JP4483643B2 - Multi-cylinder engine controller - Google Patents

Description

  The present invention relates to a control device for a multi-cylinder engine, and more particularly to a control device for a multi-cylinder engine provided with a pulse generator that generates an impulse (a high-pressure pressure wave introduced into a cylinder).

  Conventionally, various technologies for improving volumetric efficiency have been developed in a control device for a multi-cylinder engine provided with a surge tank of an intake manifold and a branch pipe branched from the surge tank and connected to an intake port of each cylinder. .

  For example, Patent Document 1 discloses a technique in which a plurality of intake passages having different passage lengths are provided for each intake port, and these intake passages are selectively communicated with a surge tank by a switching valve.

  On the other hand, Non-Patent Document 1 discloses a technique for increasing torque in a low operation region by impulse. In that configuration, an electromagnetic valve that strokes in the direction of the path of the branch pipe is provided in the middle of the branch pipe of the intake manifold, and until the middle of the intake stroke, the solenoid valve is closed to form a negative pressure, and the bottom dead center of the intake stroke A configuration is disclosed in which air is rapidly supplied into a cylinder by opening a solenoid valve in the vicinity.

Patent Document 2 and Non-Patent Document 2 disclose a device that generates a pulse using a flap valve as a device that generates an impulse.
JP 2003-41939 A JP 2000-248946 A Impulse charging boosts torque at low speed, Findlay Publications “European Automotive Design” February 2004 issue Development of an Actuator for a Fast Moving Flap for impulse Charging, Findlay Publications “European Automotive Design” January 2003 issue

  By the way, when the pulse generator is operated, in the first half of the intake stroke, while the pulse generator is closed, the air in the cylinder expands and the temperature decreases. For this reason, as a result of the air in the cylinder in the intake stroke absorbing ambient heat, the temperature in the cylinder becomes very high during the compression stroke. Therefore, if the pulse generator is operated in an operating state such as during low rotation and high load, knocking is likely to occur due to the pulse generator, which may hinder practical use.

  The present invention has been made in view of the above-described problems, and it is an object of the present invention to provide a control device for a multi-cylinder engine that can maintain an operation state in which knocking hardly occurs even when a pulse generator is used.

In order to solve the above problems, the present invention relates to an intake pipe that supplies air to each intake port of a plurality of cylinders, and an intake stroke that is open during the intake stroke during the valve opening period of each intake port, corresponding to the intake stroke of each cylinder. In a control device for a multi-cylinder engine having a pulse generator for generating pressure waves in the cylinder, a variable valve timing mechanism capable of changing the valve opening timing of the pulse generator and detecting the operating state of the engine And a control means for driving and controlling the pulse generator and the variable valve timing mechanism based on the detection of the operating condition detecting means. The control means increases the in-cylinder temperature during the compression stroke of the engine. when in Kitashi easy operation state knocking suppresses expansion of the cylinder air in the opening timing of the pulse generator, to suppress an increase in in-cylinder temperature during a compression stroke Te To a control apparatus for a multi-cylinder engine, characterized in that for advancing the opening timing of the pulse generator. In this aspect, in the operation region in which it is determined that knocking is likely to occur when the pressure wave is generated by the pulse generator, the valve opening timing of the pulse generator is advanced by the control means. The expansion of in-cylinder air at the valve closing timing is also alleviated. As a result, an excessive increase in the in-cylinder temperature during the compression stroke can be suppressed, and knocking can be avoided.

  In a preferred embodiment, an engine speed detecting means for detecting the engine speed is provided, and the control means advances the valve opening timing of the pulse generator as the detected engine speed increases, and knocking is performed. The valve opening characteristic of the pulse generator is shifted to the advance side as the operating state is more likely to occur. In this aspect, suitable pressure wave generation characteristics can be obtained according to the engine speed. Further, when the valve opening timing of the pulse generator is advanced according to the engine speed, the pulse generator is advanced as the operating state detected by the operating state detection means is more easily knocked, so the detected operating state Accordingly, an appropriate valve opening timing can be set in the pulse generator, so that knocking can be avoided.

  In a preferred embodiment, an octane number discriminating means for discriminating the octane number of the fuel is provided, and the control means shifts the valve opening characteristic of the pulse generator toward the advance side when the determined octane number is low than when it is high. It is. In this aspect, when the valve opening timing of the pulse generator is advanced according to the engine speed, when the octane number is low, the valve opening characteristic is shifted to the advanced angle side than when it is high. In this case, the pulse generator advances in a lower rotation region than in the case of a high octane number. Therefore, an appropriate valve opening timing can be set in the pulse generator according to the octane number of the fuel, and knocking can be avoided.

  In a preferred aspect, the control means performs split injection control of fuel in the low load operation region. In this aspect, while preventing knocking in the high load operation region, in the low load operation region, fuel atomization is promoted using the negative pressure of the pulse generator, and fuel is generated by the high flow rate of the intake air by the generated pressure wave. It is possible to take advantage of the mixing action of

  In a preferred aspect, the control means injects the first half of fuel before opening the pulse generator within the valve opening period of the intake port, and injects the second half of fuel near the opening of the pulse generator. . In this aspect, even in a so-called direct injection engine in which fuel is directly injected into the combustion chamber of the engine, it is possible to reliably promote the vaporization and atomization of the fuel and improve the mixing performance.

  As described above, according to the present invention, there is a remarkable effect that knocking due to the generated negative pressure or the like can be prevented as much as possible while using the pulse generator to the maximum extent.

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

  FIG. 1 is a right side view of a four-cycle spark-ignition multi-cylinder engine according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view taken along line AA of FIG. FIG. 3 is a perspective view schematically showing a main part of the present embodiment.

  Referring to the drawings, the engine 10 integrally includes a cylinder block 11 and a cylinder head 12 integrated on the upper portion of the cylinder block 11. The engine 10 is provided with first to fourth cylinders 12A to 12D, and a piston 4 connected to the crankshaft 3 is fitted into each of the cylinders 12A to 12D so that a combustion chamber is provided above the piston 4. 15 is formed.

  A spark plug 16 as an ignition means is fixed to the cylinder head 12 for each combustion chamber 15 of each of the cylinders 12A to 12D. Each spark plug 16 is installed such that its tip faces the corresponding combustion chamber 15 from the top.

  The cylinder head 12 is formed with an intake port 17 and an exhaust port 18 that open toward the combustion chamber 15 for each of the cylinders 12A to 12D, and an intake valve 19 is provided at the ports 17 and 18, respectively. And an exhaust valve 20 are respectively provided.

  Each intake port 17 is provided with a fuel injection valve 21. The fuel injection valve 21 incorporates a needle valve and a solenoid.

  An exhaust manifold (not shown) is connected to the exhaust port 18. An exhaust gas purification catalyst is provided in the exhaust passage downstream of the exhaust manifold assembly. This exhaust gas purification catalyst is formed of, for example, a so-called three-way catalyst in which the purification rate of HC, CO and NOx is extremely high when the air-fuel ratio of the exhaust is in the vicinity of the theoretical air-fuel ratio. As is generally known, this exhaust gas purification catalyst comprising a three-way catalyst is more effective than HC, CO, and NOx when the air-fuel ratio of the exhaust gas is near the stoichiometric air-fuel ratio (that is, the excess air ratio λ = 1). And high purification performance.

  The intake valve 19 and the exhaust valve 20 are configured to open and close the intake port 17 and the exhaust port 18 in synchronization with a predetermined phase difference by the camshafts 22 and 23 for the intake valve and the exhaust valve supported by the engine 10. Has been. The camshafts 22 and 23 are connected to a cam sprocket gear (not shown), and the cam sprocket gear receives power from a cam pulley 30 via a timing belt (not shown) (see FIG. 3). The cam pulley 30 is attached to the front surface of the engine 10 so as to be rotatable about an axis parallel to the crankshaft 3. On the other hand, an output pulley 32 attached to the front side of the engine 10 is fixed to the crankshaft 3, and both pulleys 30, 32 are configured to be synchronized with each other by a timing belt 34.

  The camshafts 22 and 23 are provided with variable valve timing mechanisms 24 and 25 that change the opening and closing timing by adjusting the rotation phase. As a result, the intake valve 19 can change the phase with respect to the crank angle.

  A knock sensor 28 is incorporated in the cylinder block 11 of the engine 10 (see FIG. 6). The knock sensor 28 is composed of a piezoelectric element that detects vibration at the time of occurrence of knocking. In the illustrated embodiment, the knock sensor 28 is a sensor for causing the ECU 100 described below to function as an octane number detecting means.

  The intake device 40 according to the present embodiment includes an intake manifold 41 fixed to a side portion of the engine 10 and a rotary valve 50 as a pulse generator or PGV (Pulse Generating Valve) built in the intake manifold 41. is doing.

  The intake manifold 41 is fixed to the engine 10 via a support member (not shown), and a surge tank 42 as a collective portion extending horizontally in the front-rear direction of the engine 10 (the direction in which the cylinders 12A to 12D are arranged) The first to fourth branch intake pipes 43A to 43D are integrally formed as intake pipes connected to the surge tank 42 and forming the intake passages PH11 to PH14 separated from each other. A throttle body 44 is fixed to the rear end portion of the surge tank 42, and a throttle valve (not shown) is built in the throttle body 44.

  The surge tank 42 is a substantially cylindrical member, and by communicating with the branch intake pipes 43A to 43D, the surge tank 42 absorbs the differential pressure of each branch intake pipe 43A to 43D, and has a function of preventing abnormal noise and sensor malfunction. To fulfill. In the present embodiment, the length SL of the surge tank 42 in the cylinder row direction is set to be shorter than the interval DL on the downstream end side in the cylinder row direction of the branch intake pipes 43A to 43D described below. (See FIG. 1).

  Each of the branch intake pipes 43A to 43D is provided for each of the cylinders 12A to 12D, and communicates the corresponding cylinders 12A to 12D with the surge tank 42 in a state of being substantially L-shaped when viewed from the front. In the illustrated embodiment, each of the branch intake pipes 43A to 43D has passage lengths of the intake passages PH11 to PH14 (in this embodiment, the length from the intake port 17 to the peripheral surface 51 of the rotary valve 50 in the surge tank 42). Are set to the same length. The length of each intake passage PH11 to PH14 is set within 500 mm.

  The rotary valve 50 is a cylindrical member, and is rotatably disposed in a state where the outer peripheral surface 51 is in sliding contact with the inner peripheral surface of the surge tank 42.

  Referring to FIG. 3, an input gear 54 </ b> A is provided concentrically at the front end portion of the rotary valve 50. The input gear 54A meshes with an output gear 54B provided concentrically with the cam pulley 30 so that power is transmitted from the crankshaft 3 at a ratio of 1: 0.5 via the output gear 54B. It has become. In other words, the rotary valve 50 is synchronized with the cam pulley 30 at a ratio of 1: 1. A pair of openings 52 and 53 are formed on the peripheral surface of the rotary valve 50 to communicate the inside of the surge tank 42 and the branch intake pipes 43A to 43D. The openings 52 and 53 are 180 degrees out of phase in the circumferential direction, and the front opening 52 is shifted upstream in the rotational direction with respect to the rear opening 53 in the axial direction. In the figure, 55 is an idler.

  In the illustrated embodiment, a rotary valve advance mechanism 56 is provided between the rotary valve 50 and the input gear 54A. The rotary valve advance mechanism 56 basically uses an input gear 54A and a rotary valve by using a rotation phase control device (see JP-A-11-107718) previously proposed by the present applicant. This is a mechanism for forming a phase difference between the rotary valve 50 and the valve opening timing of the rotary valve 50. The rotary valve advance mechanism 56 is driven and controlled by an OCV (Oil Control Valve) system 57 as shown in FIG. Further, as shown in FIG. 1, a PGV angle sensor 58 is attached to the rotary valve advance mechanism 56 in order to detect the phase of the rotary valve 50.

  The illustrated engine is an in-line four-cylinder engine, and when the cylinders are first to fourth cylinders 12A to 12D in order from the front of the engine 10, the order of reaching the intake stroke is the first cylinder 12A and the third cylinder. 12C, the fourth cylinder 12D, and the second cylinder 12B are set. As a result, when the first cylinder 12A reaches the intake stroke, the relationship between each cylinder and the stroke is as shown in Table 1.

  Therefore, in the present embodiment, the first branch intake pipe 43A and the second branch intake pipe 43B are arranged so as to be opposed to the opening 52 of the rotary valve 50 with a phase shifted downstream in the rotational direction. At the same time, the third branch intake pipe 43C and the fourth branch intake pipe 43D are arranged so as to be opposed to the opening 53 in the rotational direction upstream side and shifted in the rotational direction downstream side.

  More specifically, the second branch intake pipe 43B connected to the second cylinder 12B and the first branch intake pipe 43A connected to the first cylinder 12A are located upstream at positions where they can face the front opening 52. A third branch intake pipe 43C connected to the third cylinder 12C and a fourth branch intake pipe 43D connected to the fourth cylinder 12D are fixed to the surge tank 42 with a phase shifted by 90 ° from the side. Are fixed to the surge tank 42 at a position that can be opposed to the rear opening 53 with the phase shifted by 90 ° in order from the upstream side. Further, the first branch intake pipe 43A and the fourth branch intake pipe 43D (and hence the second branch intake pipe 43B and the third branch intake pipe 43C) are arranged in the same phase in the circumferential direction of the surge tank 42. Accordingly, in this configuration, the branch intake pipes 43A to 43D can be opened and closed at a predetermined timing regardless of the engine speed, and the branch intake pipes 43A to 43D can be made equal in length and made compact. Will contribute. As a result, the intake passages PH11 to PH14 can be shortened as much as possible, and an intake structure with high response to torque improvement can be configured. Further, as described above, the length SL of the surge tank 42 in the cylinder row direction is set to be shorter than the interval DL on the downstream end side in the cylinder row direction of each of the branched intake pipes 43A to 43D described below. (See FIG. 1), the upstream ends of the branch intake pipes 43A to 43D are converged in the cylinder row direction as compared with the downstream ends. For this reason, in this embodiment, it has the structure where the response with respect to a torque improvement becomes very high.

  FIG. 4 is an enlarged cross-sectional view of the main part of FIG.

  With reference to the figure, the diameter D of the rotary valve 50 is set larger than the cross-sectional width of each branch intake pipe 43A-43D. By rotating the rotary valve 50 in synchronization with the crankshaft 3, the time for opening the branch intake pipes 43A to 43D corresponding to the openings 52 and 53 is shortened. In addition, since the rotary valve 50 is rotated to supply air to the branch intake pipes 43A to 43D facing the peripheral surface through the openings 52 and 53 formed on the peripheral surface, air pulsation can be suppressed. The occurrence of abnormal noise is also reduced.

  Furthermore, the valve closing angle θ between the openings 52 and 53 formed in the rotary valve 50 is set to 120 °, for example. By setting the valve opening start timing to the first half of the intake stroke, the intake valve 19 Even if the intake port 17 is opened, the rotary valve 50 remains in the state of shielding the surge tank 42, so that the negative pressure is generated in the corresponding branch intake pipe 43A (˜43D) by the intake stroke until the rotary valve 50 is opened. Will occur.

  FIG. 5 is a partially enlarged view showing an essential part of FIG.

  Referring to FIGS. 4 and 5, each of the branch intake pipes 43 </ b> A to 43 </ b> D is provided with a VIS (Variable Induction System) 60 as a variable passage length system.

  The VIS 60 is a volume tube 61 as a volume portion extending in parallel with the crankshaft 3, a communication tube 62 that connects the volume tube 61 and each of the branch intake tubes 43 </ b> A to 43 </ b> D, and an open / close mechanism that opens and closes the communication tube 62. And a VIS valve 63. In the illustrated example, the volume tube 61 is a member that also functions as a communication passage that communicates each of the branched intake passages 43A to 43D. The VIS valves 63 are connected to the same drive shaft 64 and are configured to be simultaneously opened and closed by a VIS valve actuator 65 that drives the drive shaft 64.

Referring to FIG. 2, the engine 10 is provided with a pair of engine crank angle sensors 66 as engine speed detection means. Each engine crank angle sensor 66 is arranged around the crankshaft 3 with a predetermined phase difference. The engine speed is detected based on a detection signal output from one engine crank angle sensor 66, and both Based on the detection signal output from the engine crank angle sensor 66, the rotation direction and rotation angle of the crankshaft 3 are detected. Further, in order to detect the operating state of the engine 10, an engine water temperature sensor 67 for detecting the temperature of the cooling water of the engine 10, an accelerator opening sensor 68 as an engine load detecting means, and upstream of the exhaust gas purification catalyst. An O ₂ sensor 69 that is disposed and detects the oxygen amount of the exhaust gas discharged from the exhaust port 18 is provided.

  Further, an EGR system 70 for returning a part of the burned gas discharged to the exhaust port 18 to the intake port 17 is provided.

  FIG. 6 is a block diagram according to the present embodiment.

Referring to FIG. 1, ECU 100 for controlling driving of engine 10 is a unit having a microprocessor, a memory, an input unit, and an output unit. The input portion of the ECU 100 includes a knock sensor 28, a PGV angle sensor 58 for detecting the phase of the rotary valve 50, an engine crank angle sensor 66, an engine water temperature sensor 67, an accelerator opening sensor 68, and an O ₂ sensor 69 as input elements. It is connected. Further, an output portion of the ECU 100 includes an ignition plug 16, a fuel injection valve 21, variable valve timing mechanisms 24 and 25 for the intake valve 19 and the exhaust valve 20, a rotary valve advance mechanism 56 (specifically, an OCV system 57), The VIS valve actuator 65 is connected as an output element.

  Next, a control map stored in the memory of the ECU 100 will be described.

  FIG. 7 is a graph showing the relationship between the torque and the engine speed N according to this embodiment, and FIG. 8 is a graph showing the relationship between the rotary valve and the VIS valve and the torque in the low speed operation region of the engine 10.

  With reference to each figure, in this embodiment, the temperature of the cooling water detected by the engine water temperature sensor 67 is adopted as the temperature related to the in-cylinder temperature of the engine 10, and the detected temperature Wt of the engine water temperature sensor 67 is set in advance. The low temperature that is less than the predetermined temperature Wt1 is determined as cold when the engine 10 is cold, and the high temperature that is equal to or higher than the predetermined temperature Wt1 is determined as warm. The operation range of the rotary valve 50 during cold (PGV operation range during cold) It is determined in ECU 100 that R4 is wider than the operating region (warm PGV operation region) R5 of rotary valve 50 when warm. That is, as apparent from FIG. 7, when the engine 10 is warm, the operating region R5 of the rotary valve 50 is set up until the engine speed N is about 1500 rpm, whereas when the engine 10 is cold, The operating region R4 of the rotary valve 50 is expanded according to the engine load state until the engine speed N is about 2500 rpm. Accordingly, in the operation of the VIS valve 63, the timing at which the volume tube 61 is opened on the low load side is expanded to the high load side in the cold time torque τ2 than in the warm time torque τ1.

  In the present embodiment, as shown in FIG. 7, since the region R5 is defined even in the warm state and the rotary valve 50 is operated in this operation region, the vaporization mist of the fuel is separated from the improvement of the torque. It is possible to effectively use the rotary valve 50 in order to promote the conversion and improve the combustion stability.

  Further, as apparent from FIG. 8, in the illustrated embodiment, in the low speed operation region of the engine 10, the VIS valve 63 is closed and the rotary valve 50 is operated even on the high load side (region of torque τ 3 or more). Is set to As a result, in the low speed / low load area where fuel vaporization is important and in the low speed / high load area where high output performance is required, the rotary valve 50 operates to improve combustion stability and volume efficiency. On the other hand, in the low-speed / medium-load region where there is relatively little demand, the output is secured while improving fuel efficiency by the dynamic supercharging effect of the branch intake pipes 43A to 43D due to the opening of the VIS valve 63. Is configured to do.

  FIG. 9 is a graph showing the relationship between the in-cylinder pressure and the crank angle, where (A) is a cold time and (B) is a warm time. In FIG. 9, IN indicates the valve opening characteristics of the intake valve 19, and C11 and C12 indicate the valve opening characteristics of the rotary valve 50 when cold and warm, respectively. In the present embodiment, the rotary valve 50 at the most retarded angle is set to open in the second half of the intake stroke.

  Referring to FIGS. 2A and 2B, in the illustrated embodiment, the fuel injection timings Tr1 and Tr2 are individually set when the engine 10 is cold and warm.

  In the present embodiment, when cold, fuel is injected in the first half of the intake stroke before the rotary valve 50 is opened, and when warm, only near the opening timing of the rotary valve 50 (preferably immediately after opening). It is set to inject fuel.

  FIG. 10 is a timing chart showing the valve opening angle, the fuel injection timing, and the ignition timing in the so-called fast idle state after engine startup. In the figure, IN indicates the valve opening characteristic of the intake valve 19, and C10 indicates the valve opening characteristic of the rotary valve 50 in the fast idle state.

  Referring to FIG. 10, in the first idle state immediately after the cold start of engine 10, the ECU 100 performs a catalyst activation promoting operation for activating the exhaust gas purification catalyst. In order to realize this catalyst activity promotion operation, in this embodiment, the detected temperature Wt of the engine water temperature sensor 67 is adopted as the temperature related to the activation temperature of the exhaust gas purification catalyst, and this detected temperature Wt is preset. The ECU 100 is configured to discriminate a low temperature less than a predetermined temperature (catalyst activation state equivalent temperature) Wt2 as a catalyst inactive state and a high temperature equal to or higher than the catalyst activation state equivalent temperature Wt2 as an activation temperature state. Note that the activation state of the exhaust gas purification catalyst may be determined using both the water temperature detection and the determination of the elapsed time from the start of the engine, or the catalyst temperature may be directly detected. When the exhaust gas purification catalyst is in an inactive state lower than the catalyst active state equivalent temperature Wt2, the ECU 100 operates the rotary valve 50 with the most retarded angle and sets the ignition timing IG of the spark plug 16 to a predetermined retard limit. It is set to be retarded until. By operating the rotary valve 50 at the most retarded angle, fuel vaporization and atomization are promoted by the negative pressure, so that the combustion stability is improved, the retard limit of the ignition timing IG is increased, and the exhaust performance is greatly improved. It becomes possible to improve.

  Next, the fuel injection during the catalyst activation promoting operation is preferably divided into F1 and F2 in addition to the range of the cold fuel injection timing Tr1 described in FIG. . In principle, the first fuel injection timing F1 is set until the first half of the intake stroke within the valve opening period of the intake port 17, and the second fuel injection timing F2 is in the vicinity of the rotary valve 50 being opened (more details). Is preferably set to a timing at which injection is started immediately before the start of valve opening and injection is ended after the valve is opened). By setting the first fuel injection timing F1 until the first half of the intake stroke within the valve opening period of the intake port 17, the vaporization rate of the injected fuel is greatly improved due to the negative pressure generated by the rotary valve 50. .

  FIG. 11 is a graph showing the relationship between the intake air temperature and the evaporation rate.

  Referring to the figure, the vaporization rate at which about 1 atm (100 KPa) fuel is vaporized is 100% or more at 20 ° C., but decreases to about 70% when the intake air temperature falls to 0 ° C. . On the other hand, the vaporization rate of gasoline whose pressure has decreased to 67 KPa is maintained at 98% or more even when the intake air temperature is decreased from 20 ° C. to 0 ° C. Therefore, in order to maintain a high vaporization rate in a cold state where the vaporization rate is particularly problematic, it is advantageous to use a pressure drop even if there is a slight temperature change.

  Further, by setting the second fuel injection timing F2 in the vicinity of the opening of the rotary valve 50, it is possible to push the fuel injected at the impulse flow rate generated by the rotary valve 50 into the cylinder. Thus, in addition to the improvement of vaporization and atomization, the fuel mixing property by the impulse is improved.

  By adopting the fuel injection characteristics as shown in FIG. 10, the retard limit of the ignition timing IG of the spark plug 16 is also greatly increased. For example, after about 20 ° has elapsed at the crank angle CA from the top dead center of the compression stroke. It becomes possible to delay the ignition timing. In the illustrated embodiment, the rotary valve 50 is advanced as the detected temperature Wt increases with respect to the in-cylinder temperature until the detected temperature Wt reaches a predetermined temperature Wt1 (that is, when the temperature is cold). In addition to optimizing the balance between fuel consumption and exhaust performance, the ignition timing IG is advanced with the advance of the rotary valve 50 so that the air-fuel mixture is ignited within the range of the retard limit. . By retarding the ignition timing IG in this way, the engine 10 can be warmed up, and the ignition timing IG is retarded with the advance of the rotary valve 50. It becomes possible to achieve both improved fuel efficiency.

  FIG. 12 is a diagram showing the valve opening characteristics of the rotary valve from the catalyst activity promotion operation to the warm operation.

  Referring to FIG. 12A, during the catalyst activity promotion operation, it is preferable to operate with the rotary valve 50 fixed at the most retarded angle in order to set the retard limit as large as possible. However, when it is expected that the period of the catalyst activation promotion operation is shortened depending on the operation state, or when the detected temperature is relatively close to the predetermined temperature Wt1, as shown in FIG. As the temperature rises, the rotary valve 50 may be operated while being advanced.

  By the way, when the rotary valve 50 is operated, in the first half of the intake stroke, while the rotary valve 50 is closed, the temperature in the cylinders 12A to 12D expands, and thus the temperature decreases. For this reason, as a result of the air in the cylinder in the intake stroke absorbing ambient heat, the temperature in the cylinder becomes very high during the compression stroke. Therefore, in the present embodiment, the following measures are taken.

  FIG. 13 is a graph showing the characteristics of the rotary valve 50 and the engine speed N. In FIG.

Referring to FIG. 13, first, the engine crank angle degree sensor 66 and operating condition detecting means of the engine, based on the detection value, as the engine speed N becomes faster, the rotary valve 50 so as to advance ing. This makes it possible to obtain impulse generation characteristics suitable for the engine speed.

  Next, the knock sensor 28 is made to function as an octane number discriminating means for discriminating the octane number of the fuel, and when the determined octane number is low, the valve opening characteristic of the rotary valve 50 is shifted to the advance side than when it is high. . For this reason, in this embodiment, when the valve opening timing of the rotary valve 50 is advanced according to the engine speed N, an appropriate valve opening timing can be set for the rotary valve 50 according to the octane number of the fuel. Knocking can be avoided.

  Specifically, in the case of a high octane number, the phase at the most retarded angle is set to −115 ° with respect to the opening angle of the intake valve 19, and the most advanced angle is set at a predetermined rotational speed N1. ing. Further, in the case of a low octane number, the phase at the most retarded angle is slightly advanced from −115 °, and the engine rotational speed N is set to be advanced at a rotational speed N2 smaller than the predetermined rotational speed N1. Has been.

  Next, an operation flow according to the embodiment in which the settings of FIGS. 7 to 13 are made will be described with reference to the flowcharts of FIG. 14 to 16 are flowcharts based on the settings of FIGS. 7 to 13.

  Referring to FIG. 14, in the above configuration, first, after engine 10 starts to start (step S101), ECU 100 reads each detected value from an input element connected to the input unit (step S102). When the engine is started in step S101, the rotary valve 50 is in the most advanced angle (that is, OFF).

  Next, the ECU 100 determines the octane number of the fuel based on the detection value of the knock sensor 28 (knock strength in step S102) (step S103). If the fuel has a high octane number, the ECU 100 sets a target value of the rotary valve 50 with a high octane number characteristic from the control map based on FIG. 13 (step S104). On the other hand, if the fuel is not a high octane number, the ECU 100 sets a target value for the rotary valve 50 with a low octane number characteristic from the control map based on FIG. 13 (step S105). This makes it possible to obtain a pulse generation characteristic that is unlikely to cause knocking according to the octane number of the fuel.

  After the setting in step S104 or step S105 is completed, the ECU 100 determines whether or not the engine operating region is a low rotation / low load region (step S106).

  Referring to FIG. 15, in step S106, when the operating region of engine 10 is the low rotation / low load region, ECU 100 is not shown based on the detected value of engine water temperature sensor 67 as the catalyst activation state detecting means. The active state of the exhaust gas purification catalyst is determined (step S107). If it is determined that the active state is good, the ECU 100 determines whether or not the detected temperature Wt of the engine water temperature sensor 67 is less than the predetermined temperature Wt1, that is, whether or not the engine 10 is cold ( Step S108). If the engine 10 is cold, the ECU 100 changes the retardation correction region of the rotary valve 50 corresponding to the detected temperature Wt (step S109), and further, the ECU 100 changes the delay valve 50 corresponding to the detected temperature Wt. The set value is changed (step S110). These steps S109 and S110 are realized by storing data collected beforehand through experiments or the like in the ECU 100 as a control map and based on the control map.

  Further, the ECU 100 sets the fuel injection timing from the control map based on the graph shown in FIG. 9 (step S111). Since this flow is cold, the ECU 100 sets the cold fuel injection timing Tr1 based on FIG. 9A. Further, as shown in FIG. 10, the ignition timing IG is retarded corresponding to the settings in steps S109 and S110.

  Thereafter, the ECU 100 drives the rotary valve 50 based on the settings in steps S109 and S110 described above (step S112). Thereafter, fuel is injected based on the setting in step S111 (step S113). In this flow, since the fuel is injected at the cold fuel injection timing Tr1 shown in FIG. 9A in the cold state, the impulse generated by the rotary valve 50 at the cold time when the combustion stability is low, Fuel atomization is promoted. Thereby, combustion stability improves and exhaust performance also becomes high.

  Then, after the fuel is injected, spark mixture is ignited at a predetermined timing, whereby the air-fuel mixture whose mixing is promoted by the rotary valve 50 is burned, and torque is generated (step S114). During the cold time, the ignition timing IG is retarded by a predetermined amount, so that warm-up of the engine 10 is promoted.

  After the spark ignition is executed, the ECU 100 returns to step S102 until the engine 10 stops (step S115).

  Next, when it is determined in step S107 that the activation of the exhaust gas purification catalyst is insufficient, the ECU 100 sets the set value of the rotary valve 50 to the most retarded amount (step S116).

  Next, in order to improve the exhaust performance, the ECU 100 sets the air-fuel ratio to the stoichiometric air-fuel ratio (step S117). Thereafter, the ECU 100 sets the fuel injection mode to a split fuel injection mode that is divided into two based on the control map corresponding to FIG. 10 so as to create more exhaust energy (step S118). Thereafter, as shown in FIG. 10, the ignition timing IG is set to a value retarded by a predetermined amount (for example, 20 ° at the crank angle CA) from the compression top dead center (step S119), and thereafter, the process proceeds to step S112 and subsequent steps.

  As a result, when step S112 is executed, the rotary valve 50 opens in the state most delayed from the intake valve 19, so the cylinder 12A in the intake stroke until the rotary valve 50 is opened. A large negative pressure will be generated within ~ 12D.

  Further, when step S113 is executed based on step S118, the fuel set to the stoichiometric air-fuel ratio is injected by being divided into two in the intake stroke based on the control map corresponding to FIG.

  When step S114 is executed based on step S119, the spark plug 16 ignites the air-fuel mixture with the ignition timing IG retarded by a considerable amount. As a result, a relatively large amount of exhaust energy is generated, and the temperature of the exhaust gas purification catalyst quickly rises, so that the exhaust gas purification catalyst is activated.

  Next, in step S108, after the exhaust gas purification catalyst is activated, when the detected temperature Wt also reaches the warm region, the ECU 100 determines that the engine speed N is in the idling speed range (region below the idling speed). Is determined (step S120). If the engine speed N is in the idling speed range, the ECU 100 sets the operating condition of the rotary valve 50 to the set value at the time of warm in FIG. 7 and FIG. 8 (step S121). After completing this step S121, the ECU 100 proceeds to step S111.

  Since this flow is warm, the ECU 100 sets the injection timing to the warm fuel injection timing Tr2 in FIG. 9B. The ignition timing IG is advanced to the vicinity of the compression top dead center.

  Next, when the control proceeds to the subsequent step, the rotary valve 50 operates under warm operating conditions (step S112), and fuel is injected immediately after the opening timing of the rotary valve 50 (step S113), and a spark is generated. It is ignited (step S114). For this reason, fuel is injected immediately before the impulse is generated, and the fuel gets on the intake air and is pushed into the cylinders 12A to 12D. As a result, the fuel is also efficiently introduced into the cylinders 12A to 12D and mixed with the fresh air, so that mixing is promoted and the fresh air is cooled by the latent heat of vaporization of the fuel. Therefore, even when the air-fuel ratio is enriched in a high load state, it is possible to suppress the fuel from adhering to the passage wall surface and enhance the function of preventing knocking due to vaporization latent heat.

  On the other hand, when the engine speed N exceeds the idle speed range in step S120, the control shifts to step S123 of the flow described below.

  Referring to FIG. 16, in the determination of step S106 of FIG. 14, when the engine operating region is other than the low speed and low load region, ECU 100 determines whether or not the engine 10 operating region is a partial load region. (Step S122). If it is a partial load region, the ECU 100 refers to the flag F of the VIS valve 63 (step S123). If the value of the flag F is 0, the ECU 100 opens the VIS valve 63 (step S124). After updating the value to 1 (step S125), the process proceeds to step S111. If the value of the flag F is 1 in step S123, the process proceeds to the next step S111 as it is.

  On the other hand, when the engine operating state is the full load state in step S122, the ECU 100 refers to whether or not the value of the flag F is 1 (step S126), and when the value of the flag F is 1 The VIS valve 63 is closed (step S127), the value of the flag F is updated to 0 (step S128), and the process proceeds to step S111. If the value of the flag F is 0, the process proceeds to step S111 as it is.

  At the time of high load, as described above, the fuel set in step S111 is injected only immediately before the opening of the rotary valve 50 is started. As a result, due to the mixing effect of the rotary valve 50, the fuel can also cool the air in the cylinder.

  As described above, in the present embodiment, in generating an impulse by the rotary valve 50, in an operation region where it is determined that knocking is likely to occur (for example, a low-speed operation region or a low-medium-speed operation region with a low octane number) Since the opening timing of the rotary valve 50 is advanced by the ECU 100, the expansion of in-cylinder air at the closing timing of the rotary valve 50 is also alleviated. As a result, an excessive increase in the in-cylinder temperature during the compression stroke can be suppressed, and knocking can be avoided.

  Further, in the present embodiment, the opening timing of the rotary valve 50 is advanced as the detected engine speed N rises, and an operating state in which knocking is likely to occur (for example, in a low speed operation region or a low octane number). The low-medium speed operation region) shifts the valve opening characteristic of the rotary valve 50 to the advance side. For this reason, in this embodiment, it becomes possible to obtain a suitable impulse generation characteristic according to the operation region. In addition, when the opening timing of the rotary valve 50 is advanced according to the engine speed N, the operating state detected by the engine crank angle sensor 66 or the knock sensor 28, which is an example of the operating state detecting means, is easily knocked. As the rotary valve 50 is advanced, the appropriate valve opening timing can be set in the rotary valve 50 in accordance with the detected operating state, so that knocking can be avoided.

  Further, in this embodiment, when the determined octane number is low, the valve opening characteristic of the rotary valve 50 is shifted to the advance side as compared with the case where the determined octane number is high. For this reason, in the present embodiment, as shown in FIG. 13, when the valve opening timing of the rotary valve 50 is advanced according to the engine speed N, the valve opening characteristic is higher when the octane number is low than when it is high. Since the shift is made to the advance angle side, the rotary valve 50 advances in a lower rotation region in the case of the low octane number than in the case of the high octane number. Therefore, an appropriate valve opening timing can be set for the rotary valve 50 in accordance with the octane number of the fuel, so that knocking can be avoided.

  Further, in the present embodiment, as described with reference to FIG. 9B, in the high load operation region in which the rotary valve 50 is operating, the fuel by the fuel injection valve is just before the opening of the rotary valve 50. The injection is started. Therefore, in the present embodiment, the intake air speed can be increased by the impulse generated by the rotary valve 50. As a result, the fuel is pushed into the cylinder by the high-velocity intake air, so that the fuel can be vaporized and atomized and the mixing characteristics with the air can be promoted. Since the heat in the cylinder at the time of high load is absorbed, the temperature in the cylinder is lowered, contributing to suppression of knocking.

  Further, in the present embodiment, as shown in FIG. 10, the fuel is divided and controlled in the low load operation region. For this reason, in this embodiment, while preventing knocking in the high load operation region, in the low load operation region, promotion of vaporization using the negative pressure of the rotary valve 50 and a high flow rate of the intake air by the generated impulse are performed. It is possible to make use of the fuel mixing effect of the fuel.

  Further, in the present embodiment, when performing split injection control of fuel in the low load operation region, as shown in FIG. 10, the first half fuel is injected into the first half of the intake stroke before the rotary valve 50 is opened, and the rotary valve is The fuel in the latter half is injected immediately before 50 opens. For this reason, in this embodiment, even in a so-called direct injection engine in which fuel is directly injected into the combustion chamber of the engine, it is possible to reliably promote the vaporization and atomization of the fuel and improve the mixing performance.

  Thus, according to the present embodiment, there is a remarkable effect that knocking due to the generated negative pressure or the like can be prevented as much as possible while using the rotary valve 50 to the maximum.

  Each embodiment mentioned above is only a desirable example of the present invention, and the present invention is not limited to the embodiment mentioned above.

  For example, when the fuel injection is divided during the execution of the catalyst activation promotion operation, when this aspect is applied to a direct injection engine, the latter half of the fuel injection may be performed during the compression stroke. In addition, as a splitting mode in that case, three-split injection in the first half of the compression stroke may be employed after the opening of the intake valve is started, before the rotary valve is started, immediately after the rotary valve is opened.

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

1 is a right side view of a four-cycle spark ignition multi-cylinder engine according to an embodiment of the present invention. It is AA cross-section schematic of FIG. It is a perspective view which simplifies and shows the principal part of this embodiment. It is sectional drawing to which the principal part of FIG. 2 was expanded. It is the elements on larger scale which expand and show the principal part of FIG. It is a block diagram concerning this embodiment. It is a graph which shows the relationship between the torque which concerns on this embodiment, and an engine speed. It is a graph which shows the relationship between a rotary valve and a VIS valve, and a torque in an engine low speed operation area. It is a graph which shows the relationship between a cylinder pressure and a crank angle, (A) is at the time of cold, (B) is at the time of warm. 4 is a timing chart showing a valve opening angle, fuel injection timing, and ignition timing in a so-called fast idle state after engine startup. It is a graph showing the relationship between intake temperature and a vaporization rate. It is a figure which shows the valve opening characteristic of the rotary valve from the time of catalyst activity promotion operation to the time of warm operation. It is a figure which shows the characteristic of a rotary valve and an engine speed. It is a flowchart based on the setting of FIGS. It is a flowchart based on the setting of FIGS. It is a flowchart based on the setting of FIGS.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 12A-12D Cylinder 14 Cylinder 17 Intake port 18 Exhaust port 19 Intake valve 20 Exhaust valve 21 Fuel injection valve 22 Camshaft 28 Knock sensor (an example of an octane number detection means)
35 Exhaust passage 40 Intake device 41 Intake manifold 42 Surge tank 42 Surge tanks 43A to 43D Branch intake pipe 44 Throttle body 50 Rotary valve 56 Rotary valve advance mechanism 57 OCV system 58 Angle sensor 60 VIS (an example of variable passage length system)
61 Volumetric tube 63 Valve 64 Drive shaft 65 Valve actuator 66 Engine crank angle sensor 67 Engine water temperature sensor (an example of temperature detection means)
68 Accelerator opening sensor (an example of engine load detection means)
69 O ₂ sensor

Claims (5)

An intake pipe for supplying air to each intake port of a plurality of cylinders;
In a control apparatus for a multi-cylinder engine that includes a pulse generator that generates a pressure wave in a cylinder by opening the valve in the middle of the intake stroke during the valve opening period of the intake port corresponding to the intake stroke of each cylinder.
A variable valve timing mechanism capable of changing the valve opening timing of the pulse generator; and
Driving state detecting means for detecting the driving state of the engine;
And a control means for driving and controlling the pulse generator and the variable valve timing mechanism based on the detection of the operating state detecting means, and the control means is an operation in which the in-cylinder temperature becomes high during the compression stroke and knocking easily occurs. When in a state , the valve opening timing is advanced so as to suppress expansion of in-cylinder air at the valve opening timing of the pulse generator and to suppress an increase in the in-cylinder temperature during the compression stroke. A control device for a multi-cylinder engine. The control apparatus for a multi-cylinder engine according to claim 1,
An engine speed detecting means for detecting the engine speed is provided;
The control means advances the valve opening timing of the pulse generator as the detected engine speed increases, and shifts the valve opening characteristic of the pulse generator toward the advance side in an operation state in which knocking is likely to occur. A control device for a multi-cylinder engine, characterized in that: The control apparatus for a multi-cylinder engine according to claim 2,
An octane number discriminating means for discriminating the octane number of the fuel is provided, and the control means shifts the valve opening characteristic of the pulse generator toward the advance side when the discriminated octane number is low than when it is high. A control device for a multi-cylinder engine. The multi-cylinder engine control device according to any one of claims 1 to 3 ,
A control device for a multi-cylinder engine, wherein the control means performs split injection control of fuel in a low load operation region . The control device for a multi-cylinder engine according to claim 4 ,
The control means injects fuel in the first half before opening the pulse generator within the valve opening period of the intake port, and injects fuel in the second half near the time when the pulse generator opens. Multi-cylinder engine control device.

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