JP6464961B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device, and more particularly to an engine control device having a variable compression ratio mechanism.

  There is an engine having a compression ratio variable mechanism and a catalyst. In this engine, the compression ratio of the variable compression ratio mechanism is set on the side that is lower than that after activation of the catalyst at the time of cold start of the engine and before the catalyst is activated, There is one that switches the compression ratio (see Patent Document 1). This is because if the compression ratio of the variable compression ratio mechanism is lowered at the time of cold start of the engine, the thermal efficiency of the engine is lowered, so that the temperature of the combustion gas that has flowed into the exhaust passage becomes higher than when the compression ratio is not lowered. It is what you use. Thus, the catalyst can be activated early by controlling the compression ratio of the compression ratio variable mechanism.

JP 2009-108720 A

  By the way, when the engine is in a state immediately after the cold start and before the warm-up is completed, harmful exhaust components such as CO, HC, and particulates are included in the combustion gas generated in the combustion chamber. For this reason, there is a need for an exhaust purification measure that prevents these harmful exhaust components from coming out of the tail pipe of the vehicle.

  By using a three-way catalyst as the catalyst, three harmful exhaust components of CO, HC and NOx are simultaneously purified efficiently. However, since the three-way catalyst is not intended only for HC generated in the combustion chamber, there is a limit in purifying all of the HC generated in the combustion chamber immediately after the cold start. If the compression ratio of the compression ratio variable mechanism is increased at the timing when the three-way catalyst is activated, the HC generated in the combustion chamber will deteriorate. Similarly, if the compression ratio of the variable compression ratio mechanism is increased at the timing when the three-way catalyst is activated, the particulates generated in the combustion chamber also deteriorate.

  Therefore, an object of the present invention is to provide an apparatus capable of suppressing deterioration of HC and particulates generated in a combustion chamber immediately after a cold start of an engine.

The engine control apparatus of the present invention includes a compression ratio variable mechanism, a fuel injection valve, a catalyst, and a compression ratio control means. The compression ratio variable mechanism can change the compression ratio of the engine. The fuel injection valve can supply fuel to the combustion chamber. The catalyst can purify exhaust from the engine.
The compression ratio control means sets a first required compression ratio as a required compression ratio until the catalyst is activated. The compression ratio control means sets a second required compression ratio higher than the first required compression ratio as a required compression ratio until the combustion chamber is warmed up after the catalyst is activated. The compression ratio control means sets a third required compression ratio that is higher than the second required compression ratio as the required compression ratio after the combustion chamber has been warmed up. Further, the compression ratio control means controls the compression ratio of the variable compression ratio mechanism so that the set required compression ratio can be obtained. The second required compression ratio is at least one of a required compression ratio for reducing HC generated in the combustion chamber and a required compression ratio for reducing particulates generated in the combustion chamber.

  In the present invention, when the compression ratio of the variable compression ratio mechanism is controlled so that the first required compression ratio is obtained, the time required for catalyst activation is a short time of about a few tens of seconds from the cold start of the engine. On the other hand, when the compression ratio of the variable compression ratio mechanism is controlled so that the second required compression ratio is obtained after the catalyst is activated, the time required to complete the warm-up of the combustion chamber is 50 from the cold start of the engine. It is a long time of about ~ 100 seconds. Thus, by controlling the compression ratio of the compression ratio variable mechanism using the first required compression ratio and the second required compression ratio, the time until the catalyst is activated at the time of cold start of the engine, The time until warm-up is completed can be varied. For this reason, the second required compression ratio is optimized in accordance with each requirement for the exhaust composition such as HC and particulates generated in the combustion chamber from the timing when the catalyst is activated until the combustion chamber is completely warmed up. Can be set to Further, since the second required compression ratio is lower than the third required compression ratio, the combustion chamber temperature rises slowly during the period when the second required compression ratio is set, and the time for maintaining the second required compression ratio Can be secured. This suppresses deterioration of HC and particulates generated in the combustion chamber during the period when the second required compression ratio is set, that is, from the timing when the catalyst is activated until the combustion chamber is warmed up. can do.

It is a schematic block diagram of a reciprocating engine having a compression ratio variable mechanism. It is a posture figure of each link in a high compression ratio position and a low compression ratio position. It is a schematic block diagram of the control system of the engine of 1st Embodiment. It is a characteristic figure of a basic target compression ratio. It is a timing chart showing the change of the exhaust temperature of the catalyst inlet, the combustion chamber temperature, and the required compression ratio from the cold start of the first embodiment. It is a flowchart for demonstrating the setting of the target compression ratio of 1st Embodiment. It is a flowchart for demonstrating the setting of the target compression ratio of 1st Embodiment. It is a timing chart showing the change of the exhaust temperature of the catalyst inlet, the combustion chamber temperature, and the required compression ratio from the cold start of the second embodiment. It is a flowchart for demonstrating the setting of the target compression ratio of 2nd Embodiment. It is a flowchart for demonstrating the setting of the target compression ratio of 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram of a reciprocating engine having a variable compression ratio mechanism.

  The compression ratio variable mechanism here is a multi-link type. Specifically, it is a mechanism for changing the compression ratio by changing the piston stroke. The engine 1 having a variable compression ratio mechanism has been previously proposed by the applicant of the present invention. However, since the engine 1 is publicly known, for example, in Japanese Patent Application Laid-Open No. 2001-227367, only the outline thereof will be described.

  The crankshaft 3 is provided with a crank journal 4 that is rotatably supported by a main bearing (not shown) in a cylinder block 2 constituting a part of the engine body for each cylinder. Each crank journal 4 has an axis O that coincides with the axis (rotation center) of the crankshaft 3 and constitutes a rotating shaft portion of the crankshaft 3.

  In addition, the crankshaft 3 is eccentric from the axis O, is provided with a crankpin 5a provided for each cylinder, a crank arm 5b that connects the crankpin 5a to the crank journal 4, and opposite to the crankpin 5 with respect to the axis O. And a counterweight 5c that mainly reduces the primary rotational vibration component of the piston motion. The crank arm 5b and the counterweight 5c are integrally formed in this embodiment.

  In the present embodiment, the piston 10 slidably fitted to the cylinder 11 formed for each cylinder and the crank pin 5a described above are a plurality of link members, that is, the upper link 7 (first link). It is mechanically linked by the lower link 6 (second link). The upper end side of the upper link 7 is externally fitted to a piston pin 9 (first pin) fixedly provided on the piston 10 so as to be relatively rotatable around the axis Oc. Further, the lower link side of the upper link 7 and the one main body 6a of the lower link 6 that is substantially bisected can be relatively rotated around the axis Od by a connecting pin 8 (second pin) that passes through both of them. It is connected to.

  The lower link 6 is configured by attaching two main bodies 6a and 6b so as to sandwich the crank pin 5a, and is mounted so as to be relatively rotatable around the crank pin 5a and the axis Oe at the sandwiched portion. Yes. The other lower link body 6b, which is substantially divided into two parts, and the upper end side of the control link 12 (third link) can be relatively rotated around the axis Of by a connecting pin 13 (third pin) that passes through both of them. It is connected to.

  The lower end side of the control link 12 is swingable around its axis Ob (a fulcrum provided on the cylinder block) on a control shaft 14 having an eccentric cam portion 15 that is rotatably supported by the cylinder block 2. It is externally fitted and supported. That is, an eccentric cam portion 15 is rotatably provided on the outer periphery of the control shaft 14, and the axis Oa of the eccentric cam portion 15 is eccentric by a predetermined amount with respect to the axis Ob of the control shaft 14. The eccentric cam portion 15 is rotationally controlled by a compression ratio control actuator 17 via a worm gear 16 according to the operating state of the engine and is held at an arbitrary rotational position.

  With such a configuration, as the crankshaft 3 rotates, the piston 10 moves up and down in the cylinder 11 via the crankpin 5a, the lower link 6, the upper link 7 and the piston pin 9, and is connected to the lower link 6. The control link 12 swings with the swing axis Ob on the lower end side as a fulcrum.

  Further, the eccentric cam portion 15 is rotationally controlled by the compression ratio control actuator 17, so that the axis Ob of the control shaft 14 serving as the swing axis of the control link 12 is moved around the axis Oa of the eccentric cam portion 15. Rotation, that is, the swing center position Ob of the control link 12 moves with respect to the engine body (and crankshaft rotation center O). As a result, the stroke of the piston 10 changes, and the compression ratio of each cylinder of the engine is variably controlled. For reference, FIG. 2 schematically shows the postures of the three links 7, 6, and 12 at the piston top dead center position. The left side of FIG. 2 is the high compression ratio position, and the right side of FIG. 2 is the low compression ratio position. Each link posture.

  The greatest feature of this compression ratio variable mechanism is that the top dead center position (combustion chamber volume) of the piston 10 can be changed by the angular position control of the control shaft 14 (control shaft), and the function as a so-called variable compression ratio mechanism. To demonstrate. To explain this, the above-mentioned “compression ratio” is a value defined by the following equation.

Compression ratio = (combustion chamber volume at bottom dead center position) / (combustion chamber volume at top dead center position)
... (1)
1 and 2, since the top dead center position of the piston 10 can be changed in the variable compression ratio mechanism, the variable compression ratio mechanism can change the "compression ratio" in the equation (1). It becomes.

  In addition, since the piston stroke characteristics can be made close to simple vibrations, the acceleration at the top and bottom dead center is substantially the same, and there is an effect of reducing vibrations that eliminates the need for a balancer shaft (four cylinders). Alternatively, the piston stroke characteristic can be set such that the piston acceleration on the top dead center side is smaller than the piston acceleration on the bottom dead center side. Such piston acceleration characteristics can be obtained with a multi-link mechanism composed of a plurality of link members as described above, and depends on whether or not the compression ratio (piston top dead center position) is variable. is not. Such piston stroke characteristics increase the piston stay time near the top dead center as compared with a conventional general engine in which the piston is connected to the crankshaft by a single connecting rod.

  FIG. 3 is a schematic configuration diagram of a control system of the engine 1 having a variable compression ratio mechanism. The engine 1 is, for example, a gasoline engine. An intake port 22 and an exhaust port 23 are formed on each side surface of the cylinder head 20, and the intake port 22 and the exhaust port 23 open to the combustion chamber 21. The combustion chamber formed in this way is called a pent roof type. An intake valve 24 is provided at the open end of the intake port 23 to the combustion chamber 21, and an exhaust valve 25 is provided at the open end of the exhaust port 23 to the combustion chamber 21. A fuel injection valve 26 is provided below the open end of the intake port 22 so as to face the combustion chamber 21. A spark plug 27 is provided at the center of the ceiling of the combustion chamber 21, and an electrode 27 a of the spark plug 27 projects into the combustion chamber 21.

  In the engine 1, well-known stratified combustion is performed in the operating region on the low load side. In the stratified combustion, a flammable air-fuel mixture is collected around the electrode 27a of the spark plug 27, and an air layer without fuel is formed around the mixture to burn. Specifically, the tumble control valve 28 provided near the upstream end of the intake port 22 is closed to generate a tumble flow (longitudinal vortex) in the combustion chamber 21 during the intake stroke. In order to preserve the generated tumble flow well, a shallow dish-like cavity 10 a is provided on the crown surface of the piston 10. The flow of air flowing in from the opening end of the intake port 22 along the wall of the cylinder 11 on the exhaust side in the combustion chamber 21 is reversed by the cavity 10a. This inverted air is directed along the wall of the cylinder 11 on the intake side toward the spark plug 27 on the ceiling of the combustion chamber 21 (see the arrow in the figure). Fuel is injected from the fuel injection valve 26 in the latter half of the compression stroke and mixed with air to form an air-fuel mixture. The injected fuel mixed with the air is guided to the electrode 27a of the spark plug 27 while being bundled together by the tumble flow. The ignition timing, which is the timing at which the spark plug 27 is ignited, is matched with the timing at which this block fuel reaches the electrode 27a of the spark plug 27, and a spark is applied to the electrode 27a of the spark plug 27 before the block fuel diffuses. Fly and ignite the bulk fuel. Since the air-fuel mixture is collected only around the electrode 27a of the spark plug 27 and there is air without fuel, that is, two layers are generated, so the combustion chamber 21 as a whole has an extremely lean air-fuel ratio. It becomes possible to burn in.

  An exhaust manifold 29A is connected to the exhaust port 23, and an exhaust pipe 29B is connected to a collecting portion of the exhaust manifold 29A. The exhaust component generated in the combustion chamber 21 by the combustion of the air-fuel mixture contains harmful components. In order to purify this harmful component, the exhaust pipe 29B is provided with an exhaust purification catalyst (hereinafter also simply referred to as “catalyst”) 30. As the catalyst 30 here, a three-way catalyst capable of simultaneously purifying three components of HC, CO, and NOx among harmful components is used.

  An engine controller 31 is provided to control the compression ratio of the compression ratio variable mechanism by the compression ratio control actuator 17 described above. The engine controller 31 not only controls the compression ratio of the compression ratio variable mechanism. Although details are not described, the engine controller 31 controls the fuel injection amount and fuel injection timing by the fuel injection valve 26 and the ignition timing by the spark plug 27. Further, a throttle device (not shown) is controlled.

  Signals from a crank angle sensor 32, an accelerator sensor 33, and a water temperature sensor 34 are input to the engine controller 31. Here, the crank angle sensor 32 is a sensor for detecting the crank angle position of the engine, and the engine rotational speed Ne is calculated based on a signal from the sensor. The accelerator sensor 33 detects the opening degree of the accelerator pedal. The water temperature sensor 34 detects the engine coolant temperature Tw.

  The engine controller 31 calculates a basic target compression ratio according to the load and the rotational speed Ne at that time by referring to a map of the basic target compression ratio from the engine load and the rotational speed Ne after the engine warm-up is completed. Then, the control amount (drive amount to the compression ratio variable mechanism) given to the compression ratio control actuator 17 is controlled so that the calculated basic target compression ratio is obtained.

  FIG. 4 shows the map contents of the basic target compression ratio. As shown in FIG. 4, the basic target compression ratio is set substantially in accordance with the engine load. In other words, the basic target compression ratio is increased to a predetermined value ε6, ε5, ε4, ε3, ε2, ε1 (ε6 <ε5 <ε4 <ε3 <ε2 <ε1) with the aim of improving fuel consumption as the load decreases. The reason why the basic target compression ratio is lowered on the high load side is to suppress the occurrence of knocking.

  Now, in the low load range after the engine warm-up is completed, the compression ratio of the compression ratio variable mechanism is set to the basic target compression ratio ε1 (see FIG. 4), which is a relatively higher compression ratio than the high load side, based on fuel efficiency requirements. Drive. This is because if the compression ratio of the compression ratio variable mechanism is set to a relatively high compression ratio, the thermal efficiency of the engine is improved correspondingly and the fuel consumption is improved. The basic target compression ratio ε1 set at this time is newly defined as “warm-up fuel efficiency required compression ratio”.

  On the other hand, even if the engine 30 is in the inactive state immediately after the engine is cold started, if the compression ratio of the variable compression ratio mechanism is operated as the above-mentioned warmed-up fuel efficiency required compression ratio ε1, the tail pipe HC Getting worse. For this reason, the presence or absence of a catalyst activation request is determined from the engine coolant temperature, the catalyst temperature, etc., and when there is a catalyst activation request, the compression ratio of the variable compression ratio mechanism is made lower than the fuel consumption requirement compression ratio ε1 after warming up. Let us consider such a technique (this technique is referred to as a “comparative example”). The required compression ratio ε01 for catalyst activation set at this time is defined as “catalyst activation required compression ratio”.

  The reason why the compression ratio of the variable compression ratio mechanism is lower than the required fuel efficiency compression ratio ε1 after warming up when there is a catalyst activation request is as follows. That is, since the thermal efficiency of the engine is reduced by reducing the compression ratio of the variable compression ratio mechanism to the catalyst activation required compression ratio ε01, the temperature of the exhaust gas discharged to the exhaust manifold 29A is equal to the fuel efficiency required compression ratio ε1 after warm-up. It rises more than when. This is because the exhaust gas whose temperature has risen is led to the catalyst 30 provided in the exhaust pipe 29B, thereby activating the catalyst 30 at an early stage.

  However, the comparative example has the following two problems (1) and (2) immediately after the engine cold start as a countermeasure against exhaust.

  Here, the terms are explained before entering into the two problems. In the present embodiment, two exhaust compositions of HC and particulate (exhaust particulate) generated in the combustion chamber 21 are considered. HC generated in the combustion chamber 21 and immediately after exiting the exhaust port 23 is generally known as “engine-out HC”. Here, an engine in which the exhaust manifold 29A is connected to the exhaust port 23 formed in one side surface of the cylinder head 20 is referred to as a “conventional engine”. In the case of a conventional engine, that is, the engine as shown in FIG. 3, engine-out refers to the connection port between the exhaust port 23 and the exhaust manifold 29A. On the other hand, an engine having an exhaust manifold in the cylinder head 20 has recently been proposed. In the engine, it is unclear which position the engine out points to. Therefore, in this embodiment, the HC generated in the combustion chamber 21 and immediately after passing through the exhaust valve 25 is defined as “valve-out HC” so as to be applicable to the engine. Of course, the conventional engine may be “engine-out HC”.

  Next, the particulate at the valve-out is considered so that the particulate generated in the combustion chamber 21 can be applied to the engine. In the case of a conventional engine, it is only necessary to consider particulates when the engine is out. However, particulates are simply referred to as “particulates” without “valve out”.

  Next, after the cold start of the engine, the temperature of the combustion chamber 21 gradually rises, and the temperature of the entire engine (cylinder block + cylinder head) including the combustion chamber 21 reaches an equilibrium state. Generally, the fact that the temperature of the entire engine including the combustion chamber 21 reaches an equilibrium state is said to “complete the engine warm-up”. In this embodiment, since the exhaust composition of HC and particulates generated in the combustion chamber is handled, it is only necessary to focus on the combustion chamber and the surroundings of the combustion chamber. Thus, the fact that the temperature of the combustion chamber and the temperature around the combustion chamber rises from the cold start of the engine is referred to as “the combustion chamber warms up”. Further, the fact that the combustion chamber and the temperature around the combustion chamber reach an equilibrium state is referred to as “combustion chamber warm-up is completed”. This completes the explanation of terms. The above two problems are as follows.

(1) Deterioration of valve-out HC Here, the case where the engine does not have the compression ratio variable mechanism and has the catalyst 30 but does not take measures for activating the catalyst 30 will be considered first. In this case, the time until the catalyst 30 is activated is usually a short time of about ten or more seconds after the engine is cold-started, whereas the time until the combustion chamber 21 is completely warmed up is It takes a long time of about 50 to 100 seconds from the cold start. Thus, when there is sufficient time to complete the warming up of the combustion chamber 21, the valve-out HC tends to decrease as the warming up of the combustion chamber 21 proceeds. Although the period until the completion of warming up of the combustion chamber 21 is somewhat prolonged, the valve-out HC can be reduced during that period. Since the compression ratio of the engine is constant, it can be said that there was no room for considering the relationship between the valve-out HC and the compression ratio.

  On the other hand, in the comparative example targeting an engine having a variable compression ratio mechanism, the compression ratio of the variable compression ratio mechanism is lowered to the required catalyst activation compression ratio ε01 until the catalyst 30 is activated, and the catalyst 30 is activated. The compression ratio is increased to the fuel efficiency required compression ratio ε1 after warm-up at the timing. However, if the compression ratio is increased to the post-warm fuel consumption required compression ratio ε1 at the timing when the catalyst 30 is activated, the combustion chamber 21 is rapidly warmed up after the timing when the catalyst 30 is activated, and the combustion chamber 21 warm-up is completed. The time until the catalyst 30 is activated and the time until the combustion chamber 21 is completely warmed up are not so different. Thus, if the time until the catalyst 30 is activated and the time until the combustion chamber 21 is completely warmed up are not so different, the warming up of the combustion chamber 21 is completed at the timing when the catalyst 30 is activated. Equal to no period until. If it is attempted to reduce the valve-out HC, a certain period for reducing the valve-out HC is required. However, if the period cannot be taken, the valve-out HC deteriorates.

  Further, since it has been found by the present inventor that the compression ratio suitable for reducing the valve-out HC is different from the post-warm-up fuel consumption required compression ratio ε1, the compression ratio of the variable compression ratio mechanism is increased to ε1. As a result, the valve-out HC deteriorates. The reason why the valve-out HC deteriorates by increasing the compression ratio to ε1 is as follows. That is, when the compression ratio of the compression ratio variable mechanism is relatively low and when the compression ratio is relatively high, the S / V ratio (combustion chamber surface area and volume ratio) is higher when the compression ratio is relatively high. Ratio). As a result, the surface area (wall surface) of the combustion chamber 21 surrounding the air containing fuel becomes relatively large, and the end gas increases. Since the wall surface of the combustion chamber 21 before the completion of warming-up of the combustion chamber 21 is a cooling surface, the generation of HC in the quenching area increases and the valve-out HC deteriorates. That is, in order to reduce the valve-out HC, it is better to make the compression ratio of the variable compression ratio mechanism lower than the post-warm fuel consumption required compression ratio ε1 and to reduce the S / V ratio. The compression ratio suitable for reducing the valve-out HC is lower than the post-warm fuel consumption required compression ratio ε1. For this reason, if the compression ratio of the compression ratio variable mechanism is increased to ε1 at the timing when the catalyst 30 is activated as described above, the valve-out HC generated in the combustion chamber 21 cannot be reduced.

(2) Deterioration of particulates Here again, consider the case where the engine does not have a variable compression ratio mechanism and has the catalyst 30, but does not take measures to activate the catalyst 30. In this case, the time until the catalyst 30 is activated is usually a short time of about ten or more seconds after the engine is cold-started, whereas the time until the combustion chamber 21 is completely warmed up is It takes a long time of about 50 to 100 seconds from the cold start. Thus, when there is sufficient time to complete the warming up of the combustion chamber 21, the particulates due to the fuel adhering to the wall surface in the combustion chamber 21 decrease as the warming up of the combustion chamber 21 proceeds. There was a trend. Although the period until the completion of warming up of the combustion chamber 21 is somewhat prolonged, the particulates could be reduced during that period. Since the compression ratio of the engine is constant, it can be said that there was no room for considering the relationship between the particulates and the compression ratio.

  Here, the generation of particulates immediately after the cold start of the engine will be described. A part of the fuel directly injected into the combustion chamber 21 from the fuel injection valve 26 at the cold start of the engine is in the combustion chamber 21. It reaches the wall and adheres. As the combustion chamber 21 warms up, the fuel adhering to the wall surface evaporates and emerges as a particulate in the combustion chamber 21 space. In this case, if the wall surface temperature in the combustion chamber 21 is sufficiently high, the particulates will burn and become oxides, but will evaporate immediately after the cold start and while the wall surface temperature in the combustion chamber 21 is low. The fuel that has come out into the space is discharged from the exhaust port 23 without burning. This unburned fuel is a particulate which is unburned hydrocarbon.

  On the other hand, in the comparative example targeting an engine having a variable compression ratio mechanism, the compression ratio of the variable compression ratio mechanism is lowered to the required catalyst activation compression ratio ε01 until the catalyst 30 is activated, and the catalyst 30 is activated. The compression ratio is increased to the fuel efficiency required compression ratio ε1 after warm-up at the timing. However, if the compression ratio is increased to the post-warm fuel consumption required compression ratio ε1 at the timing when the catalyst 30 is activated, the combustion chamber 21 is rapidly warmed up after the timing when the catalyst 30 is activated, and the combustion chamber 21 warm-up is completed. The time until the catalyst 30 is activated and the time until the combustion chamber 21 is completely warmed up are not so different. Thus, if the time until the catalyst 30 is activated and the time until the combustion chamber 21 is completely warmed up are not so different, the warming up of the combustion chamber 21 is completed at the timing when the catalyst 30 is activated. Equal to no period until. If it is attempted to reduce the particulates, a certain period for reducing the particulates is required, but if the period cannot be taken, the particulates will deteriorate.

  In addition, since it has been found by the present inventor that the compression ratio suitable for reducing particulates is different from the post-warm-up fuel consumption required compression ratio ε1, the compression ratio of the compression ratio variable mechanism should be increased to ε1. As a result, the particulates deteriorate. The reason why the particulates deteriorate by increasing the compression ratio to ε1 is as follows. That is, comparing the case where the compression ratio of the compression ratio variable mechanism is relatively low and the case where the compression ratio is relatively high, the surface area of the combustion chamber 21 becomes narrower when the compression ratio is relatively high. Assuming that the same amount of fuel is deposited on the wall surface in the combustion chamber 21 when the same amount of fuel is injected from the fuel injection valve 26, the surface area of the wall surface is smaller per unit area than when the surface area of the combustion chamber 21 is narrower. The amount of fuel adhering to the fuel increases. When the amount of adhesion per unit volume increases, the amount of fuel that evaporates into the combustion chamber 21 increases, and the particulates deteriorate. That is, in order to reduce the particulates, it is better to make the surface area of the combustion chamber 21 wider by making the compression ratio of the compression ratio variable mechanism lower than the post-warm fuel consumption required compression ratio ε1. The compression ratio suitable for reducing the particulates is lower than the fuel efficiency required compression ratio ε1 after warm-up. For this reason, if the compression ratio is increased to ε1 at the timing when the catalyst 30 is activated as described above, the particulates generated in the combustion chamber 21 cannot be reduced. Particulates cannot be reduced with a three-way catalyst. This concludes the explanation of the two problems.

  As described above, due to the above two problems, in the period from immediately after the cold start to the completion of the warm-up of the combustion chamber 21, in addition to the request to promote the warm-up of the catalyst 30, the valve-out HC and the particulates are required. It can be seen that there is a demand to reduce the exhaust component of the.

  However, the conventional apparatus, which is the same technology as the comparative example, has no description about the problems (1) and (2).

  The present embodiment has been devised to meet the above demand for reducing exhaust components of valve-out HC and particulates. Hereinafter, a request for reducing the valve-out HC is referred to as a “valve-out HC request”.

  On the other hand, the demand for reducing particulates will be further described. There are two types of worldwide regulations for particulates: regulations that regard particulates as quantities, and regulations that regard particulates as numbers. Regulations that take particulates as quantities are called PM (Particulate Matter) regulations, and regulations that take particulates as numbers are called PN (Particulate Number) regulations. In the following, a request to reduce PN is considered as a “PN request” in view of PN regulations that take particulates as numbers. That is, in this embodiment, it is assumed that the request to reduce the particulates is a PN request.

  Then, when the present inventor has conceived that there is a compression ratio suitable for reducing the valve-out HC, the compression ratio ε02 suitable for reducing the valve-out HC as described above in (1). Is found to be lower than the required fuel consumption compression ratio ε1 after warm-up. In an engine that does not have a variable compression ratio mechanism, there is no room to consider the relationship between the valve-out HC and the compression ratio. In an engine that has a variable compression ratio mechanism, the relationship between the valve-out HC and the compression ratio is considered. There is room for it. Hereinafter, a compression ratio suitable for reducing the valve-out HC is defined as “valve-out HC required compression ratio”.

  Similarly, when the present inventor has conceived that there is a compression ratio suitable for reducing particulates, the compression ratio ε03 suitable for reducing particulates as described above in (2) is It has been found that the fuel consumption required compression ratio after warm-up is lower than ε1. In an engine that does not have a variable compression ratio mechanism, there was no room to consider the relationship between particulates and compression ratios. However, in an engine that has a variable compression ratio mechanism, there is room to consider the relationship between particulates and compression ratios. It has happened. Hereinafter, a compression ratio suitable for reducing particulates is defined as “PN required compression ratio”.

  Even if the valve-out HC required compression ratio ε02 is set at the timing when the catalyst 30 is activated, the valve-out HC required compression ratio ε02 needs to be maintained for a predetermined period in order to reduce the valve-out HC. . In this case, since the valve-out HC required compression ratio ε02 is lower than the post-warm fuel consumption required compression ratio ε1, the increase in the combustion chamber temperature is slower than when the post-warm fuel consumption required compression ratio ε1, and the combustion chamber 21 is completely warmed up. The time to do becomes longer. That is, by setting the valve-out HC required compression ratio ε02, a new period is generated from the timing when the catalyst 30 is activated until the combustion chamber 21 is warmed up. It is advantageous that the valve-out HC can be surely reduced during this newly occurring period.

  Similarly, even if the PN required compression ratio ε03 is set at the timing when the catalyst 30 is activated, it is necessary to maintain the PN required compression ratio ε03 for a predetermined period in order to reduce the particulates. In this case, since the PN required compression ratio ε03 is lower than the post-warm fuel consumption required compression ratio ε1, the rise in the combustion chamber temperature is slower than that at the post-warm fuel consumption required compression ratio ε1, and the warming up of the combustion chamber 21 is completed. The time will be longer. That is, by setting the PN required compression ratio ε03, a new period is generated from the timing when the catalyst 30 is activated until the combustion chamber 21 is warmed up. Advantageously, the particulates can be reliably reduced during this newly occurring period.

  Here, in the present embodiment, the purpose is to suppress the deterioration of both the valve-out HC and the particulate, but the purpose is to suppress the deterioration of either one. It's okay. When it is intended to suppress the deterioration of both the valve-out HC and the particulates, the valve-out HC required compression ratio ε02 and the PN required compression ratio ε03 cannot be set simultaneously at the timing when the catalyst 30 is activated. . That is, it becomes a problem which of the valve-out HC required compression ratio ε02 and the PN required compression ratio ε03 is set first at the timing when the catalyst 30 is activated. This point will be described later.

  By the way, since both the valve-out HC and the particulates are in a direction to decrease as the combustion chamber 21 is warmed up, it is not true whether the valve-out HC request and the PN request can be handled in the same manner. That is, the present inventor believes that the valve-out HC required compression ratio ε02 and the PN required compression ratio ε03 are basically different because the manner in which the valve-out HC and particulates are generated in the combustion chamber 21 is different. . Further, the inventor believes that the period for maintaining the valve-out HC required compression ratio ε02 is basically different from the period for maintaining the PN required compression ratio ε03. Here, in order to show an example, the valve-out HC required compression ratio ε02 and the PN required compression ratio ε03 are between the catalyst activation required compression ratio ε01 and the warm-up fuel consumption required compression ratio ε1, and the valve-out HC required compression ratio. It is assumed that ε02 is lower than the PN required compression ratio ε03.

  As a result, the compression ratio increases in the order of the catalyst activation required compression ratio ε01, the valve-out HC required compression ratio ε02, the PN required compression ratio ε03, and the warm-up fuel consumption required compression ratio ε1. Therefore, in the present embodiment, first, the catalyst activation required compression ratio ε01 is set at the cold start. Then, the three required compression ratios of the valve-out HC required compression ratio ε02, the PN required compression ratio ε03, and the warmed-up fuel consumption required compression ratio ε1 are stepwise based on the combustion chamber temperature rather than the timing when the catalyst is activated. Control. As a result, the valve-out HC and the particulates can be reduced in the period from immediately after the engine cold start until the combustion chamber 21 is warmed up.

  The stepwise control of the three required compression ratios will be further described with reference to the timing chart of FIG. The timing chart of FIG. 5 shows changes in the exhaust temperature, the combustion chamber temperature, and the required compression ratio from the cold start of the engine as a model. In FIG. 5, the horizontal axis represents the elapsed time from the engine cold start timing. It is assumed that the engine is kept in the idle state for a while after the engine is cold started and the combustion chamber 21 is warmed up.

  As a parameter for determining whether or not the catalyst 30 is activated, the exhaust gas temperature is considered, so the exhaust gas temperature is described in the first stage of FIG. Here, the exhaust temperature is a substitute for the catalyst temperature. The exhaust temperature is assumed to be, for example, the exhaust temperature at the inlet of the catalyst 30. The exhaust temperature at the catalyst inlet can be regarded as the catalyst temperature.

  Further, the exhaust temperature is a parameter for determining whether or not the catalyst 30 is activated. That is, in this embodiment, it is determined whether the catalyst 30 is activated based on the exhaust temperature. Here, a case where it is determined whether or not the catalyst 30 has been activated based on the exhaust temperature at the catalyst inlet will be described, but the present invention is not limited to this case. For example, it may be simple to determine whether or not a predetermined time has elapsed from the cold start timing of the engine and determine that the catalyst 30 has been activated at the timing when the predetermined time has elapsed.

  In the present embodiment, the valve-out HC and the particulates immediately after the engine cold start are handled, and the combustion chamber temperature greatly affects the generation of the valve-out HC and the particulates. The temperature is described. Here, the combustion chamber temperature is assumed to be a superordinate concept of the wall surface temperature in the combustion chamber (abbreviated as “wall temperature” in FIG. 5) or the piston temperature. In other words, the combustion chamber temperature can be substituted by the wall surface temperature or the piston temperature in the combustion chamber.

  The combustion chamber temperature is a parameter for determining whether or not the combustion chamber 21 has been warmed up. That is, in this embodiment, it is determined whether or not the combustion chamber 21 has been warmed up based on the combustion chamber temperature. Here, although it demonstrates by the case where it is determined whether the warming-up of the combustion chamber 21 is completed based on the combustion chamber temperature, it is not restricted to this case. For example, in a simple case, it is determined whether or not a predetermined time has elapsed from the cold start timing of the engine, and it is determined that the combustion chamber 21 has been warmed up when the predetermined time has elapsed. Good.

  Further, the combustion chamber temperature e when the exhaust temperature reaches the catalyst activation determination temperature c is newly introduced as the “catalyst activation combustion chamber temperature”. Further, the combustion chamber temperature when the engine is operated at the post-warm-up fuel efficiency required compression ratio ε1 is newly introduced as “post-warm-up fuel efficiency required determination temperature” h.

  The case of the comparative example will be described first. Changes in the exhaust temperature of the catalyst inlet, the combustion chamber temperature, and the required compression ratio in the case of the comparative example are shown by the one-dot chain line in the first, third, and lowermost stages in FIG.

  In the comparative example, the compression ratio of the compression ratio variable mechanism is set to the catalyst activation required compression ratio ε01 at the engine cold start timing at t1 (see the one-dot chain line in the lowermost stage in FIG. 5). The exhaust gas temperature at the catalyst inlet coincides with the atmospheric temperature a at the engine cold start timing at t1. When the engine is started, the exhaust temperature at the catalyst inlet gradually rises from t1 and promotes the activation of the catalyst 30 (see the one-dot chain line in the first stage in FIG. 5). When the exhaust temperature at the catalyst inlet reaches the catalyst activation determination temperature c at the timing t2, it is determined that the catalyst 30 has been activated, and the catalyst activation determination flag is switched from zero to 1 (see the second stage in FIG. 5). . This catalyst activation determination flag is used in a flowchart described later. Further, in the comparative example, the compression ratio of the variable compression ratio mechanism is switched to the post-warm-up fuel efficiency required compression ratio ε1 at the catalyst activation determination timing at t2 (see the one-dot chain line in the lowermost stage in FIG. 5). This increases the thermal efficiency of the engine.

  The combustion chamber temperature also coincides with the atmospheric temperature a at the engine cold start timing at t1 (see the one-dot chain line in the third stage in FIG. 5). In the comparative example, the combustion chamber temperature gradually increases until the catalyst activation determination timing at t2 (see the one-dot chain line in the third stage in FIG. 5). When the compression ratio of the compression ratio variable mechanism is switched to the post-warm fuel consumption required compression ratio ε1 at the catalyst activation determination timing at t2, the combustion chamber temperature rapidly increases from the catalyst activation determination timing at t2 (FIG. 5 FIG. 5). (Refer to the one-dot chain line in the third stage). Then, the fuel consumption requirement determination temperature h after warm-up is reached at a timing t21 slightly delayed from the catalyst activation determination timing at t2, and the warm-up of the combustion chamber 21 is completed (see the one-dot chain line in the third stage in FIG. 5). . After the warm-up of the combustion chamber 21 is completed, the combustion chamber temperature maintains the post-warm fuel consumption requirement determination temperature h.

  In the comparative example, the time from the cold start of the engine to the activation of the catalyst 30 (catalyst activation time) is the time from t1 to t2. Further, the time from the cold start of the engine to the completion of warming-up of the combustion chamber 21 (engine warm-up completion time) is the time from t1 to t21. Thus, in the comparative example, the catalyst activation time and the engine warm-up completion time are substantially similar, and the period from the timing when the catalyst 30 is activated until the combustion chamber 21 is completely warmed up from t2 to t21. It is only a short period of time. Thus, in order to suppress the deterioration of the valve-out HC and the particulates, it is not possible to take a sufficient period until the combustion chamber 21 is warmed up from the timing when the catalyst 30 is activated.

  Next, changes in the exhaust temperature of the catalyst inlet, the combustion chamber temperature, and the required compression ratio in the case of the present embodiment are shown by overlapping the first, third, and bottom stages in FIG.

  In the present embodiment, since the required compression ratio (ε02, ε03) lower than the fuel consumption required compression ratio ε1 after warm-up is set from t2, the rate of increase in the combustion chamber temperature becomes more gradual than in the comparative example (FIG. 5). (See the solid line in the third row). Therefore, the combustion chamber temperature (hereinafter referred to as “valve out HC request determination”) for determining the end of the time for maintaining the valve out HC required compression ratio ε02 with respect to the combustion chamber temperature that rises more slowly than in the comparative example. "Temperature") f is newly introduced. Then, the compression ratio of the variable compression ratio mechanism is maintained at the valve-out HC required compression ratio ε02 until the combustion chamber temperature reaches the valve-out HC request determination temperature f (see the solid line at the bottom of FIG. 5). Further, a combustion chamber temperature (hereinafter referred to as “PN request determination temperature”) g for determining the end of the time for maintaining the PN required compression ratio ε03 is newly introduced. Then, the compression ratio of the variable compression ratio mechanism is maintained at the PN required compression ratio ε03 until the combustion chamber temperature reaches the PN required determination temperature g (see the solid line at the bottom of FIG. 5).

  In the present embodiment, a predetermined required compression ratio ε04 is further introduced between the PN required compression ratio ε03 and the post-warm-up fuel consumption required compression ratio ε1. Then, the compression ratio of the variable compression ratio mechanism is maintained at a predetermined required compression ratio ε04 until the combustion chamber temperature reaches the post-warm-up fuel consumption requirement determination temperature h (see the solid line at the bottom of FIG. 5). In consideration of the difference between the PN request determination temperature g and the post-warm-up fuel consumption request determination temperature h, before the combustion chamber temperature exceeds the PN request determination temperature g and reaches the post-warm-up fuel consumption request determination temperature h, , A predetermined required compression ratio ε04 lower than ε1 is given.

  Using the required compression ratios ε02, ε03, ε04 and the required determination temperatures f, g, h newly introduced in this way, the compression ratio is as low as ε02, ε03, ε04, ε1 from the catalyst activation determination timing at t2. Switching from one side to the other in a stepwise manner (see the solid line at the bottom of FIG. 5).

  Here, this embodiment added to the first level, the third level, and the lowest level in FIG. 5 is merely a model. For this reason, the compression ratio difference between ε01 and ε02, the compression ratio difference between ε02 and ε03, the compression ratio difference between ε03 and ε04, and the compression ratio difference between ε04 and ε1 are made the same. On the other hand, the combustion chamber temperature rises linearly from the engine cold start timing of t1 to the timing of t5 when the combustion chamber temperature reaches the post-warm fuel consumption requirement determination temperature h. The temperature difference between e and f, the temperature difference between f and g, and the temperature difference between g and h are the same. Thus, by making the change of the combustion chamber temperature a straight line and making each temperature difference of e and f, f and g, and g and h the same, time to maintain ε01, time to maintain ε02, and ε03 are maintained. The time for maintaining ε04 is equal. However, in practice, there are basically four compression ratio differences: a compression ratio difference between ε01 and ε02, a compression ratio difference between ε02 and ε03, a compression ratio difference between ε03 and ε04, and a compression ratio difference between ε04 and ε1. It will be different. Also, the four times of maintaining ε01, maintaining ε02, maintaining ε03, and maintaining ε04 are considered to be basically different.

  This embodiment will be further described. At the catalyst activation determination timing at t2, the compression ratio of the compression ratio variable mechanism is switched to the valve-out HC required compression ratio ε02 (see the solid line at the bottom of FIG. 5). Since the valve-out HC required compression ratio ε02 is lower than the post-warm fuel consumption required compression ratio ε1, the combustion chamber temperature rises more slowly from the catalyst-activated combustion chamber temperature e than in the comparative example (third stage in FIG. 5). (See the solid line). Then, the compression ratio of the compression ratio variable mechanism is maintained at the valve-out HC required compression ratio ε02 until the combustion chamber temperature reaches the valve-out HC request determination temperature f (see the solid line at the bottom of FIG. 5).

  By setting the valve-out HC required compression ratio ε02 to a value lower than the post-warm fuel consumption required compression ratio ε1, the S / V ratio becomes smaller than that at the post-warm fuel consumption required compression ratio ε1. The surface area (wall surface) of the combustion chamber 21 surrounding the air containing fuel becomes relatively narrow, and the end gas is reduced. This reduces the occurrence of HC in the quenching area. The valve-out HC required compression ratio ε02 set to a value lower than ε1 is maintained for a predetermined time (t2 to t3), so that the valve-out HC generated in the combustion chamber 21 is reliably reduced.

  The compression ratio of the variable compression ratio mechanism is switched from the valve-out HC required compression ratio ε02 to the PN required compression ratio ε03 at the timing t3 when the combustion chamber temperature reaches the valve-out HC required determination temperature f (see the solid line at the bottom of FIG. 5). . Since the PN required compression ratio ε03 is also lower than the post-warm fuel consumption required compression ratio ε1, the combustion chamber temperature rises more slowly than the comparative example from the valve-out HC required determination temperature f (see the solid line in the third stage in FIG. 5). ). The compression ratio of the variable compression ratio mechanism is maintained at the PN required compression ratio ε03 until the combustion chamber temperature reaches the PN required determination temperature g (see the solid line at the bottom of FIG. 5).

  By setting the PN required compression ratio ε03 to a value lower than the post-warm fuel consumption required compression ratio ε1, the surface area of the combustion chamber 21 becomes wider than when the post-warm fuel consumption required compression ratio ε1. Assuming that the same amount of fuel is attached to the wall surface in the combustion chamber 21 when the same amount of fuel is injected from the fuel injection valve 26, the fuel that adheres per unit area of the wall surface when the combustion chamber 21 has a larger surface area. The amount is reduced. When the amount of adhesion per unit volume decreases, the amount that appears as particulates decreases accordingly. Then, by maintaining the PN required compression ratio ε03 set to a value lower than ε1 for a predetermined time (t3 to t4), the particulates generated in the combustion chamber 21 are reliably reduced.

  The compression ratio of the compression ratio variable mechanism is switched from the PN required compression ratio ε03 to the predetermined required compression ratio ε04 at the timing t4 when the combustion chamber temperature reaches the PN required determination temperature g (see the solid line at the bottom of FIG. 5). Since the predetermined required compression ratio ε04 is also lower than the post-warm fuel consumption required compression ratio ε1, the combustion chamber temperature rises more slowly than the comparative example from the PN required determination temperature g (see the solid line in the third stage in FIG. 5). . Then, the compression ratio of the compression ratio variable mechanism is maintained at the predetermined required compression ratio ε04 until the combustion chamber temperature reaches the post-warm fuel consumption requirement determination temperature h (see the solid line at the bottom of FIG. 5).

  The compression ratio of the compression ratio variable mechanism is switched from the predetermined required compression ratio ε04 to the post-warm fuel consumption required compression ratio ε1 at the timing t5 when the combustion chamber temperature reaches the post-warm fuel consumption required determination temperature h (at the bottom of FIG. 5). (See solid line).

  Since the above three requirement determination temperatures f, g, and h have been introduced, three new flags, namely, a combustion chamber warm-up determination flag 1, a combustion chamber warm-up determination flag 2, and a combustion chamber warm-up determination flag 3 are newly added. Introduce. That is, the combustion chamber warm-up determination flag 1 is switched from zero to 1 at the timing t3 when the combustion chamber temperature reaches the valve-out HC request determination temperature f (see the fourth stage in FIG. 5). The combustion chamber warm-up determination flag 2 is switched from zero to 1 at the timing t4 when the combustion chamber temperature reaches the PN request determination temperature g (see the fifth stage in FIG. 5). The combustion chamber warm-up determination flag 3 is switched from zero to 1 at the timing t5 when the combustion chamber temperature reaches the post-warm fuel consumption requirement determination temperature h (see the sixth stage in FIG. 5). These three combustion chamber warm-up determination flags 1, 2, and 3 are used in a flowchart described later.

  Thus, in the present embodiment, the compression ratio is not increased from ε01 to the post-warm-up required fuel consumption compression ratio ε1 stepwise at the catalyst activation determination timing of t2, but the compression ratio is variable from the low side to the high side. The compression ratio of the mechanism is increased step by step to ε02, ε03, ε04, and ε1. As a result, the change in the combustion chamber temperature becomes more gradual than in the comparative example, and the combustion chamber temperature gradually increases from the catalyst activation combustion chamber temperature e to the post-warming fuel consumption requirement determination temperature h over a period from t2 to t5. To rise.

  As a result, in this embodiment, the time from the cold start of the engine to the activation of the catalyst 30 (catalyst activation time) is a relatively short time from t1 to t2. Further, the time from the cold start of the engine to the completion of warming-up of the combustion chamber 21 (engine warm-up completion time) is a sufficiently long time from t1 to t5. As described above, in this embodiment, the catalyst activation time and the engine warm-up completion time are greatly different from each other, which is sufficient as a period from the timing when the catalyst 30 is activated until the combustion chamber 21 is completely warmed up. A period can be secured.

  Further, the valve-out HC request determination temperature f and the PN request determination temperature g are introduced, and a period for maintaining the valve-out required compression ratio ε02 and a period for maintaining the PN required compression ratio ε03 are determined. That is, the period during which the combustion chamber temperature changes from the catalyst activation combustion chamber temperature e to the valve-out HC request determination temperature f is a period during which the valve-out required compression ratio ε02 is maintained. The period during which the combustion chamber temperature changes from the valve-out HC request determination temperature f to the PN request determination temperature g is a period during which the PN required compression ratio ε03 is maintained. Thus, by determining the period for maintaining ε02 and the period for maintaining ε03 based on the combustion chamber temperature, the period for maintaining ε02 and the period for maintaining ε03 can be optimally set.

  In the present embodiment, the period for maintaining ε02 and the period for maintaining ε03 are determined based on the combustion chamber temperature, but the present invention is not limited to this case. For example, the compression ratio of the variable compression ratio mechanism is switched from ε02 to ε03 at a timing when a predetermined time Δt1 has elapsed from the timing at which the catalyst 30 is activated. The compression ratio of the compression ratio variable mechanism may be switched from ε03 to ε04 at a timing when a predetermined time Δt2 (Δt1 <Δt2) has elapsed from the timing at which the catalyst is activated.

  Although FIG. 5 illustrates the case where the valve-out HC required compression ratio ε02 is lower than the PN required compression ratio ε03, the valve-out HC required compression ratio ε02 is not necessarily lower than the PN required compression ratio ε03. If the engine types are different, the PN required compression ratio ε03 may be lower than the valve-out HC required compression ratio ε02. Which of the valve out HC required compression ratio ε02 and the PN required compression ratio ε03 is lower and higher depends on the type of engine. Therefore, the valve out HC required compression ratio ε02 and the PN required compression ratio ε03 are set according to the type of engine. Just fit. As a result of the adaptation, when the PN required compression ratio ε03 is lower than the valve-out HC required compression ratio ε02, the compression ratio of the variable compression ratio mechanism is increased in the order of ε03, ε02, ε04, ε1 based on the combustion chamber temperature. Just go.

  Further, depending on the type of engine, the valve-out HC required compression ratio ε02 and the PN required compression ratio ε03 may be the same. Alternatively, the valve-out HC required compression ratio ε02 and the PN required compression ratio ε03 may be the same in order to simplify the adaptation. In this case, the compression ratio of the variable compression ratio mechanism may be increased in the order of ε02 (= ε03), ε04, and ε1 based on the combustion chamber temperature.

  In FIG. 5, the time required to maintain each of the four required compression ratios ε01, ε02, ε03, and ε04 is the same because of the model. Actually, it is considered that the time for maintaining ε01, ε02, ε03, and ε04 is not equal, and therefore, the time for maintaining ε01, ε02, ε03, and ε04 may be set by matching.

  In FIG. 5, the case where the predetermined required compression ratio ε04 is introduced has been described, but the predetermined required compression ratio ε04 may be omitted. In this case, the compression ratio of the variable compression ratio mechanism may be switched from ε03 to ε1 at the timing t4.

  As indicated by the solid line in the third stage of FIG. 5, the combustion chamber temperature rises linearly during the period from t2 to t5, which is also a model. Therefore, it is not limited to the case where the combustion chamber temperature rises linearly.

  In order to switch the compression ratio of the compression ratio variable mechanism from the catalyst activation required compression ratio ε01 to the valve-out HC required compression ratio ε02 as described above, the exhaust temperature sensor 35 (exhaust temperature detecting means) is provided in the present embodiment. The exhaust temperature sensor 35 detects the exhaust temperature Texh at the catalyst inlet. Based on the exhaust temperature Texh at the catalyst inlet detected by the exhaust temperature sensor 35, the catalyst activation determination means (31) determines whether or not the catalyst 30 has been activated. From this determination result, when the catalyst 30 is activated, the compression ratio control means (31) switches the compression ratio from ε01 to ε02.

  In addition, in the present embodiment, the combustion chamber temperature sensor 36 (combustion chamber temperature detecting means) is provided to switch the compression ratio of the compression ratio variable mechanism step by step from ε02 to ε03, ε04, and ε1 as described above. The combustion chamber temperature sensor 36 detects the combustion chamber temperature Tcmb. Based on the combustion chamber temperature Tcmb detected by the combustion chamber temperature sensor 36, the valve-out HC required compression ratio maintenance end determination means (31) determines whether or not to end the maintenance of the valve-out HC required compression ratio. When the maintenance of the valve-out HC required compression ratio is completed based on the determination result, the compression ratio control means (31) switches the compression ratio of the compression ratio variable mechanism from ε02 to ε03. Based on the combustion chamber temperature Tcmb detected by the combustion chamber temperature sensor 36, the PN required compression ratio maintenance end determination means (31) determines whether or not to end the maintenance of the PN required compression ratio. From this determination result, when the maintenance of the PN required compression ratio is completed, the compression ratio control means (31) switches the compression ratio of the variable compression ratio mechanism from ε03 to ε04. Based on the combustion chamber temperature Tcmb detected by the combustion chamber temperature sensor 36, the combustion chamber warm-up completion determination means (31) determines whether or not the combustion chamber 21 has been warmed up. From this determination result, when the warming-up of the combustion chamber 21 is completed, the compression ratio control means (31) switches the compression ratio of the variable compression ratio mechanism from ε04 to ε1.

  The exhaust temperature sensor 35 is not limited to being provided at the catalyst inlet. For example, it may be provided at an upstream position away from the catalyst 30. If the length of the exhaust pipe between the sensor position and the catalyst 30 is known, the temperature drop from the sensor position to the catalyst 30 can be calculated using the thermal conductivity of the exhaust pipe. Therefore, this drop is calculated from the exhaust temperature detected by the sensor. By subtracting, the exhaust temperature at the catalyst inlet can be obtained. In addition, a catalyst temperature sensor that directly detects the temperature of the catalyst 30 may be provided. Furthermore, the exhaust temperature sensor 35 and the catalyst temperature sensor may not be provided, but the exhaust temperature and the catalyst temperature may be estimated.

  Moreover, it is not restricted to the case where the combustion chamber temperature sensor 36 is provided. For example, sensors for detecting the wall surface temperature in the combustion chamber 21 and the temperature of the piston 10 may be provided, and the temperatures detected by these sensors may be used as the combustion chamber temperature. Further, instead of providing the combustion chamber temperature sensor 36, the combustion chamber temperature, the wall surface temperature in the combustion chamber, and the piston temperature may be estimated.

  The compression ratio control performed by the engine controller 31 will be described with reference to the flowcharts of FIGS. 6A and 6B. The flow in FIGS. 6A and 6B is for setting the target compression ratio from the engine cold start to the completion of warming up of the combustion chamber 21, and is executed at regular intervals (for example, every 10 m).

  6A and 6B correspond to FIG. That is, it is assumed that the valve-out HC required compression ratio ε02 is lower than the PM required compression ratio ε03. 6A and 6B, the catalyst activation determination flag and the three combustion chamber warm-up determination flags 1 shown in the second, fourth, fifth, and sixth stages in FIG. , 2 and 3 are used. However, in the flow of FIGS. 6A and 6B, the catalyst activation determination flag is abbreviated as “activation determination flag”. Similarly, the combustion chamber warm-up determination flag 1 is “warm-up determination flag 1”, the combustion chamber warm-up determination flag 2 is “warm-up determination flag 2”, and the combustion chamber warm-up determination flag 3 is “warm-up determination flag”. 3 ”.

  Step 1 looks at the cold time flag. Here, assuming that the cold time flag = 0, the process proceeds to step 2, and the cooling water temperature Tw [° C.] detected by the water temperature sensor 34 is compared with the predetermined value Tw1 [° C.]. The predetermined value Tw1 is a value for determining whether or not the engine is in a cold state, and is set in advance. When the cooling water temperature Tw exceeds the predetermined value Tw1, it is determined that the hot restart is being performed, and the current process is terminated.

  When the coolant temperature Tw is not more than the predetermined value Tw1 in step 2, it is determined that the engine is in a cold state. At this time, the process proceeds to Steps 3 and 4 to set the cold-time flag = 1, and the catalyst activation required compression ratio ε01 [anonymous number] is entered in the target compression ratio ε [anonymous number]. The compression ratio ε01 required for catalyst activation is determined in advance by conformance.

  Since the cold time flag is set to 1 in step 3, the process proceeds from step 1 to step 5 next time. In step 5, the catalyst activation determination flag (initially set to zero when the engine is started) is checked. Here, it proceeds to Step 6 assuming that the catalyst activation determination flag = 0. In step 6, the exhaust temperature Texh [° C.] at the catalyst inlet detected by the exhaust temperature sensor 35 is compared with the catalyst activation determination temperature c [° C.]. The catalyst activation determination temperature c is obtained in advance by conformity. When the exhaust temperature Texh at the catalyst inlet is lower than the catalyst activation determination temperature c, it is determined that the catalyst 30 is not activated. At this time, the operations of steps 3 and 4 are executed. As long as the exhaust gas temperature Texh at the catalyst inlet is lower than the catalyst activation determination temperature c in step 6, the operations in steps 3 and 4 are repeated.

  Eventually, when the exhaust temperature Texh at the catalyst inlet becomes equal to or higher than the catalyst activation determination temperature c in step 6, it is determined that the catalyst 30 has been activated. At this time, the process proceeds to Steps 7 and 8, where the catalyst activation determination flag = 1 is set, and the valve-out HC required compression ratio ε02 [anonymous number] is set as the target compression ratio ε. The valve-out HC required compression ratio ε02 is obtained in advance by conformance.

  Since the catalyst activation determination flag is set to 1 in step 7, the process proceeds from step 5 to step 9 next time. In step 9, the combustion chamber warm-up determination flag 1 (initially set to zero when the engine is started) is checked. Here, it is assumed that the combustion chamber warm-up determination flag 1 = 0, and the routine proceeds to step 10. In step 10, the combustion chamber temperature Tcmb [° C.] detected by the combustion chamber temperature sensor 36 is compared with the valve-out HC request determination temperature f [° C.]. The valve-out HC request determination temperature f is obtained in advance by conformance. When the combustion chamber temperature Tcmb is lower than the valve-out HC request determination temperature f, it is determined that it is not time to end the maintenance of the valve-out HC request compression ratio ε02. At this time, the operations of steps 7 and 8 are executed in order to maintain the valve-out HC required compression ratio ε02. As long as the combustion chamber temperature Tcmb is lower than the valve-out HC request determination temperature f in step 10, the operations in steps 7 and 8 are repeated.

  Eventually, when the combustion chamber temperature Tcmb becomes equal to or higher than the valve-out HC request determination temperature f in step 10, it is determined that it is time to finish maintaining the valve-out HC request compression ratio ε02. At this time, the routine proceeds to steps 11 and 12, the combustion chamber warm-up determination flag 1 is set to 1, and the PN required compression ratio ε03 [anonymous number] is entered as the target compression ratio ε. The PN required compression ratio ε03 is obtained in advance by adaptation.

  Since the combustion chamber warm-up determination flag 1 is set to 1 in step 11, the process proceeds from step 9 to step 13 next time. In step 13, the combustion chamber warm-up determination flag 2 (initially set to zero when the engine is started) is checked. Here, the process proceeds to step 14 assuming that the combustion chamber warm-up determination flag 2 = 0. In step 14, the combustion chamber temperature Tcmb detected by the combustion chamber temperature sensor 36 is compared with the PN request determination temperature g [° C.]. The PN request determination temperature f is obtained in advance by adaptation. When the combustion chamber temperature Tcmb is lower than the PN request determination temperature g, it is determined that it is not time to end the maintenance of the PN required compression ratio ε03. At this time, the operations of steps 11 and 12 are executed in order to maintain the PN required compression ratio ε03. As long as the combustion chamber temperature Tcmb is lower than the PN request determination temperature g in step 14, the operations in steps 11 and 12 are repeated.

  Eventually, when the combustion chamber temperature Tcmb becomes equal to or higher than the PN required determination temperature g in step 14, it is determined that it is time to end the maintenance of the PN required compression ratio ε3. At this time, the routine proceeds to steps 15 and 16, where the combustion chamber warm-up determination flag 2 = 1 is set, and a predetermined required compression ratio ε04 [anonymous number] is entered as the target compression ratio ε. The predetermined required compression ratio ε04 is obtained in advance by adaptation.

  Since the combustion chamber warm-up determination flag 2 is set to 1 in step 15, the process proceeds from step 13 to step 17 next time. In step 17, the combustion chamber warm-up determination flag 3 (initially set to zero when the engine is started) is checked. Here, it proceeds to step 18 assuming that the combustion chamber warm-up determination flag 3 = 0. In step 18, the combustion chamber temperature Tcmb detected by the combustion chamber temperature sensor 36 is compared with the post-warm-up fuel consumption requirement determination temperature h [° C.]. The fuel consumption requirement determination temperature h after warm-up is obtained in advance by conformance. When the combustion chamber temperature Tcmb is less than the post-warm-up fuel consumption requirement determination temperature h, it is determined that the combustion chamber 21 has not yet been warmed up. At this time, the operations of steps 15 and 16 are executed. As long as the combustion chamber temperature Tcmb is lower than the warm-up fuel consumption requirement determination temperature h in step 18, the operations of steps 15 and 16 are repeated.

  Eventually, when the combustion chamber temperature Tcmb becomes equal to or higher than the post-warming fuel consumption requirement determination temperature h in step 18, it is determined that the combustion chamber 21 has been warmed up. At this time, the routine proceeds to steps 19 and 20, where the combustion chamber warm-up determination flag 3 = 1 is set, and the post-warm-up fuel efficiency required compression ratio ε1 [unnamed number] is entered as the target compression ratio ε. The fuel consumption required compression ratio ε1 after warm-up is obtained in advance by conformity.

  Since the combustion chamber warm-up determination flag 3 is set to 1 in step 19, the next time, the process exits from step 17 and ends the processes of FIGS. 6A and 6B.

  In a flow not shown, the control amount (drive amount to the compression ratio variable mechanism) given to the compression ratio control actuator 17 so as to obtain the five required compression ratios ε01, ε02, ε03, ε04, ε1 set in this way. ) To control.

  Control of the compression ratio of the variable compression ratio mechanism performed in the flow of FIGS. 6A and 6B is open loop control, but it may be further feedback control. That is, the actual compression ratio of the compression ratio variable mechanism can be known from the control amount given to the compression ratio control actuator 17. Therefore, the actual compression ratio εreal of the variable compression ratio mechanism and the target compression ratio ε are compared, and it is determined whether or not the actual compression ratio εreal deviates from an allowable value centered on the target compression ratio ε. If the actual compression ratio εreal deviates from the allowable value centered on the target compression ratio ε, the compression ratio control is performed so that the actual compression ratio εreal falls within the allowable value range centered on the target compression ratio ε. The control amount given to the actuator 17 is feedback-controlled.

  Here, the effect of this embodiment is demonstrated.

  In this embodiment, a variable compression ratio mechanism, a fuel injection valve 26, a catalyst 30, and a compression ratio control means (31) are provided. The compression ratio variable mechanism can change the compression ratio of the engine. The fuel injection valve 26 can inject fuel directly into the combustion chamber 21 (fuel amount can be supplied). The catalyst 30 can purify exhaust from the engine. The compression ratio control means (31) sets a catalyst activation required compression ratio ε01 (first required compression ratio) as a required compression ratio until the catalyst 30 is activated. Further, the compression ratio control means (31) has a second required compression ratio (ε02, higher than the catalyst activation required compression ratio ε01 as a required compression ratio until the combustion chamber 21 is warmed up after the catalyst 30 is activated. ε03) is set. The compression ratio control means (31) sets a post-warm-up fuel consumption required compression ratio ε1 (a third required compression ratio higher than the second required compression ratio) as the required compression ratio after the combustion chamber 21 has been warmed up. To do. Further, the compression ratio control means (31) controls the compression ratio of the variable compression ratio mechanism so that the set required compression ratios ε01, ε02, ε03, ε1 are obtained. In the present embodiment, when the compression ratio of the compression ratio variable mechanism is controlled so that the required catalyst activation compression ratio ε01 is obtained, the time required for the activation of the catalyst 30 is about several tens of seconds from the cold start of the engine. Is a short time. On the other hand, when the compression ratio of the variable compression ratio mechanism is controlled so that the second required compression ratio is obtained after the catalyst 30 is activated, the time required for the warm-up of the combustion chamber 21 to be completed is a cold start of the engine. It is a long time of about 50 to 100 seconds. Thus, by controlling the compression ratio of the compression ratio variable mechanism using the catalyst activation required compression ratio ε01 and the second required compression ratio, the time until the catalyst 30 is activated at the cold start of the engine, The time until the combustion chamber 21 is completely warmed up can be varied. For this reason, in the period from when the catalyst 30 is activated to when the warming-up of the combustion chamber 21 is completed, the second requirement is matched with each requirement for the exhaust composition such as HC and particulates generated in the combustion chamber 21. The compression ratio can be set optimally. In addition, since the second required compression ratio is lower than the fuel efficiency required compression ratio ε1 after warm-up, the combustion chamber temperature rises slowly during the period when the second required compression ratio is set, and the second required compression ratio is reduced. Time to maintain can be secured. As a result, the HC and particulates generated in the combustion chamber 21 during the period during which the second required compression ratio is set, that is, the period from when the catalyst is activated until the warming-up of the combustion chamber 21 is completed. Deterioration can be suppressed.

  In the present embodiment, the second required compression ratio is the valve-out HC required compression ratio ε02 (required compression ratio for reducing HC generated in the combustion chamber), and the PN required compression ratio ε03 (particulate generated in the combustion chamber). At least one of the required compression ratios. As a result, when the second required compression ratio is the valve-out HC required compression ratio ε02, the deterioration of HC generated in the quenching area in the period from when the catalyst 30 is activated until the combustion chamber 21 is completely warmed up. Can be suppressed. In addition, when the second required compression ratio is the PN required compression ratio ε03, the particulates resulting from the adhesion of fuel to the combustion chamber wall surface during the period from the timing when the catalyst 30 is activated until the combustion chamber 21 is warmed up. Can be prevented.

  In the present embodiment, the second required compression ratio is two, ie, the valve-out HC required compression ratio ε02 and the PN required compression ratio ε03, and the valve-out HC required compression ratio ε02 is lower than the PN required compression ratio ε03. . The compression ratio control means switches the compression ratio of the variable compression ratio mechanism in the order of the valve-out HC required compression ratio ε02 and the PN required compression ratio ε03. This simplifies the increase in HC generated in the quenching area and the deterioration of the particulates due to the fuel adhering to the wall of the combustion chamber during the period from the timing when the catalyst 30 is activated until the warm-up of the combustion chamber 21 is completed. Can be suppressed.

  In this embodiment, a combustion chamber temperature sensor 36 (combustion chamber temperature detection means) is provided. Then, based on the combustion chamber temperature detected by the combustion chamber temperature sensor 36, the compression ratio control means ε02 (the lower of the two required compression ratios), ε03 (of the two required compression ratios) The compression ratio of the variable compression ratio mechanism is switched stepwise in the order of ε1 (third required compression ratio). As a result, it is possible to optimally set the period for maintaining ε02 and the period for maintaining ε03.

  In the present embodiment, an exhaust temperature sensor 35 (exhaust temperature detection means) and a catalyst activation determination means (31) are provided. The exhaust temperature sensor 35 detects the exhaust temperature. The catalyst activation determination means (31) determines whether or not the catalyst 30 is activated based on the exhaust temperature detected by the exhaust temperature sensor 35. As a result, it is possible to improve the accuracy of determining whether or not the catalyst 30 is activated.

  In this embodiment, a combustion chamber temperature sensor 36 (combustion chamber temperature detection means) and a combustion chamber warm-up determination means (31) are provided. The combustion chamber temperature sensor 36 detects the temperature of the combustion chamber 21. The combustion chamber warm-up determination means (31) determines whether or not the combustion chamber 21 has been warmed up based on the temperature detected by the combustion chamber temperature sensor. As a result, it is possible to increase the accuracy of determining whether or not the combustion chamber 21 has been warmed up.

(Second Embodiment)
The timing chart of FIG. 7 is the second embodiment, which replaces the timing chart of FIG. 5 of the first embodiment. The same parts as those in the timing chart of FIG.

  In the first embodiment, the compression ratio of the variable compression ratio mechanism is switched in stages from ε02, ε03, ε04, and ε1 from the timing when the catalyst 30 is activated. On the other hand, in the second embodiment, the compression ratio of the variable compression ratio mechanism is continuously changed from the catalyst activation required compression ratio ε01 to the warmed fuel consumption required compression ratio ε1 from the timing when the catalyst 30 is activated. That is, as shown in the lowermost stage of FIG. 7, the compression ratio of the variable compression ratio mechanism is gradually increased from the catalyst activation required compression ratio ε01 to the valve-out HC required compression ratio ε02 of the first embodiment in the period from t2 to t3. In other words, the value that gradually increases from ε01 to ε02 of the first embodiment in the period from t2 to t3 is the valve-out HC required compression ratio ε02 'of the second embodiment. The period from t2 to t3 is a period for maintaining the valve-out HC required compression ratio ε02 'of the second embodiment, and this point is the same as that of the first embodiment.

  Similarly, as shown in the lowermost stage of FIG. 7, the compression ratio of the variable compression ratio mechanism is changed from the valve out / out HC required compression ratio ε02 of the first embodiment to the predetermined required compression of the first embodiment in the period from t3 to t4. Increase gradually to the ratio ε04. In other words, a value that gradually increases from ε02 of the first embodiment to ε04 of the first embodiment in the period from t3 to t4 is set as the PN required compression ratio ε03 ′ of the second embodiment. The period from t3 to t4 is a period for maintaining the PN required compression ratio ε03 'of the second embodiment, and this is the same as the first embodiment.

  Similarly, the compression ratio of the compression ratio variable mechanism is gradually increased from the predetermined required compression ratio ε04 of the first embodiment to the post-warm fuel consumption required compression ratio ε1 in the period from t4 to t5 as shown in the lowermost stage of FIG. . In other words, the value that gradually increases from ε04 to ε1 in the first embodiment in the period from t4 to t5 is the predetermined required compression ratio ε04 'in the second embodiment. The period from t4 to t5 is a period for maintaining the predetermined required compression ratio ε04 'of the second embodiment, and this point is the same as that of the first embodiment.

  In the lowest stage of FIG. 7, the compression ratio increases linearly during the period from t2 to t3, from t3 to t4, and from t4 to t5, but this is not a limitation. Moreover, although it becomes a broken line in the period from t2 to t5, it is not restricted to this case.

  The flow of FIGS. 8A and 8B is for setting the target compression ratio between the engine cold start of the second embodiment and the completion of warming up of the combustion chamber 21, and is executed at regular intervals (for example, every 10 m). To do. The same parts as those in the flow of FIGS. 6A and 6B of the first embodiment are denoted by the same reference numerals.

  8A and 8B correspond to FIG. That is, the valve-out HC required compression ratio ε02 is lower than the PM required compression ratio ε03. 8A and 8B, the catalyst activation determination flag and the three combustion chamber warm-up determination flags 1 shown in the second, fourth, fifth, and sixth stages in FIG. , 2 and 3 are used. However, the catalyst activation determination flag is also abbreviated as “activation determination flag” in the flow of FIGS. 8A and 8B. Similarly, the combustion chamber warm-up determination flag 1 is “warm-up determination flag 1”, the combustion chamber warm-up determination flag 2 is “warm-up determination flag 2”, and the combustion chamber warm-up determination flag 3 is “warm-up determination flag”. 3 ”.

  6A and 6B in the first embodiment are mainly steps 21 to 27. In step 6, when the exhaust temperature Texh at the catalyst inlet becomes equal to or higher than the catalyst activation determination temperature c, it is determined that the catalyst 30 has been activated, and the process proceeds to step 7 where the catalyst activation determination flag = 1 is set.

  In step 21, the catalyst activation required compression ratio ε01 is added to the target compression ratio ε. This is a portion where ε01 of the first embodiment is inserted as an initial value of the valve-out HC required compression ratio ε02 'of the second embodiment.

  Since the catalyst activation determination flag is set to 1 in step 7, the process proceeds from step 5 to step 9 next time. In step 9, the combustion chamber warm-up determination flag 1 (initially set to zero when the engine is started) is checked. Here, it is assumed that the combustion chamber warm-up determination flag 1 = 0, and the routine proceeds to step 10. In step 10, the combustion chamber temperature Tcmb detected by the combustion chamber temperature sensor 36 is compared with the engine-out HC request determination temperature f. When the combustion chamber temperature Tcmb is lower than the engine-out HC request determination temperature f, it is determined that it is not time to end the maintenance of the valve-out HC request compression ratio ε02 'of the second embodiment. At this time, in order to maintain the valve-out HC required compression ratio ε02 ′ of the second embodiment, the process proceeds to steps 22 and 23, the activation determination flag = 1, and the target compression ratio ε [anonymous number] is a constant value Δ1 [anonymous number]. Is added to the target compression ratio ε [anonymous number].

  As long as the combustion chamber temperature Tcmb is lower than the engine-out HC request determination temperature f in step 10, the operations in steps 22 and 23 are repeated. As a result, the target compression ratio ε increases by a constant value Δ1 from the catalyst activation required compression ratio ε01. At this time, the target compression ratio ε is calculated as the valve-out HC required compression ratio ε02 'of the second embodiment. That is, the constant value Δ1 is a value that determines the amount of increase in the target compression ratio ε (valve-out HC required compression ratio ε02 'of the second embodiment) per calculation cycle, and is adapted in advance.

  Eventually, when the combustion chamber temperature Tcmb becomes equal to or higher than the engine-out HC required determination temperature f in step 10, it is determined that it is time to end the maintenance of the valve-out HC required compression ratio ε02 'of the second embodiment. At this time, the routine proceeds to step 11 where the combustion chamber warm-up determination flag 1 = 1.

  In step 24, the valve-out HC required compression ratio ε02 of the first embodiment is added to the target compression ratio ε. This is a portion where the valve-out HC required compression ratio ε02 of the first embodiment is inserted as an initial value of the PN required compression ratio ε03 'of the second embodiment.

  Since the combustion chamber warm-up determination flag 1 is set to 1 in step 11, the process proceeds from step 9 to step 13 next time. In step 13, the combustion chamber warm-up determination flag 2 (initially set to zero when the engine is started) is checked. Here, the process proceeds to step 14 assuming that the combustion chamber warm-up determination flag 2 = 0. In step 14, the combustion chamber temperature Tcmb detected by the combustion chamber temperature sensor 36 is compared with the PN request determination temperature g. When the combustion chamber temperature Tcmb is lower than the PN request determination temperature g, it is determined that it is not time to end the maintenance of the PN required compression ratio ε03 'of the second embodiment. At this time, in order to maintain the PN required compression ratio ε03 ′ of the second embodiment, the process proceeds to steps 25 and 26, the warm-up determination flag 1 = 1, and the target compression ratio ε [anonymous number] is set to a constant value Δ2 [anonymous number]. The sum is again set as the target compression ratio ε [anonymous number].

  As long as the combustion chamber temperature Tcmb is lower than the PN request determination temperature g in step 14, the operations in steps 25 and 26 are repeated. As a result, the target compression ratio ε increases by a constant value Δ2 from the engine-out HC required compression ratio ε02 of the second embodiment. As the target compression ratio ε at this time, the PN required compression ratio ε03 'of the second embodiment is calculated. That is, the constant value Δ2 is a value that determines the amount of increase in the target compression ratio ε (PN required compression ratio ε03 'in the second embodiment) per calculation cycle, and is adapted in advance.

  Eventually, when the combustion chamber temperature Tcmb becomes equal to or higher than the PN required determination temperature g in step 14, it is determined that it is time to end the maintenance of the PN required compression ratio ε03 'of the second embodiment. At this time, the routine proceeds to steps 15 and 16, where the combustion chamber warm-up determination flag 2 = 1 is set, and the predetermined required compression ratio ε04 of the first embodiment is added to the target compression ratio ε. Step 16 is a part for inserting the predetermined required compression ratio ε04 of the first embodiment as an initial value of the predetermined required compression ratio ε04 'of the second embodiment.

  Since the combustion chamber warm-up determination flag 2 is set to 1 in step 15, the process proceeds from step 13 to step 17 next time. In step 17, the combustion chamber warm-up determination flag 3 (initially set to zero when the engine is started) is checked. Here, it proceeds to step 18 assuming that the combustion chamber warm-up determination flag 3 = 0. In step 18, the combustion chamber temperature Tcmb detected by the combustion chamber temperature sensor 36 is compared with the post-warm-up fuel consumption requirement determination temperature h. When the combustion chamber temperature Tcmb is less than the post-warm-up fuel consumption requirement determination temperature h, it is determined that the combustion chamber 21 has not yet been warmed up. At this time, the routine proceeds to steps 27 and 28, where the warm-up determination flag 2 is set to 1, and the target compression ratio ε [anonymous number] added to the target compression ratio ε [anonymous number] is again set as the target compression ratio ε [anonymous number]. .

  As long as the combustion chamber temperature Tcmb is less than the warm-up fuel consumption requirement determination temperature h in step 18, the operations in steps 27 and 28 are repeated. As a result, the target compression ratio ε increases from the predetermined required compression ratio ε04 of the first embodiment by a constant value Δ3. The target compression ratio ε at this time is the predetermined required compression ratio ε04 'of the second embodiment. That is, the constant value Δ3 is a value that determines the amount of increase in the required compression ratio ε (predetermined required compression ratio ε04 'in the second embodiment) per calculation cycle, and is adapted in advance.

  Eventually, when the combustion chamber temperature Tcmb becomes equal to or higher than the post-warming fuel consumption requirement determination temperature h in step 18, it is determined that the combustion chamber 21 has been warmed up. At this time, the routine proceeds to steps 19 and 20, where the combustion chamber warm-up determination flag 3 = 1 is set, and the post-warm-up fuel efficiency required compression ratio ε1 is added to the target compression ratio ε.

  By setting the combustion chamber warm-up determination flag 3 = 1 in step 19, the next time, the process exits from step 17 and ends the processes of FIGS. 8A and 8B.

  In the second embodiment, there are two cases where the second required compression ratio is the valve-out HC required compression ratio ε02 and the PN required compression ratio ε03, and the valve-out HC required compression ratio ε02 is lower than the PN required compression ratio ε03. deal with. Then, the compression ratio control means includes a catalyst activation required compression ratio ε01 (first required compression ratio), a valve-out HC required compression ratio ε02, a PN required compression ratio ε03, a warm-up fuel consumption required compression ratio ε1 (third required compression). The compression ratio of the variable compression ratio mechanism is continuously controlled in the order of (ratio). As a result, the deterioration of the HC generated in the quenching area and the deterioration of the particulates due to the fuel adhering to the combustion chamber wall surface during the period from the timing when the catalyst 30 is activated until the warming-up of the combustion chamber 21 is completed are accurate. It can be suppressed well.

  In the second embodiment, a combustion chamber temperature sensor 36 (combustion chamber temperature detection means) is provided. Based on the combustion chamber temperature detected by the combustion chamber temperature sensor 36, the compression ratio control means (31) is ε02 (the lower of the two required compression ratios), ε03 (the two required compression ratios). Of the compression ratio variable mechanism is continuously controlled in the order of ε1 (third required compression ratio). As a result, it is possible to optimally set the period for maintaining ε02 and the period for maintaining ε03.

(Third embodiment)
The environmental condition parameters when the engine is actually cold-started are different from the environmental condition parameters when the five required compression ratios ε01, ε02, ε03, ε04, and ε1 are set (adapted). Can be considered. Here, as environmental condition parameters,
<1> Intake air temperature (intake air temperature),
<2> Atmospheric temperature,
<3> Intercooler outlet temperature,
<4> Engine coolant temperature,
<5> Engine lubricating oil temperature (oil temperature)
<6> Atmospheric pressure,
Can be mentioned.

  Here, the intercooler of <3> is for cooling the intake air whose temperature has been increased by the compressor when a turbocharger is added to the engine having the variable compression ratio mechanism and the catalyst. is there. <1> to <5> are environmental condition parameters that affect the combustion chamber temperature, and <6> is an environmental condition parameter that affects the compression ratio of the compression ratio variable mechanism.

  Even when the environmental condition parameters are different from the environmental condition parameters when the above five required compression ratios are set (adapted), if the same required compression ratios are used, valve-out HC and particulates deteriorate. May end up. Thus, in the third embodiment, the five required compression ratios are corrected based on at least one of the environmental condition parameters <1> to <6>. Specifically, depending on the deviation (difference or ratio) of the environmental condition parameters when the actual environmental condition parameters and the respective required compression ratios are set (adapted), the above five required compression ratios are reduced or increased. Correct to the side to be used.

  The case of the temperature of the intake air <1> will be specifically described. Assume that the temperature of the intake air when the engine is actually cold started is higher by a predetermined value ΔT1 than the temperature of the intake air when the above five required compression ratios are set (adapted). Then, the combustion chamber temperature rises in a state shifted to a higher side by a predetermined value ΔT1 than in FIGS. In this case, the combustion chamber temperature rises faster than when the above five required compression ratios are adapted, and the valve-out HC and particulates deteriorate. In this case, in order to prevent the combustion chamber temperature from rising too early than when the above five required compression ratios are adapted, the above five required compression ratios must be reduced. Therefore, in the third embodiment, a difference ΔT1 between the actual intake air temperature and the intake air temperature when the above five required compression ratios are adapted is calculated, and the required compression ratios are reduced according to the difference Δt1. Correct to the side to be made. Here, the actual temperature of the intake air is detected by a temperature sensor. Thus, even when the actual intake air temperature is higher than the intake air temperature when the above five required compression ratios are set (adapted), the combustion chamber 21 is warmed up from the timing when the catalyst 30 is activated. The deterioration of the valve-out HC and the particulates generated in the combustion chamber 21 during the period until is completed can be accurately suppressed.

  On the other hand, it is assumed that the temperature of the intake air when the engine is actually cold started is lower by a predetermined value ΔT2 than the temperature of the intake air when the above five required compression ratios are set (adapted). Then, the combustion chamber temperature rises in a state shifted to a lower side by a predetermined value ΔT2 than in the case of FIGS. In this case, the combustion chamber temperature rises too slowly compared with the case where the above five required compression ratios are adapted, and in this case as well, valve-out HC and particulates are deteriorated. In addition, the time until the combustion chamber 21 is warmed up is prolonged. In this case, to prevent the combustion chamber temperature from rising too slowly compared with the case where the five required compression ratios are adapted, the five required compression ratios should be increased. Therefore, in the third embodiment, a difference ΔT2 between the actual intake air temperature and the intake air temperature when the five required compression ratios are adapted is calculated, and the five required compressions are calculated according to the difference ΔT2. Correct the ratio to the higher side. Thus, even when the actual intake air temperature is lower than the intake air temperature when the above five required compression ratios are set (adapted), the combustion chamber 21 is warmed up from the timing when the catalyst 30 is activated. The deterioration of the valve-out HC and the particulates generated in the combustion chamber 21 during the period until is completed can be accurately suppressed. In addition, it is possible to avoid prolonging the time until the combustion chamber 21 is warmed up.

  The other environmental condition parameters in the above <2> to <6> may be considered similarly.

  In the third embodiment, when the actual environmental condition parameter is different from the environmental condition parameter when the five required compression ratios are set, each of the five environmental condition parameters is based on at least one of the environmental condition parameters. Correct the required compression ratio. As a result, even when the actual environmental condition parameters differ from the environmental condition parameters when the five required compression ratios are set, the warming up of the combustion chamber 21 is completed from the timing when the catalyst 30 is activated. It is possible to suppress the deterioration of the valve-out HC and the particulates that occur during the period.

  In the third embodiment, each set required compression ratio is corrected based on the outlet temperature of the intercooler. As a result, even when a turbocharger is added, the deterioration of valve-out HC and particulates that occur during the period from when the catalyst 30 is activated until the combustion chamber 21 is warmed up is suppressed. Can do.

  In the embodiment, the case where the stratified combustion is performed in the period from the cold start timing of the engine to the completion of the warm-up of the combustion chamber 21 has been described. However, the homogeneous combustion may be performed in the period.

  In the embodiment, the case has been described in which the fuel injection valve can inject fuel directly into the combustion chamber, but the present invention is not limited to this case. For example, it may be a fuel injection valve that supplies fuel to the intake port.

1 Engine 21 Combustion chamber 26 Fuel injection valve 30 Catalyst 31 Engine controller (compression ratio control means, catalyst activation determination means, combustion chamber warm-up determination means)
35 Exhaust temperature sensor (exhaust temperature detection means)
36 Combustion chamber temperature sensor (combustion chamber temperature detection means)

Claims (9)

A variable compression ratio mechanism capable of changing the compression ratio of the engine;
A fuel injection valve capable of supplying fuel into the combustion chamber;
A catalyst that can purify the exhaust from the engine;
The first required compression ratio as the required compression ratio until the catalyst is activated is higher than the first required compression ratio as the required compression ratio until the combustion chamber is warmed up after the activation of the catalyst. The second required compression ratio is set to a third required compression ratio higher than the second required compression ratio as the required compression ratio after the combustion chamber has been warmed up, and the compression is performed so that the set required compression ratio is obtained. Compression ratio control means for controlling the compression ratio of the variable ratio mechanism;
Bei to give a,
The second required compression ratio is at least one of a required compression ratio for reducing HC generated in the combustion chamber and a required compression ratio for reducing particulates generated in the combustion chamber. An engine control device. When the second required compression ratio is the two required compression ratios and the two required compression ratios are different,
The compression ratio control means switches the compression ratio of the variable compression ratio mechanism in the order of the lower one of the two required compression ratios and the higher one of the two required compression ratios. The engine control apparatus described in 1 . Combustion chamber temperature detection / estimation means for detecting or estimating the temperature of the combustion chamber,
The compression ratio control means has a lower one of the two required compression ratios and a higher one of the two required compression ratios based on the combustion chamber temperature detected or estimated by the combustion chamber temperature detecting / estimating means. On the other hand, the engine control apparatus according to claim 2, wherein the compression ratio of the variable compression ratio mechanism is switched stepwise in the order of the third required compression ratio . When the second required compression ratio is the two required compression ratios and the two required compression ratios are different,
The compression ratio control means may change the compression ratio in the order of the first required compression ratio, the lower of the two required compression ratios, the higher of the two required compression ratios, and the third required compression ratio. The engine control device according to claim 1, wherein the compression ratio of the mechanism is continuously controlled. Combustion chamber temperature detection / estimation means for detecting or estimating the temperature of the combustion chamber,
The compression ratio control means has a lower one of the two required compression ratios and a higher one of the two required compression ratios based on the combustion chamber temperature detected or estimated by the combustion chamber temperature detecting / estimating means. 5. The engine control apparatus according to claim 4, wherein the compression ratio of the compression ratio variable mechanism is continuously controlled in the order of the third required compression ratio . Exhaust / catalyst temperature detection / estimation means for detecting or estimating the exhaust gas temperature or the catalyst temperature;
Catalyst activation determining means for determining whether or not the catalyst is activated based on the temperature of the exhaust or the catalyst detected or estimated by the exhaust / catalyst temperature detecting / estimating means;
The engine control device according to any one of claims 1 to 5, further comprising: Combustion chamber temperature detection / estimation means for detecting or estimating the temperature of the combustion chamber;
Combustion chamber warm-up determination means for determining whether or not the combustion chamber has been warmed up based on the temperature detected or estimated by the combustion chamber temperature detection / estimation means;
The engine control device according to any one of claims 1 to 6, further comprising: The set required compression ratio is corrected based on at least one parameter of intake air temperature, atmospheric temperature, engine coolant temperature, engine lubricating oil temperature, and atmospheric pressure. The engine control device according to any one of 1 to 7 . When equipped with a turbocharger and an intercooler,
The engine control device according to any one of claims 1 to 8, wherein each of the set required compression ratios is corrected based on an outlet temperature of the intercooler .

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