JP2020045859A - Fuel injection control device and vehicle - Google Patents

Abstract

To provide a fuel injection control device capable of suppressing the exhaustion of unburnt fuel, and provide a vehicle.SOLUTION: The fuel injection control device for controlling the fuel injection amount of an internal combustion engine using an intake valve for which a valve closing timing can be variably set, includes a control part for performing main injection of fuel into the internal combustion engine, and a determination part for, when the valve closing timing is changed over to any timing in the middle of a compression stroke, determining whether to perform or not preliminary injection before the main injection on the basis of the temperature of the internal combustion engine. The control part performs the preliminary injection according to the determination result of the determination part.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a fuel injection control device and a vehicle.

  2. Description of the Related Art Conventionally, in an internal combustion engine, there has been known a configuration in which late closing control for variably setting a closing timing of an intake valve during a compression stroke is performed.

  For example, Patent Document 1 discloses a configuration in which the valve closing timing can be set at two timings later than the normal timing at which the piston position is the bottom dead center position by using two types of cams. In this configuration, when one of the cams is used, pilot injection is performed prior to the fuel injection of the main injection means, and when the other cam is used, control for inhibiting the pilot injection is performed.

JP 2003-97329 A

  By the way, if the valve closing timing is later than the normal timing when the temperature of the internal combustion engine is low, the compression ratio of the internal combustion engine is reduced, so that the ignition timing of the fuel becomes unstable and unburned fuel (carbonized (E.g., hydrogen) increases. In the configuration described in Patent Document 1, the above problem can be prevented when one cam is used, but the above problem may still occur when the other cam is used.

  An object of the present disclosure is to provide a fuel injection control device and a vehicle that can suppress discharge of unburned fuel.

Fuel injection control device according to the present disclosure,
A fuel injection control device for controlling a fuel injection amount of an internal combustion engine in which an intake valve capable of variably setting a valve closing timing is used,
A control unit that performs main injection of fuel into the internal combustion engine,
When the valve closing timing is switched to any timing in the middle of the compression stroke, a determination unit that determines whether to perform preliminary injection before the main injection based on the temperature of the internal combustion engine,
With
The control unit performs the preliminary injection according to a determination result of the determination unit.

The vehicle according to the present disclosure includes:
The above fuel injection control device;
A switching device for switching the valve closing timing of the intake valve,
The internal combustion engine;
A fuel injection device for injecting fuel into the internal combustion engine,
Is provided.

  According to the present disclosure, it is possible to suppress discharge of unburned fuel.

1 is a diagram illustrating an intake and exhaust system of a vehicle to which a fuel injection control device according to an embodiment of the present disclosure is applied. 1 is a block diagram illustrating an internal combustion engine and a fuel injection control device. FIG. 3 is a diagram illustrating a lift amount of an intake valve with respect to a crank angle of an internal combustion engine. FIG. 4 is a diagram for explaining a correspondence relationship between an operation state of the internal combustion engine and a valve closing timing. 5 is a time chart showing a time change of a fuel injection amount, a valve closing timing, an air amount, and an excess air ratio. 5 is a flowchart illustrating an example of an operation of fuel injection control in the fuel injection control device.

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating an intake / exhaust system of a vehicle 1 to which a fuel injection control device 100 according to an embodiment of the present disclosure is applied.

  As shown in FIG. 1, the intake / exhaust system of the vehicle 1 includes an internal combustion engine 10, an intake pipe 20, an exhaust pipe 30, a cooling section 40, a recirculation path section 50, a supercharger 60, and an intake cam. It has a device 70 and a fuel injection control device 100.

  The internal combustion engine 10 is, for example, a diesel engine mounted on the vehicle 1, and is connected to an intake pipe 20 and an exhaust pipe 30. As shown in FIG. 2, the internal combustion engine 10 includes a fuel injection device 11 and a water temperature detection unit 12.

  The fuel injection device 11 is a device that injects fuel of the internal combustion engine 10. The fuel injection device 11 performs main injection for injecting a predetermined amount of fuel into the internal combustion engine 10 after closing an intake valve 21 described below under the control of a fuel injection control device 100 (a control unit 120 described later). The predetermined amount is such an amount that the fuel stably ignites after the intake valve 21 is closed at the normal timing when the piston of the internal combustion engine 10 is located at the bottom dead center.

  The water temperature detector 12 detects the temperature of the cooling water in the internal combustion engine 10.

  As shown in FIG. 1, the intake pipe 20 sucks outside air into the internal combustion engine 10. The intake pipe 20 is provided with an intake valve 21. The intake valve 21 is opened or closed according to the operation of the internal combustion engine 10 under the control of a control unit (not shown).

  The exhaust pipe 30 exhausts exhaust gas generated in the internal combustion engine 10.

  The cooling unit 40 is disposed in the intake pipe 20 and cools outside air in the intake pipe 20 that is compressed by a compressor 61 described later.

  The recirculation path section 50 is a path that branches from the exhaust pipe 30 and recirculates exhaust gas in the exhaust pipe 30 toward the intake pipe 20.

  The recirculation path unit 50 is provided with a recirculation valve 51 for adjusting the flow rate of exhaust gas returned from the exhaust pipe 30 to the intake pipe 20 via the recirculation path unit 50. The recirculation valve 51 adjusts the flow rate of the exhaust gas returned from the exhaust pipe 30 to the intake pipe 20 by making a transition from an open state to a closed state under the control of a control unit (not shown).

  The supercharger 60 has a compressor 61, a turbine 62, and a connection portion 63. The compressor 61 is provided in the intake pipe 20.

  The turbine 62 is provided in the exhaust pipe 30, and a turbine impeller (not shown) is rotated by exhaust gas discharged from the internal combustion engine 10.

  The compressor 61 and the turbine 62 are connected by a connecting portion 63, and a compressor impeller and a turbine impeller (not shown) of the compressor 61 rotate integrally with a rotating shaft (not shown). Thereby, in the compressor 61, the compressor impeller rotates, compresses the outside air sent into the intake pipe 20, and sends it to the internal combustion engine 10.

  The intake cam device 70 is a switching device that switches the valve closing timing of the intake valve 21, and includes a first cam 71, a second cam 72, and a third cam 73. The intake cam device 70 is configured to switch the cam applied to the intake valve 21 to one of the first cam 71, the second cam 72, and the third cam 73. The first cam 71, the second cam 72, and the third cam 73 correspond to “plurality of cams” of the present disclosure.

  The first cam 71, the second cam 72, and the third cam 73 make the closing timing of the intake valve 21 different. That is, the closing timing of the intake valve 21 in each of the first cam 71, the second cam 72, and the third cam 73 is different. FIG. 3 is a diagram illustrating a lift amount of the intake valve 21 with respect to a crank angle of the internal combustion engine 10.

  As shown in FIG. 3, the lift amount of the intake valve 21 in each of the first cam 71, the second cam 72, and the third cam 73 starts to change from when the crank angle is A. The closing timing of the intake valve 21 in the second cam 72 is later than the closing timing of the intake valve 21 in the first cam 71. The closing timing of the intake valve 21 in the third cam 73 is later than the closing timing of the intake valve 21 in the first cam 71 and the second cam 72.

  Each valve closing timing is a timing when the piston of the internal combustion engine 10 is located in any range after the bottom dead center. The timing ranges from a normal timing when the piston is located at the bottom dead center to a timing when the piston is in the middle of the compression stroke of the internal combustion engine 10 after passing through the bottom dead center. Specifically, the valve closing timing by the first cam 71 is a normal timing. The valve closing timing by the second cam 72 and the valve closing timing by the third cam 73 are timings later than the normal timing. That is, in the present embodiment, the valve closing timing can be variably set during the compression stroke.

  Each of the first cam 71, the second cam 72, and the third cam 73 is selected by the intake air amount control device 100 in association with a parameter related to an operation state of the internal combustion engine 10. The operating state of the internal combustion engine 10 includes, for example, the rotation speed of the internal combustion engine 10, the fuel injection amount in the fuel injection device 11, and the like.

  As shown in FIG. 3, the applicable range of the cam is set according to the operating state of the internal combustion engine 10. The application range of the first cam 71, the second cam 72, and the third cam 73 is determined in advance so that the closing timing of the intake valve 21 is delayed. Note that the operation state of the internal combustion engine 10 shown in FIG. 3 is an example, and may be other than the rotation speed of the internal combustion engine 10 and the fuel injection amount in the fuel injection device.

  The applicable range of the first cam 71 is a range where the fuel injection amount is larger than F1 and the rotation speed of the internal combustion engine 10 is less than R1.

  The applicable range of the second cam 72 is a range excluding the applicable range of the first cam 71, in which the fuel injection amount is larger than F2 which is smaller than F1, and the rotational speed of the internal combustion engine 10 is smaller than R2 which is larger than R1. is there.

  The applicable range of the third cam 73 is a range where the fuel injection amount is equal to or less than F2 or the rotational speed of the internal combustion engine 10 is equal to or more than R2.

  Further, the intake cam device 70 is controlled by a control device (not shown) so that any one of the cams is applied to the intake valve 21. The intake cam device 70 may be controlled by the fuel injection control device 100.

  As shown in FIG. 2, the fuel injection control device 100 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an input / output circuit (not shown). The fuel injection control device 100 controls the fuel injection device 11 to control the fuel injection amount in the internal combustion engine 10 based on a preset program. The fuel injection control device 100 includes a determination unit 110 and a control unit 120.

  When the closing timing of the intake valve 21 is switched to a timing later than the normal timing, that is, any timing in the middle of the compression stroke, the determination unit 110 supplies fuel to the internal combustion engine 10 based on the temperature of the internal combustion engine 10. It is determined whether to perform the preliminary injection.

  The temperature of the internal combustion engine 10 is a detection result by the water temperature detection unit 12. The preliminary injection is a fuel injection performed by the fuel injection device 11 before the main injection.

  When the temperature of the internal combustion engine 10 is equal to or higher than the stable combustion temperature, the determination unit 110 determines that the preliminary injection of the fuel to the internal combustion engine 10 is not performed. When the temperature of the internal combustion engine 10 is lower than the stable combustion temperature, the determination unit 110 determines that the preliminary injection of the fuel to the internal combustion engine 10 is performed.

  The combustion stable temperature is a temperature at which the fuel is stably ignited when the fuel is injected into the internal combustion engine 10 by the fuel injection device 11 and unburned fuel is not discharged to the outside, and is a temperature that can be set as appropriate. .

  When the valve closing timing is later than the normal timing, since the intake valve 21 is not closed until the middle of the compression stroke of the internal combustion engine 10, the actual compression starts only when the intake valve 21 is completely closed. And then.

  FIG. 5 is a time chart showing a time change of the temperature of the internal combustion engine 10, the valve closing timing, the number of fuel injections, and the amount of unburned fuel. The uppermost diagram in FIG. 5 is a time chart of the temperature of the internal combustion engine 10. The second diagram from the top in FIG. 5 is a time chart of the valve closing timing. The third diagram from the top in FIG. 5 is a time chart of the number of injections. The lowermost diagram in FIG. 5 is a time chart of the amount of unburned fuel.

  The number of injections in FIG. 5 is the number of fuel injections of the fuel injection device 11. Time T0 in FIG. 5 is a time when the piston of the internal combustion engine 10 is located at the bottom dead center.

  For example, as shown in FIG. 5, when the intake valve 21 is closed at time T1 which is delayed from time T0, compression starts at time T1. FIG. 5 shows an example in which the valve closing timing of the first cam 71 is switched to the valve closing timing of the second cam 72.

  As a result, the compression ratio of the internal combustion engine 10 decreases, so that the ignition timing of the fuel becomes unstable, and a problem arises in that the discharge of unburned fuel increases (see the broken line L1).

  In particular, when the temperature of the internal combustion engine 10 is low, such as when the internal combustion engine 10 is started, the above problem occurs remarkably.

  Therefore, in the present embodiment, when the temperature of internal combustion engine 10 is lower than the stable combustion temperature, determination unit 110 determines that preliminary injection of fuel is to be performed. As a result, since the preliminary injection is performed by the control unit 120 described later, it is possible to eliminate a situation in which the fuel is difficult to ignite and to stabilize the combustion state of the fuel.

  The control unit 120 controls the fuel injection by controlling the number of injections of the fuel injection device 11. Specifically, the control unit 120 controls the fuel injection device 11 to perform the main injection of the fuel into the internal combustion engine 10.

  Then, the control unit 120 controls the fuel injection device 11 to perform the preliminary injection of the fuel to the internal combustion engine 10 according to the determination result of the determination unit 110. More specifically, when the determination unit 110 determines that the preliminary injection is not performed, the control unit 120 controls the fuel control device 11 so as not to perform the preliminary injection. When the determination unit 110 determines that the preliminary injection is not to be performed, the fuel control device 11 is controlled to perform the preliminary injection.

  For example, when the intake valve 21 is closed (time T1), when the temperature of the internal combustion engine 10 is lower than Tw1, the control unit 120 sets the number of fuel injections to N1. Tw1 in FIG. 5 is, for example, a temperature lower than Tw2, which is a stable combustion temperature, and is a temperature that can be set as appropriate.

  Thus, the combustion state of the fuel in the internal combustion engine 10 can be stabilized. As a result, an increase in unburned fuel can be suppressed (see the solid line L2).

  Further, the control unit 120 controls the fuel injection device 11 such that the lower the temperature of the internal combustion engine 10 is, the more the number of injections in the preliminary injection is increased. Specifically, when the temperature of internal combustion engine 10 is lower than Tw1, control unit 120 sets the number of fuel injections to N1 (time T1). When the temperature of the internal combustion engine 10 is equal to or more than Tw1 and less than Tw2, the control unit 120 sets the number of fuel injections to N2 (time T2). N2 times is a number smaller than N1 times. When the temperature of the internal combustion engine 10 is equal to or higher than Tw2, the control unit 120 sets the number of times of fuel injection to 0 (time T3). The number of times of fuel injection in FIG. 5 is the number of times of preliminary injection.

  By doing so, the lower the temperature of the internal combustion engine 10 is, the more the number of times of fuel injection is increased, thereby promoting the stabilization of the combustion state. Further, as the temperature of the internal combustion engine 10 rises, the fuel is easily ignited in the internal combustion engine 10, so the number of fuel injections is reduced with the rise in the temperature of the internal combustion engine 10.

  Further, the control unit 120 starts the preliminary injection at a timing after the intake valve 21 is closed.

  An operation example of the fuel injection control in the fuel injection control device 100 configured as described above will be described. FIG. 6 is a flowchart illustrating an operation example of the fuel injection control in the fuel injection control device 100. The process in FIG. 6 is appropriately executed, for example, when the cam of the intake cam device 70 is switched during the operation of the vehicle 1.

  As shown in FIG. 6, the fuel injection control device 100 determines whether or not the switched cam is a late closing cam (step S101). The late closing cam is a cam whose valve closing timing is later than the normal timing, and is the second cam 72 and the third cam 73 in the present embodiment. If the result of determination is that the cam is not a late closing cam (step S101, NO), this control ends.

  On the other hand, when the cam is a late closing cam (step S101, YES), the fuel injection control device 100 determines whether the temperature of the internal combustion engine 10 is lower than the stable combustion temperature (step S102).

  If the result of the determination is that the temperature is lower than the stable combustion temperature (step S102, YES), the fuel injection control device 100 controls the fuel injection device 11 to perform the preliminary injection (step S103). On the other hand, when the temperature is equal to or higher than the stable combustion temperature (step S102, NO), the fuel injection control device 100 controls the fuel injection device 11 so as not to perform the preliminary injection (step S104). After step S103 or step S104, the present control ends.

  According to the present embodiment configured as described above, when the cam is switched to the late closing cam, the fuel injection device 11 is controlled so as to perform the preliminary injection to the internal combustion engine 10 in accordance with the temperature of the internal combustion engine 10. I do. The combustion state of the fuel can be stabilized. As a result, an increase in unburned fuel can be suppressed.

  In addition, as the temperature of the internal combustion engine 10 is lower, the number of injections in the preliminary injection is increased, so that the combustion state is stabilized.

  When the temperature of the internal combustion engine 10 is equal to or higher than the stable combustion temperature, the preliminary injection is not performed even when the engine is switched to the late closing cam.

  By the way, as in the configuration described in Patent Literature 1, there is known a configuration in which the presence or absence of a preliminary injection (pilot injection) is determined by each of two late closing cams that are switched according to a difference in load. In the case of this configuration, when the temperature of the internal combustion engine 10 decreases in the case of the cam that does not perform the preliminary injection, there is a possibility that a problem that the unburned fuel increases may occur.

  On the other hand, in the present embodiment, since the presence or absence of the preliminary injection is determined based on the temperature of the internal combustion engine 10, it is possible to reliably suppress the increase of the unburned fuel.

  In the above embodiment, the temperature of the cooling water of the internal combustion engine 10 is exemplified as the temperature of the internal combustion engine 10, but the present disclosure is not limited to this, and any temperature that can be regarded as the temperature of the internal combustion engine 10 is applicable. , May be anything. Further, the temperature of the internal combustion engine 10 may be estimated using a parameter capable of estimating the temperature of the internal combustion engine 10.

  Further, in the above embodiment, the main injection and the preliminary injection are performed by the fuel injection device 11, but the present disclosure is not limited to this, and the main injection fuel injection device and the preliminary injection fuel injection device are used. Thus, the main injection and the preliminary injection may be performed.

  In the above-described embodiment, the valve closing timing can be set to a total of three timings, that is, the closing timing of the first cam 71, the closing timing of the second cam 72, and the closing timing of the third cam 73. However, the present disclosure is not limited to this. For example, the valve closing timing may be set to two timings, or may be set to four or more timings.

  Further, in the above-described embodiment, the valve closing timing can be set to a plurality of timings by applying a plurality of cams. However, the present disclosure is not limited to this, and the valve closing timing may be set by other configurations. A plurality of timings may be set.

  Further, in the above-described embodiment, the determination unit 110 and the control unit 120 are configured to be incorporated in the fuel injection control device 100. However, the present disclosure is not limited to this, and the determination unit and the control unit are configured by separate CPUs. An operating configuration may be used.

  In addition, each of the above-described embodiments is merely an example of a specific example in carrying out the present disclosure, and the technical scope of the present disclosure should not be interpreted in a limited manner. That is, the present disclosure can be implemented in various forms without departing from the gist or the main features thereof.

  INDUSTRIAL APPLICABILITY The fuel injection control device according to the present disclosure is useful as a fuel injection control device and a vehicle that can suppress discharge of unburned fuel.

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Internal combustion engine 11 Fuel injection device 12 Water temperature detection unit 20 Intake pipe 21 Intake valve 30 Exhaust pipe 40 Cooling unit 50 Recirculation path unit 51 Recirculation valve 60 Supercharger 61 Compressor 62 Turbine 63 Connection unit 70 Intake cam device 71 first cam 72 second cam 73 third cam 100 fuel injection control device 110 determination unit 120 control unit

Claims (9)

A fuel injection control device for controlling a fuel injection amount of an internal combustion engine in which an intake valve capable of variably setting a valve closing timing is used,
A control unit that performs main injection of fuel into the internal combustion engine,
When the valve closing timing is switched to any timing in the middle of the compression stroke, a determination unit that determines whether to perform preliminary injection before the main injection based on the temperature of the internal combustion engine,
With
The control unit performs the preliminary injection according to a determination result of the determination unit,
Fuel injection control device. The determination unit includes:
If the temperature of the internal combustion engine is equal to or higher than the stable combustion temperature, it is determined that the preliminary injection is not performed,
When the temperature of the internal combustion engine is lower than the stable combustion temperature, it is determined to perform the preliminary injection,
The fuel injection control device according to claim 1. The controller increases the injection amount in the preliminary injection as the temperature of the internal combustion engine is lower,
The fuel injection control device according to claim 1 or 2. The control unit controls the injection of the fuel by controlling the number of injections of the fuel injection device,
The fuel injection control device according to claim 1. The control unit starts the preliminary injection at a timing after the intake valve is closed,
The fuel injection control device according to claim 1. The timing set as the valve closing timing is a position in the middle of the compression stroke of the internal combustion engine after the piston has passed through the bottom dead center from the timing when the piston of the internal combustion engine is located at the bottom dead center. Included in the range up to the timing,
The fuel injection control device according to claim 1. A fuel injection control device according to any one of claims 1 to 6,
A switching device for switching the valve closing timing of the intake valve,
The internal combustion engine;
A fuel injection device for injecting fuel into the internal combustion engine,
Vehicle equipped with. A water temperature detection unit that detects a temperature of cooling water of the internal combustion engine,
The determination unit determines whether to perform the preliminary injection based on a detection result of the water temperature detection unit,
The vehicle according to claim 7. The switching device has a plurality of cams that vary the valve closing timing of the intake valve,
The vehicle according to claim 7 or claim 8.

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