JP2020148096A - engine - Google Patents

Abstract

To restrain destabilization of fuel injection.SOLUTION: An engine comprises a main fuel injection part for injecting main fuel to a combustion chamber, a liquid fuel injection part for injecting liquid fuel to the combustion chamber, and a fuel control part for changing an injection ratio of the main fuel and the liquid fuel according to an internal pressure of the combustion chamber. The fuel control part decreases the injection ratio of the main fuel when knocking is detected based on vibration of the internal pressure. Also, the fuel control part decreases the injection ratio of the main fuel, when an average effective pressure derived based on the internal pressure is less than a threshold. Also, the fuel control part is shifted to a two-kind injection mode for injecting the main fuel and the liquid fuel, when variation of an engine rotation number satisfies a predetermined stable condition, in one-kind injection mode for not injecting the main fuel and injecting the liquid fuel.SELECTED DRAWING: Figure 4

Description

This disclosure relates to an engine.

Some engines use high-pressure LPG as the main fuel and inject it directly into the combustion chamber. For example, in the engine described in Patent Document 1, diesel fuel is injected into the combustion chamber as pilot fuel to ignite. As a result, the flame propagates to the high-pressure LPG injected into the combustion chamber.

Special Table 2003-522877

When a main fuel that liquefies at high pressure, such as LPG or ammonia, is used, the area around the injector of the main fuel is cooled by supplying the main fuel. However, if the main fuel supply is stopped due to an engine stop or the like, the temperature around the injector may rise. At this time, if the main fuel is injected, the main fuel may be vaporized before the injection. Then, the fuel injection may become unstable.

In view of such problems, the present disclosure aims to provide an engine capable of suppressing instability of fuel injection.

In order to solve the above problems, the engine according to one aspect of the present disclosure includes a main fuel injection unit that injects main fuel into a combustion chamber, a liquid fuel injection unit that injects liquid fuel into a combustion chamber, and internal pressure in the combustion chamber. It is provided with a fuel control unit that changes the injection ratio of the main fuel and the liquid fuel according to the above.

When an injection abnormality is detected based on the internal pressure, the fuel control unit may reduce the injection ratio of the main fuel.

When knocking is detected based on the vibration of the internal pressure, the fuel control unit may reduce the injection ratio of the main fuel.

The fuel control unit may lower the injection ratio of the main fuel when the average effective pressure derived based on the internal pressure is less than the threshold value.

When the average effective pressure is equal to or higher than the threshold value, the fuel control unit may increase the injection ratio of the main fuel so that the average effective pressure approaches the threshold value.

The fuel control unit is a type injection mode that injects liquid fuel without injecting main fuel, and when the fluctuation of the engine speed satisfies a predetermined stability condition, it shifts to a type injection mode that injects main fuel and liquid fuel. You may.

According to the present disclosure, it is possible to suppress destabilization of fuel injection.

It is a figure which shows the schematic structure of an engine. It is a functional block diagram for demonstrating the control system of an engine. It is a flowchart which shows the control flow of a fuel control part. It is a flowchart which shows the process flow of the 2 type injection mode. It is a figure which shows the relationship between the average effective pressure and a fuel injection amount.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding, and the present disclosure is not limited unless otherwise specified. In the present specification and the drawings, elements having substantially the same function and configuration are designated by the same reference numerals to omit duplicate description. In addition, elements not directly related to the present disclosure are not shown.

FIG. 1 is a diagram showing a schematic configuration of the engine 100. As shown in FIG. 1, the engine 100 includes a cylinder block 102, a cylinder head 104, and a piston 106. A cylinder 102a is formed in the cylinder block 102. The inner peripheral surface of the cylinder 102a may be formed by a cylinder liner (sleeve) press-fitted or cast into the inside of the cylinder block 102. The piston 106 is housed in the cylinder 102a.

The combustion chamber 108 is formed inside the cylinder 102a. The combustion chamber 108 is surrounded by the cylinder block 102 (cylinder 102a), the cylinder head 104, and the crown surface 106a of the piston 106.

An intake port 104a and an exhaust port 104b are formed in the cylinder head 104. The intake port 104a and the exhaust port 104b open into the combustion chamber 108. Air is supplied to the combustion chamber 108 from the intake port 104a. Exhaust gas is discharged from the combustion chamber 108 to the exhaust port 104b. The intake port 104a is opened and closed by the intake valve 110a. The exhaust port 104b is opened and closed by the exhaust valve 110b.

The cylinder head 104 is provided with injectors (main fuel injection unit 112, liquid fuel injection unit 114). The tips of the main fuel injection unit 112 and the liquid fuel injection unit 114 each project into the combustion chamber 108.

The main fuel is ejected from the tip of the main fuel injection portion 112 into the combustion chamber 108. The main fuel is, for example, LPG (Liquefied Petroleum Gas). The main fuel is stored, for example, in a high pressure tank (not shown) in a liquefied state under high pressure. Also, the high pressure tank may be cooled. Further, the main fuel may be any low boiling point fuel used by liquefying at high pressure, and may be, for example, ammonia. Liquid fuel is ejected from the tip of the liquid fuel injection unit 114 into the combustion chamber 108. The liquid fuel is a pilot fuel such as heavy fuel oil A for ignition assistance.

The pressure sensor Sa detects the pressure in the combustion chamber 108. The pressure sensor Sa outputs a signal indicating the pressure of the cylinder 102a to the control device 120 described later. The pressure sensor Sa is provided in, for example, the cylinder block 102. However, the pressure sensor Sa may be provided at another portion such as the cylinder head 104 as long as the pressure in the combustion chamber 108 can be detected.

The engine 100 is, for example, a 4-cycle engine. In the intake stroke, the piston 106 heads for bottom dead center and air flows from the intake port 104a into the combustion chamber 108. In the compression stroke, the piston 106 heads for top dead center. The main fuel and liquid fuel are injected into the air compressed by the piston 106. When the liquid fuel ignites in the combustion stroke, the flame propagates to the main fuel and burns. The combustion pressure in the combustion chamber 108 pushes the piston 106 toward bottom dead center. In the exhaust stroke, the piston 106 heads for top dead center. Exhaust gas is discharged from the combustion chamber 108 through the exhaust port 104b.

FIG. 2 is a functional block diagram for explaining the control system of the engine 100. As shown in FIG. 2, the engine 100 includes the pressure sensor Sa, the crank angle sensor Sb, and the control device 120. Here, the configuration relating to the control of the main fuel injection unit 112 and the liquid fuel injection unit 114 will be mainly mentioned, and other configurations will be omitted.

The crank angle sensor Sb is provided on the crankshaft, for example. The crank angle sensor Sb outputs a signal for identifying the crank angle to the control device 120.

The control device 120 (for example, an ECU (Engine Control Unit)) is composed of a semiconductor integrated circuit including a central processing unit (CPU), a ROM in which a program or the like is stored, a RAM as a work area, and the like, and controls the entire engine 100. To do. The control device 120 also functions as a fuel control unit 122.

The fuel control unit 122 controls the main fuel injection unit 112 and the liquid fuel injection unit 114. The fuel control unit 122 injects the main fuel from the main fuel injection unit 112 at a preset first crank angle in response to a signal from the crank angle sensor Sb. Further, the fuel control unit 122 injects the liquid fuel from the liquid fuel injection unit 114 at the second crank angle set in advance in response to the signal from the crank angle sensor Sb. The first crank angle is different from, for example, the second crank angle.

Further, the fuel control unit 122 changes the injection amount of the main fuel and the injection amount of the liquid fuel by changing the fuel injection period for each of the main fuel injection unit 112 and the liquid fuel injection unit 114. That is, the fuel control unit 122 changes the injection ratio of the main fuel and the liquid fuel.

The fuel injection amount (energy amount of injected fuel, calorific value) is set according to the engine load. However, even with the same engine load, the injection ratio of the main fuel and the liquid fuel is variable. During normal operation (during normal control described later), the liquid fuel is used as a pilot fuel for igniting the main fuel.

At this time, the main fuel injection unit 112 and the piping (not shown) for supplying the main fuel to the main fuel injection unit 112 are cooled by the main fuel. However, when the supply of the main fuel is stopped due to the stop of the engine 100 or the like, the temperature around the main fuel injection portion 112 that is no longer cooled may increase. If the engine 100 is started in this state and the main fuel is injected into the main fuel injection unit 112, the main fuel may vaporize before the injection and the fuel injection may become unstable.

Therefore, the fuel control unit 122 controls the main fuel injection unit 112 and the liquid fuel injection unit 114 to suppress injection abnormality (abnormal combustion). Hereinafter, the control of the fuel control unit 122 will be described in detail with reference to the flowchart.

FIG. 3 is a flowchart showing a control flow of the fuel control unit 122. The process shown in FIG. 3 is repeatedly executed at a predetermined cycle.

(S200)
The fuel control unit 122 determines whether or not it is a kind of injection mode. A type of injection mode is a mode in which liquid fuel is injected without injecting main fuel. That is, the main fuel injection unit 112 is not driven during the type injection mode.

For example, when the engine 100 is started, a kind of injection mode is selected. In one type of injection mode, the main fuel is not used, so injection abnormalities are suppressed. In addition, a kind of injection mode may be selected for other purposes such as measures to avoid injection abnormalities due to the outside air temperature being too high in the tropics or the like.

If it is a kind of injection mode, the process is transferred to S202. If it is not a kind injection mode, the process is transferred to S206.

(S202)
The fuel control unit 122 determines whether or not the fluctuation of the engine speed satisfies a predetermined stability condition. The stabilization condition is, for example, that the deviation of the actual engine speed with respect to the preset speed (for example, idle speed) is smaller than the preset deviation threshold. The engine speed is measured over a plurality of cycles, for example. However, other conditions may be set as stable conditions as long as it can be determined whether or not the engine speed is stable.

If the fluctuation of the engine speed satisfies a predetermined stable condition, the process is transferred to S206. If the fluctuation of the engine speed does not satisfy the predetermined stability condition, the process is transferred to S204.

(S204)
The fuel control unit 122 executes a kind of injection mode. That is, the main fuel injection unit 112 does not inject the main fuel, and the liquid fuel injection unit 114 injects the liquid fuel.

(S206)
The fuel control unit 122 executes the two-kind injection mode. The type 2 injection mode is a mode in which both the main fuel and the liquid fuel are injected. That is, the main fuel injection unit 112 injects the main fuel, and the liquid fuel injection unit 114 injects the liquid fuel. The two-kind injection mode will be described in detail with reference to FIG.

FIG. 4 is a flowchart showing the processing flow of the two-kind injection mode. The process shown in FIG. 4 is performed every preset plurality of cycles (hereinafter referred to as a target period) while the type 2 injection mode is selected. Further, the process shown in FIG. 4 may be performed, for example, triggered by a change in the engine load.

(S300)
The fuel control unit 122 determines whether or not knocking is detected during the target period. Specifically, the fuel control unit 122 passes the waveform of the internal pressure of the combustion chamber 108 through the high-pass filter from the signal from the pressure sensor Sa. In this way, the fuel control unit 122 detects knocking by detecting a momentary change (vibration) in the internal pressure of the combustion chamber 108 that occurs during knocking.

If knocking is detected, the process is transferred to S306. If knocking is not detected, the process is transferred to S302.

(S302)
The fuel control unit 122 determines whether or not the average effective pressure is less than a preset threshold value A. Specifically, the fuel control unit 122 derives the work amount per cycle from the internal pressure and the crank angle of the combustion chamber 108, and divides by the stroke volume to derive the average effective pressure.

FIG. 5 is a diagram showing the relationship between the average effective pressure and the fuel injection amount. In FIG. 5, the vertical axis represents the average effective pressure. The horizontal axis indicates the fuel injection amount. As shown in FIG. 5, a threshold value A and a threshold value B are set for the average effective pressure. The threshold value A and the threshold value B are proportional to the fuel injection amount (that is, the engine load). The threshold B is larger than the threshold A.

When an injection abnormality occurs in the engine 100, the efficiency is lowered and the amount of work is reduced. As a result, the average effective pressure becomes smaller. From this, the fuel control unit 122 determines that an injection abnormality has occurred if the average effective pressure is less than the threshold value A (unstable region). The threshold value A is a lower limit value of the average effective pressure estimated to occur if there is no injection abnormality with respect to the fuel injection amount.

In addition, there is an upper limit of the amount of work that cannot occur with respect to the amount of fuel injection, no matter how efficiently combustion is performed. The threshold value B is the upper limit value of the average effective pressure obtained by dividing the upper limit value of this work amount by the stroke volume. When the average effective pressure is equal to or higher than the threshold value B (sensor abnormality region), the fuel control unit 122 determines that the pressure sensor Sa has an abnormality. In this case, the fuel control unit 122 notifies the abnormality by, for example, an alarm device (not shown).

Further, if the average effective pressure is equal to or more than the threshold value A and less than the threshold value B, the fuel control unit 122 determines that the fuel is in an appropriate region where injection abnormality is unlikely to occur.

Here, examples of the injection abnormality detected at the average effective pressure include premature ignition. If knocking significantly reduces efficiency, knocking is also detected at the average effective pressure.

It is assumed that the ratio of the average effective pressure below the threshold value A in the target period is equal to or more than a preset predetermined ratio. In this case, the fuel control unit 122 determines that the average effective pressure is less than the preset threshold value A for the entire target period.

Further, it is assumed that the ratio of the average effective pressure below the threshold value A in the target period is less than the preset predetermined ratio. In this case, the fuel control unit 122 determines that the average effective pressure is equal to or higher than the preset threshold value A for the entire target period.

In this way, the internal pressure value of the combustion chamber 108 detected over a plurality of cycles is used. Therefore, so-called hunting, in which control is frequently switched across the threshold value, is suppressed.

If the average effective pressure is less than the preset threshold value A, the process is transferred to S306. If the average effective pressure is not less than the preset threshold value A, the process is transferred to S304.

(S304)
Since no injection abnormality has occurred, the fuel control unit 122 raises the injection ratio of the main fuel so that the average effective pressure approaches the threshold value A. The injection ratio of the main fuel is increased by, for example, a preset rate of increase (increase amount). Therefore, the injection amount of the main fuel increases, and the main fuel injection unit 112 is rapidly cooled by the main fuel.

(S306)
Since the injection abnormality has been detected, the fuel control unit 122 lowers the injection ratio of the main fuel. The injection ratio of the main fuel is reduced by, for example, a preset reduction rate (reduction amount). In this way, the injection abnormality is suppressed. Further, the main fuel injection unit 112 is cooled by the main fuel little by little. Therefore, in the later cycle, the transition to S304 is performed, and the injection ratio of the main fuel is gradually increased within a range in which injection abnormality does not occur.

When increasing the injection ratio of the main fuel, the fuel control unit 122 lowers the injection ratio of the liquid fuel so that the calorific value of the injected fuel is the same. Further, when lowering the injection ratio of the main fuel, the fuel control unit 122 raises the injection ratio of the liquid fuel so that the calorific value of the injected fuel is the same.

The above two types of injection modes are divided into transition control and normal control. The transition control is executed when the transition from the type 1 injection mode to the type 2 injection mode is performed. The transition control is a control in which the injection ratio of the main fuel is suppressed and the injection ratio of the liquid fuel is higher than that of the normal control.

When S304 is repeated in the transition control and the injection ratio of the main fuel rises to the upper limit value, the normal control is performed. In normal control, the liquid fuel is used only as a pilot fuel to ignite the main fuel. The amount of liquid fuel injected is minimized.

As described above, the fuel control unit 122 changes the injection ratio of the main fuel and the liquid fuel according to the average effective pressure (that is, the internal pressure of the combustion chamber 108). Therefore, the main fuel is supplied within a range in which the injection abnormality does not occur, and the main fuel injection unit 112 is cooled. As a result, vaporization of the fuel before injection is suppressed. Further, since the fuel control unit 122 controls according to the internal pressure of the combustion chamber 108, injection abnormality can be suppressed with higher accuracy than the control according to other index values.

Although the embodiments have been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to such embodiments. It is clear that a person skilled in the art can come up with various modifications or amendments within the scope of the claims, and it is understood that they also naturally belong to the technical scope.

For example, in the above-described embodiment, the fuel control unit 122 has described a case where the injection ratio of the main fuel is lowered when knocking is detected based on the vibration of the internal pressure of the combustion chamber 108. In this case, knocking can be suppressed. However, the knocking detection process based on the vibration of the internal pressure of the combustion chamber 108 is not an essential configuration.

Further, in the above-described embodiment, the fuel control unit 122 has described a case where the injection ratio of the main fuel is lowered when the average effective pressure derived based on the internal pressure of the combustion chamber 108 is less than the threshold value. In this case, premature ignition can be suppressed. However, the above processing based on the average effective pressure is not an essential configuration.

Further, in the above-described embodiment, the fuel control unit 122 has described a case where the injection ratio of the main fuel is increased so that the average effective pressure approaches the threshold value A. In this case, as described above, the main fuel injection unit 112 is rapidly cooled by the main fuel. However, the process of increasing the injection ratio of the main fuel so that the average effective pressure approaches the threshold value A is not an essential configuration.

Further, in the above-described embodiment, the case where the fuel control unit 122 shifts to the type 2 injection mode when the fluctuation of the engine speed satisfies a predetermined stability condition in the type 1 injection mode has been described. In this case, a kind of injection mode is applied until the engine speed stabilizes, and the injection abnormality is suppressed. However, the transition from the type 1 injection mode to the type 2 injection mode may be triggered by an index other than the stabilization of the engine speed.

Further, in the above-described embodiment, the case where the engine 100 is a direct injection engine has been described. In this case, the combustion efficiency of the engine 100 is improved as compared with the port injection. Further, in the direct injection engine, the temperature of the main fuel injection unit 112 tends to rise as compared with the port injection, so that the cooling effect by the above control is large. However, the engine 100 may perform port injection. That is, the main fuel injection unit 112 may inject the main fuel into the intake port 104a.

The present disclosure can be used for engines.

100 Engine 108 Combustion chamber 112 Main fuel injection unit 114 Liquid fuel injection unit 122 Fuel control unit A Threshold

Claims (6)

The main fuel injection section that injects the main fuel into the combustion chamber,
A liquid fuel injection unit that injects liquid fuel into the combustion chamber,
A fuel control unit that changes the injection ratio of the main fuel and the liquid fuel according to the internal pressure of the combustion chamber.
Engine equipped with. The engine according to claim 1, wherein the fuel control unit reduces the injection ratio of the main fuel when an injection abnormality is detected based on the internal pressure. The engine according to claim 2, wherein the fuel control unit reduces the injection ratio of the main fuel when knocking is detected based on the vibration of the internal pressure. The engine according to claim 2 or 3, wherein the fuel control unit lowers the injection ratio of the main fuel when the average effective pressure derived based on the internal pressure is less than the threshold value. The engine according to claim 4, wherein the fuel control unit raises the injection ratio of the main fuel so that when the average effective pressure is equal to or higher than the threshold value, the average effective pressure approaches the threshold value. The fuel control unit is a type of injection mode in which the liquid fuel is injected without injecting the main fuel, and when the fluctuation of the engine speed satisfies a predetermined stability condition, the main fuel and the liquid fuel are injected. The engine according to any one of claims 1 to 5, which transitions to the injection mode.

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