JP2012219633A - Device and method for controlling start of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an art of performing prompt and better start of an internal combustion engine.SOLUTION: A start control device for an in-cylinder direct-injection type internal combustion engine having a fuel injection valve arranged inside a cylinder is provided with a fuel property detecting means for detecting a property of a fuel injected from the fuel injection valve, a valve controlling means for controlling an opening and closing timing of an intake valve and an exhaust valve to create a period with both intake and exhaust valves closed during a period from exhaust stroke to intake stroke, and a first injection controlling means for injecting fuel from the fuel injection valve during a period created by the valve controlling means with both of the intake and exhaust valves closed. The valve controlling means changes the created period with both intake and exhaust valves closed, based on the property of the fuel detected by the fuel property detecting means.

Description

  The present invention relates to an internal combustion engine start control device and an internal combustion engine start control method.

  In the first fuel injection cycle at the start of the internal combustion engine at cryogenic temperature, the exhaust valve is brought into a small operating lift or completely stopped, and the ignition is stopped to bring the fuel into the next cycle. A technique for increasing the in-cylinder fuel amount is disclosed (for example, see Patent Document 1). According to this, the in-cylinder fuel amount at the start can be increased without increasing the fuel injection rate even at low fuel pressure, and the vaporized fuel amount can also be increased. At that time, it is not necessary to use a special fuel pump or injection valve, and the cost does not increase.

JP-A-10-009004 JP 2010-025073 A

  However, in the technique of the above-mentioned Patent Document 1, the number of cycles until the initial ignition at the start of the internal combustion engine increases, and eventually the time required for the start increases.

  An object of the present invention is to provide a technique for better starting an internal combustion engine in a short time.

In the present invention, the following configuration is adopted. That is, the present invention
A start control device for a direct injection type internal combustion engine having a fuel injection valve disposed in a cylinder,
Fuel property detection means for detecting the property of fuel injected from the fuel injection valve;
Valve control means for controlling the opening and closing timing of the intake valve and the exhaust valve so as to create a period in which both the intake valve and the exhaust valve are closed during the period from the exhaust stroke to the intake stroke;
First injection control means for injecting fuel from the fuel injection valve during a period in which both the intake valve and the exhaust valve created by the valve control means are closed;
With
The start control device for an internal combustion engine, wherein the valve control means changes a period during which both the intake valve and the exhaust valve to be created are closed based on the fuel property detected by the fuel property detection means. It is.

  Here, the fuel property refers to the alcohol concentration (ethanol concentration) of the fuel, etc. If the property is different, the fuel evaporation characteristic with respect to the in-cylinder temperature and the amount of fuel required for combustion differ. .

  In the present invention, fuel is injected from the fuel injection valve during a period in which both the intake valve and the exhaust valve are closed during the period from the exhaust stroke to the intake stroke. If a period in which both the intake valve and the exhaust valve are closed at this timing is provided, the gas remaining in the cylinder is recompressed due to the rise of the piston, and the in-cylinder temperature rises. Therefore, fuel can be injected into the hot cylinder, and fuel evaporation can be promoted.

  Here, when the fuel properties are different, the fuel evaporation characteristics with respect to the in-cylinder temperature and the amount of fuel required for combustion differ, so that the in-cylinder temperature for promoting the evaporation of fuel having different properties varies. That is, in the case of a fuel property in which the fuel evaporation characteristics with respect to the in-cylinder temperature deteriorate, or in the case of a fuel property in which the amount of fuel required for combustion increases, the in-cylinder temperature needs to be further increased. In order to further increase the in-cylinder temperature, it is necessary to advance the closing timing of the exhaust valve so as to increase the amount of gas to be recompressed. Therefore, in order to realize the optimum in-cylinder temperature for the fuel properties, the period during which both the intake valve and the exhaust valve to be created are closed is changed based on the fuel properties. According to the present invention, it is possible to adjust the period during which both the intake valve and the exhaust valve are closed so as to realize the in-cylinder temperature optimum for the properties of the fuel, and it is possible to promote the evaporation of the fuel. As a result, the fuel whose evaporation is promoted can be burned well by ignition in the cycle. Since the fuel burns well in this manner, stable startability can be ensured, and unburned HC is hardly generated, and deterioration of exhaust emission can be suppressed. Therefore, the internal combustion engine can be started better in a short time.

In the present invention, the following configuration is adopted. That is, the present invention
A start control device for a direct injection type internal combustion engine having a fuel injection valve disposed in a cylinder,
Fuel property detection means for detecting the property of fuel injected from the fuel injection valve;
Valve control means for controlling the opening and closing timing of the intake valve and the exhaust valve so as to create a period in which both the intake valve and the exhaust valve are closed during the period from the exhaust stroke to the intake stroke;
First injection control means for injecting fuel from the fuel injection valve during a period in which both the intake valve and the exhaust valve created by the valve control means are closed;
With
The first injection control means changes an injection parameter of fuel to be injected during a period in which both the intake valve and the exhaust valve are closed based on the fuel property detected by the fuel property detection means. An internal combustion engine start control device.

  Here, the fuel property refers to the alcohol concentration (ethanol concentration) of the fuel, etc. If the property is different, the fuel evaporation characteristic with respect to the in-cylinder temperature and the amount of fuel required for combustion differ. . The fuel injection parameters are variables that can be changed at the time of fuel injection, such as the fuel injection amount, the number of fuel injection divisions, and the fuel injection timing.

  In the present invention, fuel is injected from the fuel injection valve during a period in which both the intake valve and the exhaust valve are closed during the period from the exhaust stroke to the intake stroke. If a period in which both the intake valve and the exhaust valve are closed at this timing is provided, the gas remaining in the cylinder is recompressed due to the rise of the piston, and the in-cylinder temperature rises. Therefore, fuel can be injected into the hot cylinder, and fuel evaporation can be promoted.

Here, when the fuel properties are different, the fuel evaporation characteristics with respect to the in-cylinder temperature and the amount of fuel required for combustion differ, so that the evaporation of fuel having different properties with respect to the increased in-cylinder temperature is promoted. The fuel injection parameters will be different. That is, in the case of fuel properties where the fuel evaporation characteristics with respect to the predetermined in-cylinder temperature deteriorate, or in the case of fuel properties in which the amount of fuel required for combustion increases at the predetermined in-cylinder temperature, the predetermined in-cylinder temperature is adjusted It is necessary to change the fuel injection parameters to further promote fuel evaporation. For example, in order to promote the evaporation of fuel at a predetermined in-cylinder temperature, it is necessary to increase the fuel injection amount, increase the number of fuel injection divisions, or advance the fuel injection timing. Therefore, in order to realize the optimum fuel injection parameters for the fuel properties and the in-cylinder temperature determined by the period during which both the intake valve and the exhaust valve are closed, the intake valve and the The injection parameters of the fuel to be injected during the period when both exhaust valves are closed are changed. According to the present invention, the fuel injection parameter is adjusted so as to realize the optimum fuel injection parameter for the fuel property and the in-cylinder temperature determined by the period during which both the intake valve and the exhaust valve are closed. Can evaporate the fuel. As a result, the fuel whose evaporation is promoted can be burned well by ignition in the cycle. Since the fuel burns well in this manner, stable startability can be ensured, and unburned HC is hardly generated, and deterioration of exhaust emission can be suppressed. Therefore, the internal combustion engine can be started better in a short time.

  It is preferable to further include second injection control means for injecting fuel from the fuel injection valve after elapse of a period in which both the intake valve and the exhaust valve are closed.

  According to the present invention, the amount of fuel that can promote evaporation can be injected by the first injection control means, and the remaining amount of fuel necessary for combustion can be injected by the second injection control means. Therefore, evaporation of fuel can be promoted.

  The ratio between the amount of fuel injected by the first injection control unit and the amount of fuel injected by the second injection control unit may be changed based on the fuel property detected by the fuel property detection unit.

  According to the present invention, the ratio of the amount of fuel necessary for combustion can be changed so that the amount of fuel that can promote evaporation can be injected by the first injection control means based on the properties of the fuel. . Therefore, evaporation of fuel can be promoted.

  The valve control means creates a period in which both the intake valve and the exhaust valve are closed, and sets a period from the closing timing of the exhaust valve to the intake top dead center from the intake top dead center to the opening of the intake valve. It is better to make it smaller than the period until the time.

  According to the present invention, negative pressure is generated in the cylinder between the intake top dead center and the intake valve opening timing, and during the period exceeding the intake top dead center period from the exhaust valve closing timing. In this state, the intake valve is opened. Thereby, the boiling under reduced pressure can be performed by injecting the fuel in a state where the negative pressure is generated. Further, by opening the intake valve in a state where negative pressure is generated, the flow velocity of the intake air flowing into the cylinder becomes close to the speed of sound, and this kinetic energy can increase the gas temperature in the cylinder. That is, by increasing the gas temperature in the cylinder, the in-cylinder temperature can be further increased after a period in which both the intake valve and the exhaust valve are closed. Therefore, evaporation of fuel can be promoted.

  Based on the fuel property detected by the fuel property detection means, the valve closing timing for the intake bottom dead center of the intake valve that has been opened after the passage of both the intake valve and the exhaust valve is changed. Good.

  When the closing timing of the intake valve approaches the intake bottom dead center, the gas temperature in the cylinder during the compression stroke is increased due to an increase in the effective engine compression ratio due to the low engine speed at the start. be able to. Thus, according to the present invention, by changing the valve closing timing with respect to the intake bottom dead center of the intake valve that has been opened after the passage of the period during which both the intake valve and the exhaust valve are closed, The in-cylinder temperature can be further changed after the period in which both are closed. Therefore, if the closing timing of the intake valve is optimally changed based on the properties of the fuel, the evaporation of the fuel can be promoted.

In the present invention, the following configuration is adopted. That is, the present invention
A method for starting control of an in-cylinder direct injection internal combustion engine having a fuel injection valve disposed in a cylinder,
The valve control means controls the opening and closing timing of the intake valve and the exhaust valve so as to create a period in which both the intake valve and the exhaust valve are closed during the period from the exhaust stroke to the intake stroke. Fuel is injected from the fuel injection valve during a period in which both the intake valve and the exhaust valve created by the valve control means are closed by the control means,
A period in which both the intake valve and the exhaust valve created by the valve control unit are closed based on the fuel property detected by the fuel property detection unit that detects the property of the fuel injected from the fuel injection valve; and A starting control method for an internal combustion engine, wherein the first injection control means changes at least one of an injection parameter of fuel injected during a period in which both the intake valve and the exhaust valve are closed.

  Here, the fuel property refers to the alcohol concentration (ethanol concentration) of the fuel, etc. If the property is different, the fuel evaporation characteristic with respect to the in-cylinder temperature and the amount of fuel required for combustion differ. . The fuel injection parameters are variables that can be changed at the time of fuel injection, such as the fuel injection amount, the number of fuel injection divisions, and the fuel injection timing.

  In the present invention, fuel is injected from the fuel injection valve during a period in which both the intake valve and the exhaust valve are closed during the period from the exhaust stroke to the intake stroke. If a period in which both the intake valve and the exhaust valve are closed at this timing is provided, the gas remaining in the cylinder is recompressed due to the rise of the piston, and the in-cylinder temperature rises. Therefore, fuel can be injected into the hot cylinder, and fuel evaporation can be promoted.

  Here, when the fuel properties are different, the fuel evaporation characteristics with respect to the in-cylinder temperature and the amount of fuel required for combustion differ, so that the in-cylinder temperature for promoting the evaporation of fuel having different properties varies. That is, in the case of a fuel property in which the fuel evaporation characteristics with respect to the in-cylinder temperature deteriorate, or in the case of a fuel property in which the amount of fuel required for combustion increases, the in-cylinder temperature needs to be further increased. In order to further increase the in-cylinder temperature, it is necessary to advance the closing timing of the exhaust valve so as to increase the amount of gas to be recompressed. Or, if the fuel properties are different, the fuel evaporation characteristics with respect to the in-cylinder temperature and the amount of fuel required for combustion differ, so the fuel for promoting the evaporation of fuel having different properties with respect to the increased in-cylinder temperature The injection parameters will be different. That is, in the case of fuel properties where the fuel evaporation characteristics with respect to the predetermined in-cylinder temperature deteriorate, or in the case of fuel properties in which the amount of fuel required for combustion increases at the predetermined in-cylinder temperature, the predetermined in-cylinder temperature is adjusted. It is necessary to change the fuel injection parameters to further promote fuel evaporation. For example, in order to promote the evaporation of fuel at a predetermined in-cylinder temperature, it is necessary to increase the fuel injection amount, increase the number of fuel injection divisions, or advance the fuel injection timing. Therefore, in order to realize the optimum in-cylinder temperature for the fuel property, the period during which both the intake valve and the exhaust valve to be created are closed is changed based on the property of the fuel, or the property of the fuel, In order to achieve optimal fuel injection parameters for the in-cylinder temperature determined by the period during which both the intake and exhaust valves are closed, both the intake and exhaust valves are closed based on the properties of the fuel. The injection parameter of the fuel injected during the period was changed. According to the present invention, it is possible to adjust the period during which both the intake valve and the exhaust valve are closed so as to realize the in-cylinder temperature optimum for the properties of the fuel, and it is possible to promote the evaporation of the fuel. Alternatively, the fuel injection parameters can be adjusted to achieve the optimal fuel injection parameters for the fuel properties and the in-cylinder temperature determined by the period during which both the intake and exhaust valves are closed. , Fuel evaporation can be promoted. As a result, the fuel whose evaporation is promoted can be burned well by ignition in the cycle. Since the fuel burns well in this manner, stable startability can be ensured, and unburned HC is hardly generated, and deterioration of exhaust emission can be suppressed. Therefore, the internal combustion engine can be started better in a short time.

  According to the present invention, the internal combustion engine can be started better in a short time.

1 is a diagram illustrating a schematic configuration of an internal combustion engine according to Embodiment 1 of the present invention. It is a figure which shows the opening / closing timing of the intake valve and exhaust valve by the special start control and normal start control which concern on Example 1. FIG. It is a figure which shows the in-cylinder temperature with respect to the ethanol density | concentration of the fuel which concerns on Example 1, and the evaporation rate of a fuel. It is a figure which shows the fuel-injection time of the special start control which concerns on Example 1, and normal start control. It is a figure which shows the relationship between the valve closing timing of the exhaust valve which forms the both-valve closing period based on Example 1, and in-cylinder temperature. It is a figure which shows the fuel-injection time of the special starting control in the case of the 2 split fuel injection which concerns on Example 1. FIG. 3 is a flowchart illustrating a special start control routine 1 according to the first embodiment. It is a figure which shows the opening / closing timing of the intake valve and exhaust valve which concern on the modification 1. FIG. It is a figure which shows the relationship between difference (theta) i- (theta) e which concerns on the modification 1, and in-cylinder temperature. It is a figure which shows the relationship between the valve closing timing of the intake valve which concerns on the modification 2, and cylinder temperature. It is a figure explaining the case where the fuel injection parameter in a both valve closing period is changed by increasing the division | segmentation number of the fuel injection in the both valve closing period which concerns on Example 2 to two. The figure explaining the case where the fuel quantity injected in the double stroke valve closing period is increased, the fuel quantity injected in the compression stroke is reduced, and the fuel injection parameters in the double valve closing period are changed. is there. It is a figure which shows the relationship between the ratio of the fuel amount injected in the both-valve closing period which concerns on Example 2, and exhaust gas temperature. 7 is a flowchart showing a special start control routine 2 according to the second embodiment. 10 is a flowchart showing a special start control routine 3 according to Modification 3.

  Specific examples of the present invention will be described below.

<Example 1>
(Internal combustion engine)
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an internal combustion engine start control apparatus according to Embodiment 1 of the present invention is applied. An internal combustion engine 1 shown in FIG. 1 is an in-cylinder direct injection engine having fuel injection valves 3 arranged in four cylinders 2 arranged.

  The internal combustion engine 1 is connected with an intake passage 4 for taking intake air into the cylinder 2. A throttle valve 5 whose opening degree is adjusted to change the amount of fresh intake air is disposed in the intake passage 4. A surge tank 6 is formed in the intake passage downstream of the throttle valve 5.

A cylinder 2 is formed in the internal combustion engine 1. A fuel injection valve 3 that is an electromagnetically driven injector that directly injects fuel into the cylinder 2 from an obliquely upper side is provided. Fuel is supplied to the fuel injection valve 3 from the fuel tank 8 through the fuel pipe 7. Here, as the fuel used in the internal combustion engine 1, fuels having different properties such as ethanol concentration (alcohol concentration) can be used. That is, as the fuel, not only gasoline but also a mixed fuel obtained by mixing ethanol with gasoline or an ethanol fuel containing only ethanol can be used. Thus, the ethanol concentration of the fuel used for the internal combustion engine 1 can be changed. In this embodiment, the fuel property of ethanol concentration will be described as an example. However, if the fuel property is different, the fuel evaporation characteristic with respect to the in-cylinder temperature and the fuel amount required for combustion will be different. If so, other properties can be applied to the present invention. An ethanol concentration sensor 9 that detects the ethanol concentration in the fuel is disposed in the fuel pipe 7 between the fuel tank 8 and the fuel injection valve 3. The ethanol concentration sensor 9 corresponds to the fuel property detection means of the present invention.

  An intake port 11 which is a part of the intake passage 4 communicating with the cylinder 2 of the internal combustion engine 1 is provided with an intake valve 11 so that intake air is introduced into the cylinder 2 by opening the intake valve 11. It has become. The exhaust port 13 which is a part of the exhaust passage 12 communicating with the cylinder 2 of the internal combustion engine 1 is provided with an exhaust valve 14. When the exhaust valve 14 is opened, the exhaust gas after combustion is discharged to the exhaust passage 12. The The intake valve 11 and the exhaust valve 14 are provided with VVTs 15 and 16 that can change the opening / closing timing (valve timing) of each valve. By controlling the opening / closing timing of the intake valve 11 and the exhaust valve 14 with each VVT 15, 16, a period in which both the intake valve 11 and the exhaust valve 14 are closed during the period from the exhaust stroke to the intake stroke is created. Can do. VVT15 and 16 in a present Example respond | correspond to the valve control means of this invention. For example, a mechanism that is arranged in a power transmission path from the crankshaft to the camshaft and that can vary the relative position (phase) of the camshaft rotation angle with respect to the crankshaft rotation angle may be employed as the VVT 15 and 16. it can.

  A spark plug 17 is disposed on the cylinder 2 of the internal combustion engine 1. A high voltage is applied to the ignition plug 17 at an ignition timing through an ignition coil or the like, a spark discharge is generated toward the counter electrode of the ignition plug 17, and the fuel is ignited and burned. A piston 18 is disposed below the cylinder 2 of the internal combustion engine 1. The piston 18 is provided with an in-cylinder temperature sensor 19 that detects the temperature in the cylinder 2. The in-cylinder temperature sensor 19 directly detects the surface temperature of the piston cavity where the fuel injected from the fuel injection valve 3 collides. In addition, without using the in-cylinder temperature sensor 19, a correlation between the temperature of the engine cooling water or the cylinder liner and the in-cylinder temperature is obtained in advance, and the temperature of the engine cooling water or the cylinder liner is detected to derive the in-cylinder temperature. You may do it. Further, a water temperature sensor 20 that detects the temperature of the engine cooling water is disposed in a water channel through which the engine cooling water around the cylinder 2 of the internal combustion engine 1 flows. In addition, a crank angle sensor 23 for detecting the engine rotation speed is disposed on the crankshaft of the internal combustion engine 1. The crank angle sensor 23 extracts a crank angle pulse signal from the crankshaft, and performs engine speed, cylinder discrimination, stroke detection when the cylinder 2 is stopped, and the like from the crank angle pulse signal.

  Connected to the internal combustion engine 1 is an exhaust passage 12 for discharging exhaust gas after combustion in the cylinder 2. A catalyst 21 for purifying the exhaust gas is disposed in the middle of the exhaust passage 12. As the catalyst 21, a three-way catalyst, an occlusion reduction type NOx catalyst, or the like is used.

  The internal combustion engine 1 is provided with an ECU (electronic control unit) 22. Various sensors such as the ethanol concentration sensor 9, the in-cylinder temperature sensor 19, the water temperature sensor 20, and the crank angle sensor 23 are connected to the ECU 22 through electric wiring, and output signals of these various sensors are input to the ECU 22. It has become. On the other hand, the fuel injection valve 3, the throttle valve 5, the VVTs 15 and 16, and the spark plug 17 are connected to the ECU 22 through electrical wiring, and these devices are controlled by the ECU 22.

(Special start control)
When starting the internal combustion engine 1, particularly when the temperature is extremely low, even if fuel is injected from the fuel injection valve 3 in the first cycle and ignited by the spark plug 17, for example, a large amount of misfire or unburned HC occurs. Equal combustion may not be performed satisfactorily. Such a situation is more likely to occur as the ethanol concentration of the fuel increases. This is because when the ethanol concentration of the fuel is high, it is difficult for the fuel to evaporate at a low temperature as compared with gasoline, and the fuel hardly vaporizes. For this reason, the amount of fuel required for combustion also increases. In order to cope with this problem, it is proposed to increase the fuel injection pressure, increase the fuel injection amount, or advance the fuel injection timing to ensure the evaporation time, etc. according to the ethanol concentration of the fuel Has been. However, in order to increase the fuel injection pressure from the start, an electric motor type drive pump that obtains power with an electric motor is required instead of a mechanical drive pump that obtains power from the crankshaft, which increases costs. Even if the fuel injection amount at the start is increased, the fuel injection rate is low because the fuel injection pressure is low, a long injection period is required, and the evaporation time of the injected fuel cannot be secured. For this reason, conventionally, in the first fuel injection cycle at the time of starting, the exhaust valve is slightly lifted or completely stopped, and the ignition is stopped to increase the in-cylinder fuel amount in the next cycle, and the initial ignition. Techniques for performing this have also been proposed. According to this, the in-cylinder fuel amount at the start can be increased without increasing the fuel injection rate even at a low fuel pressure, and the vaporized fuel amount can also be increased. At that time, it is not necessary to use a special fuel pump or injection valve, and the cost does not increase. However, with this technique, the number of cycles until the initial ignition at the time of starting increases by one cycle or more, and eventually the time required for starting increases. In addition, the load on the starter motor that performs cranking during the increased cycle period until the first ignition increases, and the durability of the starter motor may deteriorate. Therefore, the internal combustion engine 1 can be started in a short time without increasing the cycle until the first ignition, while ensuring a stable startability, and more preferably so that unburned HC hardly occurs and the deterioration of exhaust emission is suppressed. desired.

  As a result of intensive studies by the present inventors, in order to cope with this problem, a period during which both the intake valve 11 and the exhaust valve 14 are closed during the period from the exhaust stroke to the intake stroke (both valve closing period). And tried to inject fuel during both valve closing periods. Hereinafter, such start control is referred to as special start control. The both-valve closing period is created by closing the exhaust valve 14 during the exhaust stroke using the VVT 16 and opening the intake valve 11 during the intake stroke using the VVT 15. According to such special start control, the gas remaining in the cylinder 2 is recompressed by the rise of the piston 18 during the both valve closing period, and the in-cylinder temperature rises. In addition, fuel can be injected from the fuel injection valve 3 and fuel evaporation can be promoted. The ECU 22 that executes the fuel injection control by the fuel injection valve 3 during the both valve closing periods corresponds to the first injection control means of the present invention. In addition, for the special start control, the above-described compression that does not perform the special start control in which the both valve closing periods are created during the period from the exhaust stroke to the intake stroke and fuel is injected during the both valve closing periods. The normal normal start control in which fuel is injected in the stroke is called normal start control. FIG. 2 is a diagram showing opening and closing timings of the intake valve 11 and the exhaust valve 14 in the special start control and the normal start control. FIG. 2A is a diagram showing the opening / closing timing of the intake valve 11 and the exhaust valve 14 in the special start control, and FIG. 2B is the opening / closing timing of the intake valve 11 and the exhaust valve 14 in the normal start control. FIG. In the normal start control, as shown in FIG. 2B, a valve overlap period in which both valves are opened slightly before and after the intake top dead center is provided, whereas in the special start control, FIG. As shown in (a), both valve closing periods are provided before and after the intake top dead center.

  However, when fuel having different ethanol concentrations is used in the internal combustion engine 1 as in this embodiment, the fuel evaporation characteristics with respect to the in-cylinder temperature and the amount of fuel required for combustion differ depending on the ethanol concentration of the fuel. Depending on the ethanol concentration of the fuel, how much the in-cylinder temperature is raised in order to promote the evaporation of the fuel differs. FIG. 3 is a diagram showing the in-cylinder temperature and the fuel evaporation rate with respect to the ethanol concentration of the fuel. As shown in FIG. 3, the higher the ethanol concentration of the fuel, the higher the in-cylinder temperature is required to increase the evaporation rate.

Therefore, in the present embodiment, in order to achieve the optimum in-cylinder temperature for the ethanol concentration of the fuel, the special valve start control changes the double valve closing period to be created based on the ethanol concentration of the fuel. Specifically, the ethanol concentration sensor 9 detects the ethanol concentration of the fuel, and based on the detected ethanol concentration, the VVT 16 controls the closing timing of the exhaust valve 14 that is closed during the exhaust stroke, and the VVT 15 By controlling the opening timing of the intake valve 11 to be opened during the intake stroke, the both valve closing period is changed. Then, the fuel injection by the fuel injection valve 3 is once completed within the changed both valve closing period. FIG. 4 is a diagram showing fuel injection timings for the special start control and the normal start control. FIG. 4A is a diagram showing the fuel injection timing in the special start control in which fuel is injected during the both valve closing periods, and FIG. 4B is a diagram showing the fuel injection timing in the normal start control. It is. In the normal start control, as shown in FIG. 4 (b), the entire amount of fuel is injected at a time before the compression top dead center, whereas in the special start control, as shown in FIG. The entire amount of fuel is injected during the valve closing period.

  Note that even if the valve closing timing of the exhaust valve 14 is advanced, the residual gas amount in the cylinder 2 increases and the compression end temperature at the time of recompression increases. Therefore, in order to change both valve closing periods, the VVT 16 Only the closing timing of the exhaust valve 14 that is closed in the middle of the exhaust stroke may be controlled. FIG. 5 is a diagram showing the relationship between the closing timing of the exhaust valve 14 forming the both valve closing periods and the in-cylinder temperature. As shown in FIG. 5, the in-cylinder temperature is more likely to rise as the closing timing of the exhaust valve 14 is advanced from the intake top dead center.

  According to the present embodiment, both valve closing periods can be adjusted in the special start-up control so as to realize an optimal in-cylinder temperature for the ethanol concentration of the fuel, and fuel evaporation can be promoted. As a result, the fuel whose evaporation has been promoted can be burned well by ignition with the spark plug 17 of the cycle. Therefore, the cycle until the first ignition at the start does not increase by one cycle, the time required for the start does not increase, the load of the starter motor for cranking does not increase, and deterioration of the starter motor durability is suppressed. can do. Further, since the fuel burns well in this way, stable startability can be ensured, and unburned HC is hardly generated, and deterioration of exhaust emission can be suppressed. Therefore, the internal combustion engine 1 can be started better in a short time.

  In some cases, during the period from the exhaust stroke to the intake stroke, all of the fuel amount required for combustion cannot be injected within the both valve closing periods in which both the intake valve 11 and the exhaust valve 14 are closed. In that case, the fuel amount capable of promoting evaporation is injected during the both-valve closing period, and the remaining fuel amount necessary for combustion is injected during the compression stroke after the passage of the both-valve closing period. The ECU 22 that executes the fuel injection control by the fuel injection valve 3 in the compression stroke after the passage of both valve closing periods corresponds to the second injection control means of the present invention. Such a two-part fuel injection is also included in the special start control. FIG. 6 is a diagram showing the fuel injection timing of the special start control in the case of such two-part fuel injection. In the special start control in the case of the two-part fuel injection, as shown in FIG. 6, the fuel is injected in two parts, that is, both valve closing periods and before the compression top dead center.

(Special start control routine 1)
The special start control routine 1 in the ECU 22 will be described based on the flowchart shown in FIG. FIG. 7 is a flowchart showing the special start control routine 1. This routine is executed by the ECU 22.

  The routine shown in FIG. 7 is started when the ignition SW is turned on. When this routine is started, in S101, it is determined whether or not the in-cylinder temperature detected by the in-cylinder temperature sensor 19 is equal to or lower than a predetermined temperature T. The predetermined temperature T is a temperature at which combustion cannot be satisfactorily performed under normal start control when the temperature is lower than the predetermined temperature T. If an affirmative determination is made in S101, the process proceeds to S102. If a negative determination is made in S101, this routine is once ended and normal start control is performed.

  In S102, it is determined whether or not the ethanol concentration of the fuel detected by the ethanol concentration sensor 9 is higher than a predetermined concentration α. The predetermined concentration α is a temperature at which combustion cannot be satisfactorily performed under normal start control when the concentration is higher than that. If an affirmative determination is made in S102, the process proceeds to S103. If a negative determination is made in S102, this routine is once ended and normal start control is performed.

In S103, the starter SW is turned on and the starter motor is driven to start cranking.

  In S104, it is determined whether or not the first exhaust stroke is performed in each cylinder 2. If a positive determination is made in S104, the process proceeds to S105. If a negative determination is made in S104, the process returns to this step, and fuel injection and ignition are not performed until the first exhaust stroke is reached. This avoids performing fuel injection and ignition without providing both valve closing periods.

  In S105, the valve closing timing of the exhaust valve 14 to be closed in the middle of the exhaust stroke is controlled by the VVT 16 according to the ethanol concentration of the fuel detected by the ethanol concentration sensor, and the intake valve to be opened in the middle of the intake stroke by the VVT 15 11 is controlled to change both valve closing periods. During the both-valve closing period, the valve closing timing of the exhaust valve 14 is advanced as the ethanol concentration of the fuel becomes higher, and the intake valve 11 is opened so that fuel injection is once completed within the both-valve closing period. The time is retarded.

  In S106, the fuel injection valve 3 injects fuel during both valve closing periods, and if necessary, the remaining fuel amount required for combustion is injected in the compression stroke after the passage of both valve closing periods. Then, ignition is performed by the spark plug 17 in the vicinity of the compression top dead center.

  In S107, it is determined whether or not the in-cylinder temperature detected by the in-cylinder temperature sensor 19 is higher than a predetermined temperature T. The predetermined temperature T is a temperature at which combustion cannot be satisfactorily performed under normal start control when the temperature is lower than the predetermined temperature T. If an affirmative determination is made in S107, this routine is once ended, and normal start control or normal operation is performed. If a negative determination is made in S107, the process proceeds to S105 and the special start control is continued.

  In the present routine described above, the both valve closing periods can be adjusted in the special start control so as to realize the in-cylinder temperature optimum for the ethanol concentration of the fuel. As a result, the start can be performed satisfactorily by the special start control.

<Modification 1>
In the first modification of the present invention, as in the first embodiment, the both valve closing periods are changed according to the ethanol concentration of the fuel. However, the intake is started from the closing timing of the exhaust valve 14 that creates the both valve closing periods. The period until the top dead center is made shorter than the period from the intake top dead center to the opening timing of the intake valve 11.

  FIG. 8 is a diagram showing opening and closing timings of the intake valve and the exhaust valve according to the first modification of the present invention. FIG. 8A is a diagram illustrating the opening / closing timing of the exhaust valve 14 according to the first modification, and FIG. 8B is a diagram illustrating the opening / closing timing of the intake valve 11 according to the first modification. In the first modification, as shown in FIG. 8, the period (valve closing angle) θe from the closing timing of the exhaust valve 14 to the intake top dead center, which creates the both valve closing periods, is set from the intake top dead center to the intake valve 11. The period until the valve opening timing (opening angle) θi is made smaller (θe <θi).

According to the first modification, since θe <θi, the cylinder internal volume when the intake valve 11 is opened is larger than the cylinder internal volume when the exhaust valve 14 is closed, and the intake valve 11 during both valve close periods is closed. By the time the valve is opened, a negative pressure is generated in the cylinder 2, and the intake valve 11 is opened in a state where the negative pressure is generated. Thereby, in the special start control, the reduced pressure boiling can be performed by injecting the fuel during the both valve closing period in a state where the negative pressure is generated. Further, by opening the intake valve 11 in a state where negative pressure is generated, the flow velocity of the intake air flowing into the cylinder 2 becomes close to the speed of sound, and this kinetic energy increases the gas temperature in the cylinder 2. Can do. That is, by increasing the gas temperature in the cylinder 2, the in-cylinder temperature can be further increased after the both valve closing periods. FIG. 9 is a diagram showing a relationship between the difference θi−θe and the in-cylinder temperature according to the first modification of the present invention. As shown in FIG. 9, the difference θi−θe obtained by subtracting the period θe from the closing timing of the exhaust valve 14 to the intake top dead center from the period θi from the intake top dead center to the opening timing of the intake valve 11 is large. The in-cylinder temperature rises. Therefore, evaporation of fuel can be promoted. In particular, when fuel is injected in the compression stroke after the lapse of both valve closing periods described in the first embodiment, evaporation of fuel injected in the compression stroke can be promoted.

<Modification 2>
In the second modification of the present invention, the valve closing timing with respect to the intake bottom dead center of the intake valve 11 that has been opened after the lapse of both valve closing periods is changed based on the ethanol concentration of the fuel.

  When the closing timing of the intake valve 11 approaches the intake bottom dead center, the gas temperature in the cylinder 2 is increased due to an increase in the effective engine compression ratio due to the low engine speed at the start. Can do. FIG. 10 is a diagram illustrating a relationship between the valve closing timing of the intake valve 11 and the in-cylinder temperature. As shown in FIG. 10, the in-cylinder temperature can be increased as the closing timing of the intake valve 11 approaches the intake bottom dead center from either the advance side or the retard side. Thereby, according to the modified example 2, by changing the valve closing timing with respect to the intake bottom dead center of the intake valve 11 that has been opened after the both valve closing periods have elapsed, the compression stroke after the both valve closing periods is changed. The in-cylinder temperature can be changed. Therefore, if the closing timing of the intake valve 11 is optimally changed based on the ethanol concentration of the fuel, the evaporation of the fuel can be promoted. In particular, when fuel is injected in the compression stroke after the lapse of both valve closing periods described in the first embodiment, the fuel is injected in the compression stroke as the valve closing timing of the intake valve 11 approaches the intake bottom dead center. Fuel evaporation can also be promoted.

<Example 2>
In the second embodiment of the present invention, the injection parameter of the fuel to be injected during both valve closing periods is changed based on the ethanol concentration of the fuel. The description of the same configuration as that in the above embodiment is omitted.

  According to the special start control, the gas remaining in the cylinder 2 is recompressed by the rise of the piston 18 and the in-cylinder temperature rises during the both-valve closing period, so that the fuel is injected into the hot cylinder. Can evaporate the fuel. However, when fuels having different ethanol concentrations are used in the internal combustion engine 1, the fuel evaporation characteristics with respect to the in-cylinder temperature and the amount of fuel required for combustion differ depending on the ethanol concentration of the fuel. By setting the valve period, the fuel injection parameters for promoting the evaporation of fuels having different ethanol concentrations differ from the predetermined in-cylinder temperature. That is, in the case of the ethanol concentration of the fuel that causes the fuel evaporation characteristics to deteriorate with respect to the predetermined in-cylinder temperature, or in the case of the ethanol concentration of fuel in which the amount of fuel required for combustion increases at the predetermined in-cylinder temperature, At the same time, it is necessary to change the fuel injection parameters so as to further promote the evaporation of the fuel. For example, in order to promote the evaporation of fuel at a predetermined in-cylinder temperature, it is necessary to increase the fuel injection amount, increase the number of divided fuel injections, or advance the fuel injection timing during both valve closing periods. .

  Therefore, in order to realize the optimum fuel injection parameters for the fuel ethanol concentration and the in-cylinder temperature determined by the both-valve closing period, the fuel injected during the both-valve closing period is based on the ethanol concentration of the fuel. Changed the injection parameters. Specifically, the ethanol concentration sensor 9 detects the ethanol concentration of the fuel, and based on the detected ethanol concentration, the fuel injection amount of the fuel to be injected during the valve closing period, the number of divided fuel injections, the fuel injection timing Change the injection parameters. Then, fuel injection is performed with the changed injection parameters so that the fuel injection by the fuel injection valve 3 is once completed within the both valve closing periods.

FIG. 11 is a diagram for explaining a case where the fuel injection parameter in the both valve closing period is changed by increasing the number of divided fuel injections in the both valve closing period to two. As shown in FIG. 11, if the number of divided fuel injections in the both valve closing periods is increased to two, fuel evaporation can be promoted even if the ethanol concentration of the fuel becomes high.

  In the case of two-split fuel injection in which a fuel amount capable of promoting evaporation is injected during the both-valve closing period, and the remaining fuel amount required for combustion is injected in the compression stroke after the passage of both valve closing periods. As the fuel injection parameters are changed during the both valve closing periods, the fuel injection parameters in the latter half of the compression stroke are also changed. In other words, based on the ethanol concentration of the fuel, the amount of fuel that can promote evaporation can be injected within the both-valve closing period so that the fuel amount can be injected within the both-valve closing period. The ratio between the fuel amount and the fuel amount injected in the compression stroke may be changed based on the ethanol concentration of the fuel. FIG. 12 is a diagram for explaining a case where the amount of fuel injected during the both-valve closing period is increased and the amount of fuel injected during the compression stroke is reduced to change the fuel injection parameters during the both-valve closing period. . FIG. 13 is a diagram showing the relationship between the ratio of the amount of fuel injected during both valve closing periods and the exhaust gas temperature. As shown in FIG. 13, when the ratio of the amount of fuel injected during both valve closing periods to the total fuel to be injected becomes large, a homogeneous air-fuel mixture is formed in the cylinder, so that combustion becomes slow, and afterburning is promoted. As a result, the exhaust gas temperature in the cylinder rises. Accordingly, as shown in FIG. 12, if the amount of fuel injected in the both valve closing period is increased, the in-cylinder gas temperature in the next cycle and thereafter can be increased, and fuel evaporation can be promoted.

  According to this embodiment, the fuel injection parameter is adjusted in the special start-up control so as to realize the optimal fuel injection parameter for the fuel ethanol concentration and the in-cylinder temperature determined by the both valve closing periods. Can evaporate the fuel. As a result, the fuel whose evaporation has been promoted can be burned well by the ignition of the spark plug 17 in that cycle. Therefore, the cycle until the first ignition at the start does not increase by one cycle, the time required for the start does not increase, the load of the starter motor for cranking does not increase, and deterioration of the starter motor durability is suppressed. can do. Further, since the fuel burns well in this way, stable startability can be ensured, and unburned HC is hardly generated, and deterioration of exhaust emission can be suppressed. Therefore, the internal combustion engine 1 can be started better in a short time.

(Special start control routine 2)
The special start control routine 2 in the ECU 22 will be described based on the flowchart shown in FIG. FIG. 14 is a flowchart showing the special start control routine 2. This routine is executed by the ECU 22. The special start control routine 2 shown in FIG. 14 will be described only because S105 and S106 of the special start control routine 1 shown in FIG. 7 are changed to S205 and S206.

  In S205, the valve closing timing of the exhaust valve 14 to be closed in the middle of the exhaust stroke is controlled by the VVT 16, and the valve opening timing of the intake valve 11 to be opened in the middle of the intake stroke is controlled by the VVT 15 to control the constant both valves. Provide a valve closing period. During the both-valve closing period, the valve closing timing of the exhaust valve 14 is advanced as the ethanol concentration of the fuel becomes higher, and the intake valve 11 is opened so that fuel injection is once completed within the both-valve closing period. The time is retarded.

  In S206, the fuel injection valve 3 changes the fuel injection parameters according to the ethanol concentration of the fuel detected by the ethanol concentration sensor 9, and injects the fuel during the both valve closing periods, and if necessary, the fuel is burned. The required remaining fuel amount is injected in the compression stroke after the passage of both valve closing periods. Then, ignition is performed by the spark plug 17 in the vicinity of the compression top dead center.

  In the routine described above, in the special start-up control, in the both valve closing period, the optimal fuel injection parameters for the ethanol concentration of the fuel and the in-cylinder temperature determined by the both valve closing period are realized. The fuel injection parameters can be adjusted. As a result, the start can be performed satisfactorily by the special start control.

<Modification 3>
In the third modification of the present invention, both features of the first and second embodiments are included, and based on the ethanol concentration of the fuel, both the valve closing periods or the fuel injected during the both valve closing periods Change at least one of the injection parameters. The description of the same configuration as that in the above embodiment is omitted.

  In the third modified example, as in the first embodiment, in order to realize the in-cylinder temperature optimum for the ethanol concentration of the fuel, the special valve start control changes the both valve closing periods to be created based on the ethanol concentration of the fuel. Like that. Alternatively, as in the second embodiment, in order to realize an optimal fuel injection parameter for the fuel ethanol concentration and the in-cylinder temperature determined by the both valve closing periods, the both valves are based on the ethanol concentration of the fuel. The injection parameter of the fuel injected during the valve closing period is changed.

  According to the third modified example, the both valve closing periods can be adjusted in the special start control so as to realize the optimum in-cylinder temperature for the ethanol concentration of the fuel, and the evaporation of the fuel can be promoted. Alternatively, the fuel injection parameter can be adjusted in the special start control so as to realize the optimal fuel injection parameter for the fuel ethanol concentration and the in-cylinder temperature determined by the both valve closing periods. Can promote evaporation. As a result, the fuel whose evaporation has been promoted can be burned well by the ignition of the spark plug 17 in that cycle. Therefore, the cycle until the first ignition at the start does not increase by one cycle, the time required for the start does not increase, the load of the starter motor for cranking does not increase, and deterioration of the starter motor durability is suppressed. can do. Further, since the fuel burns well in this way, stable startability can be ensured, and unburned HC is hardly generated, and deterioration of exhaust emission can be suppressed. Therefore, the internal combustion engine can be started better in a short time.

(Special start control routine 3)
The special start control routine 3 in the ECU 22 will be described based on the flowchart shown in FIG. FIG. 15 is a flowchart showing the special start control routine 3. This routine is executed by the ECU 22. The special start control routine 3 shown in FIG. 15 will be described only because S105 and S106 of the special start control routine 1 shown in FIG. 7 are changed to S305 and S306.

  In S305, the valve closing timing of the exhaust valve 14 to be closed in the middle of the exhaust stroke is controlled by the VVT 16 according to the ethanol concentration of the fuel detected by the ethanol concentration sensor 9, and the intake air to be opened in the middle of the intake stroke by the VVT 15 is controlled. The valve opening period of the valve 11 is controlled to change both valve closing periods. During the both-valve closing period, the valve closing timing of the exhaust valve 14 is advanced as the ethanol concentration of the fuel becomes higher, and the intake valve 11 is opened so that fuel injection is once completed within the both-valve closing period. The time is retarded.

  In S306, the fuel injection valve 3 changes the fuel injection parameters in accordance with the ethanol concentration of the fuel detected by the ethanol concentration sensor 9 and injects the fuel during both valve closing periods, and if necessary, the fuel is burned. The required remaining fuel amount is injected in the compression stroke after the passage of both valve closing periods. Note that only one of the both valve closing periods or the fuel injection parameters in S305 and S306 may be changed and the other may be fixed, or the other may be changed in accordance with the changed one.

In the present routine described above, the both valve closing periods can be adjusted in the special start control so as to realize the in-cylinder temperature optimum for the ethanol concentration of the fuel. Or, in order to achieve the optimal fuel injection parameters for the fuel ethanol concentration and the in-cylinder temperature determined by the both valve closing periods, the fuel injection parameters for both valve closing periods are set in the special start control. Can be adjusted. As a result, the start can be performed satisfactorily by the special start control.

<Others>
The start control device for an internal combustion engine according to the present invention is not limited to the above-described embodiments and modifications, and various modifications may be made without departing from the scope of the present invention. For this reason, you may combine each Example and a modification so that implementation is possible. The above-described embodiments and modifications are also embodiments and modifications of the internal combustion engine start control method according to the present invention.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Fuel injection valve 4 Intake passage 5 Throttle valve 6 Surge tank 7 Fuel pipe 8 Fuel tank 9 Ethanol concentration sensor 10 Intake port 11 Intake valve 12 Exhaust passage 13 Exhaust port 14 Exhaust valves 15, 16 VVT
17 Spark plug 18 Piston 19 In-cylinder temperature sensor 20 Water temperature sensor 21 Catalyst 22 ECU
23 Crank angle sensor

Claims (7)

A start control device for a direct injection type internal combustion engine having a fuel injection valve disposed in a cylinder,
Fuel property detection means for detecting the property of fuel injected from the fuel injection valve;
Valve control means for controlling the opening and closing timing of the intake valve and the exhaust valve so as to create a period in which both the intake valve and the exhaust valve are closed during the period from the exhaust stroke to the intake stroke;
First injection control means for injecting fuel from the fuel injection valve during a period in which both the intake valve and the exhaust valve created by the valve control means are closed;
With
The start control device for an internal combustion engine, wherein the valve control means changes a period during which both the intake valve and the exhaust valve to be created are closed based on the fuel property detected by the fuel property detection means. . A start control device for a direct injection type internal combustion engine having a fuel injection valve disposed in a cylinder,
Fuel property detection means for detecting the property of fuel injected from the fuel injection valve;
Valve control means for controlling the opening and closing timing of the intake valve and the exhaust valve so as to create a period in which both the intake valve and the exhaust valve are closed during the period from the exhaust stroke to the intake stroke;
First injection control means for injecting fuel from the fuel injection valve during a period in which both the intake valve and the exhaust valve created by the valve control means are closed;
With
The first injection control means changes an injection parameter of fuel to be injected during a period in which both the intake valve and the exhaust valve are closed based on the fuel property detected by the fuel property detection means. An internal combustion engine start control device.   3. The internal combustion engine according to claim 1, further comprising a second injection control unit that injects fuel from the fuel injection valve after a lapse of a period in which both the intake valve and the exhaust valve are closed. Engine start control device.   The ratio between the amount of fuel injected by the first injection control unit and the amount of fuel injected by the second injection control unit is changed based on the property of the fuel detected by the fuel property detection unit. An internal combustion engine start control device according to claim 3.   The valve control means creates a period in which both the intake valve and the exhaust valve are closed, and sets a period from the closing timing of the exhaust valve to the intake top dead center from the intake top dead center to the opening of the intake valve. The start control device for an internal combustion engine according to any one of claims 1 to 4, wherein the start control device is set to be smaller than a period until time.   Based on the fuel property detected by the fuel property detection means, the valve closing timing for the intake bottom dead center of the intake valve that has been opened after the passage of both the intake valve and the exhaust valve is changed. The start control device for an internal combustion engine according to any one of claims 1 to 5, wherein: A method for starting control of an in-cylinder direct injection internal combustion engine having a fuel injection valve disposed in a cylinder,
The valve control means controls the opening and closing timing of the intake valve and the exhaust valve so as to create a period in which both the intake valve and the exhaust valve are closed during the period from the exhaust stroke to the intake stroke. Fuel is injected from the fuel injection valve during a period in which both the intake valve and the exhaust valve created by the valve control means are closed by the control means,
A period in which both the intake valve and the exhaust valve created by the valve control unit are closed based on the fuel property detected by the fuel property detection unit that detects the property of the fuel injected from the fuel injection valve; and A starting control method for an internal combustion engine, characterized in that at least one of a fuel injection parameter to be injected during a period when both the intake valve and the exhaust valve are closed by the first injection control means.

Images