JP2002227685A - Fuel injection controller for cylinder injection spark ignition internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a stratified combustion regardless of a fuel temperature. SOLUTION: A cylinder injection gasoline engine 11 applied with a fuel injection controller has a fuel injection valve 32 for directly injecting fuel into a combustion chamber 18. During the stratified combustion operation, the engine 11 forms a mixed gas combining the fuel from the fuel injection valve 32 and air around an ignition plug 34 to ignite the mixed gas with a spark of the ignition plug 34 for combustion. The fuel injection controller has a combustion temperature sensor 44 and an electronic controller (ECU). The combustion temperature sensor 44 detects the temperature of the fuel to be supplied to the fuel injection valve 32. The ECU sets the fuel injection timing in the stratified combustion operation based on the fuel temperature detected by at least the combustion temperature sensor 44.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection spark ignition type internal combustion engine in which a mixture of fuel and air directly injected into a combustion chamber is ignited and burned by a spark. The present invention relates to a fuel injection control device to be controlled.

[0002]

2. Description of the Related Art As an example of an internal combustion engine in which a mixture of intake air and fuel is burned in a plurality of combustion modes and the combustion mode is switched according to the engine operating state, for example, a direct injection spark ignition type internal combustion engine It has been known. The combustion mode in the internal combustion engine includes, for example, stratified combustion performed at a low load or the like, and homogeneous combustion performed at a high load or the like. During stratified charge combustion, fuel injected from the fuel injection valve in the latter half of the compression stroke is burned unevenly around the spark plug in the combustion chamber. Further, during homogeneous combustion, fuel injected from the fuel injection valve during the intake stroke is burned while being diffused throughout the combustion chamber.

[0003] In the above-described in-cylinder injection spark ignition type internal combustion engine, in order to stably perform stratified combustion, it is necessary that an air-fuel mixture having an appropriate concentration is formed around the ignition plug at the time of ignition. . In general, the time required for fuel vaporization and the diffusion of fuel spray tend to change under the influence of the ambient temperature, that is, the in-cylinder temperature. Therefore, the optimal fuel injection timing changes depending on the engine temperature. Therefore, Japanese Patent Laid-Open Publication No. Hei 10-141115 proposes setting the fuel injection timing during stratified charge combustion operation based on the engine temperature.

[0004]

As described above, it has been found that the time required for vaporizing the fuel and the diffusion of the spray are affected by the engine temperature as described above, but are more strongly affected by the temperature of the fuel itself. That is, as the temperature of the fuel supplied to the fuel injection valve decreases, the vaporization characteristics (easiness of vaporization) of the fuel at the initial stage of the injection decrease, and an air-fuel mixture having an appropriate concentration is formed around the ignition plug. It takes time. Conversely, as the fuel temperature increases,
The fuel vaporization characteristics in the early stage of the injection are improved, and the fuel spray is rapidly diffused.

However, the above-mentioned publication does not consider the fuel vaporization state at the beginning of the injection when setting the fuel injection timing. Therefore, depending on the fuel temperature,
Stratified combustion may become unstable, causing misfires and the like, leading to deterioration of drivability and the like.

The present invention has been made in view of such circumstances, and has as its object to control fuel injection of a direct injection spark ignition type internal combustion engine capable of stabilizing stratified combustion regardless of fuel temperature. It is to provide a device.

[0007]

The means for achieving the above object and the effects thereof will be described below. In the invention according to claim 1, a fuel injection valve for directly injecting fuel into the combustion chamber is provided, and during a stratified charge combustion operation, a mixture of fuel and air from the fuel injection valve is formed around an ignition plug, In a fuel injection control device used in a direct injection spark ignition type internal combustion engine in which the mixture is ignited and burned by sparks of the spark plug, a fuel temperature for detecting a temperature of fuel supplied to the fuel injection valve And a fuel injection timing setting means for setting a fuel injection timing during the stratified combustion operation based on at least the fuel temperature detected by the fuel temperature detection means.

According to the above configuration, during stratified charge combustion operation of the internal combustion engine, fuel is directly injected from the fuel injection valve into the combustion chamber according to the injection timing set by the injection timing setting means. This mixture of fuel and air is formed around the spark plug and is ignited and burned by the spark of the spark plug. Here, the temperature of the fuel supplied to the fuel injection valve is detected by the fuel temperature detecting means, and is reflected in the setting of the fuel injection timing by the injection timing setting means.

Therefore, the time required for vaporizing the fuel and the diffusion state of the fuel spray change due to the change in the temperature of the fuel supplied to the fuel injection valve, and the optimum fuel injection timing during stratified combustion operation changes. By making the fuel injection timing close to the optimum fuel injection timing in consideration of the fuel temperature as described above, it is possible to stabilize stratified combustion regardless of the fuel temperature.

According to a second aspect of the present invention, in the first aspect of the invention, when the fuel temperature detected by the fuel temperature detecting means is high, the fuel injection timing setting means performs the fuel injection during the stratified combustion operation. It is assumed that the timing is set to be more retarded than when the fuel temperature is low.

According to the above configuration, when the fuel temperature is high, the fuel injection timing during the stratified combustion operation is set to the retard side as compared with when the fuel temperature is low. For this reason, when the fuel temperature is low, the vaporization characteristics of the fuel in the initial stage of the injection are deteriorated, and it takes time to form an air-fuel mixture having an appropriate concentration around the ignition plug. As the injection timing is advanced, the time from injection to ignition becomes longer. As a result, it is possible to satisfy a condition necessary for stabilizing stratified combustion, that is, an air-fuel mixture having an appropriate concentration is formed around the ignition plug at the time of ignition. Also,
When the temperature of the fuel supplied to the fuel injection valve is high, the fuel is easily vaporized in the early stage of the injection, and the fuel spray is rapidly diffused. The time from ignition to ignition is reduced. Therefore,
Also in this case, it is possible to satisfy the conditions necessary for stabilizing the stratified combustion described above.

According to a third aspect of the present invention, in the second aspect of the invention, the fuel injection timing setting means increases the fuel injection during the stratified combustion operation as the fuel temperature detected by the fuel temperature detecting means increases. It is assumed that the timing is set to the retard side.

According to the above configuration, during the stratified charge combustion operation, the higher the fuel temperature is, the more the fuel injection timing is set to the retard side. Therefore, whatever the fuel temperature is,
The fuel injection timing can be made closer to the optimum fuel injection timing that changes according to the fuel temperature.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a vehicle is equipped with an in-cylinder injection gasoline engine (hereinafter simply referred to as an engine) 11, which is an embodiment of an internal combustion engine. The engine 11 includes a cylinder head 12 and a cylinder block 14 having a plurality of cylinders (cylinders) 13. A piston 15 is accommodated in each cylinder 13 so as to be able to reciprocate. Each piston 15 is connected via a connecting rod 16 to a crankshaft 17 which is an output shaft of the engine 11. The reciprocating motion of each piston 15 is transmitted to a crankshaft 17 after being converted into a rotary motion by a connecting rod 16.

The combustion chamber 18 is defined by the top surface of the piston 15, the inner wall surface of the cylinder 13, and the lower surface of the cylinder head 12. The cylinder head 12 has an intake port 19 and an exhaust port 20 communicating with each combustion chamber 18.
Are provided respectively.

In order to open and close these intake / exhaust ports 19 and 20, an intake valve 21 and an exhaust valve 22 are supported on the cylinder head 12 in a reciprocating manner. In the cylinder head 12, the intake / exhaust valves 21 and
2 above each camshaft 23, 2 having a cam.
4 is provided rotatably. These camshafts 23,
Reference numeral 24 is drivingly connected to the crankshaft 17 by a timing pulley, a timing belt, and the like (not shown). When the crankshaft 17 is rotated, the rotation is transmitted via a timing belt, a timing pulley and the like to the camshaft 23,
24. The intake and exhaust valves 21 and 22 reciprocate by the rotation of the camshafts 23 and 24, and the intake and exhaust ports 19 and
20 is opened or closed.

The intake port 19 has a throttle valve 25,
An intake passage 28 having a surge tank 26, an intake manifold 27 and the like is connected. Air outside the engine 11 passes through the portions 25 to 27 of the intake passage 28 in order and is taken into the combustion chamber 18.

The throttle valve 25 is rotatably supported in an intake passage 28, and an actuator 29 such as a step motor is drivingly connected to the throttle valve 25.
The actuator 29 operates in response to a driver's depression operation of an accelerator pedal (not shown) or the like, and rotates the throttle valve 25. The amount of intake air, which is the amount of air flowing through the intake passage 28, changes according to the throttle opening, which is the rotation angle of the throttle valve 25.

The intake manifold 27 is branched into the same number as the cylinders 13. Two passages are respectively formed in the inside of each branch portion. These passages are connected to the intake port 19 described above. An air flow control valve (swirl control valve) 30 is rotatably supported in one passage of each branch portion. The swirl control valve 30 is for generating a swirl (swirl) flow in the combustion chamber 18 by reducing the opening of one of the passages to promote combustion. An actuator 31 such as a step motor is drivingly connected to the swirl control valve 30. The strength of the swirl flow in each combustion chamber 18 changes according to the rotation angle of the swirl control valve 30.

An electromagnetic fuel injection valve 32 is attached to the cylinder head 12 for each cylinder 13. Each fuel injection valve 32 is supplied with high-pressure fuel through a common delivery pipe 33. For details, see Delivery Pipe 33
Has a long shape, and is arranged so as to extend in the cylinder arrangement direction of the engine 11 (the direction perpendicular to the plane of FIG. 1). A fuel inlet is provided at one end of the delivery pipe 33 in the length direction. The plurality of fuel injection valves 32 are attached to the delivery pipe 33 while being separated from each other. Each fuel injection valve 32 directly injects the high-pressure fuel supplied through the delivery pipe 33 into the corresponding combustion chamber 18. The injected fuel is supplied to the intake passage 2
The fuel gas mixes with the intake air introduced into the combustion chamber 18 through the passage 8 to form an air-fuel mixture.

The cylinder head 12 has a spark plug 34
Are attached to each cylinder 13. The ignition plug 34 is driven based on an ignition signal from an igniter 35 (see FIG. 2). A high voltage output from an ignition coil (not shown) is applied to the ignition plug 34. Then, the air-fuel mixture is ignited by the electric spark of the ignition plug 34, and explodes and burns. The piston 15 is reciprocated by the high-temperature and high-pressure combustion gas generated at this time, the crankshaft 17 is rotated, and the driving force (output torque) of the engine 11 is obtained.

On the other hand, the exhaust port 20 is connected to an exhaust passage 38 having an exhaust manifold 36, a catalytic converter 37 and the like. The combustion gas generated in the combustion chamber 18 passes through each part 36, 37, etc. of the exhaust passage 38 in order, and
Is discharged to the outside. The catalytic converter 37 has a built-in catalyst for purifying the combustion gas flowing through the exhaust passage 38.

In the present embodiment, there are at least homogeneous combustion and stratified combustion as combustion modes of the air-fuel mixture, and these are switched according to the operating state of the engine 11. Homogeneous combustion is a combustion mode in which fuel is injected in the first half of the intake stroke (while the piston 15 is moving down), for example, when the engine 11 is under a high load, thereby forming a homogeneous mixture. In the stratified combustion, for example, when the engine 11 is under a low load, by injecting fuel in the latter half of the compression stroke (while the piston 15 is rising), the fuel-rich mixture (about the stoichiometric air-fuel ratio) around the ignition plug 34 This is a combustion mode in which lean combustion is enabled by forming a layer of air and forming a layer of air around the layer.

Here, during the stratified charge combustion operation, the time required for vaporizing the fuel and the diffusion state of the fuel spray change according to the fuel temperature, and the optimum fuel injection timing changes. FIG. 5 shows the relationship among the fuel injection timing, misfire frequency, and fuel temperature.
In the figure, the characteristic line shown by a solid line represents the relationship between the fuel injection timing and the misfire frequency when the fuel temperature is low, and the characteristic line shown by the two-dot chain line shows the relationship between the fuel injection timing and the misfire frequency when the fuel temperature is high. Represents the relationship. As is apparent from FIG.
When the fuel temperature is low and the fuel injection timing belongs to a certain range R, the misfire frequency becomes extremely small. Further, when the fuel injection timing deviates from the range R, the misfire frequency tends to increase as the fuel injection timing moves away from the range R. This tendency occurs regardless of whether the fuel injection timing moves toward the advanced side (the side where the fuel injection timing is advanced with respect to the crank angle described later) or the retard side (the side where the fuel injection timing is advanced with respect to the crank angle). Can be seen. Further, the characteristic line shifts to the retard side as the fuel temperature increases, as indicated by the arrow in the figure. This means that even if the fuel injection timing belongs to the range R when the fuel temperature is low, the misfire frequency may increase as the fuel temperature increases.

As shown in FIG. 1, various sensors are used to detect the operating state of the engine 11. For example, near the crankshaft 17, the crankshaft 17
Is provided with a crank angle sensor 39 which generates a pulse-shaped signal every time the. In the vicinity of the camshaft 23, there is provided a cylinder discrimination sensor 40 that generates a pulse-like signal when the piston 15 of a predetermined cylinder reaches the intake top dead center. The signals from the crank angle sensor 39 and the cylinder discrimination sensor 40 are used for calculating the crank angle (° CA), the engine rotation speed, and the like, and for discriminating the cylinder.

In the vicinity of the throttle valve 25, a throttle sensor 41 for detecting a throttle opening is arranged. In the intake passage 28, on the downstream side of the throttle valve 25, for example, in the surge tank 26, an intake pressure sensor 42 for detecting an intake pressure, which is a pressure of intake air, is provided. The accelerator pedal is provided with an accelerator sensor (see FIG. 2) 43 for detecting an accelerator opening which is an amount of depression of the pedal by the driver. At one end in the length direction of the delivery pipe 33, a temperature sensor (fuel temperature sensor) 44 for directly detecting the temperature of the fuel in the same portion is attached. The detection value of the fuel temperature sensor 44 is used as the temperature (fuel temperature) TF of the fuel supplied to the fuel injection valve 32.

Further, in order to control each part of the engine 11 based on the detection values of the various sensors 39 to 44, an electronic control unit (E) shown in FIG.
CU) 45 is used. The ECU 45 is a CPU 4
6, read-only memory (ROM) 47, random access memory (RAM) 48, backup RAM 49,
An external input circuit 50 and an external output circuit 51 are provided.
These circuits are connected to each other by a bus 52.

The ROM 47 stores a predetermined control program and initial data in advance. The CPU 46 has a ROM 4
Various arithmetic processes are executed according to the control program and the initial data stored in. The RAM 48 includes a CPU 46
Is temporarily stored. Backup RA
M49 is backed up by a battery (not shown) in order to retain various data in RAM 48 even after power supply to ECU 45 is stopped.

Then, the CPU 46 inputs detection signals of the various sensors 39 to 44 via the external input circuit 50. Further, the CPU 46 determines the engine 11 based on these inputs.
The fuel injection amount, the fuel injection timing, the opening of the throttle valve 25, the opening of the swirl control valve 30, and the ignition timing are determined based on the operating state and a predetermined arithmetic expression or a predetermined control map. Is calculated. Then, the CPU 46
A control signal is output to the actuators 29 and 31, the fuel injection valve 32, the igniter 35 and the like based on the calculation result.

For example, the CPU 46 determines the engine load based on the engine speed, the fuel injection amount, and the like, and specifies the operating region to which the engine load belongs. The fuel injection amount is calculated based on, for example, the engine speed, the accelerator opening (or intake pressure), and the like. When it is determined that the engine load is in the low load operation region, the opening of the swirl control valve 30 is reduced by controlling the actuator 31. Further, the actuator 29 is controlled so that the throttle valve 25 is substantially fully opened. Further, during the compression stroke of each cylinder, the fuel is supplied to the fuel injection valve 32 to inject fuel.

In this case, fresh air is introduced into the combustion chamber 18 of each cylinder mainly from one of the passages during the intake stroke, and a strong swirl flow is generated. In the subsequent compression stroke, the fuel injected from the fuel injection valve 32 rides on the swirl flow and the combustion chamber 1
8 and moves to the vicinity of the spark plug 34 at a predetermined timing. At this time, the combustion chamber 18 is in a so-called stratified state in which the vicinity of the ignition plug 34 becomes a combustible air-fuel mixture layer and the other areas become air layers. Then, the CPU 46
The igniter 35 is driven at a predetermined time to
Ignite. As a result, the air-fuel mixture in the combustion chamber 18 burns (stratified combustion) using the combustible air-fuel mixture layer near the ignition plug 34 as an ignition source.

On the other hand, when the CPU 46 determines that the engine load is in the high load operation range, the
To make the swirl control valve 30 fully open. Further, the actuator 29 is controlled such that the throttle valve 25 has an opening corresponding to the amount of depression of the accelerator pedal (accelerator opening). Further, during the intake stroke of each cylinder, the fuel is supplied to the fuel injection valve 32 to inject fuel. In this case, an air-fuel mixture near the stoichiometric air-fuel ratio where air and fuel are homogeneously mixed is formed over substantially the entire region in the combustion chamber 18 of each cylinder, and homogeneous combustion is realized.

Next, the operation of the present embodiment configured as described above will be described. The flowchart of FIG.
The routine for setting the fuel injection timing during stratified charge combustion operation among the processes executed by the CU 45 is shown.

First, in step S110, the ECU 45 determines whether or not the operating state of the engine is in a stratified combustion operation range. This determination uses the engine load as described above. That is, it is determined whether or not the engine load obtained based on the engine speed, the fuel injection amount, and the like belongs to the low load region, and if it does, it is assumed that the engine load belongs to the stratified combustion region. If the determination condition is not satisfied, the injection timing setting routine is ended once, and if satisfied, the process proceeds to step S120. Step S
At 120, the basic injection timing AINJbase is calculated based on the engine speed and the engine load, for example.

Next, in step S130, the fuel temperature TF from the fuel temperature sensor 44 is read. Step S14
At 0, a correction value K corresponding to the fuel temperature TF at the step S130 is calculated with reference to the control map of FIG. The correction value K is for correcting the basic injection timing AINJbase when calculating the fuel injection timing, and advances (advances) the fuel injection timing with respect to the crank angle.
In this case, the larger the degree of the advance angle, the larger the value.

The control map defines the relationship between the fuel temperature TF and a correction value K that is substantially inversely proportional to the fuel temperature TF. That is, the correction value K takes a large value when the fuel temperature TF is low, but decreases as the fuel temperature TF increases. Therefore, when this correction value K is used, the fuel injection timing is retarded as the fuel temperature TF rises. Note that the correction value K may be calculated according to a predetermined calculation formula instead of the control map.

In step S150 of FIG. 4, it is determined whether or not the correction value K in step S140 is larger than a lower limit Kmin of a range that can be normally taken.
At 60, it is determined whether the correction value K is smaller than the upper limit Kmax of the range. Step S150, S1
60 are all satisfied (Kmin <K
<Kmax) and in step S170, the correction value K is added as it is to the basic injection timing AINJbase in step S120, and the addition result is set as the fuel injection timing AINJC.

On the other hand, if the determination condition of step S150 is not satisfied (Kmin ≧ K), step S19
At 0, the lower limit Kmin is added to the basic injection timing AINJbase, and the addition result is set as the fuel injection timing AINJC. If the determination condition in step S160 is not satisfied (K ≧ Kmax), in step S180, the upper limit Kmax is added to the basic injection timing AINJbase, and the addition result is set as the fuel injection timing AINJC. It should be noted that a correction coefficient is used instead of the correction value K, and this is used as the basic injection timing AINJ
Base may be multiplied, and the multiplication result may be used as the fuel injection timing AINJC.

Then, as described above, step S170
After setting the fuel injection timing AINJC in steps S190 to S190, the injection timing setting routine ends. The fuel injection timing AINJC set in this way is used for fuel injection control in a separately prepared fuel injection control routine. That is, the fuel injection valve 32 is energized based on the fuel injection timing AINJC, and high-pressure fuel is injected into the combustion chamber 18.

According to the above-described embodiment, the following effects can be obtained. (1) The fuel temperature TF is detected, and the fuel injection timing AINJC during the stratified combustion operation is set based on the detected value. For this reason, the time required for vaporization of the fuel and the diffusion state of the fuel spray change according to the fuel temperature TF, and the characteristic line in FIG. Although the injection timing changes, the fuel injection timing AINJC can be made closer to the optimum fuel injection timing by reflecting the fuel temperature TF in the setting of the fuel injection timing AINJC. Along with this, the frequency of misfires can be reduced to suppress fluctuations in combustion, stabilize stratified combustion, and prevent deterioration in drivability.

In particular, when the fuel temperature TF is low, the correction value K is increased compared to when the fuel temperature TF is high, and the fuel injection timing AINJC
Is set to the value on the advance side. Therefore, the fuel temperature TF
When the fuel injection timing is low, it takes time to form an air-fuel mixture having an appropriate concentration around the spark plug 34 due to deterioration of the vaporization characteristics of the fuel at the beginning of the injection. Time becomes longer. As a result, at the time of ignition, a condition necessary for stabilizing stratified combustion can be satisfied, that is, an air-fuel mixture having an appropriate concentration is formed around the spark plug 34.

When the fuel temperature TF is high, the correction value K is made smaller than when the fuel temperature TF is low, and the fuel injection timing AINJC is set to a value on the retard side. For this reason, when the fuel temperature TF is high, the fuel is easily vaporized in the early stage of the injection, and the fuel spray is rapidly diffused, but by delaying the fuel injection timing AINJC,
The time from injection to ignition is reduced. As a result, also in this case, the conditions necessary for stabilizing the stratified combustion described above can be satisfied.

Further, in the present embodiment, the correction value K is made substantially inversely proportional to the rise of the fuel temperature TF in the control map of FIG. 3, so that the higher the fuel temperature TF, the more the fuel injection timing AINJC during the stratified charge combustion operation. It is set to the value on the retard side. Therefore, regardless of the value of the fuel temperature TF, the fuel injection timing AINJC can be set by obtaining the optimum correction value K for the fuel temperature TF. (2) As means for detecting the temperature of the fuel supplied to the fuel injection valve 32, a fuel temperature sensor 44 is used. Therefore, the detection value of the fuel temperature sensor 44 can be used as it is as the fuel temperature TF for calculating the correction value K. (3) The fuel temperature sensor 44 is attached to the delivery pipe 33 located near the upstream of the fuel injection valve 32 in the fuel supply path. For this reason, the fuel temperature TF can be detected with higher accuracy than when the fuel temperature sensor 44 is attached to another part of the fuel supply path. (4) An upper limit value Kmax and a lower limit value Kmin are set, and processing (guard processing) is performed so that the correction value K does not exceed these values Kmax and Kmin (step S in FIG. 4).
150, S160, S180, S190). For this reason,
Even if the fuel temperature TF is excessively low or high, it is possible to prevent an extreme fuel injection timing from being set due to that.

The present invention can be embodied in another embodiment described below. The temperature of the fuel supplied to the fuel injection valve 32 may be indirectly detected. Specifically, without using the fuel temperature sensor 44, the fuel temperature TF may be estimated based on factors considered to affect the fuel temperature TF. The factors include, for example, the temperature of the cooling water of the engine 11 (cooling water temperature), the fuel injection amount, the traveling air flow, and the like.

The cooling water and the traveling wind exert an action of taking heat from the delivery pipe 33 (cooling action). Therefore, for example, when the cooling water temperature is low or the traveling air volume is large, the cooling effect is strong, and the fuel temperature TF tends to be low. When the cooling water temperature is high or the traveling air volume is small, the cooling effect is weak and the fuel temperature TF increases. Cheap. In general, the traveling airflow increases as the traveling speed increases, and thus the traveling speed may be used as a substitute value for the traveling airflow.

When the fuel injection amount is small, the time from the flow of the fuel into the delivery pipe 33 to the flow of the fuel when the fuel injection valve 32 is opened becomes long. Therefore, the amount of heat received by the delivery pipe 33 from the cylinder head 12 and the like is large, and the fuel temperature TF tends to increase. Conversely, when the fuel injection amount increases, the time becomes short, and the influence of heat received from the cylinder head 12 and the like decreases, and the fuel temperature T
F is unlikely to be high.

Therefore, it is possible to estimate the fuel temperature TF in consideration of the effects of the above-described factors on the fuel temperature. In this case, the fuel temperature sensor 4 used in the above embodiment is used.
4 becomes unnecessary. In addition, since each element is usually used for other control or the like, it is not necessary to newly add a sensor or the like.

However, when estimating the fuel temperature TF using the cooling water temperature, it is necessary to combine it with another factor, for example, the fuel injection amount. This is because, for example, even when the cooling water temperature is the same between when the vehicle is traveling and when the vehicle is stopped after traveling, the fuel temperature may be different due to the difference in the fuel injection amount as described above. is there. The fuel temperature TF can be estimated with high accuracy by combining the cooling water temperature with the fuel injection amount as compared with the case of estimating only with the cooling water temperature.

As a method for estimating the fuel temperature TF, the relationship between the coolant temperature, the fuel injection amount, and the like and the fuel temperature when the operating state of the engine 11 is in a steady state is determined in advance by experiments or the like. The fuel temperature corresponding to the cooling water temperature, the fuel injection amount, or the like may be determined. Then, when switching from the predetermined steady state to a different steady state, the estimated value in the current steady state is gradually changed over time to approach the estimated value in the steady state after the switching. To In this way, it is possible to accurately estimate not only the steady state but also the fuel temperature during the transition.

As described above, the fuel injection timing has a small range R of misfire frequency (see FIG. 5). The range R shifts according to the fuel temperature TF. For this reason, when the basic injection timing AINJbase belongs to the above-described range for each fuel temperature TF, the correction is not performed. May be performed.
Even in this case, the misfire is prevented in the same manner as in the above-described embodiment,
Combustion fluctuations due to misfire can be suppressed.

If the fuel temperature sensor 44 is at or near the fuel supply passage to the fuel injection valve 32, the delivery pipe 3
3 may be attached to a different member. However, the influence of the heat of the cylinder head 12 on the fuel temperature is greatest at the fuel injection valve 32 close to the cylinder head 12, and decreases as the distance from the fuel injection valve 32 increases. Therefore, from the viewpoint of more accurately detecting the temperature of the fuel supplied to the fuel injection valve 32, the fuel temperature sensor 44
It is desirable to be attached to a member close to.

The mounting position of the fuel temperature sensor 44 on the delivery pipe 33 may be changed. Here, in addition to the delivery pipe 33 being formed in a long shape, the fuel inlet is provided at one end in the length direction of the delivery pipe 33. In this case, a difference may occur in the fuel temperature. So, for example,
The fuel temperature sensor 44 may be attached to the central portion in the length direction of the delivery pipe 33, and in this case, it is possible to detect the average fuel temperature.

It is also possible to use a plurality of fuel temperature sensors, arrange them at different points in the fuel supply path, and use the average value of the detected values of the fuel temperature sensors as the fuel temperature TF. In this way, the detection accuracy of the fuel temperature TF is improved as compared with the case where a single fuel temperature sensor is used.

In the above embodiment, the fuel injection timing AINJC
Although the basic injection timing AINJbase is corrected by the fuel temperature TF in the calculation of, the fuel injection timing AINJC may be calculated based on at least the fuel temperature TF without performing this correction.

In addition, technical ideas that can be grasped from the above embodiments will be described together with their effects. (A) In the fuel injection control device for a direct injection spark ignition type internal combustion engine according to any one of claims 1 to 3, the fuel temperature detecting means is disposed near an upstream of the fuel injection valve. It is a temperature sensor attached to a pipe.

According to the above configuration, the temperature of the fuel in the delivery pipe located near the upstream of the fuel injection valve in the fuel supply path is close to the temperature of the fuel supplied to the fuel injection valve. Therefore, the fuel temperature can be detected with higher accuracy by the temperature sensor attached to the delivery pipe. Further, the value detected by the temperature sensor can be used as it is as the fuel temperature.

(B) In the fuel injection control apparatus for a direct injection spark ignition type internal combustion engine according to any one of claims 1 to 3, the fuel temperature detecting means includes at least a temperature of a coolant of the internal combustion engine and The temperature of the fuel supplied to the fuel injection valve is estimated based on the fuel injection amount.

According to the above configuration, there is a correlation between the coolant temperature and the fuel temperature, and between the fuel injection amount and the fuel temperature. Therefore, the fuel temperature can be indirectly detected from the coolant temperature and the fuel injection amount without directly detecting the fuel temperature. Further, the fuel temperature can be estimated with higher accuracy than when the fuel temperature is estimated only from the coolant temperature.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an engine to which a fuel injection control device is applied according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of a control system of the engine.

FIG. 3 is a characteristic diagram illustrating a control map that defines a relationship between a fuel temperature and a correction value.

FIG. 4 is a flowchart illustrating a procedure for setting a fuel injection timing during stratified charge combustion operation.

FIG. 5 is a graph showing a relationship among fuel injection timing, misfire frequency, and fuel temperature.

[Explanation of symbols]

11 ... engine, 18 ... combustion chamber, 32 ... fuel injection valve, 3
4: spark plug, 44: fuel temperature sensor, 45: ECU.

Continued on the front page F term (reference) 3G084 AA04 BA05 BA15 BA21 CA03 CA04 DA25 DA28 EC02 FA00 FA10 FA11 FA13 FA33 FA38 FA39 3G301 HA04 HA16 HA17 JA03 JA23 KA08 KA09 LA03 LA05 LB04 LC04 MA19 NB02 NE12 NE17 NE19 PA07Z PA11Z PEBZZ PE05Z PF01Z PF03Z

Claims (3)

[Claims] 1. A fuel injection valve for directly injecting fuel into a combustion chamber, and in a stratified combustion operation, a mixture of fuel and air from the fuel injection valve is formed around an ignition plug,
In a fuel injection control device used in a direct injection spark ignition type internal combustion engine in which the mixture is ignited and burned by sparks of the spark plug, a fuel temperature for detecting a temperature of fuel supplied to the fuel injection valve A direct injection spark ignition type internal combustion engine, comprising: detection means; and injection timing setting means for setting a fuel injection timing during the stratified combustion operation based on at least the fuel temperature detected by the fuel temperature detection means. Fuel injection control device. 2. The fuel injection timing setting means, when the fuel temperature detected by the fuel temperature detecting means is high, shifts the fuel injection timing during the stratified combustion operation to a more retarded side than when the fuel temperature is low. 2. The fuel injection control device for a direct injection spark ignition type internal combustion engine according to claim 1, wherein the setting is performed. 3. The fuel injection timing setting means sets the fuel injection timing during the stratified charge combustion operation to a more retarded side as the fuel temperature detected by the fuel temperature detection means becomes higher. A fuel injection control device for an in-cylinder injection spark ignition type internal combustion engine as described in the above.