JPH0243026B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention includes two systems: a direct injection path for directly injecting gas fuel into the engine, and a premixing path for injecting gas fuel from an intake valve together with intake air. This invention relates to an output control device for a spark ignition engine using gas fuel.

[Conventional technology] In gas-fueled engines, the fuel supply system to the intake pipe found in LPG carburetors is common, and when using fuel such as hydrogen, it has the advantage of being able to operate at ultra-lean levels, but it is difficult to operate under high load. The problem is the occurrence of abnormal combustion and low output. On the other hand, although the direct injection method can overcome the problems of the carburetor method at high loads, it increases combustion irregularities and engine rotational fluctuations during idling and low load operation.

However, if the features of both of these supply methods can be fully utilized, an engine system suitable for gas fuel such as hydrogen can be constructed.

[Problems to be Solved by the Invention] The present invention has been made in consideration of these problems in gas engines. The present invention aims to provide an output control device for a gas engine that takes advantage of the advantages of a two-system supply system of a premixing path in which fuel is taken in from the fuel, and that can fully demonstrate the characteristics of the fuel.

[Means for Solving the Problems] To achieve the above object, the output control device of the present invention uses a gas fuel such as hydrogen gas that is easy to ignite and has a high burning rate, and uses a direct injection route for directly injecting it into the engine. This gas engine is equipped with two systems: a premixing path for inhaling air together with intake air through an intake valve, and is equipped with a control unit that switches the gas fuel supply system depending on the engine load, etc. It is characterized by having a control function that supplies only the premixing path during startup and idling, uses both systems together during low-load operation, and uses only the direct injection path during high-load operation.

[Function] The above output device takes advantage of the features of two gas fuel supply systems: a direct injection path that injects the fuel directly to the engine, and a premixing path that injects it together with intake air from the intake valve. , and the characteristics of the fuel can be fully exhibited.

More specifically, when switching between a direct injection system with a flow rate control valve linked to the accelerator and a premixed system that inhales from the intake valve, the engine speed, the operating status of the starter and idle switch, and the flow rate are Based on the control valve opening data, etc.
The control unit determines the operating state of the engine, such as starting, idling, low load, and high load, and supplies the engine according to the operating state.
Occurrence of abnormal combustion during high-load operation when using a premix system, or irregular combustion during idling and low-load operation when using a direct injection system.
Problems such as engine rotation fluctuations are resolved, and output control is performed that takes advantage of the features of the two-system supply system.

[Example] Hereinafter, specific examples of the present invention will be described in detail.

The present invention is directed to engine systems that use hydrogen gas or other gaseous fuels that are easy to ignite and have a high burning rate, and FIG. 1 shows an embodiment of a gas engine that uses hydrogen gas as fuel.

In the figure, an engine 1 is configured as a 4-cylinder, 4-cycle spark ignition engine that has a dedicated valve that injects hydrogen gas fuel directly into the cylinders.

Hydrogen gas passes through a pressure reducing device 3 from a fuel tank 2 that uses metal hydrides to store hydrogen, and then a direct injection path 4 (direct injection system) that injects it directly into the engine 1, and an intake control valve 6 together with intake air. The premixing path 5 is inhaled through the intake manifold 7 from
(premixing system) is supplied to the engine 1 from two systems.

The direct injection system includes a mechanical flow control valve 11 directly connected to the accelerator 10, an electronic proportional control valve (limiter) 12 that controls the maximum flow rate of fuel, and a cutoff valve 1.
3, which is a route in which the driver can control the output. The accelerator 10 has an idle switch 10a that detects whether or not the accelerator is depressed.
A throttle sensor 10b for detecting the throttle opening is also attached to the flow control valve 11.

On the other hand, the premixing system includes an injector system 15 for controlling the engine speed at a constant level, an auxiliary adjustment system 16, a main system 17 whose negative pressure is sucked into the ventilator section, and an increase system 18.
These are connected to the pressure reducing device 3 via a cutoff valve 20 and a pressure regulator 21. Electromagnetic shutoff valves 13 and 20 provided in each path 4 and 5 are used to switch the gas fuel supply path.

A control unit (hereinafter abbreviated as CU) 25 controls the engine speed N, the operating states of the starter (not shown) and the idle switch 10a, and the throttle opening determined by the throttle sensor 10b provided on the flow control valve 11. detect,
It outputs a control signal corresponding to each operation mode set in the memory of the CU 25 to operate the driving parts of each route.

The CU 25 controls the operations of the necessary parts of the engine system, and the parts controlled by the output from the CU 25 are indicated by arrows extending from the * mark in the figure.

Note that the negative pressure tank 28 of the vacuum pump 27 driven by the engine 1 is connected to the position indicated by the arrow extending from the * mark in the figure, and is driven by negative pressure.

Further, the CU 25 has a map of ignition timing with respect to the rotational speed of the engine 1 and the throttle opening, and controls the ignition timing at the same time as controlling the flow rate.

Next, the details of control in each operation mode by the CU 25 will be explained.

In the "starting mode", first, the cutoff valve 20 of the premixing path 5 opens, and all four systems in that path operate. When the rotation of the engine 1 reaches the set rotation speed or higher, it enters the "idle mode" and the increase system 18
is closed and the remaining three systems keep the engine speed constant.

In this control state, the intake air control valve 31
is open, the intake air control valve 32 is closed, and the intake air amount is not throttled. Therefore, "starting mode"
In the "idle mode", the CU 25 is in charge of all engine control, and the control is performed only by the fuel flow rate. Further, the maximum flow rate of the fuel is desirably set to an excess air ratio of 5 or more in order to prevent backfire.

Next, when the accelerator 10 is stepped on, the idle switch 10a is turned off, and the direct injection system cutoff valve 13 is turned off.
is opened, and hydrogen gas is also supplied from the direct injection path 4. "Low load operation mode" where the pedal is pressed lightly
In this case, both paths 4, 5 operate in combination. However, the injector system 15 of the premixing path 5 stops after the CU 25 determines that the engine speed does not decrease.

Furthermore, when the accelerator 10 is strongly depressed and the CU 25 determines that the CU 25 is in the "high load mode" based on the throttle opening degree and the engine speed, the supply to the premixing path 5 is cut off by the cutoff valve 20. This prevents air-fuel mixture from forming in the intake system during high-load operation.
Flash back during high loads can be prevented, the amount of intake air will not be reduced by the fuel gas, and the specific output will also increase. Furthermore, since the maximum hydrogen gas flow rate at each rotation speed is regulated by the proportional control valve 12,
It also prevents knocking during high loads.

When the accelerator 10 is released for deceleration, the idle switch 10a is first turned on. If the engine speed at this time is higher than the set rotation speed 2500rpm,
All hydrogen supply systems are shut off, resulting in a fuel cut state, and at this time, the intake air control valve 31 is closed, and the engine brake is activated. When decelerating to 2500 rpm or less, the intake throttle and fuel cut are released and the engine enters the above-mentioned "idle mode."

An example of the relationship between fuel flow rate and rotational speed in these controls is shown in FIG. 2.

[Effects of the Invention] According to the output control device of the present invention detailed above, the following effects can be expected.

(1) By using a premixing system for supply during startup and idling, it is possible to perform lean operation by controlling only the hydrogen gas flow rate without throttling the intake air, improving thermal efficiency.

(2) In high-load operation, the in-cylinder injection method improves specific output and prevents abnormal combustion.

(3) By using both methods together at low loads, the premixing method compensates for the uneven combustion of the direct injection method, allowing smooth operation. Furthermore, the premixing method can compensate for the time delay in the amount of hydrogen supplied by the direct injection system during acceleration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a graph illustrating the relationship between fuel flow rate and rotational speed in the control of the present invention. DESCRIPTION OF SYMBOLS 1... Engine, 2... Fuel tank, 4... Direct injection path, 5... Premixing path, 25... Control unit.

Claims (1)

[Claims] 1. Two systems using gaseous fuel such as hydrogen gas that is easy to ignite and has a high burning rate: a direct injection route that injects it directly into the engine, and a premixing route that injects it together with intake air from the intake valve. A gas engine equipped with a gas engine is equipped with a control unit that switches the gas fuel supply system depending on the engine load, etc., and this control unit only supplies fuel through the premixing route during startup and idling, and only supplies fuel through the premixing route during low-load operation. A gas engine output control device characterized by having a control function that uses both the direct injection path and the direct injection path during high-load operation.