JPS61207871A - Secondary air supply device for car-mounted internal-combustion engine under deceleration - Google Patents

Abstract

PURPOSE:To purify exhaust of an engine while its combustion condition is prevented from worsening, by supplying secondary air when a car speed of an engine speed, in which the engine combustion condition is relatively stable, is obtained even in low temperature deceleration of the engine. CONSTITUTION:If an engine being in a deceleration condition is discriminated from a change value DELTAPBA of the intake absolute pressure PBA, a supply device supplies secondary air of quantity corresponding to a level of deceleration when a car speed VC is in a predetermined value V1 or more (region B) even with a cooling water temperature in a predetermined value TW1 or more (region A) or TW1 or less. And if a time elapses by a supply time TSH1, valve opening duty ratio gradually decreases from 100%, while if the time elapses by a time TSH2, the valve opening duty ratio reaches 0%. Accordingly, the device, preventing the overrich in the initial time of deceleration while gradually decreasing a quantity of the secondary air also in the latter period of deceleration, enables air-fuel ratio to be controlled in a follow-up state with no large change from the base air-fuel ratio of a carburetor.

Description

TECHNICAL FIELD The present invention relates to an apparatus for supplying secondary air during deceleration of an internal combustion engine.

Background Art Immediately after the internal combustion engine starts to decelerate, the negative pressure in the intake manifold rapidly increases due to the closing of the throttle valve, which causes residual fuel adhering to the inner wall of the intake manifold to vaporize, causing the air-fuel ratio of the supplied air-fuel mixture to exceed. Become rich. Due to this over-rich air-fuel ratio, harmful components such as CO (-carbon oxide) and HC (hydrocarbons) in the exhaust gas increase. A secondary air supply device during deceleration that supplies air to prevent overrich is known (for example, Japanese Patent Publication No. 59
-12845).

In such a secondary air supply device during deceleration, the combustion state of the engine is usually unstable when the engine temperature is low, so the supply of secondary air to the engine has been stopped even during deceleration. However, when the engine decelerates, harmful components in the exhaust gas increase regardless of the engine temperature, so it is desired to improve exhaust purification when the engine decelerates at low temperatures.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a secondary air supply system during deceleration of a vehicle-mounted internal combustion engine, which can purify exhaust while preventing deterioration of the combustion state during engine deceleration at low temperature.

The secondary air supply device during deceleration of the present invention is characterized in that it supplies secondary air to the engine when the vehicle speed is above a predetermined speed or when the engine speed is above a predetermined speed when the engine is being decelerated at low temperature. .

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 7.

In the secondary air supply system during deceleration of a vehicle-mounted internal combustion engine, which is an embodiment of the present invention shown in FIG. 5. The carburetor 3 is provided with a throttle valve 6, and a bench rift 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 its solenoid 9α. On the other hand, numeral 10 is an absolute valve that is provided in the intake manifold 4 and generates an output at a level corresponding to the absolute intake pressure in the intake manifold 4. pressure sensor; 12 is a crank angle sensor that generates a pulse according to the rotation of the crankshaft (not shown) of the engine 5; 12 is a coolant temperature sensor that generates an output at a level corresponding to the coolant temperature of the engine 5; . A catalytic converter 33 is provided in the exhaust manifold 15 of the engine 5 to promote reduction of harmful components in exhaust gas. Solenoid on-off valve9. Absolute pressure sensor 10. The crank angle sensor 11 and the water temperature sensor 12 are connected to a control circuit 20. Also 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 the output levels of the water temperature sensor 12 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 signal output from the multiplexer 22. an A/D converter 23 that converts the signal into a digital signal, a waveform shaping circuit 24 that shapes the waveform of the output signal of the crank angle sensor 11, and a counter that measures the generation interval of the TDC signal output as a pulse from the waveform shaping circuit 24. 25, a drive circuit 28 that drives the electromagnetic on-off valve 9 to open, a CPU (central processing circuit) 29 that performs digital calculations according to programs, R, 0M30, and RAM 31 in which various processing programs and data are written in advance. It consists of Multiplexer 22. A/D converter 23. counter 2
5° drive circuit 28, CPU 29, ROM 30 and R
The AMs 31 are connected to each other by an input/output bus 32.

In such a configuration, the absolute pressure PRAI in the intake manifold 4 is input from the A/D converter 23 to the cooling water temperature TW.

Vehicle speed V. Alternatively, the information representing the engine speed from the counter 25 is transferred to the input/output path 32 of the CPU 29.
are respectively supplied via. CPtJ29 has a predetermined period 'r
An internal interrupt signal is generated every sot (for example, 0.1 sec), and in response to this interrupt signal, an operation to control the secondary air supply during deceleration is performed as described later.

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

The CPU 29 first determines whether a flag FSH for determining secondary air supply during deceleration is equal to "1" each time an interrupt signal is generated (step 51).

I"81 (=O indicates that the initial setting was made when the engine 5 was started, or that the engine 5 was determined not to be in a deceleration state during the previous execution of this routine, so the intake manifold value per unit time. 4, the change value ΔPBA of the absolute pressure PBA is set to the first predetermined value P (for example, -100a
Hg) is determined (step 52).

If ΔPBA<PI, the engine 5 is in a deceleration state,
The cooling water temperature Tw of the engine 5 is set to a predetermined temperature Tw (for example,
70C) or more is determined (step 53
). If 'rw<'I''wt, it is determined whether the vehicle speed ■c is equal to or higher than a predetermined speed ■1 (for example, 17 Kyn/h) (step 54).

If it is determined in step 53 that Tw≧TWI,
Even if it is determined that Tw<Twl, if vc>vl is determined in step 54, the deceleration secondary air supply time TSHI is set (step 55).

I'(0M30 has the supply time T8H1 determined as shown in FIG. 4 for the change value ΔPBA of the absolute pressure PBA written in advance as a TSHl data map, so the CPU 29 calculates the supply time Ta corresponding to the change value ΔPilA.
Search for the old data from the Ts old data map. Next, the deceleration secondary air supply time TsH2 is set (step 56).
. The supply time T'sHs is calculated using the formula TsH2=-T8H1 (K is a constant). When the deceleration secondary air supply time T8H1+Ts+-tz is set in this way, the supply time l1ls old is entered in the internal time counter A (not shown) of the CPU 29, and down counting to the time counter is started ( Step 57), the internal time counter B (not shown) of the CPU 29 is supplied with a time Tso1.
+ Added value of TaH2 (TSHI + TS112)
is set, and time counter B starts counting down (step 58). Then, 1'' representing a deceleration state is set in the flag FSH (step 59), and a valve opening drive command is issued to the !drive circuit 28 (step 60).After that, a subtraction value corresponding to the supply time T8H2 is generated. ■
A is set (step 61), and the opening period 'rou'r of the electromagnetic on-off valve 9 is made equal to the predetermined period Tll0L (
Step 62). Since the subtraction value IA corresponding to each supply time TSH2 is written in the ROM 30 in advance as a 13 data map, the CPU 29 searches the IA data map for the subtraction value I. The subtraction value IA is the supply time TaH2
It is a value for gradually decreasing the valve opening duty ratio of the electromagnetic on-off valve 90 from 100 degrees to 0 degrees in is the second predetermined value P2 (
For example, it is determined whether it is greater than 50 stroke Hg (step 63).

If ΔPnA≦P2, the count of time counter A [TA
It is determined whether or not the value has reached "0" (step 64).
. If the TA key 01, that is, the count value TA has not reached "0", the processing of this routine ends. On the other hand, when the count value TA of the time counter A reaches °On, it is determined whether the count value TB of the time counter B has reached "0" (step 65). Ta'';-0, that is, if the count value TII has not reached 0'', the subtraction value IA is subtracted from the valve opening period T0tlT, and the calculated value is set as the new valve opening period TOUT (step 66). C.P.
The valve opening period 'rou'r is set in the internal time counter C (not shown) of U29, and down counting of the time counter C is started (step 67). and drive circuit 2
A valve opening drive command is generated for 8 (step 68),
It is determined whether the count value Ta of the time counter C has reached "0" (step 69). If the count value Tc has not reached "0", step 69 is executed again. When the count value Ta reaches "0", a valve opening drive stop command is issued to the drive circuit 28 (step 70). If it is determined in step 65 that the count value To has reached "0", the flag FSH is set to "0" (
Step 71) ○In step 63, ΔPnA'>P
! 2, it is assumed that the engine 5 has transitioned from the deceleration state to the acceleration state, and the count value T of the time counter A is
The count values 'I'll of time counter A and time counter B are reset to "0" (steps 72 and 73), and a valve opening drive stop command is issued to the drive circuit 28 (step 74).
0 Then step 71 is executed.

On the other hand, if it is determined in step 51 that FSH=-1, that is, if the deceleration state has already been determined by the processing of this routine up to the previous time, step 63 is executed.

In the secondary air supply device during deceleration according to the present invention, the fact that the engine 5 is in the deceleration state is determined by the intake absolute pressure PBA.
As determined from the change value ΔPBA, when the cooling water temperature Tw is above the predetermined temperature TW1 (region A in Fig. 5), or when the vehicle speed Vc is above the predetermined speed V1 even though the cooling water temperature Tw is below the predetermined temperature TWl. (Area B in Fig. 5), as shown in Fig. 6, the solenoid on-off valve 9 is opened for the supply time Ts according to the change value ΔPIIA and the valve opening duty ratio is 100 inches, and the secondary air is taken in. It is supplied to the engine 5 via the secondary air supply passage 4. That is, an amount of secondary air is supplied in accordance with the magnitude of deceleration. Then, when the supply time T8H1 has elapsed, the valve opening duty ratio gradually decreases from 100 times, and from the time point when the supply time TSH1 has elapsed, the valve opening duty ratio decreases until the time T!
] After time H4 has elapsed, the valve opening duty ratio reaches 0%. Therefore, within the supply time Tsuz, the amount of secondary air supplied gradually decreases and the supply of secondary air is stopped.

The time TSH2 is set according to the change value ΔPBA%, that is, the magnitude of deceleration, and the sudden deceleration is set to be longer, so that the amount of secondary air supplied increases.

Therefore, if secondary air is not supplied to the engine during deceleration, the air-fuel ratio will become overrich as shown by the broken line A in Figure 7, but if secondary air is supplied as described above, the air-fuel ratio will become overrich as shown in Figure 7. As shown by solid line B, overrich at the beginning of deceleration is prevented,
By gradually decreasing the amount of secondary air supplied during the latter half of deceleration, the air-fuel ratio can be made to follow the pace air-fuel ratio of the carburetor without greatly varying.

In addition, in the embodiment of the present invention described above, cooling water m=
During deceleration when Tw is below a predetermined temperature Tw1, secondary air is supplied to the engine when the vehicle speed ■c is above a predetermined speed ■1, but when the engine speed is above a predetermined speed during such deceleration It is also possible to supply secondary air at certain times.0 Effects of the Invention As described above, in the secondary air supply device during deceleration of an in-vehicle internal combustion engine of the present invention, the combustion state of the engine is maintained even when the engine is decelerated at low temperature. When a relatively stable vehicle speed or engine rotational speed is obtained, secondary air is supplied to the engine. Therefore, it is possible to purify the exhaust gas while preventing deterioration of the combustion state when the engine is decelerated at low temperature.

[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. The figure shows the setting characteristics of the deceleration secondary air supply time T81 (1), Figure 5 shows the secondary air supply area during deceleration, and Figures 6 and 7 show the operating state of the device in Figure 1. 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 15-IF air manifold 16...Vehicle speed sensor 33...Catalytic converter

Claims (1)

[Claims] An intake secondary air supply passage communicating with an intake passage downstream of a carburetor throttle valve of an on-vehicle internal combustion engine, a flow rate adjustment valve provided in the intake secondary air supply passage, and an engine in a deceleration state based on predetermined operating parameters. When the engine temperature is above a predetermined temperature when the deceleration state is detected, and when the engine temperature is below a predetermined temperature and the vehicle speed is above a predetermined speed, or when the engine speed is above a predetermined speed. A secondary air supply device during deceleration, comprising: control means for opening the flow rate adjustment valve.