JP2817852B2 - Exhaust control device for engine with catalyst - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust control system for a catalyst-equipped engine, and more particularly, to an increase in exhaust resistance performed to promote exhaust purification performance when the engine is cold. The present invention relates to a technique for preventing deterioration of acceleration response, emission deterioration, knocking, and the like.

(Prior Art) When the engine is cold, the purification performance of the catalyst purification device is reduced because the catalyst purification device is also in a low temperature state. Therefore, in order to quickly return the exhaust gas purification performance at the time of cooling to the normal level, for example, as in Japanese Utility Model Laid-Open No. 60-192248, proposed a technology to increase the exhaust pressure and increase the exhaust pressure only at the time of cooling. Have been. This is because if the exhaust pressure increases, the temperature of the exhaust gas rises due to adiabatic compression, and eventually the temperature of the catalyst also rises, and the purification performance recovers quickly. It is also said that if the exhaust pressure is increased, the residence time of the exhaust gas in the catalyst is prolonged, which also leads to an improvement in purification performance.

Further, as a method for activating the catalyst at the time of cooling, for example, Japanese Patent Application Laid-Open No. S60-222518 discloses a method in which a passage provided with a heating means is provided in the exhaust passage on the upstream side of the catalyst. Here, when the engine is cold, the exhaust gas is guided to a passage provided therewith, and the exhaust gas is heated. Then, the heated exhaust gas activates the catalyst.

(Problems to be Solved by the Invention) When the exhaust pressure is increased by increasing the resistance of the exhaust passage as in Japanese Utility Model Application Laid-Open No. 60-192248, when a high load operation such as full throttle opening is performed, Due to the high exhaust pressure, the dilution gas ratio (DGR) increases and the mixture temperature rises,
Knocking is likely to occur. Further, the acceleration response is also reduced. Further, although the emission is improved by the high exhaust pressure, the deterioration of the catalyst is accelerated due to the high exhaust gas temperature.

Therefore, the present invention has been proposed in order to eliminate the above-mentioned problems, and its object is to make it possible to accelerate the activation of the catalyst to the extent that the catalyst is not degraded during the operation at the time of cold operation, It is an object of the present invention to propose an exhaust control device for a catalyst-equipped engine that ensures operability such as described above.

(Means and Actions for Achieving the Object) A configuration of the present invention for achieving the above object includes, as shown in FIG. 1, a resistance changing unit for changing a passage resistance of an exhaust passage provided with a catalyst on the way. In an engine with
Temperature detecting means for detecting the temperature of the catalyst; state detecting means for detecting a high-load operation state of the engine; and control means for receiving an output signal of these detecting means. When the high load operation state is detected when the engine is cold, the passage resistance is reduced, and when the catalyst temperature is equal to or higher than a predetermined value, the resistance decreases as the temperature increases.
Control means for controlling the resistance changing means.

(Embodiment) With reference to the accompanying drawings, the present invention will be described with a side port method.
An embodiment applied to a 6PI rotary engine and a modification thereof will be described.

<Embodiment> FIG. 2 shows the entire engine control system of this embodiment.

In the figure, reference numeral 10 denotes an engine body. Sucked air while paced its flow rate Q _a by the air flow meter 14, the flow rate is regulated by a throttle valve 19. The opening of the throttle valve 19 is detected by a throttle sensor 28. The intake air is mixed with the fuel injected from the injector 15 and guided into the combustion chamber.

Water temperature T _w of the engine 10 is measured in the temperature sensor (not shown), and sent to the engine controller 40. Whether the engine from the water temperature T _w is in the cold state is determined.

The engine speed N is detected by a speed sensor 29 attached to the output shaft 12. The total amount TE of fuel injected from the injector 15, that is, the injection pulse width TE, Given by Here, k is a constant.

23 is a catalytic converter. Exhaust passage 22 for exhaust gas
Flows through the converter 23 and is guided to the muffler 27. The temperature of the catalytic converter 23 is detected by the temperature sensor 16.
The opening degree φ of the exhaust control valve 24 provided at an intermediate position between the converter 23 and the muffler 27 is freely controlled by the control of the CPU 40 via the actuator 26. In the engine of this embodiment, when the engine coolant temperature _Tw is low, the exhaust valve 24 tends to close (FIG. 4C). That is, when the engine is cold, the valve 24 is closed so that the flow rate of the exhaust gas becomes low, and the exhaust pressure rises. Generally, when the engine water temperature is low, the combustion becomes unstable, and since the temperature of the converter is low, the purification performance is low. Accordingly, at the time of cooling, the exhaust pressure is increased, the exhaust gas temperature is increased by adiabatic compression, and the activation of converter 23 is hastened. When the engine comes out of the cold state, the temperature of the exhaust gas rises and the catalyst is activated, so that the valve 24 is fully opened.

Also, in this engine system, as described later,
Even under cold conditions, the valve 24 does not seem to be closed under predetermined conditions. For example, at high load the exhaust valve 24
Is fully opened (FIG. 4A), and when the temperature of the catalytic converter 23 rises, the valve 24 is opened to an opening corresponding to the temperature.
(Fig. 4B) to lower the exhaust gas temperature.

This rotary engine employs a 6-port intake system. That is, each rotor has three intake ports. In FIG. 2, for convenience of illustration, a secondary main intake port 20b (hereinafter abbreviated as SM port) and a secondary augmented port (SA port) 20a among the three intake ports are illustrated. In practice, the primary port is provided in the side housing on the near side in FIG.

FIG. 3 is a flowchart showing a control procedure of this embodiment.

In step S1, the intake air amount Q _a, engine speed N, the engine coolant temperature T _w, the catalyst temperature T _c is read respectively. Step S2
In the intake air amount Q _a, whether the load TE, calculated on the basis of the engine speed N and the like by determining whether higher or lower than a predetermined threshold, a low-load state or in a high load state judgment I do. If it is determined that the load is high, the
Proceeding to S14, the exhaust valve 24 is fully opened (opening φ = 0) (see FIG. 4A). That is, in this embodiment, regardless of whether the engine is in a cold state or not, when the engine is in a high load state, the exhaust valve 24 is fully opened to lower the exhaust pressure in order to emphasize acceleration response, It lowers the DGR.

 The case where the operation state is not high load will be described.

In this case, check the engine water temperature T _w, cold state (T _w <
t _w ) and whether it is in a warm-up state (T _w ≧ t _w ).
When the engine is warmed up, the exhaust pressure valve 24 is fully opened (see FIG. 4A).

Hereinafter, a description will be given of a case where the operation state is not high load and the engine is in a cold state. In such a case, the opening φ of the exhaust valve is changed according to the catalyst temperature _Tc . That is, if the temperature t ₁ is the temperature at which the catalyst is activated, the catalyst temperature T _c
However, when T _c <t ₁ , that is, when the catalyst has not reached the activation temperature, the exhaust valve 24 tends to close (φ = φ) in order to increase the exhaust gas temperature in order to promote catalyst activation. ₁ ; see Fig. 4C). Thus, by setting the opening degree of the valve 24 to phi _1,
The activation of the catalyst is promoted, and the emission time is improved because the residence time of the exhaust gas in the catalyst is prolonged even when the catalyst is not activated.

The temperature t ₂ and temperature accelerate the degradation of the catalyst. Step S8
The state where the catalyst temperature reaches t ₁ ≦ T _c <t ₂ indicates that the engine is in a cold state, but the catalyst is in an activated state. In this case, go to step S8
It is determined as YES. This activated state is obtained by closing the exhaust valve 24 slightly. However, if the exhaust valve 24 is opened as shown in FIG. 4A, the temperature of the catalyst 23 may decrease again because the engine is still in a cold state. On the other hand, the opening of the valve 24 phi = phi ₁
To keeping continues, the temperature of the catalytic converter 23, there is also a possibility to increase the degradation temperature t ₂ or more. Therefore, step S1
2, the exhaust valve 24 is opened at an intermediate opening (φ = φ ₂ ; FIG. 4B)
The temperature of the exhaust gas is lowered slightly to keep the catalyst at the minimum activation temperature. In addition, since the exhaust pressure slightly decreases, the DGR decreases and the operability improves.

Note that when the catalyst temperature T _c is T _c ≧ t _2, since hasten the deterioration of the catalyst, fully open the exhaust valve 24 at step S14 (FIG. 4A)
To The catalyst is sufficiently heated, even when the valve 24 is fully opened in the cold state of the engine, the catalyst temperature T _c is because never drop below the activation temperature t _1.

According to the control procedure shown in FIG. 3, the effect of preventing knocking is additionally obtained. That is, when a high-load operation is performed with the exhaust valve 24 closed as in the conventional example, the temperature of the air-fuel mixture in the combustion chamber increases due to an increase in the DGR due to the high exhaust pressure, so that knocking easily occurs. . However, the third
In the control procedure shown in the figure, a high load state is detected (step S
2) Since the exhaust pressure is lowered by fully opening the exhaust valve 24, the occurrence of knocking is also suppressed along with securing the acceleration response.

In the control procedure of FIG. 3, the high load state is determined from the fuel injection pulse width TE. However, from the viewpoint of emphasis on acceleration and control for suppressing knocking, instead of the load determination, an acceleration signal, for example, a throttle 19 per unit time is used.
The value of the change in the opening degree (Δθ / Δt) may be used as a judgment material.

Next, a modification of the embodiment shown in FIG. 2 will be described. This modification focuses on the following points. That is, when the resistance of the exhaust passage is increased at the time of cooling, as shown in Japanese Utility Model Application Laid-Open No. 192248/1985, the residence time of the exhaust gas in the catalyst becomes longer and the emission is improved. However, the drivability deteriorates due to the increase in DGR. In addition, an increase in DGR may lead to misfiring, etc., which may worsen emissions. Therefore, in this modification, in order to obtain a balance between the prevention of deterioration of driving performance and the improvement of emission, as an index of the deterioration of driving performance, the angular velocity fluctuation of the output shaft 12 or the finger pressure by the pressure sensor provided on the leading side spark plug is used. Fluctuations are detected, the drivability is suppressed to an acceptable level, and the exhaust pressure is raised as much as possible.

FIG. 5 shows an engine system of the modified example. Second
What is different from the figure is a finger pressure sensor 17 for detecting the combustion chamber pressure P near the spark plug 13b on the leading side. The finger pressure fluctuation is calculated as ΔP / Δt. Further, the variation of the angular velocity is calculated as the variation ΔW / Δt of the cycle of the output pulse of the rotation speed sensor provided on the output shaft.

FIG. 6 is a flowchart of a control procedure according to this modification.

In step S20, the intake air amount Q _a, engine speed N, the engine coolant temperature T _w, the catalyst temperature T _c, acupressure P is respectively loaded. The control of steps S22 and S24 is the same as that of steps S2 and S4 in FIG. Hereinafter, a case where the engine is in a cold state will be described.

In step S26, the angular velocity fluctuation and the acupressure fluctuation are calculated. In step S28, the calculated angular velocity fluctuation and the acupressure fluctuation are Find out if Here, C ₁ and D ₁ are predetermined thresholds. When the angular speed variation and acupressure variation is small, the drivability is good, at step S32, closing the exhaust valve 24 until opening phi = phi ₁ (cf. 4C view). N at step S28
If it is determined to be O, the process proceeds to step S30, where the angular velocity fluctuation and the acupressure fluctuation are Find out if Here, C ₂ (> C ₁ ) and D ₂ (> D ₁ ) are predetermined thresholds. NO at step S28, YE at step S30
When determined to be S, it indicates that drivability is slightly reduced. In this case, the process proceeds to step S34, increasing the exhaust valve opening to phi _2.

If NO is determined in step S28 and NO is determined in step S30, it is determined that drivability has become largely unstable, and the exhaust valve 24 is fully opened (φ = φ ₃ ) in step S36.
To

Thus, according to this variant, regardless of whether the engine is in a cold state or not, when the engine is in a high load state,
Since the exhaust valve 24 is fully opened in step S36, the acceleration response is improved. When the engine is in a cold state, the exhaust valve 24 is closed in step S32 to promote activation of the catalyst and increase the residence time of the exhaust gas to improve emission, unless the operability is deteriorated. To do it. On the other hand, if the drivability is slightly deteriorated, the exhaust valve 24 is slightly opened within a range where the exhaust pressure does not excessively decrease and the emission does not deteriorate. In this way, a balance between improvement of emission and securing of drivability can be achieved.

It should be noted that knocking occurs as an aspect of deterioration in drivability. Therefore, a knocking sensor may be further added to the system of the modified example of FIG. 4, the operability is determined from the sensor output, and the exhaust valve opening may be controlled according to the value.

 The present invention can be variously modified.

For example, in the above-described embodiment and the modified example, the opening degree of the exhaust valve is set to three types, but may be increased if the number is set. Further, in the above-described embodiment and its modified examples, all are examples of the rotary engine, but the present invention is also applicable to a reciprocating engine. This is because the above-described problems in the reciprocating engine when the engine is cold and when the exhaust pressure rises occur in the same manner as the rotary engine.

Further, the present invention is not limited to the fuel injection type engine, and is applicable to, for example, a carburetor type engine.

Further, in the above-described embodiments and the like, the exhaust valve is provided downstream of the catalyst, but the effect of the present invention can be achieved by installing the exhaust valve upstream.

(Effect of the Invention) As described above, according to the exhaust control apparatus for a catalyst-equipped engine of the present invention, the resistance increasing means operates during the cold operation, and the exhaust gas purification performance can be improved at an early stage. Furthermore, if the load becomes high during the cooling operation, the exhaust resistance decreases and the exhaust pressure decreases, so that the DGR decreases and operability, for example, acceleration, is secured. Also, since the temperature of the catalyst is monitored and the exhaust resistance is reduced as the catalyst temperature rises, prevention of catalyst deterioration, early activation of the catalyst,
Improve emission balance.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of the present invention, FIG. 2 is an overall view of one embodiment in which the present invention is applied to a rotary engine, FIG. 3 is a flowchart showing a control procedure of the embodiment in FIG. 4A, 4B, and 4C are diagrams for explaining the open / close state of the exhaust valve according to the embodiment, FIG. 5 is an overall view of an engine system according to a modification, and FIG. 6 is a diagram illustrating a modification of FIG. It is a flowchart of a control procedure. In the figure, 10: rotary engine body, 11: rotor, 12: output shaft, 13, 13a, 13b: spark plug, 15: injector, 16: catalyst temperature sensor, 17: finger pressure sensor, 19 ......
Throttle valve, 20a …… Secondary auxiliary intake port (SA port), 20b …… Secondary main intake port (S
M port), 21 ... intake pipe, 22 ... exhaust manifold, 23
... catalytic converter, 24 ... exhaust control valve, 26 ... actuator, 27 ... muffler, 28 ... throttle opening degree sensor, 29 ... engine speed sensor, 40 ... engine controller.

Claims (1)

(57) [Claims] 1. An engine provided with a resistance changing means for changing a passage resistance of an exhaust passage provided with a catalyst in the middle thereof, a temperature detecting means for detecting a temperature of the catalyst, and a high load operation state of the engine. State detection means, and control means for receiving output signals of these detection means, the path resistance of the exhaust passage increasing when the engine is cold, and the passage when the high load operation state is detected when the engine is cold. Control means for controlling the resistance changing means so as to reduce the resistance and reduce the resistance as the temperature rises when the catalyst temperature reaches the activation temperature. Exhaust control device.