JPH04209925A - Control device for rotary piston engine - Google Patents

Abstract

PURPOSE:To surely prevent overrichness of air-fuel ratio according to deterioration of an air pump by detecting a delivery pressure of the air pump for supplying secondary air, and setting a target idle speed higher the lower decreased the detected delivery pressure is than a target delivery pressure. CONSTITUTION:In an automobile rotary piston engine 1, an opening of a bypass air passage 27 is adjusted through an idle control valve 26 by a control unit 8 to perform idle speed control. Simultaneously, an air control valve 20 is opened in the final period of an exhaust stroke to supply secondary air from an air pump 16 into an exhaust port 14. Here, a pressure sensor 24 is arranged in just the downstream of the air pump 16, in an air passage 17. In the control unit 8, when the air pump 16 is deteriorated to decrease a secondary air amount by dropping a delivery pressure of the air pump a target idle speed of the engine is increased by a predetermined speed corresponding to a degree of deterioration, that is, a degree of dropping the delivery pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control device for a rotary piston engine.

(Prior Art) Conventionally, it has been known that in a rotary piston engine, feedback control is performed to maintain the idle speed at a target speed at all times by increasing or decreasing the amount of bypass air that bypasses a throttle valve disposed in the intake passage. It is being

On the other hand, in rotary piston engines, in order to prevent part of the exhaust gas from being carried into the intake system during idle operation at low rotational speeds and impairing idle stability, two parts of the exhaust system are used during idle operation. Attempts have been made to supply secondary air and replace this secondary air with the exhaust gas to reduce the exhaust gas (so-called illusion gas) brought into the intake system (for example, Japanese Patent Laid-Open No. 1-237321 (see official bulletin). And in this case,
As disclosed in the above-mentioned prior art, secondary air is normally supplied by an air pump directly driven by the engine.

(Problem to be Solved by the Invention) By the way, in this way, in addition to supplying secondary air to the exhaust system, the idle speed of the engine is feedback-controlled.In the rotary piston engine, the secondary air is supplied to the exhaust system. Is the predetermined target idle rotation speed maintained by the intake air amount that is the sum of the secondary air and the regular intake air supplied from the intake system, that is, the primary air? In that case, the fuel supply amount itself is It is set corresponding to the amount of primary air supplied via the air flow meter. For example, if the negative air amount is Ql and the secondary air amount is Q, the intake air amount is (Q, +Q.

), and in that case, the fuel supply amount is the primary air IQ,
Therefore, the air-fuel ratio of the mixture actually taken into the working chamber of the engine (i.e.,
-th air-fuel ratio) is expressed as C(Q, +Q2)/F, ko... (1 equation).

However, generally, an air pump gradually deteriorates during long-term use, and as the deterioration progresses, its discharge pressure decreases, and the amount of discharged air decreases accordingly.

Therefore, if the primary air-fuel ratio is set based on the discharge pressure of the air pump in an undeteriorated state, the primary air-fuel ratio will gradually decrease as the air pump deteriorates and its discharge pressure decreases for reasons described later. The fuel ratio becomes overrich, and as a result, unburned components in the exhaust gas are combusted in the exhaust system, which may cause the catalytic converter disposed in the exhaust passage to overheat and impair its durability.

That is, for example, assuming that the air pump deteriorates and the amount of secondary air supplied thereby decreases by (α) to (Q, -α), even in this case, the same target idle speed as before deterioration will be maintained. In order to do this, it is necessary to compensate for this decrease in secondary air (α) on the negative secondary air side. As a result, the amount of primary air supplied from the intake system is reduced from the initial (
Q, ) to ((Q.

+α). This means that the amount of air passing through the airflow sensor increases by (α), and the amount of fuel corresponding to this increased amount of primary air also changes from the initial amount of fuel (
The amount of fuel is increased from F1) to a larger amount of fuel (F2). As a result, the -order air-fuel ratio is ((Q, -α) + (
Q2+α))/F.

It is expressed as =(Ql+cl/pt...(Equation 2)).

Here, when comparing (Equation 1) and (Equation 2) above, (
F, <F2), when the air pump deteriorates, the primary air-fuel ratio becomes overrich compared to before the deterioration.

Therefore, from the viewpoint of improving the durability of the catalytic converter, it is necessary to prevent the primary air-fuel ratio from becoming overrich due to such deterioration of the air pump as much as possible.

However, the reality is that no effective proposals have been made to address these problems at present.

Therefore, in the present invention, in a rotary piston engine that performs feedback control of the idle rotation speed and also supplies secondary air to the exhaust system by an engine-driven air pump, the primary air-fuel ratio This was done in an effort to provide a control device that can prevent enrichment and improve the durability of the catalytic converter.

(Technical Background of the Invention) In the process of examining means for solving the problem, the inventors of the present application focused on the characteristics of air pumps. In other words, in general, an air pump's discharge pressure gradually decreases due to aging (in other words, the pump efficiency decreases), but on the other hand, this decrease in pump efficiency can be caused by increasing the rotation speed. It has the characteristic that it can be easily recovered. For this reason, the inventor of the present application took into account that the air pump is driven by an engine, and in order to prevent the pump efficiency from decreasing due to deterioration, the inventor of the present application determined that the engine speed should be adjusted according to the degree of deterioration. I came up with the idea that it would be better to raise the level.

(Means for Solving the Problems) Based on this idea, the present invention provides specific means for solving the above problems by performing foot-hazoku control to maintain the idle speed of the engine at the target speed, and A rotary piston engine control device that supplies secondary air to an exhaust system of a rotary piston engine by an air pump driven by the engine,
Discharge pressure detection means for detecting the discharge pressure of the air pump;
and control means for setting the target idle rotation speed higher as the detected discharge pressure detected by the discharge pressure detection means is lower than a target discharge pressure preset in accordance with the operating state of the engine. It is characterized by

(Function) Since the present invention has such a configuration, when the air pump deteriorates and its discharge pressure decreases and the amount of secondary air decreases, the system will respond to the degree of deterioration, that is, the decrease/degree of discharge pressure. The target idle speed of the engine is then increased by a predetermined number of rotations compared to that before the deterioration, and the discharge pressure is restored to the state before the deterioration. Therefore, regardless of the deterioration of the air pump, the amount of air supplied from the intake system remains the same as before deterioration.

(Effects of the Invention) Therefore, according to the control device for a rotary piston engine of the present invention, even if the air pump deteriorates, the pump efficiency of the air pump can be improved by increasing the target idle speed of the engine higher than that before the deterioration. Since this is maintained, over-richness of the air-fuel ratio due to deterioration of the air pump is reliably prevented, and as a result, the effect of eliminating overheating of the catalytic converter and improving its durability can be obtained.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a control device according to an embodiment of the present invention.
This rotary piston engine 1 for automobiles and its suction
The exhaust system is shown, and in the figure, reference numeral 2 indicates an intake passage connected to an intake port 13 opened in the side housing 10, and numeral 3 indicates an exhaust passage connected to an exhaust port 14 opened in the rotor housing 9. It is. The intake passage 2 is provided with an air cleaner 4 and an air flow sensor 5 on its upstream side, and a throttle valve 6 and an injector 7 on their downstream side. Further, a bypass air passage 27 is formed on the side of the throttle valve 6 so as to bypass the throttle valve 6, and an idle control valve 26 for controlling the amount of bypass air is interposed in the bypass air passage 27. There is. Further, the opening degree of the throttle valve 6 is determined by a throttle opening sensor 21.
At the same time, the temperature of the engine 1 is detected by a water temperature sensor 22 disposed on the intake passage 2 side.

The exhaust passage 3 is provided with a 0.0 mm air-fuel ratio sensor for detecting the air-fuel ratio. A sensor 23 and a catalytic converter I5 for purifying exhaust gas are provided.

On the other hand, an air passage 17 is branched from the intake passage 2 between the air cleaner 4 and the air flow sensor 5, and an air pump 16 driven by the engine 1 is arranged in this air passage I7. Further, a pressure sensor 24 is disposed immediately downstream of the air pump 16, and the air passage I7 is connected to a first air branch passage 18 equipped with a check valve 28 further downstream from the pressure sensor 24. The air is branched into a second air branch passage 19 equipped with a valve 29 . Of the first air branch passage 18 and the second air branch passage 19, the first air branch passage 18 has its downstream end connected to the exhaust boat 14 of the engine l.
It is partially opened. The first air branch I8 is opened and closed by an air control valve 20 whose operation is controlled by a three-way solenoid valve 30, and in particular, in this embodiment, it is opened only in the idle operating range of the engine. Its operating characteristics are set. On the other hand, the second air branch passage 19 opens its downstream end into the catalytic converter t5.

In addition, in FIG. 1, reference numeral 8 is a control unit;
21 is a throttle opening sensor, and 25 is a rotation speed sensor.

The engine 1 configured in this manner performs feedback control of the idle speed and rotation under normal operating conditions based on control signals output from the control unit 8 based on each engine condition factor detected by the sensor. A number feedback control is performed respectively. That is, in the non-idling operating range, the engine speed is controlled in accordance with the driver's request by setting the fuel injection amount according to the intake air amount or the air-fuel ratio.

On the other hand, in the idle operating range, the idle control valve 26 is operated to increase or decrease the opening degree of the bypass air passage 27,
By adjusting the amount of bypass air, idle speed control is performed to maintain the engine speed at a preset target idle speed. In this case, simultaneously with this idle rotation speed control, the air control valve 20 is opened at the end of the exhaust stroke to supply secondary air into the exhaust port 14. This supply of secondary air is carried out by replacing the exhaust scum in the exhaust stroke working chamber with the secondary work Y at the end of the exhaust stroke, and from the exhaust stroke working chamber side to the intake stroke working chamber 7 (1:
The air pump 16 that supplies this secondary air is designed to reduce the amount of exhaust gas carried into the air pump 1 as much as possible, thereby improving idle stability or height.
If the discharge pressure decreases due to age-related deterioration (that is, the pump efficiency decreases), the amount of primary air supplied from the intake passage 2 side through the air flow processor 5 increases by the amount of this decrease in secondary air. As a result, the amount of fuel set corresponding to the amount of primary air increases, and the primary air-fuel ratio becomes overrich.
As mentioned above, there is a risk that the product may overheat and its durability may be impaired.

In order to prevent the primary air-fuel ratio from becoming overrich due to the deterioration of the air pump I6, the present invention is applied in this embodiment. In order to restore the pump efficiency of the air pump 16, the target idle speed of the engine is changed to a higher speed than that before the deterioration. The specific controls in this case are as follows:
This will be explained with reference to FIGS. 2 and 3.

First, in the control, as shown in Fig. 3, the engine load condition, which is a factor for changing the target idle rotation speed, and the discharge pressure before deterioration [Po
(n)), the criterion discharge pressure (Bo(n)E) that serves as the criterion for determining its deterioration, and the target idle rotation speed [No(n)) corresponding to each engine load condition. .

Here, engine load conditions include no-load operation, cooler load applied (abbreviated as COL), electric fan load (abbreviated as EL), and power steering load applied. (abbreviated as PST)
It is assumed that a combination of these loads is applied.

The discharge pressure of the air pump 16 before deterioration (po(n)
) is the one in which the discharge pressure of the air pump 16 in the state before deterioration is set in advance for each target engine speed since the target idle speed [No(n)] of the engine differs depending on the load condition.

In addition, the deterioration determination discharge pressure of the air pump 16 [BO(n)]
The discharge pressure is set in advance based on experimental results and the like when there is a concern that the catalytic converter 15 will overheat if the flow rate of the air pump 16 is reduced further.

If the discharge pressure of the air pump 16 falls further below the deterioration judgment discharge pressure under a certain load condition, it is determined that deterioration has occurred, and the engine speed is increased until the air pump discharge pressure reaches the discharge pressure before deterioration. , the rotational speed at that time is set as the target idle rotational speed. That is, when the air pump 16 deteriorates, the rotational speed of the air pump 16 itself is increased to achieve the same discharge pressure as before the deterioration, thereby recovering the pumping efficiency of the air pump 16.

The specific control in this case will be explained according to the flowchart in Fig. 2. After starting the control, first, it is determined whether the current engine water temperature is above a predetermined temperature (for example, 70°C) (Step Sl), and if it is below this In some cases, in consideration of the stability and quality of the idle rotation, feedback control of the idle rotation speed is not performed, but normal feedback control of the rotation speed is performed (steer knob 513).

On the other hand, if Ennon>A i or above the predetermined temperature, it is determined whether the current operating state is in the idle zone (Step S2), and if it is not in the idle zone, normal rotation speed control is performed ( In step 513), if it is within the idle zone, the process shifts to feedback control of the idle rotation speed. However, even if the operating state is within the idle zone, there are cases where the idle operation is not actually being performed, so in step S3, in order to confirm this and move on to actual idle control, the target rotation speed and the current , and only if the deviation is within a predetermined value, the next idle control is performed.

As a result of the determination in step S3, if the idle state is confirmed (1), then the current engine load condition is determined (
Step S4) and the current air pump discharge pressure P. (Step S5), and furthermore, in order to determine the deterioration of the air pump, the set value (Pon) of the f-core air pump discharge pressure and the detected discharge pressure P are determined in accordance with the above-mentioned load conditions. A comparison is made with (step 56-). Then, set discharge pressure (P
on) and the detected discharge pressure (po) (P on P
o) and the determined discharge pressure (B, n) are compared (step S7).

As a result of the determination in step S7, (P on P o)
< (B on), the air pump 16 has not deteriorated, and therefore the secondary air supply amount by the air pump 16 is maintained at the initially set state, and over-riching of the primary air-fuel ratio does not occur ( That is, the catalytic converter 15
(There is no risk of overheating of the
on po)≧B.

If it is determined as n, the air pump 16 has deteriorated and the initially set amount of secondary air cannot be obtained. Therefore, if the feedback control of the idle speed is continued, the primary air-fuel ratio will not be the same. It is determined that there is a concern about overheating of the catalytic converter 15 due to over-riching, and in this case, the engine speed is set to increase by a predetermined amount (step S8), and the air pump discharge pressure P is increased again. is read (step S9).

And the set discharge pressure P. n and detected discharge pressure P. In step 510, this rotational speed increase control is continued until the rotation speed is reached.
), at the time when both match (that is, when the pump efficiency of the air pump 16 has completely recovered), the rotation speed at that time is set as the target idle rotation speed (Step 511), and then this newly set target idle rotation speed is set. Feedback control of the idle rotation speed is performed according to the number (step 512).

In this way, when the air pump 16 deteriorates, the rotational speed, that is, the engine rotational speed, is changed and set to the increasing side to recover the pump efficiency of the air pump 16, so that the air pump 16 can be constantly operated despite the deterioration of the air pump 16. It becomes possible to supply secondary air as initially set, and as a result, overheating of the catalytic converter 15 caused by over-riching of the secondary air-fuel ratio is reliably prevented, and its durability can be improved.

In this embodiment, the range of increase in engine speed is set by the air pump discharge pressure, but in other embodiments of the present invention, for example, this can be set by adjusting the amount of intake air passing through the air flow sensor 5 by the air pump. It can also be set by changing the amount of increase due to deterioration.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a rotary piston engine equipped with a control device according to an embodiment of the present invention, FIG. 2 is a control flowchart thereof, and FIG. 3 is a control map thereof. 1... Engine 2... Intake passage 3... Exhaust passage 5... Air flow sensor 6... Throttle valve 7... Injector l5... Catalytic converter 16... Air pump 17... Air passage 20.・Air control valve 24...Pressure sensor

Claims (1)

[Claims] 1. A control device for a rotary piston engine that performs feedback control to maintain the idle speed of the engine at a target speed, and also supplies secondary air to the exhaust system of the engine by an air pump driven by the engine. and a discharge pressure detection means for detecting the discharge pressure of the air pump, and a discharge pressure detected by the discharge pressure detection means is lower than a target discharge pressure preset in accordance with the operating state of the engine. 1. A control device for a rotary piston engine, comprising: control means for setting a higher target idle rotation speed.