JP2008133774A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance starting property by creating the ignitable state at an early stage while suppressing vibration in starting of an internal combustion engine in the internal combustion engine having a plurality of banks. <P>SOLUTION: The control device for the internal combustion engine provided with two groups of cylinders having a plurality of cylinders respectively is provided with an intake valve control means for variably controlling an opening/closing timing of intake valves of the respective cylinders of the two groups of cylinders. The control device firstly sets the opening/closing timing of the intake valve of the group of cylinders (hereinafter referred to as "specific group of cylinders") to which the cylinder (referred to as "specific cylinder") reaching the closing timing of the intake valve at a first opening/closing timing belongs to the first opening/closing timing after starting of the internal combustion engine. Further, the control device sets the opening/closing timing of the intake valves of the group of cylinders different from the specific group of cylinders to the second opening/closing timing in starting of the internal combustion engine. At this time, the first opening/closing timing is an opening/closing timing when an amount of gas sucked into the cylinder when the intake valve is controlled to the first opening/closing timing becomes smaller than an amount of gas sucked into the cylinder when it is controlled to the second opening/closing timing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine. More specifically, the present invention relates to a control device for an internal combustion engine that includes two cylinder groups in which a plurality of cylinders are arranged and that can variably control the opening / closing timing of an intake valve for each cylinder group.

  Japanese Patent Application Laid-Open No. 2004-293556 discloses a control device for an internal combustion engine that includes a pair of left and right banks (cylinder group) each including three cylinders. This device has a variable valve timing mechanism that changes the operation timing of the intake and exhaust valves for each bank. In addition, this device includes a hybrid drive device for a vehicle connected to an internal combustion engine and an electric motor in a power transmission mechanism connected to drive wheels. With this hybrid drive device, for example, when the vehicle is traveling at a reduced speed or during braking, the kinetic energy of the vehicle is converted into electric energy by an electric motor and recovered (regenerative braking). On the other hand, when the vehicle starts, high startability is ensured by rotating the electric motor by electric energy and outputting the assist torque.

  By the way, during the regenerative braking as described above, the regenerative amount can be increased by reducing the pump loss in the compression stroke of the internal combustion engine. For this reason, in the above-described conventional device, when the regenerative braking is being performed, the internal combustion engine of the vehicle is in the stop mode, and there is a possibility of regeneration of the internal combustion engine, the cylinders in one bank are set to the decompressed state. That is, by setting the intake valve or the exhaust valve to be open during the compression stroke by the valve timing mechanism, the gas in the cylinder in the compression stroke is not compressed. Thereby, the pump loss in the compression stroke is reduced. As a result, the regeneration amount is increased. At this time, the other bank is operated in a compression state. Therefore, when a request for restarting the internal combustion engine is issued, a state in which the internal combustion engine can be restarted immediately in response to the request is secured.

JP 2004-293556 A

  By the way, as described above, the pressure in the cylinder in the compression stroke can be reduced by maintaining the intake valve in the open state in the compression stroke and setting the decompression state. In particular, when the internal combustion engine is started, if the compression pressure in the cylinder in the compression stroke increases, a large vibration occurs due to the reaction force of the compression. Therefore, in order to suppress the vibration at the start of the internal combustion engine to be small, it is effective to put the cylinder in the compression stroke into the decompressed state by delaying the closing timing of the intake valve at the start.

  On the other hand, by delaying the opening timing of the intake valve and utilizing the negative pressure generated in the cylinder due to the lowering of the piston, the pump loss is increased, and the heat for the loss provides a sufficient amount of air for ignition. While securing, the temperature in the cylinder can be increased by intake air. Also, by closing the intake valve at the bottom dead center (compression BDC) at the start of the compression stroke of the intake valve, the air-fuel mixture filled at a high filling rate in the cylinder is compressed at a high compression ratio. The temperature in the cylinder can be increased by adiabatic compression. Therefore, in the low temperature and low rotation range at the time of starting, the opening timing of the intake valve is delayed and the valve is closed in the vicinity of the compression BDC, so that ignition is reliably performed and the startability can be improved.

  However, in order to suppress the vibration at the start of the internal combustion engine, the intake valve is controlled to the top dead center (compression TDC) near the end of the compression stroke in order to bring the cylinder into a decompressed state by controlling the intake valve timing. It is necessary to keep the valve open. Therefore, when the valve opening characteristics of the intake valve are not controlled individually as in the case of electromagnetically driven valves, but are controlled mechanically in conjunction with each other, the intake valve is controlled to be closed slowly in a certain cylinder. If the decompressed state is ensured in this way, in the cylinder in which the ignition sequence continues, the intake valve may be opened at the opening / closing timing for the decompressed state and reach the compression BDC in some cases. Therefore, it is difficult to immediately control the cylinder immediately after that to the optimum intake valve timing for ignition after being controlled to be in a decompressed state in the immediately preceding cylinder. However, in order to improve the startability of the internal combustion engine, it is preferable that the engine can be ignited immediately after starting in the decompressed state.

  However, especially when the number of cylinders increases, the ignition interval of each cylinder decreases. Accordingly, the valve timing phase difference between the front and rear cylinders is reduced. For this reason, it is more difficult to smoothly and quickly switch between control of vibration suppression at start-up in the decompressed state and control of valve timing for ignition.

  The present invention has been made to solve the above-described problems, and at the time of starting an internal combustion engine, it is possible to immediately realize optimal valve timing of ignition while suppressing the vibration while realizing the start in the decompressed state. An object of the present invention is to provide an internal combustion engine control apparatus improved to improve startability.

In order to achieve the above object, a first invention is a control device for an internal combustion engine comprising two cylinder groups each having a plurality of cylinders,
Intake valve control means for variably controlling the opening / closing timing of the intake valve of each cylinder of the two cylinder groups for the same cylinder group;
First, after the internal combustion engine is started, the opening / closing timing of the intake valve of the cylinder group (hereinafter referred to as “specific cylinder group”) to which the cylinder (hereinafter referred to as “specific cylinder group”) reaches the closing timing of the intake valve at the first opening / closing timing. A first opening / closing timing setting means for setting the first opening / closing timing; and a second opening / closing timing for setting an opening / closing timing of an intake valve of a cylinder group different from the specific cylinder group to a second opening / closing timing when the internal combustion engine is started. Timing setting means;
With
The first opening / closing timing includes an amount of gas sucked into the cylinder when the intake valve is controlled to the first opening / closing timing, and an amount of gas sucked into the cylinder when the intake valve is controlled to the second opening / closing timing. The opening / closing timing is smaller than that.

  In a second aspect based on the first aspect, the second opening / closing timing is such that the cylinder temperature controlled at the second opening / closing timing has a higher in-cylinder temperature than the cylinder controlled at the first opening / closing timing. The open / close timing is characteristic.

According to a third invention, in the first or second invention,
The first opening / closing timing is a timing for opening the intake valve in the vicinity of the top dead center and closing the intake valve in the latter half of the compression stroke,
The second opening / closing timing is a timing at which the intake valve is opened on the retard side from the top dead center and the intake valve is closed near the bottom dead center.

According to a fourth invention, in any one of the first to third inventions,
A valve closing detecting means for detecting an initial valve closing of the intake valve of the specific cylinder at the time of starting the internal combustion engine;
Switching means for switching the opening / closing timing of the intake valve of the specific cylinder group to the second opening / closing timing when the first closing of the intake valve of the specific cylinder is detected;
It is characterized by providing.

A fifth invention is the fourth invention,
Specific cylinder determining means for determining the specific cylinder such that two or more cylinders whose ignition sequence continues immediately after the specific cylinder are included in a cylinder group different from the specific cylinder group;
Start start position control means for controlling the start start position of the piston of the specific cylinder so that the determined specific cylinder first reaches the valve closing timing of the first opening / closing timing when the internal combustion engine is started;
It is characterized by providing.

A sixth invention is the fourth or fifth invention, wherein
Specific cylinder determining means for determining the specific cylinder such that a cylinder whose ignition order is immediately before the specific cylinder is included in a cylinder group different from the specific cylinder group;
Stop position control means for controlling the stop position of the piston of the cylinder whose ignition order is immediately before the specific cylinder when the internal combustion engine is stopped to a position corresponding to the valve opening timing of the first opening / closing timing;
It is characterized by providing.

  According to the first aspect of the present invention, when the internal combustion engine is started, the intake valve opening / closing timing of the specific cylinder group to which the specific cylinder first reached after the internal combustion engine starts corresponds to the closing timing of the intake valve at the first opening / closing timing. The first opening / closing timing is set, and the opening / closing timing of the intake valve of the other cylinder group is set to the second opening / closing timing. Here, the first opening / closing timing is greater than the amount of gas sucked into the cylinder when the intake valve is controlled at this timing, and the amount of gas sucked into the cylinder when controlled at the second opening / closing timing. The opening / closing timing becomes smaller. In this manner, the vibration at the start of the internal combustion engine can be suppressed by closing the cylinder in which the intake valve is initially closed at the time of starting at the timing when the gas amount is reduced. In addition, since the cylinder group different from the specific cylinder group is set to the opening / closing timing at which the gas amount increases, the timing at which the gas amount in the cylinder increases immediately after starting with a small gas amount is started. This can improve the startability of the internal combustion engine.

  According to the second invention, the second opening / closing timing may be an opening / closing timing such that the cylinder controlled at the second opening / closing timing has a higher in-cylinder temperature than the cylinder controlled at the first opening / closing timing. it can. Thereby, the startability of an internal combustion engine can be improved more reliably.

  According to the third aspect of the invention, the first opening / closing timing is a timing at which the intake valve is opened near the top dead center and the intake valve is closed at the latter half of the compression stroke, and the second opening / closing timing is on the retard side from the top dead center. The timing for opening the intake valve and closing the intake valve near the bottom dead center. Thereby, after starting the engine in a state where the gas amount is small, it is possible to immediately switch to the timing at which the gas amount in the cylinder becomes large, and the startability of the internal combustion engine can be improved.

  According to the fourth invention, when the intake valve of the specific cylinder is closed, the opening / closing timing of the intake valve of the specific cylinder group is switched to the second opening / closing timing. In addition, the intake valves of the cylinder group different from the specific cylinder group from the start are set to the second opening / closing timing. Therefore, it is possible to perform control at the second opening / closing timing with a large intake air amount immediately after starting while suppressing vibrations in a state where the compressed gas amount is small, and it is possible to ensure high startability.

  According to the fifth aspect, the specific cylinder is determined such that the two or more cylinders whose ignition order continues immediately after the specific cylinder belong to a cylinder group different from the specific cylinder group. However, when starting the internal combustion engine, the starting start position of the piston of the specific cylinder is controlled so that the valve closing timing of the first opening / closing timing is reached first. Thereby, when the ignition order does not alternate between the two cylinder groups and the ignition interval in the cylinder group is not constant, the timing at which the ignition interval in the specific cylinder group becomes long, Switching from the first opening / closing timing to the second opening / closing timing can be performed reliably.

  According to the sixth invention, the specific cylinder is determined such that the cylinder group different from the specific cylinder group includes the cylinder whose ignition order is immediately before the specific cylinder, and the ignition order is the specific cylinder when the internal combustion engine is stopped. The stop position of the piston of the cylinder immediately before is controlled so as to correspond to the valve opening timing of the first opening / closing timing. As a result, when the internal combustion engine is started, the cylinder whose ignition sequence is immediately before the specific cylinder can be started from the compression stroke and the amount of compressed gas can be reduced. Therefore, it is possible to start the internal combustion engine while suppressing vibration more reliably.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Embodiment 1 FIG.
[System configuration of the first embodiment]
FIG. 1 is a schematic diagram for explaining the overall configuration of an internal combustion engine on which the control apparatus according to Embodiment 1 of the present invention is mounted and its surrounding system. FIG. 2 is a schematic diagram for explaining the arrangement of the cylinders of the internal combustion engine. The system shown in FIG. 1 includes an internal combustion engine 10. The internal combustion engine 10 actually includes a first bank 12 (cylinder group) and a second bank 14 (cylinder group), as will be described later. The first and second banks 12 and 14 each include a plurality of cylinders 1 to In FIG. 1, only a cross section of one cylinder of one bank is illustrated in FIG.

  A piston 20 is disposed inside the cylinders 1-6. The piston 20 is connected to a crankshaft (not shown) via a connecting rod 22. In the vicinity of the crankshaft, a rotational speed sensor 24 that emits an output corresponding to the rotational speed is disposed. A combustion chamber 26 is provided in the upper part of the piston 20. A spark plug 28 is inserted into the combustion chamber 26 so that the tip portion protrudes. The internal combustion engine 10 includes an intake port 30 and an exhaust port 32 that communicate with the combustion chamber 26.

  As shown in FIG. 2, the internal combustion engine 10 has six cylinders 1 to 6. The cylinder 1, the cylinder 2, and the cylinder 3 are arranged in series in order, and constitute a first bank 12. On the other hand, the cylinder 4, the cylinder 5, and the cylinder 6 are arranged in series in order, and constitute a second bank 14. The internal combustion engine 10 is configured by connecting the first bank 12 and the second bank 14 thus configured in parallel.

  A common intake manifold 34 is communicated with the intake ports 30 of the cylinders 1 to 3 of the first bank 12, and a common intake manifold 36 is connected to the intake ports 30 of the cylinders 4 to 6 of the second bank 14. It is communicated. Specifically, the intake manifold 34 has four branch pipes 34a communicating with each of the intake ports 30 of the cylinders 1 to 3 of the first bank 12, and one branch pipe 34a connected together. And a main pipe 34b. Similarly, the intake manifold 36 has three branch pipes 36a communicating with the respective intake ports 30 of the cylinders 4 to 6 of the second bank 14 and one branch pipe 36a connected together. Main pipe 36b.

  Although not shown in FIG. 2, similar to the intake port 30 side, the exhaust ports 32 of the cylinders 1 to 3 and the cylinders 4 to 6 have an exhaust common to the first and second banks 12 and 14, respectively. The manifold is in communication.

  Referring to FIG. 1 again, the internal combustion engine 10 includes an intake valve 40 (intake valve) that opens and closes the intake port 30 in each of the intake ports 30 of the cylinders 1 to 6. An intake valve shaft 42 is fixed to the intake valve 40. A valve lifter 44 is attached to the upper end portion of the intake valve shaft 42. The urging force of the valve spring 46 acts on the intake valve shaft 42, and the intake valve 40 is urged in the valve closing direction by the urging force. An intake cam 50 is disposed above the valve lifter 44. The intake cams 50 of the cylinders 1 to 3 and 4 to 6 are connected to the same camshaft (not shown) for each of the same banks 12 and 14. The same variable valve mechanism 52 (intake valve control means) is connected to the intake cam 50 for each bank through the camshaft and the like. A cam position sensor 54 is attached near the camshaft of the intake cam 50. The cam position sensor 54 outputs an output corresponding to the rotation angle and the rotation speed of the cam.

  The variable valve mechanism 52 of the intake valve 40 controls the rotation of the intake cam 50 by controlling the rotation of the camshaft. As a result, the phase, operating angle, and lift amount of each intake valve 40 can be changed independently for each of the first and second banks 12 and 14.

  Similarly, the internal combustion engine 10 includes an exhaust valve 60 that opens and closes the exhaust port 32 in each of the exhaust ports 32 of the cylinders 1 to 6. The exhaust valve 60 has the same configuration as the intake valve 40. That is, an exhaust valve shaft 62 fixed to the exhaust valve 60, a valve lifter 64 attached to the upper portion of the exhaust valve shaft 62, and a valve spring 66 attached to urge the exhaust valve shaft 62 in the valve closing direction are provided. ing. An exhaust cam 70 is disposed on the valve lifter 64. The exhaust cams 70 of the cylinders 1 to 6 are connected to the same camshaft (not shown) for each of the banks 12 and 14, and the same possible for each of the same banks 12 and 14 via the camshaft and the like. A variable valve mechanism 72 is connected. A cam position sensor 74 is attached in the vicinity of the cam shaft of the exhaust cam 70. The cam position sensor 74 generates an output corresponding to the rotation angle and the rotation speed of the exhaust cam 70.

  The variable valve mechanism 72 on the exhaust valve 60 side controls the rotation of the exhaust cam 70 by controlling the rotation of the camshaft. As a result, the phase, operating angle, and lift amount of the exhaust valve 60 can be changed independently for each of the banks 12 and 14.

  The timing of opening and closing of the intake / exhaust valves 40, 60 can be changed by changing the phases of the intake / exhaust valves 40, 60. The valve opening period of the intake / exhaust valves 40, 60 can be changed by changing the operating angle. Further, the size of the passage formed between the intake / exhaust ports 30 and 32 when the intake / exhaust valves 40 and 60 are opened can be changed due to the change in the lift amount. Further, such control can be performed independently and independently in the cylinders 1 to 3 and the cylinders 4 to 6 of the banks 12 and 14. Note that the mechanism for controlling the phase, operating angle, and lift amount of the intake valve 40 or the exhaust valve 60 by controlling the rotation of the camshaft is not particularly new, and therefore detailed description thereof is omitted here. To do.

  The internal combustion engine 10 includes an ECU (Electronic Control Unit) 80 as a control device for the internal combustion engine. The ECU 80 acquires information necessary for controlling the internal combustion engine 10 from various sensors such as the rotation speed sensor 26 and the cam position sensors 54 and 74. Further, the ignition plug 28 and the variable valve mechanisms 52 and 72 are controlled based on the acquired information.

[Valve timing of internal combustion engine]
FIG. 3 is a valve timing diagram for illustrating the opening / closing timing of intake valve 40 when the internal combustion engine according to the first embodiment of the present invention is started. In FIG. 3, (1) represents the valve opening period of the intake valve when the pressure in the cylinder in the compression stroke is small (hereinafter referred to as “decompression state”), and IVO (1) and IVC (1) are The position of the piston 20 with respect to the valve opening timing and the valve closing timing of the intake valve 40 in this case is shown, respectively. Further, (2) represents the opening period of the intake valve that is optimal for ignition at the time of starting, and IVO (2) and IVC (2) are the opening timing and closing timing of the intake valve 40 in this case, respectively. Represents the position of the piston 20 relative to.

  At the start of cranking of the internal combustion engine 10, as shown in FIG. 3 (1), the intake valve 40 is in a TDC (Top Dead Center: hereinafter referred to as “intake TDC”) in which the piston 20 of the cylinder starts the intake stroke. It is opened at a timing at a position IVO (1) after a certain position. Thereafter, the piston 20 passes through a BDC (Bottom Dead Center: hereinafter referred to as “compressed BDC”) at the start of the compression stroke, and a position IVC (slightly before a TDC at the end of the compression stroke (hereinafter referred to as “compression TDC”). The intake valve 40 is closed at the timing 1).

  Here, while the piston 20 moves from IVO (1) to IVC (1), the intake valve 40 is kept open. While the intake valve 40 is open, even if the piston 20 starts to rise beyond the compression BDC, the gas filled in the cylinder is not compressed and pushed out to the intake port 30 side. . Therefore, until the valve closing timing IVC (1) of the intake valve 40, the piston 20 rises in a state where the gas in the cylinder is not compressed. Therefore, by adopting the valve timing of the intake valve shown in (1) of FIG. 3, the inside of the cylinder can be in a decompressed state and the compression pressure can be reduced.

  In particular, at the start of cranking of the internal combustion engine 10, if the compression pressure in the compression stroke increases, the engine rotation speed changes due to the compression stress, and large vibrations are likely to occur. However, immediately after the start of the internal combustion engine 10, among the cylinders 1 to 6, for the cylinder (specific cylinder) in the compression stroke, the valve timing of the intake valve of (1) in FIG. By doing so, it is possible to suppress the occurrence of vibration immediately after the internal combustion engine 10 is started.

  On the other hand, (2) in FIG. 3 represents the opening / closing timing of the intake valve 40 that is optimal for ignition at the time of starting. In the case of (2) in FIG. 3, the intake valve 40 is opened at a timing at which the piston 20 is at a position IVO (2) further ahead of the piston position IVO (1) when the piston 20 exceeds the intake TDC and is in a decompressed state. The Until the intake valve 40 is opened, the piston 20 descends while the inside of the cylinder is sealed, so the negative pressure in the cylinder increases. In this state, when the piston 20 reaches IVO (2) and the intake valve 40 is opened, the pump loss increases, and the temperature in the cylinder rises due to the heat of the loss.

  The intake valve 40 is closed at a timing when the piston 20 is at a position IVC (2) near the compression BDC. Therefore, in the subsequent compression stroke, the gas filled in the cylinder at a high filling rate can be compressed at a high compression ratio without flowing out to the intake port 30 or the exhaust port 32 side. Accordingly, it is possible to secure a sufficient amount of air for ignition in the cylinder and to increase the temperature in the cylinder by the adiabatic compression effect, and to increase the in-cylinder temperature at the start.

  When the internal combustion engine 10 is started, there is a case where ignition cannot be performed stably immediately after the start of the engine because the temperature in the cylinder is particularly low. However, by adopting the opening / closing timing of the intake valve 40 as shown in FIG. 3 (2), the temperature in the cylinder can be raised. Accordingly, it is possible to reliably start ignition and generate a necessary torque at an early stage when the internal combustion engine is started.

  Hereinafter, in the embodiment, the valve timing of the intake valve 40 that brings the cylinder in the compression stroke as shown in (1) of FIG. 3 into the decompressed state is referred to as “decompression timing” (first opening / closing timing). The valve timing when ignition is performed when the internal combustion engine 10 is started as in (2) is referred to as “start timing fire timing” (second opening / closing timing).

[Characteristic control of the first embodiment]
When the internal combustion engine 10 is started, the cylinder in the compression stroke is in a decompressed state so that vibration due to compressive stress is suppressed, the decompression timing is adopted, the generation of vibration is suppressed, and cranking is started earlier. It is desirable to employ the starting timing in order to perform reliable ignition to generate the required torque. Therefore, for example, the intake valve 40 of the cylinder in the first compression stroke immediately after the start of the start is set to the decompression timing, and the cylinder at the compression stroke after that is set to the ignition timing at the start in order to realize ignition. preferable.

  FIG. 4 is a diagram for explaining the order of ignition of the cylinders 1 to 6 and the phase difference of the cylinders 1 to 6 of the internal combustion engine 10. As shown in FIG. 4, the ignition order of the internal combustion engine 10 of the first embodiment is cylinder 1, cylinder 4, cylinder 2, cylinder 5, cylinder 3, and cylinder 6. The phase difference between cylinders with adjacent ignition orders is equal. That is, since one combustion cycle is 720 degrees in crank angle, the phase difference between two cylinders in which the ignition sequence is continuous is 120 degrees. Further, when viewed for each of the first bank 12 and the second bank 14, the ignition interval in each bank 12, 14 is also equal, and the phase difference between the cylinders in which the ignition sequence is continuous is 240 degrees.

  FIG. 4 shows an example in which the cylinder (specific cylinder) that is in the compression stroke first and reaches IVC (1) first immediately after the start of the internal combustion engine 10 is the cylinder 1. IVC (1) is the timing perceived by the compressed BDC. Here, when the piston 20 of the cylinder 1 is at a position A1 from the compression BDC at the start of the start of the internal combustion engine 10, and the intake valve 40 of the cylinder 1 is controlled at the decompression timing, the piston 20 moves to IVC (1). The intake valve 40 is closed. In this case, since the cylinder 4 that is ignited following the cylinder 1 is retarded in phase by 120 degrees from the cylinder 1, the piston 20 of the cylinder 4 is compressed from the position A4 close to the compression BDC in the latter half of the intake stroke. Move to BDC position IVC (2). Similarly, since the cylinder 2 to be ignited next has a delay angle of 120 degrees, the piston 20 of the cylinder 2 moves from the position A2 of the intake TDC to the position IVO (1).

  That is, when the piston 20 of the cylinder 1 reaches IVC (1), the piston 20 of the cylinder 4 is at the position IVC (2) corresponding to the valve closing timing of the start timing fire timing. Therefore, after the cylinder 1 in the compression stroke is controlled at the decompression timing, if the next cylinder 4 in the compression stroke is immediately switched to the start timing, the intake valve 40 of the cylinder 4 needs to be closed simultaneously with the switching. is there. However, considering the time lag due to actuator operation or the like, it is difficult to close the intake valve 40 at the same time as switching the valve timing. Therefore, it is difficult to switch from the decompression timing control to the start timing fire timing control between the cylinder 1 and the cylinder 4 in which the ignition order is continuous.

  This is the same even when a cylinder other than the cylinder 1 is in the first compression stroke. That is, since the phase difference between the cylinders that are continuously ignited is 120 degrees, in a state where the piston 20 of the cylinder that is ignited immediately before has reached the position IVC (1) corresponding to the valve closing timing of the decompression timing, The piston 20 of the cylinder to be ignited next has reached a position corresponding to the valve closing timing IVC (2) of the starting timing. Therefore, it is difficult to realize the decompression timing in the previous cylinder and immediately switch from the immediately following cylinder to the start timing fire timing.

  Therefore, in the first embodiment, the first bank 12 and the second bank 14 are set so that the valve timing of the intake valve 40 at the time of starting is different. Specifically, immediately after the start of the internal combustion engine 10, the intake valve 40 of the bank (specific cylinder group) to which the cylinder in the compression stroke first belongs is set to the decompression timing, and the intake valve 40 of the other bank is set to the decompression timing. Set to the starting fire timing.

  FIG. 5 is a diagram for explaining the ignition sequence and valve timing of each cylinder when the internal combustion engine according to Embodiment 1 of the present invention is started. FIG. 5 (A) is a diagram illustrating ignition of each cylinder of the internal combustion engine 10. FIG. 5B shows an example of the valve timing when the internal combustion engine is stopped, and FIG. 5C shows an example of control of the valve timing when the internal combustion engine is started.

  In the ignition sequence shown in FIG. 5A, when it is determined that the piston 20 of the cylinder 1 first passes IVC (1) of the compression stroke at the next start of the internal combustion engine 10, it is shown in FIG. 5B. Thus, first, the first bank 12 side is set to the decompression timing, and the second bank 14 side is set to the start timing. In FIG. 5, “de” indicates the decompression timing, and “dot” indicates the start timing fire timing.

  When the internal combustion engine 10 is started, in the first compression stroke, the intake valves of the cylinders 1 to 6 are controlled in a state set as shown in FIG. That is, the cylinders 1 to 3 in the first bank 12 start cranking at the decompression timing, and the cylinders 4 to 6 in the second bank 14 start cranking at the start-up fire timing. After that, when the piston 20 of the cylinder 1 that first passes through the compression stroke IVC (1) reaches IVC (1) and the intake valve 40 is closed, the valve timing on the first bank 12 side is as shown in FIG. As shown in C), the start timing is switched to the fire timing.

  FIGS. 6 to 9 illustrate specific examples of the relationship between the intake valve timing and the piston position of each cylinder 1 to 6 when the apparatus of the first embodiment performs the above-described control at the start of the internal combustion engine. FIG. 6 to 9 show an example in which the cylinder that first passes IVC (1) at the start of the internal combustion engine is the cylinder 1. FIG. In each figure, the cylinders are arranged in the order of ignition from the top row, and the change in the position of the piston 20 and the intake valve timing of the cylinder in the row after the start in the horizontal direction is shown.

  FIG. 6 shows an example in which when the internal combustion engine 10 is started, the stop position of the piston 20 of the cylinder 1 exceeds the compression BDC and is at a position A1 slightly before the middle of the compression stroke. When cranking of the internal combustion engine 10 starts in this state, the piston 20 of the cylinder 1 reaches the position IVC (1) with the intake valve 40 still open. That is, since the cylinder 1 is in the compression stroke in the decompressed state, the stress due to this compression is small, and the occurrence of vibration is suppressed by the compression immediately after starting. When the piston 20 of the cylinder 1 reaches the position IVC (1), the intake valve 40 of the cylinder 1 is closed.

  During this time, the piston 20 of the cylinder 4 following the cylinder 1 moves from the position A4 slightly advanced from the middle of the intake stroke to the position IVC (2) of the compression BDC. The cylinder 4 is a cylinder belonging to the second bank 14 and is controlled to the start timing fire timing from the start. Accordingly, when the piston 20 moves to IVC (2), the intake valve 40 is closed.

  The piston 20 of the cylinder 2 following the cylinder 4 moves from the position A2 of the intake TDC to the position IVO (1). IVO (1) is the timing delayed by 60 degrees from the intake TDC. Since the cylinder 4 belongs to the first bank 12 and is controlled at the decompression timing, the intake valve 40 of the cylinder 2 is opened at this time. Since the cylinder 5, the cylinder 3 and the cylinder 6 are in the expansion or exhaust stroke during this period, the valve timing of the intake valve 40 at the time of starting is kept closed.

  After the compression of the cylinder 1 in the decompressed state is completed and the intake valve 40 is closed, the cylinder 4 enters the compression stroke, and the piston 20 rises from the position B4 of the compression BDC. The cylinder 4 is controlled at the start timing, and the intake valve 40 is already closed in the compression BDC. Accordingly, the gas in the cylinder 4 is sufficiently compressed, the temperature in the cylinder rises due to the adiabatic compression effect, and the ignition can be started from the fourth cylinder.

  In the cylinder 2 following the cylinder 4, the valve timing of the intake valve 40 is switched to the start timing when the piston 20 reaches IVC (2) while the piston 20 is lowered while the intake valve 40 is open. . Therefore, while the cylinder 4 is in the compression stroke, the intake of the cylinder 2 is continued with the intake valve 40 opened, and the intake valve 40 is closed when reaching the IVC (2). Thereafter, the cylinder 2 enters the compression stroke, and the piston 20 of the cylinder 2 rises from the position of the compression BDC. Cylinder 2 has been switched to the starting fire timing. Therefore, the gas in the cylinder 2 is sufficiently compressed without flowing out to the intake port 30 side, and can be ignited.

  Subsequently, the cylinder 5, the cylinder 3, and the cylinder 6 are compressed and ignited after the cylinder 2, but the first bank 12 side has already been switched to the start timing. Therefore, until the completion of the start of the internal combustion engine 10 is recognized, the intake valves 40 of all the cylinders 1 to 6 are controlled at the start-up fire timing, and an optimal air amount is secured at the start while raising the in-cylinder temperature. Can be ignited.

  FIG. 7 shows an example in which the stop position of the piston 20 of the cylinder 1 is closer to the compression TDC than in the case of FIG. In the case of FIG. 7, the piston 20 of the cylinder 1 is set so that the valve timing of the first bank 12 becomes the decompression timing in a state where the piston 20 is stopped at the position A1 near the midpoint of the compression stroke. Therefore, when the start of the internal combustion engine 10 is started, in the cylinder 1, the piston 20 rises from the position A1 to IVC (1) with the intake valve 40 opened, so the first compression stroke at the start is performed in the decompressed state. Will be.

  During this time, the piston 20 of the cylinder 4 moves from a position A4 slightly before the compression BDC to IVC (2) (compression BDC). Since the cylinder 4 is controlled at the optimal ignition timing, the intake valve 40 is closed when the piston 20 reaches IVC (2). Thereafter, the cylinder 4 enters a compression stroke, and ignition is performed in a state where the inside of the cylinder 4 is sufficiently compressed and the in-cylinder temperature rises. However, in this case, since the piston 20 of the cylinder 4 starts from a position slightly before the compression BDC at which the intake stroke ends, there is no effect of the temperature rise in the cylinder 4 due to the slow opening of the intake valve 40.

  After starting, until the piston 20 of the cylinder 1 reaches IVC (1), the piston 20 of the cylinder 2 moves from the position A2 slightly ahead of the intake TDC to the IVO (1). The valve 40 is opened. When the intake valve 40 of the first cylinder is closed, the valve timing on the first bank 12 side is switched from the decompression timing to the start timing fire timing. In the cylinder 2, the valve timing is switched to the start timing fire timing while the intake valve 40 remains open, and when the piston 20 descends to IVC (2) (compression BDC), the intake valve 40 is closed. Accordingly, in the subsequent compression stroke, the gas in the cylinder 2 is sufficiently compressed and ignition is performed.

  FIG. 8 shows an example in which the piston 20 of the cylinder 1 is at a position A1 close to the compression BDC when the internal combustion engine 10 is started. When starting the internal combustion engine 10, the cylinder 1 is set to decompression timing. Therefore, the intake valve 40 is in the open state until the start of the internal combustion engine 10 and the piston 20 of the cylinder 1 reaches IVC (1). Thereby, the vibration in the first compression stroke at the time of starting is suppressed.

  In the case of FIG. 8, the piston 20 of the cylinder 4 following the cylinder 1 is stopped at a position advanced from IVO (2) at the time of starting. Accordingly, when starting of the internal combustion engine 10 is started, the piston 20 descends and moves to IVC (2) with the intake valve 40 opened, and the intake valve 40 is closed.

  In the case of FIG. 8, the piston 20 of the cylinder 2 is at a position A2 near the end of the exhaust stroke at the start, and before the piston 20 of the cylinder 1 moves to IVC (1), the piston 20 from the exhaust stroke to the intake stroke. Entering IVO (2), the intake valve 40 is opened. Thereafter, the valve timing of the first bank 12 is switched to the start timing, and when the piston 20 of the cylinder 2 reaches IVC (2), the intake valve 40 is closed. Thereafter, all the cylinders 1 to 6 are controlled at the start timing.

  FIG. 9 shows an example in which the piston 20 of the cylinder 1 is in compression BDC when the internal combustion engine 10 is started. As shown in FIG. 9, similarly, when the piston 20 of the cylinder 1 is in the compression BDC, the compression stroke is performed in the cylinder 1 in the decompressed state, and the intake valve 40 is closed when the piston 20 reaches IVC (1). To do.

  During this time, since the cylinder 4 is set to the start timing, the intake valve 40 is opened when the piston 20 reaches IVO (2) after the start of the internal combustion engine 10 is started. Thereafter, when the cylinder 1 reaches IVC (1), the piston 20 of the cylinder 4 reaches IVC (2), and the intake valve 40 is closed. In this case, in the cylinder 4, the piston 20 starts to descend from the state in which the intake valve 40 is closed. Therefore, the pump loss in the intake stroke increases, and intake is performed with a strong force due to the negative pressure in the cylinder 4. For this reason, the temperature rise in the cylinder 4 can be achieved more efficiently, the cylinder 4 can be brought into a state suitable for ignition, and ignition from the second compression at the start can be performed more reliably. However, this effect is not obtained if the piston stop position of the cylinder 4 at the start of the start is the same as that of IVO (2).

  The subsequent cylinder 2 is near the end of the exhaust stroke when the internal combustion engine 10 is started. The piston 20 of the cylinder 2 enters the intake stroke from the exhaust stroke and moves to IVO (1) until the piston 20 of the cylinder 1 moves to IVC (1). Here, the intake valve 40 opens. Thereafter, intake is performed with the intake valve 40 open, and the intake valve timing is switched to the start-up timing at that time. When the piston 20 of the cylinder 2 reaches IVC (2), the intake valve 40 is closed and the compression stroke is started. In the case shown in FIG. 9, the piston 20 of the cylinder 6 is near the end of the compression stroke when the internal combustion engine 10 is started. Accordingly, the cylinder 6 is compressed in the decompressed state, and the compression pressure becomes small. Therefore, even if the cylinder 6 is started normally, it does not cause vibration.

  As described above with reference to FIGS. 6 to 9, after the start of the internal combustion engine 10, the intake valve timing of the cylinder 1 that first passes IVC (1) is set to the decompression timing, and the intake valve 40 of the cylinder 1 After the valve is closed in the IVC (1), the valve timing of the first bank 12 is switched so as to be the start timing fire timing. During this switching, the cylinder 4 in the second bank 14 enters the compression stroke following the cylinder 1. However, the second bank 14 is set to the start timing fire from the start, and the cylinder 4 is controlled at the start timing. Therefore, in the cranking immediately after the start, after the compression stroke of the cylinder 1 is performed in the decompressed state, the cylinder 4 is immediately controlled at the start timing fire timing and the compression stroke is performed. Thereafter, the first bank 12 is switched to the start timing, and the compression stroke of the cylinder 2 is performed. Therefore, ignition from the second compression can be performed while starting the engine while suppressing vibration in the decompressed state, and the startability can be improved.

[Regarding control routine in the first embodiment]
FIG. 10 is a flowchart for illustrating a control routine executed by ECU 80 in the first embodiment of the present invention. The routine of FIG. 10 is a routine that is executed every time the internal combustion engine 10 is stopped. In the routine of FIG. 10, it is first determined whether or not a stop command for the internal combustion engine 10 has been issued (S102). If the stop command for the internal combustion engine 10 is not accepted, the process is terminated.

  On the other hand, if a stop command for the internal combustion engine 10 is detected in step S102, then the current crank angle of the internal combustion engine is detected (S104). The crank angle is obtained based on the output of the rotation speed sensor 26 arranged in the vicinity of the crankshaft of the internal combustion engine 10.

  Next, when the internal combustion engine 10 is next started, the cylinder (specific cylinder) in which the piston 20 first passes IVC (1) is specified (S106). This cylinder is identified by determining the position of each cylinder when it is stopped from the current crank angle.

  Next, of the first bank 12 and the second bank 14, the valve timing of the intake valve 40 of the bank (specific cylinder group) to which the cylinder specified in step S106 belongs is set to the decompression timing, and the intake of the other bank The valve timing of the valve 40 is set to be the start timing fire timing (S108). Thereafter, the internal combustion engine 10 is stopped (S110), and this process ends.

  FIG. 11 is a flowchart for illustrating a control routine executed by ECU 80 when starting internal combustion engine 10 in the first embodiment of the present invention. In the routine of FIG. 11, it is detected whether or not a command for starting the internal combustion engine 10 has been issued (S120). If the start command is not accepted, this process ends.

  On the other hand, when a command for starting the internal combustion engine 10 is detected, the internal combustion engine 10 is started (S122). When the internal combustion engine 10 is stopped, a cylinder that exceeds IVC (1) is first identified at the start, and the intake valve timing of the bank including this cylinder is the decompression timing, and the other bank is the starting timing. Is set to Therefore, in step S122, it is only necessary to start the engine while maintaining the set valve timing, whereby the cylinder in the first compression stroke is brought into a decompressed state, and the occurrence of vibration is suppressed.

  Next, it is detected whether or not the position of the piston 20 of the cylinder that first enters IVC (1) has reached a position corresponding to IVC (1) (S124). Here, the current crank angle is monitored by the output of the rotational speed sensor 26, and it is determined whether or not the piston 20 of the cylinder in the first compression stroke has reached IVC (1).

  In step S124, when it is not recognized that the piston 20 of the first cylinder has reached IVC (1), the operation of the internal combustion engine 10 is maintained until it is recognized that IVC (1) has been reached. On the other hand, when it is recognized in step S124 that the piston 20 of the first cylinder has reached IVC (1), of the first and second banks 12, 14, the intake valve 40 of the bank to which the first cylinder belongs is determined. The valve timing is switched to the start timing fire timing (S126). Thereafter, this process ends.

  According to the above processing, when the internal combustion engine 10 is stopped, the cylinder that first reaches IVC (1) at the next start is specified, the intake valve 40 of the bank to which the cylinder belongs is set to the decompression timing, and the other bank The intake valve 40 is set to the start timing. Thus, when starting the internal combustion engine 10, the engine starts normally, and when the first cylinder reaches IVC (1), the bank to which the cylinder belongs is switched from the decompression timing to the ignition timing at the start time. Immediately after starting cranking in the decompressed state, it is possible to start from the second compression timing to the start timing fire timing, and to improve startability while suppressing vibration.

  In the first embodiment, the illustrated decompression timing and optimum valve timing for ignition do not constrain the present invention. For example, the valve timing for performing the compression stroke in the decompression state may be other timing as long as the pressure of the cylinder in the compression stroke can be reduced. Also, the optimal valve timing for ignition may be other timing as long as the gas can be sufficiently filled to increase the in-cylinder temperature efficiently and a sufficient amount of air can be secured for ignition.

  For example, when the closing timing of the decompression intake valve is advanced or the opening timing of the optimal ignition timing is delayed, the switching time from the decompression timing of the intake valve 40 to the ignition timing at the start time becomes longer. Therefore, the valve timing can be switched reliably, and the starting timing can be realized more efficiently.

  In the first embodiment, the case where the internal combustion engine 10 has two banks and each bank includes three cylinders has been described. However, in the present invention, the number of cylinders in each bank is not limited to this. Further, the internal combustion engine of the present invention is not limited to one separated into two banks connected in parallel. For example, when a plurality of cylinders are connected in series, the internal combustion engine of the present invention may be one that can control the timing of the intake valve for each of several cylinders.

  In the first embodiment, from the stop position of the internal combustion engine 10, the cylinder that exceeds IVC (1) is first identified at the next start, and the intake valve of the bank to which this cylinder belongs is set to the decompression timing. Explained the case. However, the present invention is not limited to this. For example, a cylinder that first reaches IVC (1) at the next start is specified in advance, and the stop position is set so that the cylinder first reaches IVC (1). You may adjust.

  Further, in the first embodiment, when the internal combustion engine 10 is stopped, a cylinder that first reaches IVC (1) is specified in advance, and the valve timing is set in advance so that the intake valve of the bank becomes the decompression timing. explained. However, these controls are not limited to when the engine is stopped, but may be performed when the internal combustion engine 10 is started.

  For example, in the first embodiment, by executing steps S106 and S108, the “first opening / closing timing setting means” and the “second opening / closing timing setting means” of the present invention are realized, and step S124 is executed. Thus, the “valve closing detecting means” is realized, and the “switching means” is realized by executing step S126.

Embodiment 2. FIG.
The system of the second embodiment has the same configuration as the system of FIG. 1 except that the internal combustion engine 10 has eight cylinders 1 to 8. FIG. 12 is a schematic diagram for explaining the configuration of the internal combustion engine of the second embodiment. As shown in FIG. 12, the internal combustion engine 10 includes eight cylinders 1 to 8, the cylinders 1, 3, 5, and 7 constitute a first bank 12, and the cylinders 2, 4, 6, and 8 are first cylinders. Two banks 14 are configured. The same intake manifolds 34 and 36 are connected to the intake ports 30 of the respective cylinders 1 to 8 for each bank. Similarly, the exhaust port of each cylinder is connected to the same exhaust manifold for each bank. Also in the system of the second embodiment, the valve timings of the intake valves 40 of the cylinders 1 to 8 are configured to be controlled independently for the same bank.

  FIG. 13 is a diagram for explaining the ignition order of the cylinders 1 to 8 of the internal combustion engine 10 of FIG. As shown in FIG. 13, in the internal combustion engine 10, ignition is repeated in the order of cylinder 1, cylinder 8, cylinder 4, cylinder 3, cylinder 6, cylinder 5, cylinder 7, and cylinder 2. In the entire internal combustion engine 10, the intervals (phase differences) between the cylinders that are continuously ignited are uniform, and the crank angle is 90 degrees. However, when this phase difference is viewed for each bank, for example, in the first bank 12, the phase difference between the cylinder 1 and the cylinder 3 is 270 degrees, the phase difference between the cylinder 3 and the cylinder 5 is 180 degrees, and the cylinder 5 and the cylinder The phase difference between the cylinder 7 and the cylinder 1 is 90 degrees, and the phase difference between the cylinder 7 and the cylinder 1 is 180 degrees. Similarly, in the second bank 14, the phase difference between the cylinder 8 and the cylinder 4 is 90 degrees, the phase difference between the cylinder 4 and the cylinder 6 is 180 degrees, the phase difference between the cylinder 6 and the cylinder 2 is 270 degrees, The phase difference between 2 and cylinder 8 is 180 degrees and is not uniform.

  Therefore, in the system according to the second embodiment, when viewed in the same bank, switching from the decompression timing to the start timing fire timing is performed at the timing when the phase difference becomes long. Specifically, switching from the decompression timing to the start timing fire timing is performed between the cylinder 1 and the cylinder 3 or between the cylinder 6 and the cylinder 2. That is, at the start of cranking of the internal combustion engine 10, either cylinder 1 or cylinder 6 first passes IVC (1), and the intake valve 40 of that cylinder is controlled at the decompression timing.

  FIG. 14 is a valve timing chart for illustrating the intake valve timing and the piston position when starting the internal combustion engine 10 according to the second embodiment of the present invention. FIG. 14 shows a case where the cylinder 1 is a cylinder that first reaches the position of IVC (1) when the internal combustion engine 10 is started. The intake valve 40 on the first bank 12 side is set to have the decompression timing shown in (1), and the intake valve 40 on the second bank 14 side is set to have the start timing fire shown in (2). Is done. When this state cranking is started, the piston 20 of the cylinder 1 rises from the position A1 in the middle of the compression stroke while the intake valve 40 is opened. When the piston 20 rises to IVC (1), the intake valve 40 is closed.

  At this time, since the cylinder 8 following the cylinder 1 is a cylinder of the second bank 14, it is set in advance to the start timing. Therefore, after the cylinder 1 starts the decompression compression stroke, the subsequent cylinder 8 performs valve control at the start timing. That is, the piston 20 of the cylinder 8 reaches the compression BDC (IVC (2)) from the state stopped at the position A8 close to BDC, and at this time, the intake valve 40 is closed. Then, it moves to position B8 of the compression stroke. During this time, the subsequent cylinder 4 is also controlled at the start timing, and the piston 20 of the cylinder 4 moves from position A4 in the vicinity of IVO (1) to position B4. During this time, when the piston 20 reaches IVO (2), the intake valve 40 is opened. In this way, in the cylinders 8 and 4 following the cylinder 1, the intake valve 40 is controlled at the start-time fire timing and sufficient compression is performed. Therefore, ignition from the cylinder 8, that is, ignition from the second compression after the start. Is realized.

  On the first bank 12 side, two cylinders 8 and 4 exist between the cylinder 1 and the cylinder 3, and the phase difference between the cylinder 1 and the cylinder 3 is within the first bank 12. It is larger than the phase difference between the other cylinders. Therefore, the valve timing of the intake valve 10 is switched between the cylinder 1 and the cylinder 3. As a result, after the cylinder 1 reaches IVC (1) at the decompression timing, the valve timing of the intake valve can be switched before the piston 20 of the cylinder 3 reaches the valve opening timing IVO (2) at the starting timing. it can. Accordingly, after the cylinder 1 is controlled at the decompression timing, the subsequent cylinder 3 can realize the compression stroke at the start timing fire timing. As a result, when the internal combustion engine 10 is viewed as a whole, after the cylinder 1 is controlled at the decompression timing at the time of the first cranking after the internal combustion engine is started, the intake valve is started at the start timing at all cylinders after the cylinder 8. Can be controlled. Therefore, generation of vibration can be suppressed and startability can be improved.

  FIG. 15 is a flowchart for illustrating a control routine executed by the system in the second embodiment of the present invention. The routine shown in FIG. 15 is a routine that is executed in place of the routine of FIG. The routine of FIG. 15 is the same as the routine of FIG. 10 except that the processes of steps S202 and S204 are performed instead of the processes of steps S106 and S108 of the routine of FIG.

  Specifically, when the crank angle is detected after the stop command for the internal combustion engine 10 is issued (S102, S104), the piston position of the IVC (1) is first in the compression stroke at the next start. The cylinder (specific cylinder) that first exceeds is adjusted to be cylinder 1 or cylinder 6 (S202). In other words, from the current crank angle, it is specified which of cylinder 1 and cylinder 6 is close to the stop position at which IVC (1) first passes, and the specified cylinder 1 or 6 is It is adjusted so that it will come to the position that passes (1) first.

  Next, the bank (specific cylinder group) to which the cylinder first set to exceed IVC (1) among any of the first and second banks 12 and 14 is set to be decompression timing. The other bank is set to have a start-up fire timing (S204). Thereafter, the internal combustion engine 10 is stopped (S110), and the routine at the time of stop ends.

  The routine at the start of the internal combustion engine 10 is the same as the routine of FIG. When the internal combustion engine 10 is started, the routine shown in FIG. 11 is executed, so that the first compression stroke at the time of startup is performed in a decompressed state. From the subsequent compression stroke, the intake valve is controlled at the start timing fire timing. In addition, the bank that was set to decompression timing is switched to start timing fire timing when the first cylinder exceeds IVC (1), and the intake valve timing of all cylinders becomes start timing fire timing, The process at the start of the internal combustion engine 10 is completed.

  As described above, in the second embodiment, when the ignition interval of each cylinder in the same bank is not constant, the phase difference from the cylinder immediately after the ignition order when viewed in the same bank is A large cylinder is selected, and this cylinder is first identified as a cylinder that exceeds IVC (1) when starting. As a result, even when the ignition interval between the cylinders is short when the internal combustion engine 10 is viewed as a whole, the switching from the decompression timing to the control of the ignition timing at the starting time is performed using the timing at which the ignition interval in the bank is long. It can be done reliably. Therefore, the optimal valve timing for ignition at the time of starting can be reliably realized from the second and subsequent compression strokes after starting, and startability can be improved while suppressing vibration at the time of starting.

  In the second embodiment, the case where the internal combustion engine 10 has two banks of the first bank 12 and the second bank 14 and each bank includes four cylinders has been described. However, in the present invention, the number of cylinders included in each bank is not limited to four. In addition, the structure is not limited to two banks. For example, when a plurality of cylinders are connected in series, the cylinder can control the timing of the intake valve for each of several cylinders. It may be. However, even in this case, it is necessary that the ignition interval is not constant within a group of cylinders controlled at the same timing.

  Further, in the second embodiment, from the stop position of the internal combustion engine 10, the cylinder that first exceeds IVC (1) at the next start is specified as either cylinder 1 or cylinder 6, and the intake valve of the bank to which this cylinder belongs is specified. The case where is set to be the decompression timing has been described. However, the present invention is not limited to this. For example, the cylinder that first reaches IVC (1) at the next start is predetermined as cylinder 1 or cylinder 6, and that cylinder first reaches IVC (1). In this way, the stop position may be adjusted.

  In the second embodiment, when the internal combustion engine 10 is stopped, the cylinder that first reaches IVC (1) is specified in advance, and the valve timing is set in advance so that the intake valve of the bank is at the decompression timing. explained. However, these controls are not limited to when the engine is stopped, but may be performed when the internal combustion engine 10 is started.

  In the second embodiment, the “specific cylinder determining means” of the present invention is realized by executing step S202, and the “start start position control means” of the present invention is realized by executing step S204. Realize.

Embodiment 3 FIG.
The system of the third embodiment has the same system configuration as that of the second embodiment. The system of the third embodiment is the same as the system of the second embodiment except that the piston stop position of each cylinder when the internal combustion engine 10 is stopped is controlled as follows.

  FIG. 16 is a valve timing diagram for explaining the piston position and the intake valve timing at the start of the internal combustion engine 10 in the third embodiment. In the apparatus of the third embodiment, when the internal combustion engine 10 is started, the stop position of the piston 20 of the cylinder 2 or the cylinder 3 is controlled so as to start from IVC (1) at the next start. FIG. 16 shows an example in which the piston 20 of the cylinder 2 is controlled so as to stop at the position of IVC (1). In this case, when the internal combustion engine 10 is started next time, the cylinder (specific cylinder) exceeding IVC (1) first becomes the cylinder 1. In this case, in the first bank 12 to which the cylinder 1 belongs, the intake valve is set to the decompression timing at the time of starting, and the second bank 14 is set to the starting timing fire timing.

  As shown in FIG. 16, the piston 20 of the cylinder 2 stops at IVC (1). The cylinder interior of the cylinder 2 is gradually replaced with the atmosphere while the internal combustion engine 10 is stopped, and the cylinder interior pressure of the cylinder 2 becomes close to atmospheric pressure. That is, for the cylinder 2 that starts from the state where the piston 20 is stopped at IVC (1), the in-cylinder air amount is equivalent to the decompressed air amount, so that the internal combustion engine 10 is started and the piston 20 is started. Even if starts to rise, the occurrence of vibration can be suppressed in the same manner as the cranking start in the decompressed state.

  The cylinder 1 following the cylinder 2 is controlled at the decompression timing. When the cylinder 2 is in the position of IVC (1), the cylinder 1 is in the position A1 retarded by 90 degrees. When starting the internal combustion engine 10 in this state, the intake valve 40 is in an open state until the piston 20 of the cylinder 1 reaches IVC (1). Therefore, the compression stroke can be performed even in the cylinder 1 in the decompressed state.

  Thus, by stopping the stop position of the cylinder 2 at the valve closing timing position of the decompression timing, the compression stroke of the cylinder 2 at the start can be brought into the decompressed state. Therefore, the cylinder 2 can be in a decompressed state only at the first cranking at the start even if the valve timing is set to the start timing fire timing. Accordingly, the compression stroke in the decompressed state can be realized without switching the valve timing for the second bank 14, and the decompressed state can be achieved even in the subsequent cylinder 1, so that the decompressed state for two compressions is secured. Can be started.

  Further, until the cylinder 1 reaches the IVC (1) from the starting position A1, the subsequent cylinder 8 and cylinder 4 move from the positions A8 to B8 or A4 to B4 where the phase is retarded by 90 degrees, respectively. . At this time, since both the cylinder 8 and the cylinder 4 are controlled at the start timing, the intake valve 40 of the cylinder 8 is closed when the piston 20 of the cylinder 8 passes IVC (2) (compression BDC). Is done. Further, in the cylinder 4, the piston starts to descend from the position A4 before the IVO (2), and when the intake valve 40 is opened at the IVO (2), the air-fuel mixture flows in at once. Thereafter, when the piston 20 of the cylinder 4 reaches IVC (2), the intake valve 40 is closed, and the piston 20 is further raised to compress the gas in the cylinder 4. Therefore, after the start in the decompressed state in the cylinder 2 and the cylinder 1 is realized, the subsequent cylinders are controlled at the optimal ignition timing at the ignition timing, and the third compression, that is, the ignition from the cylinder 8 is realized. be able to.

  Further, as in the second embodiment, the intake valve 40 of the cylinder 1 is closed before the piston 20 of the cylinder 3 enters the intake stroke from the exhaust stroke position A3 and before IVO (1). At this time, the intake valve 40 of the first bank 12 is switched from the decompression timing to the start timing fire timing. Accordingly, after that, the intake valve 40 opens so that the piston 20 of the cylinder 3 passes through the position of IVO (1) and reaches IVO (2), and closes when it reaches IVC (2). Is controlled, and the cylinder 3 can be switched to a state favorable for ignition.

  Although FIG. 16 shows the case where the cylinder 2 is stopped at the position of IVC (1), the same state can be realized by stopping the cylinder 3 at IVC (1). That is, by stopping the cylinder 3 at the position of IVC (1) and setting the subsequent cylinder 6 (that is, the second bank 14) to the decompression timing, the cylinder 3 and the cylinder 6 that are initially in the compression stroke at the start are in the decompressed state. Can be started. In addition, since the first bank 12 is set to the start-time fire timing, ignition can be realized from the cylinder 5 following the cylinder 6. Further, after the cylinder 6, the cylinder 2 which is the next compression stroke in the second bank 14 has a phase difference of 270 degrees from the cylinder 6. Therefore, after the cylinder 6 is closed at IVC (1), the valve timing of the second bank 14 can be switched to the start timing fire timing, and the cylinder 6 also starts the decompressed state in the cylinder 6. After igniting, ignition can be performed by controlling the valve timing at the optimum ignition timing.

  Therefore, in the apparatus of the third embodiment, when the internal combustion engine 10 is stopped, the piston 20 of the cylinder on the side closer to the IVC (1) position of either the cylinder 2 or the cylinder 3 is stopped at IVC (1). Control the stop position. Then, the intake valve 40 of the bank to which the cylinder to which the stop position of the piston 20 is set to IVC (1) belongs is set to the start timing fire timing, and the intake valve timing of the other bank is set to the decompression timing. As a result, the cylinder 2 or 3 that initially exceeds the compression TDC at the start can be brought into a state corresponding to the decompressed state, and the subsequent compression stroke of the cylinder 1 or 6 can be performed in the decompressed state. it can. Therefore, when the internal combustion engine 10 is started, the compression stroke for the first two compressions can be set to the decompressed state, and generation of vibration at the time of starting can be suppressed more reliably.

  FIG. 17 is a flowchart for illustrating a control routine executed by ECU 80 in the third embodiment of the present invention. The routine of FIG. 17 is a routine that is executed when the internal combustion engine 10 is stopped in place of the routine of FIG. The routine in FIG. 17 is the same as the routine in FIG. 10 except that the processes in steps S302 to S306 are executed instead of the processes in steps S106 to S108.

  Specifically, when the crank angle is detected after an instruction to stop the internal combustion engine 10 is recognized (S102, S104), the piston 20 of any cylinder of the cylinders 2 and 3 from the current crank angle. Whether the stop position is set to IVC (1) is specified (S302). Next, the bank to which the cylinder identified in step S302 belongs is set to the start timing, and the intake valve of the other bank is set to the decompression timing (S304). Thereafter, control is performed so that the piston stop position of the identified cylinder 2 or cylinder 3 becomes IVC (1) (step S306), and the internal combustion engine 10 is stopped (S110).

  In the state stopped as described above, the routine of FIG. 11 is executed at the time of start-up, so that the compression stroke for two compressions is brought into the decompressed state, and thereafter the control of the third embodiment is made to immediately set the optimal ignition timing. Can be realized.

  In the third embodiment, the case where the stop position of the piston 20 of the cylinder 2 or the cylinder 3 is set to IVC (1) has been described. However, in the present invention, the stop position of the piston 20 is not limited to IVC (1), and may be, for example, stopped at a position advanced from IVC (1) in the compression stroke. Even in this case, when the internal combustion engine 10 is started, the first compression stroke of the cylinder 2 or the cylinder 3 can be made the compression stroke in the decompressed state.

  For example, in the third embodiment, “specific cylinder determining means” is realized by executing step S302, and “stop position control means” is realized by executing step S306.

  Further, in the above embodiment, when the number of each element, number, quantity, range, etc. is mentioned, it is mentioned unless otherwise specified or clearly specified in principle. The number is not limited. Further, the structures described in the embodiments, steps in the method, and the like are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

It is a schematic diagram for demonstrating the structure of the control apparatus of the internal combustion engine in Embodiment 1 of this invention. It is a schematic diagram for demonstrating arrangement | positioning of the cylinder of the internal combustion engine in Embodiment 1 of this invention. It is a schematic diagram for demonstrating the intake valve timing of the internal combustion engine in Embodiment 1 of this invention. It is a figure for demonstrating the intake valve timing and piston position at the time of the starting of the internal combustion engine in Embodiment 1 of this invention. It is a figure for demonstrating control of the ignition order and valve timing of each cylinder of the internal combustion engine in Embodiment 1 of this invention. It is a figure for demonstrating the intake valve timing and piston position at the time of the starting of the internal combustion engine in Embodiment 1 of this invention. It is a figure for demonstrating the intake valve timing and piston position at the time of the starting of the internal combustion engine in Embodiment 1 of this invention. It is a figure for demonstrating the intake valve timing and piston position at the time of the starting of the internal combustion engine in Embodiment 1 of this invention. It is a figure for demonstrating the intake valve timing and piston position at the time of the starting of the internal combustion engine in Embodiment 1 of this invention. It is a figure for demonstrating the routine of control which a control apparatus performs in Embodiment 1 of this invention. It is a figure for demonstrating the routine of control which a control apparatus performs in Embodiment 1 of this invention. It is a schematic diagram for demonstrating arrangement | positioning of the cylinder of the internal combustion engine in Embodiment 2 of this invention. It is a figure for demonstrating the ignition order and phase difference of the cylinder of the internal combustion engine in Embodiment 2 of this invention. It is a figure for demonstrating the intake valve timing and piston position at the time of the start of the internal combustion engine in Embodiment 2 of this invention. It is a flowchart for demonstrating the routine of control which ECU performs in Embodiment 2 of this invention. It is a figure for demonstrating the intake valve timing and piston position at the time of the starting of the internal combustion engine in Embodiment 3 of this invention. It is a flowchart for demonstrating the routine of control which ECU performs in Embodiment 3 of this invention.

Explanation of symbols

1 to 8 cylinders 10 internal combustion engine 12 first bank 14 second bank 20 piston 22 connecting rod 24 rotation speed sensor 26 combustion chamber 28 spark plug 30 intake port 32 exhaust port 34 intake manifold 36 exhaust manifold 40 intake valve 42 intake valve shaft 44 valve lifter 46 Valve spring 50 Intake cam 52 VVT mechanism 54 Cam position sensor 60 Exhaust valve 62 Exhaust valve shaft 64 Valve lifter 66 Valve spring 70 Exhaust cam 72 VVT mechanism 74 Cam position sensor 80 ECU

Claims (6)

A control device for an internal combustion engine having two cylinder groups each having a plurality of cylinders,
Intake valve control means for variably controlling the opening / closing timing of the intake valve of each cylinder of the two cylinder groups for the same cylinder group;
First, after the internal combustion engine is started, the opening / closing timing of the intake valve of the cylinder group (hereinafter referred to as “specific cylinder group”) to which the cylinder (hereinafter referred to as “specific cylinder group”) reaches the closing timing of the intake valve at the first opening / closing timing. A first opening / closing timing setting means for setting the first opening / closing timing; and a second opening / closing timing for setting an opening / closing timing of an intake valve of a cylinder group different from the specific cylinder group to a second opening / closing timing when the internal combustion engine is started. Timing setting means;
With
The first opening / closing timing includes an amount of gas sucked into the cylinder when the intake valve is controlled to the first opening / closing timing, and an amount of gas sucked into the cylinder when the intake valve is controlled to the second opening / closing timing. A control device for an internal combustion engine, characterized in that the opening / closing timing becomes smaller than that.   The second opening / closing timing is an opening / closing timing at which a cylinder controlled at the second opening / closing timing has a higher in-cylinder temperature than a cylinder controlled at the first opening / closing timing. The control apparatus for an internal combustion engine according to claim 1. The first opening / closing timing is a timing for opening the intake valve in the vicinity of the top dead center and closing the intake valve in the latter half of the compression stroke,
3. The control device for an internal combustion engine according to claim 1, wherein the second opening / closing timing is a timing at which the intake valve is opened on the retard side from the top dead center and the intake valve is closed near the bottom dead center. . A valve closing detecting means for detecting an initial valve closing of the intake valve of the specific cylinder at the time of starting the internal combustion engine;
Switching means for switching the opening / closing timing of the intake valve of the specific cylinder group to the second opening / closing timing when the first closing of the intake valve of the specific cylinder is detected;
The control apparatus for an internal combustion engine according to any one of claims 1 to 3, further comprising: Specific cylinder determining means for determining the specific cylinder such that two or more cylinders whose ignition sequence continues immediately after the specific cylinder are included in a cylinder group different from the specific cylinder group;
Start start position control means for controlling the start start position of the piston of the specific cylinder so that the determined specific cylinder first reaches the valve closing timing of the first opening / closing timing when the internal combustion engine is started;
The control apparatus for an internal combustion engine according to claim 4, further comprising: Specific cylinder determining means for determining the specific cylinder such that a cylinder whose ignition order is immediately before the specific cylinder is included in a cylinder group different from the specific cylinder group;
Stop position control means for controlling the stop position of the piston of the cylinder whose ignition order is immediately before the specific cylinder when the internal combustion engine is stopped to a position corresponding to the valve opening timing of the first opening / closing timing;
The control apparatus for an internal combustion engine according to claim 4 or 5, characterized by comprising:

Images