JPS59141755A - Method and apparatus for controlling gas diesel engine - Google Patents

Abstract

PURPOSE:To lower the specific fuel consumption of a gas diesel engine in which liquid fuel is supplied to a combustion chamber from a nozzle and mixture gas of gas fuel and combustion air is supplied to the combustion chamber from an intake valve, by controlling the timing for opening and closing the intake valve and an exhaust valve according to the calorific value of gas fuel. CONSTITUTION:Liquid fuel is supplied from a nozzle 4 to a combustion chamber 3 of a diesel engine 1, and at the same time, mixture gas of gas fuel from a conduit 5 and combustion air from a passage 6 is also supplied to the combustion chamber 3 from an intake valve 7. The liquid fuel is supplied to a nozzle 4 of a liquid fuel injection valve 12 via a pump 16, a pressure accumulator 17 and a passage 15, and a valve element 19 driven by a double acting cylinder 18 is provided at an intermediate portion of the passage 15. With such an arrangement, a solenod valve 21 for controlling the double acting cylinder 18, a solenoid valve 25 for controlling a double acting cylinder 24 for driving an exhaust valve 8, and a gas valve 28 are controlled by a processing circuit 29, for instance, to increase the overlap period of the exhaust valve 8 and the intake valve 7 at the time of low-load operation of the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method and apparatus for a diesel gas engine that can use both liquid fuel and gas fuel.

Such a diesel gas engine can perform full load operation when using only one liquid fuel and no gas fuel, and can also perform light load operation when using both gas fuel and ignition liquid fuel. It is necessary to be able to Therefore, in order to increase the supply flow rate of liquid fuel, the valve hole of the fuel injection valve facing the combustion chamber is relatively large. Conventionally, this liquid fuel is pumped by a cam connected to a crankshaft, and the liquid fuel from this pump is supplied to a fuel injection valve. Therefore, at low speed and low load, the injection pressure of liquid fuel becomes low. In particular, when gas fuel and liquid fuel are used together, the amount of liquid fuel supplied becomes even smaller, so that it may be injected into the combustion chamber without fogging, causing irregular ignition.

To solve this problem, conventional methods have had to supply a relatively large amount of liquid fuel, enough to atomize and inject it into the combustion chamber, resulting in high liquid fuel costs. Ta.

Further, in a conventional four-stroke diesel gas engine, the intake valve and the exhaust valve are configured to have a uniquely determined mechanical interlock with each other by a cam connected to the crankshaft. Therefore, for example, when the load is light or when the calorific value changes depending on the composition of the gas fuel, the optimum air-fuel ratio cannot be freely achieved, and the combustion chamber becomes unstable, causing abnormally high temperature parts of the combustion chamber members. I had something to do. This also applies to two-stroke diesel gas engines.

As a countermeasure to this, during light loads, the combustion air from the supercharger is discharged into the exhaust passage via a bypass path. '2 Optimal air fuel #:! There is also a way to obtain e. However, discharging air from the supercharger to the outside in this way wastes power.

An object of the present invention is to eliminate these problems of the prior art, and to provide a control method and apparatus for a diesel gas engine that reduces fuel consumption and efficiently achieves an optimal air-fuel ratio. It is to be.

Conventionally, diesel gas engines that use gas fuel that tends to knock depending on the type of gas fuel, that is, the knocking characteristics of the gas fuel, are set at a lower compression pressure. It has a structure that cannot be changed. Therefore, when only liquid fuel is used, the compression ratio is too small, resulting in poor combustion conditions and, therefore, a reduction in output.

Another object of the present invention is to provide a control method and apparatus for a diesel gas engine that can change the compression ratio.

FIG. 1 is an overall system diagram of a control device for a four-stroke diesel engine according to an embodiment of the present invention.

Combustion chamber 3 formed by cylinder 1 and piston 2
Liquid fuel is supplied from a nozzle 4 to the fuel tank.

A gas mixture of gaseous fuel from a pipe line 5 and combustion air from a flow path 6 is guided into the combustion chamber 3 via an air supply valve 7. Combustion gas from the combustion chamber 3 flows from the exhaust valve 8 to the flow path 9.
It is then discharged. This combustion gas flows from the flow path 9 to the supercharger 1
0 turbine 26, which drives the propeller 11. Combustion air is forced into the flow path 6 by the blower 11 .

FIG. 2 is a system diagram showing the liquid fuel injection valve 12 having the nozzle 4 and the exhaust valve 8. In the liquid fuel injection valve 12 , a needle valve 14 is urged toward the nozzle 4 by a spring 13 . The liquid fuel passes from the pump 16 to the pressure accumulator 17,
It is supplied from the flow path 15 toward the nozzle 4 . In the middle of the flow path 15, there is a valve body 1 driven by a double-acting cylinder 18.
9 is provided. Pump 20 to this double acting cylinder 18
The pressure oil from is switched and supplied by a solenoid valve 21.

The valve body 22 of the exhaust valve 8 is biased by a spring 23 in the valve closing direction. This valve body 22 is driven by a double-acting cylinder 24. Pressure oil from the pump 20 is supplied to the double-acting cylinder 24 via a solenoid valve 25 . The air supply valve 7 and the gas valve 28 as the second on-off valve also have the same configuration as the exhaust valve 8.

The solenoid valve 21 associated with liquid fuel injection valve 12, the solenoid valve 25 associated with the exhaust valve 8, and similar solenoid valves associated with the air supply valve 7 and gas valve 28 are operated by a processing circuit 29 including a microcomputer and the like. controlled by signals from.

FIG. 3 is a diagram for explaining the operation of the processing device 29 of the embodiment shown in FIG. 1. When the piston 2 moves from the bottom dead center to the top dead center, the gaseous fuel and combustion air in the combustion chamber 3 are compressed.

Near top dead center, cylinder 1 of liquid fuel injection valve 12
The piston 8 moves to the left in FIG. Fuel is atomized and injected. This causes an explosion. When the piston 2 reaches the bottom dead center and rises again, the exhaust valve 8 first
opens and combustion gas is discharged into the flow path 9. Next, air supply valve 7
is opened, combustion air from the flow path 6 is supplied to the combustion chamber 3, and exhaust gas is pushed out from the combustion chamber 3. When the piston passes the top dead center, the gas valve 28 is opened, thereby supplying combustion air and gas fuel to the combustion chamber 3 via the air supply valve 7.

In the above-mentioned embodiment, since pressure oil is supplied to the double-acting cylinder 18.24 for control, the solenoid valve 21.25 can be made smaller and the valve body can be reliably controlled to open and close using a large force. I can do it.

In order to return the valve body 22 of the exhaust valve 8 to the closed state, in the embodiment shown in the second figure, not only pressure oil but also a spring 23 is used.
may be omitted, or the valve body 22 may be returned only by the force of the spring 23.

Since the liquid fuel from the pump 16 is supplied to the liquid fuel injection valve 12 via the pressure accumulator 1-7, the high-pressure liquid fuel can be stored at a constant pressure at all times, so that it can be injected from the nozzle 4. The liquid fuel can be reliably atomized even if the injection amount is small. Therefore, when liquid fuel is used in combination with gas fuel, there is no need to unnecessarily increase the amount of liquid fuel consumed for ignition, which is advantageous from a cost perspective.

The pump 16 may be driven by an electric motor or alternatively by a cam connected to the crankshaft of the diesel gas engine.

Due to the operation of the processing circuit 29, for example, when (&) the load is light or (b) the calorific value of the gas fuel via the gas valve 28 is small, the overlap period 1 between the exhaust valve 8 and the air supply valve 7 is
'1ljW1 (see Figure 3) is increased.

At this time, combustion air supplied from the blower 11 of the supercharger 10 is always supplied to the flow path 6. Therefore, this combustion air can sufficiently cool the combustion chamber 3 and the exhaust valve 8, and when the exhaust valve 8 is opened, the combustion air can quickly exhaust the exhaust gas in the combustion chamber 3. This makes it possible to achieve the optimum air-fuel ratio and maintain good operating conditions.

In the embodiment described above, the solenoid valves 21 and 25 apply pressure oil to the liquid fuel injection valve 12 and the exhaust valve 8 to control the opening and closing of the liquid fuel injection valve 12 and the exhaust valve 8. The injection valve 12 and the exhaust valve 8 may be constituted by electromagnetic valves, and the electromagnetic valves may be controlled by the processing circuit 29. This also applies to the air supply valve 7 and the gas valve 28.

The invention can also be implemented in connection with a two-stroke diesel gas engine. In the two-stroke diesel gas engine, the intake valve 7 is omitted, and the other configurations are the same as in the previous embodiment.

As described above, according to the present invention, in a four-stroke diesel gas engine, the intake valve and the exhaust valve are controlled based on signals from the processing circuit, and therefore the intake valve and the exhaust valve are simultaneously opened. The wrap period can be easily varied.

Therefore, for example, when the load is light or when the calorific value of the gas fuel is small, the overlap period can be greatly controlled to prevent the occurrence of localized abnormally high temperature areas near the combustion chamber. In addition, combustion air can be constantly supplied without being throttled, so the combustion chamber can be cooled, and the exhaust gas in the combustion chamber can be quickly released from the exhaust valve, achieving an optimal air-fuel ratio. In addition to being able to
It becomes possible to maintain good operating conditions. In addition, since a pressure accumulator is used to supply high-pressure liquid fuel, atomization can be achieved reliably even if the flow rate of the liquid fuel is small, which prevents unnecessary consumption of a large amount of liquid fuel. It is better from a fuel consumption point of view. 2
Cycle diesel gas engines can also control the duration and times that the exhaust valves are open and achieve similar effects to those described above.

Further, according to the present invention, in a four-stroke diesel gas engine, the compression ratio can be changed by changing the opening/closing timing of the intake valve. Therefore, it is possible to achieve good combustion conditions without causing knocking by using gas fuels with different knocking characteristics, and it is also possible to burn liquid fuel at a high compression ratio instead of gas fuel, increasing output. be able to.

[Brief explanation of drawings]

FIG. 1 is an overall system diagram of an embodiment of the present invention, FIG. 2 is a system diagram related to the liquid fuel injection valve 12 and exhaust valve 8, and FIG. 3 is an operation of the embodiment shown in FIG. 1. Figure 1 is for explaining. 3... Combustion chamber, 4... Nozzle, 7... Air supply valve, 8
...Exhaust valve, 10...Supercharger, 12...Liquid fuel injection valve, 21.25...Solenoid valve, 29...Processing circuit agent Patent attorney Kei Nishi Part Figure 3 dIPI11 Picture 2 of the send-off

Claims (5)

[Claims] (1) Liquid fuel is supplied to the combustion chamber from the nozzle, a mixture of gaseous fuel and combustion air is introduced into the combustion chamber through the intake valve, and combustion gas from the combustion chamber is guided through the exhaust valve. drain,
The air supply valve and the exhaust valve are controlled based on an electric signal from a processing circuit, or the valve opening/closing timing of the air supply valve and the exhaust valve is controlled according to the calorific value of the gas fuel. A method of controlling a 4-stroke diesel gas engine. (2) Liquid fuel is supplied to the combustion chamber from the nozzle, a mixture of gas fuel and combustion air is introduced into the combustion chamber, and combustion gas from the combustion chamber is discharged through the exhaust valve, which is connected to the processing circuit. 1. A method for controlling a two-stroke diesel gas engine, characterized in that the timing of opening and closing of an exhaust valve is controlled based on an electric signal from the engine, and the timing of opening and closing of an exhaust valve is controlled at light load or in accordance with the calorific value of gas fuel. (3) Liquid fuel is guided from the pump through the pressure accumulator and the first on-off valve to the nozzle and into the combustion chamber, and gas fuel is guided through the second on-off valve to the combustion chamber along with combustion air via the air supply valve. , an exhaust valve for guiding exhaust gas from the combustion chamber is provided, and the first and second on-off valves, the air supply valve and the exhaust valve are controlled based on an electric signal from a processing circuit. Control device for diesel gas engine. (4) The first and second on-off valves, the air supply valve, and the exhaust valve are driven by pressure oil, and this pressure oil is supplied and cut off by a solenoid valve that responds to an electric signal from a processing circuit. A control device for a diesel gas engine according to claim 3. (5) The diesel gas engine according to claim 3, wherein the first and second on-off valves, the intake valve, and the exhaust valve are electromagnetic valves that respond to electrical signals from a processing circuit. Control device.