JP2007154858A - Spark ignition type gasoline engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve compression self-ignition operation in as wide operation zone as possible by using a cam fixing a valve opening angle. <P>SOLUTION: This spark ignition type gasoline engine is provided with the cams provided on an intake valve and an exhaust valve to open a valve corresponding in a partial load operation zone at the valve opening angle fixed to less than 180°, a variable valve timing mechanism for changing opening and closing timing of the intake valve and the exhaust valve through each cam, and a control means for controlling this variable valve timing mechanism. The control means sets the closing timing of the intake valve to a part in the vicinity of intake bottom dead center in a light load operation zone and sets a crank angle CA<SB>EX</SB>from the valve closing timing of the exhaust valve to intake top dead center to increase it more than a crank angle CA<SB>IN</SB>from the intake top dead center to the valve opening timing of the intake valve and the closing timing of the exhaust valve to the time advanced by considerable amount more than the intake top dead center. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a spark ignition gasoline engine.

In general, when performing premixed compression self-ignition combustion (HCCI) (hereinafter referred to as “compression self-ignition” in this specification), as shown in Patent Document 1, an exhaust valve is used in a predetermined operation region. A technique (so-called negative overlap) is known in which the burned gas remains in the combustion chamber by changing the valve closing timing of the intake valve and the valve opening timing of the intake valve. Such compression self-ignition operation is a technique for reducing NOx or pumping loss. In particular, in order to reduce the pumping loss in the operation region where the compression self-ignition operation is performed, Patent Document 1 is configured to remove the throttle valve and adjust the air amount at the closing timing of the intake valve and the exhaust valve. Yes.
JP-A-10-266878

  In realizing the compression self-ignition operation as described above, an extremely light load operation is required in order to reduce the cost and expand the operating range as much as possible by using a cam whose valve opening period is fixed at a predetermined crank angle. In a region (an operation region that is as close as possible to idling), rapid combustion is required, while at high loads, slow combustion is required to prevent knocking. However, in the past, from the viewpoint of reducing pumping loss, the interval between the closing timing of the exhaust valve and the intake top dead center and the timing from the intake top dead center to the timing of opening the intake valve are set evenly at least on the low load side. Therefore, the effective opening ratio to achieve compression self-ignition in the extremely light load operation region, the EGR amount to increase the in-cylinder temperature, and the in-cylinder pressure are set to a constant valve opening angle. It was difficult to secure with a fixed cam.

  On the other hand, on the high load side, since the throttle is fully open or close to full open, if a cam with a fixed valve opening angle is used, the cylinder pressure, cylinder Since adjustment to lower the internal temperature is required, knocking cannot be sufficiently prevented, and the compression self-ignition operation is limited to the low and medium load operation region.

  The present invention has been made in view of the problems as described above, and realizes compression self-ignition operation in the widest possible operation region by using a cam with a fixed valve opening angle, thereby reducing NOx. It is another object of the present invention to provide a spark ignition gasoline engine capable of reducing pumping loss.

  In order to solve the above problems, the present invention changes the valve closing timing of the exhaust valve before the intake top dead center at least in the partial load operation region of the engine and sets the valve opening timing of the intake valve after the intake top dead center. A spark-ignition gasoline engine that performs compression self-ignition operation by causing burnt gas to remain in the combustion chamber by changing, and is provided in each of the intake valve and the exhaust valve, and corresponding valves in the partial load operation region For opening and closing the valve at a valve opening angle fixed to less than 180 °, a variable valve timing mechanism for changing the opening and closing timing of the intake valve and the exhaust valve via each cam, and controlling the variable valve timing mechanism A control means configured to set an intake valve closing timing near an intake bottom dead center in an extremely light load operation region, and to set an exhaust valve closing timing. The exhaust valve closing timing is advanced by a considerable amount from the intake top dead center so that the crank angle from the intake top dead center to the intake top dead center is larger than the crank angle from the intake top dead center to the intake valve opening timing. In addition to setting the timing, on the high load side, the exhaust valve closing timing is retarded toward the intake top dead center, and the intake valve closing timing is set to be shifted from the intake bottom dead center by a predetermined amount. This is a spark ignition type gasoline engine. In this aspect, since the intake valve and the exhaust valve are opened and closed by the cam whose valve opening angle is fixed to less than 180 ° in the partial load operation region, the configuration is inexpensive. In addition, in an extremely light load operation region as close as possible to idling, by adopting a cam whose valve opening angle is fixed to less than 180 ° by setting the closing timing of the intake valve close to the intake bottom dead center. Together, it is possible to ensure a high effective compression ratio by preventing the intake valve opening period from becoming too short, and the exhaust valve closing timing is set to a time advanced by a considerable amount from the intake top dead center. Since the crank angle from the exhaust valve closing timing to the intake top dead center is set larger than the crank angle from the intake top dead center to the intake valve opening timing, as described above, a high effective compression ratio A sufficient amount of EGR can be ensured while maintaining. As a result, even in the extremely light load operation region, it is possible to quickly increase the in-cylinder temperature and the in-cylinder pressure and realize the compression self-ignition operation with high fuel efficiency. On the other hand, on the high load side, the exhaust valve closing timing is retarded toward the intake top dead center, and the intake valve closing timing is set to be shifted from the intake bottom dead center by a predetermined amount, thereby reducing the EGR amount. In addition, the effective compression ratio can be lowered, and the slow combustion capable of preventing knocking can be realized.

  In a preferred aspect, the control means is configured such that, on the high load side, the crank angle from the exhaust valve closing timing to the intake top dead center is substantially equal to the crank angle from the intake top dead center to the intake valve open timing. The closing timing of the intake valve is advanced with respect to the intake bottom dead center. In this mode, when reducing the effective compression ratio on the high load side, the opening timing of the intake valve and the closing timing of the exhaust valve are substantially symmetrical with respect to the intake top dead center, thus reducing the pumping loss. In addition, fuel efficiency can be improved.

  As described above, according to the present invention, in an extremely light load operation region, a high effective compression ratio is ensured by preventing the intake valve opening period from becoming too short, and rapid combustion by compression self-ignition is achieved with high fuel efficiency. Since it is possible to achieve slow combustion that can prevent knocking on the high load side, the operating range in which compression self-ignition operation can be performed is as high as possible from the extremely light load operating range. It can be expanded to the load side, and there is a remarkable effect that compression self-ignition operation can be realized in a wide range of operation, and NOx can be reduced and pumping loss can be reduced.

  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 gasoline engine 10 according to an embodiment of the present invention. FIG. 2 shows one cylinder of an engine body 20 according to FIG. 6 is a schematic sectional view showing the structure of the intake valve 40 and the exhaust valve 60 and the like. 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 gasoline engine 10 includes a cylinder block 22 that rotatably supports a crankshaft 21 and a cylinder head 23 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 SW1 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.

  An airflow sensor SW2 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.

  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, each intake valve 40 and each exhaust valve 60 are configured to be driven by valve operating mechanisms 41 and 61 equipped with VVLs 42 and 62 having a so-called lost motion function. The valve mechanisms 41 and 61 change the opening timings of the VVLs 42 and 62 fixed to the stems 40a and 60a of the corresponding intake valves 40 and exhaust valves 60, and the intake valves 40 and exhaust valves 60, respectively. VVT (Valable Valve Timing Mechanism) 43, 63, camshafts 44, 64 driven by the driving force of crankshaft 21 via VVT43, 63, and camshafts 44, 64 are integrated into intake air at a predetermined phase. There are two sets of intake cams 45a and 45b and exhaust cams 65a and 65b that drive the valve 40 and the exhaust valve 60 in different phases.

  The VVLs 42 and 62 are for realizing a so-called lost motion in which the second exhaust cam 65b turns on / off the function of pushing down the stem 60a of the exhaust valve 60 at a predetermined timing. In the illustrated example, the VVL is a tappet type. It is embodied in. In addition, since the mechanism itself of VVL42 and 62 is well-known, description is abbreviate | omitted here.

  One of the intake cams 45a, 45b and the exhaust cams 65a, 65b (in the illustrated example, the intake cam 45a, the exhaust cam 65a) is at a valve opening angle CA of less than 180 ° in a so-called negative overlap operation. The intake valve 40 and the exhaust valve 60 are opened and closed, and the other (in the illustrated example, the intake cam 45b and the exhaust cam 65b) is opened at a valve opening angle of 180 ° or more (in the illustrated example, the intake cam 45b and the exhaust cam 65b). The valve opening angle CA of the valve 40 is 200 ° to 230 °, and the valve opening angle CA of the exhaust valve 60 is 180 ° to 200 °. The intake valve 40 and the exhaust valve 60 are opened and closed, respectively. is there.

  The hydraulic oil circuits 46 and 66 are connected to the VVL 42 of the intake valve 40 and the VVL 62 of the exhaust valve 60, respectively. The hydraulic oil circuits 46 and 66 are controlled by electromagnetic valves 47 and 67. ing. When the supply of hydraulic oil from the hydraulic oil circuits 46 and 66 is stopped by the control of the control unit 100 described later, the intake cam 45b and the exhaust cams 65b cause lost motion by the VVLs 42 and 62, and these cams 45b , 65b is not transmitted to the corresponding intake valves 40 and the stems 40a, 60a of the exhaust valves 60, so that the intake valves 40 and the exhaust valves 60 are exclusively driven by the intake cams 45a and the exhaust cams 65a. Accordingly, the intake valve 40 and the exhaust valve 60 are opened and closed at a valve opening angle CA of less than 180 °. On the other hand, when hydraulic fluid is supplied from the hydraulic fluid circuits 46 and 66, the lost motions of the VVLs 42 and 62 are stopped for the intake cams 45b and the exhaust cams 65b, and the driving forces of the intake cams 45b and the exhaust cams 65b are changed. As a result of transmission to the corresponding intake valves 40 and stems 40a, 60a of the exhaust valves 60, the intake valves 40 and the exhaust valves 60 are opened and closed at a valve opening angle CA of 180 ° or more as described above. Yes.

  The hydraulic oil circuits 46 and 66 are provided with electromagnetic valves 47 and 67, and the electromagnetic valves 47 and 67 are controlled by a control unit 100 as a control device.

  The VVTs 43 and 63 are, for example, steplessly changing the timing of driving the intake valves 40 and the exhaust valves 60 corresponding to the intake cams 45a and 45b and the exhaust cams 65a and 65b using a vane pump or the like. Since the detailed configuration is disclosed in Japanese Patent Application Laid-Open No. 2002-242617 previously proposed by the applicant of the present application, the detailed description thereof is omitted.

  Next, the spark ignition type 4-cycle gasoline engine 10 is provided with a control unit 100.

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

  As shown in FIG. 2, the memory 102 of the control unit 100 stores control maps, data, and programs. When the CPU 101 executes these control maps, data, and programs, as shown in FIG. An operation state determination unit 110 that determines an operation state such as an engine speed and an engine load, and a VVL control unit 120 that executes drive control of each of the VVLs 42 and 62 and VVT 43 and 63 according to the determined operation state, and VVT control. Means 140 is functionally provided. Further, the driving state determination means 110 includes a control map M1 for determining the driving state. The control map M1 is also referred to by the VVL control means 120 and the VVT control means 140, and the VVL control means 120 executes switching of the intake cam 45b and the exhaust cam 65b based on the control map M1, and the VVT control means. Reference numeral 140 is configured to control the opening and closing timing of the intake valve 40 and the exhaust valve 60 based on the control map M1. Further, the VVT control means 140 includes a VVT control map M2 for advancing / retarding the intake VVT 43 and the exhaust VVT 63. Each of the control maps M1 and M2 is stored in the memory 102 of the control unit 100.

  Various detection means such as a crank angle sensor SW1, an airflow sensor SW2, and an accelerator opening sensor SW3 are connected to the control unit 100 as input elements. On the other hand, as control elements, the actuator 36 of the throttle valve 35, the electromagnetic valves provided in the VVTs 43, 63 of the valve operating mechanisms 41, 61, the electromagnetic valves 47, 67 of the hydraulic oil circuits 46, 66 that drive the VVLs 42, 62, An ignition circuit 29a for controlling ignition by the ignition plug 29, a fuel injection valve 28, and the like are connected.

  The operating state determining means 110 detects the operating state of the engine from the crank angle sensor SW1, the accelerator opening sensor SW3, etc., and based on the control map M1, based on the signals from the crank angle sensor SW1, the accelerator opening sensor SW3, etc. It is determined which operating region the engine operating state (engine speed and engine load) to be examined is in.

  FIG. 4 is a characteristic diagram showing an example of operation region setting for performing control according to the operation state according to the present embodiment.

Referring to FIG. 4, the control map M1 is configured based on the operation characteristics shown in FIG. In the operation characteristics shown in FIG. 4, in the partial load operation region where the engine speed N is equal to or less than the predetermined engine speed N1, the compression self-ignition operation region D for executing the compression self-ignition operation is set, and in the remaining region, A spark ignition operation region SI for executing a forced ignition operation by spark ignition is set. Further, the compression-ignition operation region D, the very-light-load operation region D ₀ near the idle operation region as possible, the very-light-load operation region D ₀ somewhat operating regions of high predetermined low load side of the load D than ₁ and an operation region D ₂ on the high load side exceeding the predetermined low load.

  Next, referring to FIG. 2, the VVL control unit 120 supplies hydraulic oil to the hydraulic oil circuits 46 and 66 when the operation state determined by the operation state determination unit 110 is the compression self-ignition operation region D. By stopping the intake cam 45b and the exhaust cams 65b, the valve opening control is performed so that the valve opening angle CA of each of the intake valves 40 and the exhaust valves 60 is less than 180 ° (see FIGS. 5 and 6). In other spark ignition operation regions SI, hydraulic oil is supplied to the hydraulic oil circuits 46 and 66 to transmit the driving force of the intake cam 45b and the exhaust cams 65b to the corresponding intake valves 40 and exhaust valves 60. Each intake valve 40 and exhaust valve 60 is configured to be opened and closed at a valve opening angle CA of 180 ° or more (see FIG. 7).

  The VVT control means 140 determines the opening / closing timing of the intake valve 40 and the exhaust valve 60 according to the determination of the operation state determination means based on the control map M1 and the control mode defined in the control map M2.

In the present embodiment, as apparent from FIG. 4, in the very-light-load operation region D _0, is configured to perform a compression-ignition operation. In order to execute such control, the valve opening timing shown in FIG. 5 is set in the control map M2.

FIG. 5 is a timing chart showing the opening / closing timing of the intake valve 40 and the exhaust valve 60 in the extremely light load operation region D ₀ in the present embodiment.

Referring to FIG. 5, when the operation region is the extremely light load operation region D ₀ , VVT control means 140 sets the closing timing of intake valve 40 near the bottom dead center of intake and closes the closing timing of exhaust valve 60. The closing timing of the exhaust valve 60 is set to the intake top dead center so that the crank angle CA _EX from the intake top dead center to the intake top dead center becomes larger than the crank angle CA _IN from the intake top dead center to the opening timing of the intake valve 40. It is set at a time when it is advanced by a considerable amount. With such a setting, in combination with the opening angle CA of each intake valve 40 and each exhaust valve 60 being set to less than 180 ° (130 ° in the illustrated example), first, By setting the intake valve 40 in the intake stroke in the vicinity of the intake bottom dead center, it is possible to ensure an effective compression ratio while preventing the valve opening period of the intake valve 40 from becoming too short. In addition, a certain amount of pumping loss is caused by securing a predetermined amount (50 ° in the illustrated example) of the crank angle CA _IN from the intake top dead center to the opening timing of the intake valve 40, but more demanding is required. It is possible to ensure high internal EGR and to increase the in-cylinder temperature and the in-cylinder pressure rapidly, thereby contributing to rapid combustion. Further, the valve opening timing of the exhaust valve 60 is such that the crank angle CA _EX from the valve closing timing of the exhaust valve 60 to the intake top dead center is the crank angle CA from the intake top dead center to the valve opening timing of the intake valve 40. Since it is advanced so as to be larger than _IN, the crank angle CA _EX for securing the internal EGR is ensured to be large (100 ° in the illustrated example), so that a sufficient internal EGR is secured, and the in-cylinder It is possible to contribute to an increase in temperature.

FIG. 6 is a timing chart showing the opening / closing timing of the intake valve 40 and the exhaust valve 60 in the high load operation region D ₂ in this embodiment.

Referring to FIG. 6, if the operating range is a high-load operation region D _2, VVT controller 140 retard the closing timing of the exhaust valve 60 towards the intake top dead center (in the illustrated example, the inlet with the crank angle CA range _EX is equal to or greater than 70 °) death temae, a predetermined amount retard the closing timing of the intake valve 40 from the intake bottom dead center (in the example shown, constituted 20 °) as after intake bottom dead center Has been. Therefore, the high-load operating region D _2, together with the effective compression ratio is lowered, by the internal EGR is reduced, it is possible to realize a compression self-ignition in slow combustion. As a result, knocking can be avoided reliably, and further, it can contribute to a reduction in pumping loss.

  FIG. 7 is a timing chart showing the opening / closing timing of the intake valve 40 and the exhaust valve 60 in the spark ignition operation region SI in the present embodiment.

  Referring to FIG. 7, when the operation region is the spark ignition operation region SI, the VVT control unit 140 sets the opening timing of the intake valve 40 slightly before the intake top dead center, and opens the exhaust valve 60. Set the valve timing slightly before exhaust bottom dead center. As described above, when the operation region is the spark ignition operation region SI, the VVL control unit 120 supplies the operation oil to the operation oil circuits 46 and 66 to correspond to the driving force of the intake cam 45b and each exhaust cam 65b. The intake valve 40 and the exhaust valve 60 are communicated to each other, and the intake valve 40 and the exhaust valve 60 are opened at an opening angle CA of 180 ° or more (in the illustrated example, the opening angle CA of the intake valve 40 is 200 ° to 230 °, The opening / closing control is performed when the valve opening angle CA of the valve 60 is 180 ° to 200 °. As a result, the valve closing angles CA of the intake valve 40 and the exhaust valve 60 are immediately after the intake bottom dead center and immediately after the intake top dead center.

Note that the control map M2, in the low load operating region D ₁ of the period from very-light-load operation region D ₀ to a high-load operation region D _2, the intake valve 40 as the high-load side, the exhaust valve 60 in each of the ratios The retard amount is set steplessly so as to retard.

As described above, in the present embodiment, the corresponding intake valve 40 and exhaust valve 60 in the compression self-ignition operation region D are opened and closed by the cams (the intake cam 45a and the exhaust cam 65a) fixed to less than 180 °. Therefore, it becomes an inexpensive configuration. In addition, in the extremely light load operation region D ₀ that is almost as idle as possible, the cam (with the valve opening angle CA fixed to less than 180 °) is set by setting the closing timing of the intake valve 40 in the vicinity of the intake bottom dead center. In combination with the adoption of the intake cam 45a and the exhaust cam 65a), a high effective compression ratio can be ensured so that the valve opening period of the intake valve 40 is not too short, and the closing timing of the exhaust valve 60 is also achieved. Is set to a time advanced by a considerable amount from the intake top dead center, and the crank angle CA _EX from the closing timing of the exhaust valve 60 to the intake top dead center is set between the intake top dead center and the opening timing of the intake valve 40. since it is set larger than the crank angle CA _iN, as described above, it is possible to secure a sufficient amount of EGR while maintaining high effective compression ratio. As a result, even in the extremely light load operation region D ₀ , it is possible to quickly increase the in-cylinder temperature and the in-cylinder pressure and realize the compression self-ignition operation with high fuel efficiency. On the other hand, on the high load side, the closing timing of the exhaust valve 60 is retarded toward the intake top dead center, and the closing timing of the intake valve 40 is set to be shifted from the intake bottom dead center by a predetermined amount. And the effective compression ratio can be reduced, and slow combustion that can prevent knocking can be realized.

In this embodiment also, the control unit 100, the VVL control unit 120, VVT control unit 140, in the high load side, from the intake top dead center crank angle CA _EX of the intake top dead center from the closing timing of the exhaust valve 60 it is intended to advance against the intake bottom dead center the closing timing of the intake valve 40 so that the crank angle CA _iN until the opening timing of the intake valve 40 are substantially equal. For this reason, in this embodiment, when reducing the effective compression ratio on the high load side, the opening timing of the intake valve 40 and the closing timing of the exhaust valve 60 are substantially symmetrical with respect to the intake top dead center. It becomes possible to reduce pumping loss and improve fuel consumption.

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

FIG. 8 is a timing chart showing opening and closing timings of the intake valve 40 and the exhaust valve 60 in the high load operation region D ₂ in another embodiment of the present invention.

Referring to FIG. 8, the closing timing of the intake valve 40 when the operating region is a high-load operation region D ₂ as a method for a predetermined amount of retard from intake bottom dead center, advanced the opening timing of the intake valve 40 ( in the illustrated example, it is set) to 30 ° crank angle CA _iN to opening timing from the intake top dead center. Also in this aspect, the VVT control means 140 retards the closing timing of the exhaust valve 60 toward the intake top dead center (in the illustrated example, the crank angle CA _EX before the intake top dead center is in the range of 70 ° or more). Therefore, similarly to the embodiment of FIG. 6, it is possible to reduce the effective compression ratio and reduce the internal EGR, thereby achieving slow combustion.

Note that the embodiment of the control map M2 of FIG. 8, in the low load operating region D ₁ of the period from very-light-load operation region D ₀ to a high-load operation region D _2, the intake valve 40 as the high load side is advanced The advance amount and the retard amount are set steplessly so that the exhaust valve 60 is retarded.

  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 gasoline 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 characteristic view which shows an example of the control map M1 of the driving | operation area | region setting for performing control according to the driving | running state which concerns on this embodiment. In this embodiment, it is a timing chart which shows the opening / closing timing of an intake valve and an exhaust valve in an extremely light load operation area | region. In this embodiment, it is a timing chart which shows the opening-and-closing timing of an intake valve and an exhaust valve in a high load operation area. In this embodiment, it is a timing chart which shows the opening / closing timing of the intake valve and the exhaust valve in the spark ignition operation region. In another embodiment of the present invention, it is a timing chart which shows the opening-and-closing timing of an intake valve and an exhaust valve in a high load operation field.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Spark ignition type 4 cycle gasoline engine 20 Engine main body 24 Cylinder 30 Intake system 40 Intake valve 41, 61 Valve mechanism 42 VVT (variable valve timing mechanism)
44a Camshaft 45a, 45b Intake cam 46 Hydraulic oil circuit 47 Solenoid valve 50 Exhaust system 60 Exhaust valve 65a, 65b Exhaust cam 67 Solenoid valve 100 Control unit 110 Operating state determination means 120 VVL control means 140 VVT control means CA Valve opening angle CA _EX crank angle CA _IN crank angle D Compression self-ignition operation area (partial load operation area)
D ₀ Extreme light load operation region D ₁ Low load operation region D ₂ High load operation region M1 Control map M2 Control map SW1 Crank angle sensor SW2 Airflow sensor SW3 Accelerator opening sensor

Claims (2)

By changing the exhaust valve closing timing before the intake top dead center and changing the intake valve opening timing after the intake top dead center at least in the partial load operation region of the engine, A spark ignition type gasoline engine that performs compression self-ignition operation while remaining in
A cam for opening and closing the corresponding valve in the partial load operation region at a valve opening angle fixed at less than 180 °, provided on each of the intake valve and the exhaust valve;
A variable valve timing mechanism capable of changing the opening and closing timing of the intake valve and the exhaust valve via each cam;
Control means for controlling the variable valve timing mechanism, the control means,
In the extremely light load operation region, the intake valve closing timing is set near the intake bottom dead center, and the crank angle from the exhaust valve closing timing to the intake top dead center is set to the intake valve opening timing from the intake top dead center. The exhaust valve closing timing is set to a time that is considerably advanced from the intake top dead center so that it becomes larger than the crank angle until
On the high load side, the ignition timing is set so that the closing timing of the exhaust valve is retarded toward the intake top dead center and the closing timing of the intake valve is shifted by a predetermined amount from the bottom dead center of the intake air. Type gasoline engine. The spark ignition gasoline engine according to claim 1,
On the high load side, the control means closes the intake valve so that the crank angle from the exhaust valve closing timing to the intake top dead center is substantially equal to the crank angle from the intake top dead center to the intake valve open timing. A spark-ignition gasoline engine characterized by advancing timing with respect to intake bottom dead center.

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