JP5920237B2 - Control device for spark ignition engine - Google Patents

Description

  The present invention relates to a spark ignition engine, and more particularly, to a spark ignition engine control device that retards ignition timing in order to suppress knocking in a high load region where the temperature rise of a cylinder is significant.

  In general, in a spark ignition type engine, knocking (not occurring during the propagation of flame) occurs in a high load range including the throttle full open range used for acceleration or climbing, because the temperature rise of the cylinder is remarkable due to the increase in fuel injection amount. Abnormal combustion in which the end gas of combustion self-ignites) is likely to occur. Therefore, in the operation region, the ignition timing (ignition timing) is retarded by a predetermined amount from the MBT (Minimum Advance for Best Torque), which is the timing at which the most torque is generated (usually near the compression top dead center), and knocking is performed. Is suppressed (see Patent Document 1).

  In addition, the scavenging efficiency of the exhaust gas is reduced by the exhaust pressure by adjusting the amount of refrigerant flowing through the water-cooled exhaust manifold so that the positive pressure wave peak formed by the exhaust in the water-cooled exhaust manifold is not included in the overlap period of the intake and exhaust valves. A technique for avoiding this is known (see Patent Document 2).

JP 2007-292050 A JP 2010-159678 A

  By the way, the negative pressure wave generated by the exhaust pulsation in the exhaust passage reaches the exhaust port during the overlap period of the intake and exhaust valves where both the intake valve and the exhaust valve are open, thereby scavenging the residual gas in the cylinder. As described above, a technique for configuring the exhaust passage is well known. According to this technique, the residual gas in the cylinder is reduced and the volumetric efficiency is increased, so that the torque in the high load region including the throttle full open region is improved.

  Here, since the distance between the cylinder and the portion of the exhaust passage where the pressure wave is reflected (for example, a collection portion of a plurality of exhaust pipes, etc.) is fixed, the exhaust valve is opened and the blowdown gas flows into the exhaust passage. Since the time required for the negative pressure wave generated by exhaust pulsation to reach the exhaust port is constant after it is ejected at a high speed, the engine speed varies depending on the operating conditions. As a result, the negative pressure wave may or may not reach the exhaust port during the overlap period of the intake and exhaust valves. Therefore, there are a speed range where the scavenging efficiency is high and a speed range where the scavenging efficiency is low. In the speed range where the scavenging efficiency is low, a drop in the high load range torque occurs compared to other speed ranges.

  The present invention has been made in view of the above circumstances, and is a spark ignition type engine capable of improving a drop in high load range torque in a speed range where scavenging efficiency due to a negative pressure wave caused by exhaust pulsation is relatively low. The purpose is to provide a control device.

In order to solve the above-mentioned problems, the present invention provides a spark ignition engine control device comprising a cooling mechanism for cooling the engine body and a control means for retarding the ignition timing at least in a high load region of the engine. there are, said to enhance the scavenging efficiency of the residual gas in the cylinder by causing reach the exhaust port negative pressure wave caused by exhaust pulsation in the exhaust passage at a predetermined engine speed range during the overlap period of the intake and exhaust valves exhaust passage is constituted, wherein, in the region of more than a predetermined load including a maximum load of the high load region, in the predetermined engine speed range other than the engine speed range, the predetermined engine speed range Compared to the above, the control device for the spark ignition engine is characterized in that the cooling capacity of the cooling mechanism is set high.

According to the present invention, in a spark ignition type engine in which at least the high load region of the engine is a retard region (referred to as an operation region of an engine that performs retarding of the ignition timing in order to suppress knocking; hereinafter the same), the high region that is the retard region. In the load range, in the speed range where the scavenging efficiency due to the negative pressure wave caused by exhaust pulsation is relatively low ( engine speed range other than the predetermined engine speed range, hereinafter referred to as “scavenging reduction speed range” as appropriate ), exhaust pulsation The cooling capacity of the cooling mechanism is set higher than the speed range in which the scavenging efficiency due to the negative pressure wave generated in the above is relatively high ( predetermined engine speed range, hereinafter referred to as “good scavenging speed range”). In the scavenging reduction speed region, the cooling of the engine body is enhanced and the temperature of the engine body is decreased compared to the scavenging good speed region. Therefore, knocking is suppressed in the scavenging reduction speed range, and the retard amount can be reduced (ignition timing advance (advance)), so that the torque drop in the scavenging reduction speed range is compensated. As a result, a flat and high torque curve can be obtained, and an engine that is easy to handle with high torque can be realized.

  As described above, according to the present invention, there is provided a control device for a spark ignition engine capable of improving the drop in the high load region torque in the scavenging reduction speed region.

  In the present invention, preferably, the engine is an in-vehicle engine mounted on a vehicle, and an output shaft of the engine body is connected to wheels via a transmission having a plurality of gear stages, and the control means The control for setting the cooling capacity of the cooling mechanism to be high is executed only when the gear stage of the transmission is equal to or higher than a predetermined level (Claim 2).

  According to this configuration, it is possible to increase the cooling capacity without waste under appropriate conditions in consideration of the delay time until the temperature of the engine body actually decreases. In other words, when the gear stage of the transmission is low, there is a possibility that the operating point of the engine moves sharply and shifts up immediately (the gear stage is changed to a higher gear stage). Therefore, even if the operating point moves to the scavenging reduction speed range, even if the cooling capacity is increased, if the gear stage is low, the operating point already has the cooling capacity when the temperature of each cylinder of the engine body actually decreases. There is a possibility that the vehicle has moved to an operation region that does not need to be increased (for example, a scavenging good speed region, a low-speed medium load region, a low-speed low-load region, etc.).

  Therefore, in this configuration, the control for increasing the cooling capacity is performed only when the gear stage of the transmission is high (that is, when the operation point moves slowly and is close to the cruise state). As a result, the above-mentioned problem that may occur when the cooling capacity is increased despite the low gear position is avoided. Also, when performing control to increase the cooling capacity in the scavenging reduction speed range, even if there is some delay time until the temperature of the engine body actually decreases, the operating point is in the operating area where it is not necessary to increase the cooling capacity. Since the temperature of the engine body can be sufficiently lowered in the scavenging reduction speed range before moving, control for increasing the cooling capacity is not wasted.

  In the present invention, it is preferable that the region where the cooling capacity of the cooling mechanism is set high because the scavenging efficiency is low is set to a speed region less than a predetermined reference speed (Claim 3).

  According to this configuration, control for increasing the cooling capacity is performed even if the scavenging reduction speed region is in the low speed region.

  In general, since the rotational speed is low in the low speed region, the fluidity of the air-fuel mixture in the cylinder tends to decrease, and unburned HC tends to be generated. However, the scavenging reduction speed range belongs to the high load range, the scavenging efficiency is low, and a considerable amount of residual gas remains in the cylinder, so the cylinder temperature is high and fuel atomization is promoted. The For this reason, even if the cooling of the engine body is enhanced in the scavenging reduction speed region, the vaporization and atomization of the fuel is not significantly inhibited. The effect of advancing the ignition timing (advancing) and increasing the high load region torque is greater than that.

  Therefore, in this configuration, the cooling capacity is increased even if the scavenging reduction speed region is in the low speed region. As a result, the drop in the high load region torque in the low speed region is compensated, and a flatter torque curve can be obtained.

  In the present invention, preferably, the control means retards the ignition timing in a medium load region in the high speed region of the engine, and the cooling means is higher in the high speed region in the medium load region than in the low speed region in the medium load region. The cooling capacity of the mechanism is set high (claim 4).

  According to this configuration, in a spark ignition engine in which the high-speed medium load region of the engine is the retard region in addition to the high load region of the engine, the high-speed medium load region that is the retard region is in the low-speed medium load region that is not the retard region. In comparison, since the cooling capacity of the cooling mechanism is set high, the problem of fuel consumption reduction that increases when the cooling capacity of the cooling mechanism is not set high is reduced.

  That is, since the high speed medium load region is on the high speed side compared to the low speed medium load region, the amount of heat generated per unit time is large. For this reason, the high-speed medium load region is set as a retard region in order to suppress knocking.

  By the way, if the ignition timing is retarded, the torque is reduced by that amount, so it is necessary to increase the fuel injection amount to compensate for the torque, and there is a problem that the fuel consumption decreases. In addition, if the ignition timing is retarded, the exhaust gas temperature increases due to post-combustion of the fuel or the expansion of the combustion gas, which increases the possibility of causing abnormal combustion (for example, knocking occurs due to an increase in the temperature of the exhaust valve). Since it easily occurs), the cylinder temperature is lowered by increasing the fuel injection amount and the remaining latent heat of vaporization of the fuel, and this also causes a problem that the fuel consumption is lowered.

  Therefore, in this configuration, the cooling capacity of the cooling mechanism is set higher in the high speed region, which is the retard region, in the same engine medium load region than in the low speed region that is not the retard region. Thereby, in the high-speed medium load region, the cooling of the engine body is strengthened, the temperature of the engine body is lowered, and knocking is suppressed. As a result, the retard amount can be reduced (ignition timing advance (advance)), so that the torque is increased and the fuel efficiency is improved. Further, since the exhaust gas temperature decreases due to the decrease in the retard amount, the fuel injection amount can be reduced, and the fuel efficiency is also improved in this respect.

On the other hand, in the low-speed medium load range where the exhaust temperature does not rise to the extent that reliability is reduced even when retarded, the cooling capacity of the cooling mechanism is set lower than in the high-speed medium load region, so the engine body is excessively There is no cooling. As described above, since the rotational speed is low in the low speed region, the fluidity of the air-fuel mixture in the cylinder is likely to be lowered, and unburned HC is likely to be generated. On the other hand, according to the present invention, the engine body is not excessively cooled in such a low-speed and middle-load region. An increase in the amount of generated fuel HC is prevented. Further, since the engine body is not excessively cooled, an increase in friction loss is also prevented. As a result, a reduction in fuel consumption is prevented even in a low-speed medium load region that is not the retard region.
The present invention also provides a spark ignition type engine control device comprising a cooling mechanism for cooling the engine body and a control means for retarding the ignition timing at least in a high load region of the engine, wherein the engine is installed in a vehicle. The engine mounted on the vehicle has an output shaft connected to wheels via a transmission having a plurality of gear stages, and a negative pressure wave generated by exhaust pulsation in the exhaust passage is generated by the intake and exhaust valves. The exhaust passage is configured so that the residual gas in the cylinder is scavenged by reaching the exhaust port during the overlap period, and the control means has a scavenging efficiency in another speed range in a high load range. In the lower speed range, the gear speed of the transmission is controlled so that the cooling capacity of the cooling mechanism is set higher than that in the other speed ranges and the cooling capacity of the cooling mechanism is set higher. To provide a control apparatus for a spark-ignited internal combustion engine and executes only when the above constant of grade (claim 5).
The present invention also relates to a spark ignition type engine control device comprising a cooling mechanism for cooling the engine body and a control means for retarding the ignition timing at least in a high load region of the engine. The exhaust passage is configured so that residual gas in the cylinder is scavenged by the negative pressure wave generated by pulsation reaching the exhaust port during the overlap period of the intake and exhaust valves, and the control means In the speed range where the scavenging efficiency is lower than the other speed ranges, the cooling capacity of the cooling mechanism is set higher than in the other speed ranges, and the ignition timing retard is set in the medium load range in the high speed range of the engine. In the high-speed region in the medium load region of the engine, the cooling capacity of the cooling mechanism is set higher than in the low-speed region in the medium load region. Providing an apparatus (claim 6).

  The present invention provides a control device for a spark ignition engine that can improve a drop in high load range torque in a speed range where scavenging efficiency is relatively low due to a negative pressure wave caused by exhaust pulsation, and can obtain a flat torque curve without a shock. Therefore, it contributes to the development and improvement of torque improvement technology for spark ignition engines.

1 is a plan view showing an overall configuration of a spark ignition engine according to an embodiment of the present invention. It is sectional drawing of the principal part of the said engine. It is a figure which shows the opening / closing timing and overlap period of the exhaust valve and intake valve of the engine. It is explanatory drawing of the definition of the opening / closing timing and valve opening period of the exhaust valve and intake valve of the engine. It is a figure which shows the state which a pressure wave reciprocates between the cylinder of the said engine, and the 2nd collection part of an exhaust passage. It is explanatory drawing of the pressure change which arises in the exhaust port of the said engine. It is a figure which shows the change of the volumetric efficiency with respect to the rotational speed of the said engine. It is a block diagram which shows the control system of the said engine. It is the map which divided the operation area | region of the said engine by the difference in control. It is a part of flowchart which shows the procedure of the control action performed during the driving | operation of the said engine. It is the remaining part of the flowchart. It is a graph for demonstrating the effect of the advance of the ignition timing of the engine.

(1) Overall Configuration of Engine FIGS. 1 and 2 are schematic plan views showing the overall configuration of a spark ignition engine according to an embodiment of the present invention. The engine shown in these drawings is a 4-cycle multi-cylinder gasoline engine mounted on a vehicle as a power source for traveling. Specifically, this engine is generated by an in-line four-cylinder engine main body 1 having four cylinders 2 arranged in a straight line, an intake passage 20 for introducing air into the engine main body 1, and the engine main body 1. An exhaust passage 25 for discharging exhaust gas and a cooling mechanism 30 for cooling the engine body 1 are provided.

  The engine body 1 includes a cylinder block 3 in which the four cylinders 2 are formed, a cylinder head 4 provided at the top of the cylinder block 3, and a piston 5 that is slidably inserted into each cylinder 2. have.

  A combustion chamber 10 is formed above the piston 5, and fuel mainly composed of gasoline is supplied to the combustion chamber 10 by injection from an injector 11 described later. The injected fuel burns in the combustion chamber 10, and the piston 5 pushed down by the expansion force due to the combustion reciprocates in the vertical direction.

  The piston 5 is connected to a crankshaft 15 that is an output shaft of the engine main body 1 via a connecting rod 16, and the crankshaft 15 rotates around the central axis in accordance with the reciprocating motion of the piston 5. Yes.

  The crankshaft 15 is connected to a wheel (not shown) via a transmission 40 (FIG. 8). The transmission 40 is a multi-stage transmission having a plurality of gear stages (for example, six forward stages and one reverse stage), and is linked to a shift lever operated by a driver.

  The cylinder block 3 is provided with an engine speed sensor SN1 that detects the rotational speed of the crankshaft 15 as the rotational speed of the engine.

  The cylinder head 4 includes an injector 11 that injects fuel (gasoline) toward the combustion chamber 10, and an ignition plug 12 that supplies ignition energy by spark discharge to the fuel / air mixture injected from the injector 11. However, one set is provided for each cylinder 2.

  In the four-cycle four-cylinder gasoline engine as in this embodiment, the piston 5 provided in each cylinder 2 moves up and down with a phase difference of 180 ° (180 ° CA) in crank angle. Correspondingly, the timing of ignition in each cylinder 2 is also set to a timing shifted in phase by 180 ° CA. Specifically, if the first, second, third, and fourth cylinders are sequentially arranged from the left cylinder 2 in FIG. 1, ignition is performed in the order of the first cylinder → the third cylinder → the fourth cylinder → the second cylinder. .

  The geometric compression ratio of each cylinder 2 or engine body 1, that is, the ratio of the volume of the combustion chamber 10 when the piston 5 is at bottom dead center and the volume of the combustion chamber 10 when the piston 5 is at top dead center Is set to 12 or higher, which is a high value for a gasoline engine.

  The cylinder head 4 includes an intake port 6 for introducing air supplied from the intake passage 20 into the combustion chamber 10 of each cylinder 2, and exhaust gas generated in the combustion chamber 10 of each cylinder 2 into the exhaust passage 25. An exhaust port 7 for leading out, an intake valve 8 for opening and closing the opening of the intake port 6 on the combustion chamber 10 side, and an exhaust valve 9 for opening and closing the opening of the exhaust port 7 on the combustion chamber 10 side are provided. In the present embodiment, two intake valves 8 and two exhaust valves 9 are provided for each cylinder 2.

  The intake valve 8 and the exhaust valve 9 are driven to open and close in conjunction with the rotation of the crankshaft 15 by an intake valve drive mechanism 18 and an exhaust valve drive mechanism 19 disposed in the cylinder head 4, respectively.

  The intake valve drive mechanism 18 includes an intake camshaft 18 a connected to the intake valve 8 and an intake VVT (Variable Valve Timing mechanism) 18 b. The exhaust valve drive mechanism 19 has an exhaust camshaft 19a connected to the exhaust valve 9 and an exhaust VVT 19b. The intake camshaft 18a and the exhaust camshaft 19a are connected to the crankshaft 15 via a power transmission mechanism such as a well-known chain and sprocket mechanism, and rotate with the rotation of the crankshaft 15, so that the intake valve 19 and the exhaust camshaft The valve 20 is driven to open and close.

  The intake VVT 18b and the exhaust VVT 19b are for changing the valve timing of the intake valve 8 and the exhaust valve 9. For example, the intake VVT 18b has a predetermined driven shaft that is arranged coaxially with the intake camshaft 18a and is directly driven by the crankshaft 15, and changes the phase difference between the driven shaft and the intake camshaft 18a. To do. As a result, the phase difference between the crankshaft 15 and the intake camshaft 18a is changed, and the valve timing of the intake valve 8 is changed. The same applies to the exhaust VVT 19b.

  As specific configurations of the intake VVT 18b and the exhaust VVT 19b, for example, there are a plurality of liquid chambers arranged in the circumferential direction between the driven shaft and the intake camshaft 18a or the exhaust camshaft 19a. By providing a hydraulic mechanism that changes the phase difference by providing a pressure difference, or by placing an electromagnet between the driven shaft and the intake camshaft 18a or the exhaust camshaft 19a, and applying electric power to the electromagnet. Examples include an electromagnetic mechanism that changes the phase difference.

  In this embodiment, by controlling the closing timing of the intake valve 8 by the intake VVT 18b, the effective compression ratio of each cylinder 2 or the engine body 1, that is, the volume of the combustion chamber 10 at the closing timing of the intake valve 8 is determined. The ratio with the volume of the combustion chamber 10 when the piston 5 is at the top dead center is higher for a gasoline engine in a high load region (third to fifth operation regions C1, C2, and D in the map of FIG. 9). The value is set to 10 or more.

  FIG. 3 shows opening / closing timings of the exhaust valve 9 and the intake valve 8. In this figure, EVO is the opening timing of the exhaust valve 9, EVC is the closing timing of the exhaust valve 9, IVO is the opening timing of the intake valve 8, and IVC is the closing timing of the intake valve 8. OL is an overlap period between the intake valve 8 and the exhaust valve 9 (overlap period of the intake and exhaust valves 8 and 9). As shown in this figure, the opening / closing timing of the exhaust valve 9 and the opening / closing timing of the intake valve 8 can be changed over the timing indicated by the solid line and the timing indicated by the broken line, respectively.

  In the present embodiment, the intake VVT 18b and the exhaust VVT 19b are configured such that the valve opening period and the lift amount of the intake valve 8 and the exhaust valve 9, that is, the valve profile is kept constant, while the valve opening timing IVO of the intake valve 8 and the exhaust valve 9 is maintained. , EVO and valve closing timings IVC and EVC are changed.

  In the present embodiment, as shown in FIG. 4, the valve opening period of the exhaust valve 9 and the intake valve 8 is a gentle valve lift gradient on the valve opening start side and valve closing completion side during the valve lift period. The valve opening timing EVO, IVO and the valve closing timing EVC, IVC of the exhaust valve 9 and the intake valve are the valve opening start timing and the valve closing completion timing of the valve opening period. Say. For example, when the height of the ramp portion is 0.3 mm, the timing when the valve lift amount increases or decreases to 0.3 mm is the valve opening timing and the valve closing timing, respectively.

  Returning to FIG. 1, the intake passage 20 includes four independent intake passages 21 communicating with the intake port 6 of each cylinder 2, and upstream end portions (upstream end portions in the intake air flow direction) of the individual intake passages 21. ) And a single intake pipe 23 extending upstream from the surge tank 22.

  An openable and closable throttle valve 24 for adjusting the flow rate of air sucked into the engine body 1 is provided in the middle of the intake pipe 23, and an air flow sensor for detecting the flow rate of the intake air is provided in the surge tank 22. SN2 is provided.

  The exhaust passage 25 includes four first exhaust portions 26a in which four independent exhaust passages 26 communicating with the exhaust ports 7 of the respective cylinders 2 and independent exhaust passages 26 of two cylinders 2 that are not adjacent to each other in the exhaust order are gathered. And two intermediate exhaust passages 27 connected downstream of each first collection portion 26a (downstream in the flow direction of the exhaust gas), and one second collection portion 27a in which the two intermediate exhaust passages 27 gather together. And one exhaust pipe 28 connected downstream of the second collecting portion 27a.

  Specifically, in the engine according to the present embodiment, the exhaust stroke is performed in the order of the first cylinder → the third cylinder → the fourth cylinder → the second cylinder, and therefore, the exhaust order is adjacent in the four independent exhaust passages 26. The independent exhaust passage 26 of the first cylinder and the independent exhaust passage 26 of the fourth cylinder that do not match together, and the independent exhaust passage 26 of the second cylinder and the independent exhaust passage 26 of the third cylinder gather together to form two One set portion 26a and one second set portion 27a downstream thereof are formed.

  Although not shown, the exhaust pipe 28 is provided with a three-way catalyst that provides the best exhaust purification capability when the air-fuel ratio is the stoichiometric air-fuel ratio (λ = 1).

  Here, the relationship among the passage sectional area S1 of one independent exhaust passage 26, the passage sectional area S2 of one intermediate exhaust passage 27, and the passage sectional area S3 of one exhaust pipe 28 is expressed as (S2 / S1) <(S3 / S2). That is, the degree of spread of the passage sectional area S2 of the intermediate exhaust passage 27 relative to the passage sectional area S1 of the independent exhaust passage 26 is relatively small, and compared with this, the passage sectional area of the exhaust pipe 28 relative to the passage sectional area S2 of the intermediate exhaust passage 27. The degree of spread of S3 is increased.

  In this embodiment, the negative pressure wave generated by the exhaust pulsation in the exhaust passage 25 reaches the exhaust port 7 during the overlap period OL of the intake and exhaust valves 8 and 9 so that the residual gas in the cylinder 2 is scavenged. An exhaust passage 25 is configured.

  That is, in each cylinder 2, a high positive pressure wave due to the blowdown gas is generated immediately after the exhaust valve 9 is opened, thereby causing exhaust pulsation in the exhaust passage 25. In this case, as described above, in the exhaust passage 25, since the relationship of (S2 / S1) <(S3 / S2) is established, the independent exhaust passages 26 of the cylinders 2 whose exhaust orders are not adjacent to each other are gathered. Most pressure waves pass through the first collecting portion 26a without being reflected, and the pressure waves are reflected by the second collecting portion 27a with the polarity reversed.

  Therefore, as shown in FIG. 5, the pressure wave reciprocates between the cylinder 2 and the second collecting portion 27a, and the positive pressure and the negative pressure are reversed at the second collecting portion 27a. As a result, negative pressure waves and positive pressure waves alternately reach the exhaust port 7, and as a result, the pressure waves reaching the exhaust port 7 are primary (first reciprocation), third (third reciprocation), 5 The next (5th reciprocation) is a negative pressure wave, the second (2nd reciprocation), the 4th (4th reciprocation), the 6th (6th reciprocation), etc. are positive pressure waves.

  As shown in FIG. 6, the pressure wave acting on the exhaust port 7 fluctuates. The pressure wave gradually attenuates as the reciprocation of the pressure wave is repeated while alternately changing to a negative pressure and a positive pressure.

  Thus, if the negative pressure wave generated by the exhaust pulsation in the exhaust passage 25 reaches the exhaust port 7 during the overlap period OL of the intake and exhaust valves 8 and 9, residual gas is sucked out from the cylinder 2 and the cylinder 2 The scavenging performance is improved.

  Here, the distance between the cylinder 2 and the second collecting portion 27a from which the pressure wave is reflected is fixed. Therefore, after the exhaust valve 9 is opened and the blowdown gas is jetted into the exhaust passage 25 at a high speed. While the time required for the negative pressure wave generated by the exhaust pulsation to reach the exhaust port 7 is constant, if the engine speed changes, the intake and exhaust air starts from the time when the positive pressure wave occurs immediately after the exhaust valve 9 is opened. Since the time until the overlap period OL of the valves 8 and 9 changes, the timing at which the negative pressure wave reaches the exhaust port 7 changes with respect to the overlap period OL.

  In the present embodiment, the distance between the cylinder 2 and the second collecting portion 27a where the pressure wave is reflected so that the primary negative pressure wave reaches the exhaust port 7 during the overlap period OL in the speed range near 5000 rpm. Is set. As a result, the third-order negative pressure wave reaches the exhaust port 7 during the overlap period OL in the speed range near 2500 to 3000 rpm, and the fifth-order negative pressure wave occurs during the overlap period OL in the speed range near 1500 to 2000 rpm. The exhaust port 7 is reached. In the present embodiment, the exhaust passage 25 is configured in this way, and thereby the scavenging efficiency of the cylinder 2 due to the negative pressure wave generated by exhaust pulsation is relatively enhanced in the low to medium speed range of the engine.

  As a result, in the engine according to the present embodiment, as shown in FIG. 7, the negative pressure wave generated by the exhaust pulsation in the exhaust passage 25 is generated in the intake and exhaust valves in the speed range of about 1500 to 2000 rpm, about 2500 to 3000 rpm, and about 5000 rpm. By reaching the exhaust port 7 during the overlap period OL of 8 and 9, the scavenging efficiency of the cylinder 2 is increased, the residual gas in the cylinder 2 is reduced, the volumetric efficiency is increased, and the high load range including the throttle full open range Torque is improved.

  However, on the other hand, there is a speed range in which the negative pressure wave does not reach the exhaust port 7 during the overlap period OL. Therefore, a speed range where the scavenging efficiency is high (that is, a scavenging good speed range) and a speed range where the scavenging efficiency is low (ie, Scavenging reduction speed range). In the scavenging reduction speed region, the high load region torque drops more than in the scavenging good speed region. As a result, a flat torque curve (engine performance curve) cannot be obtained, causing a shock.

  Returning to FIG. 1, the cooling mechanism 30 includes a cooling water pump 31 that pumps cooling water for engine cooling, a cooling water passage 32 through which the cooling water pumped by the cooling water pump 31 circulates, and a radiator 33 that cools the cooling water. And a switching valve 34 for switching the flow of the cooling water in the cooling water channel 32, and a water temperature sensor SN3 for detecting the temperature of the cooling water.

  The cooling water channel 32 introduces the cooling water discharged from the engine body 1 into the radiator 33 and the first water channel 32 a for returning the cooling water discharged from the engine body 1 to the engine body 1 again without passing through the radiator 33. And a third water channel 32c for introducing the cooling water discharged from the radiator 33 into the downstream portion of the first water channel 32a. The cooling water introduced into the engine main body 1 through the downstream portion of the first water passage 32a passes through an unillustrated water jacket or the like formed inside the cylinder block 3 and the cylinder head 4 of the engine main body 1, and then the engine. It is discharged from the main body 1 and led out to the upstream portion of the first water passage 32a or the second water passage 32b through the switching valve 34.

  The cooling water pump 31 is composed of, for example, a mechanical pump that obtains driving force from the crankshaft 15 of the engine body 1 and pumps the cooling water, and is located downstream of the junction between the third water passage 32c and the first water passage 32a. It is provided in the vicinity of the located engine body 1.

  The radiator 33 cools the cooling water by exchanging heat with the outside air, and is disposed at a predetermined position in the engine room where the traveling wind of the vehicle hits. For example, when the vehicle is a front engine type vehicle, a radiator 33 is disposed behind the front grill 35 provided in the front of the engine room, and the outside air introduced from the air inlet provided in the front grill 35. The (running wind) is blown to the radiator 33, whereby the cooling water in the radiator 33 is cooled.

  The switching valve 34 is composed of, for example, an electric detection type thermostat using a thermistor, and is provided at a branch portion between the first water channel 32a and the second water channel 32b. This switching valve 34 can be switched between a closed state in which the flow of the cooling water flowing into the second water passage 32b is blocked and an open state in which the flow of the cooling water into the second water passage 32b is allowed.

  Specifically, when the temperature of the cooling water detected by the water temperature sensor SN3 is lower than a predetermined reference temperature, the switching valve 34 is closed. At this time, since the cooling water circulates only through the first water passage 32a, the temperature of the cooling water gradually increases due to the heat generated in the engine body 1. On the other hand, when the temperature of the cooling water becomes equal to or higher than the reference temperature, the switching valve 34 is opened, and the cooling water flows into the second water channel 32b. That is, the cooling water led out from the engine body 1 not only circulates through the first water passage 32a but is also supplied to the radiator 33 through the second water passage 32b, and after being cooled by the radiator 33, the third water passage 32c, etc. Through the engine body 1 again. The opening degree of the switching valve 34 at this time can be continuously changed, and the flow rate of the cooling water flowing into the radiator 33 is arbitrarily adjusted by setting the opening degree. If the opening degree of the switching valve 34 is increased and the amount of cooling water flowing into the radiator 33 is increased, the cooling capacity of the cooling mechanism 30 is increased accordingly, and the cooling water temperature is rapidly lowered.

(2) Control System Next, the engine control system will be described with reference to FIG. Each part of the engine according to this embodiment is comprehensively controlled by an ECU (engine control unit) 50. As is well known, the ECU 50 includes a microprocessor including a CPU, a ROM, a RAM, and the like, and corresponds to the control means of the present invention.

  Information from various sensors is sequentially input to the ECU 50. Specifically, the ECU 50 is electrically connected to the engine speed sensor SN1, the airflow sensor SN2, and the water temperature sensor SN3 provided in each part of the engine. In addition, the vehicle according to the present embodiment includes an accelerator opening sensor SN4 that detects an opening degree of an accelerator pedal (accelerator opening degree) that is operated by a driver, and a shift position sensor that detects a gear position of the transmission 40. SN5 is provided, and the ECU 50 is also electrically connected to the accelerator opening sensor SN4 and the shift position sensor SN5. The ECU 50 acquires various information such as the engine speed, the intake air amount, the coolant temperature, the accelerator opening, and the gear stage of the transmission 40 based on the input signals from the sensors SN1 to SN5.

  ECU50 controls each part of an engine, performing various calculations etc. based on the input signal from each said sensor (SN1-SN5). That is, the ECU 50 is electrically connected to the injector 11, the spark plug 12, the intake VVT 18b, the exhaust VVT 19b, the throttle valve 24, and the switching valve 34, and is driven by these devices based on the calculation results and the like. Output control signal.

(3) Control according to operation state Next, the specific contents of the engine control according to the operation state will be described with reference to FIGS.

  The map in FIG. 9 is a map in which the rotation speed of the engine is taken on the horizontal axis and the engine load is taken on the vertical axis. In the figure, R1 is the idling speed of the engine, R2 is the boundary speed (for example, 2000 rpm) with the good scavenging speed area on the low speed side of the predetermined scavenging reduction speed area in FIG. 7, and R3 is the high speed side of the scavenging reduction speed area. A boundary speed with the good scavenging speed range (for example, 2500 rpm), R4 is a reference speed in the middle speed range of the engine, and R5 is a rated speed of the engine.

  As shown in this map, the operating region of the engine according to the present embodiment is a first operating region A that is set to include at least a region that is less than the reference speed R4 in the entire speed region in the low load region and the medium load region. And a second operating region B set in a region excluding the first operating region A in the middle load region, and a region less than the low speed side boundary speed R2 in the high load region including the throttle fully open region where the maximum load Lmax is obtained. The third operating region C1 set in the above, the fourth operating region C2 set in the region equal to or higher than the high speed side boundary speed R3 in the high load region, and the high speed above the low speed side boundary velocity R2 in the same high load region. It is divided into a fifth operation region D set in a region less than the side boundary speed R3. That is, the third operation region C1 and the fourth operation region C2 belong to the scavenging good speed range, and the fifth operation region D belongs to the scavenging reduction speed region.

  A control operation performed by the ECU 50 during operation of the engine will be specifically described with reference to the flowcharts of FIGS. In addition, as a premise that the process shown in this flowchart is executed, it is assumed that the engine is in a warm state, and thus the temperature of the cooling water is increased to a predetermined value (for example, 80 ° C.) or more.

  When the process shown in FIG. 10 starts, the ECU 50 executes a process of reading various sensor values (step S1). That is, the ECU 50 reads the detection signals from the engine speed sensor SN1, the airflow sensor SN2, the water temperature sensor SN3, the accelerator opening sensor SN4, and the shift position sensor SN5, and based on these signals, the engine speed, the suction Various information such as the amount of air, the temperature of the cooling water, the accelerator opening, and the gear stage of the transmission 40 is acquired.

  Next, the ECU 50 executes a process of determining whether or not the engine is operating in the first operation area A based on the information read in step S1 (step S2). That is, the ECU 50 specifies the engine load and rotation speed based on information obtained from the engine speed sensor SN1, the airflow sensor SN2, the accelerator opening sensor SN4, and the like, and the engine operating point obtained from both values is determined. It is determined whether or not it is included in the first operation area A shown in FIG.

When it is determined YES in step S2 and it is confirmed that the engine is operating in the first operating region A, the ECU 50 determines the temperature at which the switching valve 34 of the cooling mechanism 30 is opened (cooling to the radiator 33). A process of setting a predetermined normal reference temperature T _high as a reference temperature of the cooling water that is a temperature at which water inflow is allowed (step S3). Note that the value of the normal reference temperature T _high can be set to 88 ° C., for example.

Next, the ECU 50 performs a process of controlling the opening degree of the switching valve 34 so that the temperature of the engine coolant (hereinafter referred to as the coolant temperature Tw) is maintained at the normal reference temperature T _high set in step S3. Execute (step S4). Specifically, ECU 50 is cooling water temperature Tw is allowed to open the switching valve 34 as long as more than the normal reference temperature _{T high,} so that the cooling water temperature Tw is to close the switching valve 34 is less than the normal reference temperature _{T high} In addition, the opening degree of the switching valve 34 is controlled. Thus, the cooling water temperature Tw is the cooling water only when more than the normal reference temperature T _high is cooled and flows into the radiator 33, the cooling water temperature Tw is possible also without below greatly exceeds the normal reference temperature T _high, Its neighborhood value is maintained.

  Further, the ECU 50 sets the ignition timing of the spark plug 12 (ignition timing) to MBT, which is the timing at which torque is most generated (usually near the compression top dead center) (step S5), and sets the fuel injection amount from the injector 11 to three. The stoichiometric air-fuel ratio (λ = 1) at which the exhaust gas purification performance of the original catalyst is the best is set to a fuel injection amount that realizes (step S6).

  When it is determined NO in Step S2, the ECU 50 executes a process for determining whether or not the engine is operated in the first operation region B based on the information read in Step S1 (Step S7). . That is, the ECU 50 specifies the engine load and rotation speed based on information obtained from the engine speed sensor SN1, the airflow sensor SN2, the accelerator opening sensor SN4, and the like, and the engine operating point obtained from both values is determined. It is determined whether or not it is included in the second operation region B shown in FIG.

  When it is determined YES in step S7 and it is confirmed that the engine is operating in the second operation region B, the ECU 50 determines the gear of the current transmission 40 based on the information obtained from the shift position sensor SN5. A process of determining whether or not the level is equal to or higher than a predetermined level is performed (step S8). Here, as the “predetermined stage”, a higher stage (for example, a stage higher than half) among the plurality of gear stages of the transmission 40 is set. For example, when the transmission 40 has six forward gears, “4” can be set as the predetermined gear. At this time, if the gear stage is one of the first to third speeds, the determination in step S8 is NO, and if the gear stage is any of the fourth to sixth speeds, the determination in step S8 is YES.

When it is determined YES in step S8 and it is confirmed that the current gear stage is equal to or higher than the predetermined stage, the ECU 50 sets the normal temperature as the reference temperature of cooling water (the temperature at which the switching valve 34 is opened). A process of setting a _low temperature reference temperature T _low that is lower than the reference temperature T _high is executed (step S9). Note that the value of the _low temperature reference temperature T _low can be set to 78 ° C., for example. That is, when the engine operating point is in the second operating region B, the cooling capacity of the cooling mechanism 30 is set higher than when the engine is in the first operating region A (see step S3) (T _low <T _high ).

Next, the ECU 50 executes a process of determining whether or not the current engine coolant temperature Tw is equal to or higher than the _low temperature reference temperature T _low set in step S9 based on information obtained from the water temperature sensor SN3 ( Step S10). And when it determines with YES here and it is confirmed that it is Tw> = _Tlow , the process which opens the switching valve 34 and makes cooling water flow in into the radiator 33 is performed (step S11). Thereby, heat exchange is performed by the radiator 33, cooling water is cooled, and cooling water temperature Tw begins to fall. On the other hand, when the cooling water temperature Tw falls below the _low temperature reference temperature T _low (NO in step S10), the switching valve 34 is closed, so that the cooling does not proceed any further and the cooling water temperature Tw becomes a value near the _low temperature reference temperature T _low. Maintained.

Here, the opening degree of the switching valve 34 opened in the step S11 is set to be larger as the cooling water temperature Tw is higher than the _low temperature reference temperature T _low . That is, as the temperature difference (Tw−T _low ) between the actual cooling water temperature Tw and the low temperature reference temperature T _low is larger, the flow rate of the cooling water flowing into the radiator 33 is set, and the cooling capacity is enhanced. This is because as the temperature difference is larger, the cooling water temperature Tw is quickly lowered to approach the _low temperature reference temperature T _low .

For example, it is assumed that the cooling water temperature Tw immediately before the determination in step S10 is a value _close to the normal reference temperature T _high described above. In this case, in the determination of the step S10, the cooling water temperature Tw is significantly higher than the _low temperature reference temperature T _low (for example, when T _high = 88 ° C. and T _low = 78 ° C., it is about 10 ° C. higher). In step S11, the opening degree of the switching valve 34 is set to be sufficiently large. As a result, the amount of cooling water flowing into the radiator 33 is increased and the cooling capacity of the cooling mechanism 30 is sufficiently increased, so that the cooling water temperature Tw is rapidly lowered and the cooling of the engine body 1 is promoted.

  After cooling the cooling water as described above, the ECU 50 executes a process of retarding the ignition timing of the spark plug 12 by a predetermined amount from the MBT (step S12). In other words, the ignition timing of the spark plug 12 is set to MBT, which is the timing at which the torque is most generated (see step S5), as long as there is no particular trouble (see step S5), but in step S12, the ignition timing is set to a predetermined crank angle from the MBT. Set slower by minutes.

  The reason for retarding the ignition timing as described above is to avoid abnormal combustion in the second operation region B. That is, in the second operating region B located on the high speed side in the medium load region of the engine, the amount of heat generated per unit time is larger than that in the first operating region located on the low speed side. Remarkably, knocking is likely to occur. In order to avoid such knocking, the ignition timing is retarded in step S12. That is, the second operation region B is an engine operation region where the ignition timing is retarded to suppress knocking, that is, a retard region.

However, the retard amount (retard amount from MBT) in step S12 is set to a relatively small value. Specifically, the retard amount is set to be smaller than the retard amount set in step S17 (when the engine is operated in the third operation region C1 or the fourth operation region C2) described later. The reason is that the engine coolant temperature Tw is lowered to the _low temperature reference temperature T _low (steps S9 to S11), so that the environment in which knocking is likely to occur is improved. Therefore, even if the ignition timing retard amount is reduced, knocking is not caused. This is because it can be avoided.

  As shown in FIG. 9, the second operation region B is reduced toward a higher load as the speed decreases closer to the reference speed R4, and expanded toward a lower load as the speed approaches closer to the rated speed R5. The reason is that, since the amount of heat generated per unit time is large at high speed, once knocking occurs, it becomes a serious situation. For this reason, it is necessary to retard the ignition timing in a wide range up to a lower load at a high speed than at a low speed.

  Next, the ECU 50 sets the fuel injection amount from the injector 11 to a fuel injection amount that realizes the stoichiometric air-fuel ratio (λ = 1) that provides the best exhaust purification capability of the three-way catalyst (step S13).

  When it is determined NO in Step S7, the ECU 50 performs processing for determining whether or not the engine is operated in the third operation region C1 or the fourth operation region C2 based on the information read in Step S1. Execute (Step S14). That is, the ECU 50 specifies the engine load and rotation speed based on information obtained from the engine speed sensor SN1, the airflow sensor SN2, the accelerator opening sensor SN4, and the like, and the engine operating point obtained from both values is determined. It is determined whether or not it is included in the third operation region C1 or the fourth operation region C2 shown in FIG.

When it is determined YES in step S14 and it is confirmed that the engine is operating in the third operation region C1 or the fourth operation region C2, the ECU 50 switches the switching valve 34 of the cooling mechanism 30 as in step S3. Is set to a normal reference temperature T _high that is set in advance as the reference temperature of the cooling water that is the temperature at which the valve is opened (the temperature at which the cooling water is allowed to flow into the radiator 33) (step S15). . Note that the value of the normal reference temperature T _high can be set to 88 ° C., for example.

Next, as in step S4, the ECU 50 executes a process for controlling the opening of the switching valve 34 so that the engine coolant temperature Tw is maintained at the normal reference temperature T _high set in step S15 ( Step S16). Specifically, ECU 50 is cooling water temperature Tw is allowed to open the switching valve 34 as long as more than the normal reference temperature _{T high,} so that the cooling water temperature Tw is to close the switching valve 34 is less than the normal reference temperature _{T high} In addition, the opening degree of the switching valve 34 is controlled. Thus, the cooling water temperature Tw is the cooling water only when more than the normal reference temperature T _high is cooled and flows into the radiator 33, the cooling water temperature Tw is possible also without below greatly exceeds the normal reference temperature T _high, Its neighborhood value is maintained.

  Next, as in step S12, the ECU 50 executes a process of retarding the ignition timing of the spark plug 12 by a predetermined amount from the MBT (step S17). In other words, the ignition timing of the spark plug 12 is set to MBT, which is the timing at which the torque is most generated (see step S5), unless there is a particular problem (see step S5). Set slower by minutes.

  The reason for retarding the ignition timing as described above is to avoid abnormal combustion in the third operation region C1 or the fourth operation region C2. That is, since the third operation region C1 or the fourth operation region C2 is set to a high load region including the throttle fully open region, the fuel injection amount is increased and the generated heat amount is large, so the temperature rise of the cylinder 2 is remarkably increased. Knocking easily occurs. Therefore, in order to avoid such knocking, the ignition timing is retarded in step S17. That is, the third operation region C1 or the fourth operation region C2 is an engine operation region where the ignition timing is retarded to suppress knocking, that is, a retard region.

Moreover, the retard amount (retard amount from MBT) in step S17 is set to a relatively large value. Specifically, the retard amount is set to be larger than the retard amount set in the above-described step S12 (when the engine is operated in the second operation region B). The reason is that the engine coolant temperature Tw is maintained at the normal reference temperature T _high (steps S15 and S16), and the generated heat amount is excessive in the third operation region C1 or the fourth operation region C2 set in the high load region. Therefore, an environment in which knocking is likely to occur is maintained, and therefore it is necessary to avoid the knocking by increasing the retard amount of the ignition timing.

  Next, the ECU 50 sets the fuel injection amount from the injector 11 to a fuel injection amount that makes the air-fuel ratio richer than the stoichiometric air-fuel ratio (λ = 1) (step S18). The reason is that if the ignition timing is retarded (and the ignition timing is largely retarded in the third operation region C1 or the fourth operation region C2), the torque decreases, so it is necessary to increase the fuel injection amount to compensate for the torque. Because there is. In addition, when the ignition timing is retarded, the exhaust gas temperature rises because the fuel burns afterward or the expansion of the combustion gas decreases. Therefore, the temperature of the cylinder 2 is increased by increasing the fuel injection amount and the vaporization latent heat of the surplus fuel. This is because it needs to be lowered.

  If it is determined NO in step S8 and it is confirmed that the current gear stage is less than the predetermined stage, the ECU 50 executes steps S3 to S6. That is, the ECU 50 performs the same operation as when the engine is operated in the first operation region A, although the engine is operated in the second operation region B. However, since the operation content has already been described, description thereof will be omitted.

  Turning to FIG. 11, when it is determined NO in Step S <b> 14, that is, when it is confirmed that the engine is operating in the fifth operation region D, more specifically, the current engine rotation speed is the scavenging reduction speed. ECU 50 obtains from the shift position sensor SN5 in the same manner as in step S8, when the scavenging efficiency of the cylinder 2 due to the negative pressure wave generated by exhaust pulsation in the exhaust passage 25 is in a lower speed range than other speed ranges. Based on the obtained information, a process of determining whether or not the current gear position of the transmission 40 is equal to or higher than a predetermined predetermined position is executed (step S19). Here, as the “predetermined stage”, a higher stage (for example, a stage higher than half) among the plurality of gear stages of the transmission 40 is set. For example, when the transmission 40 has six forward gears, “4” can be set as the predetermined gear. At this time, if the gear stage is one of the first to third gears, the determination in step S19 is NO, and if the gear stage is any of the fourth to sixth gears, the determination in step S19 is YES.

When it is determined as YES in Step S19 and it is confirmed that the current gear stage is equal to or higher than a predetermined stage, the ECU 50 determines the reference temperature of the cooling water (the switching valve 34 is opened) as in Step S9. As the temperature, a process of setting a _low temperature reference temperature T _low that is lower than the normal reference temperature T _high is executed (step S20). Note that the value of the _low temperature reference temperature T _low can be set to 78 ° C., for example. That is, when the engine speed is in the scavenging reduction speed range, the cooling capacity of the cooling mechanism 30 is set higher than when there is no engine speed (that is, when the engine speed is in the scavenging good speed range: see step S15). _Yes (T _low <T _high ).

Next, as in step S10, the ECU 50 determines whether or not the current engine coolant temperature Tw is equal to or higher than the _low temperature reference temperature T _low set in step S20, based on information obtained from the water temperature sensor SN3. The process which performs is performed (step S21). And when it determines with YES here and it is confirmed that it is Tw> = _Tlow , the process which opens the switching valve 34 and makes cooling water flow into the radiator 33 is performed (step S22). Thereby, heat exchange is performed by the radiator 33, cooling water is cooled, and cooling water temperature Tw begins to fall. On the other hand, when the cooling water temperature Tw falls below the _low temperature reference temperature T _low (NO in step S21), the switching valve 34 is closed, so that the cooling does not proceed any further, and the cooling water temperature Tw becomes a value near the _low temperature reference temperature T _low. Maintained.

  After cooling the cooling water as described above, the ECU 50 executes a process of retarding the ignition timing of the spark plug 12 by a predetermined amount from the MBT (step S23), similarly to step S12. In other words, the ignition timing of the spark plug 12 is set to MBT, which is the timing at which the torque is most generated as long as there is no particular trouble (see step S5). In step S23, the ignition timing is set to a predetermined crank angle from the MBT. Set slower by minutes.

  The reason for retarding the ignition timing as described above is to avoid abnormal combustion in the fifth operation region D. That is, since the fifth operation region D is set to a high load region including the throttle full open region, similarly to the third operation region C1 and the fourth operation region C2, the fuel injection amount is increased and the generated heat amount is large. The temperature rise of the cylinder 2 is remarkable and knocking is likely to occur. In order to avoid such knocking, the ignition timing is retarded in step S23. That is, the fifth operation region D is an engine operation region in which ignition timing is retarded to suppress knocking, that is, a retard region.

However, the retard amount (retard amount from MBT) in step S23 is set to a relatively small value. Specifically, the retard amount is set to be smaller than the retard amount set in step S17 (when the engine is operated in the third operation region C1 or the fourth operation region C2). The reason is that the engine cooling water temperature Tw is lowered to the _low temperature reference temperature T _low (steps S20 to S22), so that the environment in which knocking is likely to occur is improved. Therefore, even if the ignition timing retard amount is reduced, knocking is not caused. This is because it can be avoided. That is, when the engine speed is in the scavenging reduction speed range, the retard amount is reduced (that is, the ignition timing is advanced) as compared with the case where there is no engine speed (that is, when the engine speed is in the scavenging good speed range: see step S17). Therefore, in the fifth operation region D belonging to this scavenging reduction speed region, the torque (high load region torque) increases, and the drop in the high load region torque in the scavenging reduction speed region is compensated.

  Next, as in step S18, the ECU 50 sets the fuel injection amount from the injector 11 to a fuel injection amount that makes the air-fuel ratio richer than the theoretical air-fuel ratio (λ = 1) (step S24). The reason is that if the ignition timing is retarded, the torque is reduced, so that it is necessary to increase the fuel injection amount to compensate for the torque. In addition, when the ignition timing is retarded, the exhaust gas temperature rises because the fuel burns afterward or the expansion of the combustion gas decreases. Therefore, the temperature of the cylinder 2 is increased by increasing the fuel injection amount and the vaporization latent heat of the surplus fuel. This is because it needs to be lowered. However, in the fifth operation region D, the retard amount is relatively reduced (step S23), so the richness of the air-fuel ratio in this step S24 is compared with the richness of the air-fuel ratio in the step S18. It will be minor.

  When it is determined NO in step S19 and it is confirmed that the current gear stage is less than the predetermined stage, the ECU 50 executes steps S15 to S18. That is, the ECU 50 performs the same operation as when the engine is operated in the fifth operation region D but is operated in the third operation region C1 or the fourth operation region C2. However, since the operation content has already been described, description thereof will be omitted.

(4) Action, etc. The spark ignition type engine according to the embodiment includes the cooling mechanism 30 that cools the engine body 1, the second operation region B, the third operation region C1, the fourth operation region C2, and the fifth operation region D. And an ECU 50 for retarding the ignition timing. In the exhaust passage 25 of the engine, the residual pressure in the cylinder 2 is scavenged when a negative pressure wave generated by exhaust pulsation in the exhaust passage 25 reaches the exhaust port 7 during the overlap period OL of the intake and exhaust valves 8 and 9. It is configured as follows. The third operation region C1 and the fourth operation region C2 belong to a speed region (scavenging good speed region) in which the scavenging efficiency is relatively high, and the fifth operation region D has a relatively high scavenging efficiency. It belongs to a low speed range (scavenging reduction speed range). The ECU 50 has the cooling capability of the cooling mechanism 30 in the fifth operation region D belonging to the scavenging reduction speed region even in the same high load region as compared to the third operation region C1 and the fourth operation region C2 belonging to the scavenging good speed region. A high value is set (T _low <T _{high in} step S20).

  According to the present embodiment, in the spark ignition type engine in which at least the high load region of the engine, that is, the third operation region C1, the fourth operation region C2, and the fifth operation region D are retard regions, the third to fifth operations. Of the regions C1, C2 and D, in the fifth operation region D belonging to the scavenging reduction speed region where the scavenging efficiency due to the negative pressure wave caused by the exhaust pulsation is relatively low, the scavenging efficiency due to the negative pressure wave caused by the exhaust pulsation is relatively high. Since the cooling capacity of the cooling mechanism 30 is set higher than in the third operation region C1 and the fourth operation region C2 that belong to the scavenging good speed region, in the fifth operation region D, the third operation region C1 and the second operation region C1. The cooling of the engine main body 1 is strengthened and the temperature of the engine main body 1 is lowered than in the four-operation region C2. Therefore, in the fifth operation region D, that is, the scavenging reduction speed region, knocking is suppressed and the retard amount can be reduced (ignition timing advance (advance)). Therefore, as shown by the chain line a in FIG. The torque drop in the decreasing speed range is compensated. As a result, a flat and high torque curve can be obtained, and an engine that is easy to handle with high torque can be realized.

  In particular, as described above, in the present embodiment, the effective compression ratio of the engine body 1 is 10 or more, which is a higher value for a gasoline engine, in a high load region (third to fifth operation regions C1, C2, D). Is set. For this reason, knocking is inherently likely to occur in the fifth operation region D, and as a tendency, the ignition timing retard amount in the fifth operation region D tends to increase. However, in the present embodiment, the cooling of the engine body 1 is strengthened in the fifth operation region D to reduce the retard amount. Therefore, as shown in FIG. 12, the ignition in the state where the retard amount is large even with the same advance amount. Since the advance of the torque is larger than that of the ignition advance when the retard amount is small, the effect of increasing the high load region torque is greater.

  As described above, according to the present embodiment, there is provided a control device for a spark ignition engine capable of improving the drop in the high load region torque in the scavenging reduction speed region.

In the embodiment, even when the operation is in the fifth operation region D, when the gear position of the transmission 40 is low (NO in step S19), the control for increasing the cooling capacity is not executed (step S15). in the reference temperature = T _high), it is possible to increase the cooling capacity without waste under proper conditions in consideration of the delay time until the temperature of the engine body 1 is actually reduced. That is, when the gear stage of the transmission 40 is low, there is a possibility that the operating point of the engine moves violently and the gear is shifted up immediately (the gear stage is changed to a high speed gear stage). For this reason, even if the cooling capacity is increased when the gear stage is low, when the temperature of each cylinder 2 of the engine body 1 actually decreases, it may have already moved to an operation region other than the fifth operation region D. This means that there is no point in increasing the cooling capacity. On the other hand, as in the above-described embodiment, the control for increasing the cooling capacity is performed when the gear stage of the transmission 40 is high, that is, the movement of the operating point is slow (that is, in a state close to cruising), and immediately When it is allowed only when it is predicted that the operation region D is not deviated, even if there is some delay time until the temperature of the engine body 1 actually decreases, Since it is considered that the temperature of the engine body 1 can be sufficiently lowered, the control for increasing the cooling capacity is not wasted.

  In particular, when the gear stage is low, when moving to a low speed region in the first operation region A as an operation region other than the fifth operation region D shown in FIG. That is, since the rotational speed is low in the low speed region, the moving speed of the piston 5 is slow, and therefore the fluidity or mixing of the air-fuel mixture in the cylinder 2 is liable to be reduced, and as a result, the time required for vaporization and atomization of the fuel is long. Thus, unburned HC (Raw HC) is likely to be generated. Therefore, it is not preferable that the temperature of the engine body 1 decreases in such a low speed region within the first operation region A. Further, when the temperature of the engine body 1 is lowered, various friction losses (sliding resistance of the piston 5 and the like) due to the increase in the viscosity of the engine oil are increased. Therefore, the engine body 1 is not required to be lowered in the region. Lowering the temperature is not preferable from the viewpoint of increasing friction loss. On the other hand, in the above embodiment, the control for increasing the cooling capacity is permitted only when the gear stage of the transmission 40 is high (that is, when it is predicted that the fifth operation region D cannot be immediately deviated). Such a problem that can occur when the cooling capacity is increased even though the gear stage is low is avoided.

  In the embodiment, as shown in FIG. 9, since the scavenging efficiency is low, the region where the cooling capacity of the cooling mechanism 30 is set high, that is, the fifth operation region D is predetermined in the medium speed region of the engine. The speed range is set to be lower than the reference speed R4. That is, even when the fifth operation region D is in the speed region below the reference speed R4, in other words, in the low speed region, control for setting the cooling capacity of the cooling mechanism 30 to be high is executed (steps S20 to S22). ). Thereby, the following operation is obtained.

  As described above, in the low speed region, since the rotational speed is low, the moving speed of the piston 5 is slow. Therefore, the fluidity or mixing of the air-fuel mixture in the cylinder 2 is likely to be lowered, and as a result, the fuel is atomized and atomized. Such time becomes longer, and unburned HC is likely to be generated. However, since the fifth operation region D belongs to the high load region, the scavenging efficiency is low, and a considerable amount of residual gas remains in the cylinder 2, the temperature of the cylinder 2 is high, and the vaporization mist of the fuel Is promoted. Therefore, even if the cooling of the engine main body 1 is enhanced in the fifth operation region D, fuel vaporization and atomization is not significantly inhibited. The effect of advancing the ignition timing (advancing) and increasing the high load region torque is greater than that.

  Therefore, in the embodiment, the cooling capacity is increased even if the fifth operation region D is in the low speed region. As a result, the drop in the high load region torque in the low speed region is compensated, and a flatter torque curve can be obtained.

In the above embodiment, the ECU 50 retards the ignition timing in the second operation region B, and the cooling capability of the cooling mechanism 30 is set higher in the second operation region B than in the first operation region A ( In step S9, T _low <T _high ). That is, in the spark ignition type engine in which the second operation region B is the retard region, the cooling capacity of the cooling mechanism 30 is set higher in the second operation region B that is the retard region than in the first operation region A that is not the retard region. Therefore, for the following reason, the problem of fuel consumption decrease that increases when the cooling capacity of the cooling mechanism 30 is not set high in the second operation region B that is the retard region is reduced.

  First, in the middle load region, the second operation region B is on the higher speed side than the first operation region A, and thus the amount of heat generated per unit time is large. Therefore, the second operation region B is a retard region in order to suppress knocking.

  When the ignition timing is retarded, the torque is reduced by that amount. Therefore, it is necessary to increase the fuel injection amount to compensate for the torque, resulting in a problem that the fuel consumption is lowered. In addition, when the ignition timing is retarded, the exhaust gas temperature rises because the fuel burns later or the expansion of the combustion gas decreases, so from the standpoint of preventing abnormal combustion, etc. The temperature of the cylinder 2 is lowered by the latent heat of vaporization. From this point, there is a problem that the fuel consumption is lowered.

Therefore, the ECU 50 sets the cooling capacity of the cooling mechanism 30 to be higher in the second operation region B that is the retard region than in the first operation region A that is not the retard region even in the same engine medium load region (in step S9). T _low <T _high ). Thereby, in the 2nd driving | operation area | region B, the cooling of the engine main body 1 is strengthened, the temperature of the engine main body 1 falls, and knocking is suppressed. Therefore, the retard amount can be reduced and the ignition timing can be advanced (if the engine is operated in the third operation region C1 or the fourth operation region C2, the retard amount is relatively increased in step S17). On the other hand, when the engine is operated in the second operation region B, the retard amount is relatively decreased in step S12 (that is, the ignition timing is advanced), and the torque is increased and the fuel consumption is increased. Will improve. Further, since the exhaust gas temperature decreases due to the reduction in the retard amount, the fuel injection amount can be reduced to make the air-fuel mixture lean (when the engine is operated in the third operation region C1 or the fourth operation region C2) If the air-fuel ratio is made richer (λ <1) than the stoichiometric air-fuel ratio in step S18, but the engine is operating in the second operating region B, the air-fuel ratio is made higher than that in step S13. A lean stoichiometric air-fuel ratio (λ = 1)). This also improves fuel efficiency.

  As described above, according to the present embodiment, the control of the spark ignition engine capable of reducing the problem of fuel consumption reduction in the second operation region B that is the retard region and improving the fuel consumption performance in the second operation region B. An apparatus is provided.

On the other hand, in the first operation region A in which the exhaust temperature does not rise to such an extent that the reliability is lowered even when retarded, the cooling capacity of the cooling mechanism 30 is set lower than that in the second operation region B (in step S3). (T _high > T _low ), the engine body 1 is not excessively cooled. In the first place, since the rotational speed is low in the low speed region, the moving speed of the piston 5 is slow, so that the fluidity or mixing of the air-fuel mixture in the cylinder 2 is likely to be reduced, and as a result, the time required for the vaporization and atomization of the fuel is reduced. It becomes long and unburned HC (Raw HC) is likely to be generated. On the other hand, according to the embodiment, since the engine body 1 is not excessively cooled in such a first operating region A, the above-described in-cylinder flow or mixing is not promoted. The increase in the amount of unburned HC generated is prevented. Further, since the engine body 1 is not excessively cooled, an increase in various friction losses (such as sliding resistance of the piston 5) due to an increase in the viscosity of the engine oil is also prevented. Accordingly, a reduction in fuel consumption is prevented even in the first operation region A that is not the retard region.

  Further, in the engine according to the embodiment, the geometric compression ratio of the engine body 1 is set to 12 or more, and a high compression ratio is set as a gasoline engine. On the other hand, in the above embodiment, the cooling water temperature Tw is controlled as described above, and the fuel efficiency performance in the retard region is improved. Therefore, in combination with the improvement of the thermal efficiency accompanying the increase in the compression ratio, it is more excellent. It becomes possible to obtain fuel consumption performance.

  In the above-described embodiment, the cooling temperature of the cooling mechanism 30 is increased by lowering the reference temperature that is the temperature at which the switching valve 34 opens (that is, allowing the cooling water to flow into the radiator 33 from a lower temperature condition). Although the cooling capacity is increased, the cooling capacity can be increased by another method not depending on the change of the reference temperature as described above.

  For example, an electric pump driven by an electric motor may be provided as the cooling water pump 31, and the cooling capacity may be controlled by changing the flow rate of the cooling water by adjusting the rotation speed of the electric motor. .

  Alternatively, a grill shutter may be provided as a device for increasing the cooling capacity of the cooling mechanism 30. The grill shutter is housed in a front grill disposed in front of the radiator 33 and adjusts the opening area of the air inlet of the front grill to be increased or decreased. If the opening area of the front grille is increased by the grill shutter and the flow rate of the air (running wind) blown to the radiator 33 is increased (increased), the cooling capacity of the cooling mechanism 30 is increased accordingly, and the cooling water temperature is rapidly increased. Will be reduced.

  Therefore, by adjusting the flow rate of air (running wind) blown to the radiator from the air inlet port of the front grill by controlling the opening and closing of the grill shutter, the amount of heat conversion in the radiator is adjusted and changed. The cooling capacity of the cooling mechanism 30 can be adjusted and controlled appropriately and reliably.

  Alternatively, a fan may be used instead of the grille shutter, and the fan may be rotationally driven to apply air (wind) to the radiator 33 to adjust the air volume of the air.

  Moreover, in the said embodiment, although the geometric compression ratio of the engine main body 1 was set to 12 or more, when gasoline with a high octane number (RON) is used as a fuel, abnormal combustions, such as knocking, do not occur relatively easily. Therefore, the geometric compression ratio may be set higher. Specifically, when gasoline having an octane number of 95 or more is used as a fuel, the geometric compression ratio can be 13 or more. Conversely, when the octane number is 91 or more and less than 95, the geometric compression ratio is preferably 12 or more as in the above embodiment.

  In the embodiment, the air-fuel ratio is set to the stoichiometric air-fuel ratio in step S13 (λ = 1). However, it is sufficient that the air-fuel ratio is lean as compared with the case where the cooling capacity of the cooling mechanism 30 is not increased. There is no need.

1 Engine body 2 Cylinder 15 Crankshaft (output shaft)
DESCRIPTION OF SYMBOLS 30 Cooling mechanism 32 Cooling water channel 33 Radiator 34 Switching valve 40 Transmission 50 ECU (control means)
A 1st operation area B 2nd operation area C1 3rd operation area C2 4th operation area D 5th operation area R4 Reference speed

Claims (6)

A spark ignition engine control device comprising a cooling mechanism for cooling an engine body and a control means for retarding ignition timing at least in a high load region of the engine,
Said exhaust passage to enhance the scavenging efficiency of the residual gas in cylinders by causing reach the exhaust port during the overlap period the intake and exhaust valves of the negative pressure wave generated by the exhaust pulsation in the exhaust passage at a predetermined engine speed range Configured,
Wherein, in the region of more than a predetermined load including a maximum load of the high load region, in the predetermined engine speed range the engine speed range other than, than the predetermined engine speed range, the cooling A control device for a spark ignition engine characterized by setting a high cooling capacity of the mechanism. The control device for a spark ignition engine according to claim 1,
The engine is an in-vehicle engine mounted on a vehicle,
The output shaft of the engine body is connected to wheels via a transmission having a plurality of gear stages,
The control device for a spark ignition engine, wherein the control means executes control for setting the cooling capacity of the cooling mechanism to be high only when a gear stage of the transmission is a predetermined level or higher. In the control device for the spark ignition engine according to claim 1 or 2,
The control device for a spark ignition type engine, wherein a region in which the cooling capacity of the cooling mechanism is set high because the scavenging efficiency is low is set to a speed region that is less than a predetermined reference speed. The control device for a spark ignition engine according to any one of claims 1 to 3,
The control means retards the ignition timing in a medium load range in the high speed range of the engine, and the cooling capacity of the cooling mechanism is set higher in the high speed range in the medium load range than in the low speed range in the medium load range. A control device for a spark ignition type engine. A spark ignition engine control device comprising a cooling mechanism for cooling an engine body and a control means for retarding ignition timing at least in a high load region of the engine,
  The engine is an in-vehicle engine mounted on a vehicle,
  The output shaft of the engine body is connected to wheels via a transmission having a plurality of gear stages,
  The exhaust passage is configured such that a negative pressure wave caused by exhaust pulsation in the exhaust passage reaches the exhaust port during the overlap period of the intake and exhaust valves, thereby scavenging residual gas in the cylinder,
  The control means sets the cooling capacity of the cooling mechanism higher in the speed range where the efficiency of the scavenging is lower than the other speed range in the high load range, and the cooling mechanism A control device for a spark ignition engine, wherein control for setting a high cooling capacity is executed only when a gear stage of the transmission is equal to or higher than a predetermined stage. A spark ignition engine control device comprising a cooling mechanism for cooling an engine body and a control means for retarding ignition timing at least in a high load region of the engine,
  The exhaust passage is configured such that a negative pressure wave caused by exhaust pulsation in the exhaust passage reaches the exhaust port during the overlap period of the intake and exhaust valves, thereby scavenging residual gas in the cylinder,
  The control means sets the cooling capacity of the cooling mechanism higher in the speed range where the efficiency of the scavenging gas is lower than the other speed range in the high load range, and increases the engine speed. Ignition timing is retarded in the medium load range in the region, and the cooling capacity of the cooling mechanism is set higher in the high speed region in the medium load region than in the low speed region in the medium load region. Type engine control device.

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