JP2007064021A - Spark ignition type four cycle engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To exhibit suitable compressed self-ignition performance in response to an operation load area of an engine. <P>SOLUTION: An intake valve opening in a first period of an intake stroke as indicated by IN1, is closed before the intake bottom dead center in a compressed self-ignition operation area. The intake valve as indicated by IN2 is made to perform valve reopening operation up to a first period of a compression stroke from a last period of the intake stroke. An exhaust valve performing the valve reopening operation as indicated by EX2, is opened in the middle of the IN1, and is closed in the middle of a valve opening period of the IN2. An ignition assist is performed before the ignition timing on the low load side in the compressed self-ignition operation area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a spark ignition type four-cycle engine, and more particularly, to an operation mode and spark ignition for performing premixed compression auto-ignition combustion (HCCI: “Compression self-ignition” in this specification). The present invention relates to a spark ignition type four-cycle engine having an operation mode to be performed.

In general, a technique is known in which internal EGR gas is used to improve the ignitability of an air-fuel mixture, and to ensure the EGR rate required in a wide operation region in order to enhance exhaust performance (for example, Patent Document 1). In the configuration according to this prior art, the exhaust valve is opened during the intake stroke to realize so-called internal EGR.
JP 2001-107759 A

  By the way, in order to improve the performance of the engine using the internal EGR gas in total, in the compression self-ignition operation region, it is required to prevent misfire on the low load side and to prevent knocking on the high load side. However, in the configuration of Patent Document 1, only the valve opening timing of the internal EGR is adjusted based on the determination of the operation state, so that the compression self-ignition performance is improved according to the load region, or knocking is performed. It was not possible to prevent.

  In particular, simply performing the restart valve operation of the exhaust valve in the intake stroke will not only make compression self-ignition difficult because the inside of the cylinder will be stratified in a state where the burned gas is unevenly distributed around the ignition plug in the combustion chamber. Further, there has been a problem that so-called ignition assist that promotes compression self-ignition by the spark plug becomes difficult.

  The present invention has been made in view of the above problems, and an object thereof is to provide a spark ignition type four-cycle engine capable of exhibiting a suitable compression self-ignition performance in accordance with an engine operating load region.

  In order to solve the above-described problems, the present invention provides a cylinder that forms a combustion chamber at the top, a spark plug disposed in a central portion of the combustion chamber, an intake port and an exhaust port that communicate with the combustion chamber, and an intake port An intake valve provided at the exhaust port and an exhaust valve provided at the exhaust port, and in a predetermined operating region of the engine, the burned gas is recirculated into the cylinder by a restart valve operation that opens the exhaust valve in the intake stroke, and compression self-ignition A spark ignition type four-cycle engine configured to operate, and controls opening / closing timings of an intake valve and an exhaust valve based on a determination of an operation state determination unit that determines an operation state of the engine and a determination of the operation state determination unit A valve opening / closing control means; and an ignition control means for controlling the ignition timing of the spark plug based on the determination of the operating state determination means. The valve opening / closing control means is provided in the predetermined operating region. The intake valve that opens in the first half of the intake stroke is closed before the intake bottom dead center, and the intake valve is restarted from the second half of the intake stroke to the first half of the compression stroke. The intake valve and the exhaust valve are controlled so as to be opened during the initial valve opening period of the intake valve and closed during the valve opening period of the intake valve that performs the resuming valve operation. In the operating region, the spark ignition type four-cycle engine is characterized in that, on the low load side, the spark plug is controlled so as to execute ignition before an ignition timing assumed in advance. In this mode, in a predetermined operating region of the engine, the intake valve that is opened in the intake stroke is closed before the intake bottom dead center, and the exhaust valve is restarted in the intake stroke so that fresh air is first introduced into the cylinder. Then, the burned gas recirculates in the cylinder. At this stage, the burned gas forms a swirl in a predetermined direction in the upper layer of fresh air from the intake valve that is first opened in the intake stroke, and the cylinder is stratified in a state of being unevenly distributed around the spark plug. Here, in this aspect, the intake valve restarts during the period from the latter half of the intake stroke to the first half of the compression stroke, and the exhaust valve that performs the restart valve opens during the first valve opening period of the intake valve, and Since the intake valve that closes the valve is closed during the valve opening period, fresh air is supplied to the upper layer of the stratified burnt gas and stratified by the restart of the intake valve, and the intake valve restarts around the spark plug. The fresh air by valve operation fills up. As a result, the ignition plug is driven before ignition, thereby providing an ignition assist function, and even when the in-cylinder temperature is low, the air-fuel mixture in the cylinder can be reliably ignited in a relatively lean state. It becomes possible.

  In a preferred aspect, a plurality of sets of intake ports and intake valves are provided, and the valve opening / closing control means controls the intake valves so that one intake valve is opened during an intake stroke and a restart valve operation is performed with another intake valve. Is. In this aspect, the opening timing of the intake valve can be easily multistaged.

  In a preferred embodiment, a plurality of intake ports and exhaust ports are arranged on the opposite sides of the front and rear axis of the cylinder with the spark plug as the center, and an intake valve is provided for each intake port and an exhaust valve is provided for each exhaust port. The valve opening / closing control means causes one of the plurality of exhaust valves to perform the restart valve operation, and at the first intake valve opening timing in the predetermined operation region, the restart valve operation of the one exhaust valve The intake valve and the exhaust valve are controlled so that only the intake valve of the intake port that flows out the intake air in the direction of weakening the generated swirl flow is opened. In this aspect, in the predetermined operating region, fresh air is introduced into the cylinder in a direction that disturbs the swirl by the exhaust valve, so that mixing of fresh air and burned gas is promoted. As a result, particularly on the low load side, the in-cylinder temperature rises rapidly, and in combination with the action of the ignition assist, it becomes possible to reliably perform the compression self-ignition without remaining unburned in a lean state.

  In a preferred embodiment, the valve opening / closing control means advances the valve opening timing of the exhaust valve that performs the resuming valve operation toward the low load side. In this mode, as the valve opening timing of the exhaust valve that performs the resuming valve operation advances as the load decreases, the internal EGR rate increases as the load decreases in the first half of the intake stroke, and the in-cylinder temperature can be increased. Then, fresh air is introduced around the spark plug by the resuming valve operation of the intake valve, and it is possible to achieve compression self-ignition in a relatively lean state while increasing the in-cylinder temperature.

  In a preferred aspect, the valve opening / closing control means prohibits the resumption valve operation of the intake valve on the high load side in the predetermined operation region. In this aspect, by prohibiting the restart valve operation of the intake valve, the stratification remains in a state where the burned gas due to the restart valve operation of the exhaust valve is unevenly distributed in the combustion chamber, so that the ignition timing can be easily controlled. Thus, knocking can be prevented. Further, in the high load side operation region, particularly in the low engine rotation region, the effective compression ratio is increased by prohibiting the restart valve operation of the intake valve, thereby increasing the ignition performance. The operation of the high load side increases the temperature of the burned gas, the gas temperature in the cylinder is increased, and the reduction in the effective compression ratio is suppressed, thereby increasing the ignition performance potential. Thus, even if burned gas is supplied to the upper part of the combustion chamber by the resuming valve operation of the exhaust valve, there is no risk of misfire, and the ignition timing can be easily controlled. That is, the ignition timing can be easily controlled by adjusting the ignition timing and adjusting the ignition assist timing.

  Another aspect of the present invention is provided in a cylinder that forms a combustion chamber at the top, a spark plug disposed in a central portion of the combustion chamber, an intake port and an exhaust port that communicate with the combustion chamber, and an intake port. In the predetermined operating region of the engine, the burned gas is recirculated into the cylinder by a restart valve operation that opens the exhaust valve in the intake stroke, and the compression self-ignition operation is performed. A spark ignition type four-cycle engine configured as described above, wherein the operating state determining means for determining the operating state of the engine and the valve opening / closing control for controlling the opening / closing timing of the intake valve and the exhaust valve based on the determination of the operating state determining means And ignition control means for controlling the ignition timing of the spark plug based on the determination of the operating state determination means, and the valve opening / closing control means has a high load in the predetermined operating region. In the rotation region, the intake valve that opens in the intake stroke is closed before the bottom dead center of the intake stroke, and the intake valve and the exhaust valve are controlled so that the restart operation of the exhaust valve is performed from the middle of the intake stroke to the first half of the compression stroke. As the operating range becomes the low load side, the intake valve is controlled to advance and the exhaust valve to be retarded so that the intake valve opens before the exhaust valve performing the restart valve operation. The ignition control means controls the spark plug so that ignition is executed before a presumed ignition timing on the low load side in the predetermined operating region of the engine. This is a spark ignition type 4-cycle engine. In this mode, in a predetermined operation region in which the compression self-ignition operation is performed, in the high load operation region, the intake valve that opens in the intake stroke is closed before the bottom dead center of the intake stroke, and from the middle of the intake stroke to the first half of the compression stroke. Since the exhaust valve performs the restart valve operation, the burned gas resulting from the restart valve operation is stratified in a state of being unevenly distributed in the combustion chamber, so that the ignition timing can be easily controlled and knocking can be prevented. . On the other hand, on the low load side, based on the setting of the high load operation region, the intake valve advances and the exhaust valve retards so that the intake valve opens before the exhaust valve that performs the restart valve operation. Stratification in the cylinder is promoted with fresh air unevenly distributed in the combustion chamber. Therefore, it becomes possible to control the stratified gas around the spark plug according to the operating state and obtain a suitable compression self-ignition characteristic. In this state, since the spark plug performs ignition before the ignition timing, it is possible to reliably ignite the air-fuel mixture in the cylinder in a relatively lean state even when the temperature in the cylinder is low. Become.

  As described above, according to the present invention, on the low load side, the fresh air is unevenly distributed on the combustion chamber side rather than the burned gas due to the restart valve operation of the exhaust valve, and the compression self-ignition by the ignition assist is ensured. Therefore, a remarkable effect is achieved that it is possible to exhibit a suitable compression self-ignition performance in accordance with the operating load region of the engine.

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

  FIG. 1 is a configuration diagram showing a schematic configuration of a spark ignition type four-cycle engine 10 according to an embodiment of the present invention, and FIG. 2 is provided with one cylinder of an engine body 20 according to FIG. 2 is a schematic cross-sectional view showing the structure of the intake valve 40 and the exhaust valve 60. FIG. 3 is a schematic plan view showing the structure of one cylinder of the engine body 20 and the intake valve 40 and the exhaust valve 60 provided thereto.

  In these drawings, the engine body 20 of the illustrated spark ignition type four-cycle engine 10 includes a cylinder block 22 that rotatably supports a crankshaft 21 and a cylinder head 23 that is disposed above the cylinder block 22. Have.

  The cylinder block 22 and the cylinder head 23 are provided with a plurality of cylinders 24. Each cylinder 24 is provided with a piston 25 connected to the crankshaft 21 and a combustion chamber 26 formed in the cylinder 24 by the piston 25 in the same manner as a known configuration. The cylinder block 22 is provided with a crank angle sensor 27 that detects the rotation angle (crank angle) of the crankshaft 21.

  A fuel injection valve 28 that directly injects fuel into the combustion chamber 26 is provided at the side of each combustion chamber 26. An ignition plug 29 is provided at the top of each combustion chamber 26, and the plug tip faces the combustion chamber 26. An ignition circuit 29a capable of controlling the ignition timing by electronic control is connected to the ignition plug 29.

  The engine body 20 includes an intake system 30 that supplies fresh air into the cylinder 24 and an exhaust system 50 that exhausts burned gas burned in the combustion chamber 26 of the cylinder 24.

  The intake system 30 includes an intake pipe 31 for supplying fresh air into the cylinder 24, and an intake manifold 32 communicating with the downstream side of the intake pipe 31. The intake manifold 32 branches from the surge tank and corresponds to each. A branch intake pipe 33 connected to the cylinder 24 is provided. In the illustrated embodiment, each cylinder 24 is formed with a pair of intake ports 24a (see FIG. 1), and the downstream end of the branched intake pipe 33 corresponds to the intake port 24a of each cylinder 24. And it is formed in two forks.

Referring to FIG. 3, the throat portions at the downstream ends of the intake ports 24 a provided in the cylinders 24 are all aligned along the longitudinal axis L of the cylinder 24 with the spark plug 29 as the center. Further, in the present embodiment, the throat portion in the vicinity of the downstream end of each intake port 24a is formed such that the throat axis L _IN extends obliquely from the rear to the front and intersects the axis L. For this reason, the fresh air introduced from the intake ports 24a, 24a is configured to form a swirl in the counterclockwise direction in the drawing.

  With reference to FIGS. 1 and 2, an airflow sensor 34 is provided in the intake pipe 31 of the intake system 30. Further, the intake pipe 31 is provided with a throttle valve 35 for adjusting the intake flow rate. The throttle valve 35 is configured to be opened and closed by an actuator 36.

  Each intake port 24a provided in each cylinder 24 is provided with an intake valve 40. In the illustrated embodiment, two intake valves 40 are provided for each cylinder corresponding to the intake port. Each intake valve 40 is configured to be driven by a camshaft 41 a of a valve operating mechanism 41. The valve mechanism 41 has a VCT (Variable Camshaft Timing Mechanism) 42 composed of an OCV (Oil Control Valve System) or the like. The detailed configuration of the VCT was previously proposed by the present applicant. Japanese Patent Laid-Open No. 2002-242617, etc., and detailed description thereof will be omitted. In the compression self-ignition operation region, the camshaft 41a has a small lift intake cam 43a that opens the front intake valve 40 with a small lift, and the front intake valve 40 opens with a large lift during normal operation. The large lift intake cam 43b and the restart valve cam 43c for causing the rear intake valve 40 to execute the restart valve operation are fixed at predetermined phases, respectively. In this embodiment, when the solenoid valve constituting the VCT 42 is not excited, the intake valve 40 is set to the most advanced angle state where the valve opens in the first half of the intake stroke.

  As shown in FIG. 3, in each of the pair of front and rear intake valves 40, each intake valve 40 is provided with a valve operation switching mechanism 70 having a lost motion function.

  4 is an exploded perspective view of the valve operation switching mechanism 70 provided in the intake system 40, FIG. 5 is a front sectional view of the valve operation switching mechanism 70, and FIG. 6 is a plan sectional view of the valve operation switching mechanism 70.

  Referring to these drawings, the valve operation switching mechanism 70 is for realizing a so-called lost motion in which the large lift intake cam 43b turns on / off the function of pushing down the stem 40a of the intake valve 40. The example is embodied in a tappet type.

  A valve operation switching mechanism 70 provided on the front intake valve 40 includes a rectangular housing 71, a side tappet 72 that is housed in the housing 71 so as to be movable up and down, and is fixed to the end of the stem 40 a of the intake valve 40. The side tappet 72 is assembled so as to be relatively displaceable with the side tappet 72 and has a center tappet 73. The small lift intake cam 43 a is in contact with the side tappet 72, and the large lift intake cam 43 b is in contact with the center tappet 73.

  The side tappet 72 is formed in a substantially cylindrical shape, and has an accommodation recess 72a in a diametrical direction perpendicular to the camshaft 41a when seen in a plan view. Insertion holes 72c parallel to the camshaft 41a are formed in the wall portions 72b on both sides of the housing recess 72a. The bottomed sleeve-like holders 75a and 75b are fixed to the respective insertion holes 72c in such a posture that the openings face each other. A bearing 76 is fixed to the outside of one sleeve-like holder 75 a, and a rolling element 76 a held by the bearing 76 is in rolling contact with a vertical groove 71 a formed on the inner wall of the housing 71. Thereby, the side tappet 72 is movable along the axial direction (the direction in which the intake valve 40 is opened and closed) in a state where the rotation in the circumferential direction is restricted. A spring seat 72d that receives the valve spring 60d is fixed to the lower portion of the side tappet 72.

  On the other hand, the center tappet 73 is an “I” -shaped structure that follows the outline of the receiving recess 72 a of the side tappet 72 as viewed in plan, and is defined by the receiving recess 72 a and a locking portion provided in the housing 71. In the stroke S, it is assembled so as to be able to move up and down relatively with respect to the side tappet 72 and faces the intake cam 43b for large lift.

  The center tappet 73 is always urged toward the large lift intake cam 43b by a pair of coil springs 77 arranged at the bottom of the accommodation recess 72a of the side tappet 72. The spring coefficient of the coil spring 77 is set so that the urging force is sufficiently smaller than that of the valve spring 60d. Therefore, in the free state, the upper surface of the wall portion 72b of the side tappet 72 and the upper surface of the center tappet 73 are flush with each other as shown in FIG. The center tappet 73 is provided with a pin hole 73a that communicates concentrically with the insertion hole 72c in the free state. A pin unit 78 is accommodated in the pin hole 73a.

  The pin unit 78 includes a lock plunger 78a that can be moved in and out of one sleeve-shaped holder 75a, a coil spring 78b interposed between the lock plunger 78a and the sleeve-shaped holder 75a, and a lock plunger 78a. A lock pin 78c concentrically disposed on the opposite side of the coil spring 78b, and an unlocking plunger 78d accommodated in the other sleeve-like holder 75b so as to be able to advance and retract in order to drive the lock pin 78c toward the lock plunger 78a. In addition, a pair of bushes 78e and 78f fixed to both opening ends of the pin hole 73a to support the lock pin 78c, a flange 78g and a bearing 76 integrally formed at a substantially central portion of the lock pin 78c are arranged. Between the side bush 78e and the lock pin via the flange 78g. 8c and a coil spring 78h for energizing the to the unlocked plunger 78d side. In the free state, the lock plunger 78 a and the lock pin 78 c are interposed between the wall 72 b and the center tappet 73, respectively, so that the center tappet 73 is locked to the side tappet 72. In this state, when the side tappet 72 is driven by the small lift intake cam 43a, the intake valve 40 is opened, and when the center tappet 73 is driven by the large lift intake cam 43b, the side tappet 72 is also passed through the side tappet 72. Thus, the intake valve 40 is opened.

  Further, on the side opposite to the side where the bearing 76 is provided, a hydraulic fluid circuit PH is formed in the wall portion 72b and the sleeve-like holder 75b fixed thereto. Then, when hydraulic fluid is supplied from the hydraulic fluid circuit 79 to the hydraulic fluid circuit PH under the control of the ECU 100, which will be described later, the unlocking plunger 78d is driven to the left in FIG. 5 and FIG. At the same time, the lock plunger 78a is pushed into the corresponding wall 72b, and the lock by these members is released. When the center tappet 73 is driven by the large lift intake cam 43b in this unlocked state, the center tappet 73 moves up and down in the housing recess 72a of the side tappet 72, and the force is absorbed by the coil spring 77. It is not transmitted to the intake valve 40. Thus, the intake valve 40 is opened only when the side tappet 72 is driven by the small lift intake cam 43a, and the intake valve 40 is opened by the large lift intake cam 43b (in the intake stroke during normal operation). It is possible to stop the opening of the large lift. The hydraulic oil circuit 79 is provided with an electromagnetic valve 79a, and the electromagnetic valve 79a is controlled by the ECU 100 as a control device.

  In the present embodiment, as shown in FIG. 1, a hydraulic oil circuit 79 and an electromagnetic valve 79a are provided so that the valve operation switching mechanism 70 of the front intake system 40 can be operated.

  Further, the valve operation switching mechanism 70 provided in the rear intake system 30 is completely the same in principle as the valve operation switching mechanism 70 described with reference to FIGS. It is provided at a position corresponding to the large lift intake cam 43b and is configured to perform a lost motion at a predetermined timing. Then, the lost motion of the restart valve cam 43c is controlled by driving the hydraulic oil circuit 179 and the electromagnetic valve 179a as shown in FIG.

  Next, the exhaust system 50 includes an exhaust manifold 52 in which bifurcated branch exhaust pipes 51 connected to an exhaust port 24b formed in pairs for each cylinder 24 are gathered on the downstream exhaust side, and the exhaust manifold. 52 and an exhaust pipe 53 for discharging burned gas from the exhaust manifold 52.

  Each exhaust port 24b is provided with an exhaust valve 60.

  Referring to FIG. 3, the exhaust valves 60 are also provided in pairs for each cylinder 24. Each exhaust valve 60 is driven by a valve operating mechanism 62. The valve operating mechanism 62 is configured to enable a reopening valve operation for opening the exhaust valve 60 again in the intake stroke in addition to the valve opening operation in the exhaust stroke.

  That is, the valve mechanism 62 includes a VCT 64 similar to the VCT 41 and a camshaft 62a that is driven by the driving force of the crankshaft 21 via the VCT 64. The exhaust valve 60 has a different phase with respect to one exhaust valve 60. Two sets of exhaust cams 62b and 62c for driving the exhaust gas are provided on the camshaft 62a, and a valve operation switching mechanism 70 is provided between the exhaust cams 62b and 62c and one exhaust valve 60. In the present embodiment, the exhaust valve 60 is set to the most retarded state when the solenoid valve constituting the VCT 64 is not excited.

  Further, in the present embodiment, the exhaust valve 60 provided with the valve operation switching mechanism 70 is the front exhaust valve 60 in the front-rear direction as shown in FIG. It is configured not to. The valve operation switching mechanism 70 can be switched between a state in which the drive of both the exhaust cams 62b and 62c is transmitted to the exhaust valve 60 and a state in which only the drive of the one exhaust cam 62b is transmitted to the exhaust valve 60. . One of the two sets of exhaust cams 62b and 62c is a first exhaust cam 62b that opens the exhaust valve 60 in order to discharge the burned gas in the cylinder 24 during the exhaust stroke, and the other is an intake stroke that will be described later. A second exhaust cam 62c that reopens the exhaust valve 60 and recirculates the burned gas into the cylinder. In the present embodiment, the first exhaust cams 62b form a pair, and the second exhaust cam 62c is disposed between the first exhaust cams 62b and 62b in the axial direction of the cam shaft 62a.

  The specific structure of the valve operation switching mechanism 70 provided in the exhaust system 50 is also completely the same in principle as the valve operation switching mechanism 70 described with reference to FIGS. 4 to 6, and the first exhaust cam 62 b is The exhaust valve 60 is provided at a position corresponding to the small lift intake cam 43a and is configured to open the exhaust valve 60 at an exhaust timing in a normal exhaust stroke, and the second exhaust cam 62c is connected to the large lift intake cam 43b. By being provided at a corresponding position, it is configured to perform a lost motion at a predetermined timing. The lost motion of the second exhaust cam 62c is controlled by driving the hydraulic fluid circuit 279 and the electromagnetic valve 279a as shown in FIG.

  Next, the spark ignition type four-cycle engine 10 is provided with an ECU 100.

  As shown in FIG. 1, the ECU 100 includes a CPU 101, a memory 102, an interface 103, and a bus 104 that connects these units 101 to 103.

  The memory 102 of the ECU 100 stores control maps, data, and programs. When the CPU 101 executes these control maps, data, and programs, as shown in FIG. 2, operations such as engine speed and engine load are performed. An operating state determining unit 110 that determines the state, a combustion control unit 120 that controls combustion of the engine according to the determined operating state, and a throttle valve control unit 140 that controls the throttle valve 35 according to the determined operating state. Functionally. Particularly in the present embodiment, the VCT control means 121 described later has a control map 111 for advancing / retarding the VCT 42 for intake and the VCT 64 for exhaust.

  The combustion control means 120 drives and controls the VCT control means 121 that controls the electromagnetic valve of the VCT 42 provided in the valve mechanism 41 of the intake system 30 and the electromagnetic valves 179a and 79a provided in the intake system 30 and the exhaust system 50. Thus, a valve opening / closing control means 123 for switching control of a valve operation switching mechanism 70 provided for the intake valve 40 and the exhaust valve 60 and an ignition control means 124 for controlling ignition by the spark plug 29 are included. .

  Various detection means such as a crank angle sensor 27, an air flow sensor 34, and an accelerator opening sensor 66 are connected to the ECU 100 as input elements. On the other hand, as the control elements, the actuator 36 of the throttle valve 35, the electromagnetic valve provided in the VCT 42 of the valve operating mechanism 41, the electromagnetic valves 79a to 279a of the hydraulic oil circuits 79 to 279 for driving the valve operation switching mechanisms 70, and the spark plug An ignition circuit 29a for controlling ignition by 29, a fuel injection valve 28, and the like are connected.

  Next, the control characteristics stored in the ECU 100 will be described.

  FIG. 7 is a characteristic diagram showing an example of operation region setting for performing control according to the operation state by the combustion control means 120 of the ECU 100.

  As shown in the figure, as an operation region set in the ECU 100, a region A where a so-called compression self-ignition operation (denoted as HCCI in the drawing) is performed, and a spark ignition operation (denoted as SI in the diagram) is performed. Area B is set. The region A of the compression self-ignition operation is a region below a predetermined engine load in a low / medium rotation region where the engine speed ne is relatively low. The spark ignition operation region B is a region other than the compression self-ignition operation region A, that is, a region on the high rotation side and the high load side.

  The operation state determination means 110 of the ECU 100 has a function of detecting the operation state of the engine from the crank angle sensor 27, the accelerator opening sensor 66, and the like, and determining whether the operation state is in the above-described region A or B. It is.

  The VCT control unit 121 of the combustion control unit 120 controls the VCTs 41 and 64 so as to advance or retard the opening timings of the intake valve 40 and the exhaust valve 60 individually based on the determination of the operation state determination unit 110. It has a function. In the present embodiment, based on the VCT control map 111 and the program stored in the ECU 100, the VCT control means 121 is configured to control the intake-side VCT 41 and the exhaust-side VCT 64 in a procedure described in detail later. Yes.

  The valve opening / closing control means 123 operates the solenoid valves 79a to 279a provided in the hydraulic oil circuits 79 and 179 based on the determination of the operating state determination means 110, and as shown in Table 1, the intake valve 40 and the exhaust valve 60 are operated. The valve opening function is controlled.

  The ignition control unit 124 drives the ignition circuit 29a at a predetermined timing based on the determination of the operating state determination unit 110, and executes ignition by the spark plug 29. In the present embodiment, in addition to the normal spark ignition in the spark ignition operation region B, when the compression self-ignition operation region A is in the low load side operation region, the spark plug 29 is driven before the compression self-ignition starts. The so-called ignition assist is executed.

  The throttle valve control means 140 is configured to drive the actuator 36 and control the valve opening amount of the throttle valve 35 based on the determination of the operation state determination means 110.

  FIG. 9 is a flowchart according to the present embodiment. FIG. 10 is an explanatory diagram based on the flowchart, wherein (A) is a schematic diagram of the piston, and (B) is a timing chart during the compression self-ignition operation.

  First, referring to FIG. 9, in the above configuration, the driving state is determined by the driving state determination means 110 (step S20), and the electromagnetic valves 79a to 279a are driven according to the determined driving state. The valve timing is adjusted according to the operation region (step S21). In step S21, the valve opening timing of each port 24a, 24b is determined according to the operating state, as shown in Table 1. As a result, during normal operation, the front intake valve 40 is driven by the large lift intake cam 43b, and the intake valve 40 is moved from the first half of the intake stroke as indicated by the broken line IN in FIG. The valve opens with a relatively high lift and closes in the first half of the compression stroke. In the intake stroke, the second exhaust cam 63c that performs the restart valve operation is in a lost state due to the lost motion.

  On the other hand, in the compression self-ignition operation region A, when it is determined that the load is low, the large lift intake cam 43b performs lost motion, and the front intake valve 40 is small lifted by the cam 43a in the first half of the intake stroke. The valve is opened and closed during the intake stroke. On the other hand, as shown in FIG. 10 (B), the front exhaust port 24b opens from the middle of the intake stroke and closes at the beginning of the compression stroke as hydraulic oil is supplied to the hydraulic fluid circuit 279. To do. On the low load side, the rear intake valve 40 performs a so-called restart valve operation that opens from the middle of the intake stroke and closes in the first half of the compression stroke. On the high load side, the restart valve cam 43c is lost. Due to the motion, the valve remains closed.

  As a result, as shown in FIG. 10A, the first intake valve opening IN1 by the front intake valve 40 first introduces fresh air into the cylinder 24, and then the restart valve operation by the front exhaust valve 60. Thus, burnt gas is introduced in the latter half of the intake stroke. Furthermore, the rear intake valve 40 that restarts at the low load side introduces more fresh air to the combustion chamber 26 side than the burned gas, and stratification by these gases is promoted in the cylinder.

  Next, it is determined whether or not the determined operation state is the compression self-ignition operation region indicated by A in FIG. 7 (step S22).

  If the operation region is the compression self-ignition operation region A, the VCT control unit 121 indexes the retard amount of the VCT 42 and the advance amount of the VCT 64 from the VCT control map 111 stored in the ECU 100 (step S23). Both VCTs 42 and 64 are driven based on the indexed values (step S24).

  Next, it is determined whether or not the operation state is in a low load operation region (step S25). If it is determined in step S25 that the vehicle is in the low load operation region, the ignition control means 124 determines whether or not the ignition assist timing has been reached (step S26). The ignition circuit 29a is driven to spark the spark plug 29 before the ignition timing of compression self-ignition (step S27). As described above, on the low load side in the compression self-ignition operation region A, as shown in FIG. 10B, the resuming valve operation of the intake valve 40 on the rear side causes the ignition plug 29 around the combustion chamber to Fresh air is unevenly distributed. Thus, in combination with the increase in the in-cylinder temperature due to the previously introduced burned gas, it is possible to reliably prevent misfire by executing the ignition assist in steps S26 and S27.

  After driving the spark plug 29, the ECU 100 determines whether or not a stop condition for the engine 10 is satisfied (step S28). If it is satisfied, the process is terminated. Return to.

  If it is determined in step S22 that the region is not the compression self-ignition operation region, operation in the normal mode is executed (step S29), and the process proceeds to step S28. In step S25, even in the compression self-ignition operation region, if the operation region is on the high load side, the ignition assist is not executed, and conversely, the restart valve operation of the intake valve 40 is prohibited (step S25). S30), the process proceeds to step S28.

  As described above, in the present embodiment, the intake port 24a that is opened in the intake stroke in the predetermined operation region of the engine 10, that is, the compression self-ignition operation region A, as indicated by IN1 in FIG. As shown by EX2 in FIG. 10 (B), the exhaust valve 60 is restarted during the intake stroke, so that fresh air is first introduced into the cylinder and then into the cylinder. Burned gas recirculates. At this stage, the burned gas forms a swirl in a predetermined direction on the upper layer of fresh air from the intake port 24a that is first opened in the intake stroke, and the cylinder is stratified in a state of being unevenly distributed around the spark plug 29. Here, in the present embodiment, as indicated by IN2 in FIG. 10B, the intake valve 40 restarts and the exhaust valve 60 performs the restart valve operation from the latter stage of the intake stroke to the first stage of the compression stroke. However, since the intake valve 40 opens in the middle of the first valve opening period and closes in the middle of the valve opening period of the intake valve 40 in which the resuming valve operation is performed, the resuming valve operation of the intake valve 40 causes an operation as shown in FIG. Then, fresh air is supplied to the upper layer of the stratified burned gas and stratified, and the fresh air by the restart valve operation is filled around the spark plug 29. As a result, the ignition plug 29 is driven before ignition, thereby providing an ignition assist function and reliably igniting the air-fuel mixture in a relatively lean state even when the in-cylinder temperature is low. Is possible.

  Further, in the present embodiment, a plurality of sets of intake ports 24a and intake valves 40 are provided, and the valve opening / closing control means 123 opens one intake valve 40 in the intake stroke, and performs a restart valve operation on another intake valve 40. Thus, the intake valve 40 is controlled. For this reason, in the present embodiment, the opening timing of the intake valve 40 can be easily multistaged.

  In the present embodiment, a plurality of intake ports 24a and exhaust ports 24b are arranged on the opposite sides of the longitudinal axis L of the cylinder 24 with the spark plug 29 as the center, and an intake valve 40 is provided for each intake port 24a. The exhaust valve 60 is provided for each of the exhaust ports 24b, and the valve opening / closing control means 123 causes one of the plurality of exhaust valves 60 to perform the restart valve operation, and the first in the compression self-ignition operation region A. At the intake valve opening timing, the intake valve 40 and the exhaust valve 60 are controlled so as to open only the intake valve 40 of the intake port 24a that flows out the intake air in a direction that weakens the swirl flow generated by the restart valve operation of the one exhaust valve 60. To do. Therefore, in the present embodiment, in the compression self-ignition operation region A, fresh air is introduced into the cylinder in a direction that disturbs the swirl by the exhaust valve 60, so that mixing of fresh air and burned gas is promoted. The As a result, particularly on the low load side, the in-cylinder temperature rises rapidly, and in combination with the action of the ignition assist, it becomes possible to reliably perform the compression self-ignition without remaining unburned in a lean state.

  In the present embodiment, the valve opening / closing control means 123 advances the valve opening timing of the exhaust valve 60 that performs the restart valve operation toward the low load side. For this reason, in this embodiment, as the valve opening timing of the exhaust valve 60 that performs the resuming valve operation advances as the load decreases, the internal EGR rate increases as the load decreases in the first half of the intake stroke, increasing the in-cylinder temperature. In addition, the fresh air is introduced around the spark plug 29 by the resuming valve operation of the intake valve 40, and the compression self-ignition can be realized in a relatively lean state while increasing the in-cylinder temperature.

  In the present embodiment, as shown in Table 1, the resumption valve operation of the intake valve 40 is prohibited on the high load side in the compression self-ignition operation region A. For this reason, in the present embodiment, the burned gas by the restart valve operation of the exhaust valve is stratified in a state where it is unevenly distributed in the combustion chamber 26, whereby the ignition timing can be easily controlled and knocking can be prevented. . Further, in the high-load side operation region, particularly in the engine low-speed region, the effective compression ratio is increased by prohibiting the restart valve operation of the intake valve 40, thereby increasing the ignition performance (details). Has a high potential for ignition performance due to the fact that the temperature of burned gas is increased by operation on the high load side, the gas temperature in the cylinder is increased, and the reduction of the effective compression ratio is suppressed. Thus, even if burned gas is supplied to the upper layer of the combustion chamber 26 by the resuming valve operation of the exhaust valve 60, there is no risk of misfire, and the ignition timing can be easily controlled. That is, the ignition timing can be easily controlled by adjusting the ignition timing and adjusting the ignition assist timing.

  The above-described embodiments are merely examples of preferred specific examples of the present invention, and the present invention is not limited to the above-described embodiments.

  FIG. 11 is a timing chart according to another aspect of the present invention, where (A) is at a high load and (B) is at a low load. FIG. 12 is a schematic plan view showing the structure of one cylinder of the engine body according to the embodiment of FIG. 11 and the intake and exhaust valves provided for the cylinder.

  11A and 12, in this embodiment, the valve of the front intake valve 40 in the valve operation switching mechanism 70 provided in the intake system 30 in the configuration of FIGS. 1 to 6 described above. The operation switching mechanism 70 is composed of a normal tappet 61, and the intake cam 43b is omitted from the camshaft 41. The rear intake valve 40 is configured to be driven by a cam 43b that can be lost. The valve opening / closing control means 123 is configured to perform the valve opening operation in the intake stroke at the timing shown in Table 2.

  On the other hand, in the compression self-ignition operation region A, the VCT control means 121 closes the intake valve 40 that opens in the intake stroke before the bottom dead center of the intake stroke in the high load operation region shown in FIG. As shown in FIG. 11B, the intake valve 40 and the exhaust valve 60 are controlled so that the resumption valve operation of the exhaust valve 60 is performed from the middle of the stroke to the first half of the compression stroke. As described above, the intake valve 40 is controlled to advance and the exhaust valve 60 to be retarded so that the intake valve 40 opens before the exhaust valve 60 that performs the restart valve operation.

  Further, as shown in FIG. 11 (B), the ignition control means 124 controls the spark plug 29 to execute ignition before the ignition timing on the low load side in the compression self-ignition operation region A of the engine 10. Is configured to do.

  Therefore, in the present embodiment, in the compression self-ignition operation region A, in the high load operation region, the intake valve 40 that opens in the intake stroke closes before the bottom dead center of the intake stroke and exhausts from the middle of the intake stroke to the first half of the compression stroke. Since the valve 60 performs the restart valve operation, the stratification remains in the state where the burned gas resulting from the restart valve operation is unevenly distributed in the combustion chamber 26, so that the ignition timing can be easily controlled and knocking can be prevented. It becomes possible. On the other hand, on the low load side, based on the setting of the high load operation region, the intake valve 40 is advanced so that the intake valve 40 opens before the exhaust valve 60 that performs the restart valve operation, and the exhaust valve 60 is delayed. Therefore, stratification in the cylinder is promoted with fresh air unevenly distributed in the combustion chamber 26. Therefore, it becomes possible to control the stratified gas around the spark plug 29 according to the operating state and obtain a suitable compression self-ignition characteristic. In this state, since the ignition plug 29 performs ignition before the ignition timing, it is possible to reliably ignite the air-fuel mixture in the cylinder in a relatively lean state even when the temperature in the cylinder is low. become.

  In embodying the configuration of FIGS. 1 to 6, as shown in FIG. 13, another intake port 24 c is provided between the two intake ports 24 a and 24 a arranged in the front and rear and connected to the camshaft 41 a. You may employ | adopt the structure which drives an intake valve with the rocker arm 41c.

  It goes without saying that various modifications can be made within the scope of the claims of the present invention.

1 is a configuration diagram showing a schematic configuration of a spark ignition type 4-cycle engine according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a structure of one cylinder of the engine according to FIG. 1 and an intake valve and an exhaust valve provided for the cylinder. 1 is a schematic plan view showing the structure of one cylinder of an engine body and intake and exhaust valves provided for the cylinder. It is a disassembled perspective view of the valve operation switching mechanism provided with respect to the exhaust valve. It is front sectional drawing of the said valve operation switching mechanism. It is a top sectional view of the above-mentioned valve operation change mechanism. It is a characteristic view which shows an example of the driving | operation area | region setting for performing control according to the driving | running state in the engine which concerns on embodiment of FIG. It is a schematic plan view showing the flow of fresh air and burned gas during the restart valve operation in one cylinder of the engine body, (A) when the load is low and (B) when the load is high. It is a flowchart concerning this embodiment. It is explanatory drawing based on the flowchart, (A) is a schematic diagram of a piston, (B) has shown the timing chart at the time of compression self-ignition operation. It is a timing chart which concerns on another aspect of this invention, (A) is at the time of high load, (B) is at the time of low load. FIG. 12 is a schematic plan view showing the structure of one cylinder of the engine body according to the embodiment of FIG. 11 and the intake and exhaust valves provided for the cylinder. FIG. 6 is a schematic plan view showing a structure of one cylinder of an engine body and an intake valve, an exhaust valve and the like provided for the cylinder in yet another embodiment of the present invention.

Explanation of symbols

A Compression self-ignition operation region B Spark ignition operation region 10 Spark ignition type 4-cycle engine 20 Engine body 24 Cylinder 24a Intake port 24b Exhaust port 25 Piston 26 Combustion chamber 29 Spark plug 30 Intake system 40 Intake valve 50 Exhaust system 60 Exhaust valve 70 Valve operation switching mechanism (an example of components of valve opening / closing control means)
79, 179 Hydraulic oil circuit (an example of components of valve opening / closing control means)
79a, 179a Solenoid valve (an example of components of valve opening / closing control means)
101 CPU
110 Operation state determination means 120 Combustion control means 121 VCT control means 123 Valve opening / closing control means 124 Ignition control means

Claims (6)

A cylinder that forms a combustion chamber at the top, a spark plug that is disposed in the center of the combustion chamber, an intake port and an exhaust port that communicate with the combustion chamber, and an intake valve and an exhaust port that are provided in the intake port A spark ignition type four-cycle, in which a burned gas is recirculated into the cylinder by a resuming valve operation that opens the exhaust valve in an intake stroke and a compression self-ignition operation is performed in a predetermined operating region of the engine. An engine,
An operating state determining means for determining the operating state of the engine;
Valve opening / closing control means for controlling the opening / closing timing of the intake valve and the exhaust valve based on the determination of the operating state determination means;
Ignition control means for controlling the ignition timing of the spark plug based on the determination of the operating state determination means, and the valve opening / closing control means comprises:
In the predetermined operating region, the intake valve that is opened in the first half of the intake stroke is closed before the intake bottom dead center, and the intake valve is restarted from the second half of the intake stroke to the first half of the compression stroke. The intake valve and the exhaust valve are controlled so that the operating exhaust valve is opened in the middle of the first valve opening period of the intake valve and is closed in the middle of the valve opening period of the intake valve that operates as a restart valve.
The ignition control means is a spark ignition type characterized in that, in the predetermined operating region, on the low load side, the ignition plug is controlled so as to execute ignition before a presumed ignition timing. 4-cycle engine. The spark ignition type four-cycle engine according to claim 1,
Provide multiple sets of intake ports and intake valves,
The spark opening type four-cycle engine is characterized in that the valve opening / closing control means controls the intake valve so that one intake valve is opened in an intake stroke and a resumption valve operation is executed by another intake valve. . The spark ignition type four-cycle engine according to claim 1 or 2,
Centering on the spark plug, with respect to the longitudinal axis of the cylinder, a plurality of intake ports and exhaust ports are arranged on opposite sides, an intake valve is provided for each intake port, and an exhaust valve is provided for each exhaust port.
The valve opening / closing control means causes one of a plurality of exhaust valves to perform a restart valve operation, and is generated by a restart valve operation of the one exhaust valve at an initial intake valve opening timing in the predetermined operation region. A spark ignition type 4-cycle engine characterized by controlling an intake valve and an exhaust valve so as to open only an intake valve of an intake port through which intake air flows out in a direction to weaken the swirling flow. The spark ignition type four-cycle engine according to any one of claims 1 to 3,
The spark ignition type four-cycle engine is characterized in that the valve opening / closing control means advances the valve opening timing of the exhaust valve that performs the restart valve operation toward the low load side. The spark ignition type four-cycle engine according to any one of claims 1 to 4,
The spark ignition type four-cycle engine characterized in that the valve opening / closing control means prohibits the resuming valve operation of the intake valve on the high load side in the predetermined operation region. A cylinder that forms a combustion chamber at the top, a spark plug that is disposed in the center of the combustion chamber, an intake port and an exhaust port that communicate with the combustion chamber, and an intake valve and an exhaust port that are provided in the intake port A spark ignition type four-cycle, in which a burned gas is recirculated into the cylinder by a resuming valve operation that opens the exhaust valve in an intake stroke and a compression self-ignition operation is performed in a predetermined operating region of the engine. An engine,
An operating state determining means for determining the operating state of the engine;
Valve opening / closing control means for controlling the opening / closing timing of the intake valve and the exhaust valve based on the determination of the operating state determination means;
Ignition control means for controlling the ignition timing of the spark plug based on the determination of the operating state determination means, and the valve opening / closing control means comprises:
In the predetermined operation region, in the high load operation region, the intake valve that is opened in the intake stroke is closed before the bottom dead center of the intake stroke, and the exhaust valve is restarted from the middle of the intake stroke to the first half of the compression stroke. The intake valve and the exhaust valve are controlled at the same time, and as the operating region becomes a low load side, the intake valve is advanced so that the intake valve opens before the exhaust valve performing the restart valve operation, and the exhaust valve is delayed. It is controlled to make it horn,
The spark control means is a spark that controls the spark plug so that ignition is performed before a presumed ignition timing on the low load side in the predetermined operating region of the engine. Ignition type 4-cycle engine.

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