JPS58192941A - Fuel-air mixture control device for modified gas engine - Google Patents

Abstract

PURPOSE:To improve response of the titled device to an abrupt change in an engine load, by arranging such that a modified gas flow ratio and an excess air ratio may be predetermined in their maximum levels in accordance with a capability of a modifier to modify gas properties, in an engine adapted to use both liquid fuels and modified gases. CONSTITUTION:Supplied to an engine 4 is an air passing through an air valve 28, a modified gas flowing via a gas valve 25 out of a modifier (not shown) and a liquid fuel passing through an injection valve 27. A controller 29 adapted to input signals indicative of operating conditions computes required levels of gas- fuel ratio (a flow ratio of modified gas to a total fuel rate) and an excess air ratio from a magnitude of accelerator operation and an engine speed, while at the same time computing maximum limit levels of gas-fuel ratio and the excess air ratio utilizing signals outputted from a gas pressure sensor 33 and a modified catalyst temperature sensor 32. Smaller ones of these required and maximum limit levels are selected to control each supplying valve, and thereby making it possible to control the excess air ratio in a stable state even when an abrupt change takes place in an engine load as experienced in burning a poorly modified gas.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mixture control device for a reformed gas engine used as a motor vehicle, etc.

Liquid fuels such as methanol, ethanol, gasoline, and kerosene can be reformed through catalysts into gases containing large amounts of hydrogen and -hydrogen-hydrogen, and this reformed gas has excellent combustibility and high thermal efficiency, resulting in low fuel consumption. Engines that use this reformed gas as fuel are attracting attention in recent years because of their improved characteristics and clean exhaust. However, it is not necessarily possible to obtain an optical output with only the reformed gas, so it is desirable to supply unreformed liquid fuel in addition to the reformed gas.

In this way, when reformed gas and unreformed liquid/solid fuel are used together, the air-fuel ratio of the mixture and the amount of difference between the supplied reformed gas and liquid fuel depend on the operating conditions of the engine. It is necessary to control the ratio to maintain good thermal efficiency, exhaust characteristics, and output characteristics of the engine.

An example of the air-fuel mixture control system for an alcohol reformed gas engine, which was previously proposed by the applicant of the present invention (see Japanese Patent Publication No. 55-104542), will be described below with reference to FIG. The reformed gas introduced from the gas port 1 is supplied to the engine 4 through a gas flow meter 2't-, the flow rate of which is controlled by a gas pulp 3. Air introduced from the air cleaner 5 flows into a primary air supply path 6 and a secondary air supply path 1 that are parallel to each other. Both supply channels 6
．． 7 is provided with a secondary air pulp 8 and a secondary air valve 9, both valves 8. The primary air and secondary air, whose flow rates are controlled at 1, are combined and supplied to the engine 4.

The reformed gas population 1 and the air cleaner 5 population, which is the inlet of air, are approximately equal to atmospheric pressure, and the reformed gas and air flow through their respective passages under the negative intake pressure of the engine 4, and unreformed alcohol is transported to the alcohol injector 10. The flow rate is controlled by and supplied to the engine 4. Further, the gas valve 3 and the open air valve 8 are interlocked via an interlocking device 11,
It is operated by the driver via an accelerator wire 12 using an accelerator pedal (not shown) as an operating means, and the secondary air valve 9 is controlled based on the flow rate of the reformed gas detected by the gas flow meter 2. . In addition, the −th airflow t is
The required fuel sit is set in proportion to this secondary air flow cover in response to the operating flow rate of the accelerator pedal. When the supply of reformed gas is sufficient, the required fuel flow rate is covered by the reformed gas, and the secondary air valve 9
open to dilute the mixture. Conversely, if the supply of reformed gas is insufficient or limited, the shortage of reformed gas relative to the required fuel flow rate is compensated for by supplying alcohol, and the secondary air valve 9 is closed to reduce the air flow rate. . 13 calculates the alcohol supply amount by calculating the difference between the required fuel flow rate and the reformed gas flow rate, which are set based on the primary air flow rate;
This is a controller that controls the alcohol injector 10 based on this.

However, in such a conventional mixture control device for a reformed gas engine, if the reformed gas flow rate is insufficient due to insufficient reforming capacity of the reformer that reformes liquid fuel such as alcohol into gas, As mentioned above, since the configuration was such that the liquid fuel flow rate was controlled by detecting the difference between the required fuel flow rate and the reformed gas flow rate, the response during transient operation of the engine (especially during acceleration) was poor, and the air Temporary dilution or enrichment of the excess ratio occurs, which not only deteriorates fuel efficiency and exhaust characteristics, but also causes fluctuations in the reformer pressure, making pressure control difficult. friend.

The present invention has been made in view of the origin of the conventional art, and the present invention is based on the pressure of the reformed gas and the temperature of the reforming catalyst or a temperature related thereto. It is an object of the present invention to provide a mixture control device for a reformed gas engine that solves the above-mentioned problem by controlling the excess ratio.

The present invention will be explained below based on illustrated embodiments.

FIG. 2 is a system diagram showing an embodiment of the present invention, in which the reformed gas, which is obtained by reforming alcohol, for example, by a reformer installed in the exhaust passage (not shown) of the enref 210, is supplied to the cutoff valve 22t. - a gas valve 2 through a gas passage 23 provided with a gas manifold 24 connected to its downstream end;
Inhale from 5! It is supplied to the i-way 26. On the other hand, alcohol enters the intake passage 26 via the alcohol injector 27.
is injected near the intake boat. A Vi nitrogen air pulp 28 is interposed in an intake passage 26 upstream of the gas valve 25, and the air valve 28 is connected to an accelerator pedal (not shown) via a link 29, an air pulp ha ratio actuator 30, and an accelerator wire 31. Concatenated. The actuator 29 adjusts the opening ratio of the air pulp 28 to the accelerator operation amount according to a signal from the controller 2s to determine if there is an excess air 7.
4 (hereinafter referred to as λ) is driven to increase when the patient is seriously ill.

The gas 1 nifold 24 is provided with a gas temperature sensor 32 for detecting the temperature of the reformed gas, and a gas pressure sensor 33 for detecting the pressure of the reformed gas, and the actuator 30 includes a member connected to the accelerator wire 31@. An accelerator operation amount sensor 34 is provided to detect the accelerator operation amount in conjunction with the accelerator operation amount. Further, the distributor 35 is equipped with a rotation speed/crank angle sensor 36 that detects the engine rotation speed and crank angle, the intake passage 26 on the upstream side of the air valve 28 is equipped with an air flow sensor 37 that detects the intake air flow rate, and a reformer (not shown). are each provided with a catalyst temperature sensor 38 for detecting the temperature of the reforming catalyst.

The signals from each of these sensors are sent to the controller 29.
Based on these input signals, the controller 29 controls the gas pulp 25, alcohol injector 27 . The air pulp 28 is controlled so that the reformed gas and alcohol supply lid and the air flow rate are %+1J (ii41).

Next, 1. Specific I+I of the embodiment device having the above configuration.
The IJ control method will be explained with reference to FIGS. 3 to 5. FIG. 3 is a block diagram (data flow diagram) showing an example of the signal processing procedure of the controller 2S. From the detected engine rotation speed 1ine, the required load of the engine,
That is, the load factor is calculated. Then, the basic gas/fuel ratio calculation unit 40 calculates the basic gas/fuel ratio αg corresponding to the load factor.

, and calculates the basic excess air ratio λ0 corresponding to the basic excess air ratio calculation unit 41#'i load factor.

Here, since the basic gas/fuel ratio αgo and the basic excess air ratio are set independently for the load "4L," both of them can take optimum values.

On the other hand, the gas/fuel ratio limit value calculation unit 42 calculates the maximum limit value αgtirn of the gas/fuel ratio based on the reforming catalyst temperature and reformed gas pressure detected by the catalyst temperature sensor 38 and gas pressure sensor 33, and calculates the maximum limit value αgtirn of the gas/fuel ratio. The m1l1 army limit value calculation unit 43 calculates the maximum limit value λtim' of the excess air ratio corresponding to 6141m.

Here, α141m and λA1m are set as described later. That is, the combustion performance of the reformed gas depends on the reforming catalyst temperature H(t
The higher the aata) and the higher the reforming ability, the better the rounding,
The maximum limit a Ggtlm of the reforming gas supply amount can be set to be larger as the catalyst temperature is higher or the reformed gas pressure is higher, and its characteristics are shown in FIG. 4, for example. Therefore, α141 corresponds to the limit value Ggt1m of reformed gas supply amount.
m and 2141m, which has a proportional characteristic with respect to 6141m as shown in FIG. 5, are also set to increase as the reforming contact temperature and reformed gas pressure increase, respectively.

Then, the gas/fuel ratio calculation unit 44
The smaller of the fuel ratio αgo and the maximum limit value αgt1m of the gas/fuel ratio is selected and the gas/fuel ratio αgt- is set, and the excess air ratio calculation unit 45 calculates the basic excess air ratio λ0 and the excess air ratio limit value λAim. The excess air ratio λ is set by selecting the smaller one of the following. Liquid/fuel ratio calculation 1
The unit 46 calculates the diagonal flow rate (weight ratio) α as αt−1−αg, where the liquid/fuel ratio←liquid alcohol flow′jl/#. The fuel calculation unit 47 inputs the air flow rate Ga detected by the air flow meter 37 and the excess air ratio λ, and calculates the required fuel flow rate Gf. The gas flow rate calculation unit 48 inputs the required fuel flow 'jIkGf and the gas/fuel ratio αg and calculates the gas/fuel ratio αg. The alcohol flow calculation unit 49 calculates the alcohol flow IGt by inputting the required fuel flow cover Gf and the liquid/fuel ratio αt.

The gas valve control unit 50 inputs signals of the gas flow rate Gg, gas pressure Pg, gas temperature 11tg, engine speed no., and crank angle to control the opening degree of the gas valve 25 to obtain a predetermined reformed gas supply amount. Injector control unit 51
inputs signals of the alcohol flow rate at, engine speed and crank angle, and drives the injector 2T at a predetermined injection timing to obtain a predetermined alcohol supply amount. The air valve control unit 52 inputs the excess air ratio λ and controls the air valves 28 at a predetermined time. In this way, the air-fuel mixture can be controlled to obtain the desired gas/fuel ratio αg and excess air ratio λ. As described above, the maximum limit value αgt1m of the gas/fuel ratio and the maximum limit value λgti of the excess air ratio
The amount of reformed gas supplied is controlled in accordance with the reforming capacity of the reformer because it is set to increase as the m-gold reformed gas pressure and catalyst temperature increase. Therefore, when the reforming capacity is insufficient, the amount of reformed gas supplied can be restricted and the amount of liquid alcohol supplied can be increased by that amount, which improves responsiveness to sudden engine load changes and stabilizes the excess air ratio. As a result, fuel efficiency and exhaust characteristics can be improved, and since the pressure in the reformer is stabilized, controllability of reformed gas pressure can also be improved.

In this embodiment, the temperature of the reforming catalyst is directly detected, but it may be configured to be indirectly detected using the temperature of the reformer body.

As explained above, according to the present invention, the gas/fuel ratio and excess air ratio are controlled in accordance with the reforming capacity of the reformer by detecting the reformed gas pressure and the reforming catalyst temperature or related temperatures. As a result of this configuration, it is possible to obtain mixture control performance with excellent responsiveness to sudden engine load fluctuations, stabilize the excess air ratio, improve fuel consumption and exhaust characteristics, and improve the reformed gas pressure. It has an excellent % length that can improve controllability.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of a conventional mixture control device for a reformed gas engine, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 is a control block diagram (data FIG. 4 is a diagram showing the characteristics of the limit value of the reformed gas supply amount in the device of the above embodiment, and FIG. 5 is a diagram showing the characteristics of αgt1m-λ71m in the device of the embodiment. 21...Engine 25...Gas valve 2T...
・・Injector 28・Air valve 29・
...Controller 33...Gas pressure sensor 3
4...Accelerator operation lid sensor 36...Rotation speed/crank angle sensor 37...Air flow rate sensor 3
8...Catalyst temperature sensor 42...Gas/fuel ratio limit value calculation unit 43...Excess air sw & limit value calculation unit patent Applicant: Nissan Motor Co., Ltd. Daiba person Benkoushi Sasa Tori Tsuta Nifan

Claims (1)

[Claims] A reformed gas whose main component is a combustible component obtained by reforming liquid fuel in the presence of a reforming catalyst and an unreformed liquid fuel are used as fuel, and both of the above are determined based on the detection of various operating conditions of the engine. In a reformed gas engine in which the fuel supply rate and air-fuel mixture excess ratio are set, the reformed gas pressure and the reforming catalyst temperature or a series of temperatures thereof are detected, and as these detected values increase, A mixture control device for a reformed gas engine, which is provided with a control means for increasing the ratio of the amount of reformed gas supplied to the total amount of fuel supplied and the maximum limit value of the air ratio.