JPS61207869A - Intake secondary air supply device of internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent air-fuel ratio from generating large hunting, by detecting an overrich state of the air-fuel ratio from an engine operation parameter in good reaction for deceleration and supplying intake secondary air of quantity corresponding to said parameter. CONSTITUTION:If an engine being in a deceleration condition is decided from a change value DELTAPBA of the absolute pressure PBA, a supply device, opening an electromagnetic opening and closing valve 9 only for a time TSH corresponding to the change value DELTAPBA, supplies intake secondary air to the engine through an intake secondary air passage. In this way, when deceleration of the engine is started at a point of time t1 in the drawing, the device, earlier supplying the secondary air anticipating a change of air-fuel ratio in deceleration, can prevent the air-fuel ratio from its large change as shown by a full line B in the drawing. While a broken line A shows a case that the air-fuel ratio is corrected in accordance with an output level of an oxygen concentration sensor 14 in the past. While a one-dot chain line C shows a case that no intake secondary air is supplied.

Description

TECHNICAL FIELD The present invention relates to an intake secondary air supply system for an internal combustion engine.

Background technology In order to purify the exhaust gas of internal combustion engines and improve fuel efficiency, the oxygen concentration in the exhaust gas is detected by an oxygen concentration sensor, and the air-fuel ratio of the mixture supplied to the engine is fed back according to the output level of this oxygen concentration sensor. Air-fuel ratio control devices are known. As this air-fuel ratio control device, the intake air 2 is connected to the intake manifold downstream of the carburetor throttle valve.
There is an intake secondary air supply device for feedback control that provides an on-off valve in the secondary air supply passage and controls the opening/closing of the on-off valve according to the output level of the oxygen concentration sensor, that is, the amount of intake secondary air (for example, the No. 55-3533]
.

In such conventional intake secondary air supply devices, the air-fuel ratio of the supplied air-fuel mixture is detected from the output level of the oxygen concentration sensor, so even if the air-fuel ratio changes, it takes time for the change in the air-fuel ratio to be detected. Therefore, the air-fuel ratio control by supplying the intake secondary air is slightly delayed, which may result in hunting of the air-fuel ratio.

In particular, immediately after the start of engine deceleration, the negative pressure in the intake manifold rapidly increases, and the fuel adhering to the inner wall of the intake manifold evaporates, causing the air-fuel ratio of the supplied mixture to become over-left, resulting in a control delay. There was a problem in that hunting of the air-fuel ratio became large due to this, resulting in deterioration of drivability.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an intake secondary air supply device that can prevent hunting of the air-fuel ratio immediately after the start of engine deceleration and improve driveability.

The intake secondary air supply device for an internal combustion engine according to the present invention includes a first detection means for detecting exhaust component concentration, a second detection means for detecting an engine operating parameter whose value changes in accordance with deceleration of the engine, and an intake secondary air supply device for an internal combustion engine. The air-fuel ratio is determined from the detection level of a flow rate adjustment valve provided in the air supply passage and the first detection means, the flow rate adjustment valve is controlled according to the determination result, and the engine is in a deceleration state from the detection level of the second detection means. and control means for controlling the flow rate regulating valve in accordance with the detection level of the second detection means, regardless of the detection level of the first detection means, only when it is determined that the flow rate adjustment valve is present.

Example Embodiments of the present invention will be described below with reference to the drawings.

In the intake secondary air supply system for an on-vehicle internal combustion engine, which is an embodiment of the present invention shown in FIG. 5. vaporizer 3
is provided with a throttle valve 6, and a pliers area is formed upstream of the throttle valve 6.

The intake manifold 4 and the vicinity of the air discharge port of the air cleaner 2 are communicated with each other by an air supply passage 8 within the intake 2.

An electromagnetic on-off valve 9 is provided in the intake secondary air supply passage 8 . The electromagnetic on-off valve 9 is opened when the solenoid 9α is energized.

10,000, IO is an absolute pressure sensor installed in the intake manifold 4 and generates an output at a level corresponding to the intake absolute pressure in the intake manifold 4, and 11 is a pulse sensor that generates a pulse according to the rotation of the crankshaft (not shown) of the engine 5. 12 is a cooling water temperature sensor that generates an output at a level corresponding to the cooling water temperature of the engine 5; 14 is an exhaust manifold 15 located downstream of the exhaust gas oxygen concentration sensor 14 of the engine 5; A catalyst inverter 33 is provided to promote the reduction of harmful components in exhaust gas. Electromagnetic on-off valve 9, absolute pressure sensor 10, crank angle sensor 11
, the water temperature sensor 12 and the oxygen concentration sensor 14 are connected to the control circuit 2.
Connected to 0.

The control circuit 20 includes an absolute pressure sensor 10, as shown in FIG.
A level conversion circuit 21 that converts each output level of the water temperature sensor 12 and the oxygen concentration sensor 14; and a level conversion circuit 21.
A multiplexer 22 that selectively outputs one of the sensor outputs that have passed through the multiplexer 22, and an A/D converter 23 that converts the signal output from the multiplexer 22 into a digital signal.
A waveform shaping circuit 24 that shapes the output signal of the crank angle sensor 11, a counter 25 that measures the generation interval of the TDC signal output as a pulse from the waveform shaping circuit 24, and a drive circuit that drives the electromagnetic on-off valve 9 to open. 28, a CPU (central processing circuit) 29 that performs digital calculations according to programs, a ROM 30 in which six processing programs and data are written in advance, and a RAM 31. The multiplexer 22, A/D converter 23, counter 25, drive circuit 28, CPU 29, R, OM 30, and rib N31 are connected to each other by an input/output bus 32.

In this configuration, the information on the absolute pressure PBA in the intake manifold 4, the cooling water temperature Tw, and the oxygen concentration in the exhaust gas is alternatively sent from the A/D converter 23, and the information representing the engine rotation speed is alternatively sent from the counter 25. are respectively supplied to the CPU 29 via an input/output bus 32. The CPU 29 is configured to generate an internal interrupt signal every duty cycle (for example, 100 m5ec), and in response to this interrupt signal, performs an operation for duty-controlling the intake secondary air supply as described later. Let's do it.

Next, the operation of the intake secondary air supply device according to the present invention will be explained according to the operation flow diagram of the CPU 29 shown in FIG.

In the CPU 29, first, each time an interrupt signal is generated, it is determined whether or not it is equal to the flag F8Hdf"t" for determining secondary air supply during deceleration (step 51).

If F'5H=o, it is initialized when the engine 5 is started, and it indicates that the engine 5 was determined not to be in a deceleration state during the previous execution of this routine, so the intake manifold 4 per unit time The change value ΔPBA of the absolute pressure PIIA within the first predetermined value PK (for example, −100 m
It is determined whether Hf ) is smaller than (step 52)
. If ΔPBA≧P, it is determined that the engine 4 is not in a deceleration state, and it is determined whether other air-fuel ratio feedback (F/B) control conditions are satisfied (step 53).
. This determination is determined based on the absolute pressure PBA in the intake manifold 4, the coolant temperature Tw, the engine speed N2, etc., and for example, it is determined that the air-fuel ratio feedback control condition is not satisfied at low coolant temperature and low engine speed. .

Here, if it is determined that the air-fuel ratio feedback control conditions are satisfied, the reference secondary air supply period for the l duty period, that is, the reference valve opening period DB of the electromagnetic on-off valve 9
A8m is set (step 54). For example, ROM
30, a reference valve opening period DBABE determined from the absolute pressure PBA in the intake manifold and the engine speed N is written in advance as a data map, and the CPU 29 reads the absolute pressure PB.
A and the engine speed N are read, and a reference valve opening period corresponding to the six read values is searched from the DBASE t' data map. When the reference valve opening period DBAsE is set, the oxygen concentration sensor 14
output level L. 2 is the reference level Lrgf Ext.2 corresponding to the target air-fuel ratio (step 5).
5). That is, it is determined whether the air-fuel ratio of the air-fuel mixture supplied to the engine 5 is equal to the target air-fuel ratio. If L, 2)L□f, the air-fuel ratio is the target air-fuel ratio Efree, so the correction value is I. A predetermined value AF is subtracted from UT, and the calculated value is used as a new correction value l0UT (step 56).

On the other hand, if Lox≦Lrtf, the air-fuel ratio is richer than the target air-fuel ratio, so a predetermined value AF is added to the correction value l0UT, and the calculated value is a correction value I that is discontinuous. UT (step 57). When the correction value IoU is thus calculated in step 56 or &7, the correction value IoU
T and the reference valve opening period DB set in step 54
A8E is added, and the addition result is set as the opening period TOUT of the electromagnetic on-off valve 9 in one working cycle (step 58). Then, this valve opening period TOUT is
29 is set in the internal time counter A (not shown), the time counter A starts counting down (step 59), and a valve opening drive command is generated to the drive circuit 28 (step 60). In response to the valve drive command, the drive circuit 28 drives the electromagnetic on-off valve 9 to open.Next, it is determined whether or not the count value of the time counter A has reached "0" (step 61). Count value is “0”
If it has not been reached, step 61 is repeated. When the count value of the time counter A reaches "0", a valve opening drive stop command is issued to the drive circuit 28 (step 62). Valve open period T calculated in step 58 by executing step 62. The UT-take solenoid on-off valve 9 is opened and the intake secondary air flows into the engine 5.
The next air is supplied via the air supply passage 8. Because the above-mentioned operation is repeated, the intake secondary air is subjected to duty control, and the air-fuel ratio of the air-fuel mixture supplied to the engine 5 is controlled to the target air-fuel ratio.

- If ΔPBA<Pl in step 52, a deceleration state is established and a deceleration secondary air supply period TSH is set (step 63). Absolute pressure PB for R10M30
Since the secondary deceleration secondary air supply period TSH determined as shown in FIG. 4 for the change value ΔPBA of A is written in advance as a data map, CPO29 is the change value ΔPB
The data map is also searched for the deceleration secondary air supply period TSH corresponding to A. When the deceleration secondary air supply period TSH is set, the deceleration secondary air supply period T8H is set in the internal time counter B (not shown) of the CPU 29, and down counting of the time counter B is started (step 64).
.

Then, the flag F'SH is set to "1" indicating a deceleration state (step 65). Next, it is determined whether the dog is a dog or not based on the change value ΔPBA of the absolute pressure PBA being a second predetermined value P2 (for example, 50 Ht) (step 67). This determination is performed to detect whether the engine 5 has transitioned to an acceleration state after FSH=1. ΔPBA
If ≦P2, the count value of time counter B is “O”
It is determined whether the count value of the time counter B has reached "O" (step 68), and a valve opening drive command is issued to the drive circuit 28 (step 66). .

On the other hand, if the count value of the time counter B reaches "O", a valve opening drive stop command is issued to the drive circuit 28 (step 69), and "0"' is set in the 7-lag F'SH. , and are removed (step 70). If it is determined in step 67 that ΔPBA>Pt, the count value of time counter B is reset to "0'', assuming that the engine 5 has transitioned from the deceleration state to the acceleration state (step 67).
1), then step 69 is executed.

On the other hand, if it is determined in step 51 that F'5H=1, that is, if the electromagnetic on-off valve E is in the opening operation, step 67 is immediately executed.

In the intake secondary air supply device according to the present invention,
When it is determined from the change value ΔPBA of the absolute pressure PBA that the engine 5 is in a deceleration state, the □take solenoid on-off valve 9 is opened for 9 hours T according to the change value ΔPBA, and the intake secondary air is transferred to the intake secondary air. The air is supplied to the engine 5 via the air supply passage 4'i. That is, the amount of intake secondary air is supplied depending on the magnitude of deceleration.

Therefore, when the engine 5 starts decelerating at time 1K shown in FIG.
If the air-fuel ratio during deceleration is corrected by supplying intake secondary air according to the output level of No. 4, the air-fuel ratio will fluctuate greatly immediately after the start of deceleration, resulting in large hunting, as shown by broken line A.

However, according to the intake secondary air supply device according to the present invention, fluctuations in the air-fuel ratio during deceleration can be predicted and the air-fuel ratio can be adjusted as early as possible.
Since the secondary air is supplied, it is possible to prevent the air-fuel ratio from fluctuating as shown by the solid line B. Note that the characteristic shown by the dashed line C is the change characteristic during deceleration when the intake secondary air is not supplied.

When the engine 5 shifts from the deceleration state to the acceleration state,
Since the electromagnetic on-off valve 9t is immediately closed and the supply of intake secondary air is stopped, leafing of the air-fuel ratio is prevented and drivability during acceleration can be improved.

In the intake secondary air supply device according to the present invention, when the vehicle runs at the slow speed traveling pattern shown in FIG. Immediately after the start of operation, the opening duty ratio of the electromagnetic on-off valve 9 is 1, as shown by the symbol in Fig. 6<b>.
00%, and secondary air is supplied to the engine 5 during deceleration.

In the embodiments of the present invention described above, the intake pressure in the intake manifold is used as an engine operating parameter whose value changes according to the deceleration of the engine; however, the intake pressure in the intake manifold is not limited thereto. It is also possible to use vehicle speed or engine speed.

Further, in the embodiment of the present invention described above, an electromagnetic on-off valve is provided in the intake secondary air supply passage as a flow rate adjustment valve in order to improve responsiveness, but the invention is not limited to this. It is also possible to provide a pressure-responsive on-off valve that operates or a regulating valve whose opening degree can be freely controlled.

Effects of the Invention As described above, in the intake secondary air supply device for an internal combustion engine of the present invention, the deceleration state of the engine is not detected as an overrich air-fuel ratio from the exhaust component concentration during air-fuel ratio feedback control, but is detected as a deceleration state. The intake secondary air is detected from engine operating parameters that have good responsiveness to the engine operating parameters, and the next amount of intake secondary air is supplied in accordance with the engine operating parameters before the air-fuel ratio becomes overrich due to deceleration. Therefore, it is possible to avoid overrich conditions immediately after the start of engine deceleration, reduce harmful components in the exhaust gas, and prevent large hunting in the air-fuel ratio due to control delays, thereby improving drivability. . Since fc nitrogen fuel ratio feed puncture control and air fuel ratio correction during deceleration are possible using the same intake secondary air supply passage and flow rate adjustment valve, the configuration is simple and costs can be reduced. .

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a specific configuration of a control circuit in the device shown in FIG. 1, FIG. 3 is a flow diagram showing the operation of the CPU, and FIG. This figure shows the setting characteristics of the deceleration secondary air supply period TSH, and the fifth factor and FIG. 6 are diagrams showing the operating state of the apparatus shown in FIG. 1. Explanation of symbols for main parts 2... Air cleaner 3... Carburetor 4... Intake manifold 6... Throttle valve 7... Venturi 8... Intake secondary air supply passage 9... Electromagnetic opening/closing Valve lO...Absolute pressure sensor 1
1... Crank angle sensor 12... Cooling water temperature sensor 14... Oxygen concentration sensor 15... Exhaust manifold 33... Catalytic converter

Claims (5)

[Claims] (1) A first detection means for detecting the concentration of exhaust components of an internal combustion engine, and an intake 2 that communicates with the intake passage downstream of the carburetor throttle valve.
a secondary air supply passage; a flow rate adjustment valve provided in the intake secondary air supply passage; a second detection means for detecting an engine operating parameter whose value changes in accordance with deceleration of the engine; The air-fuel ratio is determined from the detection level, and the flow rate adjustment valve is controlled according to the determination result, and only when it is determined from the detection level of the second detection means that the engine is in a deceleration state, the first detection means is activated. and control means for controlling the flow rate adjustment valve according to the detection level of the second detection means regardless of the detection level. (2) The engine operating parameter is the intake absolute pressure downstream of the carburetor throttle valve, and the control means sets the deceleration state when it detects that the change value per unit time of the intake absolute pressure is below a predetermined value. The intake secondary air supply device according to claim 1, characterized in that the intake secondary air supply device is characterized in that: (3) The intake secondary air supply device according to claim 1, wherein the flow rate adjustment valve is an electromagnetic on-off valve. (4) When the control means determines that there is a deceleration state, the control means opens the flow rate regulating valve for a time corresponding to the change value per unit time of the operating parameter to supply secondary air to the engine during deceleration. An intake secondary air supply device according to claim 1. (5) The intake air system according to claim 1, wherein the control means immediately closes the flow rate adjustment valve when an acceleration state of the engine is detected during the supply of secondary air during deceleration. Next air supply device.