JP2015124667A - Exhaust device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine capable of detecting the air-fuel ratio of exhaust gas exhausted from a plurality of cylinders for each cylinder while suppressing pressure loss of exhaust gas.SOLUTION: In an exhaust device of an engine having four cylinders detecting an air-fuel ratio in an exhaust collection part, between a third cylinder #3 and a fourth cylinder #4 whose exhaust periods are overlapped, the opening valve timing of an exhaust valve of the fourth cylinder #4 performing exhaust later, with respect to a bottom dead center (BDC) is set earlier than the opening valve timing of the exhaust valve of the third cylinder #3 performing exhaust ahead, with respect to the bottom dead center (BDC).

Description

  The present invention relates to an exhaust system for an engine having a plurality of cylinders, and more particularly, to an exhaust system for an engine having an air-fuel ratio sensor in an exhaust collection section where exhaust passages gather.

  An engine installed in an engine room of an automobile is provided with a plurality of cylinders, an exhaust passage provided for each cylinder, and an exhaust collecting portion where the exhaust passages gather. In addition, an air-fuel ratio sensor is installed in the exhaust collecting section, and exhaust gas discharged from a plurality of cylinders hits the air-fuel ratio sensor in the order of exhaust, and the air-fuel ratio of the exhaust gas is obtained for each cylinder.

  Patent Document 1 describes an engine in which the opening timing of the exhaust valve of the cylinder in the exhaust stroke is delayed from the opening timing of the intake valve of the cylinder in the intake stroke. According to this engine, the exhaust start timing of the cylinder in the exhaust stroke is delayed from the intake timing of the cylinder in the intake stroke, so that the intake efficiency of the cylinder in the exhaust stroke is improved and the output of the engine is increased.

  In Patent Document 2, the first exhaust system in which the exhaust passage of the first cylinder and the exhaust passage of the second passage are gathered, and the second exhaust system in which the exhaust passage of the third cylinder and the exhaust passage of the fourth cylinder are gathered. In an engine having an exhaust system, it has been proposed to advance the opening / closing timings of the exhaust valves of the first cylinder and the fourth cylinder and to delay the opening / closing timings of the second cylinder and the third cylinder. According to this engine, exhaust pulsation can be strengthened even at a low speed with a small displacement.

JP 2000-248948 A Japanese Examined Patent Publication No. 7-109172

  Incidentally, as described above, in order for the exhaust gas discharged from the plurality of cylinders 131 to hit the air-fuel ratio sensor 147 in the discharge order (ignition order), the volume of the exhaust collecting portion 1453 is set to be small as shown in FIG. It is preferable. However, if the volume of the exhaust collecting portion 1453 is set to be small as described above, the pressure loss of the exhaust gas increases, which causes a decrease in engine performance.

  On the other hand, as shown in FIG. 6, when the volume of the exhaust collecting portion 2453 is set to be large, the exhaust gas discharged from the cylinder in the previous exhaust order remains around the air-fuel ratio sensor 243, and the detected exhaust gas from which cylinder 231 It will not be possible to determine whether it has been discharged.

  In view of the above circumstances, an object of the present invention is to provide an engine exhaust device that can detect the air-fuel ratio of exhaust gas discharged from a plurality of cylinders for each cylinder while suppressing pressure loss of the exhaust gas.

The present invention provides an exhaust system for an engine having a plurality of cylinders, in which an air-fuel ratio sensor is installed in the vicinity of an exhaust collecting portion, and detects the air-fuel ratio for each cylinder, between two cylinders having overlapping exhaust periods. The opening characteristic of the exhaust valve of the cylinder that exhausts from is different from the opening characteristic of the exhaust valve of the cylinder that exhausts first.
According to the present invention, the flow of exhaust gas discharged from a cylinder exhausted first or the flow of exhaust gas discharged from a cylinder exhausted later is changed between two cylinders having overlapping exhaust periods. As a result, the exhaust gas discharged from the cylinder exhausted first can be distinguished from the exhaust gas discharged from the cylinder exhausted later, and the air-fuel ratio of the exhaust gas can be detected for each cylinder.

In one aspect of the present invention, the valve opening characteristic includes a change in valve opening timing and a valve opening lift amount, and the opening timing of the exhaust valve of the cylinder that exhausts the valve opening timing of the exhaust valve of the cylinder that is exhausted later is exhausted first. It is preferable to make the change rate of the lift amount of the exhaust valve small while making it earlier than the timing.
In this way, the flow of the exhaust gas discharged from the cylinder that is exhausted first is changed by the exhaust gas that is exhausted from the cylinder that is exhausted later between the two cylinders in which the exhaust periods overlap. Further, the initial flow of exhaust gas discharged from the cylinder exhausting from Ato is suppressed. Thereby, the exhaust gas discharged from the cylinder exhausted first and the exhaust gas discharged from the cylinder exhausted later can be distinguished, and the air fuel consumption of the exhaust gas can be detected for each cylinder.

In the aspect of the invention, it is preferable that the exhaust collecting portion is formed in the cylinder head.
In this way, the catalyst can be disposed close to the engine. If the catalyst is arranged close to the engine, the catalyst is warmed early after the engine is started, and the activity of the catalyst is enhanced. As a result, the exhaust gas is purified early after the engine is started, and the exhaust gas can be improved.

In one aspect of the present invention, the engine includes four cylinders arranged in a longitudinal direction, and includes an outer cylinder and an inner cylinder adjacent to the outer cylinder. And the outer cylinder, the exhaust passage of the outer cylinder is longer than the exhaust passage of the inner cylinder, and the opening timing of the exhaust valve of the outer cylinder is made earlier than the opening timing of the inner cylinder and the outer cylinder. It is preferable to reduce the rate of change of the lift amount of the exhaust valve of the inner cylinder.
In this way, it is possible to distinguish between the exhaust gas discharged from the inner cylinder and the exhaust gas discharged from the outer cylinder, and the air fuel consumption of the exhaust gas discharged from the inner cylinder and the air fuel consumption of the exhaust gas discharged from the outer cylinder. Can be distinguished and detected.

  As described above, according to the present invention, it is possible to distinguish the exhaust gas discharged from the cylinder exhausted first from the exhaust gas discharged from the cylinder exhausted later. It can be detected.

It is a mimetic diagram showing composition of an engine concerning an embodiment of the invention. It is a figure which shows the relationship between the crank angle of the conventional engine, the lift amount of an exhaust valve, and exhaust flow volume. It is a figure which shows the relationship between the crank angle of the engine which concerns on embodiment of this invention, the lift amount of an exhaust valve, and exhaust flow volume, Comprising: The valve opening timing and valve opening speed of the front side exhaust valve of the 4th cylinder were adjusted FIG. It is a schematic diagram showing the flow of the exhaust gas of the engine according to the embodiment of the present invention, and is a diagram showing the adjusted opening timing and opening speed of the front exhaust valve of the fourth cylinder. It is a schematic diagram which shows the flow of the exhaust gas of the engine which set the volume of the exhaust gas collection part small. It is a schematic diagram which shows the flow of the exhaust gas of the engine which set the volume of the exhaust gas collection part large.

  Embodiments of an engine exhaust device according to the present invention will be described below in detail with reference to the accompanying drawings. The present invention is not limited to the embodiment.

  FIG. 1 is a schematic diagram showing a configuration of an engine according to an embodiment of the present invention. An engine according to an embodiment of the present invention is an in-line four-cylinder engine installed in an engine room of an automobile, and as shown in FIG. 1, an engine body 2, a variable valve timing mechanism 5, a fuel injection device 6, An ECU 7 is provided.

  The engine body 2 includes a cylinder block 3 and a cylinder head 4 fixed on the cylinder block 3. Four cylinders 31 are formed in a row in the cylinder block 3, and one crankshaft 32 common to the four cylinders 31 is rotatably supported in the lower region thereof. The cylinder 31 is formed in a cylindrical shape, and a piston 33 is accommodated therein so as to be capable of reciprocating in the vertical direction. The piston 33 is formed in a cylindrical shape with a closed head portion, and a pin hole 33a penetrating in the radial direction is provided in the body portion thereof. One end (small end) of the connecting rod 34 is accommodated in the body portion of the piston 33, and one end of the connecting rod 34 is connected to the piston 33 by a piston pin 35 inserted through the pin hole 33 a.

  The crankshaft 32, together with the connecting rod 34, converts the reciprocating motion (downward motion) of the piston 33 into a rotational motion, and has a crankpin 321 parallel to an axis passing through the rotational center of the crankshaft 32. . The crank pin 321 is connected to the other end (large end) of the connecting rod 34. Thereby, the reciprocating motion of the piston 33 is converted into a rotational motion.

  A combustion chamber 41 is formed in the cylinder head 4 at a position corresponding to the cylinder 31 formed in the cylinder block 3. The cylinder head 4 is provided with intake ports 42F and 42R and exhaust ports 43F and 43R for each combustion chamber 41. In the embodiment of the present invention, two intake ports 42F and 42R and two exhaust ports 43F and 43R are formed for each combustion chamber 41, and these are aligned in a line in the cylinder arrangement direction.

  The cylinder head 4 is formed with an intake passage 44 communicating with the intake ports 42F and 42R and an exhaust passage 45 communicating with the exhaust ports 43F and 43R. The exhaust passage 45 has a branch passage 451 communicating with the exhaust ports 43F and 43R, and a trunk passage 452 where the branch passage 451 joins. After joining each combustion chamber 41, the exhaust collecting portion 453 (see FIGS. 4 and 4). 6).

  A catalyst 46 (see FIGS. 4 and 6) is provided in the exhaust collecting portion 453. As a result, the exhaust gas that has gathered through the exhaust passage 45 and gathered at the exhaust collecting portion 453 is purified through the catalyst 46 and discharged to the outside. An air-fuel ratio sensor 47 (see FIGS. 4 and 6) is provided on the upstream side of the catalyst. The air-fuel ratio sensor 47 detects an air-fuel ratio of exhaust gas (ratio of fuel to air), and is provided substantially at the center of the exhaust collecting portion 453. In the present embodiment, LAFS (Linear Air-Fuel ratio sensor) capable of detecting a continuous change in the air-fuel ratio is used for the air-fuel ratio sensor 47.

  In addition, intake valves 48F and 48R for opening and closing the intake ports 42F and 42R are attached to the intake ports 42F and 42R, respectively. The intake ports 42F and 42R are opened during the intake stroke, air can be sucked from the intake ports 42F and 42R, and are closed during the compression stroke, the expansion stroke, and the exhaust stroke. Similarly, exhaust valves 49F and 49R for opening and closing the exhaust ports 43F and 43R are attached to the exhaust ports 43F and 43R, respectively. The exhaust ports 43F and 43R are opened in the exhaust stroke, the exhaust gas can be discharged from the exhaust ports 43F and 43R, and are closed in the intake stroke, the compression stroke, and the expansion stroke. Thereby, the combustion chamber 41 is closed in the compression stroke and the expansion stroke.

  The variable valve timing mechanism 5 includes an intake side variable valve timing mechanism 51 installed on the intake side, an intake camshaft 511 that drives the intake valves 48F and 48R, and an exhaust side variable valve timing mechanism 52 installed on the exhaust side. The exhaust camshaft 521 that drives the exhaust valves 49F and 49R. The camshafts 511 and 521 are provided with cam portions corresponding to the intake and exhaust valves (48F, 48R, 49F, and 49R), and intake valves (48F and 48R) and exhaust valves (49F and 49R) according to the profile of the cam portions. The lift amount and valve closing timing of each valve can be set. The variable valve timing mechanisms 51 and 52 vary the phase of the camshafts 511 and 521 with respect to the crankshaft 32. By varying the phase of the camshafts 511 and 521, the intake valves 48F and 48R and the exhaust valves 49F, The opening / closing timing of 49R is variable, and is provided on the intake side and the exhaust side in the embodiment of the present invention. That is, the intake side variable valve timing mechanism 51 can arbitrarily set the opening / closing timing of the intake valves 48F, 48R. Similarly, the exhaust side variable valve timing mechanism 52 provided on the exhaust side can arbitrarily set the opening and closing timings of the exhaust valves 49F and 49R. Thereby, the opening / closing timing, lift amount, and opening / closing speed of each valve 48F, 48R can be set by the profile of the camshaft, and can be set for each intake port 42F, 42R or each combustion chamber 41. Similarly, the opening / closing timing, the lift amount, and the opening / closing speed (the rate of change of the lift amount with respect to the crank angle) of the exhaust valves 49F, 49R can be set for each exhaust port 43F, 43R or each combustion chamber 41.

  The fuel injection device 6 is for injecting pressurized fuel into a cylinder, and includes a fuel pump 61 and an injector 62. The fuel pump 61 is provided with a fuel pressure sensor 611 and monitors the pressure of the fuel pump 61. The injector 62 is disposed in the intake ports 42F and 42R and finely controls the fuel injection amount and the fuel injection timing.

  An ECU (Engine Control Unit) 7 is a control device that comprehensively controls the engine. In the present embodiment, the variable valve timing mechanism 5 (the intake side variable valve timing mechanism 51, the exhaust side variable valve timing mechanism) described above is used. 52) The fuel injection device 6 is comprehensively controlled. Specifically, by controlling the intake side variable valve timing mechanism 51 installed on the intake side, the opening / closing timing of the intake valves 48F and 48R is controlled, and the exhaust side variable valve timing mechanism 52 installed on the exhaust side is controlled. By controlling, the opening / closing timing of the exhaust valves 49F, 49R is controlled.

  FIG. 2 is a diagram showing the relationship between the crank angle of a conventional engine, the lift amount of the exhaust valve, and the exhaust flow rate. FIG. 3 is a diagram showing the relationship between the crank angle of the engine according to the embodiment of the present invention, the lift amount of the exhaust valve, and the exhaust flow rate, and shows the valve opening timing and valve opening speed of the exhaust valve of the fourth cylinder. It is a figure which shows what was adjusted. FIG. 4 is a schematic diagram showing the flow of exhaust gas from the engine according to the embodiment of the present invention, and is a diagram showing the adjusted opening timing and opening speed of the exhaust valve of the fourth cylinder.

  As shown in FIG. 4, the engine according to the embodiment of the present invention is installed in an automobile engine room (not shown) such that cylinders 31 are arranged in the vehicle longitudinal direction. In the following description, the engine cylinder 31 is referred to as a first cylinder # 1, a second cylinder # 2, a third cylinder # 3, and a fourth cylinder # 4 from the front of the vehicle toward the rear of the vehicle. Further, as shown in FIG. 2, the engine described here has the ignition order of the first cylinder # 1, the third cylinder # 3, the fourth cylinder # 4, the second cylinder # 2, and the exhaust order. The order is the first cylinder # 1, the third cylinder # 3, the fourth cylinder # 4, and the second cylinder # 2.

  Further, as described above, the engine according to the embodiment of the present invention is provided with two exhaust ports 43F and 43R for each cylinder (cylinder) 31, and these are aligned in a line from the front of the vehicle to the rear of the vehicle. doing. Further, as described above, exhaust valves 49F and 49R are attached to the exhaust ports 43F and 43R, respectively.

  Further, as shown in FIGS. 2 and 3, when the top dead center (TDC (Top Dead Center)) in the intake stroke of the first cylinder # 1 is used as a reference (crank angle is 0 degree), the first cylinder # 1 Is an exhaust stroke from -180 degrees to 0 degrees in crank angle, an intake stroke from 0 degrees to 180 degrees, a compression stroke from 180 degrees to 360 degrees, and an expansion stroke from 360 degrees to 540 degrees. Similarly, the third cylinder # 3 has a crank angle, from -180 degrees to 0 degrees is an expansion stroke, from 0 degrees to 180 degrees is an exhaust stroke, and from 180 degrees to 360 degrees is an intake stroke, from 360 degrees to 540 Up to the degree is the compression stroke. The fourth cylinder # 4 has a crank angle, a compression stroke from -180 degrees to 0 degrees, an expansion stroke from 0 degrees to 180 degrees, an exhaust stroke from 180 degrees to 360 degrees, and 360 degrees to 540 degrees. Up to the intake stroke. Cylinder # 2 has a crank angle of −180 degrees to 0 degrees as an intake stroke, 0 degrees to 180 degrees as a compression stroke, 180 degrees to 360 degrees as an expansion stroke, 360 degrees to 540 degrees. Exhaust stroke.

  As shown in FIG. 2, the engine according to the embodiment of the present invention includes the opening / closing timings of the exhaust valves 49F and 49R, the opening speeds of the exhaust valves 49F and 49R, and the lift amounts of the exhaust valves 49F and 49R in all cylinders. Are set the same. If the engine is driven in this state, the exhaust may be mixed or the exhaust may bypass the air-fuel ratio sensor 47 depending on the shape of the exhaust passage 45, the length of the exhaust path, and the like. In this case, it cannot be determined from which cylinder the exhaust gas detected by the air-fuel ratio sensor 47 is discharged.

  For example, in an engine having the characteristic that the exhaust gas discharged from the third cylinder # 3 remains around the air-fuel ratio sensor 47, is the air-fuel ratio sensor 47 detecting the exhaust gas discharged from the third cylinder # 3? It cannot be determined whether the exhaust gas discharged from the numbered cylinder # 4 is detected. In this case, it is also assumed that the exhaust gas discharged from the fourth cylinder # 4 bypasses the air-fuel ratio sensor 47.

  In this case, the exhaust valves 49F and 49R are opened with respect to the bottom dead center (BDC (Bottom Dead Center)) of the cylinders that are continuously ignited and are exhausted later between the two cylinders in which the exhaust periods overlap. A cylinder whose timing is earlier than the opening timing of the exhaust valves 49F and 49R with respect to the bottom dead center (BDC) of the cylinder to be exhausted first, and the opening speed of the exhaust valves 49F and 49R of the cylinder to be exhausted later is exhausted first The exhaust valve 49F, 49R is made slower than the valve opening speed.

  In the above-described example, as shown in FIG. 3, the exhaust timing of the exhaust valves 49F and 49R of the fourth cylinder # 4 is adjusted by adjusting the profile of the exhaust camshaft, so that the conventional one shown by the two-dot chain line in FIG. In addition, the valve opening speed of the fourth cylinder # 4 is made slower than that of the conventional one as well as by 5 ° to 10 °. In this way, the exhaust timing of the exhaust valves 49F and 49R for the bottom dead center (BDC) of the fourth cylinder # 4 is earlier than the exhaust timing for the bottom dead center (BDC) of the third cylinder # 3. The valve opening speed of the cylinder # 4 is slower than the valve opening speed of the third cylinder # 3. As a result, the rising angle of the lift amount of the exhaust valves 49F and 49R of the fourth cylinder becomes slower than the rising angle of the lift amount of the exhaust valves 49F and 49R of the third cylinder.

  For example, if the opening of the exhaust valves 49F and 49R is started at 3 to 60 degrees before the bottom dead center (BBDC (Before Bottom Dead Centerer)) in the third cylinder # 3, the fourth cylinder # 4 is before the bottom dead center ( (BBDC) The opening of the exhaust valves 49F and 49R is started at 8 to 65 ° (when 5 ° is advanced). Accordingly, the exhaust valves 49F and 49R of the fourth cylinder # 4 can be opened more slowly than the exhaust valves 49F and 49R of the third cylinder # 3. With this setting, even if the engine has such a characteristic that the exhaust gas E3 exhausted from the third cylinder # 3 remains around the air-fuel ratio sensor 47 as shown in FIG. The exhaust gas E4 that remains around the air-fuel ratio sensor 47 (exhaust gas E3 discharged from the third cylinder # 3) can be removed. As a result, the exhaust gas E4 discharged from the fourth cylinder # 4 hits the air-fuel ratio sensor 47, and the exhaust gas discharged from the fourth cylinder # 4 can be reliably detected.

  Further, in the above-described embodiment, the valve opening timing of the third cylinder # 3 is advanced by 5 ° to 10 ° from the conventional one shown by the two-dot chain line in FIG. 3 by adjusting the profile of the exhaust camshaft. In the exhaust stroke of the third cylinder # 3, the exhaust camshaft phase is advanced by 5 ° to 10 ° using the variable valve timing mechanism 52 on the exhaust side, so that the exhaust resistance can be reduced without changing the cam profile for each cylinder. It is also possible to reduce the valve opening characteristics of the exhaust valves 41F and 41R by using both the adjustment of the valve opening timing by the cam profile and the variable valve timing mechanism 51 described above.

  As described above, the engine according to the embodiment of the present invention is a cylinder in which ignition continues, and a cylinder that exhausts later between two cylinders having overlapping exhaust periods (in the above example, the fourth cylinder). The flow of the exhaust gas discharged from the cylinder (the third cylinder # 3 in the above example) from which the exhaust gas flow discharged from # 4) first exhausts is changed. As a result, even if the engine has the characteristic that the exhaust gas exhausted from the cylinder exhausted first remains around the air-fuel ratio sensor 47, it is exhausted from the exhaust gas exhausted from the cylinder exhausted first and the cylinder exhausted later. The exhaust gas can be distinguished from each other, and the air-fuel ratio of the exhaust gas can be detected for each cylinder.

  Further, the exhaust valve of the cylinder (the third cylinder # 3 in the above example) that exhausts the valve opening speed of the exhaust valves 49F and 49R of the cylinder that is exhausted later (the fourth cylinder # 4 in the above example) first. Since the valve opening speed of 49F and 49R is slower, the initial flow of exhaust gas discharged from a cylinder to be exhausted later (fourth cylinder # 4 in the above example) is suppressed, and the first exhausted cylinder (the above example) Then, the influence on the flow of the exhaust gas discharged from the third cylinder # 3) can be reduced.

  Further, since the exhaust collecting portion 453 of the exhaust passage 45 is formed in the cylinder head 4, the catalyst 46 can be disposed close to the engine body 2. As described above, if the catalyst 46 is disposed close to the engine body 2, the catalyst is warmed early after the engine is started, and the activity of the catalyst 46 is enhanced. As a result, the exhaust gas is purified early after the engine is started, and the exhaust gas can be improved.

  The present invention can detect the air-fuel ratio of exhaust gas discharged from a plurality of cylinders for each cylinder while suppressing pressure loss of the exhaust gas, and is therefore suitable for an exhaust device for an automobile engine.

2 Engine body 3 Cylinder block 31 Cylinder 32 Crankshaft 33 Piston 4 Cylinder head 41 Combustion chamber 42F, 42R Intake port 43F, 43R Exhaust port 44 Intake passage 45 Exhaust passage 451 Branch passage 452 Trunk passage 453 Exhaust collecting portion 46 Catalyst 47 Air fuel ratio Sensor 48F, 48R Intake valve 49F, 49R Exhaust valve 5 Variable valve timing mechanism 51 Intake side variable valve timing mechanism 52 Exhaust side variable valve timing mechanism 6 Fuel injection device 7 ECU
# 1 1st cylinder # 2 2nd cylinder # 3 3rd cylinder # 4 4th cylinder

Claims (4)

In an exhaust system of an engine that has a plurality of cylinders, an air-fuel ratio sensor is installed in the vicinity of an exhaust collecting portion, and detects an air-fuel ratio for each cylinder,
An exhaust system for an engine, characterized in that, between two cylinders whose exhaust periods overlap, an opening characteristic of an exhaust valve of a cylinder that is exhausted later is different from an opening characteristic of an exhaust valve of a cylinder that is exhausted first. The valve opening characteristics consist of changes in valve opening timing and valve opening lift amount,
2. An opening timing of an exhaust valve of a cylinder that is exhausted later is made earlier than an opening timing of an exhaust valve of a cylinder that is exhausted first, and a change rate of a lift amount of the exhaust valve is reduced. An exhaust system for an engine according to 1.   The engine exhaust system according to claim 1 or 2, wherein the exhaust collecting portion is formed in a cylinder head. The engine includes four cylinders arranged in the longitudinal direction, and includes an outer cylinder and an inner cylinder adjacent to the outer cylinder,
The two cylinders whose exhaust periods overlap are the inner cylinder and the outer cylinder,
The exhaust passage of the outer cylinder is longer than the exhaust passage of the inner cylinder,
2. The valve opening timing of the exhaust valve of the outer cylinder is made earlier than the valve opening timing of the inner cylinder, and the change rate of the lift amount of the exhaust valve of the inner cylinder of the outer cylinder is reduced. 4. The exhaust system for an engine according to any one of items 1 to 3.

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