JPS6030457Y2 - Engine high altitude correction device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a high altitude correction device for an engine equipped with an exhaust gas recirculation device.

Generally, when the air-fuel ratio of the air-fuel mixture supplied to the engine is slightly leaner than the stoichiometric air-fuel ratio (approximately 14.6), the fuel consumption rate is the lowest, but on the other hand, nitrogen oxides N in the exhaust gas
The largest amount of Ox is discharged at this time.

Therefore, in an engine equipped with an exhaust gas recirculation device (hereinafter simply referred to as an EGR device), the air-fuel ratio is adjusted to improve both the fuel efficiency of the engine and the reduction of nitrogen oxides (NOx) in the exhaust gas. This is dealt with by setting the air-fuel ratio to be slightly thinner than the stoichiometric air-fuel ratio and increasing the amount of EGR.

By the way, if you set the fuel as above at a low altitude, when you drive at a high altitude, the air density decreases as the atmospheric pressure decreases, so the air-fuel ratio becomes richer, and the negative intake pressure increases as the atmospheric pressure decreases. As the air pressure approaches and the intake air filling volume decreases,
In order to obtain the same output as at low altitudes, a greater amount of pedal depression is required than at low altitudes, giving the driver a feeling of lower output.

The former (enrichment of the air-fuel ratio) can be dealt with by supplying correction air to the intake passage below the venturi of the carburetor, but the latter (insufficient output) cannot be completely dealt with by this correction air alone.

In other words, since the former (enrichment of the air-fuel ratio) occurs under the latter (decrease in the intake charge amount), the amount of air for correction of the charge amount is more important than the amount of air for the correction of the air-fuel ratio. This is because they require far more.

Therefore, if the corrected air amount is set for the purpose of correcting the filling amount, the air-fuel ratio will become even thinner than the air-fuel ratio set at low altitudes, making operation impossible. Filling amount correction becomes insufficient.

Therefore, at high altitudes, the air-fuel ratio is set slightly richer than at low altitudes to increase engine output and reduce NOx in the exhaust gas, while reducing the amount of EGR to commensurate with the reduction in NOx in the exhaust gas. Although it is possible to compensate for the lack of output by increasing the air-fuel ratio extremely, there is a limit to the durability of the catalyst installed in the exhaust system.

That is, if the air-fuel ratio at low altitude is too high, it is necessary to set the air-fuel ratio to an intermediate value, and it is also necessary to reduce the EGR amount slightly accordingly.

Conventionally (for example, see Japanese Patent Application Laid-Open No. 48-5431 and Japanese Utility Model Application No. 52-158221), these controls are performed using two systems: an air-fuel ratio system and an EGR system, and the device structure is complicated. There were drawbacks.

Therefore, in the present invention, we have developed a high altitude correction device for the engine that can perform these controls, that is, setting the air-fuel ratio to be slightly enriched and setting the EGR amount to slightly decrease at high altitudes, with a single correction device. This is what we intend to provide.

That is, the present invention focuses on the fact that in an engine in which the EGR passage is opened in the intake passage downstream of the venturi part of the carburetor, the EGR passage can be used as a passage for introducing correction air, and the intake air in the EGR passage is An atmospheric air introduction passage is opened in the EGR passage between the opening to the passage and a control valve interposed in the middle of the EGR passage to control the EGR passage, which introduces atmospheric air as correction air as the atmospheric pressure decreases. It is characterized by this.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

In the same figure, 1 is an air cleaner, 2 is an air cleaner 1
3 is an intake passage that supplies the air-fuel mixture generated in the carburetor 2 to the engine 4, 5 is a venturi section provided in the intake passage 3, and 6 is an intake passage 3 downstream of the venturi section 5. The installed throttle valve 7 is an exhaust passage connected to the engine 4.

The carburetor 2 is set so as to generate an air-fuel mixture with an air-fuel ratio slightly thinner than the stoichiometric air-fuel ratio.

8 has an introduction part 8a opening into the exhaust passage 7 at one end, and a throttle valve 6 downstream from the venturi part 5 at the other end.
E having a recirculation port 8b that opens into the intake passage 3 more upstream;
A control valve 9 for controlling the amount of EGR is interposed in the middle of the EGR passage 8, which is a GR passage.

The control valve 9 has a valve body 12 supported by a diaphragm 10 via a rod 11 to open and close the EGR passage 8, and has a negative pressure chamber 13 and an atmospheric chamber 14 separated by the diaphragm 10, The negative pressure chamber 13 is located upstream of the throttle valve 6 of the intake passage 3 via the negative pressure introduction passage 15 until the throttle valve 6 is opened to a predetermined opening degree. When the engine is opened, the intake passage 3 is connected to the negative pressure outlet 16 which opens to be located downstream of the throttle valve 6, and the negative pressure chamber 1
3 is compressed with a spring 17, and until the throttle valve 6 is opened to a predetermined opening degree, intake negative pressure does not act on the negative pressure outlet 16 and negative pressure is not introduced into the negative pressure chamber 13. While the spring force of the spring 17 closes the valve body 12, when the throttle valve 6 opens beyond a predetermined opening degree, the intake negative pressure acting on the negative pressure outlet 16 is converted into negative pressure through the negative pressure introduction passage 15. By being introduced into the chamber 13, the diaphragm 10 is biased against the spring force of the spring 17, and the bias of the diaphragm 10 causes the valve body 12 to open, thereby reducing the intake negative pressure acting on the negative pressure outlet 16. It is configured to increase the opening degree of the valve body 12 in accordance with an increase in pressure.

Further, reference numeral 18 denotes an atmosphere introduction passage whose one end communicates with the clean side of the air cleaner 1;
The other end of 8 is opened to the EGR passage 8 between the recirculation port 8b of the EGR passage 8 and the control valve 9, and an on-off valve 20 that is opened and closed by a bellows 19 is interposed in the middle of the atmosphere introduction passage 18. It is configured to introduce atmospheric air as correction air and supply it to the EGR passage 8 as the atmospheric pressure decreases.

The amount of corrected air introduced through the atmosphere introduction passage 18 is set so that the air-fuel ratio when moving from a lowland to a highland can be corrected by approximately half, for example, without having to correct the entire air-fuel ratio.

Therefore, in the above embodiment, when driving on low ground,
When throttle valve 6 is opened more than a predetermined opening degree, control valve 9
As the EGR passage 8 is opened by the opening operation of Atmospheric introduction passage 18 by closing operation
is closed, the EGR passage 8 recirculation port 8b
Only a certain amount of GR gas is supplied to the Q intake passage 3, thereby reducing NOx in the exhaust gas and improving fuel efficiency.

On the other hand, when traveling at high altitudes, the bellows 19 allows the on-off valve 20 to
is opened and the atmosphere introduction passage 18 is opened, so that the atmosphere as correction air is supplied to the EGR passage 8 via the atmosphere introduction passage 18, and a part Q□ of the flow rate Q flowing through the EGR passage 8 is supplied to the atmosphere. In other words, part Q1 of the EGR gas amount Q flowing through the EGR passage 8 during lowland driving is replaced with the atmosphere, and a constant amount Q□ of the atmosphere and a constant amount of air from the recirculation port 8b of the EGR passage 8 □ EGR gas (Q1
+Q2=Q) is supplied to the intake passage 3.

As a result, the air-fuel mixture is supplied to the engine 4 with an air-fuel ratio that is smaller than the enrichment rate when moving from a lowland to a highland, and is slightly richer than that at a lowland. At the same time, the amount of EGR decreases, thereby reducing NOx. , it is possible to compensate for the lack of output and also to improve the durability of the catalyst and the like.

In the above embodiment, EGR is performed by opening the control valve 9 when the throttle valve 6 is opened to a predetermined opening degree or more, but the negative pressure outlet is opened downstream of the throttle valve 6 in the intake passage 3. EGR may be performed over the entire operating range, or a three-way solenoid valve or the like may be interposed in the middle of the negative pressure introduction passage 15 to stop EGR during operation when EGR is unnecessary. Of course.

As explained above, according to the present invention, the EGR passage is interposed between the opening to the intake passage of the EGR passage opened in the intake passage downstream of the venturi part of the carburetor and the EGR passage.
The air-fuel ratio at high altitudes can be adjusted slightly by using a single correction device with a simple configuration that opens an air introduction passage that introduces air as the atmospheric pressure decreases into the EGR passage between the control valve that controls the amount of air and the EGR passage. Can be enriched as well as EGR
Since the amount can be slightly reduced and the lack of output during high-altitude driving can be improved, the high-altitude correction device can be simplified.

[Brief explanation of drawings]

The drawings are schematic illustrations illustrating embodiments of the present invention. 1... air cleaner, 2... carburetor,
3...Intake passage, 4...Engine, 5
...Venturi section, 6...Throttle valve, 7...Exhaust passage, 8...EGR passage, 8a...Inlet, 8b ... Reflux port, 9 ... Control valve, 10 ... Diaphragm, 11 ... Rod, 12 ... Valve body,
13...Negative pressure chamber, 14...Atmospheric chamber, 1
5... Negative pressure introduction passage, 16... Negative pressure outlet, 17... Spring, 18...
Atmosphere introduction passage, 19... Bellows, 20...
...Opening/closing valve.

Claims (1)

[Scope of utility model registration request] In an engine in which an exhaust gas recirculation passage is opened in the intake passage downstream of the venturi portion of the carburetor, the exhaust gas recirculation passage is interposed between the opening of the exhaust gas recirculation passage to the intake passage and the exhaust gas recirculation passage. 1. A high-altitude correction device for an engine, characterized in that an atmospheric air introduction passage is opened in an exhaust gas recirculation passage between a control valve that controls a flow rate and which introduces atmospheric air as the atmospheric pressure decreases.