JPS6385238A - Fuel injection device for engine - Google Patents

Abstract

PURPOSE:To suppress the knocking in an engine provided with first and second fuel injection valves at downstream and upstream portions of an air intake passage, respectively, by increasing an injection burden rate of the second fuel injection valve to an entire injection quantity under a predetermined operational condition where the knocking tends to occur. CONSTITUTION:A first fuel injection valve 11 is provided at a downstream position of an air intake passage 5 near a combustion chamber 4, and a second fuel injection valve 12 is provided upstream of the first fuel injection valve 11. Both the injection valves 11 and 12 are controlled by a controller 14. The controller 14 computes a fuel injection quantity according to an intake air quantity signal (a) and an engine speed signal (b), and determines the number of fuel injection valves to be driven according to an engine operational condition to be indicated by an engine load and an engine speed. In driving both the injection valves 11 and 12, an injection burden rate of each injection valve to an entire injection quantity is set, and when a predetermined operational condition where knocking tends to occur is detected, the injection burden rate of the second injection valve 12 is controlled to increase.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a fuel injection device for an engine, and particularly to a fuel injection device for an engine in which two fuel injection valves are disposed at the downstream and upstream portions of an intake passage. Regarding.

(Prior art) In fuel injection engines, for example, Japanese Patent Application Laid-Open No. 57-1
As shown in Japanese Patent No. 57058, it is known that two fuel injection valves are installed in the vicinity of the combustion chamber in the downstream part of the intake passage and on the upstream side thereof. This means that when it is necessary to increase the amount of injection m, such as during a cold start, if you try to cover that amount with just one injection valve downstream of the intake passage, the injection amount is relatively small. This is because delicate control of the injector becomes difficult during operation, and especially in the case of rotary engines, if a large amount of fuel is injected from the injection valve near the combustion chamber, the fuel will not be sufficiently vaporized and atomized. This is because fuel is not absorbed onto the wall of the combustion chamber, causing problems such as oil being washed away. Therefore, two fuel injection valves are arranged in the downstream and upstream parts of the intake passage, and normally the downstream injection valve injects and supplies fuel with high accuracy and responsiveness, and when an increase in fuel quantity is required, In addition to this downstream injection valve, fuel is also injected from the upstream injection valve to ensure the required amount of fuel.

On the other hand, there is a problem in engines that knocking occurs, especially during low-speed, high-load operation.Therefore, in the past, when operating in the above-mentioned range, or when abnormal vibrations of the engine were detected, the spark plug was removed. By retarding (delaying) the ignition timing, knocking is prevented or eliminated at an early stage when it occurs.

(Problems to be Solved by the Invention) By the way, when the ignition timing is retarded to prevent knocking as described above, combustion enters a so-called afterburning state, resulting in a decrease in output and an increase in exhaust temperature. This accelerates thermal deterioration of the exhaust system components, causing a decrease in the durability and reliability of the exhaust system. In particular, in high-octane gasoline engines where the ignition timing is set to the retard side from the beginning for use with high-octane gasoline, knocking is likely to occur when regular gasoline is accidentally injected, causing the ignition timing to is further retarded, and as a result, the above-mentioned adverse effects caused by the rise in exhaust gas temperature become even more significant.

The present invention retards the ignition timing in an engine in which two fuel injection valves are arranged in the downstream and upstream parts of the intake passage by appropriately controlling the injection load ratio of these two fuel injection valves. The purpose of the present invention is to avoid the above-mentioned adverse effects such as thermal deterioration of the exhaust system by avoiding knocking without causing any damage.

(Means for Solving the Problems) That is, as shown in FIG. 1, the engine fuel injection device according to the present invention has a first injector in the downstream portion of the intake passage A near the combustion chamber B and the upstream side thereof. In a configuration in which second fuel injection valves C and D are arranged and the injection amounts from these injection valves C and D are controlled by a signal from injection control means E, a predetermined operating state in which knocking is likely to occur is detected. A predetermined operating state detecting means F is provided, and when the predetermined operating state is detected by the detecting means F, the injection control means E increases the injection burden ratio of the second fuel injection valve to the total injection m. Configure. Here, as a mode of increasing the injection burden rate, when the second fuel injection valve is in a non-injection state, the second fuel injection valve is also injected, that is, when the injection area of the second fuel injection valve is expanded. , 1st. When both the second fuel injection valves C and D are injecting, the amount of injection from the second fuel injection valve may be increased, and in either case, the amount of injection from the first fuel injection valve C decreases. be done. In addition, the operating conditions in which knocking is likely to occur as detected by the predetermined operating condition detection means F include, for example, low rotation and high load operating conditions, abnormal vibration of the engine detected by the vibration sensor, and high-octane gasoline specifications. This may occur when regular gasoline is injected into the engine, or when these conditions are combined.

(Function) According to the above configuration, when in a predetermined operating state where knocking is likely to occur, the second
The injection load rate from the fuel injection valve is increased, but since this injection valve is far from the combustion chamber B, the fuel injected from the valve is sufficiently vaporized before reaching the combustion chamber. It turns out. Then, as the heat of vaporization during the vaporization is taken away from the downstream part of the intake passage A, the intake air in the passage A is cooled, thereby suppressing abnormal ignition in the combustion chamber A, that is, knocking. It turns out.

(Example) Examples of the present invention will be described below. It should be noted that this embodiment concerns an engine using high-octane gasoline.

As shown in Fig. 2, the engine 1 includes intake and exhaust valves 2.3.
An intake passage 5 and an exhaust passage 6 are provided which communicate with the combustion chamber 4 via a A first fuel injection valve (hereinafter referred to as the first injection valve) 11 is located at a position close to the combustion chamber 4 in the downstream part of the engine, and a second fuel injection valve (hereinafter referred to as the second injection valve) 12 is located on the upstream side thereof. are placed respectively.

Note that an exhaust purification device 13 is installed in the exhaust passage 6.

The engine 1 also includes the first and second injection valves 11.
A controller 14 is provided to control the fuel injection amount from the air flow meter 8, and the controller 14 receives an air flow signal a from the air flow meter 8 and an engine rotation speed sensor 15.
When the engine rotation speed signal is received, a vibration signal C is sent from a vibration sensor 16 that is attached to the wall of the engine 1 and detects an abnormality, and a vibration signal C is sent from a vibration sensor 16 that is attached to the wall of the engine 1 and detects abnormality. Gasoline signal R from gasoline sensor 18 that detects gasoline
d is input.

Then, the controller 14, as shown in FIG.
a fuel injection amount calculation circuit 21 that calculates the fuel injection amount from the intake air m per cycle to the combustion chamber 4 based on the air flow rate signal a and the engine rotational speed signal S; The actual engine operating state indicated by the engine load corresponding to the above signal and the engine speed indicated by the signal is compared with a preset injection control map as shown in FIG. An injector drive number determination circuit 22 that determines whether to drive or drive both the first and second injection valves 11.12, and a Load rate setting circuit 23 that sets the injection load rate of the injection valves 11 and 12
These circuits 21 to 23 perform basic injection control.

Further, the above-mentioned air flow m signal a1 engine rotation speed signal 1 vibration signal C and gasoline signal d are input to this controller 14 for jet 1) J control to prevent knocking, and from these signals the engine is controlled. a predetermined operating state detection circuit 24 for determining whether or not the operating state of the second injector 12 is in a predetermined operating state where knocking is likely to occur; A second injection valve load rate increasing circuit 25 is provided to increase the injection load rate of the fuel injection valve.

Next, the specific operation of the injection control by the controller 14 will be explained according to the flowchart shown in FIG.

First, the controller 14 reads various data using signals a-d in step S1 of the flowchart, and
In step S2, fuel injection m is calculated based on the air flow rate signal a and the engine speed signal S. Next, step S
3.1. The engine should be driven depending on which of the fft ranges set in the map in FIG. Set the number of injection valves. In other words, if the injection amount calculated in step S2 belongs to the low-speed, low-load area, the engine is injected from the first injection valve 11, so that the injection amount is high and the high-speed, high-load area is injected from the first injection valve 11. If it belongs to the side territory 1dlI, the first.
The second injection valves 11 and 12 are set to inject separately.

Next, the controller 14 determines in step S4 whether or not the operating state of the engine is in a predetermined state in which knocking is likely to occur, and if it is not in such a state, in step S5 Check the number. If the number set in step S3 is one, or if the operating state belongs to the top area work shown in FIG. 4, the l'JI Di signal e1 is output to the first injection valve 11 in step S6. As a result, the entire injection amount calculated in step S2 is injected from the first injection valve 11 located downstream of the intake passage.

Further, if the operating state belongs to the region (3) in which a 2g injection bottle valve is driven, step Sγ is executed, and the injection amount calculated in step S2 is divided into two equal parts. Second injection valve 11.12
The injection signals e1. Output e2 respectively.

As a result, in the high-speed, high-load region (3) where pre-cooled fuel is required, the first 1. Fuel is injected from both the second injection wells 11 and 12, one by one.

On the other hand, if it is determined in step S4 that the engine is in a predetermined operating state where non-king is likely to occur, specifically, even though the gasoline engine 8d is a high-octane gasoline engine, regular gasoline is being used. In the case where the engine operating state is in the low rotation/high load region shown in Figure 4, or when the vibration signal C indicates the occurrence of abnormal engine imaging, etc. , the controller 14 performs step S
4 to step S8 to increase the injection load rate of the second injection valve 12. In other words, the operating condition is originally
In the case of working in an area where only the injection valve 11 is driven,
When the operating state is such that knocking is likely to occur as described above, a portion of the injection amount is borne by the second injection valve 12 and fuel is injected from both injection valves 11 and 12. ．． In the case where both the second injection valves 11 and 12 are driven in the region (3), if abnormal imaging occurs, etc., the injection amount from the first injection valve 11 is reduced,
The injection amount from the second injection valve 12 is set to be increased by that amount. Then, in step S6, injection signals e1 and e2 are outputted to both injection valves 11 and 12 so as to achieve the injection amount rA thus set.

In this way, when the operating condition of the engine becomes such that knocking is likely to occur, fuel is also injected from the second injection valve 12, or the injection amount is increased. The upstream part of the intake passage 5, that is, the combustion chamber 4
Since the fuel injector 12 is located at a distance from the fuel injection valve 12, the fuel injected from the injection valve 12 is sufficiently vaporized before reaching the combustion chamber 4. During vaporization, the intake air inside the intake passage 5 is cooled by removing heat from inside the intake passage 5, thereby lowering the temperature inside the combustion v4 and preventing abnormal ignition or knocking. It will be suppressed.

It should be noted that the means for detecting the operating state where knocking is likely to occur is not limited to the one shown in the above embodiment, but for example, in the case of a regular gasoline specification engine, a vibration sensor alone may be used, or other detection means may be provided. You can also do this.

(Effects of the Invention) As described above, according to the present invention, the first filter is provided at the downstream and upstream portions of the intake passage. In an engine equipped with a second fuel injection valve, when the operating condition becomes such that knocking is likely to occur, the injection load rate of the second fuel injection valve located upstream of the intake passage is increased, and the fuel is injected from the second fuel injection valve. Since the intake air is cooled by the heat of vaporization of the fuel, knocking can be effectively suppressed without resorting to conventional methods such as retarding the ignition timing of the spark plug. This prevents thermal deterioration of the exhaust system due to an increase in exhaust temperature when retarding the ignition timing, and improves the durability and reliability of the exhaust system.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of the present invention, Figs. 2 to 5 show embodiments of the present invention, and Fig. 2 is a fuel injection control system diagram;
FIG. 3 is a block diagram showing the configuration of the controller, FIG. 4 is a map showing areas of injection control, and FIG. 5 is a flowchart showing specific control operations. , 1... Engine, 5... Intake passage, 11.12.
...-1, 12[tlft■・8″15・”6・11°・8−)9r * i f″*[t[=ffl (”7
'°-meter, rotation speed sensor, vibration sensor, gasoline sensor), 14... injection control means (controller).

Claims (1)

[Claims] (1) Predetermined operating state detection for detecting a predetermined operating state in which knocking is likely to occur in an engine in which a first fuel injector is disposed downstream of the intake passage and a second fuel injector is disposed upstream thereof. A fuel injection device for an engine, comprising: means and injection control means for increasing an injection burden rate with respect to the total injection amount of the second fuel injection valve when the predetermined operating state is detected by the detection means.