JPS59194070A - Fuel injection controller of modified gas engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of back fire caused by modified gas, by a method wherein, in a running condition in which both modified gas and liquid fuel are fed to an engine, control is effected so that liquid fuel is firstly injected, and after the injection is completed, modified gas is injected. CONSTITUTION:Liquid fuel, such as alcohol, is modified into gas, containing respective large amounts of hydrogen, and carbon monoxide, through the medium of a catalyst. An engine, which uses said modified gas in combination with unmodified liquid fuel, is provided with an engine condition detecting means 32 for detecting an engine running condition. According to the detected running condition, an injected amount setting means computes an amount of fuel injected and sets respective supply amount ratios of liquid fuel and modified gas to the injection amount. According to the set supply amount ratio, a liquid fuel injection means 33 such as an injector is firstly driven by an injection control means, and in response to the output of an injection completion detecting means 53 for detecting injection completion, a modified gas injecting means 34 such as gas valves is driven.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a fuel injection control device for a reformed gas engine, and more specifically, to a fuel injection control device for a reformed gas engine, which uses a liquid fuel in combination with a reformed gas obtained by reforming this liquid fuel. The present invention relates to a fuel injection control device for a reformed gas engine.

[Prior art]

Liquid fuels such as alcohol can be reformed through a catalyst into a gas containing large amounts of hydrogen and carbon oxides.This reformed gas has excellent combustibility and high thermal efficiency, improving fuel efficiency and reducing emissions. Engines that use this reformed gas as fuel have been attracting attention in recent years because it is clean. However, it is not always possible to obtain sufficient output with the reformed gas alone, so it is desirable to supply unreformed liquid fuel in addition to the reformed gas. In this way, when using reformed gas and unreformed liquid fuel together, the air-fuel ratio of the mixture and the weight flow rate ratio of the supplied reformed gas and liquid fuel must be adjusted depending on the operating conditions of the engine. It is necessary to control this in order to maintain good thermal efficiency, exhaust characteristics, and output characteristics of the engine, and to take into account especially backfire caused by reformed gas to the intake side.

As such a conventional fuel injection control device for a reformed gas engine, there is one described, for example, in Japanese Patent Application Laid-open No. 104542/1983. This device will be explained based on FIG. 1. Reformed gas is introduced from a gas port 1, passes through a gas flow meter 2, and is supplied to an engine 4 after its flow rate is controlled by a gas valve 3. Air is introduced from the air cleaner 5 and flows into a primary air supply path 6 and a secondary air supply path 7 that are parallel to each other. - The air flows through the supply path 6 into the second air supply path 6. - A primary air valve 8 for controlling the flow rate of secondary air is provided, and a secondary air valve 9 for the same function is provided for the secondary air supply path 7, and the flow rate is controlled by these two valves 8.9. The primary air and the secondary air are combined and supplied to the engine 4. Note that the pressures of the reformed gas population 1 and the air cleaner 5 population are atmospheric pressure, and the reformed gas and air flow through their respective supply paths under the negative suction pressure of the engine 4. The unreformed fuel is then supplied to the engine 4 with its flow rate controlled by the liquid fuel supply device 10.

Further, the gas valve 3 and the primary air valve 8 are interlocked via an interlocking device 11, and are operated via an accelerator wire 12 by an accelerator pedal (not shown) as an operating means operated by the driver. The secondary air valve 9 is controlled according to the flow rate of the reformed gas detected by the gas flow meter 2. Note that the -primary air flow rate corresponds to the accelerator pedal operation amount, and the required fuel flow rate is set in proportion to this primary air flow rate. When the flow rate of the reformed gas is sufficient, the reformed gas covers the entire required fuel flow rate and at the same time opens the secondary air valve 9 to dilute the air-fuel mixture (serious excess air). Conversely, when the supply of reformed gas is insufficient or limited, the shortage of reformed gas relative to the required fuel flow rate is compensated by the supply of liquid fuel, and the secondary air valve 9 is closed to reduce the air flow rate. (excess air weight). 13 calculates the liquid fuel supply amount by calculating the difference between the required fuel flow rate and the reformed gas flow rate from the intake air flow rate of the engine 4 and the reformed gas flow rate, and controls the liquid fuel supply device 10 based on this. This is a liquid fuel supply controller. The liquid fuel supply amount controller 13 supplies liquid fuel to the engine 4 as needed by controlling the liquid fuel supply device 10 when the supply of reformed gas is insufficient or limited.

However, in such conventional fuel injection control devices, the supply timings of reformed gas and liquid fuel are set independently without any correlation with each other. Under operating conditions, particularly under high-load operating conditions, in which both fuel and liquid fuel are supplied to the engine, the reformed gas retained in the intake manifold may be drawn into the cylinder before the liquid fuel when the intake valve is opened. Under such high-load operating conditions, the excess air ratio is small and the ratio of reformed gas to air is large. Furthermore, the temperature inside the cylinder is higher than that under the low load condition. Therefore, if the reformed gas containing hydrogen as a main component is drawn into the cylinder first, the reformed gas will be burned before all the air-fuel mixture is drawn in. At that time, since the reformed gas has an extremely high combustion speed, there was a problem in that backfire occurred.

[Purpose of the invention]

Therefore, the present invention injects the liquid fuel first under operating conditions in which both reformed gas and liquid fuel are supplied to the engine, and injects the reformed gas after the injection of this liquid fuel is completed.
The purpose is to prevent backfire caused by reformed gas.

[Structure of the invention]

FIG. 2 is an overall configuration diagram for clearly showing the configuration of the present invention. Unreformed liquid fuel and reformed gas obtained by reforming the liquid fuel are injected into the engine 21, and completion of injection of the liquid fuel is detected by an injection completion detection means 53. Engine state detection means 32 for detecting the operating state of the engine 21
The injection amount setting means calculates the fuel injection amount based on the signal from the fuel injection amount, and sets the liquid fuel and reformed gas O-14 supply ratio with respect to the fuel injection amount. Then, when the injection control means outputs a liquid injection signal corresponding to the liquid fuel supply amount ratio to the liquid fuel injection means 33, the liquid fuel injection means 33
injects liquid fuel, and after the liquid fuel injection is completed based on the output of the injection completion detection means 53, a gas injection signal corresponding to the reformed gas supply amount ratio is sent to the reformed gas injection means 34.
When the reformed gas is outputted, the reformed gas injection means 34 injects the reformed gas.

〔Example〕

Hereinafter, the present invention will be explained based on the drawings.

3 to 14 are diagrams showing an embodiment of the present invention.

In FIG. 3, 21 is an engine, and intake air is supplied to the engine 21 from an air cleaner 22, through an air flow meter 23, an intake passage 25 provided with an air valve u, and from each branch of an intake manifold 26, as shown by the white arrow in the figure. supplied to each cylinder. The intake air flow rate Ga taken into the engine 21 is detected by an air flow meter 23 and controlled by an air valve 24. The opening degree of the air valve 24 is controlled by a valve opening degree setting device 27. That is, the valve opening setting device 27 first sets the basic opening of the air valve U in conjunction with the accelerator pedal (not shown) (that is, in response to the operation amount PS of the accelerator pedal), and then sets the valve opening ratio. The actuator corrects the basic opening so that the excess air ratio of the mixture containing reformed gas (described later) is optimized. The operation amount PS of the accelerator pedal relative to the valve opening setting device 27 is detected by the accelerator operation amount sensor 29. Also, engine 2
1 crank angle (for example, 180'' or 1°) and rotation speed N are detected by a crank angle sensor 31 provided in the disc I-rebuter 30. The air flow meter 23 constitutes an engine state detection means 32 that detects the operating state of the engine 21.Liquid fuel (for example, methanol) is injected into the intake manifold 26 by an injector (liquid fuel injection means) 33, and a gas valve (reformer) is injected into the intake manifold 26. The reformed gas obtained by reforming the liquid fuel is injected by the gas injection means 34 at predetermined injection timings.The reformed gas supplied to the gas valve 34 is the liquid fuel that is supplied to the gas valve 34 via the fuel flow control valve 35. aisle 36
The liquid fuel flowing into the reformer 38 provided in the exhaust passage 37 through the filter is reformed in the reformer 38 by the action of a reforming catalyst that utilizes high-temperature exhaust gas (flowing as shown by the black arrow in the figure). The reformed gas is discharged into the gas passage 39 and is supplied to the gas valve 34 via a cooling gas cooler 40 and a gas cutoff valve 41. Here, the reformed gas is hydrogen (for example, when methanol is reformed).
The main components are combustible components such as -50%) and carbon oxide (25%), and its combustion rate is extremely high compared to the methanol mixture. The flow rate of liquid fuel flowing into the reformer 38 is controlled by a fuel flow control valve 35, and this fuel flow control valve 35 has a duty ratio of 5 to 100% at a constant frequency of 20 Hz, for example, depending on the duty ratio of the pulse signal. If the fuel flow rate changes, the fuel flow rate is controlled within the range of 0.5 to 10 kg/h. Further, the gas cutoff valve 41 is, for example, an engine 2
When the gas valve 34 is stopped, the gas passage 39 is shut off and the supply of reformed gas to the gas valve 34 is stopped. The pressure Pc of the reformed gas is detected by a gas pressure sensor 42 provided in the gas passage 39, and the temperature Pc of the reformed gas is detected by a gas temperature sensor 43. Furthermore, the catalyst temperature Tc in the reformer 38
at is detected by the catalyst temperature sensor 44. The exhaust passage 37 is provided with an exhaust bypass valve 45 that allows exhaust gas to bypass the reformer 38 without flowing through it, and an actuator 46 that drives the valve, and a muffler 47 is connected to the downstream side of the reformer 38. . The actuator 46 controls the amount of exhaust gas bypassed by the exhaust bypass valve 45.
The catalyst temperature Treat within 3 days of the reformer is set to a predetermined temperature (for example, 4
50°C) or below. Each of the sensors 23, 29, 3
Each signal from 1.42.43.44 is input to the control unit 48, and the control unit 48 controls the valve opening ratio actuator 28 based on these signals.
It controls the fuel flow control valve 35, the gas cutoff valve 4], and the actuator 46, and outputs a liquid injection signal SL to the injector 33 and a gas injection signal Scr to the gas valve 34 at mutually different predetermined injection timings. The injector 33 has a liquid injection signal S
The gas valve 34 is driven only for the time that L is input to inject liquid fuel, while the gas valve 34 is driven for only the time that the gas injection device S(:T is input) to inject reformed gas.

As shown in detail in FIG. 4, the control unit 48 includes an MPL+ (central processing unit) 49; device) 52, and an injection completion detection circuit (injection completion detection means) 53, each of the sensors 23.29.31.42.4
Each signal from 3.44 is input to l1052.

Furthermore, the l1052 has input terminals for various signals connected to various sensors other than those mentioned above on its input side, such as an engine coolant temperature sensor terminal 54, a vehicle speed sensor terminal 55, an ignition switch terminal 56, an idle switch terminal 57,
A neutral switch terminal 58 is provided, and various signal output terminals connected to various actuators other than those mentioned above are provided on the output side thereof, such as an ignition timing control terminal 59 and an idle rotation control terminal 60. The injection completion detection circuit 53 includes a resistor R1, a capacitor C1, an operational amplifier OPI, and a diode D1.The falling edge of the liquid injection signal SL output from the l1052 is detected by a differentiating circuit consisting of the resistor R1 and the capacitor C1, and the operational amplifier is detected. ○After amplification at P1, diode D is applied only at the falling edge.
A pulse signal for detecting injection completion is supplied to the input side of I1052 via I. A program for controlling the MPU 49 is written in the ROM 51, and a RAM 50 temporarily stores external data from the l1052. M.P.
U49 calculates each control value of the valve opening ratio actuator 28, fuel flow control valve 35, gas cutoff valve 41, and actuator 46 based on each signal input to l1052 according to the program written in ROM51, and executes l1052. In addition to outputting a control signal via 1052, the injection amounts and injection timings of liquid fuel and reformed gas are calculated and a liquid injection signal s is output via l1052.
L and a gas injection signal SCr, respectively. Note that the signal input to the l1052 is amplified by a sensor amplifier as necessary, and the signal output from the l1052 is excited by a driver as necessary.

Next, the control program written in the ROM 51 is
10 and 12, and in these figures Pyu to P4. shows each step of the flowchart.

First, engine intake mixture control will be explained with reference to FIG. When the program starts, first P,
Look up the low load factor Tpo corresponding to the accelerator operation, quantity PS, and rotation speed N from the data table shown in FIG. 6, and calculate the basic gas fuel ratio α from this low load factor Tpo in P2
go and the basic excess air ratio λ0 in Figures 7 and 8, respectively.
Look up from the data table shown in the figure.

That is, the low load factor Tpo is appropriately set according to the operating state of the engine, and this low load factor 'l'p.

The basic gas fuel ratio αg indicates the basic value of the reformed gas supply rate that is optimal for the operating state of the engine 21 according to the following.

is looked up. In addition, the basic gas fuel ratio αg.

indicates the weight ratio of reformed gas to the total fuel.

Further, the basic excess air ratio λ0 indicates the ratio of the actual air flow rate to the theoretical air flow rate required for combustion of the reformed gas, and is look-amplified according to the low load ratio Tpo. In this case, the basic excess air ratio λ0 is set to λo = 1.7 at partial load, and set to λo = 0.9 to 1.7 at high load, and the higher the load, the smaller the value (0.9 ) approach. Next, the warm-up state of the reformer 38 is determined in P3, and if it is warm-up, the gas fuel ratio limit αglim corresponding to the catalyst temperature Tcat of the reformer 38 is determined in p-+. It is determined whether the engine 21 is starting or not based on the temperature Tcat (corresponding to the upper limit of the reformed gas that can be supplied by the reformer 38), and P if it is in a cold state. And when starting, P
. Based on the reformed gas pressure P4, the gas fuel ratio limit αgl
Determine im, and set the gas fuel ratio limit αgl im to zero in P9 if there is a difference other than when starting (at stop).In P8, set the gas fuel ratio limit αgl im to zero.
Gas fuel ratio limit αglim determined according to the warm-up condition of 8.
is compared with the basic gas fuel ratio αgo, the smaller of these values is taken as the gas fuel ratio αg, and this gas fuel ratio αg
Set the excess air ratio λ based on .

For example, the excess air ratio λ is set to λ-λ0 when αglim>αgo, and is set to O1.1+αg when αglim<αgo. That is, the basic gas fuel ratio αg is the required value of the engine 21 in P8.

and the gas fuel ratio limit αglim, which is the value at which reformed gas can be supplied.
and select the optimal value within the range that can actually be supplied. Then, at P, the basic injection amount 'rp is determined based on the intake air amount Ga, excess air ratio A, and rotational speed N as T p =
It is calculated using the relational expression K x 'IjL x' (Tata L and K are constants for N people). Hereinafter, each valve opening time Ti6 of the gas valve 34 and the injector 33 is calculated based on the basic injection amount 'rp and the gas fuel ratio αg calculated as described above.
TiL is set, and a valve opening setting signal Sv is output based on the excess air ratio λ. That is,
P is the supply amount ratio of reformed gas to the basic injection amount 'rp, that is, the gas basic injection amount T p (qO is T pro-
Calculated as αg”rp, and the basic injection amount T of this gas is calculated using pH.
p(.

is corrected by the gas valve flow coefficient KV, pressure correction coefficient, PG, temperature correction coefficient KTG, and operation correction coefficient TS to calculate the gas injection amount Tpq.

Then, at P+2, the opening time T+(q) of the gas valve 34 corresponding to the gas injection amount Tp(, is set. On the other hand, the supply amount ratio of liquid fuel to the basic injection amount Tp, that is, the basic liquid injection amount T I)LO is P+3 and Tpl.

= (1-αg)・”rp, and at pH 4, this liquid basic injection amount TpLo is adjusted to various increase correction coefficients C0EF based on the operating state of the engine 21 (for example, various increase correction coefficients such as start-up increase correction, post-idle increase correction, etc.) ) and the operation correction coefficient TS to adjust the liquid injection amount T.
Calculate pL. Then, the valve opening time TiL of the injector 33 corresponding to the liquid injection amount Tpt is set at P+5. Furthermore, the optimum air valve opening AV for the excess air ratio λ already set at Pl is look-amplified from the data table shown in FIG. 9, and the actual air valve opening Ap is input at P+7. At step p19, this air valve opening degree Av is compared with the actual air valve opening degree Ap, and a control amount Cv for the valve opening degree setter 27 is calculated. In this case, A
A control iCv that closes the air valve 24 when p>AV, a control iCv that opens the air valve 24 when Ap<Av, and stops it when Ap=Av is calculated. And P
At l'1, a valve opening setting signal Sv corresponding to this control amount Cv is output to the air valve opening ratio actuator 28. Therefore, the opening degree of the air valve 24, which changes in conjunction with the accelerator pedal, is corrected so that the excess air ratio λ of the intake air-fuel mixture is always optimized, and the combustion performance of the engine 21 can be maintained at a good level.

Next, the reformed gas and liquid fuel corresponding to the gas injection amount Tpq and liquid injection amount TpL set as described above are respectively injected into the intake manifold 26 according to the flowchart shown in FIG. This is shown in the timing chart shown in Figures B-e.

In FIG. 10, the crank angle θ from the crank angle sensor 31 is input at P21, and at P22 the crank angle θ is set to a predetermined angle lN1T (for example, every 36° at the crank angle corresponding to one rotation of the engine 21). Determine whether it exists or not. If the crank angle θ is a predetermined angle lN1T (see FIG. 11a), it is determined in P23 whether the gas fuel consumption αg is αg=1, that is, whether all the fuel supplied to the engine 21 is reformed gas or not. If αg=1 (for example, when injecting reformed gas and liquid fuel together under high load), the liquid injection signal sL is sent to the injector 3 at P2+.
Output to 3. As a result, the injector 33 is driven for the valve opening time TiL (see No. 1111fflb).
, liquid fuel is injected into the intake manifold 26 according to the liquid injection amount TpL.

This liquid fuel evaporates near the intake valve, cools the surrounding area, and stays near the intake valve.

Next, in P25, it is determined whether or not the injection of liquid fuel has been completed. If it has not been completed, the process returns to P21, and if it has been completed (see FIG. 11C), a gas injection signal S is generated at P and b. is output to the gas valve 34. As a result, the gas valve 34
is driven for the valve opening time Ti6 (see FIG. 11C).
, the reformed gas is injected into the intake manifold 26 according to the gas injection amount Tp4. At this time, liquid fuel vapor remains near the intake valve in the intake manifold 26, and after the reformed gas is cooled by this vapor,
Together with the liquid fuel (see FIG. 11C), it is sucked into the cylinder at a predetermined timing and combusted.

In this way, it is possible to avoid the phenomenon that only the reformed gas is drawn into the cylinder before the liquid fuel under high load conditions, and also to reduce the temperature of the reformed gas when it is drawn into the cylinder. Since the temperature can be lowered by the vapor of the liquid fuel, it is possible to prevent backfire from occurring due to the reformed gas. On the other hand, when pza determines that αg = 1 (for example, when injecting only reformed gas at low load), P2 immediately outputs the gas injection signal 34 to the gas valve 34, and the gas inside the intake manifold 26 is Inject reformed gas to. Under this low load condition, the excess air ratio λ to the reformed gas is set to a large value (λ-1, 7), and the intake air-fuel mixture due to the reformed gas is in a lean state.

Therefore, since the concentration of the reformed gas is low, its combustion rate is slow, and the temperature inside the cylinder is relatively low compared to the high load condition, so no flashback occurs.

Next, a control program for the reformer 38 will be explained with reference to FIG. At Pa1, the basic flow rate Ticat of the reformed gas (that is, the injection amount per unit time injected from the gas valve 34) is input, and at Pa2, the reformed gas pressure PcT is input.

At P33, the reformed gas pressure P(.

is compared with a predetermined reference pressure (for example, 3+r/d), the basic flow rate Ticat is proportionally corrected, and further integrally corrected with P3+. Then, in P35, the flow control signal 312 corresponding to the corrected reformed gas flow rate is output to the fuel flow control valve 35 to appropriately control the amount of liquid fuel flowing into the reformer 38. Next, P3. Enter the catalyst temperature Tcat in P3'
? The optimal exhaust bypass valve 4 for the catalyst temperature Tcat in
Look-amplify the closing IBV of No. 5 from the data table shown in FIG. Also, Pa1? The optimum exhaust bypass valve 45 for the operating state of the engine 21 determined by the operating state, that is, the rotation speed N and the basic injection amount Tp.
Look-amp the closing amount BVε from the data table shown in FIG.
The smaller of the two days is set as the controlled closing amount B vs. This is to prevent the catalyst from overheating due to sudden changes in exhaust gas temperature. Next, the control closing amount BV is set at P2O.
s and the actual closing amount Bvp are compared, and the control amount C, for the actuator 46 for driving the exhaust bypass valve 45 is determined.
Calculate. In this case, when BVp>BVs, the control amount Cl-1 for closing the exhaust bypass valve 45 is changed to BVp<B
Calculate Vs (control amount C)l which opens when D and stops when BVp=BVs. Then, in P41, the closing amount control signal SI3 corresponding to this control amount Cl-1 is output to the actuator 46 for driving the exhaust bypass valve 45.

Therefore, the catalyst in the reformer 38 is at a predetermined temperature (e.g.
450° C.) (that is, overheating is prevented) and maintained at a temperature at which liquid fuel can be efficiently reformed into reformed gas.

〔effect〕

According to the present invention, under operating conditions in which both reformed gas and liquid fuel are supplied to the engine, the liquid fuel is injected first,
The reformed gas can be injected after the injection of this liquid fuel is completed, and it is possible to avoid the phenomenon that only the reformed gas is sucked into the cylinder before the liquid fuel, and
The temperature of the reformed gas drawn into the cylinder can be lowered by the vapor of the liquid fuel.

As a result, occurrence of flashback due to the reformed gas can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional fuel injection control device for a reformed gas engine, Fig. 2 is an overall block diagram of the present invention, and Figs.
The figures are diagrams showing one embodiment of the present invention, FIG. 3 is a schematic configuration diagram thereof, FIG. 4 is a configuration diagram showing details of its control unit, and FIG. 5 is a diagram of a program for controlling the intake air-fuel mixture. Flowchart, FIG. 6 is a diagram showing the relationship between the accelerator pedal operation amount and rotation speed, and the temporary load factor, FIG. 7 is a diagram showing the relationship between the temporary load factor and the basic gas fuel consumption, and FIG.
The figure shows the relationship between the provisional load rate and the basic excess air rate.
Fig. 9 is a diagram showing the relationship between the excess air ratio and the air valve opening degree, Fig. 10 is a flowchart of the program that controls the injection of liquid fuel and reformed gas, and Fig. 11 a-
e is a diagram showing a timing chart for explaining the action of the injection control, FIG. 12 is a flowchart of a program that controls the reformer, and FIG. 13 is a diagram showing the relationship between the catalyst temperature and the exhaust bypass valve closing amount. The figure shown in FIG. 14 is a diagram showing the relationship between the rotation speed, the basic injection amount, and the exhaust bypass valve closing amount. 21-------Engine, 32----Engine state detection means, 33---
- Injector (liquid fuel injection means), 34 - Gas valve (reformed gas injection means), 53 - Injection completion detection circuit (injection completion detection means). Patent Applicant Nissan Motor Co., Ltd. Representative Patent Attorney Yuga Army Part Figure 6 Figure 7 A Kawara 9 Jail (Tr.) Figure 8 Figure 9 Kata V Yamato Surrender Section λ No. 10 Figure 11

Claims (1)

[Scope of Claims] A reformed gas engine that uses reformed gas obtained by reforming liquid fuel Nishiki and unreformed liquid fuel by changing the supply amount ratio according to the operating condition of the engine. In the fuel injection control device, liquid fuel injection means for injecting liquid fuel;
A reformed gas injection means for injecting reformed gas, an injection completion detection means for detecting completion of injection of liquid fuel, and an engine state detection means for detecting the operating state of the engine. An injection amount setting means that calculates the injection amount and sets a supply amount ratio of liquid fuel and reformed gas to the fuel injection amount, and a liquid injection signal that drives the liquid fuel injection means in accordance with the liquid fuel supply amount ratio. and injection control means for outputting a gas injection signal that drives the reformed gas injection means in accordance with the gas supply amount ratio when completion of injection of liquid fuel is detected. Fuel injection control device for quality gas engines.