JP6666222B2 - Variable valve operating device and controller of variable valve operating device - Google Patents

Description

  The present invention relates to a variable valve operating device for an internal combustion engine and a controller for the variable valve operating device, and more particularly to a variable valve operating device for an internal combustion engine having a function of automatically stopping and starting the internal combustion engine and a controller for the variable valve operating device. It is about.

  In order to reduce the fuel consumption of the internal combustion engine and the emission of harmful exhaust gas components, control for automatically stopping and starting the internal combustion engine regardless of the driver's intention has been put to practical use. For example, when an automobile temporarily stops at an intersection or the like during driving, so-called idle stop control is performed, in which the internal combustion engine is automatically stopped, and the internal combustion engine is automatically started before traveling starts. Also, in a hybrid vehicle having both an electric motor and an internal combustion engine as power, control is performed to automatically stop and start the internal combustion engine even during traveling according to the traveling mode.

  In an automobile that automatically stops and starts the internal combustion engine without depending on the driver's intention, vibrations and noises at the time of automatic start are likely to cause discomfort to the driver, and the internal combustion engine is started quickly and smoothly. Technology is becoming important. As a technique for smoothly starting the rotation of a crankshaft of an internal combustion engine at the time of automatic start, for example, a technique disclosed in Japanese Patent Application Laid-Open No. 2005-337110 (Patent Document 1) is known.

  In Patent Literature 1, in an internal combustion engine including a variable valve timing mechanism capable of adjusting a timing at which an exhaust valve is opened and closed, and a control unit for controlling the variable valve timing mechanism, when the internal combustion engine starts, an air-fuel mixture is first provided. It has been proposed to perform control for delaying the opening timing of the exhaust valve of the first explosive cylinder which is stopped after the combustion of the first explosive cylinder burning.

  By delaying the opening timing of the exhaust valve, it is possible to prevent the combustion pressure from being released early by opening the exhaust valve during the expansion stroke, and to efficiently take out the combustion pressure of the first explosive cylinder to the crankshaft as power. Can be done. Therefore, the internal combustion engine can be started quickly.

JP 2005-337110 A

  By the way, the gas pressure (combustion pressure) in the cylinder bore changes from a positive peak pressure to a negative pressure due to the lowering of the piston of the first explosive cylinder, but in the positive pressure range, the gas pressure acts to push down the piston. In the negative pressure range, the gas pressure acts to raise the piston. Therefore, it is important that the opening timing of the exhaust valve be set near the pressure (atmospheric pressure) at which the gas pressure switches from a positive pressure to a negative pressure.

  However, this gas pressure change characteristic differs depending on the initial piston position of the first explosive cylinder, and when the opening timing of the exhaust valve is earlier than the crank angle at which the atmospheric pressure is reached, a positive gas pressure is generated. Since the exhaust valve is opened in a state in which the exhaust gas is opened, the precious gas pressure escapes to the exhaust port side, and energy for pushing down the piston is wasted. On the other hand, if the opening timing of the exhaust valve is later than the crank angle at which the atmospheric pressure is reached, the pressure becomes negative before reaching the opening timing of the exhaust valve, thereby damping the lowering operation of the piston. Will be. Therefore, there is a problem that the startability of the internal combustion engine is hindered.

  Therefore, when automatically starting the internal combustion engine, it is necessary to effectively use the gas pressure in the cylinder bore. For this purpose, it is important to open the exhaust valve when the gas pressure is near atmospheric pressure. It is.

  Note that Patent Document 1 does not consider controlling the opening timing of the exhaust valve of the first explosive cylinder in accordance with the initial piston position at the start of the start, and when the initial piston position is different, There is a possibility that sufficient startability has not been obtained.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a novel variable valve device for an internal combustion engine and a controller for the variable valve device that can improve the startability of the internal combustion engine by effectively utilizing the gas pressure generated by combustion of the first explosion cylinder. It is in.

  The feature of the present invention is that an exhaust-side variable valve mechanism that adjusts the valve timing of an exhaust valve and an intake-side variable valve mechanism that adjusts the valve timing of an intake valve are provided in an internal combustion engine having an intake valve and an exhaust valve. In the variable valve actuating device provided with the exhaust valve, the exhaust-side variable valve mechanism is configured to inject a fuel into a cylinder in an expansion stroke at the time of starting the internal combustion engine to perform combustion first, and the first exhaust valve that opens after combustion of an initial explosion cylinder. Is adjusted based on at least information on the initial piston position of the first explosive cylinder.

  According to the present invention, even when the initial piston position of the first explosion cylinder is different, the gas pressure (combustion energy) of the first explosion cylinder can be effectively applied to the piston, and as a result, a good startability can be obtained. What you can get.

1 is a configuration diagram illustrating a configuration of a variable valve system of an internal combustion engine to which the present invention is applied. It is explanatory drawing explaining the gas pressure in an in-cylinder combustion chamber in an independent combustion process, the in-cylinder combustion chamber volume, and the state of in-cylinder combustion chamber gas. FIG. 4 is a characteristic diagram illustrating a pressure change in a combustion chamber in a cylinder during self-sustaining combustion. FIG. 5 is an explanatory diagram illustrating characteristics of an opening timing of an exhaust valve when an initial crank angle corresponding to an initial piston position is 70 ° in the first embodiment of the present invention. FIG. 4 is an explanatory diagram illustrating characteristics of an opening timing of an exhaust valve when an initial crank angle corresponding to an initial piston position is 90 ° in the first embodiment of the present invention. FIG. 4 is an explanatory diagram illustrating characteristics of an opening timing of an exhaust valve when an initial crank angle corresponding to an initial piston position is 110 ° in the first embodiment of the present invention. FIG. 7 is a characteristic diagram illustrating a gas pressure change in an in-cylinder combustion chamber during self-sustained combustion at the initial crank angle shown in FIGS. 4 to 6. 4 is a control flowchart illustrating control during automatic stop according to the first embodiment of the present invention. FIG. 4 is a control flowchart illustrating control at the time of automatic start according to the first embodiment of the present invention. FIG. 4 is an explanatory diagram illustrating the opening timing of an exhaust valve for self-sustained combustion and normal combustion during startup. FIG. 5 is an explanatory diagram illustrating characteristics of an opening timing of an exhaust valve when a transition is made from independent combustion to normal combustion. FIG. 11 is a characteristic diagram illustrating characteristics of an exhaust VEL used in the second embodiment of the present invention. FIG. 11 is an explanatory diagram illustrating characteristics of an opening timing of an exhaust valve when an initial crank angle corresponding to an initial piston position is 90 ° in the second embodiment of the present invention. FIG. 9 is an explanatory diagram illustrating characteristics of an opening timing of an exhaust valve when an initial crank angle corresponding to an initial piston position is 70 ° in the second embodiment of the present invention. FIG. 11 is an explanatory diagram illustrating characteristics of an opening timing of an exhaust valve when an initial crank angle corresponding to an initial piston position is 50 ° in the second embodiment of the present invention.

  Embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the following embodiments, and various modifications and application examples are included in the technical concept of the present invention. It is included in the range.

  Next, a variable valve operating device for an internal combustion engine and a controller of the variable valve operating device according to the first embodiment of the present invention will be described.

  In the present embodiment, the present invention is applied to a so-called four-cycle four-cylinder internal combustion engine of spark ignition gasoline specification, and is applied to an idling stop vehicle that automatically stops and starts the internal combustion engine regardless of the start operation of the driver. And a controller of the variable valve device.

  In this internal combustion engine, as shown in FIG. 1, a combustion chamber 04 is formed between a cylinder block 01 and a cylinder head 02 via a piston 03, and a spark plug 05 is provided at a substantially central position of the cylinder head 02. Is provided. The cylinder block 01, the cylinder head 02, the piston 03, and the like may be collectively referred to as a "cylinder".

  The piston 03 is connected to a crankshaft 07 via a connecting rod 06 having one end connected to a piston pin (not shown), and the crankshaft 07 is driven by a drive motor 09 via a pinion gear mechanism 08. It can be started. The drive motor 09 can also be used as crank position control means for controlling the crank angle (crank position) when the engine is stopped and the sliding position of the piston 03. The crankshaft 07 is configured so that a crank angle and a rotation speed are detected by a crank angle sensor 010 described later.

  The cylinder block 01 is provided with a water temperature sensor 011 for detecting a water temperature in the water jacket, and the cylinder head 02 is provided with a fuel injection valve 012 for injecting fuel into the combustion chamber 04. Further, two intake valves 4 and two exhaust valves 5 are provided for each cylinder for opening and closing an intake port 013 and an exhaust port 014 formed inside the cylinder head 02, respectively. A variable valve operating device is provided on the exhaust valve 5 side.

  The variable valve apparatus controls an exhaust VEL1, which is a first variable valve mechanism that controls a valve lift and an operating angle (open period) of an exhaust valve 5 of the internal combustion engine, and controls an opening / closing timing (valve timing) of the exhaust valve 5. An exhaust VTC 2 as a second variable valve mechanism and an intake VTC 3 as a third variable valve mechanism for controlling the opening / closing timing (valve timing) of the intake valve 4 are provided. The operations of the exhaust VEL1, the exhaust VTC2, and the intake VTC3 are controlled by a controller 22, which will be described later, according to the engine operating state.

  The controller 22 includes a microcomputer, a peripheral drive circuit, and the like, and has a function of detecting a parameter representing an operation state of the internal combustion engine, executing a predetermined calculation using the parameter, and adjusting a control amount of the internal combustion engine. I have. The microcomputer includes an input unit for detecting a parameter, a central processing unit for executing an operation, and an output unit for outputting a control amount obtained by the operation. The control amount from the output unit is sent to the peripheral drive circuit, and is given to the exhaust VEL1, the exhaust VTC2, and the intake VTC3 as a control drive signal.

  The detailed configurations of the exhaust VEL1, the exhaust VTC2, and the intake VTC3 are not so related to the present invention, and therefore, detailed description is omitted. Here, details of the exhaust VEL1 are the same as those described in, for example, Japanese Patent Application Laid-Open No. 2012-36864 filed by the present applicant.

  This exhaust VEL1 is not used in the first embodiment, but is used in the second embodiment. Therefore, in Example 1, the operating angle and the lift of the exhaust valve 5 are constant, and in the present embodiment, the minimum lift and the minimum operating angle are set. Of course, in the present embodiment, the exhaust VTC1 may not be used, and only the exhaust VTC2 may be used.

  The exhaust VTC2 and the intake VTC3 are electrically operated valve timing control devices, and have the same configuration as that described in, for example, Japanese Patent Application Laid-Open No. 2014-169630 filed by the present applicant. Here, the camshaft tends to stabilize near the most retarded angle due to the valve spring reaction force, and the response of the advance conversion of the opening timing of the exhaust valve at the start of startup tends to be poor (particularly at the start of startup or when the engine is stopped Time).

  Therefore, the exhaust VTC2 is provided with an advance side biasing spring, which is urged toward the advance side, so that the advancing angle conversion responsiveness which is concerned is increased, and as described later, a favorable Startup by independent combustion can be realized without delay.

  Next, the operating state of the piston by the self-sustaining combustion, the gas state of the cylinder bore, and the state of the gas pressure will be described. In the following, for example, a description will be given of a change in the above-described state when the vehicle is started independently after an idle stop. Here, the self-sustained combustion means that a compression operation is not performed by using an external drive motor such as a starter motor, but fuel is injected into a cylinder in an expansion stroke and burned, and the combustion is started by the combustion energy of the air-fuel mixture. Means that.

  FIG. 2 shows a state in which combustion is performed from the time of fuel injection of the first explosive cylinder in the expansion stroke, and the piston descends to reach the bottom dead center (BDC). FIG. 3 shows the piston position in the cylinder bore and the gas pressure. Shows the change. In the following, for convenience of explanation, a space formed by the piston crown surface, the cylinder, and the cylinder head is referred to as “in-cylinder combustion chamber”.

  The state shown in FIG. 2A shows an initial piston position of a cylinder (first explosion cylinder) in an expansion stroke when the internal combustion engine is stopped by idling stop. At this time, the initial piston position is slightly closer to the top dead center (TDC), and is about 70 ° from the top dead center (TDC) in terms of crank angle.

  Then, the cylinder in the expansion stroke at the time of idling stop becomes the first explosion cylinder, and the initial piston position of this first explosion cylinder changes every time the idling stop is performed. Immediately after the idle stop, air immediately flows from between the piston and the cylinder bore, and the inside of the in-cylinder combustion chamber is almost at atmospheric pressure. In this state, in the in-cylinder combustion chamber, the in-cylinder combustion chamber pressure is atmospheric pressure, the in-cylinder combustion chamber volume is Vs, and the in-cylinder combustion chamber gas is air. Here, when the depression of the brake pedal is released or the accelerator pedal is depressed and there is a request for independent start, the crank angle (for example, 70 °) in the state shown in (A) is set as the initial crank angle (θPi). It will shift to the sequence for independent startup.

  First, as shown in FIG. 2B, fuel corresponding to the amount of air existing in the in-cylinder combustion chamber volume Vs determined by the initial piston position is directly injected into the in-cylinder combustion chamber. That is, the fuel is injected from the fuel injection valve so as to have the stoichiometric air-fuel ratio. In this state, in the in-cylinder combustion chamber, the in-cylinder combustion chamber pressure is atmospheric pressure, the in-cylinder combustion chamber volume is Vs, and the in-cylinder combustion chamber gas is a mixture of air and fuel.

Here, the in-cylinder combustion chamber volume Vs at the initial piston position is obtained by the following equation.
Vs = V0 + A × χs (1)
V0 is the in-cylinder combustion chamber volume when the piston has reached compression top dead center (TDC), A is the bore area, and χs is the piston descent length from compression top dead center (TDC).

Further, the piston descent length χs is obtained by the following equation.
χs = R × (1-cos θPi) + λ × R × (1-√ (Ys)) (2)
Here, “R” is the radius of rotation of the crankpin shown in FIG. 1, “L” is the distance between the axes of the connecting rod shown in FIG. 1, “λ” is L / R, and “Ys” is 1− (sin ² is a need in the θP1) / λ ^2. That is, the initial crank angle (θPi) determined by the initial piston position is detected, and the in-cylinder combustion chamber volume Vs can be obtained by the above-described equations (1) and (2). The amount can be easily calculated.

  Next, after the fuel injection is performed, the air-fuel mixture is ignited by an ignition plug as shown in FIG. When the combustion is started, the gas pressure (combustion pressure) generated by the combustion causes the gas pressure in the in-cylinder combustion chamber to rise as a positive pressure, and starts pushing down the piston. When the combustion of the fuel further proceeds, the heat generated increases the gas temperature. And try to expand the volume.

  However, since the in-cylinder combustion chamber volume Vs does not suddenly increase, the pressure in the in-cylinder combustion chamber sharply increases to reach a peak pressure (Peak 1). In this state, the in-cylinder combustion chamber pressure is the peak pressure, the in-cylinder combustion chamber volume is Vs' slightly larger than Vs, and the in-cylinder combustion chamber gas is the combustion gas in the in-cylinder combustion chamber.

  Next, after the in-cylinder combustion chamber pressure reaches the peak pressure (Peak 1), as shown in FIG. 2 (D), the piston starts to drop in earnest, and the in-cylinder combustion chamber volume V becomes full-scale by the combustion gas. The pressure in the in-cylinder combustion chamber decreases to the atmospheric pressure as it expands. In this state, in the in-cylinder combustion chamber, the in-cylinder combustion chamber pressure is the atmospheric pressure, the in-cylinder combustion chamber volume is Va, and the in-cylinder combustion chamber gas is the combustion gas.

  When the piston further descends and the volume of the in-cylinder combustion chamber reaches the maximum value Vmax, a negative pressure is generated in the in-cylinder combustion chamber to reach the bottom dead center (BDC) as shown in FIG. . In this state, the in-cylinder combustion chamber pressure is a negative pressure, the in-cylinder combustion chamber volume is Vmax, and the in-cylinder combustion chamber gas is the combustion gas in the in-cylinder combustion chamber.

  Next, a description will be given of changes in the piston position and the gas pressure in the cylinder bore when the combustion is performed from the time of the fuel injection into the first explosion cylinder and the piston descends to reach the bottom dead center (BDC).

  As shown in FIG. 3, the initial piston position (initial crank angle (θPi ≒ 70 °)) is in the state of FIGS. 2A and 2B, and the in-cylinder combustion chamber pressure is atmospheric pressure. Then, when combustion is started by the ignition plug from this state, the in-cylinder combustion chamber pressure rapidly rises and reaches the peak pressure (Peak 1) in the state of FIG.

  Then, as the in-cylinder combustion chamber volume V expands, the in-cylinder combustion chamber pressure decreases and approaches the atmospheric pressure in the state of FIG. At this time, the pressure is reversed to a negative pressure after the crank angle (θPa ≒ 140 °) which reaches the atmospheric pressure. When the piston further descends, the state of FIG. 2E is reached, and a braking force due to negative pressure acts on the piston.

  As described above, the in-cylinder combustion chamber pressure from the initial crank angle (θPi ≒ 70 °) to the crank angle (θPa ≒ 140 °) reaching the atmospheric pressure acts to push down the piston, and the crank angle (θPa The pressure in the in-cylinder combustion chamber from {140 °) to the bottom dead center (BDC) acts to raise the piston.

  Therefore, it can be understood that the in-cylinder combustion chamber pressure can be effectively utilized if the exhaust valve is opened at a crank angle (θPa ≒ 140 °) that reaches the atmospheric pressure. Next, how to determine the crank angle (θPa) that reaches the atmospheric pressure will be described.

  First, the in-cylinder combustion chamber volume Va that becomes the atmospheric pressure in the state of FIG. Defining an expansion coefficient K (= Va / Vs), this expansion coefficient K is usually about K = 2 in a general internal combustion engine (displacement per cylinder is about 500 cc). Strictly, it is a value determined by the specification of the internal combustion engine.

  As described above, when the air-fuel mixture burns, the temperature of the combustion gas rises due to the heat generated, the piston depresses as the combustion gas expands, and the in-cylinder combustion chamber volume increases. However, on the other hand, as the heat escapes from the wall surface of the cylinder bore, the rise of the combustion gas temperature is suppressed, and the expansion of the in-cylinder combustion chamber volume is suppressed. As a result of the balance, the in-cylinder combustion chamber volume Va (expansion coefficient K) is settled. Therefore, the expansion coefficient K is determined by the specifications of the internal combustion engine.

  Incidentally, when the displacement per cylinder is reduced, the S / V ratio of the combustion chamber (S: wall area of the combustion chamber, V: volume of the combustion chamber) is increased, and the influence of heat release is relatively increased. Therefore, the in-cylinder combustion chamber volume Va approaching the atmospheric pressure becomes small, and the expansion coefficient K becomes relatively small. That is, the expansion coefficient K is determined by the specifications of the internal combustion engine. In the following description, it is assumed that a normal internal combustion engine (displacement per cylinder is about 500 cc) and the expansion coefficient K is about 2.

Next, the crank angle (θPa) when the in-cylinder combustion chamber volume Va approaches the atmospheric pressure will be determined. The following holds true as in the above-described equation (1).
Va = V0 + A × χa (3) ′
Here, since Va = K × Vs, Δa can be obtained.

Further, the following holds as in the case of the equation (2).
χa = R × (1-cos θPa) + λ × R × (1-√ (Ya)) (4) ′
Here, since Ya = 1− (sin ² θPa) / λ ² , χa is a function of θPa. Since χa is already known from equation (3), θPa can be calculated backward.
In this way, the crank angle (θPa) at the time of the in-cylinder combustion chamber volume Va approaching the atmospheric pressure can be obtained. Here, the crank angle (θPa) can be determined to be, for example, about 140 °.

  Next, assuming that the crank angle at the time of the in-cylinder combustion chamber volume Va approaching the atmospheric pressure is the crank angle (θPa), what is the opening timing of the exhaust valve (EOS), Will be described.

  Assuming that the opening timing (EOS) of the exhaust valve is earlier than the crank angle (θPa) at the time of the in-cylinder combustion chamber volume Va approaching the atmospheric pressure, the exhaust is performed in a state where the positive gas pressure is generated. Since the valve is opened, the pressure of the combustion gas escapes to the exhaust port side, so that the energy for pushing down the piston is lost.

  Conversely, assuming that the exhaust valve opening timing (EOS) is later than the crank angle (θPa) at the time of the in-cylinder combustion chamber volume Va approaching the atmospheric pressure, before the exhaust valve opening timing (EOS) is reached. Becomes negative pressure in the in-cylinder combustion chamber, and this negative pressure exerts braking on the lowering operation of the piston.

  That is, it is understood that it is appropriate to set the opening timing (EOS) of the exhaust valve around the crank angle (θPa) when the in-cylinder combustion chamber volume Va approaches the atmospheric pressure. As will be described later, in the present embodiment, the crank angle (θPa) at the time of the in-cylinder combustion chamber volume Va approaching the atmospheric pressure is determined according to the initial crank angle (θPi) corresponding to the initial piston position at the time of idling stop. Noting the difference, the opening timing (EOS) of the exhaust valve is changed. As a result, the engine torque at the time of the self-sustained start can be increased, the rotation start-up performance can be enhanced, and the self-sustained startability can be improved.

  Note that the expansion coefficient K (= Va / Vs) is usually about K = 2 and is determined depending on the specifications of the internal combustion engine. However, the same internal combustion engine varies depending on the operating state of the internal combustion engine. Supplementary explanation will be given in some cases.

  For example, in a self-sustained (self-sustained) start from an idle stop, the internal combustion engine is generally already in a warm-up state, but when the idle stop period is long or the outside air temperature is extremely low, the temperature of the internal combustion engine becomes low. It may go down. In this case, it is recognized that the effect of heat release from the cylinder bore becomes large, and the actual expansion coefficient K ′ becomes slightly smaller than the standard expansion coefficient K.

In this case, by introducing the correction coefficient α, the relationship between the actual expansion coefficient K ′ and the standard expansion coefficient K can be expressed.
Actual expansion coefficient K '= α × K (5)
Therefore, when the actual expansion coefficient K ′ is obtained, α is set to be smaller than “1” when the engine temperature is low, and conversely, when the engine temperature is high, the heat escape decreases. It is.

  Further, in the case of performing a so-called lean combustion by reducing the fuel injection amount in order to reduce the fuel consumption, since the calorific value also decreases due to the decrease in the fuel amount, the correction coefficient α is reduced. be able to.

  In this way, by obtaining the actual expansion coefficient K ′ corresponding to the state of the internal combustion engine, the correction value of the crank angle (θPa) in the actual combustion chamber when the in-cylinder combustion chamber volume Va approaches the atmospheric pressure is obtained. be able to. By correcting the opening timing (EOS) of the exhaust valve based on this, it becomes possible to perform the self-sustaining start more appropriately.

  FIGS. 4, 5, and 6 show the relationship between the initial piston position at the start of the start of the internal combustion engine or the initial piston position at the last stop of the engine and the valve timing. Specifically, it shows the relationship between the initial piston angle at the start of starting or the initial crank angle (θPi) corresponding to the initial piston position at the time of the previous engine stop and the exhaust valve opening timing (EOS).

  4, 5, and 6, the posture of the crankshaft (crankpin) is also shown. As shown in FIG. 1, the crank pin and the piston pin are actually connected via a connecting rod. However, FIGS. 4, 5, and 6 show the piston pin position as the crank pin position for simplicity. And is simply expressed. Further, an intake valve operating section (IOS-ICS) and an exhaust valve operating section of # 2 cylinder which is an expansion cylinder (first explosion cylinder), # 1 cylinder which is a compression cylinder opposed thereto, and # 2 cylinder (expansion cylinder). (EOS to ECS).

  In FIG. 4, when the initial crank angle (θPi1) is, for example, at a position of about 70 ° on the top dead center (TDC) side, the opening timing of the exhaust valve advances to the opening timing (EOS1) before the bottom dead center (BDC). Be horned. That is, the opening timing (EOS1) indicates the time when the in-cylinder combustion chamber pressure approaches the atmospheric pressure. Similarly, in FIG. 5, if the initial crank angle (θPi2) is at a position of about 90 ° between the top dead center (TDC) and the bottom dead center (BDC), the opening of the exhaust valve is greater than in the case shown in FIG. The timing is similarly retarded until an open timing (EOS2) near bottom dead center (BDC) at which the in-cylinder combustion pressure approaches the atmospheric pressure.

  Further, in FIG. 6, if the initial crank angle (θPi3) is at a position of approximately 110 ° lower than the middle between the top dead center (TDC) and the bottom dead center (BDC), the same as in FIG. 4, the opening timing of the exhaust valve is delayed until the opening timing (EOS3) near the bottom dead center (BDC). In this case, the in-cylinder combustion pressure is higher than the atmospheric pressure. That is, in the case of FIG. 6, since the initial piston position is located on the substantially lower side, the in-cylinder combustion chamber volume is large and the combustion start timing is considerably retarded. Is longer for the same expansion coefficient 2. For this reason, even if the piston reaches the vicinity of the bottom dead center (BDC), the in-cylinder combustion chamber pressure still maintains a positive pressure.

  Therefore, if the opening timing of the exhaust valve is delayed from the bottom dead center (BDC), the movement of the piston that has started to rise is suppressed by the positive pressure of the in-cylinder combustion chamber pressure, and the movement of the piston in the rising direction is reduced. Conversely, a braking force due to positive pressure is applied. As a result, the piston work will be reduced on the contrary. For this reason, in the case of FIG. 6, the setting is made so that the exhaust valve is opened at the bottom dead center (BDC).

  In this way, by opening the exhaust valve near the crank angle (θPa) that reaches the atmospheric pressure corresponding to the position of the initial crank angle (θPi) (EOS1, EOS2), the initial crank angle (θPi) is increased. The in-cylinder combustion chamber pressure up to the crank angle (θPa) that reaches the atmospheric pressure acts to push down the piston, so the in-cylinder combustion chamber pressure can be used effectively, and the combustion energy of the first explosion can be effectively converted to piston work. . If the pressure does not fall to the atmospheric pressure even at the bottom dead center (BDC), the exhaust valve is opened near the bottom dead center (EOS3).

  Next, how the in-cylinder pressure due to the combustion of the first explosive cylinder changes with the crank angle in FIG. 7 will be described with reference to the initial piston position shown in FIGS. 4, 5 and 6 as an example.

  The in-cylinder pressure change when the combustion is performed from the initial rank angle (θPi) shown in FIG. 4 from about 70 ° after the top dead center (TDC) is a change indicated by a characteristic p1 in FIG. That is, with the combustion of the first explosion, the gas pressure (combustion pressure) due to combustion rises from the initial crank angle (θPi1), and after reaching the peak pressure (Peak1), the gas pressure decreases as the piston descends. .

  Then, as described above, the gas pressure rapidly decreases due to the heat escaping to the cylinder bore, and the exhaust valve is opened near the crank angle (θPa1) at which the gas pressure becomes almost atmospheric pressure, that is, near the expansion coefficient K = 2. The valve is opened at the timing (EOS1), whereby the inside of the cylinder is maintained at substantially the atmospheric pressure. Thereby, the combustion energy of the first explosion can be effectively converted into piston work.

  That is, if the valve opening timing (EOS1) of the exhaust valve is later than the crank angle (θPa1) at which the gas pressure becomes substantially atmospheric pressure, the inside of the cylinder becomes a negative pressure (less than atmospheric pressure), and the piston descends. As a result, the braking force due to the negative pressure acts on the gas, and the combustion energy due to the gas pressure is wasted. Conversely, if the exhaust valve opening timing (EOS1) is earlier than the crank angle (θPa1) at which the gas pressure becomes substantially atmospheric pressure, the exhaust valve is opened with the in-cylinder pressure higher than the atmospheric pressure. The high gas pressure escapes to the side G, and the energy to push down the piston decreases accordingly.

  Therefore, by adjusting the opening timing (EOS1) of the exhaust valve to around the crank angle (θPa1) at which the gas pressure becomes substantially atmospheric pressure, the combustion energy of the first explosion can be converted to the piston work most effectively. become.

  Next, the in-cylinder pressure change when the combustion is performed from the initial rank angle (θPi) shown in FIG. 5 from about 90 ° after the top dead center (TDC) is a change shown by the characteristic p2 in FIG. is there. As in the case of FIG. 4, the gas pressure (in-cylinder pressure) due to combustion rises from the initial crank angle (θPi2) with the combustion of the first explosion, and as the piston descends after reaching the peak pressure (Peak2), The gas pressure decreases.

  Then, as described above, the gas pressure decreases rapidly due to the heat escape to the cylinder bore, and the exhaust valve is opened near the bottom dead center (BDC), which is the crank angle (θPa2) at which the gas pressure becomes almost atmospheric pressure. The valve is opened at the timing (EOS2), whereby the inside of the cylinder is maintained at substantially the atmospheric pressure. Thereby, the combustion energy of the first explosion can be effectively converted into piston work.

  Next, the in-cylinder pressure change when the combustion is performed from the initial rank angle (θPi) of 110 ° after the top dead center (TDC) shown in FIG. 6 changes as indicated by a characteristic p3 in FIG. . As in the case of FIG. 4, the gas pressure (in-cylinder pressure) due to the combustion rises from the initial crank angle (θPi3) with the combustion of the first explosion, and after reaching the peak pressure (Peak3), the gas descends as the piston descends. The pressure drops.

  Then, as described above, the gas pressure rapidly decreases due to the heat escape to the cylinder bore, but the exhaust valve is forcibly opened near the bottom dead center (BDC) just before the gas pressure becomes almost atmospheric pressure. The valve is opened at (EOS3), whereby the inside of the cylinder is maintained at substantially atmospheric pressure. This effectively converts the combustion energy of the first explosion into piston work in the process up to the bottom dead center, and the negative energy that the combustion energy (positive pressure) of this first explosion suppresses the piston rise after the bottom dead center (Braking action) can be suppressed. It should be noted that this EOS3 is near the bottom dead center, and as a result, it is almost at the same time as the above EOS2.

  As described above, the reason why the exhaust gas valve is forcibly opened near the bottom dead center (BDC) is to avoid the above-described braking action due to the positive pressure. That is, in the case of FIG. 6, since the initial piston position (θPi3) is located considerably on the lower side, the in-cylinder combustion chamber volume is large, and the combustion start timing is considerably retarded. The period until the pressure approaches the atmospheric pressure also becomes longer for the same expansion coefficient K = 2. For this reason, even if the piston reaches the vicinity of the bottom dead center (BDC), the in-cylinder combustion chamber pressure still maintains a positive pressure.

  Therefore, if the opening timing of the exhaust valve is delayed from the bottom dead center (BDC), the movement of the piston that has started to rise is suppressed by the positive pressure of the in-cylinder combustion chamber pressure, and the movement of the piston in the rising direction is reduced. Conversely, a braking force due to positive pressure is applied. As a result, the piston work will be reduced on the contrary. For this reason, in the case of FIG. 6, the setting is made such that the exhaust valve is forcibly opened at the bottom dead center (BDC).

  The control of the opening timing (EOS) of the exhaust valve described above may be performed when the internal combustion engine is automatically stopped, or may be performed when the internal combustion engine is automatically started. It is also possible to perform both.

  Next, a control flow for controlling the opening timing (EOS) of the exhaust valve will be described. FIG. 8 is a control flowchart when the internal combustion engine is automatically stopped, and FIG. 9 is a control flow when the internal combustion engine is automatically started. 4 shows a flowchart.

  First, a control flowchart when the internal combustion engine is automatically stopped will be described. This control flow is executed by the microcomputer constituting the controller 22.

{Step S10}
In step S10, parameters necessary for executing each control step described below are read as the engine operating state. The parameters are detected from each sensor, converted into physical quantities that can be processed by a microcomputer, and calculated. When the detection of the parameters is completed in step S10, the process proceeds to step S11.

{Step S11}
In step S11, it is determined whether or not the internal combustion engine has reached a stop condition, for example, an idle stop condition. The idle stop condition is determined by detecting, for example, brake pedal information, accelerator pedal information, shift position information of the transmission, and the like. Of course, it is also possible to make a determination using other information.

  If it is determined in step S11 that the idle stop condition is not satisfied, the process returns to wait for the next start timing. On the other hand, when it is determined in step S11 that the idle stop condition is satisfied, the process proceeds to step S12.

{Step S12}
In step S12, since it is determined that the idling stop condition is satisfied in step S11, the fuel injection cut process and the ignition cut process are executed to stop the internal combustion engine, and the internal combustion engine is automatically stopped. In this state, the rotation speed of the internal combustion engine decreases toward a stop. Upon completion of the fuel injection cut process and the ignition cut process, the process proceeds to step S13.

{Step S13}
In step S13, it is determined whether or not the decreasing rotational speed N (rpm) has reached a predetermined extremely low rotational speed ΔN or less. If it is determined that the rotation speed has not reached the extremely low rotation speed ΔN or less, the same determination in step S13 is executed again. If it is determined that the internal combustion engine has reached the extremely low rotational speed ΔN or less by repeating this determination, it is determined that the internal combustion engine is just before stopping, and the process proceeds to step S14.

{Step S14}
In step S14, control is performed to the initial crank angle (θPi), which is the initial piston position to be stopped by the drive motor. For example, based on the crank angular velocity at the compression top dead center (TDC), the cylinder (# 2 cylinder) which is the first explosion cylinder when the engine is stopped and which is in the expansion stroke is determined, and the expansion stroke cylinder (# 2 cylinder) is similarly set as the target. A control signal is output to the drive motor so that the target initial crank angle (θPit) is obtained. Thus, the piston position is controlled so as to reach the target initial crank angle (θPit). Here, as the target initial crank angle (θPit), for example, around 90 ° after the compression top dead center (TDC) shown in FIG. 7 is selected. When this process is completed, the process moves to step S15.

{Step S15}
In step S15, it is determined whether or not the rotational speed N = 0, and it is detected that the internal combustion engine has stopped. If it is determined that the internal combustion engine has not stopped, the process returns to step S14 and the same control is repeated. Then, when the internal combustion engine actually stops, the process proceeds to step S16.

{Step S16}
In step S16, the actual initial crank angle (θPia) corresponding to the actually stopped piston position is read by the crank angle sensor. This state becomes the piston position of the first explosion cylinder (# 2 cylinder). When the actual initial crank angle (θPia) is detected, the process proceeds to step S17.

{Step S17}
In step 17, it is determined whether or not the actual actual initial crank angle (θPia) detected in step S16 falls within an allowable range. In step S14, the drive motor is controlled to attain the target initial crank angle (θPit), and the actual initial crank angle (θPia) is determined as a result of this control.

  Here, the allowable range is the initial crank angle shown in FIG. 7, and is determined from the initial crank angle (θPi1 = 70 °) to the initial crank angle (θPi3 = 110 °). Therefore, since it is the target initial crank angle (θPit = 90 °), the actual initial crank angle (θPia) is also a crank angle near this.

  When it is determined that the actual initial crank angle (θPia) is within the allowable range, the process proceeds to step S18. When it is determined that the actual initial crank angle (θPia) is not within the allowable range, the process returns to step S14. Then, the piston position of the first explosion cylinder (# 2 cylinder) is adjusted by the drive motor.

{Step S18}
In step S18, since it is determined in step S17 that the actual initial crank angle (θPia) falls within the allowable range, the target target opening timing (EOSt) of the exhaust valve corresponding to the actual initial crank angle (θPia) is determined. Is calculated. Since the target opening timing (EOSt) is the crank angle (θPa) at which the in-cylinder combustion chamber reaches the atmospheric pressure shown in FIG. 7, the target opening timing (EOSt) is calculated by executing the above-described calculation. Can be.

The crank angle (θPa) that becomes the atmospheric pressure is not obtained by calculation, but the crank angle (θPa) that becomes the atmospheric pressure corresponding to each initial crank angle (θPi) is obtained by an adaptation work (matching) or simulation. Mapping may be performed, and the map may be stored in the controller 22 as a map, and the actual control may refer to this map to obtain the map. Adopting such a map has the effect of shortening the calculation time and enabling faster control. As a result, for example, the actual initial crank angle (θPia) becomes approximately 90 ° after compression top dead center (TDC). If there is, the opening timing (EOS2) near the bottom dead center (BDC) shown in FIG. 7 is selected as the target opening timing (EOSt) of the exhaust valve. Here, if the actual initial crank angle (θPia) is about 70 ° after the compression top dead center (TDC), the target opening timing (EOSt) of the exhaust valve is from the bottom dead center (BDC) shown in FIG. The advanced opening timing (EOS1) is selected. Further, when the actual initial crank angle (θPia) is about 110 ° after the compression top dead center (TDC), the target opening timing (EOSt) of the exhaust valve is around the bottom dead center (BDC) shown in FIG. A certain opening time (EOS3) is selected. When the target opening timing (EOSt) is determined, the process proceeds to step S19. In this case, the in-cylinder pressure is positive even at the bottom dead center, but in order to suppress the subsequent piston braking action, it is selected to forcibly open the exhaust valve at EOS3 near the bottom dead center. is there.

{Step S19}
In step S19, the target opening timing (EOSt) obtained in step S18 is given as a control signal to the exhaust VTC, and the exhaust VTC is adjusted so that the exhaust valve opens at the target opening timing (EOSt). Similarly, a target target closing timing of the intake valve (ICSt) is given to the intake VTC as a control signal, and the intake VTC is adjusted so that the intake valve closes at the target closing timing (ICSt). Here, the target closing timing (ICSt) of the intake valve is set later than the normal state, and the decompression function by the late closing of the intake valve improves the startability. When these processes are completed, the process moves to step S20.

{Step S20}
In step S19, the exhaust VTC and the intake VTC are controlled so that the target opening timing (EOSt) of the exhaust valve and the target closing timing (ICSt) of the intake valve are obtained. As a result of this control, the actual actual opening timing (EOSa) is obtained. ) And the actual actual closing timing (ICSa) are determined.

  In step S20, the actual actual opening timing (EOSa) as a result of the adjustment performed to open at the target opening timing (EOSt) of the exhaust valve, and the target closing timing (ICSt) of the intake valve, executed in step S19. The actual actual closing timing (ICSa) as a result of the adjustment to close the valve is detected, and whether the actual opening timing (EOSa) of the exhaust valve is controlled to the target opening timing (EOSt) and the actual closing timing of the intake valve are determined. It is determined whether the closing timing (ICSa) is controlled to the target closing timing (ICSt).

  Therefore, it is determined that the actual opening timing (EOSa) of the exhaust valve does not coincide with the target opening timing (EOSt) of the exhaust valve, and that the actual closing timing (ICSa) of the intake valve does not coincide with the target closing timing (ICSt) of the intake valve. Then, the process returns to step S19, in which the exhaust valve is adjusted to open at the target opening timing (EOSt), and similarly, the intake valve is adjusted to close at the target closing timing (ICSt). I do. This control can be executed by well-known feedback control of the opening timing and the closing timing.

  On the other hand, it is determined that the actual opening timing (EOSa) of the exhaust valve matches the target opening timing (EOSt) of the exhaust valve, and that the actual closing timing (ICSa) of the intake valve matches the target closing timing (ICSt) of the intake valve. Then, the process moves to step S21.

{Step S21}
In step S21, a holding current is supplied to the exhaust VTC and the electric motor provided in the intake VTC so that the target exhaust valve opening timing (EOSt) and the target intake valve closing timing (ICSt) are maintained. Flush and prepare for automatic start. If the exhaust VTC and the intake VTC having high reverse efficiency characteristics are used, the holding current can be stopped.

  According to such control and setting, the initial piston position of the first explosion cylinder can be suppressed from changing while the engine is stopped, and the gas pressure (combustion energy) of the first explosion cylinder is stably applied to the piston at the next start. It can be given effectively, and good startability can be obtained.

  Next, a control flowchart at the time of automatically starting the internal combustion engine will be described. This control flow is also executed by the microcomputer constituting the controller 22. This control flow may be executed in addition to the control at the time of the automatic stop shown in FIG. 8 described above, or may be executed solely by the present control flow.

  In the following description, since the automatic start is different from the automatic stop, the symbols indicating the crank angle and the opening / closing timing of the exhaust valve or the intake valve are distinguished by adding “′”.

{Step S30}
In step S30, parameters (including the engine temperature) necessary to execute the following control steps are read as the engine operating state. The parameters are detected from each sensor, converted into physical quantities that can be processed by a microcomputer, and calculated. When the detection of the parameters is completed in step S30, the process proceeds to step S31.

{Step S31}
In step S31, it is determined whether the condition is a start condition. If the starting condition is not satisfied, the process returns to the start and waits for the next starting timing. On the other hand, when the starting condition is satisfied, the process proceeds to step S32.

{Step S32}
In step S32, it is determined whether an automatic start condition is satisfied. In the state where the vehicle is stopped by the idle stop, it is possible to determine whether the automatic start is performed by detecting, for example, brake pedal information, accelerator pedal information, shift position information of the transmission, and the like. Of course, it is also possible to make a determination using other information. For example, if the engine temperature is equal to or lower than a predetermined temperature, the starting of the internal combustion engine by the self-sustaining combustion is difficult because the mechanical system has a large friction, and the starting is performed by an external drive motor such as a normal starter motor. Therefore, if it is determined that the automatic start is difficult, the process proceeds to step S33, and if it is determined that the automatic start is possible, the process proceeds to step S38.

{Step S33}, {Step S34}, {Step S35}, {Step S36}, {Step S37}
If it is determined in step S32 that the condition is not the automatic start condition, the process is regarded as normal start, and the processing of steps S33 to S37 is executed. Note that the normal start is not the purpose of the present invention and will be briefly described.

  If it is determined in step S32 that the condition is not the automatic start condition, the start is performed by a starter motor or a hybrid motor in step S33. In this case, since the normal combustion is performed in which the combustion stroke is performed after the first explosion cylinder has passed through the compression stroke, the normal target exhaust valve opening timing (EOE) is set to the exhaust VTC and the normal target intake valve is set to the intake VTC in step S34. The control signal of the valve closing timing (ICE) is output. Further, in step S35, a fuel injection signal and an ignition signal are sequentially output for each cylinder to start the engine. When the start is completed, the engine temperature is detected in steps S35 and S36, the degree of the increase is monitored, and the routine returns.

{Step S38}
If it is determined in step S32 that the self-sustaining start condition is satisfied, the process of step S38 is performed. In step S38, the actual initial crank angle (θP'ia = actual position), which is the current stop crank angle of the first explosive cylinder, is detected by the crank angle sensor. Initial opening timing information is obtained from the actual initial crank angle.

{Step S39}
In step 39, it is determined whether or not the actual actual initial crank angle (θP'ia) detected in step S38 falls within an allowable range. Here, the allowable range is the initial crank angle shown in FIG. 7, and is determined from the initial crank angle (θP′i1 = 70 °) to the initial crank angle (θP′i3 = 110 °).

  When it is determined that the actual initial crank angle (θP′ia) is within the allowable range, the process proceeds to step S40, and when it is determined that the actual initial crank angle (θP′ia) is not within the allowable range. Since it is considered that the self-sustaining combustion is difficult, the routine proceeds to step S33 and the normal start is executed. Here, when the automatic stop control of FIG. 8 has been performed, there is a very high possibility that the automatic stop control is within the allowable range.

{Step S40}
In step S40, since it is determined in step S39 that the actual initial crank angle (θP'ia) is within the allowable range, the target opening of the exhaust valve corresponding to the actual initial crank angle (θP'ia) is determined. The timing (EOS't) is calculated and obtained. Since the target opening timing (EOS't) is the crank angle (θP'a) at which the in-cylinder combustion chamber reaches the atmospheric pressure, the target opening timing (EOS't) is calculated by executing the above-described calculation. You can ask. In this case as well, the crank angle (θP′a) at which the atmospheric pressure is attained can be obtained not by calculation but by storing a map in the controller 22 and referring to this map in actual control.

  As a result, for example, if the actual initial crank angle (θP′ia) is about 90 ° after the compression top dead center (TDC), the target opening timing (EOS′t) of the exhaust valve is lower than that shown in FIG. The opening time (EOS2) near the dead center (BDC) is selected. If the actual initial crank angle (θP′ia) is about 70 ° after the compression top dead center (TDC), the target opening timing (EOS′t) of the exhaust valve becomes the bottom dead center (EOS′t) shown in FIG. The opening timing (EOS1) advanced from BDC) is selected. Further, if the actual initial crank angle (θP′ia) is around 110 ° after the compression top dead center (TDC), the target opening timing (EOS′t) of the exhaust valve becomes the bottom dead center (BDC) shown in FIG. ) Is selected. Here, since this EOS3 is near the bottom dead center, it is almost at the same time as the above EOS2.

  Note that the target opening timing (EOS't) of the exhaust valve can be corrected according to the engine temperature at the time of starting. For example, the lower the engine temperature is, the more the combustion in the self-sustaining combustion may be deteriorated. Therefore, the crank angle period until the combustion gas expands to reach the atmospheric pressure is reduced, and the target opening timing (EOS 'T) may be advanced. When the target opening timing (EOS't) is determined, the process proceeds to step S41.

{Step S41}
In step S41, the target opening timing (EOS't) obtained in step S40 is given to the exhaust VTC as a control signal, and the exhaust valve is opened at the target opening timing (EOS't) by the exhaust VTC. adjust. Similarly, the target closing timing (ICS't) of the intake valve is given to the intake VTC as a control signal, and the intake VTC is adjusted so that the intake valve closes at the target closing timing (ICS't). . Here, the target closing timing (ICS't) of the intake valve is set later than the normal state similarly to the control of FIG. 8, and the decompression function by the late closing of the intake valve improves the startability. I have. When these processes are completed, the process moves to step S42.

{Step S42}
In step S41, the exhaust VTC and the intake VTC are controlled so that the target opening timing of the exhaust valve (EOS't) and the target closing timing of the intake valve (ICS't) are obtained. As a result of this control, the exhaust valve Of the intake valve (EOS'a) and the actual closing timing of the intake valve (ICS'a).

  In step S42, the actual actual opening timing (EOS'a) as a result of the adjustment performed to open at the target opening timing (EOS't) of the exhaust valve executed in step S41, and the target closing of the intake valve are performed. An actual actual opening timing (ICS'a) as a result of adjusting the valve to close at the opening timing (ICS't) is detected, and the actual opening timing (EOS'a) of the exhaust valve is set to the target opening timing (EOS '). t) and whether the actual closing timing (ICS'a) of the intake valve is controlled to the target closing timing (ICS't).

  Therefore, the actual opening timing (EOS'a) of the exhaust valve does not match the target opening timing (EOS't) of the exhaust valve, and the actual closing timing (ICS'a) of the intake valve is set to the target closing timing (ICS) of the intake valve. If it is determined that the exhaust valve does not coincide with the target opening timing (ICS't), the process returns to step S41 to adjust the exhaust valve to open at the target opening timing (EOS't). Adjust to close the valve. This control can be executed by well-known feedback control of the opening timing and the closing timing.

  On the other hand, the actual opening timing of the exhaust valve (EOSa ') coincides with the target opening timing of the exhaust valve (EOS't), and the actual closing timing of the intake valve (ICS'a) is the target closing timing of the intake valve (ICS't). If it is determined that they match, the process moves to step S43.

{Step S43}
In step S43, fuel is injected from the fuel injection valve into the expansion stroke cylinder, which is the first explosion cylinder, and then ignited by a spark plug after a predetermined atomization time has elapsed, so that a so-called external drive motor is not used. Shift to start by independent combustion.

  FIG. 10 shows an initial crank angle (θP′i) when the piston is stopped in the expansion stroke of the first explosive cylinder after the completion of warm-up, and a target opening timing of the exhaust valve controlled correspondingly (θP′i). EOS't). The same applies to the control in FIG.

  As described above, when the initial crank angle (θP′i) is, for example, θP′i = 70 ° on the top dead center (TDC) side, the target opening timing (EOS′t) is as shown in FIG. It is controlled at the target opening timing (EOS1) on the top dead center (TDC) side. When the initial crank angle (θP′i) is, for example, θP′i = 90 °, which is between the top dead center (TDC) and the bottom dead center (BDC), as shown in FIG. EOS't) is controlled to a target opening timing (EOS2) near bottom dead center (BDC) which is retarded from the target opening timing (EOS1).

  Further, when the initial crank angle (θP′i) is, for example, θP′i = 110 ° on the bottom dead center (BDC) side, as shown in FIG. It is controlled to a target opening timing (EOS3) near the bottom dead center (BDC) which is retarded from the timing (EOS1). This is because, as described above, even if the piston approaches the bottom dead center (BDC), the gas pressure in the in-cylinder combustion chamber is higher than the atmospheric pressure, and the target opening timing (EOS't) is set near the bottom dead center (BDC). This is to avoid a phenomenon that the movement of the piston is stopped even if the target opening timing (EOS3) is further retarded.

  As described above, the crank angle stop position control keeps the initial crank angle (θP′i) within the allowable range (θPi1 to θPi3), and the opening timing (EOS) of the exhaust valve corresponding to the initial crank angle (θP′i). By performing the control of (1), it is possible to realize a start by independent combustion "without relying on an external drive motor". Here, "not relying on the externally driven motor" may mean starting by independent combustion without using the power of the externally driven motor, or starting using both independent combustion and the externally driven motor. It may be.

  In the former case, the start can be performed quickly and with low noise, and the durability of the external drive motor can be improved because the torque of the external drive motor is not used. Further, in a vehicle such as a hybrid vehicle, a drive motor margin torque to be held for starting is not required, so that a drive motor torque usable for traveling can be increased. The driving range in which the vehicle can run on the vehicle can be expanded to improve practical fuel efficiency. In the latter case, by using the torque of the external drive motor partially, when the stability of the self-sustaining combustion cannot be ensured, the occurrence of the instability of the starting is suppressed to achieve a stable starting performance. Can be secured.

  On the other hand, when the initial crank angle (θP′i) deviates from the allowable range (θP′i1 to θP′i3), reliable starting by independent combustion is considered to be difficult, and normal combustion using an external drive motor is performed. The start is performed. In this case, the opening timing of the exhaust valve is the opening timing at the time of normal startup (EOE). Further, in the case of cold start, since the friction of the internal combustion engine is large, the start using the external drive motor is performed regardless of the initial crank angle (θP′i).

  Returning again to step S43, when the crankshaft rotates by self-sustained combustion and the first explosion cylinder exceeds the bottom dead center, the subsequent cylinder (# 1 cylinder in FIGS. 4 to 6) becomes the compression top dead center (TDC). Beyond. Here, since the closing timing (ICS) of the intake valve is extremely late, the compression top dead center (TDC) can be easily exceeded by the decompression function by the late closing of the intake valve.

  Then, in the process, the compression operation is performed in the subsequent combustion of the first explosive cylinder, and the compressed air-fuel mixture is ignited by the ignition plug and moves to the expansion stroke by the combustion. In this case, the independent combustion (= compression operation is not performed) Start from state) is gone. Therefore, it is preferable to change the opening timing (EOE) of the exhaust valve and the closing timing (ICE) of the intake valve at the time of normal startup. Therefore, the valve timing is changed in the next step. When this step S43 ends, the process moves to step S44.

{Step S44}
In step S44, it is determined whether or not the crankshaft starts rotating and has rotated by a predetermined angle. If it is determined that the rotation has not been performed by the predetermined angle, the process returns to step S43 again to execute the same processing. Here, the predetermined angle may be set to a value exceeding the rotation angle at which the exhaust valve opening timing (EOS) of the first explosive cylinder (# 2 cylinder in FIGS. 4 to 6) is reached. Therefore, the predetermined angle needs to be increased to some extent.

  Here, when the number of cylinders is small, the inter-cylinder combustion interval is long, so that a relatively large predetermined angle is used. When the number of cylinders is large, the combustion interval is short, so that the relatively small predetermined angle may be used. If it is determined in this step S44 that the rotation has been made by a predetermined angle, the process proceeds to step S45.

{Step S45}
In step S45, the target opening timing (EOE) at the time of normal start is given to the exhaust VTC as a control signal, and the exhaust VTC is adjusted so that the exhaust valve is opened at the target opening timing (EOE). Similarly, a target target closing timing (ICE) of the intake valve is given to the intake VTC as a control signal, and the intake VTC is adjusted so that the intake valve closes at the target closing timing (ICE).

  If it is determined in step S44 that the crankshaft has rotated by the predetermined angle, the opening timing (EOE) of the exhaust valve and the closing timing (ICE) of the intake valve during normal startup are changed as described in step S43. Is more preferred. In other words, after self-sustaining combustion, the initial explosion cylinder (# 2 cylinder in FIGS. 4 to 6) again performs normal combustion (not self-sustaining combustion) in the second cycle after about two revolutions of the crankshaft. Therefore, in that case, it is preferable that the timing is converted to the valve timing of the normal intake / exhaust valve shown in FIG.

  For example, when the first explosion cylinder performs the self-sustained combustion in the state shown in FIG. 5, since the combustion in the next second cycle is the normal combustion accompanied by the compression operation, the ignition timing is more advanced than the state shown in FIG. Is set to the regular timing at the time of normal startup of the vehicle. Therefore, as shown in FIG. 11, the opening timing of the exhaust valve is advanced from the opening timing (EOS) of the exhaust valve during self-sustained combustion to the opening timing (EOE) of the exhaust valve during normal combustion. The opening timing (EOE) of the exhaust valve is on the advance side from the bottom dead center (BDC), and when the exhaust VTC is provided with an advance biasing spring, the advance operation is performed quickly. The exhaust gas discharged earlier than in the self-sustaining combustion can raise the exhaust gas temperature and promote warm-up of the downstream catalyst.

  On the other hand, the closing timing of the intake valve is advanced from the closing timing (ICS) of the intake valve during the independent combustion to the closing timing (ICE) of the intake valve during the normal combustion. Here, if the intake VTC is provided with an advance biasing spring, the advance operation is performed quickly. As a result, the charging efficiency (torque) can be increased, and the rotation increase in the subsequent combustion can be promoted. Also, the so-called valve overlap is expanded, and the exhaust gas containing high-concentration exhaust harmful components (HC, CO, etc.) discharged to the exhaust port side at the end of the exhaust stroke can be partially returned to the intake system. it can. Then, the high-concentration exhaust harmful components are reburned in the next combustion cycle, so that the exhaust harmful components exhausted from the internal combustion engine can be reduced as a result.

  When the exhaust valve is adjusted to the target opening timing (EOE) by the exhaust VTC, and similarly, when the intake valve is adjusted to the target closing timing (ICE) by the intake VTC, the process proceeds to step S46.

{Step S46}
In step S46, normal ignition combustion is executed by injecting fuel from the fuel injection valve into the subsequent combustion cylinder and igniting the ignition plug at a predetermined ignition timing thereafter. As described above, the torque in the subsequent combustion cylinder is increased to promote the rotation increase, and further, by reducing the exhaust harmful components of the internal combustion engine and activating the catalyst (warm-up), the exhaust harmful components are greatly reduced. , Quick startability can be obtained.

  As described above, according to the present embodiment, the opening timing of the first exhaust valve that is set after the combustion of the first explosive cylinder that performs the first combustion in the expansion stroke at the start of starting is set at least at the start of starting or at the time of the previous engine stop. By adjusting based on the initial piston position information of the first explosion cylinder, the gas pressure (combustion energy) of the first explosion cylinder can be effectively given to the piston even if the initial piston position of the first explosion cylinder varies. As a result, good starting performance can be obtained.

  Next, a second embodiment of the present invention will be described. This embodiment is different from the above-described first embodiment in that an exhaust valve is provided with an exhaust VEL capable of continuously adjusting a valve operating angle and a lift. As described above, the exhaust VEL has the same configuration as that described in, for example, JP-A-2012-36864.

  FIG. 12 shows changes in the valve operating angle and the lift of the exhaust valve. The characteristics of the minimum operating angle D1 and the minimum lift L1 are equivalent to the constant operating angle and the constant lift of the first embodiment. As can be seen from this figure, the operating angle is expanded from D1 to D4 corresponding to the minimum lift L1 to the maximum lift L4, and the exhaust VEL is a mechanism in which the operating angle increases as the lift increases.

  The exhaust VEL of the present embodiment is provided with an urging spring that urges the exhaust valve in the direction of a large operating angle (large lift), that is, in a direction in which the opening timing of the exhaust valve is advanced. The exhaust valve tends to be stabilized at the minimum operating angle at which the opening timing of the exhaust valve becomes the most retarded angle due to the spring reaction force of the valve spring. For this reason, in the exhaust VEL, the conversion responsiveness of moving the opening timing of the exhaust valve to the most advanced side tends to deteriorate. On the other hand, by providing the biasing spring, the conversion responsiveness of moving the opening timing of the exhaust valve to the most advanced angle side can be improved.

  FIGS. 13, 14 and 15 show the relationship between the initial piston position and the valve timing at the time of automatic start of the internal combustion engine or the previous automatic stop using the exhaust VEL. Specifically, the relationship between the initial crank angle (θPi) corresponding to the initial piston position at the time of automatic start or previous automatic stop and the opening timing (EOS) of the exhaust valve is shown.

  FIG. 13 shows a case where the characteristics are the minimum operation angle D1 and the minimum lift L1, which are equivalent to the operation angle and the lift of the first embodiment. Therefore, the characteristics of FIG. 13 are the same as the characteristics of FIG. If the initial crank angle (θPi2) is at a position of about 90 ° between the top dead center (TDC) and the bottom dead center (BDC), the opening timing of the exhaust valve becomes the opening timing (EOS2) near the bottom dead center (BDC). ).

  In this case, it is the most retarded position. Further, the closing timing (ECS2) of the exhaust valve is almost the same as the opening timing (IOS) of the intake valve, and the valve overlap is almost “0”. Therefore, similarly to the first embodiment shown in FIG. 5, gas pressure due to combustion can be effectively converted into piston work.

  Next, FIG. 14 shows a case where the characteristics of the medium operating angle D2 and the medium lift L2 are set, and the operating angle of the exhaust valve is expanded to the medium operating angle D2 and the opening timing is advanced. Therefore, if the initial crank angle (θPi1) is at a position, for example, about 70 ° on the top dead center (TDC) side, the opening timing of the exhaust valve is advanced to the opening timing (EOS1) before the bottom dead center (BDC). You. Therefore, also in this case, similarly to the first embodiment, the gas pressure due to combustion can be effectively converted into piston work.

  On the other hand, the closing timing (ECS′1) of the exhaust valve is more greatly retarded than the closing timing (ECS1) of the exhaust valve shown in FIG. 4 of the first embodiment, and the closing timing (ECS2) of the exhaust valve shown in FIG. ) Is maintained at approximately the same level, and as a result, the valve overlap is also maintained at approximately “0”. Therefore, even if the initial crank angle is different from the initial crank angle (θPi1) or the initial crank angle (θPi2), the closing timing of the exhaust valve (ECS′1) and the closing timing of the exhaust valve (ECS2) are substantially different. However, since the valve overlap is substantially "0" or the fluctuation of the valve overlap is suppressed, an excellent effect of improving the rotation start-up characteristic can be obtained.

  That is, in the case of FIG. 4, since the closing timing (ECS1) of the exhaust valve is on the advance side at the initial crank angle (θPi1), a large negative overlap is formed, and the top dead center (TDC) ) To the opening timing (IOS) of the opening of the intake valve (the so-called minus overlap section), a negative pressure is generated in the cylinder, and the pump loss impedes the increase in rotation. The start-up of rotation at the start may be hindered. On the other hand, in the case of FIG. 14, since there is almost no minus overlap, there is an effect that the pump loss can be suppressed and the rotation start-up characteristic can be improved.

  Further, since the closing timing (ECS′1) of the exhaust valve and the closing timing (ECS2) of the exhaust valve do not change or are suppressed from changing, there is an effect that the internal EGR amount can be stabilized. That is, in the exhaust stroke, the exhaust valve opens before the exhaust top dead center (TDC) in response to the rise of the piston, the piston moves beyond the exhaust top dead center (TDC), and then the piston descends. Works to close.

  Since the closing timing of the exhaust valve (ECS′1) and the closing timing of the exhaust valve (ECS2) do not change or the fluctuation is suppressed, the piston descends from the top dead center (TDC), and the exhaust The amount of internal EGR (exhaust gas) sucked into the cylinder before the valve closes is stable, and changes to the normal exhaust valve opening timing (EOE) and the normal intake valve closing timing (ICE) during the subsequent combustion. The combustion in the changing process at the time of transient is stabilized.

  The opening timing (EOS) of the exhaust valve tends to be stabilized on the retard side due to the valve spring reaction force of the exhaust valve, and therefore, the response in the advance direction tends to deteriorate. However, in this embodiment, the exhaust valve opening timing (EOS) is urged in the advance direction by the exhaust VEL urging spring and the exhaust VTC urging spring. It can be improved.

  Therefore, when changing the opening timing (EOS2) of the exhaust valve at the initial stage of the start corresponding to the initial crank angle (θPi2) shown in FIG. 13 to the opening timing (EOE) of the exhaust valve for the subsequent combustion as shown in FIG. Responsiveness can be improved.

  Next, FIG. 15 shows the case where the characteristics of the maximum operating angle D4 and the maximum lift L4 are set, and the operating angle of the exhaust valve is expanded to the maximum operating angle D4 and the opening timing is advanced. Therefore, if the initial crank angle (θPi0) is at a position, for example, about 50 ° on the top dead center (TDC) side, the opening timing of the exhaust valve is advanced to the opening timing (EOS0) on the top dead center (TDC) side. You.

  If the initial crank angle (θPi0) is, for example, at a position of about 50 ° on the top dead center (TDC) side, the piston stop position is positionally higher with respect to the cylinder bore, and the combustion chamber volume of the expansion cylinder decreases. The amount of the mixture also decreases relatively. Then, the characteristic of the in-cylinder pressure is such that the characteristic p1 in FIG. 7 is shifted from the characteristic p1 by 20 ° to the top dead center (TDC) side.

  For this reason, even if the combustion is self-sustained, the combustion energy itself is small, and the pressure drops to near the atmospheric pressure again in a relatively short period (crank angle). Therefore, the opening timing of the exhaust valve is further advanced (EOS0). It is necessary to

  Therefore, the operating angle is enlarged by the exhaust VEL, and the exhaust valve closing timing (ECS0) is the same as the exhaust valve closing timing (ECS2) of FIG. 13 and the exhaust valve closing timing (ECS′1) of FIG. Further, control is performed such that the valve overlap is maintained near "0".

  Such control of the exhaust VEL improves the rotation rise characteristics by reducing the pump loss, and stabilizes the combustion in the process of changing the valve timing at the transition from the self-sustained combustion to the normal combustion. Even when (θPi0) is at a position of about 50 ° on the side of the top dead center (TDC), the self-sustained start by the independent combustion can be performed. By using the exhaust VEL as in the present embodiment, the region in which the engine can be started by self-combustion can be expanded as compared with the first embodiment.

  In the first and second embodiments described above, an electric variable phase mechanism (VTC) is shown as one embodiment of the exhaust variable valve. However, the present invention is not limited to the electric type and may be a hydraulic type. is there. For example, if a hydraulic accumulator such as that described in the non-patent document “MTZ 07-08 / 2013 (title: NEW CAMSHAFT PHASER MODULE FOR AUTOMOBILE ENGINES)” is used, the valve timing may be set at an early stage of engine stop or start. Since the present invention can be changed, the present invention can be applied.

  Further, as another embodiment, a combination of a variable operation angle mechanism (VEL) and a variable phase mechanism (VTC) is shown as the exhaust variable valve, but only the variable operation angle mechanism (VEL) is used as the exhaust variable valve. But it is possible.

  Although there are various technical ideas that can be grasped from the above-described embodiment, representative ones will be described below.

  (1) In the first explosion cylinder that performs combustion first in the expansion stroke at the start of starting, the first exhaust valve opening timing that comes after combustion is set to at least the initial piston position of the first explosion cylinder at the start of starting or at the last stop. Adjust based on information. According to this, by adjusting the exhaust valve opening timing based on the initial piston position of the first explosion cylinder, it is possible to make the combustion energy in the first explosion cylinder effectively act on the piston, thereby achieving good startability.

  (2) The initial piston position is detected when the internal combustion engine stops, and the exhaust valve opening timing is set to a predetermined position when the engine stops based on information on the initial piston position. According to this, since the desired exhaust valve opening timing is adjusted in advance based on the initial piston position immediately after the previous engine stop, the combustion energy in the first explosive cylinder is effectively applied to the piston from the beginning at the next automatic start. And good startability can be realized.

  (3) The initial piston position is detected when the engine is started, and the exhaust valve opening timing is adjusted based on the information on the initial piston position. According to this, based on the latest initial piston position information at the time of engine start, it is adjusted to a desired opening timing of the exhaust valve at the time of start, so that the combustion energy in the first explosion cylinder is effectively and accurately applied to the piston. Good startability can be realized. In addition, when correcting the desired opening timing of the exhaust valve in consideration of the engine temperature and the like in addition to the initial piston position information, the correction accuracy can be increased because the latest information is used.

  (4) As the initial piston position is closer to the top dead center (TDC), the exhaust valve opening timing is advanced. In other words, as the initial piston position is closer to the top dead center (TDC), the in-cylinder negative pressure tends to develop earlier in the latter half of the expansion stroke, and the work of the piston is suppressed. On the other hand, since the exhaust valve is opened earlier before the in-cylinder negative pressure develops, the in-cylinder pressure is maintained near the atmospheric pressure, the piston work is not reduced by the in-cylinder negative pressure, and combustion energy is effectively applied to the piston. Can be acted upon.

  (5) As the initial piston position moves away from the top dead center (TDC), the exhaust valve opening timing is retarded. In other words, as the initial piston position moves away from the top dead center (TDC), the timing at which the in-cylinder negative pressure develops in the latter half of the expansion stroke is delayed, and the in-cylinder combustion pressure is maintained at a high positive pressure, which opens the exhaust valve. After that, it escapes to the exhaust port side, and the combustion energy is not effectively applied to the piston. On the other hand, since the exhaust valve opening timing is retarded, it becomes difficult for the positive pressure combustion pressure to escape to the exhaust port side, and combustion energy can be effectively applied to the piston.

  (6) The retard conversion limit of the exhaust valve opening timing is near the bottom dead center (BDC). According to this, when the in-cylinder pressure is still positive even after the bottom dead center (BDC), the phenomenon of suppressing the rising operation of the piston can be prevented, and smooth engine operation can be realized, and the work of the piston is reduced accordingly. Can also be prevented.

  (7) The opening timing of the exhaust valve is corrected based on the engine temperature information at the time of starting, in addition to the information on the initial piston position of the first explosive cylinder at the start of starting or at the previous engine stop. According to this, the opening timing of the exhaust valve can be corrected in consideration of the fact that the in-cylinder volume expansion characteristic of the first explosive cylinder changes according to the engine temperature at the time of starting, so that more accurate starting can be realized.

  (8) The variable valve device is provided with an urging means for urging the exhaust valve opening timing to the advanced side. Due to the reaction force of the valve spring, the opening timing of the exhaust valve tends to be stabilized near the most retarded angle, and the responsiveness of the advance conversion of the opening timing of the exhaust valve at the start of startup tends to be poor. Since the urging means is urged to the advance angle side, responsiveness to the advance angle side at the start of starting or at the time of previous engine stop is increased, and good self-sustaining start can be realized without delay.

  As described above, according to the present invention, the opening timing of the first exhaust valve that is stopped after the combustion of the first explosive cylinder that performs the first combustion in the expansion stroke at the start of the start, at least at the start of the start or at the time of the previous engine stop In this configuration, adjustment is performed based on the initial piston position information of the first explosive cylinder.

  According to this configuration, even when the initial piston position of the first explosion cylinder is different, the gas pressure (combustion energy) of the first explosion cylinder can be effectively applied to the piston, and as a result, a good startability is obtained. Is what you can do.

  Note that the present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described above. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of one embodiment can be added to the configuration of another embodiment. Also, for a part of the configuration of each embodiment, it is possible to add, delete, or replace another configuration.

  01: cylinder block, 02: cylinder head, 03: piston, 04: combustion chamber, 05: spark plug, 06: connecting rod, 07: crankshaft, 08: pinion gear mechanism, 09: drive motor, 012: fuel injection valve 4, an intake valve; 5, an exhaust valve; 1, an exhaust VEL; 2, an exhaust VTC; 3, an intake VTC;

Claims (17)

A variable valve apparatus provided in an internal combustion engine having an intake valve and an exhaust valve, the variable valve mechanism including an exhaust-side variable valve mechanism for adjusting the valve timing of the exhaust valve and an intake-side variable valve mechanism for adjusting the valve timing of the intake valve. At
The exhaust-side variable valve mechanism is configured to inject fuel into a cylinder that is in an expansion stroke at the time of starting the internal combustion engine to perform combustion first, and to open after the combustion of an initial explosion cylinder. , An initial opening timing) is adjusted based on at least information on an initial piston position of the first explosive cylinder. The variable valve apparatus according to claim 1,
The exhaust-side variable valve mechanism sets the initial opening timing of the exhaust valve to a timing at which the in-cylinder pressure of the in-cylinder combustion chamber of the internal combustion engine becomes substantially atmospheric pressure. The variable valve device according to claim 2,
The exhaust-side variable valve mechanism detects the initial piston position when the internal combustion engine is stopped and, based on the information on the initial piston position, determines the initial opening timing of the exhaust valve when the internal combustion engine is stopped. A variable valve train characterized by adjusting. The variable valve device according to claim 2,
The exhaust-side variable valve mechanism detects the initial piston position when the internal combustion engine is started and, based on the information on the initial piston position, determines the initial opening timing of the exhaust valve when the internal combustion engine is started. A variable valve train characterized by adjusting. In the variable valve actuation device according to claim 3 or 4,
The variable valve mechanism according to claim 1, wherein the exhaust-side variable valve mechanism adjusts the initial opening timing of the exhaust valve to an advanced side as the initial piston position is closer to a top dead center. In the variable valve actuation device according to claim 3 or 4,
The variable valve operating apparatus according to claim 1, wherein the exhaust-side variable valve mechanism adjusts the initial opening timing of the exhaust valve to a retard side as the initial piston position moves away from top dead center. In the variable valve operating device according to claim 5 or 6,
The variable valve mechanism, wherein the exhaust side variable valve mechanism adjusts the initial opening timing of the exhaust valve by setting a retard side limit of the initial opening timing of the exhaust valve near bottom dead center. apparatus. The variable valve apparatus according to any one of claims 1 to 7,
The exhaust-side variable valve mechanism corrects the initial opening timing of the exhaust valve, which is obtained based on the information on the initial piston position, based on information on an engine temperature when the internal combustion engine is started. A variable valve operating device that adjusts an exhaust valve at the later initial opening timing of the exhaust valve. The variable valve device according to any one of claims 1 to 8,
The variable valve operating apparatus according to claim 1, wherein the exhaust-side variable valve mechanism includes an urging unit that urges the initial opening timing of the exhaust valve to an advanced side. The variable valve actuation device having an exhaust-side variable valve mechanism for adjusting a valve timing of an exhaust valve of an internal combustion engine and an intake-side variable valve mechanism for adjusting a valve timing of an intake valve of the internal combustion engine. In the controller of the variable valve operating device that controls the variable valve device,
The controller is configured to inject fuel into a cylinder in an expansion stroke at the time of starting the internal combustion engine to perform combustion first, and to open first after the combustion of an initial explosion cylinder. Information) is provided based on at least information on the initial piston position of the first explosive cylinder, and the obtained initial opening timing information of the exhaust valve is provided to the exhaust side variable valve mechanism. A controller for a variable valve operating device, wherein an initial opening timing of the exhaust valve is adjusted based on timing information. The controller of the variable valve device according to claim 10,
The controller of the variable valve device, wherein the controller sets the initial opening timing information of the exhaust valve to a timing at which the in-cylinder pressure of the in-cylinder combustion chamber of the internal combustion engine becomes substantially atmospheric pressure. The controller of the variable valve operating device according to claim 11,
The controller detects the initial piston position when the internal combustion engine is stopped, and obtains the initial opening timing information of the exhaust valve when the internal combustion engine is stopped, based on the information on the initial piston position. And the controller of the variable valve gear. The controller of the variable valve operating device according to claim 11,
The controller detects the initial piston position when the internal combustion engine is started, and obtains the initial opening timing information of the exhaust valve when starting the internal combustion engine based on the information on the initial piston position. And the controller of the variable valve gear. In the controller of the variable valve operating device according to claim 12 or 13,
The controller of the variable valve operating device, wherein the controller sets the initial opening timing information of the exhaust valve to an advanced side as the initial piston position is closer to the top dead center. In the controller of the variable valve operating device according to claim 12 or 13,
The controller of the variable valve operating device, wherein the controller sets the initial opening timing information of the exhaust valve to a retard side as the initial piston position moves away from the top dead center. In the controller of the variable valve operating device according to claim 14 or 15,
The controller of a variable valve operating device according to claim 1, wherein the controller sets the retard side limit of the initial opening timing of the exhaust valve near a bottom dead center to obtain the initial opening timing information of the exhaust valve. The controller of the variable valve operating device according to any one of claims 10 to 16,
The controller corrects the initial opening timing information of the exhaust valve obtained based on the information of the initial piston position based on information on an engine temperature at the time of starting the internal combustion engine, and corrects the exhaust gas after the correction. A controller for a variable valve operating device, wherein the initial opening timing of the valve is supplied to the exhaust side variable valve mechanism to adjust the initial opening timing of the exhaust valve.

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