JPS60178939A - Fuel injection control device in reformed gas engine - Google Patents

Abstract

PURPOSE:To control the air excessive rate of an engine with a higher degree of accuracy, by providing a pressure compensating coefficient computing means for computing the pressure compensating coefficient of the engine in accordance with a true gas pressure, and a gas injection amount compensating means for compensating the basic gas injection amount of the engine. CONSTITUTION:There is provided a gas pressure sensor E between a reformer A for reforming liquid fuel into gas and a gas injection valve C. A basic fuel injection amount computing means F computes a basic gas injection amount in accordance with the operating condition of the engine. Further there are provided a pressure compensating coefficient computing means I for computing a pressure compensating coefficient in accordance with a true gas pressure which is computed by a means for computing the pressure of a fuel injection valve section H and a gas injection amount computing means J for computing the basic gas injection amount in accordance with the pressure compensating coefficient and a drive output means K for delivering a drive pulse signal to the gas injection valve C. With this arrangement the amount of gas fuel injection may be controlled with a high degree of accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to a fuel injection control device for a reformed gas engine that supplies reformed gas obtained by reforming liquid fuel to the engine.

Conventional technology By heating liquid fuel such as alcohol through a catalyst, it can be reformed into a flammable gas consisting mainly of hydrogen and carbon oxide, resulting in higher thermal efficiency and better efficiency than when alcohol etc. are directly combusted. Since the exhaust characteristics can be improved,
Reformed gas engines that use this reformed gas alone or in combination with unreformed liquid fuel are attracting attention.

In this reforming waste engine, a reformer that uses exhaust gas as a heat source is generally adopted in order to recover engine exhaust heat, and the efficiency of the reformer can be controlled by adjusting exhaust bypass. By controlling the amount of liquid fuel supplied, the reforming reaction is controlled according to the operating conditions.
Naturally, it is impossible to stably supply reformed gas at a constant pressure to the gas injection valve from the viewpoint of responsiveness and the like.

Therefore, in order to deal with such pressure fluctuations and ensure the desired fuel injection amount, conventionally, LP! j Kaisho 52-11,
As described in Publication No. 3426, a method was adopted in which the pressure of the reformed gas generated by a pressure regulator was adjusted to a constant pressure in advance, but it was not possible to effectively control the reformed gas in operating regions with low reforming performance such as during warm-up. In recent years, a method has been considered in which a pressure sensor is installed in the reformed gas flow path and the gas injection #Um of the gas injection valve is corrected according to the detected pressure (for example, Patent application 1986-7030
No. 9).

However, even in this method of correcting the gas injection amount based on the detected pressure, the gas pressure sensor detects the gas injection: j?
Unless it is installed immediately before the gas pressure sensor, there will be pressure loss in the piping downstream of the gas pressure sensor, and even though it is measuring the true pressure of the reformed gas metered by the gas injection valve, Therefore, when attempting to control the VC2 air excess rate with high accuracy, it becomes a relatively large source of error. Above all,
A gas cutoff valve is usually provided between the gas injection valve and the reformer to prevent gas leakage when the engine is stopped, and the gas pressure during warm-up when the gas cutoff valve is closed is In order to monitor changes using the gas pressure sensor, the gas pressure sensor must be placed upstream of the gas cutoff valve. As a result, the mounting position of the gas pressure sensor is inevitably located away from the jet injection valve, and the pressure loss caused by the gas cutoff valve is also added, resulting in a large error.

Purpose of the Invention The present invention was made in view of the above-mentioned conventional problems, and its purpose is to eliminate the influence of pressure loss in the piping downstream of the pressure sensor and the gas cutoff valve, and to reduce the amount of reformed gas. The object of the present invention is to enable more accurate correction of the injection amount in response to pressure fluctuations.

Structure of the Invention The fuel injection control system for a reformed gas engine according to the present invention, as shown in FIG. It was set up in
and a gas injection valve C that is intermittently opened and closed by a drive pulse signal synchronized with engine rotation, a gas cutoff valve installed between the reformer A and the gas injection valve C, and the gas cutoff valve. a gas pressure sensor E provided upstream of the valve D;
Accelerator operation amount a, intake air flow, engine speed c
Basic 1 to calculate the basic gas injection amount per engine revolution or per injection according to the engine operating conditions such as
a gas flow calculation means F, a gas flow calculation means G for calculating the gas flow rate per unit time from the basic gas injection amount and the engine rotational speed, and a gas flow calculation means G for calculating the gas flow rate per unit time from the gas basic injection amount and the engine rotational speed; Calculate the pressure loss at the gas injection valve and gas cutoff valve, and correct the gas pressure detected by the gas pressure sensor E by the amount of pressure → loss to determine the true gas pressure at the gas injection valve C. Injection valve pressure a calculation means H; a pressure correction coefficient calculation means H for calculating a pressure correction coefficient based on this true gas pressure;
a gas injection type correction means J that corrects the basic gas injection amount using the pressure correction coefficient; and a drive output means that outputs a drive pulse signal to the gas injection valve C in accordance with the corrected gas injection amount. In this configuration, the difference between the gas pressure detected by the gas pressure sensor E and the true gas pressure at the gas injection valve C is estimated from the gas flow rate as described above,
This allows the detected gas pressure to be corrected (thereby, the gas injection amount can be controlled even more precisely as a hydraulic flow loss).

Embodiments FIGS. 2 to 4 show an embodiment in which the present invention is applied to a reformed gas engine in which reformed gas and unreformed liquid fuel are used together depending on the operating condition.

In Figure 2, J is the engine, 2 is its intake passage, 3
indicates an exhaust passage, and the intake passage 2 includes a throttle valve 4.
A solenoid valve type gas injection valve 5 is installed downstream of the intake boat, and a solenoid valve type liquid fuel injection valve 6 is also installed near the intake boat. Note that 7 is an air flow meter for detecting the intake air lid, 8 is an air cleaner, and 9 is an accelerator operation amount sensor. In addition, a reformer 10 is provided in the exhaust passage 3, and the amount of exhaust gas flowing through the reformer IO is controlled by an exhaust bypass valve 12 whose opening degree is controlled by a negative pressure actuator 11. ing. surface,"
Reference numeral 3 designates a solenoid valve that controls negative pressure supplied from a negative pressure source to the actuator 11.

14 is a fuel tank for storing liquid fuel, such as alcohol, and a constant pressure pump 15. It is connected to the fuel inlet a of the reformer 10 via a liquid fuel passage 18 in which a flow rate control solenoid valve 16 and a check valve 17 are interposed, and is connected to the fuel inlet a of the reformer 10 upstream of the flow rate control solenoid valve 16. It is connected to the liquid fuel injection valve 6 via the injection passage branched at [9]. 2() is a return fuel passage.

Gas outlet 1 from which the gas reformed in the reformer 10 is taken out. Ob is a gas passage 2 in which a gas cooler 21 is interposed.
2 to the gas injection valve 5, and the gas passage 22 includes a gas pressure sensor 23 downstream of the gas cooler 21, and a gas cutoff valve 24 further downstream.
are interposed respectively. -1=The gas cooler 21 performs heat exchange between the engine cooling water and the reforming residue,
A cooling water temperature sensor 25 detects whether or not the engine cooling water is defective.

Further, 26 is a crank angle sensor provided in the distributor 27 to detect the rotation speed of the engine 1;
is a catalyst temperature sensor that detects the catalyst temperature in the reformer 10, and the control unit 29c controls the gas injection valve 52g based on the signals from these sensors 7, 9, 23, 25, 26 and Akara. , body fuel injection valve 6, flow control valve 16, etc.

As shown in FIG. 3, the control unit 29 includes an MPU (central processing unit) 31, a ROM 32 in which programs for controlling the MPU 31 and predetermined data are written, and temporarily stores external data. R.A.
M33 and a process 10 for processing input signals and output signals.
It is composed of 34. Incidentally, this control unit 29 also controls the ignition timing.

It performs idle rotation speed control, etc., and various sensors and actuators for this control are also connected to A.

To briefly explain the control of the fuel supply amount performed by the control unit 29, first, reformed gas has excellent fuel efficiency and exhaust characteristics, and unreformed liquid fuel has excellent output characteristics, so it is possible to control engine operation. Appropriate gas injection amounts and liquid fuel injection amounts are calculated depending on the conditions, and corresponding opening times of the gas injection valves 5 and liquid fuel injection valves 6 are set. The driving pulse signals for the gas injection valve 5 and the liquid fuel injection valve 6 are outputted at the same or consecutive timing every 101 revolutions of the engine, respectively, and the ON time is set as above for the valve opening. corresponds to time. Here, in the liquid fuel injection valve 6, the fuel pressure is kept constant by the constant pressure pump 15, so the weight flow rate of the fuel is almost exactly proportional to the valve opening time, but in the gas injection valve 5, Since the pressure and temperature of the injected reformed gas are unstable, corrections are made as described below.

On the other hand, the amount of reformed gas produced by the reformer 10 is controlled by adjusting the amount of liquid fuel supplied by a magnetic valve 16 for flow rate control according to the injection amount of the gas injection valve 5. At the same time, the opening degree of the C exhaust bypass valve 12 is controlled via the electromagnetic valve 13 so as to keep the catalyst temperature of the reformer 10 within the optimum temperature range for reforming.

FIG. 4 shows the opening time of the gas injection valve 5 at the above-mentioned pressure and
i1i when setting with temperature correction added! This is a flowchart showing control element control, and first, at (3), the accelerator operation AS, engine rotation speed N, and intake beam airflow fit Qa are detected by the accelerator operation amount sensor 9. Crank angle sensor 26
．． Read from each output signal of the air flow meter 7, and determine the optimal gas-based water injection Je'T based on these conditions in
pG. Calculate. This basic gas injection amount T is the reference pressure per one engine revolution, that is, GQ.
' indicates the injection amount at C1. Next, in (2), the gas flow rate GQ Gg per unit time is determined from the gas basic 1 contribution JiT as Gg-Tpo0×19. ■So,
The waste pressure rice actually detected by the gas pressure sensor 23.

and the cooling water width TW detected by the cooling water volume sensor 25 are input. Next, in step 2), the true gas pressure pg at the one-member injection valve 5 is calculated using the relational expression Pg = PgO-K, Gg. Here, KGg is gas, a valve 24
This shows the pressure loss due to the gas pressure sensor 2.3 downstream of the gas pressure sensor 2.3, and the coefficient is given in advance based on actual tests.

That is, by adding correction according to the gas flow rate Gg to the actually detected gas pressure PgovC, errors due to differences in the detection positions are removed.

Then, based on the true gas pressure Pg corrected as described above, the pressure correction coefficient Kp is determined as KpG=τ- in (2).

In this embodiment, the gas temperature Tg is determined indirectly from the temperature TV of the engine cooling water flowing through the waste cooler 21. In other words, the gas cooler 21 uses engine cooling water to cool the reformed gas of about 30'C sent from the reformer 10 to around 100"C, but the gas temperature after this cooling is Figure 5 shows an example of I-f, which has a correlation with cooling water temperature and gas flow rate.
Now, from the data table given in advance, look up the gas Q degree T g that corresponds to the gas flow rate Gg determined in ■ and the cooling water temperature TW input in ■, and correct the flooding from this gas temperature & Tg273 + Tg in ■ Let the relation g31KT be KTG=273.

Then, the pressure correction coefficient KpQ r set as above in ■
From the temperature correction coefficient KTG and the gas injection valve flow rate correction coefficient Kv and battery voltage correction Ts as other corrections, -TIG=TpG0×KvXKpGxKT.

+TIl], the opening time of the gas injection valve 5 is determined by the following relational expression.

Effects of the Invention As is clear from the above explanation, the fuel injection control device for a reformed gas engine according to the present invention does not require the provision of a gas pressure sensor immediately before the gas injection valve. Errors can be eliminated and more accurate nitrogen excess rate control can be achieved.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a configuration explanatory diagram showing an embodiment of the invention, FIG. 3 is a configuration explanatory diagram of the control unit, and FIG. 4 is a diagram showing the configuration of the control unit. The flowchart, FIG. 5, is a diagram showing the correlation among reformed gas temperature, cooling water wetness, and reformed gas flow rate. ]... Engine, 5... Gas injection valve, 6... Liquid fuel injection valve, 7... Air flow meter, 9... Accelerator operation amount sensor, 10 Reformer, 12 Exhaust bypass valve, 14
...Fuel tack, 16...d magnetic valve for flow layer control, 2J...
Gas cooler, 2: (Gas pressure sensor, 24...Gas cutoff valve, 25...Cooling water TW sensor, 20...Crank sensor, 28...M medium temperature [sensor, 29 Control unit.

Claims (1)

[Claims] (1) A reformer that reformes liquid fuel into hydrogen-rich gas;
A gas injection valve that is installed in the engine intake system and is intermittently opened and closed by a drive pulse signal synchronized with engine rotation, and a gas cutoff valve that is interposed between the reformer and the gas injection valve. , a gas pressure sensor provided upstream of the gas cutoff valve, a basic injection amount calculating means for calculating a basic gas injection amount according to the operating state of the engine, and a basic injection amount calculating means based on the basic gas injection amount and engine rotation speed. A gas flow rate calculation means for calculating the gas flow rate per unit time, and an injection unit that calculates the pressure loss from the gas flow meter, corrects the gas pressure detected by the gas pressure sensor, and calculates the true gas pressure at the gas injection valve. "valve pressure calculation means; pressure correction coefficient calculation means for calculating a pressure correction coefficient based on the true gas pressure; and gas injection for correcting the basic gas injection amount using the pressure correction coefficient":
A fuel injection control device for a reformed gas engine, comprising a correction means and a drive output means for outputting a drive pulse signal to the gas injection valve in accordance with the corrected gas injection amount.