JPS594527B2 - Secondary air control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to reduce the pressure difference caused by the flow of secondary air between two points in the secondary air supply passage in an automobile internal combustion engine having a secondary air supply passage such as an air pump in the exhaust system. The present invention relates to an improvement of a secondary air control device that maintains the supply amount of secondary air constant by keeping it constant.

When supplying secondary air to the exhaust gas in order to oxidize HC and CO emitted from an internal combustion engine in the exhaust system, the air-fuel ratio generally increases as the amount of intake air increases due to the air-fuel ratio control characteristics of the carburetor. Because it gradually becomes thinner (however,
(excluding during acceleration, high load, high speed, etc.), total CO in exhaust gas
The amount also tends to remain approximately constant regardless of increases or decreases in the amount of intake air, and therefore there is a method of controlling the amount of secondary air to be constant accordingly.

However, when the engine is idling, the exhaust temperature drops significantly due to excessive supply of secondary air, resulting in HC.

Since the CO oxidation efficiency decreases, it is necessary to reduce the amount of secondary air supplied.

As a means for realizing such control, a device as shown in FIG. 1 has been considered.

As a similar one, Ganto Toyama proposed the patent application in 1975.
152780 (Japanese Unexamined Patent Publication No. 52-76520).

Two orifices 34 and 35 are provided in the secondary air supply passage 32 that supplies discharged air from the air pump 31 to the exhaust system with a predetermined interval from each other, and the orifice 34 normally has a pressure P1 before and after. and P2 are A and B of the differential pressure regulator 36, which are separated by a diaphragm 37.
The diaphragm 38 connected to the diaphragm 3T that acts on the pressure chamber 38at38b and responds to this differential pressure opens and closes the atmosphere opening passage 39a, and a negative pressure source (for example, suction negative pressure)
The controlled negative pressure is transmitted to the negative pressure working chamber 40 of the IJ valve 33 via the controlled negative pressure passage 39b, thereby increasing or decreasing the amount of secondary air relief. Feedback control was carried out so that the differential pressure (Pi P2) between the front and rear of 34 was kept constant.

In order to reduce the amount of secondary air when the engine is idling, the B pressure chamber 3 is designed so that the front pressure P1 of the orifice 34 and the rear pressure P3 of the orifice 35 are guided to the differential pressure adjustment device 36.
The passages 41a and 41b connected to the 8b are joined via a switching valve 42, and only when the engine is idling, the switching valve 42 is turned off by a signal from a throttle switch, for example, and the passage 41b side is communicated with the B pressure chamber 38b. I made it.

Here, the areas A1 and A2 of orifices 34 and 35 are AI
> A2, the differential pressure between the two orifices 34 and 35 (Pi-P3) will be smaller than the above (pt P2), and therefore the diaphragm 37 of the differential pressure regulator 36 will be relatively Move to the middle and lower part, atmosphere opening passage 3
In order to increase the dilution rate of negative pressure by the atmosphere by increasing the opening of IJ valve 33, the opening of IJ valve 33 is increased.
J IJ-F amount increases.

As a result, the amount of secondary air supplied to the exhaust system is reduced, and an appropriate amount can be ensured during idle link.

Note that the switching valve 4 interposed in the passage 43 to the A pressure chamber 38a
4 is a switch that is switched at high speed to introduce the atmosphere, strengthen the control negative pressure, reduce the opening degree of the IJ-F valve 33, and increase the amount of secondary air supply. The equipped switching valve 45 operates at high speed and high load, and the IJ
The atmosphere is introduced into the negative pressure working chamber 40 of the IJ-F valve 33,
JIJ-Full valve 33 is fully opened to significantly reduce the amount of secondary air supplied.

Stopping or significantly reducing the supply of secondary air when the engine is at high speeds and under high load is because the exhaust temperature becomes extremely high and the oxidation reaction is excessive due to the supply of secondary air, resulting in the risk of burning out the oxidation catalyst or thermal reactor in the exhaust system. This is because there is.

However, according to this device, the secondary air supply passage 32
Since the two orifices 34 and 35 are provided in the air pump, it is inevitable that the flow path resistance increases, and especially when the air pump rotates at high speed, the flow path resistance becomes extremely large, which may accelerate the deterioration of the air pump. Further, there was a problem that a predetermined flow rate could not be obtained when necessary.

This invention was devised to solve this problem, and the secondary air supply passage is provided with only one orifice, and when the engine is idling, the pressure signal downstream of the orifice is reduced, and the pressure signal on the upstream side is reduced. By increasing the differential pressure with the pressure signal, the IJ IJ-F valve control negative pressure signal is controlled to increase the IJ IJ-F valve opening degree by the front and rear differential pressure adjustment device, and the IJ-IJ-F valve control negative pressure signal is An object of the present invention is to provide a secondary air control device that reduces the supply amount of secondary air to a predetermined state.

The present invention will be described in detail below based on the accompanying drawings.

In FIG. 2, reference numeral 1 indicates a secondary air supply passage connecting the air pump 2 and an exhaust manifold (not shown), and this passage 1 is provided with an IJ valve 3 and a control orifice 4.

Further, this secondary air supply passage 1 is provided with a differential pressure adjustment device 5 (hereinafter referred to as the adjustment device 5) for comparing the passage pressure between the upstream pressure P1 and the downstream pressure P2 of the control orifice 4. The A pressure chamber 7 partitioned off by the diaphragm 6 of the regulating device 5 receives the upstream pressure P1 of the control orifice 4 via the passage 8, and the B pressure chamber 9 receives the downstream pressure P2 of the control orifice 4 via the passage 10. are respectively guided.

An electromagnetic switching valve 11 that responds to a speed switch (not shown) is interposed in the passage 8 that leads the upstream pressure P1 of the control orifice 4 to the A pressure chamber 7 of the adjustment device 5. It turns on when the engine is running at high speed, and the A pressure chamber 7
Atmospheric air is introduced into the air, the diaphragm 6 is raised, the relief valve 3 is fully closed as described later, and the entire amount of air pump discharged is used as the secondary air amount, and the air is supplied through the secondary air supply passage 1. By introducing it into the exhaust gas, it increases the dilution rate of the exhaust gas with secondary air (cold air) and prevents the exhaust gas temperature from rising.

Further, the downstream pressure P2 of the control orifice 4 is in the B pressure chamber 9.
An electromagnetic switching valve 12 that responds to a throttle switch (not shown) and is turned on only when the engine is idling or decelerating is installed in the passage 10 that guides the flow.
2 is switched, the pressure introduction passage 10 on the downstream side of the control orifice 4, which had been in communication only with the B pressure chamber 9, is made to communicate with the atmospheric passage 13 via the orifice 13a, and the downstream pressure P2 of the control orifice 4 is changed. The pressure difference between the A and B pressure chambers 7 and 9 is increased by leaking it to the atmosphere,
The diaphragm 6 of the adjusting device 5 is lowered.

When the diaphragm 6 is lowered, the valve body 14 connected to the diaphragm 6 branches off from the control negative pressure passage 16 that introduces negative pressure from a negative pressure source, for example, engine suction negative pressure, to the negative pressure working chamber 15 of the IJ valve 3. The control negative pressure acting on the negative pressure working chamber 15 is weakened by diluting it with the atmosphere, and the opening degree of the valve body 19 connected to the diaphragm 18 of the relief valve 3 is increased. The second air supply is configured to reduce the amount of air supplied.

In addition, the control negative pressure passage 16 is equipped with an electromagnetic switching valve 20 that responds to the throttle switch and turns on when the engine is running at high speed and under high load when the carburetor secondary valve opens. When the negative pressure passage 16 is closed to the valve body 21
The negative pressure working chamber 1 of the IJ valve 3 is closed by
5, the diaphragm 18 is lowered by the spring 22, the valve body 19 is fully opened, and the entire amount of air pump discharged air is released into the secondary air release passage 23 to stop the supply of secondary air and oxidize the exhaust system. Prevents catalyst or reactor burnout.

Next, this invention will be explained in detail.

In the normal operating range of the engine, the electromagnetic switching valves 11 and 20 are in the positions shown in Figure 2, and the differential pressure across the control orifice 4 (PI P
2), the relief valve 3 acts via the regulating device 5 to keep the amount of secondary air supplied from the air pump 2 substantially constant.

In other words, the secondary air supplied to the engine should be proportional to the amount of intake air, but as mentioned earlier, when matching the carburetor, generally the VF becomes thinner as the amount of intake air increases. Since this setting is made, the total amount of CO discharged is approximately constant regardless of the amount of intake air.

Therefore, it can be seen that a fixed amount of secondary air is required to oxidize this CO.

On the other hand, considering the deterioration of the air pump 2, in the maximum deterioration state, the discharge amount decreases by about 30 factors.

For this reason, in anticipation of this amount, the 30% of the initial discharge amount is
JIJ- If you set it so that the required flow rate can be secured when it is turned off, and supply the full discharge amount when it deteriorates,
You can always secure the required amount.

As a means for this, for example, by keeping the differential pressure across the control orifice 4 constant (PI-P2), 70% of the above discharge amount is supplied to the exhaust system, and the remaining 30 sections are relieved. Even when the exhaust gas is deteriorated, a discharge amount of 100 times the required amount can be supplied to the exhaust system.

This invention basically provides control orifice 4 from this point of view.
The pressure difference (p1P2) between the front and rear sides of the air pump is controlled to be constant, and a constant amount of secondary air supply is ensured in order to cope with the required amount of secondary air during normal operation and the deterioration of the air pump.

To explain in more detail, the secondary air supplied from the air pump 2 depends on the opening degree of the control orifice 4 and the differential pressure (p
t P2), and if the differential pressure P1-P2 is constant, the flow rate will also be constant as long as the orifice opening does not change.

Under normal operating conditions, the upstream pressure P of the control orifice 4,
is introduced into the A pressure chamber 7 of the regulating device 5 via the passage 8, while the downstream pressure P2 is introduced into the B pressure chamber 9 via the passage 10.

Therefore, for example, the differential pressure across the control orifice 4 (PI P2), which increases the pump discharge amount, increases, so the diaphragm 6 moves downward in FIG. is wide open and the atmosphere is introduced into the control negative pressure passage 16, so the suction negative pressure is significantly diluted and weakened by the atmosphere.As a result, the diaphragm 18 of the relief valve 3 is pressed downward by the spring 22, and at the same time Valve body 19 attached to diaphragm 18
The opening degree of IJ increases to increase the amount of IJ-F.

Furthermore, if the pump discharge rate decreases and the differential pressure across the control orifice 4 (Pi P2) decreases, the opening degree of the atmosphere release passage 17 decreases to compensate for this, and the control negative pressure decreases. Since the atmospheric dilution rate is weakened and a strong negative pressure acts on the IJ valve 3, the opening degree of the valve body 19 is reduced and the IJ valve amount is reduced.

In other words, the IJ is adjusted so that the differential pressure across the orifice remains constant.
The negative pressure signal to the IJ valve 3 is adjusted.

As a result, the differential pressure across the orifice (Pl-P2) is constant, so the amount of secondary air is also constant.

For this reason, even if the air pump 2 deteriorates as described above and the discharge pressure of the secondary air decreases, and the differential pressure across the control orifice 4 (Pi-, p2) decreases, there is no way to deal with this. Since the opening degree of the relief valve 3 becomes smaller and the amount of secondary air is reduced, the supply ratio from the air pump 2 to the secondary air supply passage 1 side increases, and therefore the deterioration of the air pump 2 is reduced. (approximately 30 sections) can be supplemented.

Next, when the required amount of secondary air is small, such as when the engine is idling or decelerating, the solenoid switching valve 12 is switched, that is, turned on, by the throttle switch (not shown), and the B pressure chamber 9 of the regulating device 5 is turned on. and control orifice 4
The passage 10, which previously communicated only with the downstream side of the air, is simultaneously communicated with the atmosphere via the orifice 13a.

In this way, by leaking the downstream pressure P2 to the atmosphere, the pressure difference between the A pressure chamber 7 and the B pressure chamber 9 (PI-P
2) Increase.

(In addition to the throttle switch, it is also possible to use an intake negative pressure detection switch, an accelerator switch, etc. as a detection device for idling, etc.)

) Generally, the atmospheric pressure is lower than the downstream pressure P2 of the control orifice 4, so the downstream pressure P2 diluted with the atmosphere also becomes lower, so the diaphragm 6 moves relatively downward by being pressed by the orifice upstream pressure P1. , valve body 14
The degree of opening with respect to the atmosphere opening passage 17 increases relatively.

Therefore, the opening degree of the IJ-F valve 3 increases due to the decrease in the controlled negative pressure, the IJ-IJ-F amount increases, and the supply amount of the secondary air amount decreases.

Even in this case, the signal pressure of the orifice upstream pressure P1 and the orifice downstream pressure P2 weakened by the atmosphere is acting on the differential pressure adjustment device 5, so the absolute value of the differential pressure across the orifice 4 becomes small. , control to keep this constant is continued, and therefore a small but stable amount of secondary air can be ensured even during idling.

During idling or deceleration, the exhaust temperature decreases due to excessive supply of secondary air and the oxidation efficiency of HC and CO deteriorates, but this can be prevented by reducing the amount of secondary air supplied. Can be done.

Also, when the secondary valve of the carburetor opens at high speed and under high load, the electromagnetic switching valve 20 is turned on and the atmosphere is introduced into the negative pressure working chamber 15 of the IJ-F valve 3, and the diaphragm 18 is pushed down by the spring 22 and the valve body 19 is pressed down. Fully open,
Stopping the supply of secondary air prevents burnout of the oxidation catalyst or reactor in the exhaust system due to a rise in exhaust temperature.By the way, at high speeds and high loads when the secondary valve of the carburetor opens, the intake mixture becomes concentrated, so a large amount of If secondary air is supplied, re-combustion in the exhaust system becomes too active.

However, when the engine is operating at high speed, the electromagnetic switching valve 11 is turned on by the speed switch, and the atmospheric air is introduced into the A pressure chamber 7 of the regulating device 5 to reduce the pressure in the A pressure chamber 7, thereby raising the diaphragm 6 and causing the diaphragm 6 to rise. The opening degree of the atmosphere opening passage 17 is reduced by the valve body 14 connected to the valve body 6 .

Then, a strong controlled negative pressure is applied in the negative pressure working chamber 15 to
The J IJ valve 3 is fully opened to introduce the entire amount of air pump discharged air as secondary air, thereby increasing the dilution rate of the exhaust gas with the cold secondary air and preventing a rise in exhaust gas temperature.

By the way, when the engine is operating at high speeds and medium to low loads, the intake air-fuel mixture is kept lean for fuel efficiency reasons, so even if a large amount of secondary air is supplied, re-combustion will not become excessive.

As described above, according to the present invention, the passage resistance can be reduced by using one orifice in the secondary air supply passage, so that the air pump does not deteriorate or the secondary air supply is insufficient, and moreover, it can be adjusted according to the operating conditions. The effect of supplying appropriate secondary air can be expected.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a conventional device, and FIG. 2 is a schematic configuration diagram of the present invention. 1...Secondary air supply passage, 2...Air pump, meter...Relief valve, 4...
Control orifice, 5... Front and rear differential pressure adjustment device, 6
...Diaphragm, 7...A pressure chamber,
8...Passage, 9...B pressure chamber, 10.
...Passage, 11...Solenoid valve, 12...
... Solenoid switching valve, 13a ... Orifice, 1
4... Valve body, 15... Negative pressure working chamber, 1
6...Control negative pressure passage, 17...Atmospheric release passage, 18...Diaphragm 19...
・Valve body, 20... Solenoid switching valve, 21...
・Valve body, 22...Spring, 23...
・Secondary air release passage.

Claims (1)

[Claims] 1. A relief valve and an orifice that regulates the flow rate are provided in the secondary air supply passage connected to the exhaust system, and differential pressure adjustment is performed to control the operating negative pressure of the IJ (L) in response to the differential pressure between the front and rear of the orifice. A device is installed to feedback control the opening degree of the IJ-F valve so that the differential pressure across the orifice remains constant, while also allowing the pressure signal downstream of the orifice that is led to the A pressure adjustment device to leak to the atmosphere via the switching valve. A secondary air control device configured to operate the switching valve when the engine is idling to weaken the orifice 1 flow pressure signal and reduce the secondary air supply amount.