JPH0442513Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement of an air-fuel ratio controller for a gas engine in which a three-way catalyst is installed in the exhaust system.

[Conventional technology]

A three-way catalyst reduces carbon monoxide (CO) in exhaust gas.
It simultaneously oxidizes hydrocarbons (HC) and reduces nitrogen oxides (NOx), converting the three harmful gas components in exhaust gas into harmless carbon dioxide (CO ₂ ), water vapor (H ₂ O), and nitrogen (N ₂ ) is used for cleaning.

When purifying exhaust gas using a three-way catalyst, the purification characteristics vary greatly depending on the set air-fuel ratio of the engine. When the air-fuel ratio is lean, oxygen (O ₂ ) is produced even after combustion.
, the oxidizing action becomes active and the reducing action becomes inactive. Conversely, when the air-fuel ratio is high, the oxidizing action becomes inactive and the reducing action becomes active. The three-way catalyst works most effectively when this oxidation and reduction are balanced (near the stoichiometric air-fuel ratio).

Therefore, conventionally, as shown in Fig. 4, an O ₂ sensor 3 is provided in the exhaust system 2 of the gas engine 1.
Utilizing the fact that the output of the O ₂ sensor 3 changes depending on the air-fuel ratio, the air-fuel ratio control valve 6 provided in the bypass line 5 is controlled to open and close via the controller 4. For example, when the current air-fuel ratio is lower than the stoichiometric air-fuel ratio, the output of the O ₂ sensor 3 becomes less than the set value, and the air-fuel ratio control valve 6 is output via the controller 4.
On the contrary, when the O 2 sensor 3 is rich, the output of the O ₂ sensor 3 exceeds the set value, and the air-fuel ratio control valve 6 is opened via the controller 4.

In FIG. 4, 7 is a throttle valve installed in the air supply system 8 of the gas engine 1, and upstream of the throttle valve 7 is a mixer 9 for mixing air and gas at a predetermined ratio.
In this figure, a bypass line 5 is provided on the air supply pipe 10 side, but the gas supply pipe 1
Some are implemented by providing a bypass line 5 on the first side.

As a side note, it is also possible to consider a method in which the air-fuel ratio control valve 6 is installed in the air supply pipe 10 or the gas supply pipe 11 instead of in the bypass line 5 as described above, but this method is too sensitive and smooth. (e.g. slow response, hunting, etc.),
If there are problems such as the engine closing due to runaway and stopping, etc., the air-fuel ratio is roughly set in the mixer 9 as shown in Figure 4, and the additional amount from the bypass line 5 is determined by the O ₂ sensor. 3, the above problem is solved by controlling the air-fuel ratio control valve 6 via the controller 4.

[The problem that the idea attempts to solve]

Conventional air-fuel ratio controllers do not allow the air-fuel ratio control valve 6 to be fully opened or fully opened due to changes in air volume due to temperature changes in winter and summer, dirt (clogging) of the air filter provided upstream of the air supply pipe 10, etc. Even if it is closed, the output of the O ₂ sensor 3 may not recover to the set value, and in such a case, the cleaning by the three-way catalyst in the catalyst tank 12 becomes worse.

The present invention was proposed in view of the above-mentioned shortcomings of the prior art, and its purpose is to provide an air-fuel ratio controller that can appropriately adjust the air-fuel ratio over a wide range beyond the limits of the air-fuel ratio control valve. This is what we are trying to provide.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a mixer installed upstream of a throttle valve in the air supply system of a gas engine to mix air and gas at a predetermined ratio, and a mixer that bypasses the mixer to mix air and gas at a predetermined ratio. a bypass line that supplies O 2 to the air supply system upstream from the throttle valve; an air-fuel ratio control valve installed in the bypass line; and an O ₂ control valve installed in the exhaust system of the gas engine that detects O ₂ components in the exhaust gas. sensor and above
In a gas engine that consists of a controller that controls the opening and closing of the air-fuel ratio control valve based on the output of the O ₂ sensor, and a three-way catalyst installed in the exhaust system downstream of the O ₂ sensor, a three-way catalyst is installed in a part of the air-fuel ratio control valve. ,
It is equipped with a detection body that detects whether it is fully open or fully closed, an auxiliary control valve installed in the gas supply pipe, and an auxiliary controller that controls opening and closing of the auxiliary control valve based on the detection signal of the detection body. Yes, also
The opening/closing operation of the auxiliary control valve by the auxiliary controller is performed by a bidirectional timer.

[Effect]

When the air-fuel ratio is around the stoichiometric air-fuel ratio, the three harmful gas components (CO), (HC), and (NOx) in the exhaust gas
The oxidation reaction and reduction reaction of the three-way catalyst are performed in a well-balanced manner, resulting in the production of harmless gases (CO ₂ ), (H ₂ O), (N ₂ ).
be cleaned. In this state, the output of the O ₂ sensor is at the set value, the controller does not operate, and the opening degree of the air-fuel ratio control valve is, for example, in a half-open state. Therefore, the detection body does not perform any detection operation, and the auxiliary control valve remains in its fixed position.

Now, when the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio, in the case of the air bypass method, the O ₂ sensor operates the air-fuel ratio control valve in the opening direction via the controller to increase the amount of air. In the case of the gas bypass system, the air-fuel ratio control valve is operated in the closing direction to reduce the amount of gas.

When the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio, the operation opposite to the above is performed.

In the case of the air bypass method, when the air-fuel ratio control valve is fully open, the fully open detector detects this and closes the auxiliary control valve via the auxiliary controller, so that the air-fuel ratio control valve is fully closed. If so, perform the opposite operation to the above.

In the case of the gas bypass method, when the air-fuel ratio control valve is fully closed, the fully closed detector detects this, closes the auxiliary control valve via the auxiliary controller, and the air-fuel ratio control valve becomes fully open. If so, do the opposite.

The bidirectional timer prevents mutual interference between the air-fuel ratio control valve and the auxiliary control valve.

〔Example〕

FIG. 1 is a schematic diagram of a gas engine supply and exhaust system showing a first embodiment of the present invention, in which 1 is a gas engine, 2 is an exhaust system, 3 is an O ₂ sensor, 4 is a controller, and 5 is a bypass line. , 6 is an air-fuel ratio control valve, 7 is a throttle valve, 8 is an air supply system, 9 is a mixer, 10 is an air supply pipe, 11 is a gas supply pipe, 12
is a catalyst tank, and this configuration is the same as the conventional configuration of the air bypass system in which the bypass line 5 is provided on the air side.

In the present invention, the air-fuel ratio control valve 6 is provided with a fully open detector 13.
and a fully closed detection body 14, and a gas supply pipe 1.
An auxiliary control valve 15 is provided in the middle of 1, and the auxiliary control valve 15 is controlled to open and close via an auxiliary controller 16 based on detection signals from a fully open detector 13 and a fully closed detector 14.

The fully open detector 13 and the fully closed detector 14 are composed of limit switches, for example, and the auxiliary controller 16 can be composed of a forward/reverse motor, a rotary solenoid, a fluid pressure cylinder, etc.
As an example, the figure shows a case where a forward/reverse motor 16a of a type called a module roll motor is used, and in this case, the fully open limit switch 13a and the fully closed limit switch 14a are Forward rotation coil 16
Although it is possible to insert the circuit directly into the circuit of b and the circuit of the reversing coil 16c, the bidirectional timer 1
The timer contacts 17a and 18a of 7 and 18 are inserted into both circuits, and the respective bidirectional timers 17 and 18 are operated (ON) for a certain period of time and stopped (OFF) for a certain period of time using the fully open limit switch 13a and the fully closed limit switch 14a. I'm trying to give it back.

Operation of the above two-way timers 17 and 18 (ON)
Mutual interference between the air-fuel ratio control valve 6 and the auxiliary control valve 15 can be prevented by setting the time to be sufficiently short and the stop (OFF) time to be sufficiently long.

The first embodiment of the present invention has the above configuration, and its operation will be explained next.

Normally, the air-fuel ratio is controlled to be close to the stoichiometric air-fuel ratio by controlling the opening and closing of the air-fuel ratio control valve 6 using the O ₂ sensor 3 of the exhaust system 2 via the controller 4. However, if the temperature change is larger than expected or the air filter becomes dirty (clogged),
If the air-fuel ratio cannot be controlled to near the stoichiometric air-fuel ratio even if the air-fuel ratio control valve 6 is fully opened or fully closed, the device of the present invention operates as follows to eliminate the above-mentioned problem.

That is, when the air-fuel ratio control valve 6 is fully opened, the full-open limit switch 13a in FIG.
ON, the bidirectional timer 17 is operated for a certain period of time, the timer contact 17a is turned ON, and only during this time, current is passed through the forward rotation coil 16b of the forward/reverse rotation motor 16a, and the forward/reverse rotation motor 16a is rotated in the forward direction for auxiliary control. Valve 15 is closed. This reduces the gas supply amount and corrects the air-fuel ratio. Here, the closing operation of the auxiliary control valve 15 is performed by the bidirectional timer 1.
7 shortens the operation (ON) time and stops (OFF)
By setting a long time, the closing operation will be completed in a short time, but the closing operation will not be performed again until the predetermined stop (OFF) time has elapsed before the next closing operation, which will prevent chattering. It is prevented.

Furthermore, when the opening degree of the air-fuel ratio control valve 6 becomes fully closed, the fully closed limit switch 14a shown in FIG.
ON, the bidirectional timer 18 is operated for a certain period of time, the timer contact 18a is turned ON, and only during this time, current is passed through the reversing coil 16c of the forward/reverse motor 16a, the forward/reverse motor 16a is reversed, and the auxiliary control valve 15 is turned on. Operate the opening. This increases the amount of gas supplied and corrects the air-fuel ratio. In this case as well, chattering is prevented by shortening the operating (ON) time and lengthening the stopping (OFF) time of the bidirectional timer 18.

For convenience of explanation, it is easy to understand that the initial setting conditions for the air-fuel ratio control valve 6 and the auxiliary control valve 15 are set to a half-open state for both, but the invention is not limited to this.

Next, a second embodiment of the present invention will be explained with reference to FIG. In the second embodiment, a bypass line 5 is provided on the gas side, and the other configurations are the same as in the first embodiment. However, the opening/closing conditions for the auxiliary control valve 15 due to fully opening and fully closing the air-fuel ratio control valve 6 are inversely related to those in the first embodiment.

That is, when the air-fuel ratio control valve 6 is fully open, the auxiliary control valve 15 is opened, and when it is fully closed, the auxiliary control valve 15 is closed. The bidirectional timers 17 and 18 shown in the figure are inserted and connected to the electrical circuit of the forward/reverse motor 16a in a reverse relationship.

[Effect of idea]

According to the present invention, it is possible to overcome the case where conventional methods become uncontrollable due to environmental changes such as temperature changes or dirt on the air filter, and it is possible to appropriately adjust the air-fuel ratio over a wide range.

Furthermore, according to the present invention, there is no need to change the control logic of the conventional controller, and furthermore, by using a bidirectional timer, mutual interference such as chatter between the air-fuel ratio control valve and the auxiliary control valve is prevented. can do.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a gas engine supply and exhaust system showing a first embodiment of the present invention, FIG. 2 is a control electric circuit diagram showing an embodiment of the main part of the present invention in the first embodiment, and FIG. The figure is a schematic diagram of a gas engine supply and exhaust system showing a second embodiment of the present invention, and FIG. 4 is a schematic diagram of a conventional gas engine supply and exhaust system. 1... Gas engine, 2... Exhaust system, 3...
O ₂ sensor, 4... Controller, 5... Bypass line, 6... Air-fuel ratio control valve, 7... Throttle valve, 8... Air supply system, 9... Mixer, 10... Air supply pipe, 11... ... Gas supply pipe, 12 ... Catalyst tank, 13 ... Fully open detection body, 14 ... Fully closed detection body,
15... Auxiliary control valve, 16... Auxiliary controller, 17, 18... Bidirectional timer.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A mixer installed upstream of the throttle valve in the air supply system of a gas engine to mix air and gas at a predetermined ratio; a bypass line that supplies O 2 to the air supply system upstream from the throttle valve; an air-fuel ratio control valve installed in the bypass line; and an O ₂ control valve installed in the exhaust system of the gas engine that detects O ₂ components in the exhaust gas. In a gas engine consisting of a sensor, a controller that controls the opening and closing of the air-fuel ratio control valve based on the output of the O ₂ sensor, and a three-way catalyst installed in the exhaust system downstream of the O ₂ sensor, one of the air-fuel ratio control valves is used. a detection body installed in the gas supply pipe to detect whether it is fully open or fully closed; an auxiliary control valve installed in the gas supply pipe; and an auxiliary controller that controls opening and closing of the auxiliary control valve based on a detection signal from the detection body. An air-fuel ratio controller characterized by comprising: (2) The air conditioner according to claim 1, characterized in that the opening/closing operation of the auxiliary control valve by the auxiliary controller is performed via a bidirectional timer based on a detection signal from a detection body that detects fully open and fully closed states of the air-fuel ratio control valve. Fuel ratio controller.