JP2006307737A - Starting control device of cylinder injection internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a sudden change in starting time by a little difference in the cooling water temperature, in a system for controlling a boosting start. <P>SOLUTION: This starting control device performs " the boosting start " for taking preference of a fuel pressure increase by prohibiting starting time fuel injection in the whole temperature area, regardless of the detecting cooling water temperature of a cooling water temperature sensor 32, when detecting fuel pressure of a fuel pressure sensor 29 is predetermined injection allowable fuel pressure or less in starting. Afterwards, when starting the fuel injection when the detecting fuel pressure of the fuel pressure sensor 29 exceeds the injection allowable fuel pressure, a determination is made on to which of three temperature areas of the low temperature, the medium temperature and the high temperature the detecting cooling water temperature of the cooling water temperature sensor 32 corresponds, and the starting time injection timing is set to an intake stroke in a low temperature area and a high temperature area, and the starting time injection timing is set to a compression stroke in a medium temperature area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a start control device for an in-cylinder injection type internal combustion engine having a function of increasing the fuel pressure early at the start.

  An in-cylinder injection engine that directly injects fuel into a cylinder has a shorter time from injection to combustion than an intake port injection engine that injects fuel into an intake port, and can earn enough time to atomize injected fuel. Therefore, it is necessary to atomize the injected fuel by increasing the injection pressure. For this reason, in the cylinder injection engine, the fuel pumped up from the fuel tank by the low pressure pump is increased in pressure by the high pressure pump driven by the cam shaft of the engine and is pumped to the fuel injection valve.

  Since the high-pressure pump and the low-pressure pump are also stopped while the engine is stopped, the fuel pressure in the fuel pipe decreases with time. For this reason, when the engine stop time becomes long, the fuel pressure decreases to almost 0 MPa, and therefore it takes some time for the fuel pressure to rise to a high fuel pressure region suitable for starting at the time of starting. As a result, since the fuel is injected at a low fuel pressure at the time of starting, the atomization of the injected fuel is insufficient and the combustibility is deteriorated, the in-cylinder wet is increased, the startability is deteriorated, Emissions at start-up also get worse.

  As a countermeasure against this, in the start control of the cylinder injection engine, as described in Patent Document 1 (Japanese Patent Laid-Open No. 11-270385) and Patent Document 2 (Japanese Patent Laid-Open No. 2004-218615), a predetermined value at the initial stage of starting is described. In some cases, the injection is stopped during the period, and during the injection stop period, the fuel pressure is raised to a high fuel pressure region suitable for the start by the high pressure pump, and then the boost start is performed to start the injection.

In such boost start-up control, it is possible to further improve the emission by performing the compression stroke injection at the start. However, as shown in FIG. 3, when the cooling water temperature at the start is low, smoke generation and In order to avoid the problem of deterioration of the start feeling, the compression stroke injection and the pressure boost start are prohibited and the intake stroke injection is started, and when the cooling water temperature at the time of start is high, the injection amount decreases, so The compression stroke injection and the pressure boost start are prohibited and the intake stroke injection is started for the reason that it becomes difficult to form a stratified mixture which is easy.
JP-A-11-270385 (first page, etc.) JP-A-2004-218615 (pages 6 to 7 etc.)

  When the presence or absence of boosting start is switched according to the cooling water temperature as in the conventional case (FIG. 3), the start time suddenly changes due to a slight difference in the cooling water temperature in the vicinity of the switching temperature, and the driver feels uncomfortable. (Part surrounded by a dotted line in FIG. 3). That is, in the boosting start, since the fuel injection is stopped during the boosting time until the fuel pressure is increased to the injection permitted fuel pressure, it is inevitable that the starting time becomes longer than the normal starting by the intake stroke injection. Therefore, if the boosting start is completely prohibited at low water temperature or high water temperature, the start-up time is suddenly shortened despite the low water temperature starting, or the cooling water temperature is slightly higher on the high water temperature side. The starting time may be suddenly shortened just by becoming, which causes the driver to feel uncomfortable.

  The present invention has been made in view of such circumstances. Therefore, the object of the present invention is to prevent a start time from changing suddenly due to a slight difference in cooling water temperature in a system that performs boost start-up control. It is an object of the present invention to provide a start control device for a cylinder injection type internal combustion engine that can eliminate the discomfort.

  In order to achieve the above object, the invention according to claim 1 is directed to a fuel pressure detecting means for detecting the pressure of fuel supplied to the fuel injection valve (hereinafter referred to as “fuel pressure”), and a cooling for detecting the cooling water temperature of the internal combustion engine. A water temperature detecting means is provided, and the start control means prohibits fuel injection at the start and increases the fuel pressure regardless of the detected cooling water temperature of the cooling water temperature detecting means when the detected fuel pressure of the fuel pressure detecting means is below a predetermined fuel pressure at the time of starting. When starting fuel injection after the fuel pressure detected by the fuel pressure detection means exceeds the predetermined fuel pressure, if the cooling water temperature detected by the cooling water temperature detection means is lower than the predetermined temperature, the injection timing at start is set to the intake stroke. In other cases, the injection timing at the start is set to the compression stroke. In this way, at the time of start-up, “pressure boost start” that prohibits fuel injection and prioritizes increase in fuel pressure can be executed in the entire temperature range regardless of the coolant temperature, and fuel is injected by an injection method suitable for the coolant temperature. Can be started. As a result, it is possible to prevent the start time from changing suddenly due to a slight difference in cooling water temperature, to eliminate the driver's uncomfortable feeling, and to cause problems of smoke generation at low water temperature and deterioration of the start feeling by the intake stroke injection. Can be resolved.

  By the way, in the compression stroke injection, in order to collect the stratified mixture around the spark plug, the injection timing is retarded to the vicinity of the compression TDC (top dead center), and therefore, the ignition timing must be significantly retarded. When the water temperature is low, the ignition timing will continue to be retarded for early catalyst warm-up even after startup. However, at high water temperature, the catalyst is already warmed and the catalyst early warm-up (ignition timing retarded) Since it is not necessary, it is necessary to advance the ignition timing greatly immediately after starting, and torque shock occurs at that time. In addition, in order to form a stratified mixture that is easy to burn around the spark plug by compression stroke injection, a certain amount of injection is required, but at high water temperatures, the amount of injection decreases, so stratified mixing that is easy to burn There is also a situation where the formation of qi becomes difficult.

  As a countermeasure against this, as in claim 2, when the detected fuel pressure of the fuel pressure detecting means is equal to or lower than a predetermined fuel pressure at the start, fuel injection at the start is prohibited and the fuel pressure rises regardless of the detected coolant temperature of the coolant temperature detecting means. Priority is given to whether the detected coolant temperature of the coolant temperature detection means falls into one of three temperature ranges: low temperature, medium temperature, or high temperature when fuel injection is started after the detected fuel pressure of the fuel pressure detection means exceeds the predetermined fuel pressure. Determination may be made so that the injection timing at the start is set to the intake stroke in the low temperature region and the high temperature region, and the injection timing at the start is set to the compression stroke in the intermediate temperature region. In this way, the same effect as in the first aspect can be obtained, and in addition, since the intake stroke injection is performed at the start in the high temperature region, the ignition timing at the start is greatly delayed unlike the compression stroke injection. There is no need to horn. For this reason, it is not necessary to advance the ignition timing significantly after starting, which can solve the problem of torque shock due to the advance of the ignition timing after starting, and it becomes difficult to form a stratified mixture that easily burns in a high temperature region. This problem can be solved by using the intake stroke injection.

  Further, as in claim 3, when the detected fuel pressure of the fuel pressure detecting means is less than a predetermined fuel pressure at the start, fuel injection at the start is prohibited regardless of the detected coolant temperature of the cooling water temperature detecting means to give priority to an increase in fuel pressure. When the fuel injection is started after the fuel pressure detected by the fuel pressure detecting means exceeds the predetermined fuel pressure, the cooling water temperature detected by the cooling water temperature detecting means falls into one of the four temperature ranges of extremely low temperature, low temperature, medium temperature, and high temperature. In the extremely low temperature region and the high temperature region, the injection timing at the start is set to the intake stroke, in the intermediate temperature region, the injection timing at the start is set to the compression stroke, and in the low temperature region, the fuel is taken in the intake stroke and / or the compression stroke. May be divided into a plurality of times for injection. In short, even if the cooling water temperature is low, there is a temperature range that can achieve low fuel consumption and low emissions if split injection is used.Therefore, the temperature range on the low temperature side is divided into a cryogenic region and a low temperature region. The intake stroke injection is performed, and the split injection is performed in the intake stroke and / or the compression stroke in the low temperature region, thereby improving the combustibility in the low temperature region and realizing low fuel consumption and low emission. it can.

  By the way, at extremely low temperatures, even if a boost start is performed, the required injection amount is large, so the fuel pressure drops significantly at each injection and the fuel pressure pulsates, causing the actual injection amount to become unstable and misfire. there's a possibility that.

  As a countermeasure against this, as in claim 4, the required injection amount at the time of start is calculated by the required injection amount calculation means, the fuel pressure decrease amount due to injection is estimated based on this required injection amount, and this fuel pressure decrease amount is a predetermined value. In the above case, fuel injection at start-up may be executed regardless of the detected fuel pressure of the fuel pressure detecting means. In this way, when it is determined that the amount of fuel pressure reduction due to injection is large, fuel injection at start-up is performed without performing boost start-up, so that the feed pressure (electric motor that supplies fuel to the high-pressure pump is The fuel injection is performed in the vicinity of the pump discharge pressure). As a result, the fuel pressure pulsation at the time of starting is reduced, the actual injection amount is stabilized, and the effect of making it difficult to misfire is obtained.

  In this case, the process of estimating the fuel pressure decrease amount due to injection based on the required injection amount is omitted, and it is determined that the fuel pressure decrease amount due to injection is large when the required injection amount is a predetermined value or more as in claim 5. Then, fuel injection at the start may be executed regardless of the detected fuel pressure of the fuel pressure detecting means.

  According to another aspect of the present invention, the fuel discharge amount per cycle of the high-pressure pump and the fuel consumption amount due to the injection are estimated at the start, and when the fuel discharge amount is smaller than the fuel consumption amount due to the injection, the fuel pressure detecting means The fuel injection at start-up may be executed regardless of the detected fuel pressure. In short, when the amount of fuel consumed by injection is greater than the amount of fuel discharged, it is determined that the amount of fuel pressure reduction due to injection is large, and fuel injection at start-up is executed regardless of the fuel pressure detected by the fuel pressure detection means It is.

  Several embodiments embodying the best mode for carrying out the present invention will be described below.

  A first embodiment of the present invention will be described with reference to FIGS. First, the configuration of the entire fuel supply system of the direct injection engine will be described with reference to FIG. A low-pressure pump 12 that pumps up fuel is installed in the fuel tank 11 that stores the fuel. The low-pressure pump 12 is driven by an electric motor (not shown) that uses a battery (not shown) as a power source. The fuel discharged from the low pressure pump 12 is supplied to the high pressure pump 14 through the fuel pipe 13. A pressure regulator 15 is connected to the fuel pipe 13, and the pressure regulator 15 regulates the feed pressure of the low-pressure pump 12 (fuel supply pressure to the high-pressure pump 14) to a predetermined pressure. Is returned to the fuel tank 11 by a fuel return pipe 16.

  As shown in FIG. 2, the high-pressure pump 14 is a piston pump that sucks / discharges fuel by reciprocating a piston 19 in a cylindrical pump chamber 18. The piston 19 is fitted to a camshaft 20 of the engine. It is driven by the rotational movement of the cam 21. On the suction port 23 side of the high-pressure pump 14, a fuel pressure control valve 22 comprising a normally open type electromagnetic valve is provided. During the intake stroke of the high-pressure pump 14 (when the piston 19 is lowered), the fuel pressure control valve 22 is opened and fuel is sucked into the pump chamber 18, and during the discharge stroke (when the piston 19 is raised), the fuel pressure control valve. By controlling the valve closing time 22 (the valve closing time from the valve closing start time to the top dead center of the piston 19), the discharge amount of the high-pressure pump 14 is controlled to control the fuel pressure (discharge pressure). That is, when raising the fuel pressure, the valve closing start timing (energization timing) of the fuel pressure control valve 22 is advanced to extend the valve closing time of the fuel pressure control valve 22 and increase the discharge amount of the high-pressure pump 14. In addition, when the fuel pressure is reduced, the valve closing start time (energization timing) of the fuel pressure control valve 22 is retarded, thereby shortening the valve closing time of the fuel pressure control valve 22 and reducing the discharge amount of the high pressure pump 14 ( (See FIG. 9).

  On the other hand, a check valve 25 for preventing the backflow of discharged fuel is provided on the discharge port 24 side of the high-pressure pump 14. The fuel discharged from the high-pressure pump 14 is sent to a delivery pipe 27 through a high-pressure fuel pipe 26, and high-pressure fuel is distributed from the delivery pipe 27 to a fuel injection valve 28 attached to each cylinder head of the engine for each cylinder. . The high pressure fuel pipe 26 is provided with a fuel pressure sensor 29 (fuel pressure detecting means) for detecting a fuel pressure, and an output signal of the fuel pressure sensor 29 is input to an engine control circuit (hereinafter referred to as “ECU”) 30.

  The ECU 30 is mainly composed of a microcomputer, and is used to monitor engine operating conditions such as a cooling water temperature sensor 32 (cooling water temperature detecting means) for detecting the cooling water temperature of the engine, engine rotation speed, intake pipe pressure (or intake air amount), and the like. The output signals of various sensors to be detected are read, the required injection timing, the required injection amount, the required ignition timing, etc. are calculated, the fuel injection valve 28 is driven in accordance with the required injection timing, and fuel injection is performed. Ignition is performed by applying a high voltage to the spark plug according to the timing.

  Further, the ECU 30 executes each routine for boosting start control described later stored in a built-in ROM (storage medium), so that when the detected fuel pressure of the fuel pressure sensor 29 is equal to or lower than a predetermined injection permission fuel pressure at the start. The fuel pressure is detected after the fuel pressure detected by the fuel pressure sensor 29 exceeds the fuel pressure permitted for injection regardless of the coolant temperature detected by the coolant temperature sensor 32 and fuel injection at the start is prohibited to give priority to the increase in fuel pressure. When the injection is started, it is determined whether the detected coolant temperature of the coolant temperature sensor 32 corresponds to one of the three temperature ranges of low temperature, medium temperature, and high temperature, and the injection timing at the start is taken in the intake stroke in the low temperature region and the high temperature region. In the middle temperature region, the injection timing at the start is set to the compression stroke.

  By the way, in a conventional system that performs boosting start-up, as shown in FIG. 3, when the cooling water temperature at the time of starting is low, compression stroke injection and boosting start-up are performed in order to avoid problems such as smoke generation and start feeling deterioration. Start with intake stroke injection with prohibition, and when the cooling water temperature is high at the time of start-up, the injection amount decreases, so it becomes difficult to form a stratified mixture that is easy to burn, etc. Starting is prohibited and intake stroke injection is started.

  However, if the boosting start / stop operation is switched according to the cooling water temperature, the start time suddenly changes due to a slight difference in the cooling water temperature in the vicinity of the switching temperature, giving the driver a sense of incongruity (enclosed by the dotted line in FIG. 3). portion). That is, in the boost start, since the fuel injection is stopped during the boost time until the fuel pressure is increased to the injection permitted fuel pressure, it is inevitable that the start time becomes longer than the normal start by the intake stroke injection. Therefore, if the boosting start is completely prohibited at low water temperature or high water temperature, the start-up time is suddenly shortened despite the low water temperature starting, or the cooling water temperature is slightly higher on the high water temperature side. The starting time may be suddenly shortened just by becoming, which causes the driver to feel uncomfortable.

  Therefore, in the first embodiment, as shown in FIG. 3, regardless of the cooling water temperature at the time of starting, the boost start is executed in the entire temperature range, and when the fuel injection is started, the intake air is taken in the low temperature range and the high temperature range. The engine is started with stroke injection, and is started with compression stroke injection in the intermediate temperature range.

  The boost start control according to the first embodiment is executed by the ECU 30 according to the routines shown in FIGS. The processing contents of each routine will be described below.

  The boost start control routine of FIG. 5 is started at a predetermined cycle (for example, 8 ms cycle) during the ON period of the IG switch, and serves as a start control means in the claims. When this routine is started, first, at step 101, it is determined whether or not the boost start precondition is satisfied based on the processing result of the boost start precondition determining routine of FIG. If not, the routine proceeds to step 108 where the injection is permitted, and at the next step 109, the injection mode at the start is set to the intake stroke injection mode. In this case, the boosting start is not performed but the intake stroke injection is started.

  On the other hand, if it is determined in step 101 that the boost start precondition is satisfied, the process proceeds to step 102, in which it is determined whether the detected fuel pressure of the fuel pressure sensor 29 is lower than the injection permission fuel pressure. If it is lower than the injection permission fuel pressure, the routine proceeds to step 107, where "pressure increase start" is executed in which fuel injection at the start is prohibited and priority is given to the increase in fuel pressure.

  After that, when the detected fuel pressure becomes equal to or higher than the injection permitted fuel pressure, the routine proceeds to step 103, where it is determined whether or not a predetermined time has elapsed after the start, and if the predetermined time has elapsed after the start, the injection control at the start is performed. It is determined that the processing has ended, and this routine ends.

  On the other hand, if it is determined in step 103 that the predetermined time has not elapsed since the start, the process proceeds to step 104 where the cooling water temperature detected by the cooling water temperature sensor 32 is within a predetermined temperature range [TWL (eg, 0 ° C) <cooling water temperature <TWH (for example, 40 ° C.)], and if the cooling water temperature is within a predetermined temperature range (medium temperature region), the process proceeds to step 105 to compress the injection mode at the start Set to stroke injection mode and start. If it is determined in step 104 that the cooling water temperature is outside the predetermined temperature range (that is, a low temperature region below TWL or a high temperature region above TWH), the process proceeds to step 106 and the injection mode at the start is changed to the intake stroke injection mode. Set to start.

  The boost start precondition determination routine of FIG. 6 is started at a predetermined cycle (for example, 8 ms cycle) during the ON period of the IG switch, and determines whether the boost start precondition is met or not as follows. When this routine is started, first, in step 110, it is determined whether or not the high-pressure system is normal based on the diagnosis result of the self-diagnosis function implemented in the ECU 30, and if the high-pressure system is determined to be abnormal. If YES, the routine proceeds to step 115, where it is determined that the boost start prerequisite is not satisfied, and this routine is terminated.

  On the other hand, if it is determined in step 110 that the high-pressure system is normal, the process proceeds to step 111, the cooling water temperature at the time of start detected by the cooling water temperature sensor 32 is read, the process proceeds to step 112, and the start of FIG. A required start injection amount Qst corresponding to the cooling water temperature at the start is calculated using the required injection amount calculation map. The calculation map of the required injection amount at start in FIG. 7 is set so that the required injection amount Qst at start increases as the coolant temperature at the start decreases. The processing in step 112 serves as a required injection amount calculation means in the claims.

  Thereafter, the process proceeds to step 113, and the fuel pressure decrease amount PRdown corresponding to the start required injection amount Qst is calculated using the fuel pressure decrease amount calculation map of FIG. This fuel pressure decrease amount PRdown is a fuel pressure decrease amount that is generated by fuel injection at the start required injection amount Qst. The fuel pressure decrease amount calculation map of FIG. 8 is set so that the fuel pressure decrease amount PRdown increases as the starting required injection amount Qst increases.

  After calculating the fuel pressure reduction amount PRdown, the routine proceeds to step 114, where it is determined whether or not the fuel pressure reduction amount PRdown is larger than the predetermined value P0. If the fuel pressure reduction amount PRdown is larger than the predetermined value P0, the routine proceeds to step 115, where the pressure rises. It is determined that the starting precondition is not satisfied. When the boosting start precondition is not satisfied, boosting startup is prohibited regardless of the fuel pressure detected by the fuel pressure sensor 29, and fuel injection at startup is executed without boosting startup.

  On the other hand, if it is determined in step 114 that the fuel pressure decrease amount PRdown is equal to or less than the predetermined value P0, the process proceeds to step 116, and it is determined that the boost start prerequisite is satisfied. When the boosting start precondition is satisfied, if the detected fuel pressure of the fuel pressure sensor 29 is lower than the injection permission fuel pressure, the fuel injection at the start is prohibited and the boosting start is executed.

  In the first embodiment described above, when the detected fuel pressure of the fuel pressure sensor 29 is equal to or lower than the injection permission fuel pressure at the start, the boost start is executed in the entire temperature range regardless of the coolant temperature at the start, and the fuel pressure sensor 29 When the fuel injection is started after the detected fuel pressure exceeds the permitted fuel pressure, the engine is started with the intake stroke injection in the low temperature region and the high temperature region, and is started with the compression stroke injection in the intermediate temperature region. It is possible to prevent the start time from changing suddenly due to the difference, and to eliminate the driver's uncomfortable feeling, and it is possible to solve the problem of smoke generation at low water temperature and deterioration of the start feeling by the intake stroke injection.

  In addition, since the intake stroke injection at the start is performed in the high temperature region, unlike the compression stroke injection, it is not necessary to significantly retard the ignition timing at the start. For this reason, it is not necessary to advance the ignition timing significantly after starting, which can solve the problem of torque shock due to the advance of the ignition timing after starting, and it becomes difficult to form a stratified mixture that easily burns in a high temperature region. This problem can be solved by using the intake stroke injection.

  By the way, when the required injection amount Qst at the start is large, even if the boosting start is performed, the fuel pressure is greatly reduced and the fuel pressure pulsates for each injection, and the actual injection amount becomes unstable and misfires due to the influence. there's a possibility that.

  On the other hand, in the first embodiment, when it is determined that the fuel pressure reduction amount PRdown due to the fuel injection of the required injection amount Qst at the start is larger than the predetermined value P0, regardless of the detected fuel pressure of the fuel pressure sensor 29, Since the fuel injection at the start is executed without performing the boosting start, the fuel injection is executed near the feed pressure (the discharge pressure of the low pressure pump 12 that supplies fuel to the high pressure pump 14) at the start. In addition, the fuel pressure pulsation at the start is reduced, the actual injection amount is stabilized, and the effect of making it difficult to misfire is obtained.

  In this case, the process of calculating the fuel pressure decrease amount PRdown corresponding to the startup required injection amount Qst is omitted, and when the startup required injection amount Qst is equal to or greater than a predetermined value, it is determined that the fuel pressure decrease amount PRdown due to injection is large. Thus, fuel injection at start-up may be executed irrespective of the fuel pressure detected by the fuel pressure sensor 29.

  Needless to say, the temperatures TWL and TWH for dividing the low temperature region, the intermediate temperature region, and the high temperature region may be changed as appropriate.

  In the first embodiment, when the fuel pressure decrease amount PRdown due to the fuel injection of the required injection amount Qst at the time of start is larger than the predetermined value P0, regardless of the fuel pressure detected by the fuel pressure sensor 29, the boost start is not performed and In the second embodiment of the present invention shown in FIG. 10, the fuel discharge amount Qpump per cycle (360 ° C. A) of the high-pressure pump 14 and the fuel consumption amount Qstsum by injection are calculated at the start. When the calculated fuel consumption amount Qstsum is larger than the fuel discharge amount Qpump, the fuel injection at the start is executed without performing the boost start regardless of the fuel pressure detected by the fuel pressure sensor 29. Yes. In short, when the fuel consumption amount Qstsum by injection is larger than the fuel discharge amount Qpump, it is determined that the fuel pressure decrease amount by injection is large, and fuel injection at the time of starting is executed without performing boosting start.

  In the second embodiment, the boost start prerequisite condition determination routine of FIG. 10 is executed at a predetermined cycle (for example, 8 ms cycle) during the ON period of the IG switch. When this routine is started, first, at step 210, it is determined whether or not the high-pressure system is normal based on the diagnosis result of the self-diagnosis function implemented in the ECU 30, and if the high-pressure system is determined to be abnormal. If so, the process proceeds to step 217, where it is determined that the boost start prerequisite is not satisfied, and this routine is terminated.

  On the other hand, if it is determined in step 210 that the high-pressure system is normal, the process proceeds to step 211, the cooling water temperature at the time of start detected by the cooling water temperature sensor 32 is read, the process proceeds to step 212, and the start of FIG. A required start injection amount Qst corresponding to the cooling water temperature at the start is calculated using the required injection amount calculation map.

  Thereafter, the process proceeds to step 213, where the energization timing TPon of the high-pressure pump 14 (opening start timing of the fuel pressure control valve 22) is read. In the next step 214, the high-pressure pump 14 is turned on based on the energization timing Tpon of the high-pressure pump 14. The fuel discharge amount Qpump per cycle (360 ° C. A) is calculated using the high pressure pump discharge amount calculation map shown in FIG.

In the next step 215, the fuel consumption amount Qstsum by the injection per cycle (360 ° C. A) of the high-pressure pump 14 is calculated. For example, in a four-cylinder engine, injection is performed twice per cycle (360 ° C. A) of the high-pressure pump 14, so the fuel consumption amount Qstsum is equal to two injections of the required injection amount Qst at start calculated in step 212. It becomes.
Qstsum = Qst × 2

  Thereafter, the process proceeds to step 216, where it is determined whether or not the fuel discharge amount Qpump is smaller than the fuel consumption amount Qstsum. If the fuel discharge amount Qpump is smaller than the fuel consumption amount Qstsum, the flow proceeds to step 217 and the boost start precondition Is determined to be not established. When the boosting start precondition is not satisfied, boosting startup is prohibited regardless of the fuel pressure detected by the fuel pressure sensor 29, and fuel injection at startup is executed without boosting startup.

On the other hand, if it is determined in step 216 that the fuel discharge amount Qpump is equal to or greater than the fuel consumption amount Qstsum, the flow proceeds to step 218, where it is determined that the boost start-up precondition is satisfied. When the boosting start precondition is satisfied, if the detected fuel pressure of the fuel pressure sensor 29 is lower than the injection permission fuel pressure, the fuel injection at the start is prohibited and the boosting start is executed. Other processes are the same as those in the first embodiment.
Also in the second embodiment described above, the same effect as in the first embodiment can be obtained.

  In the first embodiment, when the fuel injection is started after the detected fuel pressure of the fuel pressure sensor 29 exceeds the injection permission fuel pressure, the detected coolant temperature of the coolant temperature sensor 32 falls into any of the three temperature ranges of low temperature, medium temperature, and high temperature. In the low temperature region and the high temperature region, the injection timing at the start is set to the intake stroke, and in the intermediate temperature region, the injection timing at the start is set to the compression stroke. In the third embodiment, when the fuel injection is started after the detected fuel pressure of the fuel pressure sensor 29 exceeds the injection permission fuel pressure, the detected coolant temperature of the coolant temperature sensor 32 is four temperature ranges of extremely low temperature, low temperature, medium temperature, and high temperature. In the extremely low temperature region and the high temperature region, the injection timing at the start is set to the intake stroke, in the intermediate temperature region, the injection timing at the start is set to the compression stroke, and in the low temperature region, the intake stroke and / Or compression process By dividing the fuel a plurality of times are to be injected.

  In short, even if the cooling water temperature is low, there is a temperature range that can achieve low fuel consumption and low emissions if split injection is used.Therefore, the temperature range on the low temperature side is divided into a cryogenic region and a low temperature region. The intake stroke injection is performed, and the split injection is performed in the intake stroke and / or the compression stroke in the low temperature region, thereby improving the combustibility in the low temperature region and realizing low fuel consumption and low emission. it can.

  The boost start control routine of FIG. 11 executed in the third embodiment is obtained by adding the processing of step 104a and step 106a to the boost start control routine of FIG. 5 described in the first embodiment. The process is the same.

  In the boost start control routine of FIG. 11, when the fuel pressure detected by the fuel pressure sensor 29 exceeds the injection permission fuel pressure and the fuel injection is started, the cooling water temperature detected by the cooling water temperature sensor 32 in step 104 is the medium temperature region [TWL (for example, 0 ° C) <cooling water temperature <TWH (for example, 40 ° C)], and if the cooling water temperature is in the middle temperature range, the process proceeds to step 105, and the injection mode at the start is set to the compression stroke injection mode. Start.

  If it is determined in step 104 that the cooling water temperature is not in the intermediate temperature region, the process proceeds to step 104a, where the cooling water temperature is in the low temperature region [TWLL (eg, −10 ° C.) <Cooling water temperature <TWL (eg, 0 ° C.)]. If the cooling water temperature is in the low temperature range, the process proceeds to step 106a, and the injection mode at the start is set to the divided injection mode and the engine is started. In this divided injection mode, any one of the following divided injections (1) to (3) is performed.

(1) The fuel is divided into a plurality of times and injected over the intake stroke and the compression stroke.
(2) The fuel is divided into multiple injections during the intake stroke.
(3) The fuel is divided into multiple injections during the compression stroke.

  On the other hand, when it is determined as “No” in step 104a, that is, when the cooling water temperature is a very low temperature region of TWLL (for example, −10 ° C.) or lower or a high temperature region of TWH (for example, 40 ° C.) or higher. Then, the routine proceeds to step 106, where the start-up injection mode is set to the intake stroke injection mode and the start is started. Other processes are the same as those in the first embodiment.

  In the third embodiment described above, even if the coolant temperature is low, if the divided injection is used, the divided injection is performed in the temperature range (low temperature range) where low fuel consumption and low emission can be realized. This can improve flammability and achieve low fuel consumption and low emissions.

Needless to say, the temperatures TWLL, TWL, and TWH for dividing the extremely low temperature region, the low temperature region, the intermediate temperature region, and the high temperature region may be appropriately changed.
In addition, the present invention can be implemented with various modifications such as an engine having an excellent ability to form a stratified mixture by compression stroke injection, such that compression stroke injection may be performed even in a high temperature region.

It is a figure which shows schematic structure of the whole fuel-injection system in Example 1 of this invention. It is a block diagram of a high pressure pump. It is a figure explaining the relationship between the conventional cooling water temperature at the time of starting, and starting time. It is a figure explaining the relationship between the cooling water temperature at the time of start of Example 1, and start time. 3 is a flowchart illustrating a processing flow of a boost start control routine according to the first embodiment. 6 is a flowchart illustrating a processing flow of a boost start prerequisite condition determination routine according to the first embodiment. It is a figure which shows an example of the map which calculates the starting injection quantity Qst at the time of the cooling water temperature at the start of Example 1 as a parameter. It is a figure which shows an example of the map which calculates fuel pressure fall amount PRdown by using the injection quantity Qst at the time of start of Example 1 as a parameter. It is a figure which shows an example of the map which calculates the fuel discharge amount of a high pressure pump by making into energization timing Tpon of the flow control valve of the high pressure pump of Example 1 a parameter. 7 is a flowchart illustrating a processing flow of a boost start prerequisite condition determination routine according to a second embodiment. 12 is a flowchart illustrating a processing flow of a boost start control routine according to a third embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Fuel tank, 12 ... Low pressure pump, 14 ... High pressure pump, 15 ... Pressure regulator, 19 ... Piston, 20 ... Cam shaft, 21 ... Cam, 22 ... Fuel pressure control valve, 25 ... Check valve, 27 ... Delivery pipe, 28 ... Fuel injection valve, 29 ... Fuel pressure sensor (fuel pressure detecting means), 30 ... ECU (starting control means), 32 ... Cooling water temperature sensor (cooling water temperature detecting means)

Claims (6)

In the in-cylinder injection type internal combustion engine start control device in which fuel is made high pressure by a high pressure pump and supplied to the fuel injection valve, and fuel is directly injected into the cylinder from the fuel injection valve.
Fuel pressure detecting means for detecting the pressure of fuel supplied to the fuel injection valve (hereinafter referred to as “fuel pressure”);
Cooling water temperature detecting means for detecting the cooling water temperature of the internal combustion engine;
When the detected fuel pressure of the fuel pressure detecting means is less than a predetermined fuel pressure at the start, the fuel injection at the start is prohibited regardless of the coolant temperature detected by the cooling water temperature detecting means to prioritize the increase of the fuel pressure, and the detection of the fuel pressure detecting means When the fuel injection starts after the fuel pressure exceeds the predetermined fuel pressure, if the detected coolant temperature of the coolant temperature detecting means is below the predetermined temperature, the injection timing at the start is set to the intake stroke, and otherwise, And a start control means for setting the injection timing to a compression stroke. A start control device for a cylinder injection type internal combustion engine, comprising: In the in-cylinder injection type internal combustion engine start control device in which fuel is made high pressure by a high pressure pump and supplied to the fuel injection valve, and fuel is directly injected into the cylinder from the fuel injection valve.
Fuel pressure detecting means for detecting the pressure of fuel supplied to the fuel injection valve (hereinafter referred to as “fuel pressure”);
Cooling water temperature detecting means for detecting the cooling water temperature of the internal combustion engine;
When the detected fuel pressure of the fuel pressure detecting means is less than a predetermined fuel pressure at the start, the fuel injection at the start is prohibited regardless of the coolant temperature detected by the cooling water temperature detecting means to prioritize the increase of the fuel pressure, and the detection of the fuel pressure detecting means When fuel injection is started after the fuel pressure exceeds the predetermined fuel pressure, it is determined whether the detected coolant temperature of the coolant temperature detection means falls into one of the three temperature ranges of low temperature, medium temperature, and high temperature, and the low temperature region and the high temperature region are detected. And a start control means for setting the injection timing at the start to the intake stroke in the region and the injection timing at the start to the compression stroke in the intermediate temperature region. Control device. In the in-cylinder injection type internal combustion engine start control device in which fuel is made high pressure by a high pressure pump and supplied to the fuel injection valve, and fuel is directly injected into the cylinder from the fuel injection valve.
Fuel pressure detecting means for detecting the pressure of fuel supplied to the fuel injection valve (hereinafter referred to as “fuel pressure”);
Cooling water temperature detecting means for detecting the cooling water temperature of the internal combustion engine;
When the detected fuel pressure of the fuel pressure detecting means is less than a predetermined fuel pressure at the start, the fuel injection at the start is prohibited regardless of the coolant temperature detected by the cooling water temperature detecting means to prioritize the increase of the fuel pressure, and the detection of the fuel pressure detecting means When fuel injection is started after the fuel pressure exceeds a predetermined fuel pressure, it is determined whether the detected coolant temperature of the coolant temperature detection means falls into one of four temperature ranges of extremely low temperature, low temperature, medium temperature, and high temperature. In the low temperature region and the high temperature region, the injection timing at the start is set to the intake stroke, in the intermediate temperature region, the injection timing at the start is set to the compression stroke, and in the low temperature region, the fuel is divided into multiple times in the intake stroke and / or the compression stroke. A start control device for in-cylinder injection type internal combustion engine. Equipped with a required injection amount calculating means for calculating a required injection amount at the start,
The start control means estimates a fuel pressure decrease amount due to injection based on the required injection amount, and when the fuel pressure decrease amount is equal to or greater than a predetermined value, fuel injection at start is performed regardless of the detected fuel pressure of the fuel pressure detection means. The start control device for a cylinder injection type internal combustion engine according to any one of claims 1 to 3, wherein: Equipped with a required injection amount calculating means for calculating a required injection amount at the start,
4. The fuel injection system according to claim 1, wherein when the required injection amount is equal to or greater than a predetermined value, the start control unit executes fuel injection at the start regardless of the detected fuel pressure of the fuel pressure detecting unit. A start-up control device for an in-cylinder internal combustion engine as described in 1.   The start control means estimates a fuel discharge amount per cycle of the high-pressure pump and a fuel consumption amount by injection at the start, and when the fuel consumption amount by injection is larger than the fuel discharge amount, the fuel pressure detection means 6. The start control device for a cylinder injection type internal combustion engine according to claim 1, wherein fuel injection at the time of start is executed irrespective of the detected fuel pressure.

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