JP6312050B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device, and more particularly to an engine control device including an intake valve for introducing intake air into a cylinder and a cylinder provided with an exhaust valve for discharging exhaust gas from the cylinder.

  2. Description of the Related Art Conventionally, a variable valve mechanism (in other words, a variable valve mechanism) that changes the opening / closing timing and / or lift amount of an exhaust valve and an intake valve provided in a cylinder is known. For example, in Patent Document 1, regarding an engine system including a variable valve mechanism that changes the opening and closing timing of an exhaust valve, the opening timing of the exhaust valve is retarded by the variable valve mechanism as the engine speed decreases. In addition, a technique is described in which air supplied to the exhaust passage is prevented from flowing back into the cylinder during low rotation.

JP 2010-185301 A

  As the variable valve mechanism as described above, a hydraulically operated mechanism is known in which a valve is operated using oil pressure (typically engine oil). In such a hydraulically operated variable valve mechanism, depending on the state of the oil, specifically, depending on the viscosity of the oil (which varies depending on the oil temperature, dilution rate, air mixing rate, deterioration degree, etc.) In some cases, the hydraulic pressure required for proper operation of the motor cannot be obtained. In this case, the valve cannot perform a desired operation by the variable valve mechanism. In particular, when a hydraulically operated variable valve mechanism is applied to an exhaust valve, when the hydraulic pressure necessary to operate the exhaust valve properly cannot be obtained, the lift amount of the exhaust valve is reduced, and the exhaust is reduced. There is a possibility that the in-cylinder pressure increases without being properly discharged from the cylinder, and a loss due to exhaust (pumping loss) occurs.

  The present invention has been made to solve the above-described problems of the prior art, and in an engine in which a hydraulically operated variable valve mechanism is applied to an exhaust valve, the variable valve mechanism is independent of the state of oil. An object of the present invention is to provide an engine control device that can cause an exhaust valve to perform a desired operation.

In order to achieve the above object, the present invention provides an engine control device including an intake valve for introducing intake air into a cylinder and a cylinder provided with an exhaust valve for discharging exhaust gas from the cylinder. A hydraulically operated variable valve mechanism configured to operate the exhaust valve using hydraulic pressure, and to change the opening / closing timing of the exhaust valve, and a variable valve mechanism to change the opening / closing timing of the exhaust valve. The variable valve mechanism is configured such that the lift amount decreases as the exhaust valve opening timing is retarded from a predetermined reference timing. The in-cylinder pressure in the vicinity of the exhaust top dead center is acquired as the in-cylinder pressure at a predetermined timing during the valve opening period of the exhaust valve by the valve mechanism, and the opening timing of the exhaust valve is advanced as the in-cylinder pressure increases. The timing for controlling the variable valve mechanism is corrected. To.

  According to the present invention configured as described above, the variable valve mechanism is configured to switch the exhaust valve from the closed state to the open state based on the magnitude of the in-cylinder pressure indicating the state of the oil (such as viscosity). Since the control timing is corrected, the exhaust valve opening timing is advanced as the in-cylinder pressure increases, so the exhaust-side variable valve mechanism is controlled at a timing that properly takes into account the oil state. be able to. Therefore, it is possible to cause the exhaust valve to perform a desired operation by the variable valve mechanism regardless of the state of oil, that is, it is possible to appropriately ensure the lift amount during the valve opening period of the exhaust valve. Thereby, the loss (pumping loss) due to the exhaust, which is caused when the in-cylinder pressure rises without being exhausted from the in-cylinder, can be appropriately suppressed. In particular, even when the opening timing of the exhaust valve is retarded to improve the expansion ratio when the engine is running at a low speed, the lift amount of the exhaust valve can be secured and the loss due to exhaust can be suppressed appropriately.

In the present invention, it is preferable that the control unit corrects the timing for controlling the variable valve mechanism so that the exhaust valve is opened as the acquired in-cylinder pressure is higher.
According to the present invention configured as described above, the oil timing can be corrected to a control timing that more appropriately takes into account, and the lift amount of the exhaust valve can be effectively ensured.

In the present invention, preferably, the control means acquires the in-cylinder pressure at the exhaust top dead center as the in-cylinder pressure at a predetermined timing.
According to the present invention thus configured, the control timing of the variable valve mechanism is corrected based on the in-cylinder pressure at the exhaust top dead center, so that the lift amount at the exhaust top dead center of the exhaust valve is reliably ensured. be able to.

In the present invention, it is preferable that the control unit performs variable operation so as to open the exhaust valve based on the acquired magnitude of the in-cylinder pressure so that the lift amount of the exhaust valve at a predetermined timing is equal to or greater than a predetermined amount. The timing for controlling the valve mechanism is corrected.
According to the present invention configured as described above, the control timing of the variable valve mechanism is corrected so that the lift amount of the exhaust valve becomes equal to or greater than a predetermined amount. The loss due to can be effectively suppressed.

In the present invention, preferably, the variable valve mechanism includes a cam that rotates in synchronization with the rotation of the crankshaft, a pressure chamber in which engine oil is filled and the oil pressure of the engine oil is changed by the operation of the cam, and a pressure A hydraulic valve that is connected to the chamber and controls the hydraulic pressure applied to the exhaust valve by opening and closing, and the control means operates when the cam operates to increase the hydraulic pressure in the pressure chamber. Based on the magnitude of the acquired in-cylinder pressure, control is performed to switch the opening and closing of the valve, the hydraulic pressure in the pressure chamber is applied to the exhaust valve to open the exhaust valve, and the control to switch the opening and closing of the hydraulic valve is performed. to correct.
According to the present invention configured as described above, the hydraulic pressure of the engine oil in the pressure chamber is changed using the cam that rotates in synchronization with the rotation of the crankshaft, and the hydraulic pressure in the pressure chamber is changed to the exhaust valve by the control of the hydraulic valve. Since the variable valve mechanism configured to open and operate the exhaust valve is applied, the opening / closing timing of the exhaust valve can be changed with a simple configuration.

  According to the engine control apparatus of the present invention, in an engine in which a hydraulically operated variable valve mechanism is applied to the exhaust valve, the oil state is corrected by appropriately correcting the control timing of the variable valve mechanism based on the in-cylinder pressure. It is possible to cause the exhaust valve to perform a desired operation by the variable valve mechanism without depending on the above.

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. 1 is a schematic side view of an exhaust-side variable valve mechanism that is applied to an exhaust valve of an engine according to an embodiment of the present invention. 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 explanatory drawing of the basic operation | movement of an intake valve and an exhaust valve in the 1st operation area | region by embodiment of this invention. It is explanatory drawing about the characteristic of the exhaust side variable valve mechanism by embodiment of this invention. It is explanatory drawing about the change of the lift amount of an exhaust valve in exhaust top dead center when the valve opening timing of an exhaust valve is retarded by the exhaust side variable valve mechanism. It is explanatory drawing about the case where the lift amount of an exhaust valve becomes small with the state of engine oil. It is explanatory drawing about the problem which arises when the lift amount of an exhaust valve becomes small resulting from the state of engine oil. It is a flowchart which shows the control processing of the exhaust valve by embodiment of this invention.

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

[Engine configuration]
First, the configuration of an engine to which an engine control apparatus according to an embodiment of the present invention is applied will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic configuration diagram of an engine to which an engine control apparatus according to an embodiment of the present invention is applied, and FIG. 2 is an exhaust side variable valve mechanism applied to an exhaust valve in the engine according to the embodiment of the present invention. Fig. 3 is a schematic side view (partially showing a cross-sectional view), and Fig. 3 is a block diagram showing an electrical configuration of an engine control apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the engine 1 is a gasoline engine that is mounted on a vehicle and supplied with 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 provided 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. Each valve 22 is disposed. Further, as shown in FIG. 3, the intake valve 21 has its valve opening timing and / or lift amount changed by the intake side variable valve mechanism 71, and the exhaust valve 22 has the valve opening timing by the exhaust side variable valve mechanism 72. Is changed. The exhaust-side variable valve mechanism 72 is configured by a hydraulically operated mechanism that operates the exhaust valve 22 using the oil pressure of engine oil. In general, two exhaust valves 22 are provided for each cylinder 18, but the exhaust side variable valve mechanism 72 is not limited to both of the two exhaust valves 22, and one of the exhaust valves 22 is not limited. The exhaust side variable valve mechanism 72 may be applied only to the valve 22, and the other valve 22 may be a mechanical valve mechanism having a constant valve opening timing and lift amount. The same applies to the intake valve 21.

  As shown in FIG. 2, an exhaust side variable valve mechanism 72 applied to the exhaust valve 22 includes an oil supply path 72a through which engine oil supplied from the outside passes, and a three-way valve provided on the oil supply path 72a. As a solenoid valve 72b (corresponding to a hydraulic valve) and a pressure chamber 72c filled with engine oil supplied from the oil supply passage 72a via the solenoid valve 72b. In this case, when the solenoid valve 72b is open, the oil supply path 72a and the pressure chamber 72c are in fluid communication, and engine oil is supplied from the oil supply path 72a to the pressure chamber 72c (in FIG. 2). Arrow A11). The solenoid valve 72b is open when not energized and closes when energized. More specifically, the solenoid valve 72b is maintained in a closed state by being energized. Note that a check valve (not shown) is provided on the oil supply path 72a upstream of the solenoid valve 72b.

  The exhaust-side variable valve mechanism 72 swings by a cam 72d provided on the exhaust camshaft 23 to which the rotation of the crankshaft 15 is transmitted via a timing belt or the like, and a force transmitted from the cam 72d. A roller finger follower 72e and a pump unit 72f connected to the pressure chamber 72c and operated by the roller finger follower 72e to increase the pressure (hydraulic pressure) of engine oil in the pressure chamber 72c. In addition, the exhaust side variable valve mechanism 72 is connected to the pressure chamber 72c via the solenoid valve 72b, and operates to open the exhaust valve 22 by the hydraulic pressure in the pressure chamber 72c. And a valve spring 72h for applying a force for maintaining the exhaust valve 22 in a closed state when 72g is not operating. In this case, when the solenoid valve 72b is closed, the fluid communication between the oil supply path 72a and the pressure chamber 72c is interrupted, and the pressure chamber 72c and the brake unit 72g are in fluid communication with each other. The hydraulic pressure in 72c acts on the brake unit 72g (see arrow A12 in FIG. 2).

  An operation in which the exhaust side variable valve mechanism 72 opens the exhaust valve 22 will be specifically described. While the cam 72d rotates in synchronization with the exhaust camshaft 23, when the cam crest (in other words, the cam lobe) formed on the cam 72d contacts the roller finger follower 72e, the cam crest moves the roller finger follower 72e. Push in. Thereby, the roller finger follower 72e urges the pump unit 72f, and the pump unit 72f operates to compress the engine oil in the pressure chamber 72c. At this time, when the solenoid valve 72b is closed, the fluid communication between the oil supply path 72a and the pressure chamber 72c is interrupted, and the pressure chamber 72c and the brake unit 72g are fluidly communicated, so that the pressure chamber 72c and the brake are disconnected. A substantially sealed space is formed by the unit 72g, and the hydraulic pressure of the engine oil in this space is increased by the operation of the pump unit 72f. Then, the brake unit 72g is operated by the increased hydraulic pressure to urge the exhaust valve 22, whereby the exhaust valve 22 is lifted, that is, the exhaust valve 22 is opened. On the other hand, when the solenoid valve 72b is kept open in the above situation, the oil supply passage 72a and the pressure chamber 72c are in fluid communication with each other. The engine oil is pushed out to the oil supply path 72a. (Naturally, when the solenoid valve 72b is closed, the fluid communication between the pressure chamber 72c and the brake unit 72g is cut off, so the hydraulic pressure in the pressure chamber 72c is Does not act on the brake unit 72g).

  Basically, the exhaust valve 22 can be opened by closing the solenoid valve 72b at some timing while the cam crest formed on the cam 72d acts on the roller finger follower 72e. Therefore, the valve opening timing of the exhaust valve 22 can be changed by changing the timing of switching the solenoid valve 72b from the open state to the closed state. In the present embodiment, the cam crest is formed at a predetermined position on the cam 72d so that the exhaust valve 22 can be opened in the exhaust stroke, and the exhaust valve 22 can be opened in the intake stroke in addition to the exhaust stroke. In other words, another cam crest is formed at a predetermined position on the cam 72d so that the exhaust can be opened twice. In the present embodiment, while each of the two cam ridges is acting on the roller finger follower 72e, control for switching the opening and closing of the solenoid valve 72b is performed to change the opening and closing timing of the exhaust valve 22. To do. Further, the exhaust double opening is executed when burnt gas (internal EGR gas) flows backward from the exhaust port 17 to the combustion chamber 19 and is reintroduced.

  Referring to FIG. 1 again, the cylinder head 12 is provided with an injector 67 for direct injection of fuel into the cylinder 18 for each cylinder 18 (direct injection). 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. The fuel supply system 62 is not limited to this configuration.

  An ignition plug 25 for forcibly igniting the air-fuel mixture in the combustion chamber 19 (specifically, spark ignition) 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.

  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 as control means. 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 3, detection signals of various sensors SW1, SW2, SW4 to SW18 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 performs various calculations based on these detection signals to determine the state of the engine 1 and the vehicle, and in response to this, (direct injection) injector 67, spark plug 25, intake side variable valve mechanism 71 Control signals are output to the exhaust side variable valve mechanism 72, the fuel supply system 62, and the actuators of various valves (throttle valve 36, EGR valve 511). Thus, the PCM 10 operates the engine 1. In particular, in this embodiment, the PCM 10 outputs a control signal to the solenoid valve 72b of the exhaust side variable valve mechanism 72 (specifically, supplies a voltage or current to the solenoid valve 72b), and the solenoid valve 72b. The control for changing the opening / closing timing of the exhaust valve 22 is executed by switching between opening and closing.

[Operation area]
Next, with reference to FIG. 4, an operation region of the engine 1 according to the embodiment of the present invention will be described. FIG. 4 shows an example of the operation control map of the engine 1. For the purpose of improving fuel consumption and exhaust emission performance, the engine 1 does not perform ignition by the spark plug 25 in the first operating region R11, which is a low load region where the engine load is relatively low. Performs compression ignition combustion by ignition. However, as the load on the engine 1 increases, in this compression ignition combustion, the combustion becomes too steep and combustion noise is generated, and it becomes difficult to control the ignition timing (prone to misfire and the like). It is in). Therefore, in this engine 1, in the second operating region R12, which is a high load region where the engine load is relatively high, forced ignition combustion (here, spark ignition combustion) using the spark plug 25 is used instead of compression ignition combustion. To do. As described above, the engine 1 performs a CI (Compression Ignition) operation for performing an operation by compression ignition combustion and an SI (for performing an operation by spark ignition combustion) according to the operation state of the engine 1, particularly, the load of the engine 1. It is configured to switch between (Spark Ignition) driving.

  Here, with reference to FIG. 5, the basic operation of the intake valve 21 and the exhaust valve 22 in the first operation region R11 in which the CI operation is performed will be described. FIG. 5 shows the crank angle on the horizontal axis and the lift amount of the valve on the vertical axis. A solid line graph G11 shows the operation (lift curve) of the exhaust valve 22 according to the crank angle, and a broken line graph G12 shows the operation (lift curve) of the intake valve 21 according to the crank angle. As shown in the graph G11, in the first operation region R11 in which the CI operation is performed, the exhaust side variable valve mechanism 72 opens the exhaust valve 22 during the exhaust stroke and also opens the exhaust valve during the intake stroke. Opening is performed to introduce the internal EGR gas having a relatively high temperature into the cylinder 18. By doing so, during the CI operation, the compression end temperature in the cylinder 18 is increased to improve the ignitability and stability of the compression ignition combustion.

[Control for exhaust valve]
Next, the control content for the exhaust valve according to the embodiment of the present invention will be specifically described.

  First, the characteristics of the exhaust-side variable valve mechanism 72 that operates the exhaust valve 22 will be described with reference to FIG. Here, in order to simplify the explanation, an example will be given in which the exhaust valve 22 is opened only once by the exhaust-side variable valve mechanism 72 (actually, the exhaust valve 22 opens twice).

  6A shows the operation (lift curve) of the exhaust valve 22 when the exhaust valve 22 is opened at a relatively early timing t11 by the exhaust side variable valve mechanism 72. 6 (a) shows the open / closed state of the solenoid valve 72b of the exhaust side variable valve mechanism 72 when the exhaust valve 22 is operated in this way. For example, the valve opening timing t11 is referred to as the valve opening timing when the valve opening timing of the exhaust valve 22 is advanced to the maximum by the exhaust-side variable valve mechanism 72 (hereinafter referred to as “maximum valve opening timing” as appropriate). ). On the other hand, on the upper side of FIG. 6B, the exhaust is performed at a relatively late timing t12, specifically, at the timing t12 delayed from the valve opening timing t11 shown in FIG. 6A (see arrow A21). The operation (lift curve) of the exhaust valve 22 when the exhaust valve 22 is opened by the side variable valve mechanism 72 is shown. In FIG. 6B, the exhaust valve 22 is operated in this way. The open / close state of the solenoid valve 72b of the exhaust side variable valve mechanism 72 at the time is shown. Further, on the upper part of FIG. 6B, the lift curve shown in the upper part of FIG.

  Comparing FIG. 6 (a) and FIG. 6 (b), it can be seen that if the valve opening timing of the exhaust valve 22 is retarded, the lift amount of the exhaust valve 22 becomes smaller (see arrow A22). Further, the lift amount integrated value of the exhaust valve 22 corresponding to the area indicated by the symbol Ar2 (the value obtained by integrating the lift amount of the exhaust valve 22 that changes according to the crank angle during the valve opening period, and passes through the exhaust valve 22). The amount of flowing gas is approximately the amount corresponding to the integral value of the lift amount at high revolutions, and the pump loss generally increases as the integral amount of lift decreases with respect to the same passing gas amount at low revolutions). It can be seen that the lift amount integrated value of the exhaust valve 22 corresponding to the area is smaller. The reason why the lift amount and the lift amount integral value become smaller when the opening timing of the exhaust valve 22 is retarded in this way is as follows.

  As described above, in the exhaust side variable valve mechanism 72, when the cam crest formed on the cam 72d is in contact with the roller finger follower 72e, the cam crest pushes the roller finger follower 72e, thereby The unit 72f operates to compress the engine oil in the pressure chamber 72c. At this time, when the solenoid valve 72b is closed, a substantially sealed space is formed by the pressure chamber 72c and the brake unit 72g, and the hydraulic pressure of the engine oil in this space is increased, and the brake pressure is increased by the brake unit 72g. Operates to urge the exhaust valve 22 to open the exhaust valve 22.

Here, the hydraulic pressure in the pressure chamber 72c increases when the cam crest of the cam 72d starts to act on the roller finger follower 72e, but decreases after increasing to some extent. Therefore, when the solenoid valve 72b is closed at an initial predetermined timing when the cam crest of the cam 72d starts to act on the roller finger follower 72e, the pressure of the high pressure chamber increases from a relatively early time. The valve opening speeds up, and the lift amount and the integral value of the lift amount are the largest since the valve unit is lifted in accordance with the movement of the pump unit 72f pushed by the cam crest (see FIG. 6A). In this case, the valve opening timing of the exhaust valve 22 that maximizes the lift amount and the lift amount integral value of the exhaust valve 22 is defined as the maximum advance valve opening timing of the exhaust valve 22. On the other hand, if the valve closing timing of the solenoid valve 72b is retarded from such maximum advance valve opening timing, the pressure increase in the high pressure chamber becomes relatively slow and the opening of the exhaust valve 22 becomes slow. Then, the lift amount and the lift amount integrated value that are lifted in accordance with the movement of the pump unit that is pushed in by the cam crest thereafter are also reduced (see FIG. 6B).
As described above, the exhaust-side variable valve mechanism 72 can change the opening / closing timing of the exhaust valve 22, but as shown in FIG. 6, the exhaust-side variable valve mechanism 72 opens and closes the exhaust valve 22. When the timing is changed, the lift amount of the exhaust valve 22 also changes. Therefore, it can be said that the exhaust side variable valve mechanism 72 can change the lift amount in addition to the opening / closing timing of the exhaust valve 22.

  By the way, when the engine 1 is rotating at a high speed, if the valve opening timing of the exhaust valve 22 is advanced with respect to the exhaust bottom dead center (TDC) by the exhaust side variable valve mechanism 72, the exhaust can be quickly discharged from the cylinder. It is considered that the pumping loss can be reduced. For example, if the valve opening timing of the exhaust valve 22 is set to the maximum advance valve opening timing, the pumping loss can be effectively reduced. On the other hand, it is considered that the expansion ratio can be improved by retarding the valve opening timing of the exhaust valve 22 to the vicinity of the exhaust bottom dead center by the exhaust side variable valve mechanism 72 when the engine 1 is rotating at a low speed.

  Therefore, in this embodiment, the PCM 10 changes the valve opening timing of the exhaust valve 22 by the exhaust-side variable valve mechanism 72 according to the engine speed. Specifically, from the viewpoint of pumping loss, the PCM 10 advances the valve opening timing of the exhaust valve 22 by the exhaust side variable valve mechanism 72 as the engine speed increases (more specifically, the maximum valve opening timing is set). The opening timing of the exhaust valve 22 is advanced as a limit.) From the viewpoint of the expansion ratio, the opening timing of the exhaust valve 22 is retarded by the exhaust side variable valve mechanism 72 as the engine speed is lower.

  However, due to the characteristics of the exhaust side variable valve mechanism 72 as described above (see FIG. 6), if the valve opening timing of the exhaust valve 22 is retarded too much in order to improve the expansion ratio when the engine 1 is rotating at low speed, it is desirable. The lift amount cannot be secured, and the exhaust cannot be discharged smoothly from the cylinder. In particular, if the opening timing of the exhaust valve 22 is retarded too much, the lift amount of the exhaust valve 22 at the exhaust top dead center becomes considerably small, and loss due to exhaust (pumping loss) occurs. This will be specifically described with reference to FIG.

  FIG. 7 is an explanatory view of a change in the lift amount of the exhaust valve 22 at the exhaust top dead center when the valve opening timing of the exhaust valve 22 is retarded by the exhaust side variable valve mechanism 72. In FIG. 7, the horizontal axis indicates the crank angle, and the vertical axis indicates the lift amount of the exhaust valve 22. The graphs G21 to G24 basically operate the exhaust valve 22 to open the exhaust twice (see FIG. 5), and retard the valve opening timing of the exhaust valve 22 in the exhaust stroke at that time. A specific example of the lift curve of the exhaust valve 22 is shown.

  As shown in FIG. 7, it can be seen that if the degree of retarding the opening timing of the exhaust valve 22 is increased (see arrow A31), the lift amount of the exhaust valve 22 at the exhaust top dead center is decreased (arrow). A32). In particular, as shown in the graph G24, when the degree of delay of the opening timing of the exhaust valve 22 is considerably increased, the lift amount of the exhaust valve 22 at the exhaust top dead center becomes 0, that is, at the exhaust top dead center. It can be seen that the exhaust valve 22 is fully closed. Thus, if the lift amount of the exhaust valve 22 at the exhaust top dead center is not ensured by retarding the valve opening timing of the exhaust valve 22, the exhaust pressure is not properly discharged from the cylinder and the in-cylinder pressure increases. However, loss due to exhaust occurs.

  Accordingly, in the present embodiment, the valve opening timing of the exhaust valve 22 in the exhaust stroke is retarded to the maximum by the exhaust side variable valve mechanism 72 so that the lift amount of the exhaust valve 22 at the exhaust top dead center is ensured. A maximum retarded valve opening timing is set, and the exhaust-side variable valve mechanism 72 is controlled so that the exhaust valve 22 is opened at a timing more advanced than the maximum retarded valve opening timing. Specifically, the PCM 10 lifts the exhaust valve 22 at the exhaust top dead center by retarding the valve opening timing of the exhaust valve 22 up to the maximum retarded valve opening timing when the engine speed is low. The expansion ratio is improved while securing the amount and suppressing loss due to exhaust.

  By the way, as described above, if the opening timing of the exhaust valve 22 is retarded too much, the lift amount of the exhaust valve 22 at the exhaust top dead center cannot be ensured. However, the lift amount of the exhaust valve 22 is to cope with this problem. Even when the valve opening timing is set such that the exhaust valve 22 is secured, the lift amount of the exhaust valve 22 may not be properly secured depending on the state of the engine oil used by the exhaust side variable valve mechanism 72, that is, the exhaust valve. 22 may not perform the desired operation. This will be specifically described with reference to FIG.

  FIG. 8 is an explanatory diagram for a case where the lift amount of the exhaust valve 22 becomes small depending on the state of the engine oil. FIG. 8 shows the crank angle on the horizontal axis and the lift amount of the exhaust valve 22 on the vertical axis. The graphs G31 and G32 basically operate the exhaust valve 22 so as to open the exhaust twice (see FIG. 5), and the opening timing of the exhaust valve 22 in the exhaust stroke at that time is the same. The lift curve of the exhaust valve 22 in the case of setting to is shown. More specifically, the broken line graph G32 shows the lift curve of the exhaust valve 22 when the viscosity of the engine oil used by the exhaust side variable valve mechanism 72 is higher than that of the solid line graph G31. Comparing the graph G31 and the graph G32, when the viscosity of the engine oil is high, the lift amount of the exhaust valve 22 is reduced as a whole even if the opening timing of the exhaust valve 22 is set to be the same. . In particular, it can be seen that the lift amount of the exhaust valve 22 at the exhaust top dead center is considerably small (see arrow A4). This is because if the viscosity of the engine oil is high, the exhaust side variable valve mechanism 72 cannot obtain the hydraulic pressure required to cause the exhaust valve 22 to perform a desired operation. This is because the hydraulic pressure in the pressure chamber 72c of the mechanism 72 does not rise to an appropriate pressure. The viscosity of the engine oil varies depending on the temperature and dilution rate of the engine oil, the air mixing rate, the degree of deterioration, and the like.

  Next, referring to FIG. 9, a problem that occurs when the lift amount of the exhaust valve 22 is reduced due to the state of the engine oil (for example, when the lift curve is as shown in the graph G <b> 32 of FIG. 8). The point will be described. FIG. 9 shows the in-cylinder volume on the horizontal axis and the in-cylinder pressure on the vertical axis, and shows the relationship between the in-cylinder volume and the in-cylinder pressure in each step (intake stroke, compression stroke, combustion stroke, exhaust stroke). (P-V diagram). As described above, when the lift amount of the exhaust valve 22 is reduced due to the state of the engine oil, particularly when the lift amount of the exhaust valve 22 at the exhaust top dead center is considerably reduced, the exhaust gas is discharged from the cylinder. Without being properly discharged, the in-cylinder pressure rises in the latter half of the exhaust stroke, that is, immediately before the intake stroke, as indicated by arrow A5 in FIG. 9 (see the broken line). In this case, loss due to exhaust (pumping loss) occurs.

  Therefore, in this embodiment, the PCM 10 acquires the in-cylinder pressure at the exhaust top dead center from the in-cylinder pressure sensor SW6, and based on the magnitude of this in-cylinder pressure, opens the exhaust valve 22 so as to open the exhaust valve 22. The timing for controlling the mechanism 72 is corrected. Specifically, the timing for performing the control for switching the solenoid valve 72b of the exhaust side variable valve mechanism 72 from open to closed is corrected. In this case, the PCM 10 corrects the control timing for the solenoid valve 72b earlier as the in-cylinder pressure at the exhaust top dead center is higher, and advances the valve opening timing of the exhaust valve 22 so as to advance the exhaust top dead center. The lift amount of the exhaust valve 22 at the point is secured to a predetermined amount or more. This utilizes the characteristic of the exhaust side variable valve mechanism 72 that the lift amount and the lift amount integral value of the exhaust valve 22 increase as the valve opening timing of the exhaust valve 22 is advanced (FIG. 6 and FIG. 6). 7).

  Next, a method for controlling the exhaust valve 22 according to the embodiment of the present invention will be specifically described with reference to FIG. FIG. 10 is a flowchart showing a control process of the exhaust valve 22 according to the embodiment of the present invention. This flow is executed while the exhaust valve 22 is opened in the exhaust stroke. The flow is repeatedly executed by the PCM 10.

  First, in step S1, the PCM 10 determines whether or not the piston 14 of the cylinder 18 has reached exhaust top dead center based on the crank angle detected by the crank angle sensor SW12. When it is determined that the piston 14 has reached exhaust top dead center (step S1: Yes), the process proceeds to step S2, and the PCM 10 acquires the in-cylinder pressure detected by the in-cylinder pressure sensor SW6, and proceeds to step S3. On the other hand, when it is not determined that the piston 14 has reached exhaust top dead center (step S1: No), the process returns to step S1, and the PCM 10 performs the determination in step S1 until the piston 14 reaches exhaust top dead center. repeat.

  In step S3, the PCM 10 determines whether or not the in-cylinder pressure acquired in step S2 is a predetermined value or more. Here, it is determined whether or not an increase in the in-cylinder pressure has occurred due to a reduction in the lift amount of the exhaust valve 22 without obtaining sufficient hydraulic pressure in the exhaust-side variable valve mechanism 72. For example, a value corresponding to the operating state of the engine 1 is applied to the predetermined value used in the determination in step S3. If it is determined that the in-cylinder pressure is greater than or equal to the predetermined value (step S3: Yes), the process proceeds to step S4. If it is not determined that the in-cylinder pressure is greater than or equal to the predetermined value (step S3: No), the process ends. .

  In step S4, the PCM 10 controls the exhaust side variable valve mechanism 72 to open the exhaust valve 22 according to the in-cylinder pressure acquired in step S2, that is, the solenoid valve of the exhaust side variable valve mechanism 72. The timing for performing control for switching 72b from open to closed (corresponding to the timing for energizing the solenoid valve 72b) is corrected. Specifically, the PCM 10 corrects the control timing of the solenoid valve 72b earlier as the amount of in-cylinder pressure that exceeds the predetermined value in step S3 is larger. Further, the PCM 10 corrects the control timing of the solenoid valve 72b so that the lift amount of the exhaust valve 22 at the exhaust top dead center is equal to or greater than a predetermined amount. This is equivalent to correcting the control timing of the solenoid valve 72b so that the cylinder pressure at the exhaust top dead center is less than a predetermined value. Accordingly, the predetermined amount used in this case is set based on, for example, an amount that is at least larger than the lift amount of the exhaust valve 22 that causes a loss that cannot be overlooked (pumping loss), in other words, a loss within an allowable range ( It is set based on the lift amount of the exhaust valve 22 that causes a pumping loss). After step S4, the PCM 10 applies the control timing of the solenoid valve 72b corrected in this way when the exhaust valve 22 is opened in the next exhaust stroke.

  For example, when the engine speed is higher, the PCM 10 advances the valve opening timing of the exhaust valve 22, and when the engine speed is lower, the PCM 10 delays the valve opening timing of the exhaust valve 22 according to the engine speed. Thus, when the opening timing of the exhaust valve 22 is advanced or retarded, the control timing of the solenoid valve 72b corrected according to the in-cylinder pressure as described above may be applied. The PCM 10 also corrects the maximum retarded valve opening timing of the exhaust valve 22 based on the in-cylinder pressure in accordance with the correction of the control timing of the solenoid valve 72b in accordance with the in-cylinder pressure at the exhaust top dead center, thereby rotating the engine. When the number is low, the valve opening timing of the exhaust valve 22 may be retarded up to the corrected maximum retardation valve opening timing.

[Function and effect]
Next, operational effects of the engine control apparatus according to the embodiment of the present invention will be described.

  According to the present embodiment, the timing for controlling the exhaust-side variable valve mechanism 72 to correct the exhaust valve 22 is corrected based on the magnitude of the in-cylinder pressure indicating the state (viscosity or the like) of the engine oil. The exhaust-side variable valve mechanism 72 can be controlled to open the exhaust valve 22 at a timing that appropriately takes into account the state of the engine oil. Therefore, it is possible to cause the exhaust valve 22 to perform a desired operation by the exhaust side variable valve mechanism 72 regardless of the state of the engine oil, in other words, it is possible to realize a desired cam profile. That is, the lift amount during the valve opening period of the exhaust valve 22 can be ensured appropriately. Thereby, the loss (pumping loss) due to the exhaust, which is caused when the in-cylinder pressure rises without being exhausted from the in-cylinder, can be appropriately suppressed. In particular, even when the opening timing of the exhaust valve 22 is retarded in order to improve the expansion ratio when the engine 1 is running at a low speed, the lift amount of the exhaust valve 22 is secured and the loss due to exhaust is appropriately suppressed. be able to.

  Further, according to the present embodiment, the higher the acquired in-cylinder pressure is, the faster the timing for controlling the exhaust-side variable valve mechanism 72 to open the exhaust valve 22 is corrected. The control timing can be corrected more appropriately and the lift amount of the exhaust valve 22 can be effectively ensured.

  Further, according to the present embodiment, the control timing of the exhaust side variable valve mechanism 72 is corrected based on the in-cylinder pressure at the exhaust top dead center, so that the lift amount at the exhaust top dead center of the exhaust valve 22 is ensured. Can be secured.

  Further, according to the present embodiment, the control timing of the exhaust side variable valve mechanism 72 is corrected so that the lift amount of the exhaust valve 22 is equal to or greater than a predetermined amount, so that the lift amount of the exhaust valve 22 is ensured, Loss due to exhaust can be effectively suppressed.

[Modification]
In the above-described embodiment, the timing for controlling the exhaust side variable valve mechanism 72 to open the exhaust valve 22 is corrected based on the in-cylinder pressure at the exhaust top dead center, but the in-cylinder pressure at this timing is corrected. However, the in-cylinder pressure at a predetermined timing during the valve opening period of the exhaust valve 22 by the exhaust side variable valve mechanism 72 may be used. However, it is preferable to use the in-cylinder pressure at the exhaust top dead center, but not strictly limited to using the in-cylinder pressure at the exhaust top dead center. The in-cylinder pressure near the exhaust top dead center is used. May be.

  In the above-described embodiment, the timing for controlling the exhaust-side variable valve mechanism 72 is corrected so as to open the exhaust valve 22 based only on the in-cylinder pressure indirectly indicating the state (viscosity or the like) of the engine oil. However, in another example, not only the in-cylinder pressure but also the oil pressure detected by the oil pressure sensor SW17 and / or the oil temperature detected by the oil temperature sensor SW18, which directly indicates the state of the engine oil, are used to control the exhaust valve 22. You may correct | amend the timing which controls the exhaust side variable valve mechanism 72 so that it may open.

  In the above-described embodiment, an example in which the present invention is applied to a gasoline engine that is operated by switching between CI operation and SI operation has been described, but application of the present invention is not limited to this. The present invention is also applicable to a normal gasoline engine (that is, an engine that executes only SI operation) and a diesel engine.

1 engine 10 PCM
18 cylinder 21 intake valve 22 exhaust valve 25 spark plug 67 injector 71 intake side variable valve mechanism 72 exhaust side variable valve mechanism 72b solenoid valve 72c pressure chamber 72d cam

Claims (5)

An engine control device including a cylinder provided with an intake valve for introducing intake air into a cylinder and an exhaust valve for discharging exhaust gas from the cylinder,
A hydraulically operated variable valve mechanism configured to operate the exhaust valve using hydraulic pressure, and to change the opening and closing timing of the exhaust valve;
Control means for controlling the variable valve mechanism so as to change the opening and closing timing of the exhaust valve;
Have
The variable valve mechanism is configured such that the lift amount decreases when the opening timing of the exhaust valve is retarded from a predetermined reference timing,
The control means obtains an in- cylinder pressure near the exhaust top dead center as an in-cylinder pressure at a predetermined timing during a valve opening period of the exhaust valve by the variable valve mechanism, and the higher the in-cylinder pressure, the more the exhaust valve A control apparatus for an engine, wherein the timing for controlling the variable valve mechanism is corrected so that the valve opening timing is advanced.   2. The engine control device according to claim 1, wherein the control unit performs a correction for earlier timing of controlling the variable valve mechanism so that the exhaust valve is opened as the acquired in-cylinder pressure is higher.   The engine control device according to claim 1 or 2, wherein the control means acquires an in-cylinder pressure at an exhaust top dead center as the in-cylinder pressure at the predetermined timing.   The control means is configured to open the exhaust valve based on the acquired magnitude of the in-cylinder pressure so that a lift amount of the exhaust valve at the predetermined timing is equal to or greater than a predetermined amount. The engine control apparatus according to any one of claims 1 to 3, wherein timing for controlling the mechanism is corrected. The variable valve mechanism is
A cam that rotates in synchronization with the rotation of the crankshaft;
A pressure chamber in which engine oil is filled and the oil pressure of the engine oil is changed by the operation of the cam;
A hydraulic valve that is connected to the pressure chamber and controls the hydraulic pressure applied to the exhaust valve by opening and closing;
Have
The control means performs control for switching opening and closing of the hydraulic valve when the cam is operating to increase the hydraulic pressure in the pressure chamber, and causes the hydraulic pressure in the pressure chamber to act on the exhaust valve to perform the control. The engine control according to any one of claims 1 to 4, wherein a timing for performing control to open and close the hydraulic valve to open and close the hydraulic valve is corrected based on the acquired magnitude of the in-cylinder pressure. apparatus.

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