JPS621399Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to the improvement of an air-fuel ratio control circuit for an engine that uses dual fuels (gaseous fuel and liquid fuel) at the same time. The present invention relates to an air-fuel ratio control circuit that can maintain good output efficiency of the engine by improving its performance.

In a diesel engine that uses gaseous fuel as the main fuel and liquid fuel as the auxiliary fuel (for example, used as an ignition source), in order to obtain good combustion conditions in the entire load range, the amount of gaseous fuel and the amount of air must be adjusted. Strict control of the air-fuel ratio is required. This is because the flammability limit of gaseous fuel is generally within a very narrow range, and one of the circuits for performing this kind of control has conventionally been to detect the exhaust temperature and determine the amount of air supply (hereinafter simply referred to as A circuit that centrally controls the amount of air (referred to as "supply air amount") is adopted. The inventor of the present invention also previously applied for a control circuit as shown in FIG.
and an exhaust control temperature calculator 18 is connected to the detector 17, while an exhaust temperature detector 15a is connected to the exhaust section of the engine, and the exhaust temperature detector 15a and the exhaust control temperature calculator 18 are connected to the exhaust section of the engine. 18 is connected to a comparison output device 19, and the comparison output device is used to control the air supply amount in the air supply system 4 of the engine via the fluid pressure control valve 30 and slider crank mechanisms 31a, 32 of the fluid equipment 31. By connecting the valve 8a, changes in the supply air temperature T ₀ are interpreted as an error from the ideal state of the exhaust temperature (that is, the theoretical exhaust temperature Tg'), and the supply air amount is adjusted so that the error becomes zero. We have already filed an application for a control circuit that efficiently improves the control performance of the air-fuel ratio by controlling the increase or decrease of .

However, even with the above-mentioned control circuit, sufficient air-fuel ratio control cannot always be obtained in a moderate or lower load range. As a result of various studies on the causes of this, we found that in the medium load range or below, the exhaust temperature changes greatly depending on the load factor value, as shown in Figure 2. It has been found that under the air-fuel ratio control circuit that is not taken into consideration, sufficient control performance is not exhibited as far as the region affected by the load factor (that is, the load region below the medium level) is concerned.

Therefore, in order to solve these problems, the inventor of the present invention conducted further intensive studies, and found that the exhaust gas temperature associated with a decrease in the load factor was calculated in advance with respect to the theoretical exhaust temperature The theoretical exhaust temperature Tg'' obtained here is used as the temperature control element by making corrections that take the decrease in temperature into consideration, and changes in the supply air temperature To are understood as an error from the corrected theoretical exhaust temperature Tg''. By controlling the increase/decrease of the air supply amount so that the error becomes zero, it has become possible to perform air-fuel ratio control satisfactorily even in the medium or lower load range, and the present invention has been completed.

Therefore, the air-fuel ratio control circuit of the present invention includes a supply air temperature detector provided at the outlet of the air cooler in the air supply system of the dual fuel engine, and a load factor detector provided in the fuel supply system of the engine. Further, both of these detectors are connected to exhaust control temperature calculators, while an exhaust temperature detector is connected to the exhaust section of the engine, and the exhaust temperature detector and the exhaust control temperature calculator are connected to a comparison output device. Along with connecting,
The gist is that the comparison output device is connected to the air supply amount control valve in the air supply system of the engine via the fluid pressure control valve and the slider crank mechanism of the fluid equipment.

Embodiments of the present invention will be described below based on the drawings (FIG. 3). In FIG. 3, 1 is a dual fuel diesel engine (hereinafter simply referred to as the "engine"), and 2 and 3 are gas fuel pipes and liquid fuel pipes connected to the engine 1, respectively. Further, 4 is an air piping system, in which air is sent into the engine 1 via a main pipe 5, an air flow rate measuring nozzle 6, a supercharger 7 (including a bypass pipe 8), an air cooler 9, and an air supply pipe 11. It's becoming like that. Further, a supply air temperature detection sensor 17a is attached to the supply air pipe 11. On the other hand, 2 is a gaseous fuel pipe, and the gaseous fuel is sent into the engine 1 through a gaseous fuel flow rate measuring nozzle 13, and a load factor detector is provided in the middle of the pipe 2.
As the load factor detector, for example, a detector using a method of measuring the amount of movement of an injection adjustment rack in a fuel injection pump is suitable, but the present invention is not limited thereto. Furthermore, liquid fuel is sent into the engine 1 from the liquid fuel pipe 3 via a suitable control valve (not shown). Note that an exhaust gas temperature detection sensor 15a is connected to the exhaust pipe 14 of the engine 1.

Now, if an abnormality occurs in the supply of gaseous fuel, which is the main fuel, for some reason and the air-fuel ratio changes, and the change in exhaust temperature is confirmed by the exhaust temperature detector 15,
The air-fuel ratio is corrected again by continuously controlling excess or deficiency of the amount of air supplied to the engine 1 (that is, optimally controlling the amount of air supplied to the amount of gaseous fuel at that time),
Operations are performed to maintain normal operation of the engine 1. In this case, the amount of air supplied to the engine 1 is controlled by adjusting the internal pressure of the air supply pipe 11, and the adjustment is made by adjusting the internal pressure of the air piping system 4. This is done by bypassing the air inside from the outlet side of the supercharger 7 to the inlet side. The amount of bypass air is controlled by adjusting the opening degree of a flow control valve 8a provided in the bypass pipe 8.
The opening degree is adjusted by the control circuit shown below.

That is, the supply air temperature To is detected by the supply air temperature detector 17 through the temperature detection sensor 17a, and then sent to the exhaust control temperature calculator 18, where the calculator 18 calculates the theoretical exhaust temperature Tg' corresponding to the actual supply air temperature To. At the same time, the load factor of the engine 1 detected by the load factor detector 20 is sent to the exhaust control temperature calculator 18, so especially in the medium or lower load region, the load factor of the engine 1 detected by the load factor detector 20 is calculated. The corrected theoretical exhaust temperature Tg'' is calculated by further performing a correction calculation that takes into account the decrease in exhaust temperature due to a decrease in the load factor as shown in Fig. 2. Meanwhile, the exhaust temperature Tg of the engine 1 is detected by the exhaust temperature detector 15 through the exhaust temperature detection sensor 15a attached to the exhaust pipe 14, and then
It is sent to the comparison output device 19. Therefore, the supply air temperature To
changes, the comparison output device 19 calculates the deviation Δ between the corrected theoretical exhaust temperature Tg'' and the actual exhaust temperature Tg.
Tg (ΔTg = 1Tg'' - Tg1) is immediately compared and corrected (calculation of increase or decrease in supply air amount corresponding to change in exhaust gas temperature), and the calculated value is transmitted to the output section 19' as a constant current control signal.Output The control signal leaving the section 19' is transmitted to the hydraulic cylinder 31 via the solenoid valve 30.
Since the amount of bypass air is adjusted by opening and closing the flow rate control valve 8a in the bypass pipe 8, the amount of air supply is controlled so as to obtain the optimum air-fuel ratio.

The present invention is constructed as described above, but the key point is that in the region where the exhaust temperature is affected by the load factor (i.e., in the region below the medium range), the reduction in the exhaust temperature as the load factor decreases is taken into account in advance. The theoretical exhaust temperature Tg'' obtained through correction is adopted as the temperature control element, and changes in the supply air temperature To are understood as an error from the corrected theoretical exhaust temperature Tg'', and the error becomes zero. By controlling the increase/decrease of the intake air amount in a similar manner, it is possible to improve the air-fuel ratio control performance of the dual fuel diesel engine even in the medium-low load range, and to maintain the engine's output efficiency at a good level. Summer.

[Brief explanation of the drawing]

Fig. 1 shows an air-fuel ratio control circuit in a conventional dual-fuel diesel engine, Fig. 2 is an explanatory diagram of the relationship between engine load factor and exhaust temperature, and Fig. 3 shows an air-fuel ratio control circuit in the same engine according to the present invention. are shown respectively. DESCRIPTION OF SYMBOLS 1... Dual fuel diesel engine, 2... Gaseous fuel piping, 3... Liquid fuel piping, 4... Air piping system, 5... Air main pipe, 8a... Flow rate control valve, 1
1...Air supply pipe, 15...Exhaust temperature detector, 17...
...Supplement air temperature detector, 18...Exhaust control temperature calculator, 19...Comparison output device, 20...Load factor detector.

Claims (1)

[Scope of utility model registration request] A supply air temperature detector is provided at the outlet of the air cooler in the air supply system of the dual fuel engine, and a load factor detector is provided in the fuel supply system of the engine, and both of these detectors are connected to an exhaust control temperature calculator. An exhaust temperature sensor is connected to the exhaust section of the engine, and the exhaust temperature sensor and the exhaust control temperature calculator are connected to a comparison output device, and the comparison output device is connected to a fluid An air-fuel ratio control circuit for a dual fuel engine, characterized in that the air-fuel ratio control circuit is connected to an air supply amount control valve in an air supply system of the engine via a pressure control valve and a slip crank mechanism of a fluid device.