JPS61187548A - Control method of opening/closing valve for adjusting mixed gas for internal-combustion engine - Google Patents

Abstract

PURPOSE:To eliminate the erroneous detection for trouble by a trouble detecting means by closing an opening/closing valve for controlling the air-fuel ratio of mixed gas in each duty cycle and calculating the valve closing time of the opening/closing valve for the duty cycle and opening the opening/closing valve after the lapse of the valve closing time. CONSTITUTION:An intake manifold 4 on the downstream side of the throttle valve 6 of a carburetor 3 and the vicinity of the air discharge port of an air cleaner 2 are allowed to communicate through a secondary intake air feeding passage 8, and an electromagnetic opening/closing valve 9 is installed into said passage 8. The air-fuel ratio of the mixed gas is controlled by electric-conduction-controlling the solenoid 9a of the electromagnetic opening/closing valve 9 according to the duty ratio on the basis of the operation parameter of an engine by a control circuit 20. In this case, the opening/closing valve 9 is closed from the control starting time-point in each duty cycle, and the valve closing period of the opening/closing valve 9 for the duty cycle is calculated on the basis of the result of the detection of the operation parame ter, and the opening/closing valve 9 is opened after the lapse of the calculated valve closing period.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a method for controlling an on-off valve for adjusting air-fuel mixture in an internal combustion engine.

1L[] For the purpose of purifying the exhaust gas of internal combustion engines and improving 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 adjusted according to the output level of this oxygen concentration sensor. Air-fuel ratio control devices that perform feedback control are known. As this air-fuel ratio control device, an on-off valve is installed in the intake secondary air supply passage that communicates downstream of the carburetor throttle valve, and the opening and closing of the on-off valve, that is, the intake secondary air supply, is controlled in accordance with the output level of the oxygen concentration sensor. There is a feedback control intake secondary air supply system (for example, Japanese Patent Publication No. 55-3533).

In such a conventional intake secondary air supply device, 1
The opening/closing duty ratio of the opening/closing valve is calculated for each duty period according to the engine operating parameters, and as soon as the calculation is completed, the valve is opened for a period according to the duty ratio. It is taken. In such a control method, when the duty ratio reaches a value close to 100%, a state occurs in which the on-off valve is opened even during the calculation of the duty ratio in the next duty cycle, and in some cases, the on-off valve is opened. The valve open state is continued by opening the valve after completing the new duty ratio calculation. However, if a failure detection means is provided to determine the failure of the on-off valve from the opening/closing operation within one duty cycle of the on-off valve, the open state of the on-off valve will remain open until the next duty cycle as described above. If this continues, it will be judged as a malfunction, which is inconvenient.

11 animals 1L Therefore, the purpose of the present invention is to ensure that the calculated duty ratio is 10
It is an object of the present invention to provide a control method for an on-off valve for air-fuel mixture adjustment, which can prevent the on-off valve from being deemed to be in failure by a failure detection means even if it is 0%.

The on-off valve control method for air-fuel mixture adjustment of the present invention closes the on-off valve from the start of control in each duty cycle, detects operating parameters, and determines the closing period of the on-off valve within the duty cycle based on the detection results. It is characterized in that the on-off valve is opened when the calculated valve closing period has elapsed.

1M J Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a secondary intake air supply system for an on-vehicle internal combustion engine to which the control method according to the present invention is applied. In this device, 1, intake air is supplied to the engine 5 from an atmospheric air intake port 1 via an air cleaner 2, a carburetor 3, and an intake manifold 4. The carburetor 3 is provided with a throttle valve 6, 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 . The electromagnetic on-off valve 9 is opened by energizing the solenoid 9a.

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 accordance with 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 a lean sensor installed in the exhaust manifold 15 of the engine 5 that generates an output proportional to the oxygen concentration in the exhaust gas. It is an oxygen concentration sensor. As shown in FIG. 2, the oxygen concentration sensor 14 has a characteristic that the output level increases proportionally as the air-fuel ratio of the air-fuel mixture supplied to the engine 5 becomes leaner than the stoichiometric air-fuel ratio (14,7>. A catalytic converter 33 is provided in the exhaust manifold 15 downstream of the concentration sensor 14 in order to promote reduction of harmful components in the exhaust gas.

Electromagnetic on-off valve 9, absolute pressure sensor 10, crank angle sensor 1
1. The water temperature sensor 12 and the 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.

The control circuit 20 includes an absolute pressure sensor 101 as shown in FIG.
Water temperature sensor 12, oxygen concentration sensor 14, and vehicle speed sensor 1
6, a multiplexer 22 that selectively outputs one of the sensor outputs that have passed through the level conversion circuit 21;
A/2 converts the signal output from 2 into a digital signal.
A D converter 23, a waveform shaping circuit 24 that shapes the waveform of 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 opening/closing valve 9. A spinning circuit 28 that drives the valve opening, two CPUs (central processing circuits) that perform digital calculations according to programs, a ROM 30 in which various processing programs and data are written in advance, and a RAM.
It consists of 31. Multiplexer 22, A/D converter 23, counter 25, drive circuit 28, CPU 29,
ROM30 and RAM31 are connected to each other by an input/output bus 32.

In this configuration, the A/D converter 23 selectively provides information on the absolute pressure in the intake manifold 4, the cooling water temperature, the oxygen concentration in the exhaust gas, and the vehicle speed, and the counter 25 provides information representing the engine speed. CI) U 29 are each supplied via a manned saw bus 32. The CPU 29 is configured to generate an internal interrupt signal every one duty cycle TsOL (for example, 100 m5ec), and in response to this interrupt signal, the CPU 29 generates an internal interrupt signal for duty-controlling the intake secondary air supply as described later. Perform the action.

Next, the operation of the intake secondary air supply device will be explained according to the operation flowchart of the CPU 29 shown in FIGS. 4 and 5.

In the CPU 29, first, a valve opening drive stop command is issued to the drive circuit 28 to close the electromagnetic on-off valve 9 every time an interrupt signal is generated (step 51). This is a CPU
This is to prevent malfunction of the electromagnetic on-off valve 9 during the calculation operation of step 29. Next, Den! ! The closing period TAF of the on-off valve 9 is 1
is made equal to the duty period TSOL (step 52).
Then, the A/F routine shown in FIG. 5 is executed to calculate the opening period TOLJT of the electric power 1 on-off valve 9 (step 53).

In the A/F routine, first, the operating state of the vehicle (including the operating state of the engine) is determined by air-fuel ratio feedback (F/B).
It is determined whether the control conditions are satisfied (step 531). This determination is determined from the absolute pressure in the intake manifold, cooling water temperature, vehicle speed, and engine rotation speed. 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, the valve opening period TO is set to stop the air-fuel ratio feedback control.
LJT is set to "o" (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 reference duty ratio of the opening of the open valve 9 of the electric power 11 (
DBA sE is set (step 533)
. As shown in FIG. 6, the reference duty ratio DBASε, which is 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. Read the rotation speed Ne and set the standard duty control Da A sE corresponding to each read value.
Search from the 8ASE data map. Next, the CPU
It is determined whether or not a predetermined time Δtl has elapsed from the count time of the internal timer counter A (not shown) of No. 29 (step 534).

During the predetermined time Δt1, the intake secondary air is supplied, and the result is detected as a change in the oxygen concentration in the exhaust gas by the oxygen concentration sensor 1.
4 corresponds to the response delay time until detection.

When a predetermined time Δt1 has elapsed since the time counter A was set and started counting, time counter A is reset and counting starts from the initial value (step 535). That is, after the time counter A starts counting from the initial value by executing step 535, it is determined in step 5 whether or not the predetermined time Δ has reached 1.
This was done in 34.

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 536). To set this target air-fuel ratio, the ROM 30 stores a reference level l ref corresponding to the target air-fuel ratio determined from the intake manifold absolute pressure PBA and the engine speed Ne as a Δ/F data map, similar to the DBASE data map. A
It is written in advance separately from the SE data map.

Therefore, the CPU 29 calculates the absolute pressure PBA and the engine speed N.
The reference level L ref corresponding to o is searched from the A/F data map. Next, it is determined from the oxygen a1 degree information whether the output level LO2 of the oxygen concentration sensor 14 is greater than the reference level 1rer determined in step 536 (step 537).

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. L
If oz>Lref, the air-fuel ratio is leaner than the target air-fuel ratio, so a subtraction value I L is calculated (step 53
8). The subtraction value IL is calculated by multiplying the constant by 1, the engine speed Ne and the absolute pressure PBA by IQ(K+ -1'tle-
PeA), and depends on the intake air amount of the engine 5. After calculating the subtraction value IL,
By executing this A/F routine, the already calculated correction value 1outT is read from the memory location al of the RAM 31, the subtraction value IL is subtracted from the read correction value 10LJT, and the calculated value becomes the new correction value. 10UT and written to storage location a1 of the RAM 31 (step 539). On the other hand, in step 537, LO2≦l
If it is rer, the air-fuel ratio is higher than the target air-fuel ratio, so an additional value IR is calculated (step 5310). The additional value IR is calculated by multiplying the constant by 2 (≠KI), the engine speed Ne and the absolute pressure PaA (K2 ・Ke-PeA
), and is made to depend on the intake air pressure of the engine 5. After calculating the additional value IR, A/F
Correction value 10 already calculated by executing the routine
LJT is read from the storage location a1 of the RAM 31, an additional value JR is added to the read correction value 10LIT, and the calculated value is set as a new correction ItJIoUT and is stored in the RAM 31.
31 storage location a1 (step 5311
). In this way, the correction value l0UT is set at step 539 or 53.
11, the correction value four and the reference duty ratio DI3 set in step 533
ASε is added and the addition result is the valve opening time Tout
(Step 5312).

Note that after the time counter A is reset in step 535 and starts counting from the initial value, the predetermined Rr
If it is determined in step 534 that fIJΔj+ has not elapsed, step 5312 is immediately executed, and in this case, the correction value 1o LJ T lfi obtained by the previous execution of Δ/F routine is read out.

When the execution of A/F Routine is completed, r is calculated by subtracting the valve opening time TOUT from 1 duty period TSOL.
An time TAF is determined (step 54). next,
A value corresponding to the valve closing time TAF is set in an 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 counted value of time counter B has reached "0" (step 56), and if the counted value of time counter B has reached "0", the valve is opened to the drive circuit 28. A drive command is generated (step 57).

During this time, the drive circuit 28 operates the electromagnetic on-off valve 9 in response to the valve drive command.
The valve is driven to open, and this valve-opening state continues until step 51 is executed next. If the count value of time counter B does not reach 0'' in step 56, step 56 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, as shown in FIG. Supply is cut off. Also, the closing time TAF of the electromagnetic nl3JJ valve 9 in one duty cycle TSOL
is calculated and the valve closing time TAF has elapsed since the interrupt signal was generated, the electromagnetic 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. By controlling the intake secondary air in this manner, the air-fuel ratio of the air-fuel mixture supplied to the engine 5 is controlled to the target air-fuel ratio.

In the intake secondary air supply device to which the on-off valve control method according to the present invention is applied, the electromagnetic on-off valve 9 is first closed every time an interrupt signal is generated. This prevents the air-fuel ratio of the supplied air-fuel mixture from becoming over-lean when the engine is under low load. In other words, conventionally, when the engine load is low and the duty ratio is 100% and the on-off valve remains open until the next duty cycle, the negative pressure inside the intake manifold increases and the intake secondary air Large [l
However, even if the valve opening duty ratio calculated by applying the control method of the present invention is 100%, the actual valve opening/closing duty ratio is slightly smaller than 100%. Since the valve is opened, overlean is prevented. In particular, when the target air-fuel ratio is set in the lean region as in the above embodiment, the target air-fuel ratio at low loads is set leaner than at medium-high loads, so the air-fuel ratio of the supplied air-fuel mixture tends to become over-lean. but,
Since the controlled air-fuel ratio can be moved slightly to the rich side, overlean can be prevented and drivability under low load can be improved.

In the embodiment of the present invention described above, the on-off valve is provided in the intake secondary air supply passage to control the amount of intake secondary air, but the on-off valve is not limited to this. It can also be applied to the case where it is provided in a fuel supply passage to control the fuel tank.

In addition, in the embodiment of the present invention described above, the time counter B is built in the CPU 29, but if the time counter B is provided outside the CPU 29 and the count value of the time counter B reaches II OII, the time counter B is Counter B
It is also possible to supply the valve opening drive command to the drive circuit 28 from the valve opening drive command.

1 ri! As described above, in the mixture adjustment on-off valve control method for an internal combustion engine of the present invention, the on-off valve is first forcibly closed in each duty cycle, and the closing period of the on-off valve within the duty cycle is As soon as the calculated valve closing period has passed, the on-off valve is opened, so even if the valve closing period is calculated to be Ol, that is, the valve opening duty ratio is 100%, the open state of the on-off valve will be the same as the next duty cycle. It does not occur that it continues until the end. Therefore, even if a failure detection means is provided to determine the failure of the on-off valve from the opening/closing operation within one duty period of the on-off valve, as long as the on-off valve is normally controlled, it will not be possible to make incorrect failure determinations as in the past. It can be prevented.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram (not showing) of an intake secondary air supply device to which the control method according to the present invention is applied, FIG. 2 is a diagram (not showing) the output characteristics of the oxygen concentration sensor in the device of FIG. 1, and FIG. Figure 1 is a block diagram showing the specific configuration of the control circuit in the device, Figures 4 and 5 are flow diagrams that do not show the operation of the CPU, and Figure 6 is a flow diagram showing the RO
Figure 7 shows the data map written in M.
FIG. 3 is a diagram showing the operation timing of the device shown in the figure. 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 ...Solenoid on-off valve 10 ...Absolute pressure sensor 11 ...Crank angle sensor 12 ...Cooling Water temperature sensor 14...Oxygen concentration sensor 15...Exhaust manifold 33...Catalytic converter Applicant Honda Motor Co., Ltd. Agent Patent attorney Motohiko Fujimura Chiku 1 Figure 2 147 18! ! WE Figure 6 r, p, m. Figure 7

Claims (3)

[Claims] (1) A method of controlling the opening and closing of an on-off valve provided to adjust the air-fuel mixture supplied to an internal combustion engine using a duty ratio based on engine operating parameters, the method comprising: Close the on-off valve, detect the operating parameters, calculate the closing period of the on-off valve within the duty cycle based on the detection result, and open the on-off valve when the calculated closing period has elapsed. A control method characterized by closing a valve. (2) the on-off valve is provided in a secondary intake air supply passage communicating downstream of the carburetor throttle valve of the internal combustion engine;
2. The control method according to claim 1, wherein the operating parameter is an oxygen concentration in exhaust gas detected by an oxygen concentration sensor provided in an exhaust system. (3) The oxygen concentration sensor generates an output proportional to the oxygen concentration in the exhaust gas when the air-fuel ratio of the air-fuel mixture supplied to the engine is at least leaner than the stoichiometric air-fuel ratio. Control method according to item 2.