JPH0322532Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a catalyst-equipped fuel injection engine that purifies exhaust gas by the action of a catalyst provided in an exhaust passage.

(Prior art) Since automobiles run on roads, the organic components contained in the exhaust gas from their engines have a large impact on the surroundings, and there is a strong need to purify the exhaust gas, and various countermeasures have been taken. There is. The toxic components contained in engine exhaust gas include CO,
There are unburned gases such as HC and NOx, and thermal reactors, catalysts, etc. are often used to remove them.

To give an example, as disclosed in Jitsugyo No. 57-17047, a thermal reactor, a reduction catalyst, and an oxidation catalyst are arranged in the exhaust passage from the upstream side, and a secondary There is an engine exhaust control device that supplies air. With this exhaust control device,
In the thermal reactor, the unburned gas components supplied upstream are combusted, and NOx is mainly converted into CO, HC, etc. by the reduction catalyst.
is removed by reaction with an oxidation catalyst. In addition, since the oxidation catalyst promotes the oxidation reaction when the amount of air becomes larger than the stoichiometric air-fuel ratio, secondary air is supplied to the upstream side of the oxidation catalyst (that is, between the reduction catalyst and the oxidation catalyst).

In this way, by combining a reduction catalyst and an oxidation catalyst, it is possible to remove toxic unburned gas components such as NOx, CO, and HC from exhaust gas, but the reaction of the catalyst does not become active unless the temperature reaches a certain level. Therefore, in general, secondary air is supplied upstream of the thermal reactor to combust unburned gas within the thermal reactor to raise the exhaust gas temperature and thereby raise the catalyst temperature.

Additionally, generally speaking, when the intake air of the engine is at the stoichiometric air-fuel ratio, the toxic unburned gas components in the exhaust are at a minimum. For this reason, it is common practice to install an exhaust gas concentration sensor such as an oxygen sensor in the exhaust passage to detect the amount of oxygen in the exhaust gas, feed this back to the intake system, and control the air-fuel ratio so that it approaches the stoichiometric air-fuel ratio. There is. Note that there are a fuel injection control method and a carburetor method for controlling the amount of fuel supplied in the intake system, but the fuel injection control method is often used because of its ease of control.

In this way, it is common practice to use a catalyst to purify toxic unburned components in exhaust gas, but when a catalyst is used to oxidize, or combust, the unburned components, heat is generated. Because it accompanies
This heat causes the catalyst to reach a high temperature. In this case, the catalyst does not promote the reaction unless the temperature is raised to a predetermined temperature or higher, but there is a problem in that it tends to deteriorate if the temperature is too high. In particular, as the engine speed increases, the amount of exhaust gas increases and the unburned gas components in the exhaust gas also increase, so the catalyst tends to become hot in the high speed range.
The catalyst also deteriorates quickly. For this reason, when the engine speed exceeds a predetermined speed, the feedback control described above is not performed, but rather the amount of fuel is increased so that the exhaust gas contains unburned fuel, and this unburned fuel is used as a refrigerant. By acting as
A method of preventing the temperature of the catalyst from rising is generally adopted.

Specifically, engine load (throttle opening)
The engine load condition determined by
When the engine is in the feedback region A indicated by diagonal lines in the graph of the figure, the fuel injection amount is controlled to keep the air-fuel ratio close to the stoichiometric air-fuel ratio, and secondary air is supplied. feedback stop area)
When in F, the fuel injection amount is increased and 2
Next, the supply of air is restricted to prevent overheating of the catalyst. FIG. 1 is a graph showing the throttle opening on the vertical axis and the engine rotation speed on the horizontal axis. Line P ₁
is a deceleration line set by the throttle opening and engine speed, and indicates the minimum load necessary for constant speed driving on flat ground. i.e. the line
The higher load side of line P ₁ is the normal operating range (including acceleration operation), and the lower load side of line P ₁ is the deceleration range.
Line P ₂ indicates idling rotation N ₁ , and at rotations lower than N ₁ the engine stalls, which is a region that is not used in actual driving. Hereinafter, line _P1 will be referred to as a deceleration line, and line _P2 will be referred to as an idling rotation line.

Feedback region A in which feedback control is performed is within the normal operating region on the higher load side than the deceleration line P ₁ and on the higher rotation side than the idling rotation line P ₂ , and when the engine rotation speed is lower than the predetermined rotation speed N ₂ in the medium speed range. The throttle opening is set in a region where the throttle opening is smaller than the high load predetermined opening _L1 (that is, medium to low load). Furthermore, even if the engine speed is lower than _N2 , at high loads where the throttle opening is greater than _L1 , feedback control is not performed and the amount of fuel is increased. This is because there is a problem that the output torque decreases and sufficient output cannot be obtained, so the fuel injection amount is increased to increase the output torque.

In this way, in the feedback stop region F, the amount of fuel is increased to prevent overheating of the catalyst, and as a result, the amount of fuel consumed per distance traveled by the vehicle (fuel efficiency) naturally increases.

(Purpose of the invention) In view of the above circumstances, it is an object of the present invention to provide a fuel injection engine with a catalyst that can prevent overheating of the catalyst without deteriorating fuel efficiency as much as possible.

(Structure of the invention) The catalytic fuel injection engine of the invention divides the above-mentioned feedback stop area F into a high rotation and low load area (first feedback stop area) B and other areas, as shown in FIG. In region B, port air (air supplied to the upstream side of the three-way catalyst in the exhaust passage arranged in the order of three-way catalyst and oxidation catalyst from upstream) is divided into region C (second feedback stop region). By this structure, the feedback control of the air-fuel ratio is stopped at the same time as the air-fuel ratio is supplied, thereby eliminating the need to unnecessarily enrich the air-fuel ratio, improving fuel efficiency, and achieving the above objective.

That is, as shown in FIG. 5, the catalyst-equipped fuel injection engine according to the present invention includes a three-way catalyst and an oxidation catalyst in the exhaust passage in order from the upstream side, and a three-way catalyst and an oxidation catalyst on the upstream side of the three-way catalyst in the exhaust passage. A port air supply port for supplying secondary air and an exhaust concentration sensor are provided, and a split air supply port for supplying secondary air is provided between the two catalysts, and the air is supplied to the engine by the exhaust concentration sensor depending on the operating state. In a catalytic fuel injection engine that controls the feedback control of the air-fuel ratio of the air-fuel mixture and the supply of secondary air, the engine speed is higher than the idling speed and the engine load is lower than the minimum load required for running at flat ground speed. In a load state larger than the deceleration line, (a) the engine speed is less than or equal to a first predetermined rotation speed _N2 set in a medium speed range, and the engine load is set to a medium load or a low load;
In the area A where the predetermined load _L1 is below, the feedback control is performed so that the air-fuel ratio of the mixture in the combustion chamber is close to the stoichiometric air-fuel ratio, and the secondary air supply from the port air supply port is stopped and the split air is a feedback area in which secondary air is supplied through the supply port, and (b) the engine rotation speed is the first predetermined rotation speed.
A second predetermined rotation speed N ₂ or more and set higher than the first predetermined rotation speed N ₂ A second predetermined rotation speed N ₃ or less and the engine load is set lower than the first predetermined load L ₁ A region B in which the predetermined load L2 is less than or equal to the predetermined load L ₂ is a first feedback stop region in which secondary air is supplied from the port air supply port and at the same time feedback control of the air-fuel ratio is stopped; A and the area C other than the first feedback stop area B are a second area where the air-fuel ratio in the combustion chamber is made smaller than the stoichiometric air-fuel ratio and where the supply of secondary air from the port air supply port and the split air supply port is cut off. The present invention is characterized in that it is equipped with a catalyst temperature rise control device that sets the feedback stop region.

(Function) As shown in the above configuration, in the first feedback stop region B, NOx is reduced due to the low load.
In view of the fact that the generation of 3-way catalyst is small and there is little negative effect on exhaust gas purification even if the three-way catalyst functions as an oxidation catalyst, a configuration is adopted in which port air is supplied to the upstream side of the three-way catalyst and it functions as an oxidation catalyst. This allows the reaction heat to be borne by the two oxidation catalysts, thereby making it possible to prevent catalyst overburning without making the air-fuel ratio unnecessarily rich, thereby improving fuel efficiency. Furthermore, in the first feedback stop region B, the air-fuel ratio feedback control is stopped, so the exhaust concentration sensor outputs a lean signal due to the port air supply, enriching the air-fuel mixture supplied to the engine. It is possible to prevent this from happening.

(Effects of the invention) Therefore, according to the invention, it is possible to improve fuel efficiency in the first feedback stop region B, thereby achieving prevention of overheating of the catalyst without deteriorating fuel efficiency as much as possible. I can do it.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 2 is a graph showing the control details of the fuel injection type engine of the present invention. As shown in the figure, the normal operating region where the load is higher than the deceleration line _P1 and the rotation speed is higher than the idling rotation line _P2 is changed to the feedback region A. , a first feedback stop area B and a second feedback stop area (fuel increase area) C.
Control is performed in three areas:

Feedback region A is the same as the conventional feedback region shown in _FIG .
When the engine load condition is in this region A, the engine speed is lower than the predetermined speed _N2 in the medium speed range, the air-fuel ratio in the combustion chamber is brought close to the stoichiometric air-fuel ratio. Feedback control is performed and secondary air is supplied to the upstream side of the catalyst.

In the first feedback stop region B, the throttle opening is smaller than the medium load predetermined opening L ₂ (that is, the load is low), the engine speed is equal to or higher than the predetermined rotation speed N ₂ in the medium speed range, and This is a region where the rotational speed is _N3 or less, and when the engine load condition is in this region B, the above feedback control is stopped and secondary air is supplied. This secondary air is
As shown in FIG. 3, the exhaust passage 12 is supplied from the port air supply port 19a near the combustion chamber of the engine body 1, so that the secondary air supplied to the exhaust passage 12 enters the combustion chamber. As a result, the air-fuel ratio within the combustion chamber can be made larger than the stoichiometric air-fuel ratio.

The second feedback stop region C is the feedback region A and the first feedback region within the normal operation region.
When the engine load condition is in a region C excluding the feedback stop region B, the air-fuel ratio in the combustion chamber is made smaller than the stoichiometric air-fuel ratio, and the supply of secondary air is cut off.

By controlling as described above, in the feedback region A, toxic components in the exhaust gas can be effectively purified as in the conventional method, and in the second feedback stop region C, the unburned fuel acts as a refrigerant to cool the catalyst. Overheating and deterioration can be prevented, and sufficient output can be obtained during high loads. Furthermore, in the first feedback stop region B, the air-fuel ratio in the combustion chamber becomes large, so that the fuel injected into the combustion chamber can be sufficiently combusted, the exhaust gas can be purified, and the catalytic oxidation The amount of unburned gas that reacts is reduced, and overheating of the catalyst is suppressed. Furthermore, the exhaust gas is cooled by the relatively cold secondary air supplied upstream of the catalyst, making it possible to suppress overheating of the catalyst. Furthermore, since the amount of fuel injected is small, fuel efficiency is also improved. Note that there is a problem that engine output decreases as the air-fuel ratio increases, but in the case of the present invention, the first feedback stop region B is set in a low load region where the influence of engine output decrease is relatively small. Preventing problems.

In addition, this figure (Figure 2) shows the rotation range lower than the idling rotation speed N ₁ divided into an area D above the deceleration line P 1 and an area below the deceleration line P ₁ , but this is explained later. This is because when the engine load condition reaches region D or E, control is performed to increase the fuel injection amount to prevent engine stalling.

FIG. 3 is a schematic diagram showing an example of a fuel injection type engine with a catalyst according to the present invention.

An intake passage 4 is connected to the intake side of the engine body 1, and an exhaust passage 12 is connected to the exhaust side. Inside the intake passage 4, an air flow meter 3, a throttle valve 5, and a fuel injection valve 7 are installed in order from the upstream side.
An air cleaner 2 is connected to the upstream end of the intake passage 4 and has one end 2a communicating with the outside air. Inside the exhaust passage 12, an oxygen sensor 9, an enlarged manifold 11 acting as a thermal reactor, a three-way catalyst 13a, and an oxidation catalyst 13b are arranged in order from the upstream side, and a port air supply port 19a is opened upstream of the oxygen sensor 9. However, a split air supply port 1 is provided between the three-way catalyst 13a and the oxidation catalyst 13b.
8a opens. In addition, the air cleaner 2 includes not only the intake passage 4 but also the intake pipe 15 of the air pump 15.
a also communicates with the discharge pipe 15 of this air pump 15a.
b communicates with the air control valve 16. A relief passage 17, a split air pipe 18 and a port air pipe 19 are attached to the air control valve 16, the relief passage 17 is open to the atmosphere, and the split air pipe 18 and the port air pipe 19 are connected to the split air supply port 18, respectively.
a and the port air supply port 19a.

When the engine configured as described above is operated, the intake amount is adjusted by the throttle 5, and the air sucked in from one end 2a is purified by the air cleaner 2, and the intake amount is detected by the air flow meter 3. Thereafter, it is mixed with the injected fuel from the fuel injection valve 7 and enters the combustion chamber within the engine body 1. After burning in the combustion chamber and providing driving force to the engine, the combustion gas is discharged into the exhaust passage 12. Port air supply port 1 is connected to this exhaust depending on the operating condition.
Port air as secondary air is supplied from 9a, and the oxygen sensor 9 detects the exhaust gas concentration.
This exhaust gas then passes through the enlarged manifold 1 and enters the three-way catalyst 13a to contain CO, HC, and NOx.
After the air is purified, it is mixed with split air as secondary air supplied from the split air supply port 18a depending on the operating condition, and the oxidation catalyst 13b is heated.
Once inside, CO and HC are purified. At this time, the port air and split air are supplied by distributing the air sent to the air control valve 16 by the air pump 15 by the air control valve 16.

During the above operation, the intake air amount detected by the air flow meter 3, the throttle opening detected by the throttle opening sensor 6 placed near the throttle 5, the engine rotation speed detected by the engine rotation sensor 8, and Oxygen sensor 9
The exhaust concentration detected by
It is transmitted to the catalyst temperature rise control device 10 via a, 6a, 8a, and 9a. Catalyst temperature rise control device 1
0, depending on these detected information,
Signals for controlling the fuel injection amount and the supply of secondary air are sent from lines 10a and 10b to the fuel injection valve 7.
and output to the air control valve 16 to control these.

The operation of the catalyst temperature increase control device 10 is illustrated by the flowchart shown in FIG. This control device 10
When operation starts, after initialization, the engine speed, throttle opening, intake air amount, and exhaust concentration (oxygen concentration) at that time are read, and the basic fuel injection amount q is calculated based on these.

(q = K Any zone (area) from A to E
Determine if it is. When it is determined that the air is in the A zone, that is, the feedback region, the exhaust gas concentration detected by the oxygen sensor 9 is fed back to correct the fuel injection amount so as to approach the stoichiometric air-fuel ratio, and then the air control valve 16 is operated. Split air is supplied from the split air supply port 18a upstream of the oxidation catalyst 13b, and the flow returns to the beginning. When it is determined that the engine is in the B zone, that is, the first feedback stop region, fuel injection is performed with the basic fuel injection amount q calculated above, and the air control valve 16 is operated to supply port air from the port air supply port 19a. After feeding, return to the beginning of the flow. When it is determined that the fuel is in the C zone, that is, the second feedback stop region, a coefficient is set to increase the fuel injection amount.
The basic fuel injection amount q is multiplied by K ₁ (>1) to determine the fuel injection amount, and fuel injection is performed accordingly. After cutting off the secondary air supply with the air control valve 16, the flow Go back to the beginning. D
When it is determined that the vehicle is in the zone or E zone, a coefficient K ₂ (>1) or K ₃ (>1) is added to the basic fuel injection amount q to prevent engine stalling.
After injecting fuel with the fuel injection amount obtained by multiplying by , and supplying port air with the air control valve 16, the process returns to the beginning of the flow. When it is determined that the engine load condition is not in any of the above zones A to E, the engine is in the deceleration zone with a lower load than the deceleration line _P1 , so the fuel injection is cut off, the engine brake is activated, and the port air is After supplying, return to the beginning of the flow.

By repeating the above flow, the purpose of the present invention can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the control area of fuel injection and secondary air supply in the conventional engine, Fig. 2 is a graph showing the control area of fuel injection and secondary air supply in the engine of the present invention, and Fig. 3 is a graph showing the control area of the fuel injection and secondary air supply in the engine of the present invention. FIG. 4 is a schematic diagram showing an example of the engine of the invention, FIG. 4 is a flowchart showing control by the catalyst temperature rise control device of the engine of the invention, and FIG. 5 is an overall configuration diagram showing the configuration of the invention. DESCRIPTION OF SYMBOLS 1... Engine body, 2... Air cleaner, 3... Air flow meter, 4... Intake passage, 5... Throttle, 7... Fuel injection valve, 9... Oxygen sensor, 10... Catalyst temperature rise control device, 12... Exhaust passage, 13a...
Three-way catalyst, 13b... Oxidation catalyst, 16... Air control valve, 18a... Split air supply port,
19a...Port air supply port.

Claims (1)

[Claims for Utility Model Registration] A three-way catalyst and an oxidation catalyst are provided in the exhaust passage in order from the upstream side, and a port air supply port and an exhaust concentration sensor that supply secondary air to the upstream side of the three-way catalyst in the exhaust passage. On the other hand, a split air supply port for supplying secondary air is provided between the two catalysts, and the exhaust gas concentration sensor controls the air-fuel ratio of the air-fuel mixture supplied to the engine and the secondary air supply depending on the operating condition. In a catalytic fuel injection engine in which supply is controlled, in a load state where the engine rotation speed is higher than idling rotation and the engine load is higher than the minimum load deceleration line required for constant speed running on flat ground, (a) the engine rotation; a first predetermined rotation speed _N2 or less, which is set for a medium-speed engine, and a first engine whose engine load is set to a medium load or a low load;
In region A where the predetermined load _L1 is below, the feedback control is performed so that the air-fuel ratio of the air-fuel mixture in the combustion chamber is close to the stoichiometric air-fuel ratio, and the secondary air supply from the port air supply port is stopped and the split air is a feedback area in which secondary air is supplied by the supply port, and (b) the engine rotation speed is the first predetermined rotation speed.
A second predetermined rotation speed N ₂ or more and set higher than the first predetermined rotation speed N ₂ A second predetermined rotation speed N ₃ or less and the engine load is set lower than the first predetermined load L ₁ A region B in which the predetermined load L2 is less than or equal to the predetermined load L ₂ is a first feedback stop region in which secondary air is supplied from the port air supply port and at the same time feedback control of the air-fuel ratio is stopped; A and the area C other than the first feedback stop area B are a second area where the air-fuel ratio in the combustion chamber is made smaller than the stoichiometric air-fuel ratio and where the supply of secondary air from the port air supply port and the split air supply port is cut off. What is claimed is: 1. A fuel injection engine with a catalyst, characterized in that the engine is equipped with a catalyst temperature rise control device that controls the temperature of the catalyst in a feedback stop region.