JP2010084529A - Exhaust emission control device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly make negative pressure wave in exhaust pulsation reach an exhaust port during a valve opening overlap period. <P>SOLUTION: This exhaust emission control device for an engine performs control so that during the valve opening overlap period of an intake valve 4 with an exhaust valve 5 in the same cylinder, the negative pressure wave in the exhaust pulsation is made to reach the exhaust port 3 opened/closed with the exhaust valve 5. The exhaust emission control device includes an exhaust valve opening timing changing means 13 changing the valve opening timing of the exhaust valve 5 and an exhaust gas temperature detection means S2. A controller U controls the exhaust valve opening timing changing means 13 so that the negative pressure wave is made to reach the exhaust port 3 during the valve opening overlap period according to exhaust gas temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an engine exhaust control device.

In an engine, in order to improve exhaust efficiency and volume efficiency, that is, torque, it is common to set a valve opening overlap period in which both an intake valve and an exhaust valve are opened. On the other hand, although exhaust pulsation acts on the exhaust port opened and closed by the exhaust valve, the exhaust efficiency is improved at the timing when the negative pressure wave of the exhaust pulsation reaches the overlap period. In Patent Document 1, this overlap period is increased at the timing when the negative pressure wave of the exhaust pulsation reaches the exhaust port during the overlap period, and conversely, the timing when the positive pressure wave reaches the exhaust port during the overlap period. Discloses that the overlap period is reduced. Further, Patent Document 2 discloses that the phase of the overlap period can be changed, and the timing at which the negative pressure wave reaches the exhaust port during the overlap period is disclosed. Patent Document 3 discloses variable valve means for changing the lift amount and valve opening angle of an intake valve.
JP-A-11-022499 Japanese Patent No. 3678861 JP 2006-348774 A

  By the way, if the negative pressure wave of the exhaust pulsation is set to reach the exhaust port opened and closed by the exhaust valve during the valve opening overlap period when both the intake valve and the exhaust valve are opened, the engine warm-up state In other words, if the exhaust temperature is significantly different, not only does the negative pressure wave reach the exhaust port during the valve opening overlap period, but conversely, the positive pressure wave reaches the exhaust port, resulting in a significant reduction in torque. There was found. That is, the transmission speed of the exhaust pulsation in the exhaust passage becomes the speed of sound, while the speed of sound (that is, the frequency of the exhaust pulsation) changes according to the temperature, while the exhaust temperature is, for example, 200 to 300 degrees C when cold. On the other hand, when the temperature is warm, the temperature is 800 to 900 degrees C. Due to the large difference in the exhaust temperature, the negative pressure wave cannot reach the exhaust port during the valve opening overlap period.

  The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to control the exhaust of an engine that can reliably reach the exhaust port during the valve opening overlap period. To provide an apparatus.

In order to achieve the above object, the following solution is adopted in the present invention. That is, as described in claim 1 in the claims,
An exhaust control device for an engine for controlling a negative pressure wave due to exhaust pulsation to reach an exhaust port where the exhaust valve opens and closes during a valve opening overlap period of the intake valve and the exhaust valve in the same cylinder,
An opening timing change means for the exhaust valve for changing the opening timing of the exhaust valve;
Exhaust temperature detecting means for detecting the exhaust temperature of the engine;
Control means for controlling the exhaust valve opening timing changing means so that the negative pressure wave reaches the exhaust port during the overlap period in accordance with the exhaust temperature detected by the exhaust temperature detecting means;
It is supposed to be equipped with.

  According to the above solution, the exhaust valve pulsation phase itself is changed by changing the exhaust valve opening timing (opening start timing), that is, the timing (phase) at which the negative pressure wave reaches the exhaust port. It becomes possible to change. Then, by changing the valve opening timing of the exhaust valve according to the exhaust temperature, the negative pressure wave can be surely reached the exhaust port during the overlap period, and the torque can be improved.

A preferred mode based on the above solution is as described in claim 2 and the following claims. That is,
The control means delays the opening timing of the exhaust valve as the exhaust temperature rises (corresponding to claim 2). In this case, when focusing on the negative pressure wave of a certain order component, the negative pressure wave is phase-shifted in the advance direction with respect to the crank angle as the exhaust gas temperature rises. By doing so, negative pressure waves of the same order reach the exhaust port during the overlap period, which is preferable in eliminating or suppressing a torque step.

  The control means is configured to advance the opening timing of the exhaust valve when the exhaust temperature is cold compared to when the exhaust temperature is high (corresponding to claim 3). In this case, an effect similar to the effect corresponding to claim 2 can be obtained.

  When the negative pressure wave having a smaller order component reaches the exhaust port during the overlap period within the change range of the exhaust valve opening timing, the control means sets the opening timing of the exhaust valve. The negative pressure wave having a smaller order component is made to reach the overlap period with a large delay (corresponding to claim 4). In this case, the negative pressure wave of the exhaust pulsation has a plurality of order components such as first order, second order, third order, etc. in the order of arrival at the exhaust port, while the negative pressure wave having a smaller order component has a larger amplitude. As the negative pressure wave having a small component reaches the exhaust port during the overlap period, the exhaust gas suction effect becomes higher. Therefore, when a negative pressure wave having a smaller order component can reach the exhaust port during the overlap period within the range of change in the opening timing of the exhaust valve, the negative pressure wave having a smaller order component is used. The torque can be improved more sufficiently by obtaining the exhaust gas suction effect.

The exhaust valve opening timing changing means is a phase change type, and is set so that the closing timing of the exhaust valve is also changed according to the change of the opening timing of the exhaust valve,
An intake valve opening timing changing means for changing the opening timing of the intake valve is provided;
The control means changes the intake valve opening timing when the exhaust valve closing timing is changed by changing the exhaust valve opening timing by the exhaust valve opening timing changing means. To change the intake valve opening timing in the same direction as the exhaust valve opening timing change direction,
(Corresponding to claim 5). In this case, it is preferable to ensure a sufficient overlap period regardless of the opening timing of the exhaust valve, and to sufficiently exhibit the exhaust gas suction effect using the negative pressure wave.

  The exhaust valve opening timing changing means is set to change the opening timing of the exhaust valve while keeping the closing timing of the exhaust valve unchanged or substantially unchanged (corresponding to claim 6). ). In this case, it is preferable to always keep the overlap period at a predetermined size without changing the opening timing of the intake valve.

  According to the present invention, torque improvement utilizing a negative pressure wave can be obtained regardless of changes in exhaust gas temperature.

  In FIG. 1, an engine E is an in-line four-cylinder spark ignition engine for automobiles in the embodiment. Each cylinder 1 </ b> A to 1 </ b> D of the engine E has two intake ports 2 and two exhaust ports 3. As shown in FIG. 2, the intake port 2 is opened and closed by an intake valve 4, and the exhaust port 3 is opened and closed by an exhaust valve 5. Each cylinder 1A to 1D is provided with a fuel injection valve 6 and a spark plug 7. The fuel injection valve 6 is a direct injection type that directly injects fuel into the combustion chamber, but may be a port injection type that injects fuel into the intake port 2.

  In FIG. 2, 8 is a cylinder block, 9 is a cylinder head, 10 is a piston, 11 is an intake valve camshaft that drives the intake valve 4 to open and close, and 12 is an exhaust valve camshaft that drives the exhaust valve 5 to open and close. The exhaust valve camshaft 12 is provided with a variable valve mechanism 13 as means for changing the opening timing of the exhaust valve 5. Of course, each of the camshafts 11 and 12 is interlocked with a crankshaft (not shown) connected to the piston 10.

  Each intake port 2 is connected to a surge tank 22 via a branch intake passage 21. A common intake passage 23 is connected to the surge tank 22, and an air cleaner 24 and a throttle valve 25 are disposed in the common intake passage 23 sequentially from the upstream side to the downstream side.

  Each exhaust port 3 is connected to a branch exhaust passage 31. The branch exhaust passages 31 for the respective cylinders are gathered at the gathering portion 32 and are finally connected to one common exhaust passage 33. The common exhaust passage 33 is provided with a three-way catalyst 34 as an exhaust gas purification catalyst.

  Here, the collecting portion 32 becomes an inverting portion where the pressure wave (positive pressure wave) of the exhaust gas discharged from each exhaust port 3 is reversed, and the exhaust passage length from the collecting portion 32 to each exhaust port 3 is Equivalent exhaust pipe length for exhaust pulsation. That is, the pressure wave (positive pressure wave, negative pressure wave) of the exhaust pulsation reciprocates between each exhaust port 3 and the collecting portion 32 at the speed of sound.

  As shown in FIG. 2, the variable valve mechanism 13 is controlled as described below by a controller (control unit) U configured using a microcomputer. Further, the controller U receives a signal from the rotation speed sensor S1 that detects the engine rotation speed and a signal from the temperature sensor S2 that detects the exhaust gas temperature disposed in the common exhaust passage 33.

  FIG. 3 shows the valve opening timing of the intake valve 4 and the valve opening timing of the exhaust valve 5. The valve opening timing of the intake valve 4 is fixed, and is opened to the front side (advanced side) from the intake top dead center, and is closed to the rear side (retarded side) from the intake bottom dead center. On the other hand, the valve closing timing of the exhaust valve 5 is fixed by the variable valve mechanism 13 (in the embodiment, it is slightly later than the intake top dead center as in the general setting). Is variable.

  The opening timing of the exhaust valve 5 shown in FIG. 3 is for warm use (when the exhaust temperature is high, for example, 800 ° C.), and the intake valve 4 and the exhaust valve 5 are over opened. The negative pressure wave of the exhaust pulsation reaches the exhaust port 3 during the lap period. On the other hand, FIG. 4 is for cold use (when the exhaust temperature is at a low temperature of, for example, 300 ° C.), and the valve opening timing of the exhaust valve 5 remains the same as in FIG. The timing at which the positive pressure wave of the exhaust pulsation reaches the exhaust port 3 will be reached, and the torque will decrease if this condition is maintained.

  In the present invention, when cold, as shown in FIG. 5, the valve opening timing of the exhaust valve 5 is advanced, and the timing of the negative pressure wave of the exhaust pulsation is advanced as compared to the case of FIG. It is. As a result, the timing at which the negative pressure wave reaches the exhaust port 3 (phase with respect to the crank angle) is advanced, and the timing at which the negative pressure wave reaches the exhaust port 3 during the overlap period is achieved, thereby improving the torque. 3 to 5, the primary negative pressure wave is indicated by symbol α1, the secondary negative pressure wave is indicated by symbol α2, and the third negative pressure wave is indicated by symbol α3 (a numerical value after α). Indicates the order, and the third-order negative pressure wave α3 is not shown in FIGS. 4 and 5). Then, the negative pressure wave having a smaller order has a larger amplitude, and the exhaust gas suction effect is higher.

  In a range where the opening time of the exhaust valve 5 is changed, a negative pressure wave having a lower order (lower) may be able to reach the overlap period. That is, for example, even when the third negative pressure wave reaches the exhaust port 3 during the overlap period, the second negative pressure wave is changed during the overlap period by changing the valve opening timing of the exhaust valve 5. If it is possible to reach the exhaust gas, the opening timing of the exhaust valve 5 is changed so that a negative pressure wave having a lower order reaches the exhaust port 3 during the overlap period. FIG. 6 shows a setting example of the valve opening timing of the exhaust valve 5 for causing a negative pressure wave of a lower order to reach the exhaust port 3 during the overlap period. In FIG. 6, the solid line indicates the warm time, and the broken line indicates the cold time. As the engine speed increases, the valve opening timing of the exhaust valve 5 is gradually advanced. However, when the engine is cold, it is more advanced than when it is warm. When the opening timing of the exhaust valve 5 is retarded at a time both in warm and cold conditions, the processing is for causing a negative pressure wave having a smaller order to reach the exhaust port 3 during the overlap period.

  The opening timing of the exhaust valve 5 as shown in FIG. 6 is stored in the controller U in advance in association with the engine speed and the exhaust temperature. Of course, the opening timing of the exhaust valve 5 when the exhaust temperature is not shown in FIG. 6 is set to a plurality (for example, five stages), and the exhaust valve 5 is opened corresponding to the exhaust temperature other than the set exhaust temperature. The time is obtained by interpolation. While the transmission speed of the exhaust pulsation is a constant speed called sound speed, the timing at which the overlap period occurs is changed according to the engine speed, so the opening timing of the exhaust valve 5 is determined using the engine speed as a parameter. I am going to change it.

  FIG. 7 shows a second embodiment of the present invention. In the present embodiment, the exhaust gas discharge order (that is, the ignition order) is, for example, the first cylinder 1A, the third cylinder 1C, the fourth cylinder 1D, and the second cylinder 1B. Then, a collective exhaust passage 41 is formed in which the first cylinder 1A and the fourth cylinder 1D, which are cylinders in which the exhaust gas discharge order (that is, the ignition order) is not adjacent to each other, are configured, and the second cylinders 1B and 3 A collective exhaust passage 42 once assembled with the cylinder 3C is configured. The collective exhaust passages 41 and 42 are gathered at the gathering portion 43, and the downstream side of the gathering portion 43 is configured as one common exhaust passage 44.

  The collective exhaust passages 41 and 42 communicate with each other on the upstream side of the collective portion 43 through a communication port 45, and the communication port 45 is opened and closed by a switching valve 46. Thereby, when the switching valve 46 is closed (when the communication port 45 is shut off), the exhaust pulsation is reversed by the collecting portion 43 and returned to the exhaust port 3. On the other hand, when the switching valve 46 is opened, the communication port 45 becomes an inversion portion of the exhaust pulsation, and the equivalent exhaust pipe length in which the exhaust pulsation is reciprocated is substantially short. Thus, the equivalent exhaust pipe length is changed according to the opening and closing of the switching valve 46, and the timing at which the negative pressure wave reaches the exhaust port 3 during the overlap period can be changed. Note that the position of the communication port 4 is selected so that the timing at which the negative pressure wave of the exhaust pulsation is generated at the exhaust port 3 does not coincide between when the switching valve 46 is opened and when the switching valve 46 is closed.

  In the present embodiment, even when the opening timing of the exhaust valve 5 is changed, even when the timing at which the negative pressure wave reaches the exhaust port 3 cannot be obtained during the overlap period, the overlap is utilized by using the opening and closing of the switching valve 46. The negative pressure wave can surely reach the exhaust port 3 during the period. Even if the negative pressure wave can reach the exhaust port 3 during the overlap period only by changing the valve opening timing of the exhaust valve 5, the switching valve 46 can be used to open and close a larger amplitude (order). It is also possible to cause a negative pressure wave to reach the exhaust port 3 during the overlap period. Of course, the opening / closing control of the switching valve 46 is performed by the controller U.

  FIG. 8 shows a third embodiment of the present invention, in which a variable phase mechanism is used as the variable valve mechanism 13. That is, the valve opening period of the exhaust valve 5 is entirely offset (phase change). In the present embodiment, the exhaust valve 5 can be advanced until the overlap period becomes zero. In the present embodiment, if the timing at which the negative pressure wave reaches the exhaust port 3 cannot be obtained in the overlap period even if the valve opening timing of the exhaust valve 5 is changed, the overlap period is reduced (including 0). It is possible to prevent or suppress the situation where exhaust gas exhaust efficiency is deteriorated by the positive pressure wave of exhaust pulsation.

  In the embodiment of FIG. 8, a variable valve mechanism for the intake valve that changes the opening timing of the intake valve 4 is separately provided so that at least the opening timing of the intake valve 5 can be changed. The valve opening timing of the intake valve 4 is changed in the same direction as the change direction (particularly in the advance direction). Thereby, it is possible to always ensure an overlap period of a predetermined size (period) (the center position of the overlap period is phase-shifted with respect to the crank angle). Note that the change in the opening timing of the intake valve 4 shown in FIG. 8 is a phase change type in which the phase is changed as a whole, but only the opening timing is changed while keeping the closing timing constant or substantially constant. It may be of a form.

  Although the embodiment has been described above, the present invention is not limited to the embodiment, and can be appropriately changed within the scope described in the scope of claims. For example, the invention includes the following cases. . The engine E may be another multi-cylinder engine such as 3 cylinders or 6 cylinders. Moreover, it is not limited to a spark ignition engine represented by a gasoline engine, but may be a compression ignition engine represented by a diesel engine. As the variable valve mechanism for the exhaust valve or the intake valve, an appropriate one can be selected. For example, the exhaust valve 5 (the same applies to the intake valve 4) is driven directly or indirectly by an actuator, This can be performed by controlling the actuator (the actuator constitutes a variable valve mechanism). Of course, the object of the present invention is not limited to what is explicitly stated, but also implicitly includes providing what is substantially preferred or expressed as an advantage.

The simplified top view which shows one Embodiment of this invention and shows the whole system | strain of an engine. The simplified side sectional view of the engine shown in FIG. The figure which shows the relationship between an overlap period and exhaust pulsation at the time of warm. The figure which shows the relationship between the overlap period and exhaust pulsation in the state which made the valve opening timing of the exhaust valve the same as the case of FIG. 3 at the time of cold. The figure which shows the relationship between an overlap period and exhaust pulsation when the valve opening timing of an exhaust valve is advanced at the time of cold. The figure which shows the example of a setting of the valve opening time of an exhaust valve. The principal part simple plane sectional view which shows the 2nd Embodiment of this invention. The figure which shows the 3rd Embodiment of this invention, and respond | corresponds to FIG.

Explanation of symbols

U: Controller S1: Speed sensor S2: Temperature sensor E: Engines 1A to 1D: Cylinder 2: Intake port 3: Exhaust port 4: Intake valve 5: Exhaust valve 13: Variable valve mechanism 32: Collecting portion

Claims (6)

An exhaust control device for an engine for controlling a negative pressure wave due to exhaust pulsation to reach an exhaust port where the exhaust valve opens and closes during a valve opening overlap period of the intake valve and the exhaust valve in the same cylinder,
An opening timing change means for the exhaust valve for changing the opening timing of the exhaust valve;
Exhaust temperature detecting means for detecting the exhaust temperature of the engine;
Control means for controlling the exhaust valve opening timing changing means so that the negative pressure wave reaches the exhaust port during the overlap period in accordance with the exhaust temperature detected by the exhaust temperature detecting means;
An exhaust control device for an engine, comprising: In claim 1,
The engine exhaust control apparatus according to claim 1, wherein the control means retards the valve opening timing of the exhaust valve as the exhaust temperature rises. In claim 1 or claim 2,
An exhaust control apparatus for an engine, characterized in that the control means advances the opening timing of the exhaust valve when the exhaust temperature is cold and when the exhaust temperature is cold compared to when the exhaust temperature is high. In claim 3,
When the negative pressure wave having a smaller order component reaches the exhaust port during the overlap period within the change range of the exhaust valve opening timing, the control means sets the opening timing of the exhaust valve. An exhaust control apparatus for an engine, characterized in that the negative pressure wave having a smaller order component is made to reach the overlap period by being largely retarded. In claim 1,
The exhaust valve opening timing changing means is a phase change type, and is set so that the closing timing of the exhaust valve is also changed according to the change of the opening timing of the exhaust valve,
An intake valve opening timing changing means for changing the opening timing of the intake valve is provided;
The control means changes the intake valve opening timing when the exhaust valve closing timing is changed by changing the exhaust valve opening timing by the exhaust valve opening timing changing means. To change the intake valve opening timing in the same direction as the exhaust valve opening timing change direction,
An exhaust control device for an engine. In claim 1,
The exhaust valve opening timing changing means is set so as to change the opening timing of the exhaust valve while keeping the closing timing of the exhaust valve unchanged or substantially unchanged. apparatus.

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