JPH09222037A - Control device for cylinder direct injection type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To start the feed of fuel from an optimum cycle according to an engine state during the starting of a cylinder direct injection type internal combustion engine. SOLUTION: Based on the results of an operation state detecting means A to detect the operation state of an engine and a fuel feed amount computing means B to calculate a fuel feed amount during the starting of an engine, a fuel pressure lower limit value computing means C calculates the lower limit value (a fuel pressure lower limit value) of a fuel pressure demanded during starting and a fuel pressure estimating means D estimates a fuel pressure (a fuel pressure estimating value) after the feed of fuel. A fuel feed starting cylinder deciding means E compares the fuel pressure estimating value with the fuel pressure lower limit, and when the fuel pressure estimating value exceeds the fuel pressure lower limit, fuel is fed to a cylinder to which a fuel feed timing comes. When the fuel pressure estimating value is below the fuel pressure lower limit, the feed of fuel is not effected and at a next fuel feed timing, similar processing described above is effected and a cylinder to start the feed of fuel is decided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine of an automobile or the like, and more particularly to a control device for a direct injection type internal combustion engine having a direct injection injector for directly injecting fuel at high pressure into the cylinder. Regarding

[0002]

2. Description of the Related Art In a cylinder direct injection type internal combustion engine, in consideration of atomization of fuel, the engine is surely started at the time of starting.
It is desirable to supply after the fuel pressure (hereinafter referred to as fuel pressure) becomes high. Therefore, conventionally, a high fuel pressure is generated using a mechanically driven high-pressure fuel pump in consideration of fuel consumption and efficiency.

However, when the engine is started, the high-pressure fuel pump becomes a load, and the increase in the engine speed is delayed, and the increase in the fuel pressure is also delayed. Therefore, the fuel is supplied after waiting for the fuel pressure to sufficiently increase. Then, as a result, the start of the engine may be delayed. Also, if the fuel supply is too early while the fuel pressure is insufficient to speed up the start,
Depending on the operating conditions, the fuel supply amount may be insufficient, resulting in poor combustion or misfire, which may lead to deterioration of exhaust gas or startability.

In order to avoid such an inconvenience
In the 4-311637 publication, in an internal combustion engine equipped with a direct injection injector, when the engine speed at startup is lower than a predetermined value, the supply of fuel is started at the end of the compression stroke, and the injected fuel is injected. Is stratified around the spark plug, and when the engine speed is higher than a predetermined value, fuel is supplied when the exhaust valve closes to form a uniform mixture in the combustion chamber. There is disclosed a technique for burning the fuel. This is intended to realize a rapid increase in engine speed without deteriorating exhaust gas and startability.

[0005]

However, in such a conventional control apparatus for a direct injection type internal combustion engine, only the rotational speed at the time of engine start is focused, and the fuel supply amount and the fuel pressure are controlled. The state is not taken into consideration, and the first fuel supply at the start is always started in a predetermined cycle. For this reason, if the fuel supply start cycle is set earlier, the supply amount may be insufficient if the fuel pressure is low, and exhaust failure may be deteriorated due to poor combustion or misfire. When set late, there is a problem that it takes more time than necessary to start the engine even under good conditions where the temperature is high and quick start is possible.

In view of the above-mentioned conventional problems, the present invention is based on the engine speed at the engine start, the fuel supply amount, the fuel pressure increase characteristic of the fuel pump, the fuel pressure detection value, the fuel temperature detection value, etc. An object of the present invention is to provide a control device for a direct injection type internal combustion engine, capable of variably controlling a fuel supply start cycle in accordance with an operating state and starting fuel supply from an optimum cycle.

[0007]

Therefore, according to the present invention, under the condition that a large amount of fuel needs to be supplied at the time of starting and the engine speed is low and the increase in fuel pressure is slow, such as when the temperature is low, Basically, the fuel is supplied after waiting for the fuel pressure to rise sufficiently to prevent exhaust and startability from deteriorating. On the other hand, under conditions where a small amount of fuel needs to be supplied at startup and the engine speed is high and the fuel pressure rises quickly, such as when the temperature is high, by starting fuel supply in a relatively early cycle, the engine starts quickly. To realize.

Specifically, in the invention according to claim 1, in a control device for a direct injection type internal combustion engine, in which fuel is directly injected into a cylinder at a high pressure by a direct injection injector,
As shown in FIG. 1, an operating state detecting means A for detecting an operating state of the engine, a fuel supply amount calculating means B for calculating a fuel supply amount at the time of starting the engine, a detection result of the operating state detecting means and the fuel. Based on the calculation result of the supply amount calculation means, the fuel pressure lower limit value calculation means C for calculating the lower limit value of the fuel pressure required at the time of starting, the detection result of the operating state detection means, and the calculation of the fuel supply amount calculation means Based on the result, the fuel pressure estimating means D for estimating the change of the fuel pressure when the fuel is supplied, the fuel pressure lower limit value calculating means and the fuel pressure estimating means, and the fuel supply at the time of starting. And a fuel supply start cylinder determining means E for determining a cylinder to start the fuel injection.

Further, in the invention according to claim 2, the operating state detecting means A detects the crank angle of the engine by the crank angle sensor installed in the internal combustion engine, and based on this, the engine speed is determined. It is characterized by being calculated. Further, the invention according to claim 3 is characterized in that the fuel supply amount calculation means B determines the fuel supply amount at the time of starting the engine based on the cooling water temperature of the engine.

Further, in the invention according to claim 4, the fuel pressure lower limit value calculating means C has a maximum time during which fuel can be supplied, which is calculated based on the crank angle detected by the operating state detecting means A, and the fuel. From the supply amount calculated by the supply amount calculation means B, the lower limit value of the fuel pressure required to finish supplying the supply amount within the maximum time is calculated.

Further, in the invention according to claim 5, the fuel pressure lower limit value calculating means C is provided with a limiter for limiting the minimum value of the fuel pressure lower limit value, and the fuel pressure lower limit value correcting means for correcting the calculated lower limit value of the fuel pressure. It is characterized in that it is configured to include. Further, in the invention according to claim 6, the fuel pressure estimating means D is a crank angle detected by the operating state detecting means A, a fuel supply amount calculated by the fuel supply amount calculating means B, and a known fuel pump. It is characterized in that a change in fuel pressure after fuel supply is estimated from the characteristics.

Further, in the invention according to claim 7, the internal combustion engine is provided with a fuel pressure sensor for detecting fuel pressure, while the fuel pressure estimating means D has a crank angle detected by the operating state detecting means A and the fuel. It is characterized in that the change in fuel pressure is estimated from the fuel supply amount calculated by the supply amount calculation means B, the known characteristics of the fuel pump, and the output of the fuel pressure sensor.

Further, in the invention according to claim 8, the internal combustion engine is provided with a fuel temperature sensor for detecting a fuel temperature, while the fuel pressure estimating means D has a crank angle detected by the operating state detecting means A, and It is characterized in that a change in fuel pressure is estimated from the fuel supply amount calculated by the fuel supply amount calculation means B, the known characteristics of the fuel pump, and the output of the fuel temperature sensor.

Further, in the invention according to claim 9, the fuel supply start cylinder determination means E, the estimated value of the fuel pressure after the fuel supply calculated by the fuel pressure estimation means D, and the fuel pressure lower limit value calculation means C. The fuel pressure lower limit value calculated by the above is compared, and when the fuel pressure estimated value is equal to or higher than the fuel pressure lower limit value, fuel is supplied to the cylinder at the fuel supply timing, and the fuel pressure estimated value is the fuel pressure lower limit value. When it is smaller than the above, the fuel supply is not performed, and the same processing is performed at the next fuel supply timing to determine the cylinder to start the fuel supply.

Further, the invention according to claim 10 is characterized in that the present control is terminated when a predetermined period has elapsed after the engine was started.

[0016]

According to the present invention, the engine speed at start-up, the fuel supply amount, the fuel pressure increase characteristic due to the characteristics of the fuel pump, the fuel pressure detection value, the fuel temperature detection value, etc. are used to determine the operating state at that time. In this configuration, the fuel supply start cycle is variably controlled. Due to this, under conditions where it is necessary to supply a large amount of fuel at the time of starting, such as when the temperature is low, the engine speed is low, and the rise in fuel pressure is slow, wait until the fuel pressure rises sufficiently before supplying fuel. By doing so, it is possible to prevent deterioration of exhaust gas. Further, under a condition where a small amount of fuel is supplied at the time of starting, such as when the temperature is high, and the engine speed is high and the fuel pressure rises quickly, fuel supply is started in a relatively early cycle to achieve a quick start of the engine. As a result, it is possible to prevent deterioration of exhaust gas due to deterioration of combustion or misfire and deterioration of startability.

That is, according to the invention of claim 1,
Judging the fuel supply start timing at the time of starting with the direct injection type internal combustion engine, the deterioration of combustion and the deterioration of exhaust due to misfire,
This has the effect of preventing a delay in starting. Further, according to the invention of claim 2, there is an effect that the operating state of the engine can be detected easily and accurately, and the accurate control can be performed based on this.

According to the invention of claim 3, there is an effect that the fuel supply amount at the time of starting can be easily calculated.
According to the invention of claim 4, the optimum fuel pressure lower limit value is calculated based on the fuel supply amount and the engine speed. Therefore, even if the fuel supply amount and the engine speed at the start are different, This has the effect of preventing the startability from deteriorating.

Further, according to the invention of claim 5, since the correction is made by limiting the minimum value of the fuel pressure lower limit value,
Even when the fuel supply amount is small and the engine speed is slow, it is possible to prevent exhaust and startability from being deteriorated due to insufficient atomization of fuel. Further, according to the invention of claim 6, since the change of the fuel pressure is estimated from the characteristic of the fuel pump which is known in advance, there is an effect that the fuel pressure can be estimated easily and accurately.

Further, according to the invention of claim 7, the output value of the fuel pressure sensor is used to estimate the change in fuel pressure when fuel is supplied to the cylinder where the fuel supply timing comes from the next time onward. There is an effect that the fuel pressure can be estimated more accurately. Further, according to the invention of claim 8, there is an effect that the fuel pressure can be accurately estimated even when the fuel property changes due to the difference in the fuel temperature and the fuel pressure increase characteristic of the fuel pump changes.

According to the ninth aspect of the invention, there is an effect that the fuel can be satisfactorily and surely supplied by preventing the fuel pressure after the fuel supply from falling below the lower limit value of the fuel pressure. According to the invention of claim 10,
Since the execution of this control is limited to the predetermined period after starting,
There is an effect that it is possible to prevent the fuel supply from being erroneously stopped by this control during the normal operation after the start.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a sectional view of a direct injection internal combustion engine showing an embodiment of the present invention. In the engine 1, the throttle valve 2, surge tank 3, intake manifold 4
Intake is performed via the intake valve 5, and fuel is directly injected and supplied from the direct injection injector 6 into the combustion chamber 7.
Further, the spark plug 8 is provided so that an electrode for ignition faces the combustion chamber 7.

As a means for detecting the operating state of the engine 1,
An air flow meter 9 provided upstream of the throttle valve 2 for measuring the amount of intake air, a crank angle sensor (not shown) for measuring the crank angle position of the engine 1, and the like are provided. The crank angle sensor is directly or indirectly connected to a crank shaft or a cam shaft that rotates in conjunction with the crank shaft through a gear, and calculates the crank angle position (crank angle) and the rotation speed of the engine 1.

Further, the fuel pressure sensor 10 for detecting the fuel pressure of the supplied fuel is provided, and the air-fuel ratio is controlled by adjusting the fuel injection amount by the direct injection injector 6. In addition, a water temperature sensor 11 for measuring the engine cooling water temperature, an O ₂ sensor 12 for measuring the oxygen concentration in the exhaust gas, and the like are provided. Input / output of information to / from the outside and various calculations are realized by a circuit centered on the microcomputer shown in FIG. Various sensors such as the air flow meter 9 described above are connected to the input port 13, and the information thereof is input. In the A / D converter 14, an analog signal of the signals obtained from various sensors via the input port 13 is A / D converted so that it can be handled by a computer. And CPU
15 executes a predetermined calculation based on the input data, and the result is output from the output port 16 as a signal for driving / controlling an external device.

The ROM 17 previously stores a control program, various data, etc., which will be described later, and the RAM 18 temporarily stores information during execution of the program. In the above-mentioned conventional direct injection type internal combustion engine, the fuel supply amount at the start is determined based on the water temperature and the like, but the cycle for starting the fuel supply is generally fixed. Further, in the direct injection type internal combustion engine, it is necessary to make the fuel high pressure in order to atomize and supply the fuel in a short time, and in consideration of fuel efficiency and efficiency, a mechanical high pressure fuel driven by a camshaft etc. It uses a pump.

Therefore, in order to supply the fuel and start the engine, the pump must first discharge the high-pressure fuel. Further, in order for the pump to rotate and discharge the high-pressure fuel, the engine must rotate at a predetermined speed.
Here, when the engine speed at start is low due to low battery voltage, etc., and when a large amount of fuel needs to be supplied because the temperature is low, a large amount of fuel should be supplied at a low fuel pressure. As a result, the fuel pressure is further reduced, and the supply amount and atomization of the fuel become insufficient. As a result, combustion at the time of starting may be deteriorated, and in the worst case, misfire may occur, leading to exhaust and deterioration of startability.

Now, in the cylinder direct injection internal combustion engine,
Consider the case where fuel injection is performed in the intake stroke at the start. Generally, the opening and closing timing of the intake valve and exhaust valve is
It is set as shown in FIG. Here, the exhaust valve is opened at the beginning of the intake stroke, and if fuel is supplied, the fuel may be exhausted as it is, so fuel cannot be supplied. In the first half of the intake stroke as well, the piston is not lowered so much, and when fuel is supplied, fuel adheres to the piston and atomization becomes insufficient, which may deteriorate exhaust gas. On the other hand, if fuel is supplied immediately before the intake valve is closed, the piston may start rising, and the air-fuel mixture may be pushed back to the intake port side. Therefore, it is desirable to select a range of the crank angle for fuel supply such as the "fuel supply possible section" in FIG.

Generally, the fuel supply amount is determined by the product of the fuel supply time and the differential pressure between the fuel supply atmosphere pressure (in this case, the cylinder pressure) and the fuel pressure. Here, since the in-cylinder pressure at the time of starting is almost atmospheric pressure, when the fuel supply amount Ti is constant, the relationship between the fuel pressure Pfuel and the fuel supply time Tpulse is shown in FIG.
become that way. Further, the upper limit value T1 of the fuel supply time can be calculated from the engine speed N at that time and the fuel supply possible section of FIG. 4, and if the fuel supply amount is Ti1, then according to the relationship of FIG. The lower limit value P1 of the fuel pressure required to supply the fuel supply amount Ti1 to the fuel cell is obtained.

Even when the engine speed N is low and the fuel supply time can be long, the fuel pressure does not have to be low, and there is a minimum required fuel pressure for atomizing the supplied fuel. . Therefore, when this is taken into consideration, FIG.
It is necessary to further correct the fuel pressure lower limit value obtained from
Alternatively, as shown in FIG. 5, a lower limit limiter for the fuel pressure lower limit may be provided in advance.

FIG. 6 shows the fuel pressure increasing characteristics at the time of starting by the fuel pump when the fuel is not supplied into the cylinder, and the fuel pressure is steadily increasing with the passage of time. However, in reality, the fuel pressure decreases when fuel is supplied, and when the fuel pressure falls below the above-described fuel pressure lower limit value P1, the fuel supply amount becomes insufficient. An example will be described below in which a four-cylinder in-cylinder direct injection internal combustion engine uses a fuel pump that discharges four times per two revolutions of the engine. In all cases, the battery state, the cranking speed at the time of starting, and the upper limit value T1 of the fuel supply time are the same. Further, referring to FIG. 5, the fuel supply amount at high temperature is Ti1 (fuel pressure lower limit value is P1), and the fuel supply amount at low temperature is Ti2 (fuel pressure lower limit value is P2). Despite direct injection, the amount of fuel supplied at startup varies depending on the temperature.For example, when the temperature is low, the supplied fuel is scraped off from the cylinder to the crankcase so much that more fuel than is required for combustion is consumed. This is because the fuel must be supplied, but at the time of high temperature, almost no fuel is scraped off to the crankcase, so only the amount required for combustion needs to be supplied. Another reason is that the air density varies depending on the temperature, so that the required fuel amount varies.

In the case of Ti1 where the fuel supply amount is relatively small at high temperature, as shown in FIG. 7, even if the fuel injection pulse is output from the cylinder (# 1 cylinder) which first undergoes the intake stroke, the fuel pressure Pfuel is not so high. The fuel pressure does not drop significantly below the lower limit of the fuel pressure P1 even before the first explosion in the # 1 cylinder, and fuel is smoothly supplied to the subsequent cylinders (# 3 ~). It rises and reaches the target speed.

On the other hand, in the case of Ti2 where the fuel supply amount is relatively large at a low temperature, as shown in FIG. 8, when the fuel is first supplied to the cylinder (# 1 cylinder) which undergoes the intake stroke, the fuel pressure decreases. Then, the fuel pressure becomes lower than the lower limit P2, and the fuel supply amount of each cylinder (# 3 and # 4 cylinders) before the first explosion of the # 1 cylinder may be insufficient. As a result, even if the initial explosion occurs, the fuel supply amount to those cylinders (# 1, # 3, and # 4 cylinders) is insufficient, so the combustion deteriorates, the increase in rotational speed slows, and the startability deteriorates. At the same time, the exhaust gas deteriorates.

However, in such a case, before the fuel is supplied to the # 1 cylinder, the fuel pressure change due to the fuel supply is estimated in advance from the characteristics of the high-pressure fuel pump, the output of the fuel pressure sensor, the output of the fuel temperature sensor, etc. By determining whether the supply is possible, it is possible to avoid the inconvenience as described above. That is, as shown in FIG. 9, when it is estimated that the fuel pressure is lower than the lower limit P2, the fuel supply to the # 1 cylinder is not performed and the fuel pressure is increased. Then, it is judged again whether or not fuel can be supplied before the fuel is supplied to the next # 3 cylinder. If it is judged that the fuel pressure does not fall below the fuel pressure lower limit P2 even if the fuel is supplied to the # 3 cylinder, the fuel is supplied from the # 3 cylinder. To start. By doing so, it is possible to prevent deterioration of combustion or deterioration of exhaust gas due to misfire, and as a result, the target rotational speed is reached faster than when fuel is supplied from the first cylinder at a low fuel pressure. It is also possible.

A first embodiment for performing such processing will be described below. FIG. 10 is a routine for detecting the operating state, which corresponds to the operating state detecting means A. Here, it is assumed that the job is executed every fixed time (10 ms), but it may be executed at different timings such as a background job. In step 1001 (denoted as S1001 in the figure, the same applies hereinafter), the output of the crank angle sensor is read. In step 1002, the current crank angle is detected from the data read in step 1001. And in step 1003,
From the data read in step 1001, the engine speed N r
Calculate pm and exit this routine.

FIG. 11 shows a routine for calculating the fuel supply amount, which corresponds to the fuel supply amount calculating means B. This is executed in synchronization with the reference signal output from the crank angle sensor every 180 CA °. In step 1101, the water temperature Tw is read from the water temperature sensor 11, and in step 1102, the
From the table shown in FIG. 17, the value of the fuel supply amount Ti at the time of starting corresponding to the current water temperature Tw read in the previous stage is read (for example, if the water temperature is Tw1, the fuel supply amount Ti1), and this routine To finish.

FIG. 12 is a routine for calculating the lower limit value of the fuel pressure, which is executed for each reference signal. This corresponds to the fuel pressure lower limit value calculation means C. In step 1201, the predetermined fuel supplyable section C pulse ° CA shown in FIG. 4 is read, and in step 1202, the rotation speed N calculated in step 1003 of FIG. 10 is read. In step 1203, the read C
From pulse and N, the upper limit value T of fuel supply time is calculated by the following formula.
Calculate 1

T1 = Cpulse × 1000 / (6 × N) ms In the following step 1204, T1 calculated in step 1203 is calculated.
Then, based on the fuel supply amount read in step 1102 of FIG. 11, the fuel pressure lower limit value P is calculated from the table as shown in FIG. 5, and the process ends. If the fuel supply amount is Ti1, the fuel pressure lower limit value is P1 from FIG.

FIG. 13 is a routine for estimating the fuel pressure, which is executed for each reference. This corresponds to the fuel pressure estimating means D. Here, FIG. 18 shows the fuel pressure increase characteristics of the fuel pump corresponding to the crank angle, but it is premised that this is already known from experiments and the like. In step 1301, the previous estimated fuel pressure value Pest is read. However, since there is no previous estimated value in the case of the first reference after starting, the previous fuel pressure estimated value Pest is created based on the crank angle at the time of starting and a part of the characteristics of FIG. 18.

In step 1302, as shown in FIG. 20, the transition of the fuel pressure Ppump by the high-pressure fuel pump while the crank angle advances by 180 CA °, the final value of the previous estimated fuel pressure value read in step 1301 is set to the initial value. Is estimated from the characteristics of FIG. In the following step 1303, the fuel supply amount Ti1 obtained in the routine of FIG. 11 is read, and in step 1304, the fuel supply amount Ti1 is calculated from the relationship of FIG. 5 based on the fuel supply amount Ti1 and the fuel pressure Ppump of the high pressure fuel pump estimated in 1302. Calculate the time Tpulse.

In step 1305, the fuel supply time Tpu
The fuel pressure decrease rate when the lse pulse is output is calculated from the characteristics that have been examined in advance by experiments. When the fuel injection pulse width is the same, a large amount of fuel is injected when the fuel pressure is high, and the fuel pressure drops significantly, but when the fuel pressure is low, only a small amount of fuel is supplied, so the amount of decrease in fuel pressure is also small. It is considered that the ratio between the fuel pressure and the fuel pressure decrease amount is the same in both cases. Therefore, a table as shown in FIG. 19 in which the fuel supply time Tpulse and the fuel pressure decrease rate are simply proportional to each other can be used.

In step 1306, the fuel pressure transition Pdown during fuel supply is calculated from the fuel pressure Ppump of the pump estimated in step 1302 (FIG. 20) and the fuel pressure value reduction rate obtained in step 1305.
Is estimated as shown in FIG. 21, and this routine is finished. FIG. 14 is a routine for determining a cylinder for starting fuel supply, which is executed for each reference. This corresponds to the fuel supply cylinder determination means E.

In step 1401, the reduced fuel pressure value Pdown during fuel supply estimated in the routine of FIG. 13 is read, and in step 1402, the fuel pressure lower limit value P1 calculated in the routine of FIG. 12 is read. In the next step 1403, the two are compared,
When the estimated fuel pressure value Pdown is equal to or larger than the fuel pressure lower limit value P1 (Pdown ≧ P1), the routine proceeds to step 1404, where it is decided to supply fuel to the cylinder at the fuel supply timing as scheduled, and at step 1405, fuel supply is performed. The injection pulse of time Tpulse is set, and Pdown is substituted for Pest in step 1406, and the process is ended.

On the other hand, when the estimated fuel pressure value Pdown is smaller than the fuel pressure lower limit value P1 in step 1403 (Pdown <P1), the routine proceeds to step 1407, where the supply to the cylinder at the next fuel supply timing is stopped and the fuel is supplied. It is decided to postpone, and in step 1408, the estimated fuel pressure value Ppump when fuel is not supplied is substituted for Pest, and the process ends. With the above processing, based on the fuel supply amount Ti1 and the rotation speed N at the time of starting, it is possible to reliably start the engine according to the state at that time without causing deterioration of combustion or misfire. .

Although the routines shown in FIGS. 11 to 14 are all reference jobs, these routines are assumed to be sequentially executed in the ascending order of the figure. Also, this control is executed from the start, and after the first fuel supply is performed, a predetermined time (for example, 5 s
) Or after a predetermined combustion cycle (for example, 50 combustion cycles) has elapsed, the execution is terminated. Next, a second embodiment will be described.

In the first embodiment, there is no particular limitation when calculating the fuel pressure lower limit P1 in step 1204 of FIG. However, when the fuel supply amount is small or the rotation speed is low and the fuel supply time can be long, the fuel pressure lower limit value is calculated to be extremely low, and an extremely low fuel pressure is allowed, resulting in insufficient atomization of fuel. there is a possibility. To compensate for this point, a lower limit limiter for limiting the minimum fuel pressure lower limit may be provided to correct the calculated fuel pressure lower limit.
The value of the lower limiter may be a map value determined from the engine speed N and the fuel supply amount Ti as shown in FIG. 22, or may be a constant value as shown in FIG. 5 regardless of operating conditions.

In this case, as the fuel pressure lower limit value calculating means C,
The routine of FIG. 15 is used instead of the routine of FIG. Fig. 15
Routine is executed for each reference, step 1501
At 1504, the fuel pressure lower limit value P1 is calculated in the same manner as in the first embodiment, and at step 1505 correction is performed by the lower limit limiter. This corresponds to the fuel pressure lower limit correction means. As a result, even when the fuel supply amount Ti is small or the rotational speed N is low, the fuel pressure lower limit value P1 does not become extremely low, and the fuel is sufficiently atomized, so that deterioration of combustion and misfire can be prevented.

A third embodiment will be shown. In the first embodiment,
When estimating the estimated fuel pressure value Ppump in FIG. 20, the future estimation was performed based on the previous estimated value, but the previous fuel pressure data uses the actual measurement value by the fuel pressure sensor 10 and estimates the future fuel pressure. Alternatively, a correction coefficient may be calculated from the previous estimated value and the previous measured value to correct the fuel pressure increase characteristic of FIG. 18, and the future estimation may be performed using the correction coefficient.

In this case, as the fuel pressure estimating means D, the routine of FIG. 16 is used instead of the routine of FIG. 13 of the first embodiment. The routine of FIG. 16 is executed for each reference.
In step 1601, the fuel pressure sensor detection value Psen in the previous predetermined period (between references) as shown in FIG. 23 is read, and in the following step 1602, the previously used fuel pressure estimated value Pest corresponding to the sensor detection value Psen is read. In step 1603, the correction coefficient α of the estimated fuel pressure value is calculated from the data read in step 1601 and step 1602. Specifically, the correction coefficient α is obtained by the following equation as the ratio of the respective average values.

Α = Ave (Psen) / Ave (Pest) In step 1604, the fuel pressure Ppump by the high-pressure fuel pump is estimated from the characteristic of FIG. 18 as in the first embodiment, and the step is executed.
In 1605, the estimated value Ppump is corrected by the following equation using the correction coefficient α calculated in step 1603 to obtain P'pump. P′pump = Ppump × α After that, in each step from step 1606 to step 1609, the corrected estimated value P′pump is used to calculate in the same manner as the procedure of FIG. 13 of the first embodiment to supply the fuel. When the fuel pressure value Pdown is decreased, the fuel pressure value Pdown is estimated as shown in FIG. 23, and this routine ends.

As a result, it becomes possible to more accurately estimate how the fuel pressure value changes when fuel is supplied. In this embodiment, in order to calculate the correction coefficient α of the estimated fuel pressure value, the average value Ave (Pest) of the previous estimated fuel pressure value series is calculated.
The average value Ave (Psen) of the sensor output sequence was used, but this may be calculated only from the data at a predetermined crank angle. Although only the data of the previous combustion is used here, the correction coefficient may be obtained using the data of the past several combustions.

The correction based on the sensor output is applied not only to the characteristic Ppump of the fuel pump, but also to the fuel supply time Tpulse.
May be performed for the characteristic of the fuel pressure decrease ratio with respect to (FIG. 19). In this case, the fuel pressure decrease rate when fuel is supplied may be detected from the sensor output, and the correction value β may be set based on this data. As in the first embodiment, this control is executed from the start, and if a predetermined time (for example, (5 s) or a predetermined combustion cycle (for example, 50 combustion cycles) elapses after the first fuel supply is performed. , End execution.

Also in this embodiment, if a lower limit limiter is provided for the fuel pressure lower limit value P1 as in the second embodiment, it is possible to more accurately determine whether the fuel supply or the fuel postponement is postponed. . A fourth embodiment will be described. In the first and second embodiments, when estimating the estimated fuel pressure value of FIG. 21, the fuel pressure increase characteristic Ppump of the fuel pump is the same in all operations (FIG. 18).
However, when the engine is equipped with the fuel temperature sensor 19 that detects the temperature of fuel (hereinafter referred to as the fuel temperature), the difference in the fuel pressure increase characteristics due to the subtle change in the fuel property based on the difference in the fuel temperature has been experimentally tested in advance. By investigating beforehand, it becomes possible to more accurately estimate the fuel pressure increase characteristic of the pump based on the fuel temperature at that time.

In this case, as the fuel pressure estimating means D, the routine of FIG. 24 is used instead of the routine of FIG. 13, and the table of FIG. 25 is used instead of the table of FIG. The routine of FIG. 24 is executed for each reference. After reading the previous estimated fuel pressure value Pest in step 2401, the fuel temperature is read in step 2402, and in step 2403, based on the fuel temperature, the data of FIG. Estimated Fuel Pressure Ppu of High Pressure Fuel Pump
Calculate mp. After that, as in FIG. 13, steps 2404 to
The 2407 estimates the reduced fuel pressure value (Pdown) during fuel supply.

Here, in the case where the fuel pressure sensor 10 is used as shown in the third embodiment, the difference in the fuel pressure increase characteristic of the fuel pump due to the difference in the fuel temperature is also based on the detected value of the fuel pressure sensor 10. It is not necessary to use FIG. 24 and FIG. 25 because they are considered to have been corrected. In each of the embodiments described above,
The engine 1 has four cylinders, and the fuel pump discharges fuel four times for every two revolutions of the engine. However, the fuel discharge cycle of the fuel pump is not limited to this, and the characteristic of the fuel pressure with respect to the crank angle is known. If so, the period does not necessarily have to be the same as the engine rotation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIG. 2 is a system configuration diagram showing an engine portion of an embodiment of the present invention.

FIG. 3 is a system configuration diagram showing a circuit portion of an embodiment of the present invention.

FIG. 4 is a diagram showing opening and closing timings of an intake valve and an exhaust valve.

FIG. 5 is a diagram showing the relationship between the fuel pressure and the fuel supply time when the fuel supply amount is constant.

FIG. 6 is a diagram showing a process of increasing fuel pressure by a fuel pump.

FIG. 7 is a diagram showing changes in fuel pressure and rotational speed when the fuel supply amount at start is small.

FIG. 8 is a diagram showing changes in fuel pressure and rotation speed when a large amount of fuel is supplied at startup.

FIG. 9 is a diagram showing changes in fuel pressure and rotation speed when the method of the present invention is applied, when the fuel supply amount at startup is large.

FIG. 10 is a flowchart showing a procedure for detecting an operating state.

FIG. 11 is a flowchart showing a procedure for calculating a fuel supply amount.

FIG. 12 is a flowchart showing a procedure for calculating the lower limit value of the fuel pressure.

FIG. 13 is a flowchart showing a procedure for estimating fuel pressure.

FIG. 14 is a flowchart showing a procedure for determining whether to supply fuel.

FIG. 15 is a flowchart showing a second procedure for calculating the lower limit value of the fuel pressure.

FIG. 16 is a flowchart showing a second procedure for estimating the fuel pressure.

FIG. 17 is a diagram showing the relationship between the water temperature at startup and the fuel supply amount.

FIG. 18 is a diagram showing a characteristic of fuel pressure increase by a fuel pump with respect to a crank angle.

FIG. 19 is a diagram showing a relationship between a fuel injection pulse width and a fuel pressure decrease width.

[Fig. 20] Fig. 20 is a diagram showing how the fuel pressure is estimated by the fuel pump.

FIG. 21 is a diagram showing how the fuel pressure change is estimated in consideration of both the fuel pressure change due to the fuel pump and the fuel pressure decrease due to the fuel supply.

FIG. 22 is a diagram illustrating an example of a lower limit limiter map.

FIG. 23 is a diagram showing how fuel pressure change is estimated in consideration of both the fuel pressure change due to the fuel pump and the fuel pressure decrease due to fuel supply when the fuel pressure sensor is provided.

FIG. 24 is a flowchart showing a third procedure for estimating fuel pressure.

[Fig. 25] For the crank angle when the fuel temperature is different,
Diagram showing the characteristics of fuel pressure increase by fuel pump

[Explanation of symbols]

 1 Engine 2 Throttle Valve 3 Surge Tank 4 Intake Manifold 5 Intake Valve 6 Direct Injection Injector 7 Combustion Chamber 8 Spark Plug 9 Air Flow Meter 10 Fuel Pressure Sensor 19 Fuel Temperature Sensor

Claims (10)

[Claims] 1. A control device for a direct injection type internal combustion engine, in which fuel is directly injected into a cylinder at a high pressure by a direct injection injector, and an operating condition detecting means for detecting an operating condition of the engine; A fuel supply amount calculation means for calculating a fuel supply amount, and a fuel pressure lower limit for calculating a lower limit value of the fuel pressure required at the time of start based on the detection result of the operating state detection means and the calculation result of the fuel supply amount calculation means. Value calculation means, fuel pressure estimation means for estimating a change in fuel pressure when fuel is supplied based on the detection result of the operating state detection means and the calculation result of the fuel supply amount calculation means, and the fuel pressure lower limit value Fuel supply start cylinder determination means for determining a cylinder to start fuel supply at the time of starting based on the calculation result of the calculation means and the estimation result of the fuel pressure estimation means. Control devices that direct injection internal combustion engine. 2. The operating state detecting means detects a crank angle of the engine by a crank angle sensor installed in the internal combustion engine, and calculates an engine speed based on the detected crank angle. The control device for a direct injection type internal combustion engine according to claim 1, wherein: 3. The fuel supply amount calculation means determines the fuel supply amount at the time of starting the engine from a predetermined table based on the temperature of the cooling water of the engine.
Alternatively, the control device for the in-cylinder direct injection internal combustion engine according to claim 2. 4. The fuel pressure lower limit value calculating means, a crank angle section in which fuel can be supplied, and a maximum fuel supply time calculated based on an engine speed detected by the operating state detecting means, From the fuel supply amount calculated by the fuel supply amount calculation means, a lower limit value of the fuel pressure required to finish supplying the fuel supply amount within the maximum time is calculated from a predetermined table. The control device for a cylinder direct injection internal combustion engine according to any one of claims 1 to 3. 5. The fuel pressure lower limit value calculating means is provided with a limiter for limiting the minimum value of the fuel pressure lower limit value, and is configured to include a fuel pressure lower limit value correcting means for correcting the calculated lower limit value of the fuel pressure. The control device for a direct injection internal combustion engine according to claim 4, wherein. 6. The fuel pressure estimating means, based on a crank angle detected by the operating state detecting means, a fuel supply amount calculated by the fuel supply amount calculating means, and a predetermined fuel pump characteristic,
The control device for a direct injection internal combustion engine, according to any one of claims 1 to 5, which estimates a change in fuel pressure after fuel supply. 7. The internal combustion engine comprises a fuel pressure sensor for detecting fuel pressure, while the fuel pressure estimating means calculates a crank angle detected by the operating state detecting means and a fuel supply amount calculated by the fuel supply amount calculating means. The in-cylinder direct according to any one of claims 1 to 5, wherein a change in fuel pressure is estimated from a known characteristic of a fuel pump and an output of the fuel pressure sensor. Control device for internal combustion engine. 8. The internal combustion engine includes a fuel temperature sensor for detecting a fuel temperature, while the fuel pressure estimating means calculates a crank angle detected by the operating state detecting means and a fuel supply calculated by the fuel supply amount calculating means. The cylinder according to any one of claims 1 to 5, wherein a change in fuel pressure is estimated from an amount, a known characteristic of a fuel pump, and an output of the fuel temperature sensor. Control device for internal direct injection internal combustion engine. 9. The fuel supply start cylinder determination means compares the estimated value of the fuel pressure after the fuel supply calculated by the fuel pressure estimation means with the fuel pressure lower limit value calculated by the fuel pressure lower limit value calculation means. However, if the estimated fuel pressure is equal to or higher than the lower limit of fuel pressure, fuel is supplied to the cylinder whose fuel supply timing is approaching, and if the estimated fuel pressure is smaller than the lower limit of fuel pressure, fuel is supplied. First, the same process is performed at the next fuel supply timing to determine the cylinder to start the fuel supply.
The control device for a direct injection type internal combustion engine, according to claim 8. 10. The control device for a direct injection type internal combustion engine, according to claim 1, characterized in that the control is terminated when a predetermined period has elapsed after the engine was started. .