JP2010261335A - Control device of cylinder injection type engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of a cylinder injection type engine capable of restraining the deterioration in exhaust performance by an increase in fuel pressure in a common rail by receiving heat from an engine, while securing responsiveness in restarting thereafter, when performing an idle stop, when the engine is put in a high temperature state. <P>SOLUTION: When an operation state of the engine and an engine-mounted vehicle satisfies a predetermined condition, the idle stop is performed for temporarily stopping the engine, and allowable fuel pressure of fuel supplied to a fuel injection valve is determined when restarting after the idle stop based on a characteristic of the fuel injection valve, and pressure of the fuel is controlled so as not to exceed the restarting time allowable fuel pressure in the idle stop. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an engine control device mounted on a vehicle or the like, and in particular, performs an idle stop that temporarily stops the engine when the engine and the operating state of the engine-equipped vehicle satisfy a predetermined condition. The present invention relates to a control device for an in-cylinder injection engine.

  Current vehicles (automobiles) reduce exhaust gas substances such as carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) contained in automobile exhaust gases from the viewpoint of environmental conservation, and fuel consumption Reduction of the amount is demanded, and for the purpose of these reductions, for example, as shown in the following Patent Document 1 and the like, the development of an in-cylinder injection engine has been performed. The in-cylinder injection engine directly performs fuel injection by a fuel injection valve into a combustion chamber of a cylinder, and aims to reduce exhaust gas substances, reduce fuel consumption, improve engine output, and the like.

  Here, in order to reduce the particle size of the fuel injected from the fuel injection valve, means for increasing the pressure of the fuel is required, and various techniques for a high-pressure fuel supply device have been proposed. Among them, for example, in Patent Document 2 below, there is a technology in which an electronically controlled relief valve is provided in a common rail that stores fuel to be supplied to the fuel injection valve, and the fuel pressure in the common rail is controlled using this relief valve. It is disclosed.

  In addition to the above, in order to improve fuel consumption, intermittent operation control that automatically stops the engine temporarily during establishment of a predetermined condition after vehicle operation is started, so-called idle stop is performed, for example, 3 etc.

  When performing the idling stop, the responsiveness when starting the engine again is important. In Patent Literature 4 below, in the in-cylinder injection engine, it is necessary for restarting when performing the idling stop. In order to suppress the deterioration of responsiveness caused by increasing the fuel pressure up to the fuel pressure, the electronically controlled relief valve is kept closed during idling stop (when the engine is stopped) to ensure fuel pressure at restart Techniques to do this are disclosed.

JP 2007-23930 A JP 2005-98138 A JP 2000-352462 A JP 2006-258032 A

  In the vehicle that performs the idling stop, particularly when the idling stop is performed in a state where the engine (main body) is at a high temperature, the heat generated from the engine before the idling stop is performed on the common rail in the engine room. Accordingly, the fuel temperature in the common rail rises, and the fuel pressure in the common rail rises due to the bulk modulus of the fuel.

  On the other hand, the fuel injection valve has a characteristic that the fuel injection amount (hereinafter, abbreviated as the injection amount) increases as the fuel pressure increases under the same drive pulse width. With respect to the injection amount characteristic, the linearity is maintained in a region where the drive pulse width is a certain value or more, and the injection amount is not stable when the drive pulse width is less than a certain value. Therefore, the lower limit value that can be used as the drive pulse width is limited to a minimum value that maintains linearity.

  Accordingly, when the fuel temperature in the common rail rises due to heat received from the engine and the fuel pressure in the common rail rises due to the bulk modulus of fuel, the drive pulse width of the fuel injection valve is temporarily set to the minimum value. Even if the actual injection amount becomes larger than the desired injection amount (target injection amount) and the air-fuel ratio becomes excessively rich, the exhaust performance deteriorates, and the oil due to the increase in fuel adhesion to the engine cylinder or the like. There is a risk of overdilution. In order to avoid such problems, if the drive pulse width of the fuel injection valve is set to a value equal to or smaller than the minimum value, the linearity of the fuel injection amount with respect to the drive pulse width is not maintained and the injection amount is not stable. There is a risk of deteriorating exhaust performance.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to perform a restart after an idle stop even when an idle stop is executed while the engine is at a high temperature. An object of the present invention is to provide a control device for a direct injection engine that can suppress deterioration of exhaust performance due to increase in fuel pressure in a common rail due to heat received from the engine while ensuring responsiveness.

  In order to achieve the above object, the control device for a direct injection engine according to the present invention basically stops the engine temporarily when the operating condition of the engine and the engine-equipped vehicle satisfies a predetermined condition. Based on the characteristics of the fuel injection valve, an allowable fuel pressure of fuel supplied to the fuel injection valve at the time of restart after the idle stop is obtained, and during the idle stop, The pressure is controlled so as not to exceed the allowable fuel pressure at the time of restart.

  In a more specific preferred embodiment, a fuel injection valve that directly injects fuel into the combustion chamber of the engine, a fuel pump that discharges the sucked fuel to the fuel injection valve side, and fuel that is supplied to the fuel injection valve is stored. A common rail, a pressure sensor for detecting a fuel pressure in the common rail, and an electric relief valve for reducing the fuel pressure in the common rail. When the vehicle and the engine satisfy a predetermined condition, the engine is temporarily The engine is stopped at an idle stop, and based on the engine coolant temperature or the like, the required fuel injection amount at restart required for restart after the idle stop is calculated, and the characteristics of the fuel injection valve and Based on the required fuel injection amount at restart, the allowable fuel pressure at restart is calculated, and during idling stop, If the charge pressure exceeds the restart time allowable fuel pressure, it is characterized in that for opening the electrically controlled relief valve.

  In this case, in a preferred aspect, the allowable fuel pressure at restart is based on the minimum value of the drive pulse width that can maintain linearity with respect to the fuel injection amount, and the relationship between the fuel pressure in the common rail and the fuel injection amount. To be calculated.

  In another preferred aspect, when the engine and the operating state of the engine-equipped vehicle satisfy a predetermined condition, the engine is temporarily stopped to stop the engine, and the fuel is restarted after the idle stop is restarted. When the drive pulse width to be supplied to the injection valve is set to a minimum value that can maintain linearity with respect to the fuel injection amount, the actual injection amount of the fuel injection valve at the time of restart is required at the time of restart. The fuel pressure of the fuel supply system is controlled during idle stop so as not to exceed the fuel injection amount.

  According to the present invention, during idle stop, in preparation for the subsequent restart, the electric relief valve is controlled to be opened and closed, and the fuel pressure in the common rail is made equal to or less than the allowable fuel pressure at restart. While ensuring responsiveness during restart after idle stop, deterioration of exhaust performance due to increase in fuel pressure in the common rail due to heat received from the engine, oil overdilution due to increased fuel adhesion to the engine cylinder, etc. It can be effectively suppressed.

1 is a schematic configuration diagram of a vehicle equipped with a vehicle engine control device according to an embodiment of the present invention. 1 is a schematic configuration diagram of an entire control system for a direct injection engine according to an embodiment of the present invention. 1 is an overall configuration schematic diagram of a fuel system including a high-pressure fuel pump according to an embodiment of the present invention. The block diagram which shows the input / output signal relationship of the engine control unit used with the system configuration | structure which shows one Embodiment of the control apparatus of the engine for vehicles by one Embodiment of this invention. The flowchart which shows the control content of the engine pressure control during engine idle stop by one Embodiment of this invention. The function table of the required injection amount at restart for calculating the allowable fuel pressure at restart shown in FIG. 5 and the characteristics of the drive pulse width of the fuel injection valve for setting the function table, the fuel pressure, and the fuel injection amount FIG. The time chart which shows the example of control at the time of performing idle stop, without using the fuel pressure control during engine idle stop by one embodiment of this invention. The time chart which shows the 1st control example at the time of performing an idle stop using the fuel pressure control during the engine idle stop by one embodiment of this invention. The time chart which shows the 2nd control example at the time of performing idle stop using the engine fuel pressure control during engine idle stop by one embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of a control device according to the present invention together with a vehicle on which a direct injection engine to which the control device is applied is mounted.

  The illustrated vehicle 10 includes an in-cylinder injection engine 1, a ring gear 1a connected to the engine 1, a transmission 3 connected to the ring gear 1a, a differential gear 4 connected to the transmission 3, a differential. Drive wheels 5a and 5b connected to the gear 4 are provided (two wheels which are not drive wheels are four-wheeled vehicles although illustration is omitted), and the ring gear 1a is connected to the pinion gear 2a. A starter 2 to be connected is provided. The battery 104 includes a rechargeable secondary battery. The battery 104 is generally a lead storage battery, but can be constructed using a nickel metal hydride battery or a lithium ion battery.

  In addition, the vehicle 10 is configured to be able to execute intermittent operation control, that is, so-called idle stop control in which the engine 1 is automatically stopped temporarily while a predetermined condition is satisfied after the operation is started. That is, the vehicle 10 is provided with an engine control unit 101 that controls the engine 1, a starter control unit 102 that controls the starter 2, and a transmission control unit 103 that controls the transmission 3. A DC voltage is supplied from the battery 104 to the units 101, 102, and 103. The engine control unit 101 and the transmission control unit 103 transmit and receive information via communication means. The starter control unit 102 receives an operation signal of a key switch (not shown) by the driver and a start signal from the engine control unit 101, controls the starter 2, and drives the engine 1 to start rotation. Give power.

  The starter 2 and the pinion gear 2a may be of a sliding type in which the pinion gear 2a is slid and meshed with the ring gear 1a, but a constant meshing type in which the pinion gear 2a and the ring gear 1a are always meshed. Alternatively, the motor generator may be connected via a belt, or it may be configured by using another mechanism for starting the engine 1 again after it is stopped. In addition to the engine 1, the driving force source may be a so-called hybrid vehicle provided with one or more motor generators, and the engine 1 may be started by the motor generator. Moreover, when restarting the engine 1, it is good also as a starting device starting system which starts by injecting fuel, rotating an engine by the said starting device, and stop of the piston of the engine 1 when the engine 1 stops Even if a so-called combustion start method is employed, the fuel is injected and ignited at an optimal time (crank angle) for controlling the position and restarting the engine 1, and the engine 1 is restarted by the torque generated by combustion. Alternatively, a method using both a starter start method and a combustion start method may be used.

  In the present embodiment, the engine control unit 101 and the starter control unit 102 are configured separately, but may be configured integrally. In the present embodiment, the transmission 3 is configured as an automatic transmission including the transmission control unit 103. However, the transmission 3 may be configured as a manual transmission. The stepped transmission used, the continuously variable transmission using a belt and a pulley, or a so-called twin clutch transmission can be used.

  FIG. 2 is a schematic configuration diagram of the entire control system of the engine 1. The in-cylinder injection engine 1 in the illustrated example includes, for example, four cylinders (# 1, # 2, # 3, # 4), and air supplied into each cylinder 207b is taken in from an inlet portion of an air cleaner 202, The air passes through an air flow meter (air flow sensor) 203 and enters a collector 206 through a throttle body 205 in which an electric throttle 205a for controlling the amount of intake air is accommodated. The air sucked into the collector 206 is distributed to each intake pipe 201 (intake manifold and intake port) connected to each cylinder 207b of the engine 1, and then slidably inserted into each cylinder 207b. It is guided to a combustion chamber 207c defined above the piston 207a. Further, a signal representing the intake air amount is supplied from the airflow sensor 203 to the engine control unit 101. Furthermore, a throttle sensor 204 for detecting the opening degree of the electric throttle 205a is attached to the throttle body 205, and its signal is also output to the engine control unit 101.

  On the other hand, the fuel supply system for supplying fuel to the fuel injection valve 254 has the following configuration. That is, fuel such as gasoline is primarily pressurized from the fuel tank 250 by the low-pressure fuel pump 251 and regulated to a constant pressure (for example, 0.3 MPa) by the fuel pressure regulator 252, and moreover by the high-pressure fuel pump 209 described later. Secondary pressure is applied to a high pressure (for example, 5 MPa or 10 MPa), and the fuel is injected into the combustion chamber 207 c from the fuel injection valve 254 provided in each cylinder 207 b via the common rail 253. The fuel injected into the combustion chamber 207 c is ignited by a spark emitted from a spark plug 208 to which a high voltage is applied from the ignition coil 222. In this embodiment, the fuel injection valve 254 is a center injection method in which the fuel injection valve 254 is injected from directly above the combustion chamber 207c, but may be a side injection method in which the fuel injection valve 254 is injected from the side of the combustion chamber 207c.

  A crank angle sensor 216 attached to the crankshaft 207d of the engine 1 outputs an angle signal indicating the rotational position of the crankshaft 207d to the engine control unit 101. The engine 1 also includes a variable valve mechanism that can change the opening and closing timings of the intake valve 225 and the exhaust valve 226. The cam angle sensor 211 attached to the exhaust camshaft is a rotational position of the camshaft. Is output to the engine control unit 101, and an angle signal indicating the rotational position of the high-pressure fuel pump drive cam 200 that rotates as the cam shaft on the exhaust side rotates is also output to the engine control unit 101.

  In the present embodiment, a four-cylinder in-cylinder injection engine 1 is described as an example, but an engine having another number of cylinders such as three or six cylinders may be used.

  In addition, the engine 1 of the present embodiment is configured to include a variable valve mechanism that can change the opening and closing timings of both the intake valve 225 and the exhaust valve 226. However, as the variable valve mechanism, the opening and closing timing of the intake valve 225 may be used. It is good also as a structure which can be changed only, and it is good also as a structure provided with the variable valve mechanism which can change the valve lift amount in addition to the opening / closing timing.

FIG. 3 shows an overall schematic configuration of a fuel system provided with the high-pressure fuel pump 209.
The high-pressure fuel pump 209 pressurizes fuel from the fuel tank 250 and pumps high-pressure fuel to the common rail 253.

  The fuel in the tank 250 is sucked and discharged by the low-pressure pump 251, and is led to the fuel inlet of the high-pressure fuel pump 209 while being regulated to a constant pressure by the pressure regulator 252. A high-pressure pump solenoid 209a that is an electromagnetic control valve for adjusting the fuel introduction amount is provided on the fuel introduction port side. The high-pressure pump solenoid 209a is a normally closed solenoid that closes when not energized and opens when energized. The fuel supplied by the low-pressure pump 251 is adjusted in suction amount by controlling the high-pressure pump solenoid 209a by the engine control unit 101, and pressurized in the pressurizing chamber 209b having a piston driven by the pump drive cam 200. Then, it is pumped from the fuel discharge port to the common rail 253. The fuel discharge port is provided with a discharge valve (check valve) 209c so that the downstream high-pressure fuel does not flow back into the pressurizing chamber.

  The common rail 253 is provided with a pressure sensor 256 and a normally closed type electronically controlled relief valve (hereinafter referred to as an electric control relief valve) 255 that is opened when the fuel pressure in the common rail 253 is reduced. ing. The electric relief valve 255 is provided to prevent damage to the high-pressure piping system and to reduce the fuel pressure in the common rail 253 as necessary. The fuel pressure in the common rail 253 exceeds a predetermined value. And when the electric drive signal is given by the engine control unit 101, the valve is opened.

  FIG. 4 shows the input / output relationship of the engine control unit 101. The engine control unit 101 includes an I / O LSI 101a including an A / D converter, a CPU 101b, and the like. The key switch 401 signal indicating an accessory, ignition ON, and starter ON, an accelerator opening sensor 402, a brake switch 403, and a vehicle speed sensor 404, an airflow sensor 203, a throttle sensor 204, a cam angle sensor 211, a crank angle sensor 216, a water temperature sensor 217, an air-fuel ratio sensor 218, a signal from various sensors including a fuel pressure sensor 256, and the like are input as inputs to perform predetermined calculation processing. This is executed, and various control signals calculated as calculation results are output, and the electric throttle 205a, the high pressure pump solenoid 209a, the ignition coil 222, the low pressure fuel pump 251, and the cylinders (# 1, # 2, # 3) that are actuators are output. , # 4) Fuel injection 254, it supplies a predetermined control signal 255 such as an electrically controlled relief valve, a common rail internal combustion pressure control, and executes the injection amount control and ignition timing control. The electric relief valve 255 is controlled by the engine control unit 101 as a so-called PWM drive in which a duty ratio for a predetermined drive cycle is set.

  The signal of the vehicle speed sensor 404 may be input from the transmission control unit 103 of FIG. 1 via communication means, and further, the shift lever position (P range, R range) is transmitted from the transmission control unit 103. , N range, D range, and M range that allows the driver to perform a shifting operation) may be input.

Next, the fuel pressure control of the present embodiment will be specifically described with reference to FIGS.
FIG. 5 is a flowchart showing an example of a fuel pressure control routine including fuel pressure control during idle stop.
This fuel pressure control routine is programmed in the CPU 101b of the engine control unit 101 and is repeatedly executed at a predetermined cycle. That is, the processing of the following steps 501 to 506 is repeatedly executed at a predetermined cycle by the engine control unit 101.

  First, in step 501, signals from the vehicle speed sensor 404, the accelerator opening sensor 402, the crank angle sensor 216, the water temperature sensor 217, the brake switch 403, etc. are taken in, and the vehicle speed, accelerator opening, engine speed, engine cooling used for control are taken. Calculate parameters such as water temperature.

  Subsequently, in step 502, it is determined whether or not the engine is idling based on parameters such as the vehicle speed, accelerator opening, engine speed, and engine coolant temperature calculated in step 501. The idle stop is a function that automatically stops the engine 1 temporarily when a predetermined condition is satisfied after the vehicle starts driving. For example, the vehicle speed is 0, the accelerator opening is 0, the idle state is continued for a certain time, and the brake pedal is The engine is automatically stopped when a condition such as being depressed is satisfied. Accordingly, in step 502, it is determined whether or not the above condition is satisfied and the engine is stopped. If NO, the engine is not idling stopped, and therefore the process proceeds to step 506, where, for example, the engine speed, the engine load ( The required target fuel pressure is calculated according to the intake air amount, engine cooling water temperature, etc., and the high pressure fuel pump 209 and the electric relief valve 255 are controlled so that the actual fuel pressure becomes the target fuel pressure (normal fuel pressure control). Finish this flow.

  In this example, various signal acquisitions in step 501, parameter calculation, and idling stop determination processing in step 502 are performed in the fuel pressure control routine of the engine control unit 101. It may be performed by another routine of the unit 101 (for example, a fuel injection control routine or the like), or may be performed by another control unit such as the engine starter control unit 102.

  If it is determined in step 502 that the engine is idling stop, the process proceeds to step 503, and a fuel injection amount (required injection amount at restart) necessary for restarting the engine 1 after the idling stop is calculated. In calculating the required injection amount TTf_rst at the time of restart, for example, the basic injection amount is set according to the engine coolant temperature, and the oxygen inhalation amount in the process of stopping the engine 1 (idle stop) is considered. It is desirable to calculate a typical target injection amount.

  In the subsequent step 504, the restart allowable fuel pressure TPf_rst is obtained based on the restart required injection amount TTf_rst. This restart allowable fuel pressure TPf_rst is set so as not to exceed the restart required injection amount TTf_rst when the drive pulse width supplied to the fuel injection valve 254 is the minimum drive pulse width. 6 is a function (f1) represented by a curve as shown in FIG. 6A with the fuel pressure on the vertical axis and the fuel injection amount on the horizontal axis. The restart allowable fuel pressure TPf_rst is a memory map of the CPU 101b. Stored as a table function.

  A curve (function f1) representing the restart allowable fuel pressure TPf_rst with respect to the restart required injection amount TTf_rst is a drive pulse width, fuel pressure, and fuel injection amount of the fuel injection valve 254 as shown in FIG. It is required from the relationship. Here, the minimum drive pulse width that can be used as the pulse width of the drive pulse signal supplied to the fuel injection valve 254 depends on the characteristics (individual differences) of the fuel injection valve 254, and in general, the drive pulse width and the fuel injection It is defined as the minimum value of the drive pulse width in a range where linearity is maintained in relation to the quantity. Strictly speaking, the minimum drive pulse width changes according to the fuel pressure, and generally the minimum drive pulse width tends to slightly increase as the fuel pressure increases, but depends on the characteristics (individual differences) of the fuel injection valve 254. It is desirable that the restartable fuel pressure TPf_rst is set in accordance with the characteristics of the fuel injection valve 254 being used. In this embodiment, the restartable allowable fuel pressure TPf_rst is stored as a table function in the memory map of the CPU 101b, but may be calculated by calculation.

  In the next step 505, the allowable fuel pressure TPf_rst at the time of restart is compared with the fuel pressure in the common rail 253 detected by the fuel pressure sensor 256 (hereinafter referred to as detected fuel pressure SPf). Open / close control of the relief valve 255 is performed. That is, when the detected fuel pressure SPf is larger than the restart allowable fuel pressure TPf_rst, the electronic control valve 255 is opened for a predetermined time, and the detected fuel pressure SPf is equal to or less than the restart allowable fuel pressure TPf_rst-α (α is the width of the dead zone). If it is, the electric control relief valve 255 is kept closed. In the case of TPf_rst−α <SPf ≦ TPf_rst, the electronic control relief valve 255 is made to maintain the previous state. The electric control relief valve 255 is controlled by PWM drive at a predetermined cycle by the engine control unit 101 based on the comparison result of step 505. The opening time of the electric control relief valve 255 is set to a constant value obtained by an experiment or the like in advance, or the temperature of the engine 1 (cooling water temperature), the detected fuel pressure SPf, the change rate of the detected fuel pressure SPf at the time of idling stop, and the like. You may make it change according to it. Note that the dead zone width α is sufficient in consideration of margins for avoiding dizzying hunting and for the allowable fuel pressure at restart TPf_rst and the minimum fuel pressure (for example, 2 MPa or 3 MPa) defined as the operating range. It is desirable to set so that a margin can be secured.

Next, with reference to FIG. 7 to FIG. 9, the operation and effect when the fuel pressure control routine as shown in FIG. 5 is executed will be described in comparison with the conventional example.
FIG. 7 is a time chart showing changes in engine speed and fuel pressure when the fuel pressure control as shown in FIG. 5 is not performed (prior art example) during idling stop with the engine 1 at a high temperature.

  In FIG. 7, (A) shows the state of a flag for determining whether or not the engine is idling stop (if “1”, idling stop), (B) is the engine speed, (C) is the fuel pressure, (D) Indicates whether the electric relief valve 255 is open or closed (controlled).

  Before time t1, the engine 1 is in an operating state, the idle stop flag in (A) is “0”, the engine speed in (B) is 0 or more, and the fuel pressure in (C) is kept at a predetermined value, The electric relief valve 255 in (D) is in a closed state.

  When the idle stop execution condition is satisfied at time t1 and the idle stop flag changes from “0” to “1”, ignition by the spark plug 208 and fuel injection supply by the fuel injection valve 254 are stopped, and the engine speed is 0. (Engine 1 is stopped). For this reason, the fuel amount in the common rail 253 does not decrease from the idle stop start time t1 to the idle stop end time t3. However, since the temperature of the engine 1 is high, the common rail 253 receives heat from the surroundings to receive the common rail 253. The internal fuel temperature rises, and the actual fuel pressure (detected fuel pressure SPf) in the common rail 253 rises due to the bulk modulus of the fuel. Therefore, the detected fuel pressure SPf in the common rail 253 exceeds the restart-time allowable fuel pressure TPf_rst at time t2.

  When an idle stop release condition (for example, a condition determined from the opening and position of a brake pedal, an accelerator pedal, a shift lever, etc.) is established at time t3 and the idle stop flag is returned from “1” to “0”, the engine In order to restart the engine 1, a rotational driving force is applied to the engine 1 by the starter 2, ignition by the spark plug 208 and fuel injection by the fuel injection valve 254 are resumed, and air sucked into the combustion chamber 207 c and fuel injection An air-fuel mixture comprising fuel injected from the valve 254 is ignited by spark discharge of the spark plug 208, and the engine speed increases due to combustion of the air-fuel mixture.

  At the time t3, the detected fuel pressure SPf is higher than the restartable allowable fuel pressure TPf_rst. Therefore, even if the drive pulse signal having the minimum drive pulse width is supplied to the fuel injector 254, the fuel injector 254 results in excess. As a result, fuel is injected into the air-fuel ratio, resulting in deterioration of exhaust performance due to excessively rich air-fuel ratio and excessive dilution of oil due to increased fuel adhesion to a cylinder or the like.

  FIG. 8 is a time chart showing an example of changes in the engine speed and the fuel pressure when the fuel pressure control as shown in FIG. 5 is performed during idle stop with the engine 1 at a high temperature (present invention 1). It is.

  8 (A), (B), (C), and (D) are the same as (A), (B), (C), and (D) in FIG. (B) is the engine speed, (C) is the fuel pressure, and (D) is the state where the electric relief valve 255 is open / closed. (It is controlled). .

  Prior to time t1, as in the conventional example, the engine 1 is in an operating state, the idle stop flag in (A) is “0”, the engine speed in (B) is 0 or more, and the fuel pressure in (C) is predetermined. The electric relief valve 255 of (D) is in the closed state.

  When the idle stop execution condition is satisfied at time t1 and the idle stop flag changes from “0” to “1”, ignition by the spark plug 208 and fuel injection supply by the fuel injection valve 254 are stopped, and the engine speed is 0. (Engine 1 is stopped). For this reason, the fuel amount in the common rail 253 does not decrease from the idle stop start time t1 to the idle stop end time t3. However, since the temperature of the engine 1 is high, the common rail 253 receives heat from the surroundings to receive the common rail 253. The internal fuel temperature rises, and the actual fuel pressure (detected fuel pressure SPf) in the common rail 253 rises due to the bulk modulus of the fuel.

  When the detected fuel pressure SPf exceeds the restartable allowable fuel pressure TPf_rst at time t2, the electric relief valve 255 is opened for a predetermined time (step 505 in FIG. 5), and thereby the detected fuel pressure SPf is lowered. When the detected fuel pressure SPf falls below the restartable allowable fuel pressure TPf_rst-α, the electric control relief valve 255 is closed, and thus the fuel pressure in the common rail 253 increases again from the time point t2 to the time point t2 '. When the detected fuel pressure SPf exceeds the restartable allowable fuel pressure TPf_rst at the time t2 ', the electric control relief valve 255 is opened again for a predetermined time, and the detected fuel pressure SPf decreases.

  When the idle stop release condition is satisfied at time t3 and the idle stop flag is returned from “1” to “0”, a rotational driving force is applied to the engine 1 by the starter 2 in order to restart the engine 1, Ignition by the spark plug 208 and fuel injection by the fuel injection valve 254 are resumed, and an air-fuel mixture composed of air sucked into the combustion chamber 207c and fuel injected from the fuel injection valve 254 is ignited by spark discharge of the spark plug 208. The engine speed increases due to the combustion of the air-fuel mixture.

  At the time point t3, the detected fuel pressure SPf is kept below the restartable allowable fuel pressure TPf_rst, so that at the time of restart, the drive pulse width supplied to the fuel injection valve 254 can be greater than or equal to the minimum drive pulse width. . In other words, when restarting after idling stop, the actual fuel pressure (detected fuel pressure SPf) is kept below the allowable fuel pressure TPf_rst during restarting by the opening / closing control of the electric relief valve 255 during idling stop. As the drive pulse width supplied to the fuel injection valve 254, a pulse width in a range in which linearity is maintained with respect to the fuel injection amount (more than the minimum drive pulse width) can be used.

  For this reason, even when idling is stopped while the engine is at a high temperature, the exhaust performance deteriorates due to the air-fuel ratio becoming excessively rich, and the oil due to increased fuel adhesion to the cylinder of the engine 1 etc. Effectively suppresses deterioration of exhaust performance due to increased fuel pressure in the common rail due to heat received from the engine, while ensuring responsiveness at restart after idling stop without causing excessive dilution, etc. Can do.

  FIG. 9 shows another example of changes in engine speed and fuel pressure when fuel pressure control is performed as shown in FIG. 5 (invention 2) during idling stop when the temperature of the engine 1 is high. It is a time chart.

  9 (A), (B), (C), and (D) are the same as (A), (B), (C), and (D) in FIG. (B) is the engine speed, (C) is the fuel pressure, and (D) is the state where the electric relief valve 255 is open / closed. (It is controlled). .

  Prior to time t1, as in the conventional example, the engine 1 is in an operating state, the idle stop flag in (A) is “0”, the engine speed in (B) is 0 or more, and the fuel pressure in (C) is predetermined. The electric relief valve 255 of (D) is in the closed state.

  When the idle stop execution condition is satisfied at time t1 and the idle stop flag changes from “0” to “1”, ignition by the spark plug 208 and fuel injection supply by the fuel injection valve 254 are stopped, and the engine speed is 0. (Engine 1 is stopped).

  In this example, since the fuel pressure in the common rail 253 exceeds the restartable allowable fuel pressure TPf_rst at the time t1, the electric control relief valve 255 is opened for a predetermined time, and the detected fuel pressure decreases. When the fuel pressure decreases, the electric control relief valve 255 is closed. Since the temperature of the engine 1 is high, the fuel temperature in the common rail 253 increases due to the common rail 253 receiving heat from the surroundings until time t2, and the fuel pressure in the common rail 253 increases due to the bulk modulus of the fuel. When the fuel pressure in the common rail 253 exceeds the restart-time allowable fuel pressure TPf_rst at time t2, the electric control relief valve 255 is opened again, and the detected fuel pressure is reduced. When the fuel pressure decreases, the electric control relief valve 255 is closed again. Thereafter, the fuel pressure in the common rail 253 increases again until time t2 '. When the fuel pressure in the common rail 253 exceeds the restart allowable fuel pressure TPf_rst at time t2 ', the electric control relief valve 255 is opened again, and the fuel pressure is reduced.

  When the idle stop release condition is satisfied at time t3 and the idle stop flag is returned from “1” to “0”, a rotational driving force is applied to the engine 1 by the starter 2 in order to restart the engine 1, Ignition by the spark plug 208 and fuel injection by the fuel injection valve 254 are resumed, and an air-fuel mixture composed of air sucked into the combustion chamber 207c and fuel injected from the fuel injection valve 254 is ignited by spark discharge of the spark plug 208. The engine speed increases due to the combustion of the air-fuel mixture.

  At the time point t3, the detected fuel pressure SPf is kept below the restartable allowable fuel pressure TPf_rst, so that at the time of restart, the drive pulse width supplied to the fuel injection valve 254 can be greater than or equal to the minimum drive pulse width. . In other words, when restarting after idling stop, the actual fuel pressure (detected fuel pressure SPf) is kept below the allowable fuel pressure TPf_rst during restarting by the opening / closing control of the electric relief valve 255 during idling stop. As the drive pulse width supplied to the fuel injection valve 254, a pulse width in a range in which linearity is maintained with respect to the fuel injection amount (more than the minimum drive pulse width) can be used.

  For this reason, even when idling is stopped while the engine is at a high temperature, the exhaust performance deteriorates due to the air-fuel ratio becoming excessively rich, and the oil due to increased fuel adhesion to the cylinder of the engine 1 etc. Effectively suppresses deterioration of exhaust performance due to increased fuel pressure in the common rail due to heat received from the engine, while ensuring responsiveness at restart after idling stop without causing excessive dilution, etc. Can do.

DESCRIPTION OF SYMBOLS 1 ... In-cylinder injection type engine 2 ... Starter 3 ... Transmission 101 ... Engine control unit 102 ... Starter control unit 103 ... Transmission control unit 104 ... Battery 200 ... Pump drive cam 203 ... Airflow sensor 204 ... Throttle sensor 208 ... Spark plug 209 ... High pressure fuel pump 211 ... Cam angle sensor 216 ... Crank angle sensor 217 ... Water temperature sensor 218 ... Air-fuel ratio sensor 222 ... Ignition coil 225 ... Intake valve 226 ... Exhaust valve 250 ... Fuel tank 251 ... Low pressure fuel pump 252 ... Fuel pressure Regulator 253 ... Common rail 254 ... Fuel injection valve 255 ... Electrically controlled relief valve 256 ... Fuel pressure sensor 401 ... Key switch 402 ... Accelerator opening sensor 403 ... Brake switch 404 ... Vehicle speed sensor

Claims (4)

When the operating state of the engine and the engine-equipped vehicle satisfies a predetermined condition, a control device for a direct injection engine configured to perform idle stop for temporarily stopping the engine,
Based on the characteristics of the fuel injection valve, an allowable fuel pressure of the fuel supplied to the fuel injection valve at the time of restart after the idle stop is obtained, and during the idle stop, the fuel pressure is determined as the allowable fuel pressure at the time of restart. A control apparatus for a cylinder injection engine, wherein control is performed so as not to exceed. A fuel injection valve for directly injecting fuel into the combustion chamber of the engine, a fuel pump for discharging the sucked fuel to the fuel injection valve side, a common rail for storing fuel to be supplied to the fuel injection valve, and fuel in the common rail A pressure sensor for detecting pressure and an electric relief valve for reducing the fuel pressure in the common rail, and when the vehicle and the engine satisfy a predetermined condition, an idle stop is performed to temporarily stop the engine. An in-cylinder in-cylinder injection engine control device,
Based on the engine coolant temperature and the like, the required fuel injection amount at restart required for restart after the idle stop is calculated, and based on the characteristics of the fuel injection valve and the required fuel injection amount at restart In-cylinder injection, wherein an allowable fuel pressure at restart is calculated, and the electric relief valve is opened when the fuel pressure in the common rail exceeds the allowable fuel pressure at restart during idle stop Type engine control device.   The restart allowable fuel pressure is calculated based on a minimum value of a drive pulse width that can maintain linearity with respect to a fuel injection amount, and a relationship between the fuel pressure in the common rail and the fuel injection amount, The in-cylinder injection engine control device according to claim 2. When the operating state of the engine and the engine-equipped vehicle satisfies a predetermined condition, a control device for a direct injection engine configured to perform idle stop for temporarily stopping the engine,
When the drive pulse width to be supplied to the fuel injection valve at the restart after the idle stop is set to a minimum value that can maintain linearity with respect to the fuel injection amount, the actual performance of the fuel injection valve at the restart is A control apparatus for an in-cylinder injection engine, wherein a fuel pressure of a fuel supply system is controlled during an idle stop so that an injection amount does not exceed a fuel injection amount required at the time of restart.

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