JPH04325708A - Secondary air supplying device for engine - Google Patents

Abstract

PURPOSE:To prevent supercooling of catalyzer when engine speed is decreased after warming up, and prevent deterioration of emission. CONSTITUTION:First and second secondary air supplying passages M1a, M1b supply secondary air upstream of catalyzer of an exhaust gas system of an engine M2. The control valves M3a, M3b of the first and second secondary air supplying passages M1a, M1b are switched according to the operation state of the engine. A catalyzer temperature detecting means M4 detects temperature of the catalyzer. A switching control means M5 opens either of the control valves M3a, M3b of the first and second secondary air supplying passages M1a, M1b when the catalyzer temperature is not more than the predetermined value; and open both of the control valves M3a, Mob of the first and second secondary air supplying passages M1a, M1b when the catalyzer temperature is more than the predetermined value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary air supply system for an internal combustion engine that supplies secondary air to a catalyst through two secondary air supply passages.

0002

2. Description of the Related Art Some internal combustion engines that purify exhaust gas using a three-way catalyst supply secondary air to the exhaust system during warm-up, etc., in order to improve the purification efficiency of the catalyst.

For example, the secondary air supply device described in Japanese Utility Model Application Publication No. 61-116119 has two systems of secondary air supply passages, and when warming up the engine, the two passages are used to supply a large amount of
Secondary air is supplied, and when the engine is idling after warming up, secondary air is supplied through one passage.

0004

[Problems to be Solved by the Invention] In the conventional secondary air supply device, when an idle state occurs due to deceleration after warming up, secondary air is uniformly supplied through one passage regardless of the catalyst temperature. is being carried out. For this reason, if the amount of secondary air supplied through one passage is adjusted to the amount of secondary air required when the catalyst temperature is high, if the catalyst temperature is low when the idle state is reached due to deceleration after warming up. However, there was a problem in that the over-supplied secondary air overcooled the catalyst, worsening emissions.

[0005] The present invention has been made in view of the above points.
If the catalyst is at a low temperature during deceleration after warming up, only one of the two secondary air supply channels will supply secondary air, thereby preventing overcooling of the catalyst and deterioration of emissions. The purpose is to provide a secondary air supply device for an engine.

[0006]

Means for Solving the Problems FIG. 1 shows a diagram of the principle of the present invention.

[0007] First and second secondary air supply paths M1a, M
1b supplies secondary air to the upstream side of the catalyst in the exhaust system of the internal combustion engine M2. first and second secondary air supply paths M1a,
Control valves M3a and M3b of M1b are opened and closed depending on the operating state of the internal combustion engine. Catalyst temperature detection means M4 detects the temperature of the catalyst.

The switching control means M5 compares the temperature of the catalyst with a predetermined value during deceleration after warming up the internal combustion engine, and when the temperature of the catalyst is equal to or lower than the predetermined value, the switching control means M5 switches the first and second secondary air. One of the control valves of the supply passage is opened, and when the temperature of the catalyst exceeds a predetermined value, both of the control valves of the first and second secondary air supply passages are opened.

[0009]

[Operation] In the present invention, when the temperature of the catalyst is lower than a predetermined value during deceleration after warming up, the control valve of one of the secondary air supply paths is opened by the switching control means M5, and a small amount of secondary air is Since the supply is carried out, overcooling of the catalyst is prevented.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows a block diagram of the apparatus of the present invention. This embodiment will be explained using a four-cylinder internal combustion engine as an example. In FIG. 2, an air introduction pipe 10 is supplied with secondary air from an air cleaner.
is branched into two, one having an air suction valve 11a, an air switching valve (ASV) 12a, and an air supply pipe 1.
3a to the exhaust system of the first and fourth cylinders of the engine body 15, and the other is connected to the air suction valve 11b and the ASV
12b, the second air supply pipe of the engine body 15 via the air supply pipe 13b.
, connected to the exhaust system of the third cylinder. ASV12a,
12b are provided with electric negative pressure switching valves (VSV) 16a and 16b, which are supplied with the negative pressure of the intake manifold, and are controlled by a drive signal from the electronic control circuit 30.
When SV16a, 16b opens, ASV12a, 12b
The air suction valves 11a and 11b open and the secondary air from the air supply pipe 10 is supplied to the exhaust system of the engine body 15 through the air supply pipes 13a and 13b. Ru.

[0011] Also, a water temperature sensor detects the cooling water temperature (THW) of the engine body 15, an air flow meter detects the intake air amount Q, a throttle sensor detects the throttle opening, a rotation angle sensor detects the angular position of the predetermined number of cranks, and The detection signal of each vehicle speed sensor that detects the vehicle speed is sent to the ECU3.
0.

The electronic control circuit (ECU) 30 has a configuration shown in FIG. 3, and includes a central processing unit (CPU) 40, a read-only memory (ROM) 41 that stores processing programs, and a random access memory used as a work area. (R.A.
M) 42, a bank-up RAM 43 that retains data even after power is stopped, an A/D converter 44 with a multiplexer function, and an I/O interface 45 with a buffer function, and a bus line 47 is connected between them. are interconnected.

The A/D converter 44 is an air flow meter 31
The air flow rate signal from the water temperature sensor 32, the water temperature signal from the water temperature sensor 32, and the vehicle speed signal from the vehicle speed sensor 33 are supplied and digitized, and these digital signals are sent to the CPU.
40. Further, signals from the throttle sensor 35 and rotation angle sensor 36 are input to the I/O interface 45, and each signal is read by the CPU 40.

[0014] The CPU 40 generates a VSV drive signal based on the detection data of each sensor and outputs the VSV drive signal to the I/O interface 4.
5 to each of the VSVs 16a and 16b.

Next, a control program for an embodiment of the apparatus of the present invention will be explained.

FIG. 4 shows a flowchart of the secondary air supply process. This process is executed, for example, every 34 msec. In FIG. 4, in step 50, it is determined whether the cooling water temperature THW is less than a predetermined cryogenic value A (A is, for example, -25°C), and if the water temperature THW is equal to or higher than the predetermined value A, step 51
It is determined whether the water temperature THW exceeds a predetermined high temperature value B (B is, for example, 40° C.).

When the internal combustion engine is warmed up when the water temperature THW is in the range from predetermined value A to B, it is determined in step 50 whether or not the OTP increase value FOTP is 0, and if it is 0 and OTP increase has not been performed. In step 53, the engine speed NE
is less than a predetermined value C (C is, for example, 5000 rpm). If the rotational speed is less than a predetermined value C and the rotation is high, it is determined in step 54 whether the intake air amount Q is less than a predetermined value D (D is 200 m2, for example), and if the intake air amount is less than the predetermined value D and is large, then , the amount of combustion injection is being increased during warm-up, and a large amount of secondary air is required.
Proceed to step 55 to activate the ASV12a,
VSV16a to open valve 12b and supply secondary air.
, 16b are output.

When the water temperature THW is extremely low in step 50 and is less than the predetermined value A, or when the OTP is increased in step 52, or when the rotational speed NE is high than the predetermined value C in step 53, or when the intake air amount is increased in step 54. If Q is greater than or equal to the predetermined value D, the process proceeds to step 56, where the VSVs 16a and 16 close the ASVs 12a and 12b to stop the supply of secondary air.
Outputs a VSV drive signal that closes both valves b.

After warming up so that the water temperature THW exceeds a predetermined value B in step 51, the process proceeds to step 60, where it is determined whether or not the idle switch output from the throttle sensor 35 is on. determine whether If the idle switch is off and the secondary air supply is not required, or if the vehicle speed is 0 and the secondary air supply is to be stopped for learning control of air-fuel ratio feedback control discrimination, the process proceeds to step 62 and the ASVs 12a and 12b are closed. Both VSVs 16a and 16b are closed so that the valves are closed. Thereafter, in step 63, the ASON flag at idle-on is reset to 0.

When the vehicle speed is not 0 in step 61, that is, when the vehicle is decelerating after warming up, it is determined in step 64 whether the catalyst temperature counter F exceeds a predetermined value E (E is 500° C., for example). If the catalyst temperature counter F exceeds the predetermined value E and the temperature of the three-way catalyst is sufficiently high, a drop in catalyst temperature will not be a problem even if a large amount of secondary air is supplied. VSV16a to open the valve
, 16b is output.

If the catalyst temperature counter F is less than the predetermined value E and the temperature of the three-way catalyst is low, an ASV switching control routine is executed in step 65 to reduce emissions and catalyst exhaust odor, and switch between ASVs 12a and 12b. After opening one of the valves to supply a small amount of secondary air, the ASON flag at idle-on is set to 1 in step 66.

FIG. 5 shows a flowchart of the ASU switching control routine executed in step 65. In step 70, it is determined whether the ASON flag at idle-on is 1, and if this ASON flag is 1, the process is immediately terminated. If the ASON flag is 0, that is, when executing the ASV switching control routine for the first time during deceleration after warming up, step 71 is executed.
It is determined whether the use flag of the ASV 12a is 1 or not. When this usage flag is 1, in step 72 the ASV12
A VSV drive signal is output to open the VSV 16a so as to open the valve a, and the use flag of the ASV 12a is set to 0 in step 73. Also, the use flag of ASV12a is 0.
In this case, in step 74, V is set to open the ASV 12b.
A VSV drive signal is output to open the SV 16b, and the use flag of the ASV 12a is set to 1 in step 75.

FIG. 6 shows a flowchart of the catalyst temperature estimation routine. This routine is executed every 1-2 seconds. In FIG. 6, in step 80, it is determined whether or not the ignition is turned on and the engine is starting. If the engine is starting, the catalyst temperature counter F is set to a predetermined initial value in step 81.

If the engine has been started, the intake air amount Q based on the output signal of the air flow meter 31 is read in step 82, and a correction value is obtained from the map shown in FIG. 7 in step 83. In the map of FIG. 7, correction values -2 to 5 are set corresponding to the intake air amounts Q0 to Q6, respectively. Thereafter, the correction value taken into the catalyst temperature counter F in step 84 is added to obtain a new value of the catalyst temperature counter F.

In this way, when the temperature of the catalyst is lower than the predetermined value E during deceleration after warming up, the A of one of the secondary air supply paths is
Since the SV 12a or 12b is opened and a small amount of secondary air is supplied, overcooling of the catalyst is prevented, and deterioration of emissions in this state can be prevented.

[0026]

As described above, according to the secondary air supply device for an internal combustion engine of the present invention, it is possible to prevent overcooling of the catalyst when the catalyst is at a low temperature, and to prevent deterioration of emissions, which is extremely useful in practice. Useful.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention.

FIG. 2 is a configuration diagram of the device of the present invention.

FIG. 3 is a block diagram of an electronic control circuit.

FIG. 4 is a flowchart of secondary air supply processing.

FIG. 5 is a flowchart of an ASV switching control routine.

FIG. 6 is a flowchart of a catalyst temperature estimation routine.

FIG. 7 is a diagram showing a correction value map.

[Explanation of symbols]

10 Air introduction pipes 11a, 11b Air suction valves 12a, 12
b ASV 13a, 13b Air supply pipe 15 Engine body 30 ECU M1a, M1b Secondary air supply path M2 Internal combustion engine M3a, M3b Control valve M4 Catalyst temperature detection means M5 Switching control means

Claims (1)

[Claims] Claim 1: The exhaust system of an internal combustion engine has first and second secondary air supply passages for supplying secondary air upstream from a catalyst, and the first and second secondary air supply passages are configured to supply secondary air to an upstream side of a catalyst in an exhaust system of an internal combustion engine. A secondary air supply device for an internal combustion engine that opens and closes a control valve for each of the second secondary air supply passages includes a catalyst temperature detection means for detecting the temperature of the catalyst, and a temperature detection means for detecting the temperature of the catalyst during deceleration after warming up the internal combustion engine. is compared with a predetermined value, and when the catalyst temperature is below the predetermined value, either one of the control valves of the first and second secondary air supply passages is opened, and the catalyst temperature exceeds the predetermined value. When the above 1st
and switching control means for opening both of the control valves of the second secondary air supply path.