JPH0235865B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention includes a secondary air passage that guides a part of air pressurized by a supercharger to an exhaust passage, and also provides fuel injection in accordance with the amount of intake air. The present invention relates to a supercharged engine that controls the amount of fuel injected from the device.

(Prior art) Conventionally, a turbocharger has been used to improve engine output, and a portion of the air pressurized by the turbocharger has been used as secondary air for exhaust purification. A supercharged engine provided with a secondary air passage is known. In particular, this type of engine is equipped with an electronically controlled fuel injection device, for example, as shown in Japanese Patent Publication No. 59-5781, a supercharging passage equipped with a supercharger is branched from the main intake passage.
A first air amount detection device is provided upstream thereof, and a second air amount detection device is provided in a secondary air passage whose one end is connected to the supercharging passage and the other end is connected to the exhaust passage. The amount of intake air supplied to the combustion chamber is determined by subtracting the secondary air flow rate detected by the second air amount detection device from the total amount of intake air detected by the device, and fuel injection is performed accordingly. There are some that control the amount.

By the way, in general, this type of engine requires a large amount of secondary air or not so much depending on the operating condition, so a flow rate control device operated by a diaphragm device or the like is installed in the secondary air passage. A valve is provided to open and close the secondary air passage depending on the operating condition, or to change the flow rate of the secondary air depending on the operating condition. Further, the supercharger provided in the supercharging passage usually uses a positive displacement air pump driven by the engine. When controlling the fuel injection amount as described above in such a structure, when the supply of secondary air is stopped or the flow rate of secondary air is low, the influence of pulsations in the discharge pressure of the supercharger etc. Since errors tend to occur in the detected value of the secondary air amount,
Substantially, the detection of the secondary air amount by the second air amount detection device is stopped, and a predetermined value (for example, zero when the secondary air is cut) is set to 2 instead of the detected value.
The fuel injection amount can be controlled with higher precision by setting the air amount to the following air amount. However, if you do it like this, 2
When the operating state is such that the secondary air should be cut or reduced, there is a certain degree of response delay in the operation of the flow control valve, and during this response delay, supercharged air flows out into the secondary air passage. , measures are required to prevent this from causing distortions in the air-fuel ratio.

(Object of the Invention) In view of these circumstances, the present invention includes a first air amount detection device that detects the total amount of intake air introduced into the intake passage, and a second air amount detection device that detects the amount of secondary air sent to the exhaust system.
When controlling the amount of fuel injection from the fuel injection device according to the amount of intake air supplied to the combustion chamber, which is determined by subtracting the amount of secondary air from the total amount of intake air, To control the amount of fuel injection with high precision even in an operating state where the supply of secondary air is stopped or reduced by a control valve, or even when the operating state changes to such an operating state. The purpose is to provide a supercharged engine that can.

(Structure of the Invention) The present invention has one end connected to an intake passage downstream of a supercharger and the other end connected to an exhaust passage of an engine, so that a part of the air pressurized by the supercharger is transferred to the exhaust passage. a first air amount detection device provided in the intake passage upstream of the supercharger and outputs a signal corresponding to the amount of air flowing through the passage; A second air amount detection device outputs a signal corresponding to the amount of air flowing through the passage, and a second air amount detection device receives outputs from the first and second air amount detection devices and calculates a second signal from the air amount detected by the first air amount detection device. In a supercharged engine equipped with an electronically controlled fuel injection device that determines and supplies a fuel injection amount corresponding to the air amount obtained by subtracting the air amount detected by the air amount detection device, the secondary air passage is sent to the exhaust passage. In addition to providing a flow control valve to control the amount of secondary air introduced,
When the flow rate control valve enters an operating state in which it operates to stop or reduce the supply of secondary air, continuing to detect the secondary air amount by the second air amount detection device for a predetermined period from that point, Thereafter, a control means is provided to substantially stop detection of the amount of secondary air. In other words, in the present invention, 2
During operating conditions in which a certain amount of secondary air is sent to the exhaust system through the secondary air passage, and immediately after operating conditions in which the supply of secondary air is stopped or reduced by the flow control valve. , for a predetermined period commensurate with the response delay of the flow control valve.
The substantial amount of secondary air is detected by the air amount detection device, thereby preventing deviations in the air-fuel ratio due to response delays of the flow rate control valve that controls the flow of secondary air.

(Embodiment) Fig. 1 shows an embodiment of the device of the present invention. In this embodiment, a supercharger is provided in an intake passage (supercharging passage) branched from a main intake passage, and a The present invention is applied to a structure in which a secondary air passage is connected between a supercharging passage and an exhaust passage. In this figure, 1 is a cylinder of an engine, 2 is a piston, and 3 is a combustion chamber formed above the piston 2 in the cylinder 1. A main intake port 4, a supercharging port 5, and an exhaust port 6 are opened in this combustion chamber 3, and a main intake valve 7,
A supercharging intake valve 8 and an exhaust valve 9 are provided.

10 is an air cleaner, 11 is an air cleaner 10
This is the intake passage connected to the The intake passage 11 is
Consisting of a main intake passage 12 and a supercharging passage 13 branched from the main intake passage 12, the downstream end of the main intake passage 12 is connected to the main intake port 4, and the downstream end of the supercharging passage 13 is connected to the supercharging passage 13. Connected to port 5. A first air amount detection device (air flow meter) 14 is provided in the intake passage 11 upstream of the branch point between the main intake passage 12 and the supercharging passage 13 . Also, in the main intake passage 12, a first throttle valve 15 is provided which is opened and closed in accordance with the operation of the accelerator pedal.
is provided, and a fuel injection device 16 is installed downstream thereof.

On the other hand, the supercharging passage 13 is provided with a supercharger 17 consisting of a vane type air pump driven by the engine. An intercooler 18 is provided downstream of the supercharger 17 to cool the supercharged air supplied from the supercharger 17 in order to increase its density.
A surge tank 19 is formed downstream thereof.
Further, a second throttle valve 20 is provided in the supercharging passage 13 downstream of the surge tank 19, and this second throttle valve 20 is opened to an opening degree corresponding to the load when the load is higher than a predetermined load. When the throttle valve 15 is opened to a predetermined opening degree or more, it is opened in conjunction with this. Further, from the surge tank 19 of the supercharging passage 13, there is a secondary air passage 21 that sends a part of the supercharging air to the exhaust system as secondary air for exhaust gas purification, and a relief valve that relieves excess supercharging air. The passage 22 is branched.

The secondary air passage 21 is connected to the exhaust system, and in the embodiment shown in the figure, the secondary air passage 21 has a large flow passage 21a having a relatively large passage area and a large flow passage 21a having a small passage area at its downstream portion. The large flow passage 21 a opens into an exhaust passage 24 upstream of the catalytic converter 23 , and the small flow passage 21 b opens into an intermediate portion of the catalytic converter 23 . The reason why the secondary air passage 21 is configured in this way is to supply a relatively large amount of secondary air to the upstream side of the catalytic converter 23 during idling when operating with a rich air-fuel mixture. , acts as an oxidation catalyst to reduce CO, and when operating at approximately the stoichiometric air-fuel ratio, a small amount of secondary air is supplied to the rear half of the catalytic converter 23 to reduce NOx.
This is because it functions as a three-way catalyst for reducing HC and CO.

This secondary air passage 21 is provided with a second air amount detection device 25 that detects the flow rate of the secondary air, and in the figure, detects the pressure difference between the upstream side and the downstream side of the throttle 25a in the secondary air passage 21. The differential pressure sensor 25b is used to detect the amount of secondary air in a control unit 40, which will be described later, based on its output, thereby forming a second air amount detection device 25. Furthermore, the secondary air passage 21 includes two air channels depending on the operating state.
As a flow rate control valve that controls the flow rate of secondary air, an on-off valve 26 that opens and closes the secondary air passage 21 downstream of the second air amount detection device 25, and a large flow passage 2
A switching valve 27 that opens either of the passages 21a and 21b is provided at a branch point between the passage 1a and the passage 21b for small flow rate. The on-off valve 26 includes a valve body 26a and a diaphragm type actuator 26.
b, and opens the secondary air passage 21 when negative pressure is introduced into the actuator 26b, and closes the secondary air passage 21 when the atmosphere is introduced. The switching valve 27 is also composed of a valve body 27aa and a diaphragm type actuator 27b, and when negative pressure is introduced into the actuator 27b, the large flow passage 21a is opened, and when the atmosphere is introduced, the small flow passage 21b is opened. That's what I do.
The actuator 26b of the on-off valve 26 has one end connected to the main intake passage 12 downstream of the first throttle valve 15.
The actuator 27b of the switching valve 27 is connected to the negative pressure passage 28 connected to the passage 31 and the second three-way solenoid valve 30 via a passage 29 and a first three-way solenoid valve 30. Solenoid valve 32
connected via. Each of these three-way solenoid valves 3
0 and 32 are each of the above actuators 26, respectively.
b, 27b are selectively communicated with the negative pressure passage 28 or the openings 30a, 32a to the atmosphere.

Further, the relief passage 22 is arranged so as to recirculate surplus supercharging air to the main intake passage 12 or the supercharging passage 13 upstream of the supercharger 17. It is connected to the intake passage 12. The relief passage 22 includes a boost pressure control valve 33 that mainly controls the maximum boost pressure during high loads, and a boost pressure control valve 33 that opens the relief passage 22 when the on-off valve 26 of the secondary air passage 21 is opened, and A relief control valve 34 for preventing excessive supply of secondary air is arranged in parallel with the air conditioner. The supercharging pressure control valve 33 has a valve body 33a disposed at an opening 35 of the relief passage 22 with respect to the surge tank 19.
and the diaphragm 3 connected to this valve body 33a.
3b and a pressure control chamber 33c formed on one side thereof.
and a spring 33d that biases the valve body 33a in the valve closing direction, and when the supercharging pressure applied to the valve body 33a becomes excessively high, the valve body 33a opens to relieve supercharging air. This controls the maximum boost pressure. By connecting the pressure control chamber 33c to the negative pressure passage 28, the maximum boost pressure can be suppressed to a certain level during low loads where the intake negative pressure is large, and the maximum boost pressure can be suppressed to a certain level during high loads where the intake negative pressure is small. I'm trying to improve it.

The relief control valve 34 includes a valve body 34a disposed in a communication hole 36 between the relief passage 22 and the surge tank 19, and a diaphragm type actuator 34b. It is connected to the negative pressure passage 28 via one three-way solenoid valve 30 . Therefore, this relief control valve 34 is connected to the secondary air passage 2.
It is designed to be opened and closed in response to the opening and closing valve 26 of No. 1.

The fuel injection device 16 and the three-way solenoid valves 30, 32 are controlled by a control unit 40 using a microcomputer or the like, and the control unit 40 includes the first air amount detection device 14 and the second air amount detection device. In addition to the detection signals from the engine rotation speed sensor 41 and the throttle opening detection signal corresponding to the load from the throttle opening sensor 42 which detects the opening degree of the first throttle valve 15, is entered.

In order to control the secondary air supply according to the operating state, the control unit 40 preliminarily sets the operating region where the engine speed and the load are below predetermined values as the secondary air supply region, as shown in FIG. The rest of the area is set as the air cut area (area where the supply of secondary air is stopped), and of the secondary air supply area, the low rotation area and low load area are set as the secondary air large area, and the other areas are set as the secondary air cut area. It is set as a small amount area. When the operating state detected from the engine speed and the throttle opening (load) is in a high secondary air volume region, the large flow passage 21a is opened, and when the operating state is in a low secondary air volume region, the high flow passage 21a is opened. The on-off valve 26 and the switching valve 27 are controlled via the three-way solenoid valves 30 and 32 so that the small flow passage 21b is opened and the secondary air passage 21 is closed when in the air cut region.

Further, the control unit 40 controls the first
The amount of intake air supplied to the combustion chamber 3 is determined by subtracting the amount of secondary air from the amount of intake air detected by the air amount detection device 14, and the amount of intake air supplied from the fuel injection device 16 is determined according to this amount of intake air supplied. Controls fuel injection amount. In particular, by performing the process for controlling the fuel injection amount according to the program shown in the flowchart of FIG. 3, when the operating state is reached in which the secondary air is cut or reduced,
For a predetermined period of time from that point on, the second air amount detection device 25
The controller constitutes a control means that continues to detect the amount of secondary air and then substantially stops this detection. That is, when such an operating state changes, a control signal for switching the on-off valve 26 or the switching valve 27 is output to the three-way solenoid valve 30 or 32, but from this point on, the on-off valve 26 or the switching valve 27 is also switched off. The detection of the secondary air amount is continued for a predetermined period of time commensurate with the response delay of the operation.

The function of this control means will now be explained with reference to the flowchart of FIG.

In this flowchart, we will first
In step _S1 , the intake air amount Qa detected by the first air amount detection device 14 is read, and in step _S2 , the rotation speed sensor 41 and the throttle opening sensor 42 are read.
The operating status is detected based on the output of the Next, it is determined in step _S3 which operating region in FIG. 2 the detected operating state is in, that is, whether it is in the air cut region or _not . Determine whether it is in the area. Although not shown in this flowchart, the on-off valve 26 and the switching valve 27 are controlled via the three-way solenoid valves 30 and 32 as described above in accordance with the determination result of the operating range.

When it is determined in step _S4 that the secondary air amount is in the region, the flow rate _Qb2 detected based on the output of the differential pressure sensor 25b is set as the secondary air amount Qb (steps _S5 , _S6 ). Also, if it is determined in step _S3 that the area is in the air cut area, in step _S7 ,
It is determined whether or not a predetermined period of time (for example, 3 seconds) has elapsed since the operating state changed from the secondary air volume region to the air cut region. And this step S ₇
When the judgment result is YES, the flow rate Qb ₂ calculated based on the output of the differential pressure sensor 25b is set as the secondary air amount Qb in the same way as when the secondary air amount is in the large amount area.
When the determination result in step _S7 is NO, the secondary air amount Qb is set to zero in step _S8 .

Also, when the judgment result in step _S4 is NO,
In other words, when the secondary air is in the small amount region, the flow rate Qb ₂ is calculated based on the output of the differential pressure sensor 25b (step S ₉ ), and the small flow passage 21b
The flow rate Qb ₁ of is determined from the map corresponding to the operating state (step S ₁₀ ). In other words, the small flow passage 21
2 in various operating conditions when b is open.
The flow rate of the air is experimentally investigated in advance and stored as a map in the memory within the control unit 40, and values corresponding to the actual operating conditions are read from this map. Next, in step _S11 , it is determined whether or not a predetermined period of time (for example, 3 seconds) has elapsed since the operating state changed from the high-volume secondary air region to the low-volume secondary air region, and if the determination result is YES, In step _S12 , it is determined whether the flow rate _Qb2 calculated based on the output of the differential pressure sensor 25b is larger than the flow rate _Qb1 of the small flow passage 21b calculated from the map. And step S ₁₁ ,
If both judgment results in _S12 are YES, step
Proceeding to _S6 , the flow rate Qb ₂ calculated based on the output of the differential pressure sensor 25b is set as the secondary air supply amount Qb,
Otherwise, if the secondary air is in a small amount area, the small flow passage 21 read from the map in step _S13
Let the flow rate Qb ₁ of b be the secondary air amount Qb.

After any one of steps S ₆ , S ₈ , and S ₁₃ , the intake air supply amount Q to the combustion chamber 3 is determined by subtracting the secondary air supply amount Qb from the intake air amount Qa (step S ₁₄ ), and this The fuel injection amount is controlled according to the intake air supply amount Q (step _S15 ).

By controlling according to this flowchart,
When a relatively large amount of secondary air is being supplied to the exhaust system through the large flow passage 21a of the secondary air passage 21, the second
The amount of secondary air is detected by the air amount detection device 25, and the amount of intake air supplied to the combustion chamber 3 is determined based on the detected value of the intake air amount and the detected value of the secondary air amount by the first air amount detection device 14. is calculated and the fuel injection amount is controlled accordingly. On the other hand, when the secondary air passage 21 is closed and the supply of secondary air is stopped, the secondary air quantity is set to zero and the detection by the second air quantity detection device 25 is not performed, and the small flow passage 21b
Even when a small amount of secondary air is supplied to the exhaust system through the air flow, the value determined from the map according to the operating condition is taken as the secondary air amount, so that the second air amount detection device 25 is substantially detection will be stopped. By doing this, when the supply of secondary air is stopped or when the amount of secondary air is small, the detected value of the second air amount detection device 25, which tends to have errors due to the influence of the discharge pressure of the supercharger, is exactly than the case 2
Next, the amount of air is determined.

Further, when the operating state changes from a large amount of secondary air region to an air cut region or a small amount of secondary air region, a control signal is output to the three-way solenoid valves 30 and 32 accordingly, and then the on-off valve 26 is switched to the secondary air state. A certain amount of response delay occurs until the air passage 21 is closed or the switching valve 27 switches to a state in which the large flow passage 21a is closed and the small flow passage 21b is opened. During this response delay time, a relatively large amount of secondary air flows out into the exhaust system through the large flow passage 21a, so the time required to compensate for the response delay of the on-off valve 26 or the switching valve 27 is ,
The secondary air amount is detected by the second air amount detection device 25 through processing according to the determination result in step S ₇ or S ₁₁ and S ₁₂ .

Note that a large flow passage 21a and a small flow passage 21 are branched at the downstream portion of the secondary air passage 21.
The opening position of b with respect to the exhaust system may be changed within a preferable range for the exhaust purification effect. Further, the secondary air passage 21 is formed without branching as described above,
Only the on-off valve 26 may be provided as the flow rate control valve, and in this case, the flow rate control valve may be used at a predetermined time when in the secondary air supply area and immediately after the operation state where the supply of secondary air is to be stopped. The secondary air amount may be detected by the second air amount detection device 25 during the period.

(Effects of the Invention) As described above, the supercharged engine of the present invention adjusts the fuel injection amount according to the value obtained by subtracting the secondary air amount from the total intake air amount detected by the first air amount detection device. When controlling, when a certain amount of secondary air is being supplied to the exhaust system, the secondary air amount is detected by the second air amount detection device, and the supply of secondary air is stopped by the flow control valve. or when the secondary air supply amount is reduced, the detection of the secondary air amount by the second air amount detection device is substantially stopped, and the pulsation of the discharge pressure of the supercharger, etc. This prevents false detections caused by In particular, when switching to such a state, the secondary air amount is detected for a predetermined period of time commensurate with the response delay of the flow control valve operation, so even at this time, the air-fuel ratio is Therefore, the amount of fuel injection can be controlled with high precision.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing one embodiment of the present invention, and FIG.
The figure is an explanatory diagram showing operating ranges in which a large amount of secondary air is supplied, a small amount is supplied, and the supply is stopped to the exhaust system, and FIG. 3 is a flowchart for controlling the fuel injection amount. 12... Main intake passage, 13... Supercharging passage, 14
...First air amount detection device, 16...Fuel injection device, 21...Secondary air passage, 25...Second air amount detection device, 26...Opening/closing valve, 27...Switching valve, 4
0...Control unit.

Claims (1)

[Claims] 1 One end is connected to the intake passage downstream of the supercharger, and the other end is connected to the exhaust passage of the engine,
A secondary air passage that guides a portion of the air pressurized by the turbocharger to the exhaust passage, and a primary air passage that is provided in the intake passage upstream of the turbocharger and outputs a signal corresponding to the amount of air flowing through the passage. an amount detection device, a second air amount detection device provided in the secondary air passage and outputting a signal corresponding to the amount of air flowing through the passage, and receiving outputs from the first and second air amount detection devices, an electronically controlled fuel injection device that determines and supplies a fuel injection amount corresponding to the air amount obtained by subtracting the air amount detected by the second air amount detection device from the air amount detected by the first air amount detection device; In a supercharged engine, 2
A flow control valve is provided in the secondary air passage to control the amount of secondary air introduced into the exhaust passage, and when the flow control valve is in an operating state in which it operates to stop or reduce the supply of secondary air. , 2 by the second air amount detection device for a predetermined time from that point.
A supercharged engine characterized in that a control means is provided to continue detecting a secondary air amount and then substantially stop detecting the secondary air amount.