18, and the dual type exhaust manifold 17 has a small amount of exhaust interference, so The exhaust gas temperature is likely to be lowered because of the small reaction and the large heat capacity and the large surface area (heat radiation area). However, even when such a structure is disadvantageous for maintaining the exhaust temperature, as shown in FIGS. 5 (a) to 5 (d), when the above-described temperature increase control is executed at the cold start. The catalyst device 18 can be raised to the activation temperature at an early stage, and the purification efficiency of harmful substances (HC, CO, and NOx) can be quickly increased.
[0035]
Further, when the ignition timing is retarded until after the compression top dead center as described above, normally, combustion becomes unstable and drivability such as torque fluctuation is deteriorated. Performs the compression stroke injection with retarded ignition timing and high combustion stability. Further, as described above, the internal EGR of the engine 1 is reduced by reducing the overlap of the valve opening period of the exhaust valve 7 and the intake valve 6 as compared with the normal operation, thereby improving the combustion stability. ing. Therefore, even when the ignition timing is greatly retarded until after the compression top dead center, drivability is not deteriorated due to a decrease in combustion stability. Further, the improvement in combustion stability by reducing the overlap in the valve opening period compensates for the deterioration in combustion stability associated with leaning, and therefore leaning can be achieved more easily.
[0036]
That is, according to the temperature increase control according to the present embodiment, the fuel is injected during the compression stroke so that the air-fuel ratio becomes near the stoichiometric or the lean lean air-fuel ratio, and the ignition timing is set after the compression top dead center. In addition, the synergistic effect of reducing the overlap of the valve opening period between the exhaust valve 7 and the intake valve 6 as compared with that in the normal operation can efficiently raise the temperature of the catalyst device 18 without deteriorating the combustion stability. The effect of being able to be obtained.
[0037]
The ignition timing is specifically set within a range of 0 to 30 degrees after compression top dead center. The reason why the temperature does not exceed 30 degrees after the compression top dead center is that, if it exceeds 30 degrees after the compression top dead center, the combustion stability is deteriorated. Preferably, the range is 5 to 20 degrees after compression top dead center. By setting this range, a sufficient exhaust gas temperature raising effect can be obtained. Further, the overlap of the valve opening period of the exhaust valve 7 and the intake valve 6 should be at least smaller than the set amount at the same load and the same rotational speed in the warm state (during normal operation). If possible, the setting is preferably 0 degree or less. As long as there is an overlap, there is some internal EGR that is a factor of lowering the combustion stability. In particular, when a negative pressure is generated in the intake passage 4, if there is a slight overlap, a negative pressure is present. The exhaust gas that should be drawn to the exhaust passage 5 and remain in the combustion chamber 3 as internal EGR. Therefore, by setting the overlap to 0 degrees or less as described above, it is possible to completely eliminate internal EGR and further improve the combustion stability.
[0038]
When the temperature raising control is executed as described above to raise the temperature of the catalyst device 18, the ECU 30 next performs a process of step S60. In step S60, the ECU 30 determines whether or not the timer has counted a predetermined timer time T1, that is, whether or not the temperature increase control has been continued beyond the predetermined timer time T1. The predetermined timer time T1 is set in advance by an experiment or the like until, for example, it is estimated that the temperature of the catalyst device 18 has been raised to a predetermined temperature close to the activation temperature after the start of cooling. ing. When the timer does not reach the predetermined timer time T1 (No route), the ECU 30 continues the temperature increase control again in step S50 through the process of step S30. On the other hand, when the timer counts the predetermined timer time T1 (Yes route), the process of the next step S70 is performed. That is, in step S70, the ECU 30 ends the temperature raising control (see FIGS. 3A to 3C), and the fuel injection mode, the ignition timing, and the intake valve 6 according to the operating state of the engine 1 are determined. Select the opening / closing timing and perform normal control again.
[0039]
Next, a second embodiment of the present invention will be described with reference to FIGS.
This embodiment is intended to improve the control accuracy in the temperature raising control as compared with the first embodiment. For this reason, in this embodiment, as a fuel injection mode (fuel injection mode) of the engine 1, in addition to each fuel injection mode similar to the first embodiment, O as one of the compression stroke injection modes.₂Compression O that feedback-controls the air-fuel ratio to be stoichiometric using a signal from the sensor 21₂-F / B mode is provided. The ECU 30 performs this compression O₂The -F / B mode is used for fuel injection control during temperature raising control together with the compression S / L mode. That is, the present embodiment is different from the first embodiment in the method of temperature increase control, and hereinafter, the method of temperature increase control that is the difference will be described mainly. The configuration of the engine (cylinder injection type internal combustion engine) 1 is the same as that of the first embodiment, and therefore the description thereof will be omitted here. The same reference numerals as those of the first embodiment will be used hereinafter.
[0040]
As shown in the flowchart of FIG. 6, the present embodiment is characterized in that the processes of steps S51 to S53 are performed instead of the step of executing the temperature increase control (step S50) according to the first embodiment. That is, in this embodiment, the execution step of temperature rising control is comprised by step S51-S53. The other steps are the same as those in the first embodiment, and the description thereof is omitted here.
[0041]
First, in step S30, when it is determined that all of the water temperature WT, the engine speed Ne, the target average effective pressure Pe, and the vehicle speed V are equal to or less than the corresponding predetermined values WT1, Ne1, Pe1, and V1 (Yes route) [FIG. (F) to FIG. 7 (i)], the ECU 30 proceeds to the next step S51, where O₂It is determined whether or not the sensor 21 is in an activated state. O₂Since the sensor 21 is configured to exhibit its performance at a certain high temperature, it cannot perform proper feedback control in a low temperature state. So, for example, O₂By comparing the output voltage at the rich air-fuel ratio of the sensor 21 with a predetermined activation determination voltage, O₂The sensor 21 determines the activation state. And O₂When it is determined that the sensor 21 is not yet activated (off) (No route) [see FIG. 7A], the process proceeds to step S52.
[0042]
In step S52, as in the first embodiment, the ECU 30 selects the compression S / L mode as the fuel injection mode, retards the ignition timing after compression top dead center, and sets the opening / closing timing of the intake valve 6 to the exhaust valve 7 And the intake valve 6 are retarded so that the overlap of the valve opening period is smaller than that during normal operation (see FIGS. 7B to 7D). On the other hand, O₂When it is determined that the sensor 21 is in an activated state (ON) (Yes route) [see FIG. 7A], the process proceeds to step S53.
[0043]
In step S53, the ECU 30 delays the ignition timing after the compression top dead center, and the opening / closing timing of the intake valve 6 is smaller in the overlap of the opening period of the exhaust valve 7 and the intake valve 6 than in the normal operation. With the retarded angle, the fuel injection mode is compressed O₂-The F / B mode is selected (see FIGS. 7B to 7D). In this way, by executing the compression stroke injection while performing feedback control so that the air-fuel ratio becomes stoichiometric, a relatively large amount of CO, H is obtained by stratified combustion as in the case where the compression S / L mode is selected.₂And surplus O₂Can be generated. Furthermore, since the feedback control is performed, the air-fuel ratio can be set accurately as compared with the open loop control in the compression S / L mode. Therefore, according to the present embodiment, the control accuracy can be increased as compared with the first embodiment, and the temperature of the catalyst device 18 can be raised more efficiently. Although not shown in the flowchart, the normal control is also performed in step S40.₂After it is determined that the sensor 21 is in the activated state, the intake O / L mode is changed to the intake O / L mode.₂-Switch the fuel injection mode to F / B mode.
[0044]
Compression O₂In the -F / B mode, feedback control is usually performed so that the air-fuel ratio becomes stoichiometric, but by changing the setting of the feedback gain (for example, integral gain or proportional gain in the case of PI control), the lean lean Feedback control may be performed using the air-fuel ratio as the target air-fuel ratio. In the compression stroke injection, a relatively large amount of H is contained in the exhaust gas due to local incomplete combustion accompanying stratified combustion.₂Will occur, but this H₂Is O₂Than O₂Since the speed of diffusing the coating layer covering the Pt electrode of the sensor 21 is high, O₂Concentration is detected to be smaller than actual and O₂The output of the sensor 21 is slightly rich. Therefore, even when feedback control is performed using stoichio as the target air-fuel ratio, the actual air-fuel ratio is naturally controlled to a slightly lean air-fuel ratio that is slightly leaner than stoichio.
[0045]
In FIG.₂The sensor 21 is disposed on the upstream side of the catalyst device 18, but may be disposed on the downstream side of the catalyst device 18, and may be disposed on both the upstream and downstream sides. In addition, O₂As the sensor 21, a linear air-fuel ratio sensor can also be used. In this case, feedback control can be executed with any air-fuel ratio as the target air-fuel ratio.
[0046]
Next, a third embodiment of the present invention will be described with reference to FIGS.
The present embodiment is intended to improve the fuel efficiency in the temperature raising control as compared with the first embodiment, and the temperature raising control method is different from the first embodiment. Hereinafter, the method of temperature increase control which is this difference will be described mainly. The configuration of the engine (in-cylinder injection type internal combustion engine) 1 is the same as that of the first embodiment, and thus the description thereof will be omitted. Hereinafter, the same reference numerals as those of the first embodiment are used.
[0047]
As shown in the flowchart of FIG. 8, the present embodiment is characterized in that the temperature increase control is executed in two stages (step S50, step S57). First, the execution process (step S50) of the first stage temperature increase control (first temperature increase control) is the same as that in the first embodiment, and the ECU 30 selects the compression S / L mode as the fuel injection mode and performs ignition. The timing is retarded after compression top dead center, and the opening / closing timing of the intake valve 6 is retarded so that the overlap of the opening period of the exhaust valve 7 and the intake valve 6 is smaller than that during normal operation [FIG. a) to FIG. 9 (c)].
[0048]
Next, in step S54, the ECU 30 determines whether or not the timer has counted a predetermined timer time T2, that is, whether or not the first temperature increase control has been continued beyond the predetermined timer time T2 [FIG. d)]. The predetermined timer time T2 is set in advance by, for example, an experiment or the like until, for example, it is estimated that the temperature of the catalyst device 18 has been raised to a predetermined temperature by executing the first temperature increase control after the cold start. If the timer has not reached the predetermined timer time T2 (No route), the ECU 30 continues the first temperature increase control in step S50 again through step S30. On the other hand, when the timer counts the predetermined timer time T2 (Yes route), the process of the next step S55 is performed.
[0049]
In step S55, the ECU 30 determines whether or not the second-stage temperature increase control (second temperature increase control) may be executed. Specifically, as in step S30, it is determined whether or not the water temperature WT, the engine speed Ne, the target average effective pressure Pe, and the vehicle speed V are equal to or less than the corresponding predetermined values WT1, Ne1, Pe1, and V1, respectively. [Refer to Drawing 9 (e)-Drawing 9 (h)). When any of the water temperature WT, the engine rotational speed Ne, the target average effective pressure Pe, and the vehicle speed V is larger than the corresponding predetermined values WT1, Ne1, Pe1, and V1 (No route), the ECU 30 causes the second increase. The normal control is executed in step S56 without executing the temperature control. On the other hand, if all of the water temperature WT, the engine rotational speed Ne, the target average effective pressure Pe, and the vehicle speed V are equal to or less than the corresponding predetermined values WT1, Ne1, Pe1, and V1 (Yes route), the process proceeds to the next step S57. The second temperature increase control is executed. Here, the predetermined values WT1, Ne1, Pe1, and V1 used in the start determination of the first temperature rise control are also used in the start determination of the second temperature increase control, but the predetermined value WT2 different from the first temperature increase control. , Ne2, Pe2, V2 may be used.
[0050]
The second temperature raising control is realized by comprehensive control of the fuel injection mode and the opening / closing timing of the intake valve 6. Specifically, the ECU 30 selects the compression S / L mode as the fuel injection mode in the same manner as when executing the first temperature increase control, and the opening / closing timing of the intake valve 6 is the opening / closing timing of the exhaust valve 7 and the intake valve 6. The ignition timing is advanced to the top dead center in the same manner as in the normal control while the valve period is kept retarded so that the overlap of the valve period is smaller than that in the normal operation (see FIGS. 9A and 9C). [Refer FIG.9 (b)]. Here, the ignition timing is the same as that at the time of normal control before top dead center, but may be slightly retarded from that at the time of normal control while being before top dead center. This is because the compression stroke injection in the compression S / L mode is performed, so that the combustion stability is good, and the drivability is not deteriorated even if the ignition timing is somewhat retarded.
[0051]
In the first temperature rise control, high-temperature exhaust gas is supplied by retarding the ignition timing, and CO, H by compression stroke injection are used.₂And O₂However, if the catalyst temperature rises to a certain level and even a part of the catalyst device 18 is activated, then CO, H by compression stroke injection are used.₂And O₂The catalyst device 18 can be sufficiently heated to the activation temperature only by supplying the catalyst. Therefore, the ignition timing is retarded by changing (advancing) the ignition timing from the top dead center to the top dead center when the predetermined time T2 has elapsed after the start of the first temperature raising control. It is possible to suppress the accompanying reduction in fuel consumption. Therefore, according to the present embodiment, there is an effect that it is possible to raise the temperature of the catalyst device 18 while suppressing deterioration of fuel consumption more than in the first embodiment. Here, the ignition timing is changed stepwise (advanced) as the predetermined timer time T2 elapses, but the amount of retardation may be gradually decreased.
[0052]
When the second temperature raising control is executed as described above to raise the temperature of the catalyst device 18, the ECU 30 next performs a process of step S61. In step S61, the ECU 30 determines whether or not the timer has counted a predetermined timer time T3, that is, whether or not the first and second temperature raising controls have been continued beyond the predetermined timer time T3. The predetermined timer time T3 is determined in advance through experiments or the like until, for example, it is estimated that the temperature of the catalyst device 18 has been raised to a predetermined temperature close to the activation temperature by performing the first and second temperature increase control after the cold start. Is set to time. If the timer has not reached the predetermined timer time T3 (No route), the ECU 30 continues the second temperature increase control in step S57 again through the process of step S54. On the other hand, when the timer counts the predetermined timer time T3 (Yes route), the process proceeds to step S70, where the ECU 30 ends the second temperature rise control and performs normal control [FIGS. 9 (a), 9]. (See (c), FIG. 9 (d)).
[0053]
Next, a fourth embodiment of the present invention will be described with reference to FIGS.
In the present embodiment, the temperature of the catalyst is increased more efficiently than in the first embodiment by performing engine control immediately after starting more appropriately. That is, a relatively large amount of CO can be generated in the exhaust gas by performing the compression stroke injection with the air / fuel ratio in the vicinity of stoichiometric or the lean lean air / fuel ratio as in the temperature raising control of the first embodiment. Even if this is carried out in a state where the catalyst is not sufficiently activated, the produced CO may not be reacted on the catalyst and may be discharged into the atmosphere as it is. Therefore, in the present embodiment, as shown in the flowchart of FIG. 10, the catalyst is preheated by performing the following temperature rise start control (first temperature rise start control) for a predetermined time after the engine is started. We are trying to activate early. Hereinafter, temperature rise start control, which is a difference from the first embodiment, will be described mainly. Since the configuration of the engine (cylinder injection type internal combustion engine) is the same as that of the first embodiment, the same reference numerals as those of the first embodiment are used here.
[0054]
As shown in the flowchart of FIG. 10, when the start determination is completed in step S20, the ECU 30 next performs a process of step S21. In addition, the processing content of step S10, S20 is the same as that of 1st Embodiment. In step S21, the ECU 30 determines whether or not the temperature raising start control may be executed. Specifically, the water temperature WT, the engine rotational speed Ne, the target average effective pressure Pe, and the vehicle speed V are respectively equal to or less than predetermined values. [See FIG. 11 (e) to FIG. 11 (h)]. When any one of the water temperature WT, the engine rotational speed Ne, the target average effective pressure Pe, and the vehicle speed V is larger than a corresponding predetermined value (No route), the ECU 30 may overheat the exhaust purification catalyst device 18. Therefore, the temperature increase start control is not performed, and the process proceeds to step S22 to execute the normal control. On the other hand, when all of the water temperature WT, the engine rotation speed Ne, the target average effective pressure Pe, and the vehicle speed V are equal to or less than the corresponding predetermined values (Yes route), the process proceeds to step S23 and the following temperature increase start control is executed. .
[0055]
In the temperature rise start control, the ignition timing is retarded from the normal operation in the state where the intake O / L mode is selected as the fuel injection mode. At this time, the opening / closing timing of the intake valve 6 may be maintained during normal operation, but is preferably retarded so that the overlap of the valve opening period between the exhaust valve 7 and the intake valve 6 is smaller than that during normal operation [ FIG. 11 (a) to FIG. 11 (c)]. The air-fuel ratio is preferably set in the vicinity of stoichiometric or slightly lean air-fuel ratio. Since the intake O / L mode is intake stroke injection, the amount of CO generated is small, and the exhaust temperature can be increased by afterburning by retarding the ignition timing from that during normal operation. Therefore, immediately after starting the engine in which the catalytic device 18 is not activated, the ignition timing is retarded from the normal operation while performing the intake stroke injection in this manner, thereby reducing the CO emission amount to a certain extent. The temperature can be raised. Then, when the catalyst device 18 is activated to some extent, temperature increase control is started, and a large amount of CO, H is produced by the compression stroke injection.₂And surplus O₂By supplying the catalyst, the temperature of the catalyst device 18 can be raised more efficiently by the reaction heat accompanying the oxidation reaction on the catalysts 18A to 18C. It should be noted that the ignition timing at the time of intake stroke injection need only be retarded at least as compared with that during normal operation, and need not be retarded until after top dead center as in the temperature rise control. In this control, combustion stability due to compression stroke injection cannot be obtained, but by adjusting the opening / closing timing of the intake valve 6 so that the overlap of the valve opening period is smaller than that during normal operation, the internal EGR is controlled. A certain degree of combustion stability can be ensured by the reduction.
[0056]
After executing the temperature rise start control as described above, the ECU 30 next performs a process of step S24. In step S24, the ECU 30 determines whether or not the timer has counted a predetermined timer time T4, that is, whether or not the temperature increase start control has been continued beyond the predetermined timer time T4 [see FIG. 11 (d). ]. For example, the predetermined timer time T4 is set to a time during which it is estimated that the catalyst temperature has risen to the extent that the oxidation reaction is started on the catalysts 18A to 18C of the catalyst device 18, for example. If the timer has not reached the predetermined timer time T4 (No route), the ECU 30 continues the temperature rise start control again in step S23, and if the timer has counted the predetermined timer time T4 (Yes route), The temperature increase start control is terminated and the process proceeds to step S30.
[0057]
Since the processing content after step S30 is the same as that of the first embodiment, the description thereof is omitted here. Note that the timer time T5 of step S62 is set to a time until it is estimated here that the temperature of the catalyst device 18 has been raised to a predetermined temperature close to the activation temperature by executing the temperature rise start control and the temperature rise control. [See FIG. 11 (d)]. According to the present embodiment, the temperature of the catalyst device 18 can be increased more efficiently by executing the temperature increase start control prior to the temperature increase control, so that the timer time T5 is greater than the timer time T1 of the first embodiment. Can be set to a short time. Further, when changing the ignition timing, all of them are changed stepwise, but preferably gradually (more preferably continuously). More preferably, the ignition timing may be changed in accordance with the detected or estimated catalyst temperature (or the elapsed time from the start of control or the water temperature).
[0058]
Next, a fifth embodiment of the present invention will be described with reference to FIGS.
In the present embodiment, similarly to the fourth embodiment, the temperature of the catalyst is increased more efficiently by performing the engine control immediately after starting more appropriately. In the present embodiment, the catalyst is preheated by executing so-called two-stage combustion control (second temperature rise start control) for a predetermined time after engine startup and prior to the temperature rise control, thereby achieving early activation of the catalyst. . Hereinafter, the two-stage combustion control, which is the difference from the first embodiment, will be described mainly. Since the configuration of the engine (cylinder injection type internal combustion engine) is the same as that of the first embodiment, the same reference numerals as those of the first embodiment are used here.
[0059]
Specifically, as shown in the flowchart of FIG. 12, when the start determination is completed in step S20, the ECU 30 next performs a process of step S25. In addition, the processing content of step S10, S20 is the same as that of 1st Embodiment. In step S25, the ECU 30 determines whether or not the two-stage combustion control may be executed. Specifically, the water temperature WT, the engine rotational speed Ne, the target average effective pressure Pe, and the vehicle speed V are respectively equal to or less than the corresponding predetermined values. [See FIG. 12 (e) to FIG. 12 (h)]. When any one of the engine speed Ne, the target average effective pressure Pe, the vehicle speed V, and the water temperature WT is larger than the corresponding predetermined value (No route), the ECU 30 may overheat the exhaust purification catalyst device 18. Therefore, the two-stage combustion control is not carried out, and the routine proceeds to step S26 where the normal control is executed. On the other hand, when all of the water temperature WT, the engine rotational speed Ne, the target average effective pressure Pe, and the vehicle speed V are equal to or lower than the corresponding predetermined values (Yes route), the process proceeds to step S27 and the following two-stage combustion control is executed. .
[0060]
The two-stage combustion control is a control for performing two-stage injection of fuel for injecting additional fuel after the expansion stroke after injecting the main fuel in the compression stroke. As the injection timing of the additional combustion, it is preferable to be in the middle of the expansion stroke, particularly in the middle of the expansion stroke. Thereby, the fuel injected into the high temperature atmosphere in the expansion stroke is self-ignited, and the generation of smoke and unburned HC can be suppressed low. The main fuel amount and the additional fuel amount are adjusted so that the overall air-fuel ratio is close to stoichiometric or a slight lean air-fuel ratio. In the two-stage combustion control, the additional fuel injected during the expansion stroke is used to increase the exhaust temperature without contributing to the output of the engine 1. Therefore, immediately after starting the engine in which the catalyst device 18 is not activated, it is possible to raise the temperature of the catalyst device 18 to a certain extent by executing such two-stage combustion control.
[0061]
Then, when the catalyst device 18 is activated to some extent, temperature increase control is started, and a large amount of CO, H is produced by the compression stroke injection.₂And surplus O₂By supplying the catalyst, the temperature of the catalyst device 18 can be raised more efficiently by the reaction heat accompanying the oxidation reaction on the catalysts 18A to 18C. Also in this embodiment, the ignition timing at the time of the two-stage combustion control may be retarded from that during the normal operation, and according to this, the temperature of the catalyst device 18 can be raised more efficiently. Furthermore, by adjusting the opening / closing timing of the intake valve 6 so that the overlap during the valve opening period is smaller than that during normal operation, combustion stability can be ensured even immediately after the engine is started.
[0062]
When the two-stage combustion control is executed as described above, the ECU 30 determines whether or not the timer has counted a predetermined timer time T6 in the next step S28 [see FIG. 13 (d)]. For example, the predetermined timer time T6 is set to a time during which it is estimated that the catalyst temperature has risen to the extent that the oxidation reaction is started on the catalysts 18A to 18C of the catalyst device 18, for example, through experiments. When the timer does not reach the predetermined timer time T6 (No route), the two-stage combustion control is continued in Step S27 through Step S25, and when the timer reaches the predetermined timer time T6 (Yes route), Proceed to the next Step S30. Since the processing content after step S30 is the same as that of the first embodiment, the description thereof is omitted here. Note that the timer time T7 in step S63 is set to a time until it is estimated that the catalyst device 18 has been heated to a predetermined temperature close to the activation temperature by executing the two-stage combustion control and the temperature increase control. Yes. According to the present embodiment, the temperature of the catalyst device 18 can be increased more efficiently by executing the two-stage combustion control prior to the temperature increase control, so the timer time T7 is greater than the timer time T1 of the first embodiment. Can be set to a short time.
[0063]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, it is of course possible to make a new embodiment by appropriately combining the feature points of the above-described second to fifth embodiments.
In the above-described embodiment, the intake valve 6 includes the valve timing adjusting device 10. However, the opening / closing timing of the exhaust valve 7 may be adjusted, or the opening / closing timing of both the intake valve 6 and the exhaust valve 7 may be adjusted. May be. Furthermore, in the above-described embodiment, the amount of valve overlap at the time of temperature rise control is fixed. However, as the engine 1 warms up, the combustion stability also increases, so that the temperature of the water (or oil temperature) increases. The overlap amount may be returned to the normal amount.
[0064]
Further, the compression stroke injection in the temperature rise control (compression S / L mode and compression O₂-F / B mode) injection timing may be advanced from the injection timing of compression stroke injection during normal operation. By advancing the injection timing in this way, fuel can be injected when the space of the combustion chamber 3 is relatively wide, and there is an advantage that fuel diffusion can be promoted and combustion stability can be further improved. . Moreover, there is also an advantage that the generation of smoke can be suppressed by sufficiently securing the atomization time of the injected fuel.
[0065]
In the case where the throttle valve 12 is electronically controlled, the throttle valve 12 may be opened in accordance with the retarded degree of the ignition timing to increase the intake air amount during the temperature rise control. Since the output decreases when the ignition timing is retarded, there is an advantage that the decrease in the output due to the retard of the ignition timing can be compensated by controlling the throttle valve 12 in this way.
[0066]
Further, when the engine 1 is provided with an exhaust gas recirculation (EGR) device, it is preferable that the EGR valve is throttled or closed during temperature increase control. Since EGR is a cause of a decrease in combustion stability, there is an advantage that a decrease in combustion stability can be prevented by controlling the EGR device in this way.
In addition, the engine 1 of the above-described embodiment includes the dual type exhaust manifold 17 with less exhaust interference in order to improve the output, but has a small heat radiation area and heat capacity, which is advantageous and low in preventing the exhaust temperature from decreasing. A single exhaust manifold 17 of cost may be provided. Furthermore, you may provide the clamshell type exhaust manifold (reaction type exhaust manifold) which has the volume part for making exhaust interference actively. According to this type of exhaust manifold, the exhaust temperature can be further increased by reaction of unburned components accompanying exhaust interference inside the exhaust manifold.
[0067]
In the above-described embodiment, the end time of the temperature raising control is measured using a timer. For example, as shown in the flowchart of FIG. 14, the exhaust immediately upstream of the catalyst device 18 detected by the high temperature sensor 22. The catalyst temperature Tex is estimated from the temperature, and the temperature increase control may be terminated when the estimated catalyst temperature Tex reaches a predetermined temperature (a temperature at which it can be determined that the activity of the catalyst has become sufficient) Tex1 (step S64). . The catalyst temperature Tex is estimated by, for example, referring to a map storing the relationship between the exhaust gas temperature and the catalyst temperature Tex, using a predetermined calculation formula using the exhaust gas temperature as a parameter, The estimation may be based on the engine speed, the vehicle speed, the air-fuel ratio, and the like. Further, instead of estimating the catalyst temperature Tex from the exhaust temperature, the temperature rise control may be terminated when the coolant temperature WT (or oil temperature) detected by the water temperature sensor 23 reaches a predetermined temperature.
[0068]
Further, the present invention is not only at the time of cold start of the engine 1 but also an activated catalyst such as when idling or lean operation (especially compression lean operation with a high degree of leaning) continues for a relatively long time. The present invention can also be applied to temperature increase control such as when the temperature of the device 18 (catalysts 18A to 18C) is lowered or less than the activation temperature. In this case, as shown in the flowchart of FIG. 15, whether or not the catalyst temperature Tex estimated from the exhaust temperature detected by the high temperature sensor 22 is equal to or lower than a predetermined temperature (a temperature at which it can be determined that the catalyst activity is insufficient). Is determined (step S11). When the catalyst temperature Tex falls below the predetermined temperature Tex0 (Yes route), the process proceeds to step S30 to determine whether or not the temperature increase control can be executed, and depending on the determination result, normal control in step S40 or step S50. The temperature rise control is performed. Then, in step S65, it is determined whether or not the catalyst temperature Tex has reached the predetermined temperature Tex1, and when the catalyst temperature Tex rises to the predetermined temperature Tex1 or more (Yes route), the control before proceeding to step S71 and performing the temperature increase control. Continue driving in the state.
[0069]
【The invention's effect】
As described in detail above, the direct injection internal combustion engine of the present invention realizes stratified combustion with a high combustion speed by directly injecting fuel into the combustion chamber during the compression stroke, and overlaps the valve opening period. By reducing the internal EGR by reducing the EGR, combustion stability is improved, and even after the ignition timing is set after top dead center, stable combustion after combustion can be ensured, so that CO, generated by compression stroke injection, H₂And surplus O₂There is an effect that the temperature of the catalyst can be efficiently raised by a synergistic effect with the reaction on the catalyst.
[0070]
Also, if the ignition timing is changed from the top dead center to the top dead center at a predetermined time after the start of the temperature raising control, the fuel consumption is reduced due to the retardation of the ignition timing while the temperature of the catalyst is efficiently raised. There is an effect that it can be suppressed.
Further, prior to the execution of the temperature increase control, the first temperature increase start control for injecting fuel in the intake stroke and retarding the ignition timing from that during the normal operation is performed over a predetermined period, or the compression is performed. When the second temperature rise start control in which the additional fuel is injected after the expansion stroke after the main fuel is injected during the stroke is performed over a predetermined period, the catalyst is made more efficient while reducing the CO emission amount. There is an effect of raising the temperature well.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a direct injection internal combustion engine according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing a control routine of temperature rise control at the time of cold start according to the first embodiment of the present invention.
FIG. 3 is a time chart showing the control contents of temperature increase control shown in FIG. 2; timer value (d), water temperature (e), engine speed (f), target effective pressure (g), vehicle speed (h) And changes in the corresponding fuel injection mode (a), ignition timing (b), and overlap amount (c) are shown.
FIG. 4 is a diagram illustrating setting of an overlap amount during a valve opening period according to the first embodiment of the present invention.
FIG. 5 shows temperature rise control (a) of the catalyst temperature after cold start, together with time changes of NOx purification efficiency (b), CO purification efficiency (c), and HC purification efficiency (d). This is a comparison between the case of executing (solid line) and the case of executing normal control (dashed line).
FIG. 6 is a flowchart showing a control routine of temperature increase control according to the second embodiment of the present invention.
7 is a time chart showing the control content of temperature increase control shown in FIG.₂Sensor activation state determination (a), timer value (e), water temperature (f), engine rotation speed (g), target effective pressure (h), vehicle speed (i), and changes in time and corresponding fuel Each setting of injection mode (b), ignition timing (c), and overlap amount (d) is shown.
FIG. 8 is a flowchart showing a control routine of temperature increase control according to a third embodiment of the present invention.
FIG. 9 is a time chart showing the control contents of the temperature increase control shown in FIG. 8; timer value (d), water temperature (e), engine speed (f), target effective pressure (g), vehicle speed (h) And changes in the corresponding fuel injection mode (a), ignition timing (b), and overlap amount (c) are shown.
FIG. 10 is a flowchart showing a control routine of temperature increase control according to a fourth embodiment of the present invention.
11 is a time chart showing the control contents of the temperature raising control shown in FIG. 10; timer value (d), water temperature (e), engine speed (f), target effective pressure (g), vehicle speed (h) And changes in the corresponding fuel injection mode (a), ignition timing (b), and overlap amount (c) are shown.
FIG. 12 is a flowchart showing a control routine of temperature increase control according to the fifth embodiment of the present invention.
FIG. 13 is a time chart showing the control contents of the temperature raising control shown in FIG. 12; timer value (d), water temperature (e), engine speed (f), target effective pressure (g), vehicle speed (h) And changes in the corresponding fuel injection mode (a), ignition timing (b), and overlap amount (c) are shown.
FIG. 14 is a flowchart showing a control routine of temperature increase control according to another embodiment of the present invention.
FIG. 15 is a flowchart showing a control routine of temperature increase control according to another embodiment of the present invention.
[Explanation of symbols]
1 Engine (Cylinder injection type internal combustion engine)
2 Cylinder head
4 Intake passage
5 Exhaust passage
6 Intake valve
7 Exhaust valve
8 Spark plug (ignition means)
9 Fuel injection valve (fuel injection means)
10 Valve timing adjusting device (valve timing adjusting means)
12 Throttle valve
18 Catalytic device
18A NOx storage catalyst
18B, 18C Three-way catalyst
20 Throttle position sensor
21 O₂Sensor
22 High temperature sensor
23 Water temperature sensor
24 Crank angle sensor
30 ECU (control means)

Claims (4)

A catalyst for purifying exhaust gas provided in the exhaust passage;
Fuel injection means capable of directly injecting fuel into the combustion chamber;
Valve timing adjusting means for adjusting the opening and closing timing of the exhaust valve and / or the intake valve;
Ignition means capable of igniting the air-fuel mixture in the combustion chamber;
When temperature rise of the catalyst is required, temperature rise start control for driving the fuel injection means to inject fuel in the intake stroke and retarding the ignition timing by the ignition means from the normal operation is performed for a predetermined period. over run, then with air by driving the fuel injection means injects the fuel during the compression stroke so as to slightly lean air-fuel ratio than the stoichiometric air-fuel ratio near or stoichiometric air-fuel ratio, the valve timing control The temperature rise control is executed to reduce the overlap of the valve opening period of the exhaust valve and the intake valve from that during normal operation and set the ignition timing by the ignition means after top dead center. A cylinder injection type internal combustion engine. A catalyst for purifying exhaust gas provided in the exhaust passage;
Fuel injection means capable of directly injecting fuel into the combustion chamber;
Valve timing adjusting means for adjusting the opening and closing timing of the exhaust valve and / or the intake valve;
Ignition means capable of igniting the air-fuel mixture in the combustion chamber;
When temperature rise of the catalyst is required, temperature rise start control is executed over a predetermined period of time after the fuel injection means is driven and main fuel is injected during the compression stroke and then additional fuel is injected after the expansion stroke. Thereafter, the fuel injection means is driven to inject fuel during the compression stroke so that the air-fuel ratio is close to the stoichiometric air-fuel ratio or slightly leaner than the stoichiometric air-fuel ratio, and the valve timing adjusting means is driven. Control means for performing temperature increase control, wherein the overlap of the valve opening period of the exhaust valve and the intake valve is reduced from that during normal operation, and the ignition timing by the ignition means is set after top dead center An in-cylinder internal combustion engine characterized by comprising: 3. The in-cylinder according to claim 1, wherein the control means changes the ignition timing of the ignition means from after top dead center to before top dead center at a predetermined time after the start of temperature rise control. Injection type internal combustion engine. And wherein the <br/> that includes a reactive exhaust manifold having a volume portion for interfering actively the exhaust gas discharged from the combustion chamber, any one of claims 1 to 3 A cylinder injection type internal combustion engine as described in 1.

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