JPH01312A - Spark ignition engine with catalyst - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a spark ignition engine such as a gas engine, and more particularly to a spark ignition engine equipped with a catalyst for purifying exhaust gas in the exhaust path of the engine.

(Conventional technology) Conventionally, this type of engine has been constructed as shown in FIG.

In FIG. 7, a mixer 4 is connected to an inlet of an intake manifold 2 of a gas engine main body 1 via a passage having a throttle 3. As shown in FIG.

The mixer 4 is provided with an air intake 5 and a fuel inlet 6. The fuel supply 6 is connected to a fuel gas supply source (not shown) via a main gas passage 8 having a gas regulator 7 in the middle. An inlet of an auxiliary gas passage 9 is connected to the main gas passage 8 on the downstream side of the gas regulator 7 .

The auxiliary gas passage 9 is provided with an actuator valve 10 in the middle, and its outlet is connected to the mixture passage between the throttle 3 and the mixer 4.

The actuator valve 10 is for controlling the air-fuel ratio of the intake air (air-fuel mixture), and is opened and closed by an electric signal from the controller 11, thereby controlling the flow rate of fuel in the auxiliary gas passage 9 to adjust the air-fuel ratio of the air-fuel mixture. is designed to be controlled. Specifically, the mixer 4 forms a lean mixture to which fuel controlled by the actuator valve 10 is added from the auxiliary gas passage 9.

The controller 11 controls the opening degree of the auxiliary gas passage 9 based on signals from various sensors. Specifically, the above sensor is a rotation detection sensor 1 provided in the engine body 1.
2. A load detection sensor 13 provided in the intake manifold 2, and an oxygen sensor 14 provided in the engine exhaust path.

An exhaust manifold 15, a supercharger 16, and a three-way catalyst 17 are provided in the engine exhaust path in this order from the upstream side, and the oxygen sensor 14 is provided in an exhaust passage 18 that connects the supercharger 16 and the catalyst 17.

(Problem to be Solved by the Invention) However, in general, as shown in FIG. It is on the richer side than (Amount - 0). Therefore, in order to activate the catalyst 17, the air-fuel ratio of the air-fuel mixture cannot be set within a narrow range around the stoichiometric air-fuel ratio, but must be varied over a wide range including the catalyst window. As a result, the conventional t1
In the 11 configuration, there is a problem in that the output and rotational speed of the engine body 1 vary greatly in response to the range of variation in the air-fuel ratio of the air-fuel mixture.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a spark ignition type engine body, an intake air-fuel ratio control section provided in the intake path of the engine, and a control section provided in the exhaust path of the engine. An exhaust purification catalyst and an exhaust air-fuel ratio control section connected to the exhaust path on the upstream side of the catalyst to control the air-fuel ratio of the exhaust gas are provided, and the exhaust air-fuel ratio control section controls the air-fuel ratio of the exhaust gas to the catalyst. The feature is that the range is set to include the active range.

The exhaust air-fuel ratio control section may be provided with a fuel blowing means or an air blowing means.

(Function) According to the above configuration, the exhaust air-fuel ratio control unit sets the air-fuel ratio of the exhaust gas to the active range of the catalyst, so the intake air-fuel ratio control unit sets the air-fuel ratio without considering the catalyst active range. Therefore, the air-fuel ratio of the air-fuel mixture can be set within a narrow range or at a constant value.

(Example) In FIG. 1, parts corresponding to those in FIG. 7 are given the same reference numerals. The illustrated embodiment differs from the conventional structure shown in FIG. 7 in its basic structure only in that an exhaust air-fuel ratio control section 20 is added.

The exhaust air-fuel ratio control section 20 includes a fuel passage 21 and an actuator valve 22 provided in the middle thereof. The fuel passage 21 has an inlet connected to the main gas passage 8 on the downstream side of the gas regulator 7 . fuel passage 21
The outlet serves as a fuel blowing portion, and opens into the exhaust passage 18 between the supercharger 16 and the oxygen sensor 14.

The actuator valve 22 is electrically connected to the controller 11, and is adapted to control the fuel flow rate in the fuel passage 21, that is, the amount of fuel added to the exhaust gas, based on a signal from the controller 11. An oxygen sensor 23 is also provided in the exhaust passage 18 between the outlet of the passage 21 and the supercharger 16, and this sensor 23 is also electrically connected to the controller 11.

In the above system, the air-fuel ratio of the air-fuel mixture supplied to the engine body 1 from the mixer 4 and the auxiliary gas passage 9 has a fluctuation range within a narrow range including the stoichiometric air-fuel ratio (λ-1,0), as shown in FIG. It is set to lean toward the catalyst window. Therefore, engine body 1
The output of the engine is maintained near the maximum value, and the fluctuation range of the output is narrowed, and the fluctuation range of the rotational speed is also narrowed.

On the other hand, the exhaust air-fuel ratio control section 20 shown in FIG. 1 injects fuel gas into the exhaust gas to lower its air-fuel ratio, but the fluctuation range of the air-fuel ratio of the exhaust gas depends on the window of the catalyst, as shown in FIG. It has a wide range of settings including: Therefore, exhaust gas can be effectively purified by the catalyst 17.

(Effects of the Invention) As explained above, according to the present invention, the exhaust air-fuel ratio control section 20 is provided in the exhaust path, so in a system equipped with the catalyst 17, the range of fluctuations in the output and rotational speed of the engine body 1 is narrowed. Can be set.

In particular, as in the embodiment shown in Fig. 1, the fluctuation range of the intake air-fuel ratio can be set to a narrow range that includes the theoretical value (λ-1,0), thereby reducing engine output fluctuations. .

(Other Embodiments) In the embodiment shown in FIG. 3, the exhaust air-fuel ratio control section 20 includes an air passage 25 and an actuator valve 26. The inlet of the air passage 25 is connected to the air intake 5 of the mixer 4, and the outlet is connected to the exhaust passage 18. Further, the actuator valve 26 controls the air flow rate of the air passage 25 in response to a signal from the controller 11. In this embodiment, an air-fuel ratio sensor 27 is used in place of the oxygen sensor 23 shown in FIG.

In this structure, as shown in FIG. 4, the air-fuel ratio of the mixture is set to a constant value on the richer side than the window of the catalyst, and by adding air to the exhaust gas by the exhaust air-fuel ratio control section 20 shown in FIG. , the exhaust air-fuel ratio is set to a range that includes the catalyst window.

The structures shown in FIGS. 1 and 3 both include a supercharger 16, and therefore the pressure in the exhaust passage 18 is low. However, if the supercharger 16 is abolished, the exhaust passage 18 Since the pressure increases, it becomes impossible to blow fuel gas or air into the exhaust passage 18 with the structure as it is. In such a case, as shown in FIGS. 5 and 6, an ejector 30 is provided in the exhaust passage 18, and the outlets of the fuel passage 21 and the air passage 25 are located within the ejector 30, thereby reducing the negative pressure generated in the ejector 30. This is used to supply fuel or air from the fuel passage 21 and the air passage 25 to the exhaust passage 18.

Of course, it is possible to eliminate the ejector 30 and use a pressurizing device (booster or blower) to pressurize the fuel and air and supply it from the fuel passage 21 and the air passage 25 to the exhaust passage 18.
Compared to such a structure, the structure shown in FIGS. 5 and 6 has the advantage that no power is required to pressurize fuel or air.

[Brief explanation of drawings]

FIG. 1 is a layout diagram of an embodiment of the present invention, FIG. 2 is a graph showing air-fuel ratio control characteristics and output characteristics of the structure shown in FIG. 1, FIG. 3 is a layout diagram of another embodiment of the present invention, and FIG. The figure is a graph showing the air-fuel ratio control characteristics and output characteristics of the structure shown in Figure 3, Figures 5 and 6 are layout diagrams of still another embodiment of the present invention, Figure 7 is a layout diagram of a conventional example, Figure 8 is the seventh
3 is a graph showing air-fuel ratio control characteristics and output characteristics of the structure shown in the figure. 1...Engine body, 9.10...Auxiliary gas passage and actuator valve (intake air-fuel ratio control section), 1
7... Catalyst, 18... Exhaust passage, 20... Exhaust air-fuel ratio control unit Patent applicant Yanmar Diesel Co., Ltd. Fig. 4-□ - 1... Engine body 9... Auxiliary gas passage 10...・Actuator valve 17...Catalyst 22...Actuator valve Fig. 2

Claims (3)

[Claims] (1) A spark ignition type engine body, an intake air-fuel ratio control section provided in the intake path of the engine, an exhaust purification catalyst provided in the exhaust path of the engine, and a device connected to the exhaust path on the upstream side of the catalyst. 1. An exhaust air-fuel ratio control section that controls an air-fuel ratio of exhaust gas, and the exhaust air-fuel ratio control section sets the air-fuel ratio of the exhaust gas to a range that includes the active range of the catalyst. (2) The catalyst-equipped spark ignition engine according to claim 1, wherein the exhaust air-fuel ratio control section includes fuel injection means. (3) The catalyst-equipped spark ignition engine according to claim 1, wherein the exhaust air-fuel ratio control section includes air blowing means.