JP2005098170A - Controller of spark ignition engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smoothly switch a combustion state according to the operating conditions of an engine to improve fuel economy and emission. <P>SOLUTION: This controller of a spark ignition engine formed so that cylinders perform, at a specified phase difference, a cycle comprising an intake stroke, compression stroke, an expansion stroke, and an exhaust stroke comprises an engine control means which, in an operating area A as an operating area where the operating state of the engine is low load and low rotational speed, burns a preceding cylinder in a lean state and burns a subsequent cylinder by using a gas exhausted from the preceding cylinder and, in an operating area B other than the operating area A, switches so as to burn at a stoichiometric air-fuel ratio in the independent state of the cylinders. The engine control means is formed to perform the switching after temporarily stopping the burning of the preceding cylinder to burn only the subsequent cylinder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a spark ignition engine control device, and more particularly to a device for controlling the combustion state of each cylinder in a multi-cylinder engine to improve fuel consumption and emissions.

  Conventionally, in a spark ignition engine, in order to control the combustion state of each cylinder in order to improve fuel efficiency and emissions, the air-fuel ratio of the air-fuel mixture in each cylinder is set to a lean air-fuel ratio that is larger than the stoichiometric air-fuel ratio. A technique for improving fuel consumption by performing combustion in a state is known. For example, as shown in Patent Document 1, a fuel injection valve that directly injects fuel into a combustion chamber is provided, and in a low-rotation low-load region or the like It is known that stratified combustion is performed by injecting fuel in a compression stroke from the fuel injection valve, thereby realizing super lean combustion.

In such an engine, an ordinary three-way catalyst (a catalyst having a high purification performance in the vicinity of the theoretical air-fuel ratio with respect to HC, CO, and NOx) alone as an exhaust gas purification catalyst is sufficient for NOx during lean operation. Since the purification performance cannot be obtained, a lean NOx catalyst that adsorbs NOx in an oxygen-excess atmosphere and removes and reduces NOx in an oxygen-concentrated atmosphere is provided, as shown in the above publication. When such a lean NOx catalyst is used, if the NOx adsorption amount of the lean NOx catalyst increases during the lean operation, for example, as shown in the above publication, additional fuel is injected during the expansion stroke in addition to the main combustion. As a result, the air-fuel ratio of the exhaust gas is enriched and CO is generated, thereby promoting NOx separation and reduction.
Japanese Patent Laid-Open No. 10-275085

  The engine that performs the conventional lean operation as described above requires the lean NOx catalyst in order to ensure the NOx purification performance during the lean operation. A three-way catalyst is also required for exhaust purification in a region operated at a stoichiometric air-fuel ratio such as a high load region, and the lean NOx catalyst is provided in addition to the three-way catalyst, and the lean A NOx catalyst requires a relatively large capacity in order to secure a certain amount of NOx adsorption, and is expensive compared to a three-way catalyst, which is disadvantageous in terms of cost.

  In addition, in order to maintain the purification performance of the lean NOx catalyst, the NOx is removed temporarily, temporarily supplied by supplying additional fuel for reduction, etc. at predetermined intervals such that the NOx adsorption amount increases as described above. It is necessary to enrich the air-fuel ratio, which reduces the fuel efficiency improvement effect due to lean combustion.

  Therefore, in view of such a problem, the applicant of the present application, in a multi-cylinder engine that performs a cycle including intake, compression, expansion, and exhaust strokes, between a pair of cylinders in which an exhaust stroke and an intake stroke overlap in a low load low rotation range. In this case, the burned gas discharged from the preceding cylinder, which is the cylinder on the exhaust stroke side, is directly introduced into the subsequent cylinder, which is the cylinder on the intake stroke side, and the gas discharged from the subsequent cylinder is introduced into the exhaust passage provided with the three-way catalyst. In addition, when the two cylinders are connected, combustion is performed in a state where the preceding cylinder has a lean air-fuel ratio larger than the stoichiometric air-fuel ratio by a predetermined amount, and in the succeeding cylinder, the lean introduced from the preceding cylinder is performed. While controlling the combustion state etc. so that combustion is performed in a state where the stoichiometric air-fuel ratio is supplied by supplying fuel to the burned gas of the air-fuel ratio (referred to as a special operation mode), in the high load high rotation range Usual, I thought to control the combustion conditions or the like so as to perform the combusting respective cylinders at the stoichiometric air-fuel ratio (referred to the normal operation mode) (Japanese Patent Application No. 2002-024548).

  According to this, by setting the special operation mode in the low-load and low-rotation region, the preceding cylinder is burned at a lean air-fuel ratio, and the thermal efficiency is increased and the pumping loss is reduced, thereby significantly improving the fuel efficiency. In the succeeding cylinder, the fuel is supplied to the burned gas having a lean air-fuel ratio introduced from the preceding cylinder so as to achieve the stoichiometric air-fuel ratio, and the fuel efficiency is improved by reducing the pumping loss. can get. In addition, since only the combustion gas burned at the stoichiometric air-fuel ratio discharged from the subsequent cylinder is guided to the exhaust passage provided with the three-way catalyst, the exhaust gas purification performance is sufficiently ensured only by the three-way catalyst, and the lean NOx catalyst is also used. It becomes unnecessary.

  However, during the transition period of mode switching, the timing of switching between valve operation and stoppage may shift, and even in such a case, combustion of supplied fuel and discharge of burned gas are performed well. It is required to be

  The present invention has been made in consideration of the above-described conventional problems, and spark ignition capable of smoothly switching the operation mode even when the operation mode is switched for improving fuel efficiency and emission. An engine control device is provided.

  The invention according to claim 1 is a control device for a multi-cylinder spark ignition engine configured such that each cylinder performs a cycle including intake, compression, expansion, and exhaust strokes with a predetermined phase difference. Between a pair of cylinders in which the exhaust stroke and the intake stroke overlap, the preceding cylinder, which is the cylinder on the exhaust stroke side, burns at an air-fuel ratio larger than the stoichiometric air-fuel ratio, and the burned gas discharged from this preceding cylinder is the cylinder on the intake stroke side Each cylinder is independent of the special operation mode in which the burned gas and newly introduced fuel are combusted and introduced into the succeeding cylinder via the inter-cylinder gas passage, and the combustion gas is discharged into the exhaust passage. Engine control means for switching between the normal operation mode in which intake is performed from the intake passage and combustion is performed by exhausting from the exhaust passage, and the engine control means includes the normal operation mode and the special operation mode. When switching between modes, but to switch after the switching operation mode to burn only the following cylinders.

  According to a second aspect of the present invention, in the control device for the spark ignition type engine according to the first aspect, when performing the switching operation mode, the supply of fuel to the preceding cylinder is stopped and fuel is injected only to the subsequent cylinder. Is.

  According to a third aspect of the present invention, in the control device for the spark ignition type engine according to the first or second aspect, a preceding cylinder side exhaust passage communicating with the preceding cylinder and a subsequent cylinder side exhaust passage communicating with the subsequent cylinder are provided in the exhaust passage. And a three-way catalyst is separately arranged in the preceding cylinder side exhaust passage and the subsequent cylinder side exhaust passage.

  According to a fourth aspect of the present invention, in the spark ignition engine control apparatus according to any one of the first to third aspects, the first switching means for switching stop and execution of the introduction of fresh air to the subsequent cylinder, A second switching means for switching between execution and stop of the flow of the inter-cylinder gas passage and switching between stop and execution of exhaust from the preceding cylinder to the preceding cylinder side exhaust passage.

  According to a fifth aspect of the present invention, in the spark ignition engine control device according to the fourth aspect, when the engine control means switches from the special operation mode to the normal operation mode, the switching of the first switching means is performed in the The intake passage provided in the succeeding cylinder before the supply of burned gas from the preceding cylinder to the succeeding cylinder by the inter-cylinder gas passage is stopped by operating faster than the switching of the second switching means. From the above, fresh air is supplied to the succeeding cylinder.

  According to a sixth aspect of the present invention, in the control device for the spark ignition engine according to the fourth or fifth aspect, the second switching means stops and operates the exhaust valve provided in the exhaust port of the preceding cylinder. The gas lead-out valve provided at the preceding cylinder side end of the inter-cylinder gas passage and the gas introduction valve provided at the end of the succeeding cylinder are switched between the operating state and the stopped state. Switching is performed by a common control member.

The invention according to claim 7 is the control device for the spark ignition engine according to claims 1 to 6,
The switching operation mode is executed when switching from the special motion mode to the normal operation mode.

  If the configuration of the invention according to claim 1 is adopted, when switching between the normal operation mode and the special operation mode, the switching is performed after performing the switching operation mode in which only the subsequent cylinder is combusted. The succeeding cylinder exhausts from the exhaust passage in any of the normal operation mode and the special operation mode. Therefore, in the transition period of the mode switching, the valve operation / stop switching timing Even when there is a deviation, it is possible to discharge the burned gas satisfactorily, and it is possible to ensure a stable combustion state even in the transition period.

  Therefore, when switching from the special operation mode to the normal operation mode, the operation mode can be smoothly switched.

  If the configuration of the invention according to claim 2 is adopted, when the switching operation mode is performed, the supply of fuel to the preceding cylinder is stopped, and fuel is injected only to the succeeding cylinder, whereby the subsequent operation is performed in the switching operation mode. Only the cylinder can be burned easily and reliably.

  When switching between the special operation mode and the normal combustion mode, since the preceding cylinder does not perform combustion, fresh air is discharged as it is from the exhaust passage disposed in the preceding cylinder.

  Therefore, if the configuration of the invention according to claim 3 is adopted, since the three-way catalyst is separately arranged in the preceding cylinder side exhaust passage and the subsequent cylinder side exhaust passage, the place where the three way catalyst is arranged is provided. The fresh air exhausted from the preceding cylinder and the exhaust gas exhausted from the succeeding cylinder enter and mix, that is, the exhaust gas that has become lean does not enter the location where the three-way catalyst is disposed. The exhaust gas can be reliably purified.

  If the structure of the invention of Claim 4 is taken, while switching the execution and stop of the distribution | circulation of the said inter-cylinder gas passage, the 1st switching means which switches stop and execution of the introduction of fresh air to the said succeeding cylinder, And a second switching means for switching between stop and execution of exhaust from the preceding cylinder to the preceding cylinder side exhaust passage, so that the normal operation mode is changed from the special operation mode to the normal operation mode. By switching the first switching means earlier than the second switching means, the fresh air is supplied to the succeeding cylinder before the gas supply from the preceding cylinder to the succeeding cylinder is stopped. I can do it.

  Therefore, the supply of air to the succeeding cylinder can be more reliably prevented from being stopped, so that the succeeding cylinder can be more reliably combusted in the switching operation mode.

  If the structure of the invention of Claim 6 is taken, the exhaust valve provided in the exhaust port of the preceding cylinder, the gas outlet valve provided at the preceding cylinder side end of the inter-cylinder gas passage, and the following cylinder side end Since the gas introduction valve provided in can be controlled by a common control member, the entire control device can be made compact. In addition, the number of control members can be reduced, and the manufacturing cost can be reduced.

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

  FIG. 1 shows a schematic configuration of an engine according to an embodiment of the present invention, and FIG. 2 schematically shows a structure of one cylinder of an engine body 1 and intake / exhaust valves provided for the cylinder. In these drawings, the engine body 1 has a plurality of cylinders, and in the illustrated embodiment, has four cylinders 2A to 2D. A piston 3 is fitted into each of the cylinders 2 </ b> A to 2 </ b> D, and a combustion chamber 4 is formed above the piston 3.

  A spark plug 7 is provided at the top of the combustion chamber 4 of each cylinder 2 </ b> A to 2 </ b> D, and the tip of the plug faces the combustion chamber 4. An ignition circuit 8 capable of controlling the ignition timing by electronic control is connected to the spark plug 7. A fuel injection valve 9 that directly injects fuel into the combustion chamber 4 is provided at a side portion of the combustion chamber 4.

  Further, intake ports 11, 11a, 11b and exhaust ports 12, 12a, 12b are opened to the combustion chambers 4 of the respective cylinders 2A to 2D, and an intake passage 15 and an exhaust passage 20 are connected to these ports. Each port is opened and closed by intake valves 31, 31a, 31b and exhaust valves 32, 32a, 32b.

  Each cylinder performs a cycle consisting of intake, compression, expansion, and exhaust strokes with a predetermined phase difference. In the case of a four-cylinder engine, the cylinders 2A and 2 When the cylinder 2B, the third cylinder 2C, and the fourth cylinder 2D are called, as shown in FIG. 5, the cycle is 180 degrees in crank order in the order of the first cylinder 2A, the third cylinder 2C, the fourth cylinder 2D, and the second cylinder 2B. It is performed with a phase difference of °. In FIG. 5, EX is an exhaust stroke, IN is an intake stroke, F is fuel injection, S is forced ignition, and the star mark in the figure is compression ignition (forced ignition depending on conditions). Represents that.

  Between a pair of cylinders in which the exhaust stroke and the intake stroke overlap, a cylinder on the intake stroke side (referred to herein as a preceding cylinder) from the cylinder on the exhaust stroke side when the exhaust stroke and the intake stroke overlap (this specification) The inter-cylinder gas passage 22 is provided so that the burned gas can be directly introduced to the subsequent cylinder). In the four-cylinder engine of this embodiment, as shown in FIG. 5, the exhaust stroke (EX) of the first cylinder 2A and the intake stroke (IN) of the second cylinder 2B overlap, and the exhaust stroke (EX) of the fourth cylinder 2D. ) And the intake stroke (IN) of the third cylinder 2C overlap, the first cylinder 2A and the second cylinder 2B, and the fourth cylinder 2D and the third cylinder 2C form a pair, respectively, and the first cylinder 2A and the fourth cylinder 2C. The cylinder 2D is the preceding cylinder, and the second cylinder 2B and the third cylinder 2C are the subsequent cylinders.

  The intake / exhaust port of each cylinder and the intake passage, exhaust passage, and inter-cylinder gas passage connected to the cylinder are specifically configured as follows.

  The first cylinder 2A and the fourth cylinder 2D (hereinafter referred to as the preceding cylinders 2A and 2D), which are the preceding cylinders, respectively, have an intake port 11 for introducing fresh air, and burned gas. A first exhaust port 12a for sending (exhaust gas) to the exhaust passage and a second exhaust port 12b for leading the burned gas to the succeeding cylinder are provided. In addition, the second cylinder 2B and the third cylinder 2C (hereinafter, the subsequent cylinders are referred to as the subsequent cylinders 2B and 2C), which are the subsequent cylinders, are respectively provided with a first intake port 11a for introducing fresh air. A second intake port 11b for introducing burned gas from the preceding cylinder and an exhaust port 12 for sending burned gas to the exhaust passage are provided.

  In the example shown in FIG. 1, two intake ports 11 for the preceding cylinders 2A and 2D and two first intake ports 11a for the succeeding cylinders 2B and 2C are provided in parallel in the combustion chamber, while the preceding cylinder 2A. , 2D, the first exhaust port 12a and the second exhaust port 12b, and the second intake port 11b and the exhaust port 12 in the succeeding cylinders 2B and 2C are provided in parallel in the combustion chamber.

  The intake port 11 in the preceding cylinders 2A and 2D and the first intake port 11a in the succeeding cylinders 2B and 2C are connected to the downstream end of the branch intake passage 16 for each cylinder in the intake passage 15. In the vicinity of the downstream end of each branch intake passage 16, there is provided a throttle valve 17 that is linked to each other via a common shaft. This throttle valve 17 is driven by an actuator 18 in accordance with a control signal, and the amount of intake air is reduced. It comes to adjust. Note that an air flow sensor 19 that detects the intake air flow rate and an intake air temperature sensor 27 that measures the intake air temperature are provided in the common intake passage upstream of the gathering portion of the branch intake passage 16 in the intake passage 15. The throttle valve 17 is generally a multiple throttle valve.

  An upstream end of a branch exhaust passage 21 for each cylinder in the exhaust passage 20 is connected to the first exhaust port 12a in the preceding cylinders 2A and 2D and the exhaust port 12 in the subsequent cylinders 2B and 2C.

  The exhaust passage 20 includes a preceding cylinder side exhaust passage 20a and a subsequent cylinder side exhaust passage 20b. The preceding cylinder side exhaust passage 20a is connected to the branch exhaust passage 21 connected to the preceding cylinders 2A and 2D, and the subsequent cylinder side exhaust passage 20b is connected to the branch exhaust passage 21 connected to the subsequent cylinders 2B and 2C. Yes.

The preceding cylinder side exhaust passage 20a and the succeeding cylinder side exhaust passage 20b are each provided with an O ₂ sensor 23 that detects the air-fuel ratio by detecting the oxygen concentration in the exhaust gas. The O ₂ sensor 23 is a λO ₂ sensor whose output changes suddenly in the vicinity of the theoretical air-fuel ratio, and the fuel injection amount for each of the cylinders 2A to 2D is feedback-controlled based on the output of the O ₂ sensor 23.

Further, three-way catalysts 24a and 24b for purifying exhaust gas are provided in the preceding cylinder side exhaust passage 20a and the subsequent cylinder side exhaust passage 20b downstream of the O ₂ sensor 23, respectively. As is generally known, the three-way catalysts 24a and 24b are used for 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 is λ = 1). It is a catalyst that exhibits high purification performance.

  Further, an inter-cylinder gas passage 22 is provided between the first cylinder 2A and the second cylinder 2B and between the third cylinder 2C and the fourth cylinder 2D, and is provided in the second exhaust port 12b of the preceding cylinders 2A and 2D. The upstream end of the inter-cylinder gas passage 22 is connected, and the downstream end of the inter-cylinder gas passage 22 is connected to the second intake ports 11b of the succeeding cylinders 2B and 2C.

  The inter-cylinder gas passage 22 is a relatively short passage that connects adjacent cylinders, and is covered with a water jacket 26. The water jacket 26 includes a cooling water passage 52 (see FIG. 3) that surrounds the inter-cylinder gas passage 22 therein. When the burned gas discharged from the preceding cylinder passes through the inter-cylinder gas passage 22, the cooling water is stopped when the heat radiation is suppressed, and the cooling water is circulated when the heat radiation is promoted. The cooling water passage 52 is provided with a cooling pump 50 for circulating the cooling water and a cooling pump drive motor 51 for driving the cooling water, and a gas passage cooling water temperature sensor for measuring the temperature of the cooling water. 57 is provided (see FIG. 3).

Further, the inter-cylinder gas passage 22 is provided with a linear O ₂ sensor 25 whose output changes linearly according to the oxygen concentration, and the preceding cylinders 2A, 2D that have a predetermined lean air-fuel ratio according to the output. The fuel injection amount with respect to is feedback controlled.

  The intake / exhaust valves for opening and closing the intake / exhaust ports of each cylinder and the valve operating mechanism for these valves are as follows.

  The intake port 11, the first exhaust port 12a and the second exhaust port 12b in the preceding cylinders 2A and 2D are provided with an intake valve 31, a first exhaust valve 32a and a second exhaust valve 32b (gas outlet valve), respectively. The first intake port 11a, the second intake port 11b, and the exhaust port 12 in the succeeding cylinders 2B and 2C are provided with a first intake valve 31a, a second intake valve 31b (gas introduction valve), and an exhaust valve 32, respectively. These intake / exhaust valves are opened and closed at predetermined timings by the valve mechanisms comprising the camshafts 33, 34, etc. so that the intake stroke and exhaust stroke of each cylinder are performed with the predetermined phase difference as described above. To be driven.

  Further, among these intake / exhaust valves, the first exhaust valve 32a, the second exhaust valve 32b, the first intake valve 31a, and the second intake valve 31b are switched between an operating state and a stopped state. A valve stop mechanism 35 is provided. The valve stop mechanism 35 has been known in the art and will not be shown in detail. For example, hydraulic oil can be supplied to and discharged from a tappet interposed between the cams of the camshafts 33 and 34 and the valve shaft. When a hydraulic oil is supplied to the hydraulic chamber, the operation of the cam is transmitted to the valve and the valve is opened and closed. When the hydraulic oil is discharged from the hydraulic chamber, the cam operation is not performed. The valve is stopped by not being able to be transmitted to.

  A first control valve 37 is provided in the hydraulic oil supply / discharge passage 36 to the valve stop mechanism 35 of the first intake valve 31a, and a valve stop mechanism 35 of the first exhaust valve 32a and a valve stop mechanism of the second exhaust valve 32b. A second control valve 39 is provided in each of the hydraulic oil supply / discharge passages 38 with respect to 35 and the valve stop mechanism 35 of the second intake valve 31b (see FIG. 3).

FIG. 3 shows the configuration of the drive and control system. In this figure, signals from an air flow sensor 19, an O ₂ sensor 23, a linear O ₂ sensor 25, and an intake air temperature sensor 27 are sent to an engine control ECU (control unit) 40 (engine control means) composed of a microcomputer or the like. Signals are input from the rotational speed sensor 45 that detects the engine rotational speed to determine the driving state, the accelerator opening sensor 46 that detects the accelerator opening (accelerator pedal depression amount), the vehicle speed sensor 55, and the like. Further, signals from the engine cooling water temperature sensor 56 and the gas passage cooling water temperature sensor 57 are input to detect the temperature of each cooling water. Control signals are output from the ECU 40 to the fuel injection valves 9, the actuator 18 of the throttle valve 17, the first and second control valves 37 and 39, and the cooling pump drive motor 51. .

  The ECU 40 includes an operating state determination unit 41, a valve stop mechanism control unit 42, an intake air amount control unit 43, a combustion control unit 44, and a gas passage cooling control unit 47.

  The operating state discriminating means 41 examines the operating state of the engine (engine speed and engine load) based on signals from the rotational speed sensor 45, the accelerator opening sensor 46, etc., and the operating state is low and low as shown in FIG. It is discriminated whether the operation area A is on the rotation side or the operation area B on the high load side or high rotation side.

  When the engine is in a warm state (completely warmed up) and is not in a special state (for example, in-cylinder temperature rise in a subsequent cylinder described later), the operation region A is operated in the special operation mode. In the operation area B, the operation is performed in the normal operation mode. Details of the special operation mode and the normal operation mode will be described later.

  The valve stop mechanism control means 42 includes a first switching control means 42a and a second switching control means 42b.

  The first switching control means 42 a controls the valve stop mechanism 35 of the first intake valve 31 a by controlling the first control valve 37.

  The second switching control unit 42b controls the valve stop mechanism 35 disposed in the first exhaust valve 32a, the second exhaust valve 32b, and the second intake valve 31b by controlling the second control valve 39.

  That is, the first switching control means 42a, the first control valve 37, and the valve stop mechanism 35 controlled by them constitute a first switching means, and the second switching control means 42b, the second control valve 39, And the 2nd switching means is comprised by the valve stop mechanism 35 controlled by these.

  The first and second switching control means 42a and 42b control the control valves 37 and 39 in accordance with the special operation mode and the normal operation mode, so that each valve stop mechanism 35 is set as follows. Perform switching control.

Special operation mode: Stops the first exhaust valve 32a and the first intake valve 31a
Second exhaust valve 32b and second intake valve 31b are in operating state Normal operation mode: first exhaust valve 32a and first intake valve 31a are in operating state
The second exhaust valve 32b and the second intake valve 31b are in a stopped state. Note that the intake valve 31 and the exhaust valve 32 are always in operation regardless of the operation mode.

  The intake air amount control means 43 controls the opening degree of the throttle valve 17 (throttle opening degree) by controlling the actuator 18, and the target intake air amount (target intake air amount) from a map or the like according to the operating state. ) And the throttle opening is controlled according to the target intake air amount.

  In this case, in the special operation mode, as will be described later, in the succeeding cylinders 2B and 2C, excess air in the burned gas introduced from the preceding cylinder is newly supplied in a state where the intake air introduction from the branch intake passage 16 is blocked. Since the combustion is performed while the ratio of the fuel to the stoichiometric air-fuel ratio is the stoichiometric air-fuel ratio, the amount of fresh air necessary for the combustion of fuel corresponding to the required torque for the preceding and subsequent two cylinders (the amount of fuel for the two cylinders) The throttle opening is adjusted so that the theoretical air / fuel ratio is supplied to the preceding cylinders 2A and 2D.

  In the normal operation mode, each of the cylinders 2A to 2D performs combustion in a state in which it is richer than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio, so that an amount of fresh air corresponding to this combustion state is supplied. Thus, the throttle opening is adjusted. That is, the opening degree of the throttle valve 17 arranged in the preceding cylinders 2A and 2D is smaller than that in the special operation mode.

  The combustion control means 44 is composed of a fuel injection control means 44a and an ignition control means 44b. The fuel injection control means 44a allows the fuel injection amount and injection from the fuel injection valves 9 provided in the respective cylinders 2A to 2D. The timing is controlled in accordance with the operating state of the engine, and ignition control means 44b controls ignition timing and ignition stop according to the operating state. In particular, the combustion control (fuel injection control and ignition control) is changed depending on whether the operation state is the special operation mode or the normal operation mode.

  That is, in the special operation mode, for the preceding cylinders 2A and 2D, the fuel injection amount is set so that the air-fuel ratio is a lean air-fuel ratio larger than the stoichiometric air-fuel ratio, preferably approximately twice or more than the stoichiometric air-fuel ratio. In addition, the injection timing is set so that fuel is injected in the compression stroke and the mixture is stratified, and the ignition timing is set so that forced ignition is performed near the compression top dead center. On the other hand, for the succeeding cylinders 2B and 2C, fuel is supplied to the burned gas having a lean air-fuel ratio introduced from the preceding cylinder, the fuel injection amount is controlled so as to be the stoichiometric air-fuel ratio, and the intake stroke is performed. The injection timing is set so as to inject fuel. When the in-cylinder temperature of the succeeding cylinders 2B and 2C is a temperature suitable for compression ignition, forced ignition is stopped and combustion by compression ignition is performed.

  In the normal operation mode, the fuel injection amount is controlled so that the air-fuel ratio of each of the cylinders 2A to 2D is equal to or lower than the stoichiometric air-fuel ratio. The fuel ratio is made richer than the stoichiometric air-fuel ratio in the fully open load and the operation region in the vicinity thereof. In this case, the injection timing is set so that the air-fuel mixture is made uniform by injecting fuel to each of the cylinders 2A to 2D and the cylinders 2A to 2D are forcedly ignited. To.

  The gas passage cooling control means 47 controls the temperature of burned gas flowing in the inter-cylinder gas passage 22 during the special operation mode. Even in the special operation mode, the in-cylinder temperatures of the succeeding cylinders 2B and 2C are compressed and ignited when the operation state is a relatively high load and high rotation or immediately after the operation region B is shifted to the operation region A. The temperature may be higher than the temperature suitable for. Therefore, the gas passage cooling control means 47 operates the cooling pump drive motor 51 to cool the air-fuel mixture when the air-fuel mixture temperature in the subsequent cylinder is equal to or higher than a predetermined value. Cooling water is circulated in the cooling water passage 52 by the cooling pump 50 driven by the cooling pump drive motor 51, and the inter-cylinder gas passage 22 in the water jacket 26 is cooled. For this reason, the temperature of the burned gas guided from the preceding cylinders 2A and 2D to the succeeding cylinders 2B and 2C via the inter-cylinder gas passage 22 is lowered, so that the in-cylinder temperatures of the succeeding cylinders 2B and 2C are suitable for compression ignition. Temperature.

  The operation of the apparatus of the present embodiment as described above will be described with reference to FIGS.

  In the special operation mode, as described above, the first exhaust valve 32a and the first intake valve 31a are stopped, and the second exhaust valve 32b and the second intake valve 31b are activated. 6, the burned gas discharged from the preceding cylinders 2A, 2D is directly introduced into the succeeding cylinders 2B, 2C via the inter-cylinder gas passage 22, and the succeeding cylinders 2B, 2B, A two-cylinder connection state is established in which only the combustion gas discharged after being burned at 2C is guided to the exhaust passage 20.

In this state, fresh air is introduced into the preceding cylinders 2A and 2D from the intake passage 15 in the intake stroke (arrow a in FIG. 6), and the air-fuel ratio detected by the linear O ₂ sensor 25 is detected in the preceding cylinders 2A and 2D. Fuel is injected in the compression stroke while the fuel injection amount is feedback controlled so that the super lean air / fuel ratio is approximately twice or more than the theoretical air / fuel ratio, and ignition is performed at a predetermined ignition timing. Stratified combustion is performed at the fuel ratio.

  Thereafter, the burned gas discharged from the preceding cylinders 2A and 2D passes through the inter-cylinder gas passage 22 during the period in which the intake strokes of the preceding cylinders 2A and 2D overlap with the exhaust strokes of the succeeding cylinders 2B and 2C. (The white arrow in FIG. 5 and the arrow b in FIG. 6). In the succeeding cylinders 2B and 2C, fuel is supplied to the burned gas having a lean air-fuel ratio introduced from the preceding cylinders 2A and 2D, and the fuel injection amount is controlled so as to be substantially the stoichiometric air-fuel ratio. Fuel is injected during the intake stroke. At this time, in the succeeding cylinders 2B and 2C, forced ignition by the spark plug 7 is stopped, and compression ignition is performed near the top dead center of the compression stroke due to an increase in pressure and temperature in the combustion chamber.

  Thus, in the preceding cylinders 2A and 2D, the stratified combustion at the lean air-fuel ratio is performed, so that the thermal efficiency is increased and the pumping loss is reduced, and the fuel efficiency is greatly improved by the synergistic effect thereof. Further, in the succeeding cylinders 2B and 2C, fuel is supplied to the burned gas in an excess air state and combustion is performed while being controlled to the stoichiometric air-fuel ratio, so that stratified combustion is performed at a lean air-fuel ratio like the preceding cylinders 2A and 2D. Although the thermal efficiency is somewhat inferior to that in which the fuel consumption is performed, the fuel efficiency improvement effect by reducing the pumping loss can be sufficiently obtained.

  That is, in the preceding cylinders 2A and 2D, the thermal efficiency is increased and the pumping loss is reduced by the stratified combustion in the ultra-lean state, while in the succeeding cylinders 2B and 2C, the pumping loss reducing effect is obtained as in the preceding cylinders 2A and 2D. At the same time, when performing combustion by compression ignition, thermal efficiency is improved by performing compression ignition in a uniform mixture distribution state. Therefore, the fuel efficiency is greatly improved by these actions.

  Further, since the succeeding cylinder is switched from compression ignition to forced ignition as necessary, a special operation mode by forced ignition is possible even in an operation region unsuitable for compression ignition.

  Further, the amount of NOx generated in the preceding cylinders 2A and 2D is set to a lean air / fuel ratio that is approximately twice or more than the theoretical air / fuel ratio, so that the amount of NOx generated is relatively small. In the succeeding cylinders 2B and 2C, Since the burned gas is introduced, the state is equivalent to that in which a large amount of EGR is performed, so that the generation of NOx is sufficiently suppressed. This is also advantageous for improving emissions.

  On the other hand, in the normal operation mode, as described above, the first exhaust valve 32a and the first intake valve 31a are activated, and the second exhaust valve 32b and the second intake valve 31b are deactivated. 7 and the flow path of the gas is as shown in FIG. 7, and the intake ports 11 and 11a and the exhaust ports 12a and 12 of each cylinder 2A to 2D are substantially independent, and the intake ports of the cylinders 2A to 2D are separated from the intake passage 15. 11, 11a is introduced with fresh air, and burned gas is discharged into the exhaust passage 20 from the exhaust ports 12, 12a of the cylinders 2A to 2D. In this case, the output performance is ensured by controlling the intake air amount and the fuel injection amount so that the stoichiometric air-fuel ratio or richer (however, only in the fully open load region and the surrounding operation region). .

  FIG. 8 shows a flowchart of a part related to switching between the normal operation mode and the special operation mode in the control of the ECU 40.

  After the start of control, first, in step S11, the operation state determination means 41 determines whether the current engine operation state is a region located in the operation region A or a region located in the operation region B.

  In step S11, when the operation region is B, the process proceeds to step S21, and the operation state determination unit 41 determines whether or not the operation region is shifted from A to B.

  In the case of YES in step S21 (when it is determined that the operation region has been shifted from A to B), it is necessary to switch from the special operation mode to the normal operation mode. Intervene. Hereinafter, the control of the switching operation mode when switching from the special operation mode to the normal operation mode will be described in steps S22 to S27.

  First, in step S22, the fuel injection control means 44a is operated to stop the fuel injection to the preceding cylinders 2A and 2D, and the combustion of the preceding cylinders 2A and 2D is stopped. Accordingly, fresh air is introduced into the subsequent cylinders from the inter-cylinder gas passage 22. Next, in step S23, the throttle valve 17 is adjusted so that the opening amount is increased and the intake air amount is slightly increased. Further, in step S24, the fuel injection control means 44a changes the fuel injection amount to the succeeding cylinders 2B and 2C to an amount corresponding to the theoretical air-fuel ratio.

  Furthermore, in step S25, the opening degree of the throttle valve 17 is reduced, and in this state, the first switching control means 42a is operated to switch the first intake valve 31a from the stopped state to the operating state.

  Thereafter, in step S26, the opening degree of the throttle valve 17 is increased again, and in this state, the second switching control means 42b is operated to switch the second exhaust valve 32b and the second intake valve 31b from the operating state to the stopped state. At the same time, the first exhaust valve 32a is switched from the stopped state to the activated state.

  Finally, in order to shift from the switching operation mode to the normal operation mode, in step S27, the opening degree of the throttle valve 17 is reduced to a level corresponding to the required intake air amount in the normal operation mode, and the fuel corresponding to the stoichiometric air-fuel ratio. The fuel injection by the fuel injection control means 44a to the preceding cylinders 2A and 2D is resumed in the state where the injection amount is changed.

  If NO in step S21 (when it is determined that there is no switching of the operation region), the control in the normal operation mode is continued as it is without switching the operation mode (step S28).

  Next, a case where the operation region is A in step S11 will be described.

  In this case, the process proceeds to step S31, and the operation state determination unit 41 determines whether or not the operation region is shifted from B to A.

  In the case of YES in step S31 (when it is determined that the operation region has been shifted from B to A), it is necessary to switch from the normal operation mode to the special operation mode. Intervene. Hereinafter, the control of the switching operation mode when switching from the normal operation mode to the special operation mode will be described in steps S32 to S36.

  First, in step S32, the fuel injection control means 44a is operated to stop fuel injection to the preceding cylinders 2A and 2D. In step S33, the opening degree of the throttle valve 17 is adjusted to the opening degree of the throttle valve 17 corresponding to the target intake air amount of the preceding cylinders 2A and 2D by increasing the opening degree of the throttle valve 17.

  Next, in step S34, the opening degree of the throttle valve 17 is decreased, and in this state, the second switching control means 42b is operated to switch the second exhaust valve 32b and the second intake valve 31b from the stopped state to the operating state. Then, fresh air is introduced from the inter-cylinder gas passage 22 and the first exhaust valve 32a is switched from the operating state to the stopped state.

  Further, in step S35, the opening degree of the throttle valve 17 is increased, and in this state, the first switching control means 42a is operated to switch the first intake valve 31a from the operating state to the stopped state.

  Thereafter, in order to shift from the switching operation mode to the special operation mode, in step S36, the opening degree of the throttle valve 17 is reduced and the fuel injection amount corresponding to the lean air-fuel ratio is changed to the preceding cylinders 2A and 2D. In step S37, the fuel injection control unit 44a changes the fuel injection amount to the subsequent cylinders 2B and 2C to an amount corresponding to the stoichiometric air-fuel ratio.

  If NO in step S31 (when it is determined that there is no operation region switching), the operation mode is not switched and the special operation mode is continued as it is (step S38).

  With the above configuration, when switching between the normal operation mode and the special operation mode, the switching is performed after performing the switching operation mode in which only the subsequent cylinders 2B and 2C are burned. The succeeding cylinders 2B and 2C always maintain an operation state in which the gas burned in the cylinder is discharged from the exhaust port 12 to the succeeding cylinder side exhaust passage 20b regardless of the switching of the operation mode. It is possible to reliably burn the supplied fuel and discharge the burned gas even in the transition period of the operation mode. Therefore, in the transition period of the mode switching, it is possible to discharge the burned gas satisfactorily even when the valve operation and the stop switching timing are shifted. Therefore, it is possible to ensure a stable combustion state even in the transition period.

  Further, when the switching operation mode is performed, the supply of fuel to the preceding cylinders 2A and 2D is stopped and fuel is injected only into the succeeding cylinders 2B and 2C. Therefore, when the switching operation mode is executed, only the succeeding cylinders 2B and 2C are operated. It is possible to more reliably perform the combustion state.

  When switching to the switching operation, combustion is not performed in the preceding cylinders 2A and 2D, and therefore, fresh air is discharged as it is from the preceding cylinder side exhaust passage 20a disposed in the preceding cylinders 2A and 2D. Become. Further, in the succeeding cylinders 2B and 2C, the combustion gas burned at the stoichiometric air-fuel ratio is discharged from the succeeding cylinder side exhaust passage 20b and purified by the three-way catalyst 24b disposed in the succeeding cylinder side exhaust passage 20b. Become.

  That is, since fresh air discharged from the preceding cylinder side exhaust passage 20a is not mixed with the combustion gas discharged from the subsequent cylinder side exhaust passage 20b, the exhaust discharged from the subsequent cylinder side exhaust passage 20b becomes lean. Thus, the three-way catalyst 24b can be prevented from functioning and the exhaust gas can be purified with certainty.

  Further, when switching from the special operation mode to the normal operation mode, the gas from the preceding cylinders 2A, 2D to the succeeding cylinders 2B, 2C is activated by operating the first switching control means 42a earlier than the second switching control means 42b. It is possible to supply fresh air to the succeeding cylinders 2B and 2C before the supply of.

  Therefore, in the switching operation mode, it is possible to reliably prevent the supply of air to the subsequent cylinders 2B and 2C from being stopped, and to perform the combustion of the subsequent cylinders 2B and 2C more reliably.

  Further, a first exhaust valve 32a provided in the first exhaust port 12a of the preceding cylinders 2A, 2D, a second exhaust valve 32b provided at the preceding cylinder side end of the inter-cylinder gas passage 22, and a succeeding cylinder 2B, The second intake valve 31b provided at the side end of 2C is switched between the operating state and the stopped state by the second control valve 39. That is, since the control members for these valves are shared, the entire control device can be made compact. In addition, the number of control members can be reduced, and the manufacturing cost can be reduced.

  Further, since the combustion in the succeeding cylinders 2B and 2C is performed in step S24 with the opening of the throttle valve 17 increased in step S23, even if the thermal efficiency is reduced as compared with the special operation mode, This can be compensated by the increase in the intake air amount and the fuel injection amount, and the torque amount obtained from the entire engine does not rapidly decrease, and the occurrence of torque shock can be more effectively suppressed.

  Further, by reducing the opening of the throttle valve 17 in step S25, the intake amount of fresh air to the succeeding cylinders 2B and 2C is prevented from rapidly increasing as the first intake valve 31a is operated. And it can suppress that torque amount increases rapidly.

  In step S26, the operation of the second exhaust valve 32b and the second intake valve 31b is stopped by increasing the opening degree of the throttle valve 17 and increasing the intake amount from the first intake valve 31a. It is possible to suppress a sudden decrease in the amount of intake air sucked into the succeeding cylinders 2B and 2C, and it is possible to suppress a sudden decrease in the torque amount.

  Further, in step S34, by reducing the opening of the throttle valve 17 and limiting the intake air amount from the first intake valve 31a, the intake air amount introduced into the succeeding cylinders 2B and 2C increases rapidly. It is possible to prevent the torque amount from rapidly increasing.

  In step S35, the opening of the throttle valve 17 is increased, more fresh air is taken into the preceding cylinders 2A, 2D, and more intake air is introduced into the succeeding cylinders 2B, 2C through the inter-cylinder gas passage 22. As a result, by stopping the operation of the first intake valve 31a, it is possible to prevent the intake amount introduced into the succeeding cylinders 2B and 2C from rapidly decreasing and to suppress the torque amount from rapidly decreasing. it can.

  Further, since the opening degree of the throttle valve 17 is reduced in step S36, the amount of torque is obtained even when the lean air-fuel ratio combustion is performed in the preceding cylinders 2A and 2D to switch to the special operation mode with high thermal efficiency. It is possible to suppress an abrupt increase in.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, For example, the following forms are also possible.

  one. The fuel supply to the succeeding cylinders 2B and 2C in the special operation mode is not necessarily a direct injection type in which fuel is directly injected into the combustion chamber. For example, fuel injection valves are provided in the inter-cylinder gas passage 22 and the intake port 11a, and fuel is injected into the inter-cylinder gas passage 22 during the special operation mode, and fuel is injected into the intake port 11a during the normal operation mode. Alternatively, fuel may be supplied to each subsequent cylinder.

  two. The cooling means for the inter-cylinder gas passage 22 is not limited to the water cooling type as described above. For example, a so-called air-cooling type in which a large number of cooling fins are provided outside the inter-cylinder gas passage 22 and the traveling wind is introduced into the fin portions may be employed. Further, it is not necessary to provide a cooling means.

  three. The present invention is also applicable to multi-cylinder engines other than four cylinders. For example, in the case of six cylinders, the exhaust stroke of one cylinder and the intake stroke of another cylinder do not completely overlap. In this case, the exhaust stroke of one cylinder precedes the intake stroke of the other cylinder. In addition, two cylinders in which both strokes partially overlap may be used as a pair of preceding and succeeding cylinders.

It is a schematic plan view of the whole engine provided with the apparatus by one Embodiment of this invention. It is a schematic sectional drawing, such as an engine main body. It is a block diagram of a control system. It is explanatory drawing which shows an operation area | region. It is a figure which shows the exhaust stroke of each cylinder, an intake stroke, fuel injection timing, ignition timing, etc. FIG. It is explanatory drawing which shows the distribution path | route of substantial fresh air and gas at the time of low load low rotation. It is explanatory drawing which shows the distribution path | route of a substantially new air and gas when it exists in the operation area | region of a high load and high and low rotation side. 4 is a flowchart of control related to switching between a normal operation mode and a special operation mode.

Explanation of symbols

1 Engine body 2A First cylinder (preceding cylinder)
2B 2nd cylinder (following cylinder)
2C No. 3 cylinder (following cylinder)
2D 4th cylinder (preceding cylinder)
11 intake port 12 exhaust port 15 intake passage 20a preceding cylinder side exhaust passage 20b succeeding cylinder side exhaust passage 20 exhaust passage 22 inter-cylinder gas passages 24a, 24b three-way catalyst 31 intake valve 31b second intake valve (gas introduction valve)
32 Exhaust valve 32b Second exhaust valve (gas outlet valve)
35 Valve stop mechanism (first switching means, second switching means)
37 First control valve (first switching means)
39 Second control valve (second switching means)
40 ECU (engine control means)
41 driving state determination means 42a first switching control means (first switching means)
42b Second switching control means (second switching means)

Claims (7)

A control device for a multi-cylinder spark ignition engine configured such that each cylinder performs a cycle including intake, compression, expansion, and exhaust strokes with a predetermined phase difference,
Between a pair of cylinders where the exhaust stroke and the intake stroke overlap, the preceding cylinder which is the cylinder on the exhaust stroke side burns at an air / fuel ratio larger than the theoretical air / fuel ratio, and the burned gas discharged from this preceding cylinder is the cylinder on the intake stroke side A special operation mode for introducing the burned gas and the newly introduced fuel into the succeeding cylinder via the inter-cylinder gas passage, and discharging the combustion gas to the exhaust passage;
A normal operation mode in which each cylinder independently intakes air from the intake passage and exhausts from the exhaust passage for combustion;
Engine control means for switching between,
The engine control means switches after performing a switching operation mode in which only the subsequent cylinder is burned when switching between the normal operation mode and the special operation mode. The control device for the spark ignition engine according to claim 1,
A control device for a spark ignition engine, wherein when performing the switching operation mode, supply of fuel to the preceding cylinder is stopped and fuel is injected only to the succeeding cylinder. The control device for the spark ignition engine according to claim 1 or 2,
Formed in the exhaust passage is a preceding cylinder side exhaust passage that communicates with the preceding cylinder and a subsequent cylinder side exhaust passage that communicates with the subsequent cylinder. A control device for a spark ignition engine characterized by arranging a catalyst. The control device for the spark ignition engine according to any one of claims 1 to 3,
A first switching means for switching between stopping and executing the introduction of fresh air to the subsequent cylinder;
Second switching means for switching between execution and stop of circulation of the inter-cylinder gas passage, and for switching between stop and execution of exhaust from the preceding cylinder to the preceding cylinder side exhaust passage;
A spark ignition type engine control device. The control device for the spark ignition engine according to claim 4,
When the engine control means switches from the special operation mode to the normal operation mode, the first switching means is operated earlier than the switching of the second switching means, so that the preceding gas passage by the inter-cylinder gas passage is performed. Spark ignition is characterized in that fresh air is supplied to the succeeding cylinder from the intake passage provided in the succeeding cylinder before the supply of burned gas from the cylinder to the succeeding cylinder is stopped. Type engine control device. The control device for a spark ignition engine according to claim 4 or 5,
The second switching means switches an exhaust valve provided at an exhaust port of the preceding cylinder between a stopped state and an operating state, and a gas outlet valve provided at an end of the preceding cylinder side of the inter-cylinder gas passage; A control device for a spark ignition engine, wherein a gas introduction valve provided at an end portion of a succeeding cylinder is switched between an operating state and a stopped state, and these valves are switched by a common control member. In the control device for the spark ignition type engine according to claim 1,
A control device for a spark ignition engine, wherein the switching operation mode is executed when the special motion mode is switched to the normal operation mode.

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