Fuel injection system for internal combustion engines

Abstract

To provide an internal combustion engine fuel injection system capable of preventing misfire of an internal combustion engine even when a port injection mode is switched from a port injection mode to an in-cylinder injection mode during operation of the internal combustion engine.SOLUTION: A control device of an internal combustion engine fuel injection system switches between a port injection mode to drive an internal combustion engine with fuel injected through a port injection valve, and an in-cylinder injection mode to drive the internal combustion engine with fuel injected through at least an in-cylinder injection valve. When switching a fuel injection mode from the port injection mode to the in-cylinder injection mode, the control device also causes the internal combustion engine to perform fuel injection through the port injection valve and blank injection injecting fuel through the in-cylinder injection valve at a timing which does not contribute to fuel combustion in the internal combustion engine for a predetermined period before performing fuel injection in the in-cylinder injection mode.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to fuel injection systems for internal combustion engines. [Background technology]

[0002] Patent Document 1 discloses a fuel injection device for an internal combustion engine that includes a port injection valve that injects fuel into an intake port and an in-cylinder injection valve that injects fuel into a combustion chamber, and when the engine is cold, injects fuel from the port injection valve out of the port injection valve and the in-cylinder injection valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-234730 Summary of the Invention [Problem to be solved by the invention]

[0004] In the fuel injection device for an internal combustion engine disclosed in Patent Document 1, during operation of the internal combustion engine with fuel injected from the port injection valve, the nose of the in-cylinder injection valve is heated by heat from fuel combustion, and the temperature of the fuel filled in the nose may rise to a high temperature. When the fuel filled in the nose becomes hot, the fuel density in the nose may decrease or vapor may be generated. In this case, if the fuel injection mode is switched from a port injection mode in which the internal combustion engine is driven by fuel injected from the port injection valve to an in-cylinder injection mode in which the internal combustion engine is driven by fuel injected at least from the in-cylinder injection valve, the decrease in fuel density and the generation of vapor may cause a misfire in the internal combustion engine.

[0005] In view of the above circumstances, at least one embodiment of the present invention aims to provide a fuel injection system for an internal combustion engine that can suppress misfires in the internal combustion engine even when switching from port injection mode to direct injection mode during operation of the internal combustion engine. [Means for solving the problem]

[0006] (1) A fuel injection system for an internal combustion engine according to at least one embodiment of the present invention includes a port injection valve for injecting fuel into an intake port provided in the internal combustion engine, an in-cylinder injection valve for injecting fuel into a combustion chamber provided in the internal combustion engine, and a control device for controlling the port injection valve and the in-cylinder injection valve, the control device being configured to operate the internal combustion engine in a port injection mode by injecting fuel from the port injection valve. from an in-cylinder injection motor that drives the internal combustion engine by injecting fuel from at least the in-cylinder injection valve; Do When switching, The port injection mode is switched to a waste injection mode, and in the waste injection mode, a second injection valve for injecting the fuel from the port injection valve and a second injection valve for injecting the fuel from the direct injection valve at a timing that does not contribute to combustion in the internal combustion engine, the second injection valve being injected until the internal combustion engine has completed a predetermined period of time; When the specified period ends The waste injection When finished, The in-cylinder injection mode Switch to .

[0007] According to the configuration (1) above, when switching from port injection mode to direct injection mode, the control device injects fuel from the port injection valve and performs a throw-off injection, in which fuel is injected from the direct injection valve at a timing that does not contribute to combustion in the internal combustion engine, until the end of a predetermined period of time, and then switches to the direct injection mode after the throw-off injection. This makes it possible to prevent misfires in the internal combustion engine even when fuel injection is switched from port injection mode to direct injection mode while the internal combustion engine is running.

[0008] (2) In some embodiments, in the configuration of (1) above, when the temperature of the internal combustion engine is below a predetermined temperature, the timing at which the device does not contribute to the combustion of the fuel is the exhaust stroke of the internal combustion engine, and when the temperature of the internal combustion engine is equal to or higher than the predetermined temperature, the timing at which the device does not contribute to the combustion of the fuel is the later stage of the combustion stroke of the internal combustion engine.

[0009] According to the configuration (2) above, when the temperature of the internal combustion engine is below a predetermined temperature, fuel is injected from the in-cylinder injection valve during the exhaust stroke of the internal combustion engine, so that the fuel burns downstream of the internal combustion engine and activates the exhaust purification device (catalyst).When the temperature of the internal combustion engine is equal to or higher than a predetermined temperature, fuel is injected from the in-cylinder injection valve at a later stage of the combustion stroke of the internal combustion engine, so that the exhaust purification device (catalyst) provided downstream of the internal combustion engine is prevented from becoming too hot and damage to the catalyst can be prevented.

[0010] (3) In some embodiments, in the configuration described in (1) or (2) above, the port injection valve injects fuel until the end of the predetermined period so as to achieve a corrected air-fuel ratio obtained by correcting the target air-fuel ratio required for the internal combustion engine to the lean side.

[0011] According to the configuration (3) above, the port injection valve injects fuel so as to achieve a corrected air-fuel ratio obtained by correcting the target air-fuel ratio required of the internal combustion engine to the lean side until the internal combustion engine finishes a predetermined period of time, so that oxygen is stored in the exhaust purification device (catalyst) and the fuel (HC) injected by the waste injection can be treated (oxidized).

[0012] (4) In some embodiments, in the configuration of (1) or (2) above, when the internal combustion engine is operating at a low load, the port injection valve injects fuel until the end of the predetermined period so as to achieve a corrected air-fuel ratio obtained by correcting the target air-fuel ratio required for the internal combustion engine to the lean side, and when the internal combustion engine is operating at a high load, the port injection valve injects fuel until the end of the predetermined period so as to achieve the target air-fuel ratio required for the internal combustion engine.

[0013] According to the configuration (4) above, when the internal combustion engine is operating at a low load, the port injection valve injects fuel until the end of a predetermined period so as to achieve a corrected air-fuel ratio obtained by correcting the target air-fuel ratio required for the internal combustion engine to the lean side, so that oxygen is stored in the exhaust purification device (catalyst) and the fuel (HC) injected by the waste injection can be treated (oxidized). Also, when the internal combustion engine is operating at a high load, the port injection valve injects fuel until the end of a predetermined period so as to achieve the target air-fuel ratio required for the internal combustion engine, so that high-load operation of the internal combustion engine can be maintained even when fuel injection is switched from port injection mode to direct injection mode during operation of the internal combustion engine. [Effects of the Invention]

[0014] According to at least one embodiment of the present invention, misfires in the internal combustion engine can be suppressed even when fuel injection mode is switched from port injection mode to direct injection mode while the internal combustion engine is in operation. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram schematically illustrating an internal combustion engine according to an embodiment. [Figure 2] 2 is a block diagram showing the port injection valve and the in-cylinder injection valve shown in FIG. 1, and a control device that controls them. FIG. [Figure 3] 3 is a time chart showing the operation of the port injection valve and the in-cylinder injection valve controlled by the control device shown in FIG. 2, and showing the operation when fuel injection is switched from the port injection valve to the in-cylinder injection valve while the internal combustion engine is operating. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative positions, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0017] Fig. 1 is a diagram that schematically shows an internal combustion engine according to an embodiment. Fig. 2 is a diagram that shows the port injection valve and the in-cylinder injection valve shown in Fig. 1, and a control device that controls them. Fig. 3 is a time chart that shows the operation of the port injection valve and the in-cylinder injection valve controlled by the control device shown in Fig. 2, and is a time chart that shows the operation when fuel injection is switched from the port injection valve to the in-cylinder injection valve during operation of the internal combustion engine.

[0018] As shown in FIG. 1, an internal combustion engine 1 according to this embodiment includes a cylinder block 10 and a cylinder head 12. The cylinder block 10 includes a cylinder 16 in which a piston 14 reciprocates, and a cylinder head 12 is fixed to the cylinder block 10. The cylinder head 12 includes a spark plug 18, and a combustion chamber 20 is formed between the cylinder head 12 and the piston 14. The cylinder head 12 includes an intake port 22 and an exhaust port 24. An exhaust pipe is connected to the exhaust port 24, and an exhaust purification device is provided in the exhaust pipe. The exhaust purification device is, for example, a three-way catalyst. For example, two intake ports 22 and two exhaust ports 24 are provided for each combustion chamber 20, but this is not limited thereto. The intake port 22 includes an intake valve 26 that opens and closes the intake port 22, and the exhaust port 24 includes an exhaust valve 28 that opens and closes the exhaust port 24. The intake port 22 includes a port injection valve 30 that injects fuel into the intake port 22. Furthermore, the cylinder block 10 or the cylinder head 12 is provided with an in-cylinder injection valve 32 for injecting fuel into the combustion chamber 20. These port injection valve 30 and in-cylinder injection valve 32 are controlled by a control device 34, as shown in FIG.

[0019] The control device 34 is composed of a processor (not shown) consisting of an arithmetic unit, registers for storing instructions and information, and peripheral circuits, memories (not shown) such as ROM (Read Only Memory) and RAM (Random Access Memory), and an input interface (not shown).

[0020] The control device 34 can switch between a mode in which the internal combustion engine 1 is driven by fuel injection from the port injection valve 30 (hereinafter referred to as the "port injection mode") and a mode in which the internal combustion engine 1 is driven by fuel injection from at least the in-cylinder injection valve 32 (hereinafter referred to as the "in-cylinder injection mode"). The in-cylinder injection mode may be one in which the internal combustion engine 1 is driven by fuel injection from the in-cylinder injection valve 32 and the port injection valve 30, as long as the internal combustion engine 1 is driven by fuel injection from at least the in-cylinder injection valve 32, or one in which the internal combustion engine 1 is driven by fuel injection from only the in-cylinder injection valve 32.

[0021] As shown in FIG. 3 , when switching from the port injection mode to the in-cylinder injection mode, the control device 34 injects fuel from the port injection valve 30 and performs a waste injection, in which fuel is injected from the in-cylinder injection valve 32 at a timing that does not contribute to combustion in the internal combustion engine 1, until the end of a predetermined period of time in the internal combustion engine 1. After the waste injection, the control device 34 switches to the in-cylinder injection mode. The waste injection, in which fuel is injected from the in-cylinder injection valve 32 at a timing that does not contribute to combustion in the internal combustion engine 1, is referred to as the waste injection mode. Microscopically, switching from the port injection mode to the in-cylinder injection mode can be visualized as switching between the port injection mode, the waste injection mode, and the in-cylinder injection mode in this order. That is, when a command to switch to the in-cylinder injection mode is issued during the port injection mode, the control device 34 switches to the waste injection mode, in which fuel is injected from the port injection valve 30 to maintain the drive of the internal combustion engine 1, while fuel is injected from the in-cylinder injection valve 32 at a timing that does not contribute to combustion in the internal combustion engine 1. After the waste injection mode is performed for a predetermined period of time, the waste injection mode is terminated and the mode transitions to in-cylinder injection mode, in which fuel is injected from the in-cylinder injection valve 32 at a timing that contributes to combustion in the internal combustion engine 1. Note that Fig. 3 illustrates an example of the in-cylinder injection mode in which the internal combustion engine 1 is driven by fuel injection from only the in-cylinder injection valve 32.

[0022] The timing that does not contribute to the combustion of fuel is the timing that is not converted into the rotational torque of the internal combustion engine 1, and is, for example, other than the intake stroke and compression stroke of the internal combustion engine 1.

[0023] The predetermined period can be set arbitrarily, and for example, can be set in units of the number of cycles of the internal combustion engine 1. When the predetermined period is set in units of the number of cycles of the internal combustion engine 1, the predetermined period can be set to be until the internal combustion engine 1 completes the predetermined number of cycles. The predetermined cycle can be set arbitrarily, and can be one cycle or several cycles, for example, two to three cycles.

[0024] The control device 34 injects fuel from the port injection valve 30 so as to achieve a corrected air-fuel ratio obtained by correcting the target air-fuel ratio required for the internal combustion engine 1 to the lean side (lean side) until the end of a predetermined period of time. As a result, the target air-fuel ratio of fuel injection from the port injection valve 30 in the discard injection mode becomes leaner (leaner) than the target air-fuel ratio before switching from the port injection mode to the direct injection mode. In the port injection mode or the direct injection mode, the fuel injection amount is set so as to achieve the target air-fuel ratio set based on the vehicle's running state, etc. When fuel is injected from the port injection valve 30 in the discard injection mode, the fuel injection amount is set so as to achieve a corrected air-fuel ratio obtained by correcting the target air-fuel ratio in the port injection mode immediately before switching to the discard injection mode to the lean side. For example, if the injection time from the port injection valve 30 before the switching command is set to t1 and the injection time after the switching command is set to t2, the air-fuel ratio after the switching command is made leaner than the air-fuel ratio before the switching command by setting the injection time t1 before the switching command > the injection time t2 after the switching command.

[0025] However, when the internal combustion engine 1 is operating under high load, the target air-fuel ratio is not corrected to the lean side until the internal combustion engine 1 has completed a predetermined period of time, and fuel is injected from the port injection valve 30 so as to achieve the target air-fuel ratio required by the internal combustion engine 1. When the internal combustion engine 1 is operating under high load, for example, the vehicle is traveling at high speed (for example, 60 km / h or more), when the vehicle is traveling on an uphill lane, or when the accelerator is depressed to a predetermined level or more.

[0026] Therefore, the port injection valve 30 injects fuel to achieve a corrected air-fuel ratio obtained by correcting the target air-fuel ratio required for the internal combustion engine 1 to the lean side only when the internal combustion engine 1 is operating at a low load (other than when the internal combustion engine 1 is operating at a high load). The low load operation of the internal combustion engine 1 includes, for example, when the internal combustion engine 1 is idling or when the vehicle is operating at a low speed in an urban area.

[0027] It is preferable that the amount of fuel injected from the direct injection valve 32 during the waste injection be as small as possible. For example, the cycle of the internal combustion engine 1 in which fuel is injected from the direct injection valve 32 at a timing that does not contribute to fuel combustion is one cycle.

[0028] Furthermore, the amount of fuel injected from the in-cylinder injection valve 32 at a timing that does not contribute to fuel combustion is the minimum amount that can be injected from the in-cylinder injection valve 32. The minimum amount that can be injected from the in-cylinder injection valve 32 is an amount determined by the performance of the in-cylinder injection valve 32, and is the minimum amount within a range in which the fuel injection amount can be accurately controlled by the in-cylinder injection valve 32. The minimum amount that can be injected from the in-cylinder injection valve 32 may be determined by experiment, or may be determined by calculation from the diameter of the injection port of the in-cylinder injection valve 32, the fuel injection pressure of the in-cylinder injection valve 32, etc. Note that the predetermined period and fuel injection amount when performing a waste injection are not limited to those described above. For example, the predetermined period and fuel injection amount may be set so that all of the high-temperature fuel in the in-cylinder injection valve 32 can be injected.

[0029] The timing at which fuel is injected from the direct injection valve 32 when performing the waste injection may be changed according to predetermined conditions. For example, when the temperature of the internal combustion engine 1 is below a predetermined temperature, the timing at which fuel is injected from the direct injection valve 32 and does not contribute to fuel combustion is the exhaust stroke of the internal combustion engine 1, and when the temperature of the internal combustion engine 1 is equal to or higher than the predetermined temperature, the timing at which fuel is injected from the direct injection valve 32 and does not contribute to fuel combustion is the latter half of the combustion stroke of the internal combustion engine 1.

[0030] For example, the predetermined temperature is the temperature at which a catalyst built into an exhaust purification device provided downstream of the exhaust port 24 is activated. Therefore, for example, when the temperature of the internal combustion engine 1 is below the temperature at which the catalyst is activated, fuel is injected from the in-cylinder injection valve 32 during the exhaust stroke of the internal combustion engine 1, and when the temperature is equal to or higher than the temperature at which the catalyst is activated, fuel is injected from the in-cylinder injection valve 32 during the latter part of the combustion stroke of the internal combustion engine 1.

[0031] According to the fuel injection system for the internal combustion engine 1 according to the embodiment described above, when switching from port injection mode to direct injection mode, the control device 34 injects fuel from the port injection valve 30 and also performs a throw-in injection, in which fuel is injected from the direct injection valve 32 at a timing that does not contribute to combustion in the internal combustion engine 1, until the end of a predetermined period of time in the internal combustion engine 1, and then switches to the direct injection mode after the throw-in injection. This allows high-temperature fuel to be discharged from the direct injection valve 32 when switching fuel injection from the port injection mode to the direct injection mode while the internal combustion engine 1 is operating, thereby preventing misfires in the internal combustion engine 1. At this time, fuel can be discharged from the direct injection valve 32 while maintaining operation of the internal combustion engine 1 by injecting fuel from the port injection valve 30, so the operation of the internal combustion engine 1 is not significantly affected.

[0032] Furthermore, for example, the control device 34 causes the port injection valve 30 to inject fuel so as to achieve a corrected air-fuel ratio that is the target air-fuel ratio required by the internal combustion engine 1 corrected to the lean side until the internal combustion engine 1 completes a predetermined period of time, so that oxygen is stored in the exhaust purification device (catalyst) and the fuel (HC) injected by the waste injection can be processed (oxidized).

[0033] Furthermore, for example, when the internal combustion engine 1 is operating under high load, the control device 34 causes the port injection valve 30 to inject fuel so as to achieve the target air-fuel ratio required for the internal combustion engine 1 until the internal combustion engine 1 has completed a predetermined period of time, so that the high load operation of the internal combustion engine 1 can be maintained even when the fuel injection mode is switched from port injection mode to in-cylinder injection mode while the internal combustion engine 1 is operating.

[0034] Furthermore, for example, the cycle of the internal combustion engine 1 in which fuel is injected from the direct injection valve 32 at a timing that does not contribute to fuel combustion is one cycle, so the amount of fuel wasted from the direct injection valve 32 can be reduced.

[0035] Furthermore, for example, when the temperature of the internal combustion engine 1 is below a predetermined temperature, fuel is injected from the in-cylinder injection valve 32 during the exhaust stroke of the internal combustion engine 1, so that the fuel burns downstream of the internal combustion engine and activates the exhaust purification device (catalyst). Furthermore, for example, when the temperature of the internal combustion engine 1 is equal to or higher than a predetermined temperature, fuel is injected from the in-cylinder injection valve 32 during the latter part of the combustion stroke of the internal combustion engine 1, so that the exhaust purification device (catalyst) provided downstream of the internal combustion engine 1 is prevented from becoming too hot, and damage to the catalyst can be prevented. [Explanation of symbols]

[0036] 1. Internal combustion engine 10 Cylinder block 12 Cylinder head 14 Piston 16 cylinders 18 Spark plug 20 Combustion chamber 22 Intake port 24 exhaust port 26 Intake valve 28 Exhaust valve 30-port injection valve 32 In-cylinder injection valve 34 Control device

Claims

1. a port injection valve for injecting fuel into an intake port provided in the internal combustion engine; an in-cylinder injection valve provided in the internal combustion engine for injecting fuel into a combustion chamber; a control device that controls the port injection valve and the in-cylinder injection valve; Equipped with The control device When switching from a port injection mode in which the internal combustion engine is driven by fuel injection from the port injection valve to an in-cylinder injection mode in which the internal combustion engine is driven by fuel injection from at least the in-cylinder injection valve, switching from the port injection mode to a throw-away injection mode, in which the fuel is injected from the port injection valve and the fuel is injected from the direct injection valve at a timing that does not contribute to combustion in the internal combustion engine, until the internal combustion engine completes a predetermined period of time; A fuel injection system for an internal combustion engine, which switches to the direct injection mode when the predetermined period ends and the waste injection ends.

2. When the temperature of the internal combustion engine is lower than a predetermined temperature, the timing at which the combustion does not contribute to the combustion of the fuel is an exhaust stroke of the internal combustion engine, When the temperature of the internal combustion engine is equal to or higher than the temperature, the timing at which the fuel does not contribute to combustion is a later stage of a combustion stroke of the internal combustion engine.

2. A fuel injection system for an internal combustion engine according to claim 1.

3. the port injection valve injects fuel so as to achieve a corrected air-fuel ratio obtained by correcting a target air-fuel ratio required for the internal combustion engine to the lean side until the end of the predetermined period.

3. A fuel injection system for an internal combustion engine according to claim 1 or 2.

4. During low load operation of the internal combustion engine, the port injection valve injects fuel until the end of the predetermined period so as to achieve a corrected air-fuel ratio obtained by correcting a target air-fuel ratio required for the internal combustion engine to the lean side, During high load operation of the internal combustion engine, the port injection valve injects fuel so as to achieve a target air-fuel ratio required for the internal combustion engine until the end of the predetermined period.

3. A fuel injection system for an internal combustion engine according to claim 1 or 2.

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