JPS6287637A - Internal combustion engine intake secondary air supply device - Google Patents

Abstract

PURPOSE:To prevent air-fuel ratio control accuracy from getting worse as well as to aim at stabilization in a driving state at the time of idle running or the like, by restricting a secondary air flowing in a suction secondary air supply passage at the time of a low suction air quantity in an engine. CONSTITUTION:At a control circuit 20, if an engine speed and absolute pressure inside a suction pipe both are smaller the specified value by each information out of a crank angle sensor 11 and an absolute pressure sensor 10, it is so discriminated that an engine is at time of a low suction air quantity, whereby current-energization to a solenoid 17a is stopped and a solenoid on-off valve 17 is closed. And, a solenoid valve 9 is opened at the output valve opening time compensated according to an output level of an oxygen content sensor 14 by a duty ratio multiplying a reference duty ratio depending on the engine speed and the absolute pressure inside the suction pipe ten times, so that secondary air is fed to the inside of a suction manifold 4 only through a throttle valve 18. Therefore, at this time, it comes to a secondary air quantity of one-tenth to such an air quantity that is flowable in a suction secondary air supply passage 8 at the time of opening of the solenoid on-off valve 17 with opening of the solenoid valve 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake secondary air supply V device for an internal combustion engine.

11nl of oxygen in the exhaust gas for the purpose of purifying the exhaust gas of an internal combustion engine and improving fuel efficiency! An air-fuel ratio control U device is known that detects I and feedback-controls the air-fuel ratio of the air-fuel mixture supplied to the engine to a target air-fuel ratio according to the detection result. This air-fuel ratio control device provides an on-off valve in the intake secondary air supply passage that communicates with the downstream side of the carburetor throttle valve, and controls the opening and closing of the on-off valve according to the output level of the oxygen atq sensor. There is also an intake secondary air supply device for duty-controlling the intake secondary air supply (for example, Japanese Patent Publication No. 55-3533).

In such an intake secondary air supply device, the amount of secondary air passing through the on-off valve is small in the range of 0 to 20%, where the duty ratio representing the opening time ratio of the on-off valve is small in one denity cycle. Since it hardly changes, it becomes impossible to obtain a secondary air flow rate corresponding to the duty ratio.However, at low engine speeds such as when the engine is idling, and when the intake pipe is under high negative pressure, the amount of intake air passing through the throttle valve is small. Since the amount of intake secondary air required to adjust the air-fuel ratio is also reduced, the duty ratio must be set to a value in a small range, which poses the problem that air-fuel ratio control accuracy deteriorates when the engine's intake air amount is low. .

1. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a secondary intake air supply device using a duty control method that can improve the accuracy of air-fuel ratio control when the intake air amount of an engine is low.

The intake secondary air supply device of the present invention is characterized by having a restriction means for restricting the amount of secondary air flowing through the intake secondary air supply passage when the intake air amount of the engine is low.

Length - 1 - Of course 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. is supplied to vaporizer 3
A throttle valve 6 is provided, and a venturi 7 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 through an intake secondary air supply passage 8. An electromagnetic on-off valve 9 is provided in the intake secondary air supply passage 8 . An electromagnetic on-off valve 17 and a throttle 18 are provided in parallel upstream from the location where the electromagnetic on-off valve 9 is provided.

On the other hand, 10 is an absolute pressure sensor installed in the intake manifold 4 and generates an output at a level corresponding to the absolute pressure inside the intake manifold 4, and 11 generates a pulse in response 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 oxygen sensor installed in the exhaust manifold 15 of the engine 5 and generates an output according to the oxygen concentration in the exhaust gas. It is a concentration sensor. A catalytic converter 33 is provided in the exhaust manifold 15 downstream of the oxygen a degree sensor 14 in order to promote the reduction of harmful components in the exhaust gas. Solenoid on-off valve 9, 17
, an absolute pressure sensor 10°, a crank angle sensor 11, a water temperature sensor 12, and an oxygen concentration sensor 14 are connected to a control circuit 20.

Further connected to the control circuit 20 is a vehicle speed sensor 16 that generates an output at a level corresponding to the speed of the vehicle.

As shown in FIG. 2, the control circuit 20 includes an absolute pressure sensor 10.
a level conversion circuit 21 that converts each output level of the water temperature sensor 12, the Fi element concentration sensor 14, and the vehicle speed sensor 16;
A multiplexer 22 that selectively outputs one of the sensor outputs that have passed through the level conversion circuit 21; and A that converts the signal output from the multiplexer 22 into a digital signal.
/D converter 23, 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 an electromagnetic on-off valve 9. A drive circuit 28a that drives the valve to open, a drive circuit 28b that drives the electromagnetic on-off valve 17 to open, a CPU (central processing circuit) 29 that performs digital calculations according to the program, and various processing programs and data are written in advance. ROM30 and RAM
It consists of 31. Multiplex+j-22, A/
D converter 23, counter 25, drive circuits 28a, 28b
1 CPU 29, ROM 30, and RAM 31 are connected to each other by an input/output bus 32.

In J3 having such a configuration, information on the absolute pressure in the intake manifold 4, cooling water temperature, oxygen concentration in exhaust gas, and vehicle speed is alternatively displayed from the A/D converter 23, and information on the engine speed is displayed from the counter 25. WAZ' information is supplied to the CPU 29 via an input/output bus 32, respectively. The CPU 29 is configured to generate an internal interrupt signal every duty period TSOL (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. . In addition, the internal interrupt signal etc. are sent to the electromagnetic on-off valve 1 at predetermined intervals or in synchronization with the engine rotation.
It is determined whether or not the valve 7 should be opened, and if it is determined that the valve should be opened, a first valve opening drive command is generated to the drive circuit 28b to cause the electromagnetic on-off valve 17 to open.

Next, the operation of the intake secondary air supply device according to the present invention will be explained in detail with reference to the operation flowcharts of the CPU 29 shown in FIGS. 3 to 5.

As shown in FIG. 3, the CPU 29 first determines whether the engine speed Ne is smaller than 1000 r, p, m (step 41). Neku1000r, p
, t, the absolute pressure inside the intake pipe PBA is 400 mmHg
It is determined whether Ne≧1 (step 42)
00 Or, p, m, or PBA≧40Q mmHg
If so, it is determined that the intake air is not at low intake 1, and the intake air amount determination flag Fo is set to "1" (step 43), and a first valve opening drive command is issued to the drive circuit 28b (step 44). The drive circuit 28b opens the electromagnetic on-off valve 17 by energizing the solenoid 17a in response to the first valve-opening drive command.
3 Drive the valve open. On the other hand, if Ne < 100 Or, p, m, and P BA < 400 mmHg, it is determined that the intake air amount is low, and the flag Fo is set to Opa (step 45), and the drive circuit 28b is Generation of the first valve drive command is stopped (step 46).

Also, as shown in Figure 4, each time an interrupt signal occurs, 1711
Question: In order to open and close the valve 9, the second
A valve opening drive stop command is generated (step 51). This is to prevent malfunction of the electromagnetic on-off valve 9 during the calculation operation of CP (J29). Next, the opening time T of the electromagnetic on-off valve 9 is determined.
AF is made equal to one duty period rsoL (step 52), and the A/F routine shown in FIG. 5 is executed to calculate the opening time TOLJT of the electromagnetic on-off valve 9 (step 53).

In the A/F routine, first, it is determined whether the operating state of the vehicle (including the operating state of the engine) satisfies air-fuel ratio feedback (F/B) control conditions (step 5).
31). This determination is based on the absolute pressure inside the intake manifold and the cooling water temperature. It is determined from the vehicle speed and engine rotational speed, and for example, it is assumed that the air-fuel ratio feedback control conditions are not satisfied at low vehicle speeds and low cooling water temperatures. Here, if it is determined that the air-fuel ratio feedback control conditions are not satisfied,
Valve opening time TOL to stop air-fuel ratio feedback control
JT is set to "0" (step 532). On the other hand, if it is determined that the air-fuel ratio feedback control conditions are satisfied, the secondary air supply for one duty period TSQL,
That is, the standard duty ratio (standard valve opening time) D8ASE for opening the electromagnetic on-off valve 9 is set (step 533).
. As shown in FIG. 6, the reference duty ratio DBASE determined from the intake manifold absolute pressure PBA and the engine speed Ne is pre-written in the ROM 30 as a DBASE data map, so the CPU 29 uses the absolute pressure PBA and the engine speed Ne. Ne and DBA the 1 meter semi-duty ratio D8ASE corresponding to the 6 values read.
Search from SE data map. Compared to standard duty,
After setting eAse, it is determined whether the intake air amount determination flag Fa is equal to 0'' (step 534), and if FQ=O, the reference duty ratio DBASE is multiplied by 10 (step 535). Next, a predetermined time Δ[
It is determined whether l has elapsed (step 536).
. The predetermined time Δt1 corresponds to a response delay time from when the intake secondary air is supplied until the result is detected by the oxygen concentration sensor 14 as a change in the oxygen concentration in the exhaust gas. When the predetermined time Δt1 has elapsed since the time counter A was reset and started counting, the time counter A is reset and counting starts from the initial value (step 537). That is, after the time counter Δ starts counting from the initial value by executing step 537, it is determined in step 536 whether or not the predetermined time Δt1 has elapsed. When the time counter A starts counting the predetermined time Δt1, a target air-fuel ratio leaner than the stoichiometric air-fuel ratio is set (step 538). In order to set this target air-fuel ratio, the ROM 30 contains the intake manifold internal absolute pressure PBA and engine rotation speed Ne as well as the D8ASE data map.
The reference level l re corresponding to the target air-fuel ratio determined from
t' is pre-populated as an A/F data map separately from the D[3A SE data map. Therefore, C.P.
U29 searches the A/F data map for a reference level Lref corresponding to the absolute pressure PBA and the engine speed Ne. Next, it is determined from the oxygen concentration information whether the output level 1-o2 of the oxygen concentration sensor 14 is greater than the reference level lrer determined in step 538 (step 539). That is, it is determined whether the air-fuel ratio of the air-fuel mixture supplied to the engine 5 is leaner than the target air-fuel ratio. If Lo2>1ref, the air-fuel ratio is leaner than the target air-fuel ratio, so a subtraction value IL is calculated (step 5310).

The subtracted value IL is obtained by multiplying a constant by +, the engine speed Ne, and the absolute pressure Ps A @multiplying each other Ne - PeA), and is made to depend on the intake air amount of the engine 5. After calculating the reduced n value IL, the correction value 10L that has already been determined by executing this A/F Luzin
IT is read from the storage location a1 of the RAM 31, and the read correction value I.

The subtraction value IL is subtracted from the IJT, and the calculated value is set as a new correction value 10UT, and is stored in the memory location a1 of the RAM 31.
1. : Written (step 5311).

On the other hand, if LO2≦l ref in step 539, the air-fuel ratio is higher than the target air-fuel ratio, so the addition fl
aIR is calculated (step 5312).

The additional value IR is obtained by multiplying the constant by 2 (≠ +), the engine speed Ne and the absolute pressure PBA (K2 ・Ne-P
8A), and depends on the intake air amount of the engine 5. After calculating the additional value IR, A
The correction value Io U T which has already been calculated by executing the /F routine is read from the storage location a1 of the ffiRAM 31, and the g'3 value IR is added to the read correction value 10LIT, and the ejection value is new. The correction value l0UT is stored in the memory location a1 of the RAM 31 (step 5313). In this way, the correction value 10UT is set at step 5.
Once calculated in step 311 or 5313, the correction value ■OUT is added to the reference duty ratio Da As E set in step 533, and the addition result is set as the valve opening time TOLJT (step 5314).

Note that if it is determined in step 536 that the predetermined time Δt1 has not elapsed after the time counter A has been reset in step 537 and started counting 81 from the initial value, step 5314 is immediately executed.
In this case, the correction value l01JT obtained by executing the A, /F routines up to the previous time is read out.

Δ/When the execution of the routine is completed, the valve closing time TAf is determined by subtracting the valve opening time OUT from one duty cycle T S OL (step 5/I).

Next, a value corresponding to the lower AF of the valve closing time 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 55).
. Then, it is determined whether or not the count value of time counter B has reached ``0'' (step 56), and if the count value of time counter B has reached O'', the drive circuit 2B is When the valve drive command is generated (step 57), the drive circuit 28 drives the electromagnetic on-off valve 9 to open in response to the second valve opening drive command, and during this time the valve drive state remains until step 51 is executed next. If the count value of time counter B does not reach '0'' in step 56, step 5G is repeatedly executed.

Therefore, in the intake secondary air supply device according to the present invention, the electromagnetic on-off valve 9 is immediately closed in response to the generation of the interrupt signal INT, and the supply of intake secondary air to the engine 5 is stopped. In addition, the valve closing time TAF of the electromagnetic on-off valve 9 in one duty period Ts OL is calculated, and when the valve opening time TAF has elapsed from the time when the interrupt signal is generated, the M magnetic on-off valve 9
is opened, and intake secondary air is supplied to the engine 5 via the intake secondary air supply passage 8. Because this operation is repeated, the intake secondary air is duty-controlled.

In addition, in the intake secondary air supply device according to the present invention, the electromagnetic on-off valve 17 is opened when the engine has a medium-high intake amount, and the reference duty ratio Do A S E set in step 533 is adjusted to the output level of the oxygen concentration sensor 14. The output valve opening time TOLIT is determined by correcting accordingly. When the engine intake air amount is low, the electromagnetic on-off valve 17 closes, and the value obtained by multiplying the reference duty ratio DBASE set in step 533 by 10 is set as the reference duty ratio D.
The output valve opening time TOLJT is determined by correcting BASE according to the output level of the oxygen concentration sensor 14. One duty period TSO is set by the drive circuit 28a.
In L, the solenoid valve 9 is opened only under the output valve opening time Tou, and when the engine intake air amount is low, the solenoid valve 9 is opened only through the throttle 18.
Since the secondary air is supplied into the intake manifold 4, the secondary air flow is 1/10 of the amount of air that can flow through the intake secondary air supply passage 8 when the electromagnetic on-off valve 17 is opened.

As described above, in the intake secondary air supply device of the present invention, the restriction stage 1 is provided for restricting the secondary air flow through the intake secondary air supply passage when the intake air amount of the engine is low. Therefore, even when the intake air amount of the engine is low, it is possible to accurately control the secondary air supply amount by using a characteristic portion with good linearity that allows a secondary air supply amount corresponding to the duty ratio of the on-off valve to be obtained.

Therefore, deterioration of the accuracy of air-fuel ratio control when the engine has a low intake air amount is prevented, and it is possible to stabilize the operating state during idling or the like.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing the specific configuration of the control circuit in the device shown in FIG. 1, and FIGS. 3 to 5 show the operation of the CPU. The flowchart, FIG. 6, is a diagram showing the data map corrupted to the ROM. Explanation of symbols of main parts 2... Air cleaner 3... Carburetor 4... Intake manifold 6... Throttle valve 7... Venturi 8 ...Intake secondary air supply passage 9.17 ...Solenoid on-off valve 10 ...Absolute pressure sensor 11 ...Crank angle sensor 12 ...・Cooling water temperature sensor 14... Oxygen concentration sensor 15... Exhaust manifold 18... Throttle 33... Catalytic converter applicant Honda Motor Co., Ltd. agent Patent attorney Master Motohiko Fujimura Figure 4 Figure 5 r, p, m.

Claims (2)

[Claims] (1) An intake secondary air supply passage communicating with the intake pipe downstream of the carburetor throttle valve of the internal combustion engine, a first on-off valve provided in the intake secondary air supply passage, and an exhaust gas passage of the engine. and an oxygen concentration sensor that determines the air-fuel ratio of the air-fuel mixture supplied to the engine according to the output level of the oxygen concentration sensor, and the first opening/closing valve within the predetermined cycle at predetermined intervals according to the determination result. duty control means that calculates a valve opening time and opens the first on-off valve for the valve opening time; and a restriction that limits the amount of secondary air flowing through the intake secondary air supply passage when the intake air amount of the engine is low. An intake secondary air supply device comprising means. (2) The limiting means includes a second on-off valve that is provided in the secondary intake air supply passage and closes when the engine intake air amount is low, and a second on-off valve that is provided in the secondary intake air supply passage in parallel with the second on-off valve. Claim 1 characterized in that it consists of a diaphragm.
The intake secondary air supply device described in Section 1.