JP6079973B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device, and more particularly, to an engine control device including a variable valve lift mechanism that changes a lift amount of an engine valve.

  Conventionally, an engine having a variable valve lift mechanism that changes the lift amount of an engine valve is known. For example, Patent Document 1 discloses that an exhaust valve of an engine can be opened not only in an exhaust stroke but also in an intake stroke, and an opening operation of the exhaust valve during the intake stroke (so-called exhaust valve opening twice) is executed. An engine having a switching mechanism that switches between performing and stopping is described. In the engine of this Patent Document 1, the opening degree of the high temperature EGR valve is changed at the same timing as the switching of the opening operation of the exhaust valve.

JP 2014-173532 A

  By the way, the above-described variable valve lift mechanism generally switches the lift amount of an engine valve when the engine valve is not in an open / close operation (that is, a fully closed state). On the other hand, while the engine valve is opening and closing, the lift amount of the engine valve cannot be switched. Therefore, when the engine is a multi-cylinder engine, the variable valve lift mechanism switches the lift amount in order from the cylinder in which the engine valve is fully closed.

  Here, the variable valve lift mechanism is driven by, for example, hydraulic pressure, electromagnetic actuator, air pressure, etc., but the response characteristic of those drive mechanisms causes the engine valve lift amount switching instruction to be input to the variable valve lift mechanism. The response time until the variable valve lift mechanism completes switching of the lift amount of the engine valve varies. As a result, when an instruction for switching the lift amount of the engine valve is output to the variable valve lift mechanism at a timing immediately before the engine valve starts to open / close in a certain cylinder, the lift amount of the engine valve is switched in that cylinder. Whether the lift amount of the engine valve is switched in the cylinder with the next ignition / ignition order may vary depending on the response time variation of the variable valve lift mechanism.

  However, in the engine of Patent Document 1 described above, the opening degree of the high temperature EGR valve is not changed at the same timing as the switching instruction of the opening operation of the exhaust valve without considering the variation in the response time of the switching mechanism (variable valve lift mechanism). Since the change instruction is output, the cylinder in which the opening degree of the high temperature EGR valve has been changed does not match the cylinder in which the opening operation of the exhaust valve has been changed due to variations in the response time of the switching mechanism. A situation can arise. In this case, intended combustion control is not performed (for example, high temperature EGR and internal EGR are introduced into the cylinder at the same time, or neither high temperature EGR nor internal EGR is introduced into the cylinder), leading to abnormal combustion or misfire. There is a fear.

  The present invention was made to solve the above-described problems of the prior art, and the combustion of the engine can be reliably controlled by an appropriate combustion control parameter corresponding to the switching state of the variable valve lift mechanism. An object of the present invention is to provide an engine control device.

In order to achieve the above object, an engine control apparatus according to the present invention is an engine control apparatus having a variable valve lift mechanism that changes the lift amount of an engine valve, and detects a crank angle of the engine. Detection means, variable valve lift mechanism control means for outputting an instruction for switching the lift amount of the engine valve to the variable valve lift mechanism according to the operating state of the engine, and switching of the lift amount of the engine valve by the variable valve lift mechanism control means Combustion control means for controlling the combustion of each cylinder of the engine by selecting a combustion control parameter corresponding to the instruction, and the crank angle detected by the crank angle detection means, the variable valve lift mechanism control means After the switching instruction is output, the variable valve lift mechanism completes the switching of the lift amount of the engine valve. When the cylinder in which the lift amount of the engine valve changes due to variations in the response time until it is within a predetermined angle range that varies, the switching instruction that limits the output of the switching instruction of the lift amount of the engine valve by the variable valve lift mechanism control means And limiting means.
In the present invention configured as described above, the switching instruction limiting means changes the cylinder in which the lift amount of the engine valve is switched due to the variation in the response time of the variable valve lift mechanism. When the angle is within a predetermined angle range, the variable valve lift mechanism control means restricts the output of the engine valve lift amount switching instruction, so that the variable valve can be used only when the cylinder to which the engine valve lift amount is switched can be reliably identified. The lift mechanism control means can output an instruction to switch the lift amount of the engine valve, whereby the combustion of the engine can be reliably controlled with an appropriate combustion control parameter corresponding to the switching state of the variable valve lift mechanism. .

In the present invention, preferably, the variable valve lift mechanism is operated by hydraulic pressure.
In the present invention configured as described above, due to the characteristics of the hydraulic drive mechanism, the variable valve lift mechanism control means outputs the engine valve lift amount switching instruction and the variable valve lift mechanism switches the engine valve lift amount. It is assumed that there will be some variation in response time until the engine is completed, but even in that case, combustion of the engine can be reliably controlled by an appropriate combustion control parameter corresponding to the switching state of the variable valve lift mechanism. .

In the present invention, it is preferable that the engine control device further includes a hydraulic pressure detection unit that detects a hydraulic pressure of hydraulic oil supplied to the variable valve lift mechanism, and the switching instruction limiting unit is detected by the hydraulic pressure detection unit. The higher the hydraulic pressure, the narrower the predetermined crank angle range that limits the output of the engine valve lift amount switching instruction.
In the present invention configured as described above, the variable valve lift mechanism has a response speed that increases as the hydraulic pressure increases, so that the response speed of the variable valve lift mechanism increases and response time variation decreases. The range of the angle range that restricts the output of the engine valve lift amount switching instruction can be reduced in accordance with the characteristics of the engine valve, thereby enabling the variable valve lift mechanism to switch the engine valve lift amount as early as possible. It can be carried out.

In the present invention, it is preferable that the engine control device further includes an oil temperature detecting unit that detects an oil temperature of the hydraulic oil supplied to the variable valve lift mechanism, and the switching instruction limiting unit includes the oil temperature detecting unit. The higher the oil temperature detected by the means, the narrower the predetermined crank angle range that limits the output of the engine valve lift amount switching instruction.
In the present invention configured as described above, the variable valve lift mechanism has a response speed that is increased by decreasing the viscosity of the hydraulic oil of the variable valve lift mechanism as the oil temperature increases, and the variation in response time is reduced. According to the characteristics of the valve lift mechanism, it is possible to reduce the width of the angle range that restricts the output of the engine valve lift amount switching instruction, thereby enabling the variable valve lift mechanism to switch the engine valve lift amount. As early as possible.

In the present invention, preferably, the engine control device further includes an engine water temperature detecting means for detecting the engine water temperature, and the switching instruction limiting means increases the water temperature detected by the engine water temperature detecting means. The predetermined angle range of the crank angle that limits the output of the engine valve lift amount switching instruction is narrowed.
In the present invention configured as above, the oil temperature of the hydraulic oil of the variable valve lift mechanism increases as the water temperature increases, and the viscosity of the hydraulic oil decreases accordingly, so that the response speed of the variable valve lift mechanism increases. Therefore, in accordance with the characteristics of the variable valve lift mechanism that the response time variation is reduced, the width of the angle range that limits the output of the engine valve lift amount switching instruction can be reduced. The lift amount of the engine valve by the mechanism can be switched as early as possible.

In the present invention, it is preferable that the engine control device further includes an engine speed detecting means for detecting the engine speed, and the switching instruction limiting means is the engine speed detected by the engine speed detecting means. The lower the value, the narrower the predetermined angle range of the crank angle that limits the output of the engine valve lift amount switching instruction.
In the present invention configured as described above, the lower the engine speed, the smaller the rotation angle of the crankshaft during the response time of the variable valve lift mechanism, thereby responding to variations in the response time of the variable valve lift mechanism. In accordance with the characteristics of the variable valve lift mechanism that the crank angle width is reduced, the width of the angle range that limits the output of the engine valve lift amount switching instruction can be reduced. The engine valve lift amount can be switched as early as possible.

In the present invention, it is preferable that the switching instruction limiting means is a predetermined crank angle that limits output of an engine valve lift amount switching instruction when the hydraulic oil supplied to the variable valve lift mechanism is depressurized. The range is narrower than when hydraulic fluid supplied to the variable valve lift mechanism is pressurized.
In the present invention configured as above, the response speed of the variable valve lift mechanism when the hydraulic oil supplied to the variable valve lift mechanism is depressurized is the hydraulic oil supplied to the variable valve lift mechanism being pressurized. When the operating speed is faster than the response speed of the variable valve lift mechanism, the variation in response time when the hydraulic oil is discharged from the variable valve lift mechanism is smaller than when the hydraulic oil is supplied to the variable valve lift mechanism. In accordance with the characteristics of the variable valve lift mechanism, the range of the angle range that limits the output of the engine valve lift amount switching instruction can be reduced, which allows the variable valve lift mechanism to switch the engine valve lift amount. Can be done as early as possible.

In the present invention, preferably, the engine is an engine whose combustion mode is switched to premixed compression self-ignition combustion or spark ignition combustion, and the variable valve lift mechanism control means is configured to switch the combustion mode of the engine, An instruction for switching the lift amount of the engine valve is output to the variable valve lift mechanism.
In the present invention configured as described above, the engine is configured to switch between premixed compression self-ignition combustion and spark ignition combustion, and even when combustion control parameters that are greatly different are used in the respective combustion methods. Since the variable valve lift mechanism control means outputs the engine valve lift amount switching instruction only when the cylinder to which the engine valve lift amount is switched can be reliably identified, an appropriate value corresponding to the switching state of the variable valve lift mechanism is output. It is particularly advantageous that the combustion of the engine can be reliably controlled by the combustion control parameters.

  According to the engine control apparatus of the present invention, the combustion of the engine can be reliably controlled by an appropriate combustion control parameter corresponding to the switching state of the variable valve lift mechanism.

1 is a schematic configuration diagram of an engine to which an engine control device according to an embodiment of the present invention is applied. It is a block diagram which shows the electrical structure regarding the control apparatus of the engine by embodiment of this invention. It is explanatory drawing of the driving | operation area | region of the engine by embodiment of this invention. It is a diagram which shows the lift curve of the intake valve and exhaust valve by embodiment of this invention, (a) is the low load side of the HCCI area | region of an engine, (b) is the high load side of the HCCI area | region of an engine, (c). FIG. 4 is a diagram showing lift curves of intake valves and exhaust valves in the SI region of the engine. It is a graph which illustrates the switching instruction | command limitation angle range in which the switching instruction | indication of the variable valve lift mechanism by embodiment of this invention is restrict | limited. It is the diagram which showed the relationship between each parameter which affects the switching instruction | command limitation angle range of the variable valve lift mechanism by embodiment of this invention, and a switching instruction | command limitation angle range, (a) is oil_pressure | hydraulic, (b) is Oil temperature or water temperature, (c) is a diagram showing the relationship between the engine speed and the switching instruction limit angle range. It is a flowchart of the switching process of the operation mode of the exhaust valve by embodiment of this invention. (A) Change in the operation region, (b) Change in and out of the crank angle switching instruction limit range, and (c) To the VVL 71 by the PCM 10 when the operation region of the engine according to the embodiment of the present invention is switched from the HCCI region to the SI region. 6 is a time chart showing a change in the switching instruction output, (d) a change in the exhaust valve operation mode, (e) a change in the fuel injection mode, and (f) a change in the spark ignition mode.

  Hereinafter, an engine control apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[Device configuration]
FIG. 1 shows a schematic configuration of an engine (engine body) 1 to which an engine control device according to an embodiment of the present invention is applied, and FIG. 2 is a block diagram showing the engine control device according to the embodiment of the present invention. .

  The engine 1 is a gasoline engine that is mounted on a vehicle and supplied with a fuel containing at least gasoline. The engine 1 includes a cylinder block 11 provided with a plurality of cylinders 18 (in FIG. 1, only one cylinder is illustrated, but four cylinders are provided in series, for example), and the cylinder block 11 is disposed on the cylinder block 11. The cylinder head 12 is provided, and an oil pan 13 is provided below the cylinder block 11 and stores lubricating oil. A piston 14 connected to the crankshaft 15 via a connecting rod 142 is fitted in each cylinder 18 so as to be able to reciprocate. A cavity 141 like a reentrant type in a diesel engine is formed on the top surface of the piston 14. The cavity 141 is opposed to an injector 67 described later when the piston 14 is positioned near the compression top dead center. The cylinder head 12, the cylinder 18, and the piston 14 having the cavity 141 define a combustion chamber 19. The shape of the combustion chamber 19 is not limited to the shape illustrated. For example, the shape of the cavity 141, the top surface shape of the piston 14, the shape of the ceiling portion of the combustion chamber 19, and the like can be changed as appropriate.

  The engine 1 is set to a relatively high geometric compression ratio of 15 or more for the purpose of improving the theoretical thermal efficiency and stabilizing the compression ignition combustion described later. In addition, what is necessary is just to set a geometric compression ratio suitably in the range of about 15-20.

  The cylinder head 12 is formed with an intake port 16 and an exhaust port 17 for each cylinder 18. The intake port 16 and the exhaust port 17 have an intake valve 21 and an exhaust for opening and closing the opening on the combustion chamber 19 side. Valves 22 are respectively provided.

  Of the valve systems that drive the intake valve 21 and the exhaust valve 22, respectively, on the exhaust side, the operation mode of the exhaust valve 22 is switched between a normal mode and a special mode, for example, a hydraulically operated variable valve lift mechanism (FIG. 2). (Hereinafter referred to as VVL (Variable Valve Lift)) 71 and a phase variable mechanism (hereinafter referred to as VVT (Variable Valve Timing)) 75 capable of changing the rotational phase of the exhaust camshaft with respect to the crankshaft 15. , Is provided. Although the detailed illustration of the configuration of the VVL 71 is omitted, two types of cams having different cam profiles, a first cam having one cam crest and a second cam having two cam crests, and its first And a lost motion mechanism that selectively transmits the operating state of one of the second cams to the exhaust valve 22. When the operating state of the first cam is transmitted to the exhaust valve 22, the exhaust valve 22 operates in the normal mode in which the valve is opened only once during the exhaust stroke, whereas the operating state of the second cam is the exhaust valve. When transmitting to the engine 22, the exhaust valve 22 is operated in a special mode in which the exhaust valve is opened during the exhaust stroke and is also opened during the intake stroke so that the exhaust is opened twice. The normal mode and the special mode of the VVL 71 are switched according to the operating state of the engine. Specifically, the special mode is used in the control related to the internal EGR. An electromagnetically driven valve system that drives the exhaust valve 22 by an electromagnetic actuator may be employed.

  The execution of the internal EGR is not realized only by opening the exhaust twice. For example, the internal EGR control may be performed by opening the intake valve 21 twice or by opening the intake valve twice, or by providing a negative overlap period in which both the intake valve 21 and the exhaust valve 22 are closed in the exhaust stroke or the intake stroke. Internal EGR control that causes the fuel gas to remain in the cylinder 18 may be performed.

  The VVT 75 may employ a hydraulic, electromagnetic, or mechanical structure as appropriate, and illustration of the detailed structure is omitted. The exhaust valve 22 can continuously change the valve opening timing and valve closing timing within a predetermined range by the VVT 75.

  As shown in FIG. 2, a VVL 74 and a VVT 72 are provided on the intake side in the same manner as the valve system on the exhaust side provided with the VVL 71 and the VVT 75. The intake side VVL 74 is different from the exhaust side VVL 71. The VVL 74 on the intake side includes two types of cams having different cam profiles: a large lift cam that relatively increases the lift amount of the intake valve 21 and a small lift cam that relatively decreases the lift amount of the intake valve 21; and The lost motion mechanism is configured to selectively transmit the operating state of one of the large lift cam and the small lift cam to the intake valve 21. When the VVL 74 is transmitting the operating state of the large lift cam to the intake valve 21, the intake valve 21 is opened with a relatively large lift amount, and the valve opening period is also lengthened. On the other hand, when the VVL 74 is transmitting the operating state of the small lift cam to the intake valve 21, the intake valve 21 is opened with a relatively small lift amount and the valve opening period is also shortened. The large lift cam and the small lift cam are set to be switched at the same valve closing timing or valve opening timing.

  As with the VVT 75 on the exhaust side, the intake-side VVT 72 may adopt a known hydraulic, electromagnetic, or mechanical structure as appropriate, and the detailed structure is not shown. The intake valve 21 can also continuously change its valve opening timing and valve closing timing within a predetermined range by the VVT 72. Note that, instead of applying the VVL 74 to the intake side, only the VVT 72 may be applied and only the valve opening timing and the valve closing timing of the intake valve 21 may be changed.

  In addition, for each cylinder 18, an injector 67 that directly injects fuel into the cylinder 18 (direct injection) is attached to the cylinder head 12. The injector 67 is disposed so that its nozzle hole faces the inside of the combustion chamber 19 from the central portion of the ceiling surface of the combustion chamber 19. The injector 67 directly injects an amount of fuel into the combustion chamber 19 at an injection timing set according to the operating state of the engine 1 and according to the operating state of the engine 1. In this example, the injector 67 is a multi-hole injector having a plurality of nozzle holes, although detailed illustration is omitted. Thereby, the injector 67 injects the fuel so that the fuel spray spreads radially from the center position of the combustion chamber 19. At the timing when the piston 14 is positioned near the compression top dead center, the fuel spray injected radially from the central portion of the combustion chamber 19 flows along the wall surface of the cavity 141 formed on the top surface of the piston. It can be paraphrased that the cavity 141 is formed so that the fuel spray injected at the timing when the piston 14 is located near the compression top dead center is contained therein. This combination of the multi-hole injector 67 and the cavity 141 is an advantageous configuration for shortening the mixture formation period and the combustion period after fuel injection. In addition, the injector 67 is not limited to a multi-hole injector, and may be an open valve type injector.

  A fuel tank (not shown) and the injector 67 are connected to each other by a fuel supply path. A fuel supply system 62 including a fuel pump 63 and a common rail 64 and capable of supplying fuel to the injector 67 at a relatively high fuel pressure is interposed on the fuel supply path. The fuel pump 63 pumps fuel from the fuel tank to the common rail 64, and the common rail 64 can store the pumped fuel at a relatively high fuel pressure. When the injector 67 is opened, the fuel stored in the common rail 64 is injected from the injection port of the injector 67. Here, although not shown, the fuel pump 63 is a plunger type pump and is driven by the engine 1. The fuel supply system 62 configured to include this engine-driven pump enables the fuel with a high fuel pressure of 30 MPa or more to be supplied to the injector 67. The fuel pressure may be set to about 120 MPa at the maximum. The pressure of the fuel supplied to the injector 67 is changed according to the operating state of the engine 1 as will be described later. The fuel supply system 62 is not limited to this configuration.

  A spark plug 25 that forcibly ignites the air-fuel mixture in the combustion chamber 19 is also attached to the cylinder head 12. In this example, the spark plug 25 is disposed through the cylinder head 12 so as to extend obliquely downward from the exhaust side of the engine 1. The tip of the spark plug 25 is disposed facing the cavity 141 of the piston 14 located at the compression top dead center.

  As shown in FIG. 1, an intake passage 30 is connected to one side of the engine 1 so as to communicate with the intake port 16 of each cylinder 18. On the other hand, an exhaust passage 40 for discharging burned gas (exhaust gas) from the combustion chamber 19 of each cylinder 18 is connected to the other side of the engine 1.

  An air cleaner 31 that filters intake air is disposed at the upstream end of the intake passage 30, and a throttle valve 36 that adjusts the amount of intake air to each cylinder 18 is disposed downstream thereof. A surge tank 33 is disposed near the downstream end of the intake passage 30. The intake passage 30 on the downstream side of the surge tank 33 is an independent passage branched for each cylinder 18, and the downstream end of each independent passage is connected to the intake port 16 of each cylinder 18.

Between the throttle valve 36 and the surge tank 33 in the intake passage 30, an ozone generator (O ₃ generator) 76 that adds ozone to fresh air introduced into the cylinder 18 is interposed. The ozone generator 76 generates ozone by silent discharge using oxygen contained in the intake air as a source gas. That is, when a high frequency alternating current high voltage is applied to the electrode from a power source (not shown), silent discharge is generated in the discharge gap, and the air (that is, intake air) passing therethrough is ozonized. The intake air thus added with ozone is introduced into each cylinder 18 from the surge tank 33 via the intake port 16. The ozone concentration in the intake air after passing through the ozone generator 76 is adjusted by changing the voltage application mode to the electrodes of the ozone generator 76 and / or changing the number of electrodes to which the voltage is applied. It is possible. The PCM 10 adjusts the ozone concentration in the intake air introduced into the cylinder 18 through the control of the ozone generator 76.

  The upstream portion of the exhaust passage 40 is constituted by an exhaust manifold having an independent passage branched for each cylinder 18 and connected to the outer end of the exhaust port 17 and a collecting portion where the independent passages gather. A direct catalyst 41 and an underfoot catalyst 42 are connected downstream of the exhaust manifold in the exhaust passage 40 as exhaust purification devices for purifying harmful components in the exhaust gas. Each of the direct catalyst 41 and the underfoot catalyst 42 includes a cylindrical case and, for example, a three-way catalyst disposed in a flow path in the case.

  A portion between the surge tank 33 and the throttle valve 36 in the intake passage 30 and a portion upstream of the direct catalyst 41 in the exhaust passage 40 are used for returning a part of the exhaust gas to the intake passage 30. They are connected via a passage 50. The EGR passage 50 includes a main passage 51 in which an EGR cooler 52 for cooling the exhaust gas with engine coolant is disposed. The main passage 51 is provided with an EGR valve 511 for adjusting the recirculation amount of the exhaust gas to the intake passage 30.

  The engine 1 is controlled by a powertrain control module (hereinafter referred to as PCM) 10. The PCM 10 includes a microprocessor having a CPU, a memory, a counter timer group, an interface, and a path connecting these units. This PCM 10 constitutes a controller.

As shown in FIGS. 1 and 2, detection signals from various sensors SW 1, SW 2, SW 4 to SW 18 are input to the PCM 10. Specifically, on the downstream side of the air cleaner 31, the PCM 10 includes a detection signal of an air flow sensor SW 1 that detects a flow rate of fresh air, a detection signal of an intake air temperature sensor SW 2 that detects the temperature of fresh air, and an EGR passage 50. The detection signal of the EGR gas temperature sensor SW4 that is disposed in the vicinity of the connection portion with the intake passage 30 and detects the temperature of the external EGR gas, and the intake air that is attached to the intake port 16 and immediately before flowing into the cylinder 18 The detection signal of the intake port temperature sensor SW5 for detecting the temperature, the detection signal of the in-cylinder pressure sensor SW6 attached to the cylinder head 12 and detecting the pressure in the cylinder 18, and the vicinity of the connection portion of the EGR passage 50 in the exhaust passage 40 And the detection signals of the exhaust temperature sensor SW7 and the exhaust pressure sensor SW8 that detect the exhaust temperature and the exhaust pressure, respectively. And it is disposed on the upstream side of the direct catalyst 41, disposed between the detection signal of the linear O ₂ sensor SW9 for detecting the oxygen concentration in the exhaust gas, the direct catalyst 41 and underfoot catalyst 42 and the exhaust A detection signal of a lambda O ₂ sensor SW10 that detects the oxygen concentration of the engine, a detection signal of a water temperature sensor SW11 that detects the temperature of engine cooling water, a detection signal of a crank angle sensor SW12 that detects the rotation angle of the crankshaft 15, A detection signal of an accelerator opening sensor SW13 that detects an accelerator opening corresponding to an operation amount of an accelerator pedal (not shown) of the vehicle, detection signals of intake side and exhaust side cam angle sensors SW14 and SW15, and a fuel supply system A fuel pressure sensor S that is attached to the common rail 64 of 62 and detects the fuel pressure supplied to the injector 67. 16 a detection signal of a detection signal of the hydraulic sensor SW17 for detecting the oil pressure of the engine 1, and the detection signal of the oil temperature sensor SW18 for detecting the oil temperature of the engine 1, are input.

  The PCM 10 determines the state of the engine 1 and the vehicle by performing various calculations based on these detection signals, and accordingly, the injector 67, the spark plug 25, the VVT 72 and VVL 74 on the intake valve side, and the exhaust valve side Control signals are output to the VVT 75 and VVL 71, the fuel supply system 62, actuators of various valves (throttle valve 36, EGR valve 511), and the ozone generator 76. Thus, the PCM 10 operates the engine 1. Although details will be described later, the PCM 10 corresponds to an engine control device in the present invention, and functions as a variable valve lift mechanism control means, a combustion control means, and a switching instruction restriction means.

[Operation area]
Next, with reference to FIG. 3, the operating region of the engine according to the embodiment of the present invention will be described. FIG. 3 shows an example of the operation control map of the engine 1. In order to improve fuel efficiency and exhaust emission performance, the engine 1 is not subjected to ignition by the spark plug 25 in a low load region where the engine load is relatively low, and is premixed compression self-ignition (Homogeneous-Charge Compression) Compression ignition combustion by Ignition (HCCI) is performed. However, as the load on the engine 1 increases, in the compression ignition combustion, the combustion becomes too steep and causes problems such as combustion noise. Therefore, in the engine 1, in a high load region where the engine load is relatively high, compression ignition combustion is stopped and switched to forced ignition combustion (here, spark ignition combustion (SI)) using the spark plug 25. . As described above, the engine 1 is configured to switch between the HCCI mode in which the premixed compression self-ignition combustion is performed and the SI mode in which the spark ignition combustion is performed in accordance with the operation state of the engine 1, in particular, the load of the engine 1. ing. However, the boundary line for mode switching is not limited to the illustrated example.

[Operation of intake valve and exhaust valve]
Next, operations of the intake valve and the exhaust valve according to the embodiment of the present invention will be described with reference to FIG. 4A and 4B are diagrams showing lift curves of an intake valve and an exhaust valve according to an embodiment of the present invention, where FIG. 4A is a low load side of the HCCI region of the engine, and FIG. 4B is a high load side of the HCCI region of the engine. (C) shows an example of lift curves of the intake valve and the exhaust valve in the SI region of the engine.

The profile of the small lift cam in the intake side VVL 74 has one cam crest having a relatively small lift amount as illustrated by the solid line in FIGS. 4A and 4B, and the large lift cam in the intake side VVL 74. This profile has one cam crest having a relatively large lift amount as illustrated by a solid line in FIG.
When the VVL 74 is transmitting the operating state of the small lift cam to the intake valve 21, as shown in FIGS. 4 (a) and (b), the intake valve 21 is opened with a relatively small lift amount. The valve opening period is also shortened. On the other hand, when the VVL 74 is transmitting the operating state of the large lift cam to the intake valve 21, as shown in FIG. 4 (c), the intake valve 21 is opened with a relatively large lift amount. The valve opening period also becomes longer. In the example of FIG. 4, the large lift cam and the small lift cam are set so as to be switched at the same valve opening timing. The valve closing timing 21 is set so as to be delayed until the compression process, and a delayed closing mirror cycle is realized.

  The cam profile of the first cam in the VVL 71 on the exhaust side is substantially constant as the crank angle advances on the valve closing side in the lift curve, as illustrated by the broken lines in FIGS. 4 (a) and 4 (b). It has a lift shelf 222 to maintain, and the cam profile of the second cam does not have a lift shelf as shown by the broken line in FIG.

  When the lost motion mechanism of the VVL 71 on the exhaust side transmits the operating state of the first cam to the exhaust valve 22, the exhaust valve 22 is opened as illustrated by broken lines in FIGS. 4 (a) and (b). After the valve is operated, the lift amount gradually increases with the progress of the crank angle. At least after reaching a predetermined peak during the exhaust stroke, the lift amount is maintained at the lift shelf 222 and then the valve is closed. Operate in mode. On the other hand, when the lost motion mechanism is transmitting the operating state of the second cam to the exhaust valve 22, the exhaust valve 22 is opened after being opened, as illustrated by a broken line in FIG. As the angle advances, the lift amount gradually increases, and at least after reaching a predetermined peak during the exhaust stroke, the lift amount gradually decreases and operates in a normal mode in which the valve is closed as it is. The normal mode and the special mode of the VVL 71 are switched according to the operating state of the engine 1. Specifically, the special mode is used when the internal EGR gas is introduced into the cylinder 18, and the normal mode is other than that. Used when In the following description, operating the VVL 71 in the normal mode is referred to as “turning off the VVL 71”, and operating the VVL 71 in the special mode and performing the internal EGR control is referred to as “turning on the VVL 71”. There is a case.

  Here, the cam profile of the first cam in the VVL 71 on the exhaust side will be described in more detail with reference to FIGS. 4 (a) and 4 (b). The broken line in FIG. 4A is the lift curve 221 of the exhaust valve 22 when the phase of the closing timing of the exhaust valve 22 is set to the most retarded side, and the broken line in FIG. This is the lift curve 221 of the exhaust valve 22 when the phase of the closing timing is set to the most advanced side. As described above, the first cam is configured to have the lift shelf 222 on the valve closing side of the lift curve 221. Here, the valve closing side in the lift curve 221 corresponds to the valve closing side when the both sides sandwiching the peak in the lift curve 221 are divided into the valve opening side and the valve closing side. As shown in FIG. 4A, when the phase of the closing timing of the exhaust valve 22 is retarded by the VVT 75, the lift shelf 222 is positioned at least in the first half of the intake stroke. The “first half” here corresponds to the first half when the intake stroke is divided into the first half and the second half. Accordingly, part of the exhaust gas discharged to the exhaust port 17 during the exhaust stroke is returned to the cylinder 18 as the exhaust valve 22 is opened during the intake stroke. Thus, a part of the exhaust gas substantially remains in the cylinder 18 (that is, internal EGR control).

The lift amount of the lift shelf 222 is set to a lift amount lower than the peak of the lift curve 221. As shown in FIG. 4A, when the phase of the opening / closing timing of the exhaust valve 22 is retarded by the VVT 75, the lift shelf 222 may be positioned at the top dead center (TDC). Therefore, in the embodiment, the lift amount of the lift shelf 222 is set to be the maximum lift amount as long as it does not interfere with the upper surface of the piston 14 located at the top dead center. In this way, the maximum amount of internal EGR can be set as large as possible. For example, the lift amount of the lift shelf 222 can be appropriately set within a range of 1/2 or less with respect to the lift amount at the peak of the lift curve 221.
Further, the length of the lift shelf 222 (that is, the length of the crank angle in the traveling direction) can satisfy the required maximum internal EGR gas amount based on the maximum lift amount that can be set. Is set.

  In the special mode of the exhaust valve 22, as shown in FIG. 4, after opening the valve in the exhaust stroke, the cam is maintained in the open state through the lift shelf 222 and then closed in the intake stroke. Instead of the profile, a cam profile that once closes after opening in the exhaust stroke and then opens again in the intake stroke may be employed.

[Engine valve lift amount switching instruction limit angle range]
Next, an angle range in which the PCM 10 according to the embodiment of the present invention limits the lift amount switching instruction of the exhaust valve 22 will be described with reference to FIGS. 5 and 6. FIG. 5 is a graph illustrating a switching instruction limit angle range in which a switching instruction of the VVL 71 according to the embodiment of the present invention is limited in an in-line four-cylinder engine. In the following description, a cylinder serving as a reference for specifying the timing at which the PCM 10 outputs an instruction to switch the operation mode of the exhaust valve 22 to the VVL 71 is referred to as a first cylinder, and each cylinder is defined as a second cylinder according to the subsequent ignition / ignition sequence. The third cylinder and the fourth cylinder are assumed.
FIG. 6 is a diagram showing the relationship between each parameter affecting the switching instruction limit angle range of the VVL 71 and the switching instruction limit angle range according to the embodiment of the present invention, where (a) is the hydraulic pressure, and (b) is the hydraulic pressure. Oil temperature or water temperature, (c) is a diagram showing the relationship between the engine speed and the switching instruction limit angle range.

First, in the graph of FIG. 5, in the operation state where the engine speed is 1000 rpm, the water temperature is 88 ° C., the oil temperature is 90 ° C., and the oil pressure is high, the operation region of the engine 1 is switched from the HCCI region to the SI region. The case where the PCM 10 outputs an instruction for switching the operation mode of the exhaust valve 22 to the VVL 71 is illustrated.
The horizontal axis in FIG. 5 represents the timing at which the PCM 10 outputs an instruction to switch the operation mode of the exhaust valve 22 to the VVL 71 as a crank angle before the compression top dead center (BTDC) of the first cylinder. The vertical axis in FIG. 5 represents the crank angle margin from when the VVL 71 completes the switching of the operation mode of the exhaust valve 22 to when the exhaust valve 22 starts to operate.

  When the crank angle of the first cylinder is 720 degrees BTDC, after the PCM 10 outputs an instruction to switch the operation mode of the exhaust valve 22 to the VVL 71, the first cylinder in which the exhaust valve 22 opens in the operation mode after switching (that is, The cylinder with the smallest crank angle margin after the VVL 71 completes the switching of the operation mode of the exhaust valve 22 until the exhaust valve 22 starts to operate) depends on the response speed of the VVL 71, the engine speed at that time, etc. However, in the example of FIG. 5, the first cylinder in which the exhaust valve 22 opens in the operation mode after switching is the second cylinder.

  Specifically, as shown in FIG. 5, when the crank angle of the first cylinder is 720 ° BTDC and the PCM 10 outputs an instruction to switch the operation mode of the exhaust valve 22 to the VVL 71, the VVL 71 of the second cylinder is exhausted. The crank angle margin from the completion of the switching of the operation mode of the valve 22 to the start of the operation of the exhaust valve 22 is secured about 120 degrees. Therefore, in this case, the operation mode of the exhaust valve 22 is reliably switched in the second cylinder. Note that the specific value of the crank angle margin is determined according to the response speed of the VVL 71, the engine speed at that time, and the like.

  On the other hand, if the PCM 10 outputs an instruction for switching the operation mode of the exhaust valve 22 to the VVL 71 when the crank angle of the first cylinder is near 600 degrees BTDC, the VVL 71 of the second cylinder completes the switching of the operation mode of the exhaust valve 22. After that, the crank angle margin from when the exhaust valve 22 starts to operate is hardly ensured. In this case, the operation mode of the exhaust valve 22 may be switched in the second cylinder due to variations in the response time of the VVL 71, or the operation mode of the exhaust valve 22 may be switched to start the operation of the exhaust valve 22 in the second cylinder. Since the operation mode of the exhaust valve 22 may be switched in the next third cylinder without being in time, it cannot be specified in which cylinder the operation mode of the exhaust valve 22 is switched.

Therefore, in the PCM 10 of the present embodiment, when the crank angle of the first cylinder is within the angle range (switching instruction limit angle range) of width θ degrees centering on 600 degrees BTDC, the operation mode of the exhaust valve 22 with respect to the VVL 71 is set. Limit the output of switching instructions.
Similarly, the PCM 10 according to the present embodiment can also be used with respect to the VVL 71 even when the crank angle of the first cylinder is within an angle range of width θ degrees centering around 420 degrees BTDC, 240 degrees BTDC, and 60 degrees BTDC. The output of the switching instruction of the operation mode of the exhaust valve 22 is limited.
As a result, the PCM 10 can output an instruction to switch the operation mode of the exhaust valve 22 by the VVL 71 only when the cylinder in which the operation mode of the exhaust valve 22 is switched can be reliably identified.

Next, the graph of FIG. 6 represents the relationship between the width θ of the switching instruction limit angle range and each parameter that affects the width θ.
First, under the condition that the other parameters are constant, the driving force of the VVL 71 increases as the hydraulic pressure of the engine 1 increases, so that the response speed of the VVL 71 increases and the variation in response time decreases. Accordingly, as shown in FIG. 6A, the higher the oil pressure detected by the oil pressure sensor SW17, the narrower the width θ of the switching instruction limit angle range is set.

  Next, under the condition that the other parameters are constant, the viscosity of the hydraulic fluid of the VVL 71 decreases as the oil temperature or water temperature of the engine 1 increases, so the response speed of the VVL 71 increases and the variation in response time decreases. Therefore, as shown in FIG. 6B, the higher the oil temperature detected by the oil temperature sensor SW18 or the water temperature detected by the water temperature sensor SW11, the narrower the width θ of the switching instruction limit angle range is set.

  Next, under the condition that the other parameters are constant, the rotation angle of the crankshaft 15 during the response time of the VVL 71 becomes smaller as the rotational speed of the engine 1 becomes lower, so that the crank angle corresponding to the variation in the response time of the VVL 71 is reduced. The width of becomes smaller. Therefore, as shown in FIG. 6 (c), the lower the rotational speed of the engine 1 detected by the crank angle sensor SW12, the narrower the width θ of the switching instruction limit angle range is set.

  Furthermore, the width θ of the switching instruction limit angle range can be changed according to the switching direction of the operation mode of the exhaust valve 22 by the VVL 71 (that is, the switching direction of the operation region of the engine 1). For example, the response speed of the VVL 71 when the hydraulic fluid supplied to the VVL 71 is depressurized (that is, when the hydraulic fluid is discharged from the VVL 71) under the condition that the other parameters are constant is the hydraulic fluid supplied to the VVL 71. When the hydraulic pressure is higher than the response speed of the VVL 71 when the hydraulic fluid is pressurized (that is, when the hydraulic fluid is supplied to the VVL 71), the dispersion of the response time when the hydraulic fluid is discharged from the VVL 71 causes the hydraulic fluid to be supplied to the VVL 71. Will be smaller than when Therefore, the width θ of the switching instruction limit angle range when the hydraulic fluid supplied to the VVL 71 is depressurized is set narrower than when the hydraulic fluid supplied to the VVL 71 is pressurized.

[Exhaust valve operation mode switching by VVL]
Next, the operation mode switching process of the exhaust valve 22 according to the embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a flowchart of the process for switching the operation mode of the exhaust valve 22 according to the embodiment of the present invention, and FIG. 8 is a flowchart when the operation region of the engine 1 according to the embodiment of the present invention is switched from the HCCI region to the SI region. (A) Change in operating region, (b) Change in and out of crank angle switching instruction limit range, (c) Change in switching instruction output to VVL 71 by PCM 10, (d) Change in operation mode of exhaust valve 22, (e It is a time chart which shows the change of fuel injection mode, and the change of (f) spark ignition mode. The process shown in FIG. 7 is repeatedly executed by the PCM 10 at a predetermined cycle when the vehicle is driven.

  As shown in FIG. 7, when the process for switching the operation mode of the exhaust valve 22 is started, first, in step S1, the PCM 10 determines the operating state of the engine 1 based on detection signals input from various sensors. get.

  Next, in step S2, the PCM 10 determines whether or not the operating region of the engine 1 exceeds the boundary between the SI region and the HCCI region. As a result, when the operation region of the engine 1 does not exceed the boundary between the SI region and the HCCI region, it is not necessary to switch the operation mode of the exhaust valve 22, so the PCM 10 ends the process.

  On the other hand, when the operation region of the engine 1 exceeds the boundary between the SI region and the HCCI region in step S2, the process proceeds to step S3, and the PCM 10 determines each parameter (for example, the influence of the switching instruction limit angle range width θ). Oil pressure, oil temperature, water temperature, engine speed, switching direction of the operating region of the engine 1, etc.).

  Next, in step S4, the PCM 10 determines the position of the switching instruction limit angle range (for example, the crank angle represented by BTDC of the first cylinder) based on the operating state of the engine 1 acquired in step S1 and the parameter acquired in step S3. And obtaining the width θ, the switching instruction limit angle range is set.

  Next, in step S5, the PCM 10 acquires the crank angle detected by the crank angle sensor SW12. Next, in step S6, the PCM 10 determines whether or not the crank angle acquired in step S5 is outside the switching instruction limit angle range set in step S4.

As a result, when the crank angle acquired in step S5 is outside the switching instruction limit angle range set in step S4, the process proceeds to step S7, and the PCM 10 sets the operation mode of the exhaust valve 22 according to the switching direction of the operation region. An instruction to switch is output to the VVL 71, and then the process ends.
On the other hand, if the crank angle acquired in step S5 is not outside the switching instruction limit angle range set in step S4 (if it is within the switching instruction limit angle range), the PCM 10 issues an instruction to switch the operation mode of the exhaust valve 22 to VVL71. The process is terminated without outputting to.

For example, as shown in FIG. 8 (a), when the operation region of the engine 1 is switched from the HCCI region to the SI region at time T1, the conventional engine control device uses FIGS. 8 (c), 8 (e) and (e). As indicated by the one-dot chain line in f), an instruction to switch the operation mode of the exhaust valve from the special mode to the normal mode is immediately output to the VVL of the cylinder A in which the exhaust valve is first opened after time T1, and the cylinder A The fuel injection mode is switched from the HCCI mode to the SI mode, and the spark ignition mode is switched from OFF to ON.
However, as shown in FIG. 8B, when the crank angle at the time T1 is within the switching instruction limit angle range, as shown in FIG. 8D, the first time after the time T1 due to the variation in the response time of the VVL. In some cases, the operation mode of the exhaust valve is not switched in the cylinder A in which the exhaust valve is opened, and the operation mode of the exhaust valve is switched in the next cylinder B. Even in this case, as described above, the fuel injection mode in the cylinder A in which the exhaust valve first opens after time T1 is switched to the SI mode, and the spark ignition mode is switched to ON. Although the exhaust valve is still operating in the special mode corresponding to the HCCI region, the fuel injection and spark ignition are controlled corresponding to the SI region. As a result, abnormal combustion or misfire may occur in the cylinder A.

On the other hand, in the PCM 10 of the present embodiment, even when the operation region of the engine 1 is switched from the HCCI region to the SI region at time T1, the crank angle at time T1 is within the switching instruction limit angle range as shown in FIG. Therefore, as indicated by a solid line in FIG. 8C, an instruction to switch the operation mode of the exhaust valve 22 from the special mode to the normal mode is immediately given to the VVL 71 of the cylinder A that opens the exhaust valve first after time T1. Rather than output, when the crank angle is outside the switching instruction limit angle range at time T2, it is output to the VVL 71 of the next cylinder B, and the fuel injection mode in that cylinder B is changed from the HCCI mode to the SI mode. Switch and switch the spark ignition mode from OFF to ON.
Therefore, in the cylinder A, control corresponding to the HCCI region is performed in all of the operation mode, the fuel injection mode, and the spark ignition mode of the exhaust valve 22, and in the next cylinder B, the operation mode of the exhaust valve 22, the fuel injection mode In both the spark ignition mode and the spark ignition mode, control corresponding to the SI region is performed.

Next, further modifications of the embodiment of the present invention will be described.
First, in the above-described embodiment, the VVL 71 is hydraulically operated, and includes two types of cams having different cam profiles, a first cam having one cam peak and a second cam having two cam peaks, and Although it has been described that it includes a lost motion mechanism that selectively transmits the operating state of one of the first and second cams to the exhaust valve 22, a VVL having a different configuration is used. Alternatively, electromagnetically driven or pneumatically driven VVL may be used.

  Further, in the above-described embodiment, the case where the switching instruction to the VVL 71 that drives the exhaust valve 22 is exemplified, but the technique disclosed here is also applied to the control of the switching instruction to the VVL 74 that drives the intake valve 21. Can be applied.

  In the above-described embodiment, the switching instruction limit angle range in which the switching instruction of the VVL 71 is limited has been described by taking an in-line four-cylinder engine as an example. However, the technique disclosed herein is also applied to a multi-cylinder engine other than the in-line four-cylinder engine. Can be applied.

  Next, functions and effects of the above-described embodiment of the present invention and the engine control device 1 according to the modification of the embodiment of the present invention will be described.

  First, the PCM 10 varies in response time from when the crank angle detected by the crank angle sensor SW12 outputs an instruction to switch the operation mode of the exhaust valve 22 until the VVL 71 completes the switching of the operation mode of the exhaust valve 22. When the cylinder to which the operation mode of the exhaust valve 22 is switched is within the switching instruction limit angle range in which the exhaust valve 22 is changed, the PCM 10 limits the output of the instruction to switch the operation mode of the exhaust valve 22 to the VVL 71. Only when it is possible to reliably identify the cylinder whose operation mode is to be switched, it is possible to output an instruction to switch the operation mode of the exhaust valve 22 by the VVL 71, which corresponds to the switching state of the operation mode of the exhaust valve 22 by the VVL 71. Reliably control engine combustion with appropriate combustion control parameters It is possible.

  In particular, when the VVL 71 is operated by hydraulic pressure, due to the characteristics of the hydraulic drive mechanism, the response time until the VVL 71 completes the switching of the operation mode of the exhaust valve 22 after the output instruction of the operation mode of the exhaust valve 22 is output to some extent. However, even in such a case, the combustion of the engine can be reliably controlled by an appropriate combustion control parameter corresponding to the switching state of the operation mode of the exhaust valve 22 by the VVL 71.

  Further, the higher the hydraulic pressure detected by the hydraulic sensor SW17, the narrower the width θ of the switching instruction limit angle range is set. Therefore, as the hydraulic pressure increases, the driving force of the VVL 71 increases and the response speed of the VVL 71 increases. The width θ of the switching instruction limit angle range can be reduced in accordance with the characteristic of the VVL 71 that response time variation is reduced, and thereby the operation mode of the exhaust valve 22 by the VVL 71 is switched as early as possible. Can do.

  Further, as the oil temperature detected by the oil temperature sensor SW18 or the water temperature detected by the water temperature sensor SW11 is higher, the width θ of the switching instruction limit angle range is set narrower. Therefore, the operation of the VVL 71 is increased as the oil temperature or the water temperature is higher. By reducing the viscosity of the oil, the response speed of the VVL 71 increases, and the width θ of the switching instruction limit angle range can be reduced in accordance with the characteristics of the VVL 71 that variations in response time are reduced. The operation mode of the exhaust valve 22 can be switched as early as possible.

  In addition, the lower the engine 1 detected by the crank angle sensor SW12, the narrower the switching instruction limit angle range width θ. Therefore, the lower the engine 1 speed, the more the crank during the response time of the VVL 71. The width θ of the switching instruction limit angle range can be reduced in accordance with the characteristics of the VVL 71 that the width of the crank angle corresponding to the variation in the response time of the VVL 71 is reduced by reducing the rotation angle of the shaft 15. Thus, the operation mode of the exhaust valve 22 by the VVL 71 can be switched as early as possible.

  Further, the width θ of the switching instruction limit angle range when the hydraulic oil supplied to the VVL 71 is depressurized is set narrower than when the hydraulic oil supplied to the VVL 71 is pressurized, and thus is supplied to the VVL 71. If the response speed of the VVL 71 when the hydraulic oil is reduced is faster than the response speed of the VVL 71 when the hydraulic oil supplied to the VVL 71 is pressurized, the response time when the hydraulic oil is discharged from the VVL 71 The width θ of the switching instruction limit angle range can be reduced in accordance with the characteristic of the VVL 71 that is smaller than when the hydraulic oil is supplied to the VVL 71, and thereby the operation of the exhaust valve 22 by the VVL 71. The mode can be switched as early as possible.

  In addition, the engine 1 is configured to switch between an HCCI mode in which premixed compression self-ignition combustion is performed and an SI mode in which spark ignition combustion is performed, and combustion control parameters that are greatly different between the HCCI mode and the SI mode are used. Even in this case, the PCM 10 outputs the instruction for switching the operation mode of the exhaust valve 22 by the VVL 71 only when the cylinder to which the operation mode of the exhaust valve 22 is switched can be reliably identified. Therefore, the switching of the operation mode of the exhaust valve 22 by the VVL 71 is performed. The combustion of the engine can be reliably controlled by an appropriate combustion control parameter corresponding to the state, which is particularly advantageous.

1 Engine (Engine body)
10 PCM
18 cylinder 22 exhaust valve 71 VVL
SW11 Water temperature sensor SW12 Crank angle sensor SW17 Oil pressure sensor SW18 Oil temperature sensor

Claims (8)

An engine control device having a variable valve lift mechanism for changing a lift amount of an engine valve,
Crank angle detecting means for detecting the crank angle of the engine;
Variable valve lift mechanism control means for outputting an instruction to switch the lift amount of the engine valve to the variable valve lift mechanism in accordance with the operating state of the engine;
Combustion control means for controlling combustion of each cylinder of the engine by selecting a combustion control parameter corresponding to an instruction to switch the lift amount of the engine valve by the variable valve lift mechanism control means;
The variable valve lift mechanism switches the lift amount of the engine valve after the variable valve lift mechanism control means outputs an instruction to switch the lift amount of the engine valve based on the crank angle detected by the crank angle detection means. When the cylinder in which the lift amount of the engine valve switches due to a variation in response time until completion is within a predetermined angle range that fluctuates, the variable valve lift mechanism control means outputs an instruction for switching the lift amount of the engine valve. An engine control device comprising: a switching instruction limiting unit for limiting.   The engine control device according to claim 1, wherein the variable valve lift mechanism is operated by hydraulic pressure. Furthermore, it has a hydraulic pressure detection means for detecting the hydraulic pressure of the hydraulic oil supplied to the variable valve lift mechanism,
The switching instruction limiting means narrows a predetermined angle range of the crank angle that limits the output of the engine valve lift amount switching instruction as the hydraulic pressure detected by the hydraulic pressure detection means is higher. The engine control device described. Furthermore, it has an oil temperature detecting means for detecting the oil temperature of the hydraulic oil supplied to the variable valve lift mechanism,
The switching instruction limiting means narrows a predetermined angle range of the crank angle that limits the output of the engine valve lift amount switching instruction as the oil temperature detected by the oil temperature detecting means is higher. The engine control apparatus according to 2 or 3. Furthermore, it has an engine water temperature detecting means for detecting the water temperature of the engine,
The switching instruction limiting means narrows a predetermined angle range of the crank angle that limits the output of the engine valve lift amount switching instruction as the water temperature detected by the engine water temperature detecting means is higher. 5. The engine control device according to any one of 1 to 4. Furthermore, it has an engine speed detecting means for detecting the engine speed,
The switching instruction limiting means narrows a predetermined angle range of the crank angle that limits the output of the engine valve lift amount switching instruction as the engine speed detected by the engine speed detecting means is lower. Item 6. The engine control device according to any one of Items 2 to 5.   The switching instruction limiting means is configured to change the predetermined angle range of the crank angle to limit the output of the engine valve lift amount switching instruction when the hydraulic oil supplied to the variable valve lift mechanism is depressurized. The engine control device according to any one of claims 2 to 6, wherein the operating oil supplied to the valve lift mechanism is narrower than when pressurized. The engine is an engine whose combustion method is switched to premixed compression self-ignition combustion or spark ignition combustion,
The variable valve lift mechanism control means outputs an instruction to switch the lift amount of the engine valve to the variable valve lift mechanism in response to switching of the combustion method of the engine. The engine control device described.

Images