JPS5849686B2 - Secondary air control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an internal combustion engine for automobiles having a secondary air supply device in the exhaust system, by appropriately changing the opening degree of a regulating valve provided in a secondary air passage in accordance with operating conditions. The present invention relates to a secondary air control device that controls the increase/decrease of the supply amount of secondary air.

In order to treat H0.00 emitted from an internal combustion engine in the exhaust system, a device is known that supplies secondary air into the exhaust gas. There is a device that controls the amount of secondary air supplied by adjusting the opening degree of the IJ valve installed in the secondary air passage using C negative pressure or carburetor venturi negative pressure. No. 70728, U.S. Patent No. 3
85967, etc.).

However, with these control means, it is difficult to supply an appropriate amount of secondary air depending on the operating conditions due to the effects of changes in the rotational speed of the air pump, deterioration of the air pump, etc. resulting in insufficient air supply and therefore effective HC. There was a drawback that it was not possible to reduce the number of 00.

This invention was devised to solve the above problems, and maintains the differential pressure across the orifice provided in the secondary air passage constant, and maintains the amount of secondary air at a constant amount under normal conditions. It is an object of the present invention to provide a secondary air control device that increases the amount of secondary air by expanding the opening degree of the orifice via a regulating valve when the engine accelerates.

The present invention will be explained below based on the accompanying drawings.

Reference numeral 1 indicates a secondary air supply passage connecting the air pump 2 and an exhaust manifold (not shown), and this passage 1 includes a relief valve 3, a control orifice 4 downstream thereof, and a fixed orifice and A flow rate regulating valve device 5 is provided to perform both functions of the variable orifice.

Further, in the secondary air supply passage 1, there is a differential pressure adjustment device 6 for comparing the passage pressures upstream and downstream of the control orifice 4.
(Hereinafter referred to as the adjustment device 6.

), the pressure chamber 8 partitioned off by the diaphragm I of the regulating device 6 receives the upstream pressure P1 of the control orifice 4 via the passage 9, and the pressure chamber 10 receives the control pressure via the passage 11. A downstream pressure P2 of the orifice 4 is respectively introduced.

An electromagnetic switching valve 12 that responds to a throttle switch (not shown) is interposed in the middle of the passage 11, and the solenoid 12' is energized to switch the valve body 12 during low and high engine loads.
By moving " to the left in the figure, the passage 11 is blocked and the pressure chamber 10 is released to the air.

Further, a valve body 13 connected to a diaphragm 7 of the adjustment device 6 branches from a control negative pressure passage 15 that leads the engine suction negative pressure P to the negative pressure working chamber 14 of the IJ valve 3 in response to the diaphragm 7. The atmosphere opening hole 15b communicating with the passage 15a is opened and closed.

Further, the IJ valve 3 controls the opening degree of the IJ valve 16 communicating with the secondary air supply passage 1 in accordance with the negative feeding pressure.

A flow rate regulating valve device 5 (hereinafter referred to as valve device 5) provided near the control orifice 4.

), a valve body 17 located within the control orifice 4 is directly connected to a diaphragm 18, and a negative pressure working chamber 19 is defined by the diaphragm 18.

An engine suction negative pressure P is introduced into the negative pressure working chamber 19, whereby the valve body 17 moves forward and backward with respect to the control orifice 4 according to the engine operating state, thereby adjusting its opening degree.

That is, the valve body 1T has a cylindrical portion 17' and a tapered portion 17.
", and only the cylindrical portion 17' has the control orifice 4.
When located inside the orifice, both function as a fixed orifice.

However, when the tapered portion 17'' enters inside the control orifice and moves away from the control orifice as shown by the dotted line, both act as variable orifices.

Next, the operation of this invention will be explained.

In the normal operating range of the engine, the control orifice 4 and the valve body 17
functions as a fixed orifice, and the differential pressure between the front and rear (P, -P
2), the relief valve 3 is operated via the regulating device 6 to keep the amount of secondary air supplied from the air pump 2 substantially constant.

In other words, the secondary air required by the engine should be proportional to the amount of intake air, but in general, the A/F becomes thinner as the amount of intake air increases until the power range or secondary side works due to carburetor matching. Since the oxidation reaction temperature of the exhaust gas is set to be approximately constant, the total amount of CO discharged is approximately constant regardless of the amount of intake air.

Therefore, it can be seen that a constant amount of secondary air is required to oxidize this CO, regardless of changes in the amount of intake air.

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

For this reason, approximately 70% of the initial discharge amount is effectively utilized in anticipation of this amount in advance.

As a method of utilizing this, for example, by keeping the differential pressure (P1-P2) between the front and rear of the control orifice 4 constant, the above 70%
The remaining 30% is supplied to the exhaust system.
By relieving the air, even when the air pump 2 deteriorates, it is possible to supply 100% of the required amount to the exhaust system.

From this point of view, the present invention deals with the deterioration of the air pump and always maintains the differential pressure across the control orifice 4 (P1P2
) can be controlled at a constant level, and a constant amount of secondary air can always be supplied.

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 (
P1-P2), and the differential pressure (PI-p2
) is constant, the flow rate will also be constant as long as the orifice opening does not change.

That is, in normal operating conditions, the upstream pressure P1 of the control orifice 4 is led via the passage 9 into the pressure chamber 8 of the regulating device 6, while the downstream pressure P2 is introduced via the passage 11 into the pressure chamber 10. .

Therefore, for example, when the pump discharge rate increases, the differential pressure (P1-P2) across the control orifice 4 increases, so the diaphragm 7 moves downward in the figure, and accordingly, the valve body 13
Since the air opening passage 15b is wide open and the dog air E is guided to the control negative pressure passage 15, the suction negative pressure P is significantly diluted by the atmosphere and weakened.

As a result, the diaphragm 20 of the IJ valve 3 is pressed downward by the spring 21, and at the same time, the opening degree of the valve body 22 integrally connected to the diaphragm 20 increases, increasing the IJ valve amount.

Further, when the pump discharge amount decreases and the differential pressure across the orifice 4 (PI-P2) decreases, the opening degree of the atmosphere release passage 15b decreases, contrary to the above, to compensate for this.
Since the atmospheric dilution rate of the controlled negative pressure is weakened and a strong negative pressure acts on the IJ valve 3, the opening degree of the valve body 22 is reduced and the IJ valve amount is reduced.

In other words, the magnitude of the control negative pressure to the IJ valve 3 is adjusted so that the differential pressure across the orifice becomes constant.

As a result, since the differential pressure across the orifice (P, -P2) is constant, the amount of secondary air supplied to the exhaust system is also constant.

This also means that even if the air pump 2 deteriorates as described above and the discharge pressure of the secondary air decreases, the differential pressure (P1-P2) across the control orifice 4 decreases accordingly, causing the IJ
The opening degree of the IJ-F valve 3 becomes smaller and the secondary air I
Since the amount of J IJ-F is reduced, the proportion of the total discharge amount from the air pump 2 that is supplied to the exhaust system increases, and therefore deterioration of the air pump 2 can be compensated for.

From this state, when the engine accelerates and the suction negative pressure P decreases, the valve body 17 of the valve device 5, which responds to this suction negative pressure, moves to the position shown by the dotted line in FIG. 4. Increase the opening area.

In other words, as the suction negative pressure decreases, the diaphragm 18 is pressed by the spring 23, and the valve body 17 moves from inside the control orifice 4 to the left in the figure, increasing the opening degree of the flow path.

Even in this case, the opening degree of the IJ-F valve 3 is automatically reduced by the feedback control as described above, and the differential pressure across the valve body 17 (p+P2) is kept constant, so that the secondary air supply amount is increases as the opening degree of the control orifice 4 increases.

When the engine is accelerating, the supply of power fuel generally enriches the air-fuel mixture and creates HC. CO increases rapidly, but by increasing secondary air accordingly, these HC-00 can be effectively reburned.

Incidentally, as shown in FIG. 2, instead of the suction negative pressure introduced into the valve device 5, a negative pressure near the carburetor throttle valve, that is, a C negative pressure may be applied.

However, when the engine accelerates, generally the negative pressure increases, so the operating direction of the valve body 17a is reversed compared to the case of suction negative pressure.

Next, when the required amount of secondary air is small, such as when the engine is idling, the throttle switch (not shown) operates the electromagnetic switch and the valve 12 switches (by moving the valve body 12'' to the left in the figure). The downstream pressure P2 is cut off) and the dog air E is introduced into the pressure chamber 10.

Since the atmospheric pressure is generally lower than the control orifice downstream pressure P2, the diaphragm 7 is pressed downward by the orifice upstream pressure P1, and the degree of opening of the valve body 13 with respect to the atmosphere opening passage 15b increases relatively.

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

However, even in this operating range, if the operation of the air pump 2 is insufficient and the discharge amount decreases below the set value, the upstream pressure P1
As a result, the diaphragm 7 moves upward, increasing the control negative pressure, reducing the relief amount and ensuring a predetermined amount of secondary air.

Further, this electromagnetic switching valve 12 operates based on the throttle switch even when the engine is at high speed and under high load, and similarly
Increase the amount of IJ-F to decrease the amount of secondary air supplied.

When idling, etc., the exhaust temperature decreases due to excessive supply of secondary air, causing HO. C! The oxidation catalyst or reactor in the exhaust system may burn out due to the exhaust temperature rising due to the supply of secondary air at high speeds and high loads. This inconvenience is prevented by reducing the amount of air.

As described above, this invention provides a flow rate adjustment valve device in the secondary air supply passage to supply a substantially constant amount of secondary air during normal operation, but increases the amount of secondary air appropriately when the engine accelerates. This has the effect of reliably reducing I-{0.00, which tends to increase when the engine accelerates.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the general structure of this invention, and Figure 2 is an explanatory diagram showing the general structure of this invention.
It is an explanatory view showing other examples of a flow rate adjustment valve device. 1... Secondary air supply passage, 2... Air pump, 3... Relief valve, 4...
・Control orifice, 5... Flow rate adjustment valve device, 6... Front and rear differential pressure adjustment device, I... Diaphragm, 8... Pressure chamber, 9. ... Passage, 10... Pressure chamber, 11... Passage,
12... Solenoid switching valve, 13... Valve body,
14... Negative pressure working chamber, 15... Control negative pressure passage, 15a... Branch passage, 15b...
... Atmospheric release passage, 16... IJ IJ-fu passage, 17... Valve body, 18... Diaphragm, 19... Negative pressure working chamber, 20...
...Diaphragm, 21...Spring, 2
2... Valve body, 23... Spring, P1
...Upstream pressure, P2...Downstream pressure, P
... Engine suction negative pressure, VC ... Negative pressure near the throttle valve.

Claims (1)

[Claims] 1. IJ in the secondary air supply passage by the air pump of the engine.
In a secondary air supply device that is equipped with an IJ-F valve and a differential pressure adjustment device before and after an orifice to adjust the amount of secondary air to a nearly constant level, an adjustment valve that narrows this passage is provided, and the adjustment device controls the pressure of the adjustment valve. The control negative pressure of the IJ IJ-F valve is adjusted in response to the pressure difference across the front and back, and the opening degree of the relief valve is feedback-controlled so as to keep the pressure difference between the front and rear of the adjustment valve constant. A secondary air control device, characterized in that the secondary air control device functions as a fixed orifice, while increasing the opening degree of the adjustment valve when the engine accelerates to increase the amount of secondary air. 2. The secondary system according to claim 1, characterized in that engine suction negative pressure is applied to the adjustment valve, and when the suction negative pressure decreases during engine acceleration, the opening degree of the adjustment valve is increased. Air control device. 3. A negative pressure generated near the throttle valve of the carburetor is applied to the regulating valve, and when this negative pressure increases during engine acceleration, the opening degree of the regulating valve is increased. A secondary air control device according to scope 1.