JP4509191B2 - Fuel injection control device for in-cylinder injection engine - Google Patents

Description

  The present invention relates to a fuel injection control device for an in-cylinder injection engine that directly injects high-pressure fuel into a cylinder, and in particular, when vapor is generated in a pressure accumulating chamber, the discharge of vapor in the pressure accumulating chamber and the pressure increase of the fuel are quickly The present invention relates to a fuel injection control device.

  As is well known, in a cylinder injection engine fuel injection control device having a fuel injection valve that directly injects fuel into a combustion chamber, the injected fuel is injected so that the fuel can be injected into the cylinder in a sufficiently fine mist form. Therefore, the fuel discharged from the low-pressure fuel pump is adjusted to a feed pressure set to a predetermined low-pressure value by a low-pressure pressure regulator. The fuel pump is boosted to a desired high pressure value. The high-pressure fuel boosted by the high-pressure fuel pump is stored in the pressure accumulating chamber and directly injected into the combustion chamber of each cylinder of the engine via the fuel injection valve. The pressure accumulating chamber has a volume of a certain level or more, and the pressure drop in the pressure accumulating chamber due to injection is reduced to keep the injection pressure constant.

  The aforementioned high-pressure fuel pump is normally operatively connected to an engine camshaft and is driven at a rotational speed synchronized with the engine. Further, the fuel discharge amount per rotation of the high-pressure fuel pump is considerably smaller than the volume of the pressure accumulating chamber. Therefore, when the engine speed is low, such as when the engine is starting, the amount of fuel pumped per unit time to the pressure accumulator chamber is considerably low. For example, the fuel pressure in the pressure accumulator chamber is reduced to near atmospheric pressure. In some cases, it takes several seconds for the fuel pressure in the pressure accumulating chamber to rise.

  Therefore, at the time of engine start when the fuel discharge amount of the high pressure fuel pump becomes small, when the fuel pressure in the pressure accumulation chamber is lower than a predetermined value, the fuel discharged from the low pressure fuel pump is directly supplied to the pressure accumulation chamber, and the fuel pressure is predetermined. There has been proposed a technique in which the pressure is increased by supplying fuel pressurized by a high pressure fuel pump to a pressure accumulating chamber after reaching the value (see, for example, Patent Document 1). According to this conventional technology, even when the fuel pressure in the pressure accumulating chamber is reduced to near atmospheric pressure, the time until the fuel pressure in the pressure accumulating chamber is increased to the feed pressure can be shortened. In particular, the time for boosting the fuel by the high-pressure fuel pump can be shortened.

  On the other hand, when the fuel in the fuel tank is filled from an empty state, not only the fuel pressure in the pressure accumulating chamber is reduced to near atmospheric pressure, but also a vapor exists in the pressure accumulating chamber. Further, when the engine is stopped after the engine is loaded under a high temperature environment, the fuel pressure in the pressure accumulating chamber falls below the saturated vapor pressure with respect to the fuel temperature at that time, and a vapor is generated in the pressure accumulating chamber. In these situations, the vapor in the pressure accumulating chamber must be compressed and crushed by the pressure of the fuel, and the time required for boosting the fuel is significantly longer than when the pressure accumulating chamber is filled with fuel.

  Therefore, a fuel pipe connecting the accumulator chamber and the fuel tank, and an open / close valve in the middle of the fuel pipe, and when the engine is started, the open / close valve is controlled to quickly open the vapor existing in the accumulator chamber. A technique of discharging is proposed (see, for example, Patent Document 2). According to this conventional technique, not only does the fuel pressure in the pressure accumulator chamber decrease to near atmospheric pressure, but even if a vapor exists in the pressure accumulator chamber, the vapor is placed outside the pressure accumulator chamber. By discharging, the time for boosting the fuel pressure in the pressure accumulating chamber can be greatly shortened. As a result, the time for boosting the fuel by the high-pressure fuel pump is also shortened.

  Conventionally, a technique has been proposed in which the fuel injection valve is driven with a fuel injection valve drive time sufficiently longer than the fuel injection valve drive time corresponding to the required start injection amount when the engine is started (for example, Patent Document 3). This technique also allows the time for boosting the fuel pressure in the pressure accumulating chamber to be greatly shortened by discharging the vapor out of the pressure accumulating chamber, as in the case of the aforementioned Patent Document 2. As a result, the high pressure fuel The fuel pressurization time by the pump is also shortened.

JP-A-9-250426 JP 7-77119 A JP 2003-166435 A

  In the technique described in Patent Document 1 described above, when the fuel pressure is reduced to near atmospheric pressure in the state where no vapor exists in the pressure accumulating chamber, the fuel pressurization time can be shortened. However, when vapor is present in the pressure accumulating chamber, the pressure of the fuel is increased until the vapor is compressed by the feed pressure fuel supplied from the low pressure fuel pump until the vapor is crushed and dissolved in the fuel. There was a problem that it became dull and the boosting time was significantly increased.

  On the other hand, in the technique described in Patent Document 2, the vapor can be discharged to the fuel tank through the on-off valve, and the pressure increase time can be shortened. However, in order to realize the technique described in Patent Document 2, it is necessary to add a fuel pipe and an on-off valve for connecting the pressure accumulating chamber and the fuel tank, which causes a significant cost increase. was there.

  Further, in the technique described in Patent Document 3, the vapor can be discharged into the combustion chamber through the fuel injection valve, and the pressure increase time is shortened without incurring the cost increase as in the technique described in Patent Document 2. Is possible. However, in the technique described in Patent Document 3, the fuel injection valve is driven with a drive time sufficiently longer than the drive time corresponding to the injection amount required by the engine, so that when the fuel pressure rises faster than expected, the fuel injection amount There is a problem that excessively increases the amount of misfire, which leads to rich misfire and engine oil dilution.

  Furthermore, since the technology of Patent Document 3 is based on a port injection engine that injects fuel into the intake pipe of the engine, it does not apply to a direct injection engine that directly injects fuel into the combustion chamber. There is also a problem that it cannot be applied. That is, in a port injection engine that injects fuel into the intake pipe, the pressure in the intake pipe does not rise above the atmospheric pressure regardless of the stroke state of the combustion chamber. There is no problem even if the driving time is longer than the normal driving time. However, in a cylinder injection engine that directly injects fuel into the combustion chamber, if the drive time of the fuel injection valve is increased, the pressure in the combustion chamber increases when the combustion chamber shifts from the intake stroke to the compression stroke. Therefore, in the worst case, there is a concern that the vapor once discharged into the combustion chamber may flow back into the pressure accumulating chamber.

  The present invention has been made in view of such a problem in the conventional apparatus, and an object of the present invention is when a fuel in a fuel tank is filled from an empty state in an in-cylinder injection engine. When the engine is stopped after a load operation of the engine in a high-temperature environment, when the vapor exists in the pressure accumulation chamber, the vapor existing in the pressure accumulation chamber is discharged in a short time to increase the fuel pressure. It is an object of the present invention to provide a fuel injection control device for an in-cylinder injection engine that can shorten the time.

A fuel injection control device for an in-cylinder injection engine according to the present invention includes a fuel injection valve arranged for each cylinder so as to directly inject fuel into a combustion chamber, and an accumulator that is connected in common with the fuel injection valve and stores high-pressure fuel. A fuel pressure sensor for detecting the pressure of the fuel in the pressure storage chamber, a low pressure fuel pump for pumping up fuel in the fuel tank and discharging it to the low pressure passage, and a low pressure pressure regulator for adjusting the fuel in the low pressure passage to a feed pressure A high-pressure fuel pump that sucks fuel in the low-pressure passage and discharges the fuel into the pressure accumulation chamber, a discharge valve that allows only fuel to flow from the high-pressure fuel pump to the pressure accumulation chamber, and a pressure of the fuel in the pressure accumulation chamber In a fuel injection control device for a cylinder injection engine having a fuel pressure control valve for adjustment, the low pressure fuel pump is operating and detected by the fuel pressure sensor When the accumulation chamber of the fuel pressure which is below the feed pressure, is characterized in that to start the forced driving of the fuel injection valve in the cylinder in the exhaust stroke.
A fuel injection control device for a direct injection engine according to the present invention includes a fuel injection valve arranged for each cylinder so as to directly inject fuel into a combustion chamber, and a high pressure fuel connected in common with the fuel injection valve. A pressure accumulation chamber for storing, a fuel pressure sensor for detecting the pressure of the fuel in the pressure accumulation chamber, a low pressure fuel pump for pumping up fuel in a fuel tank and discharging it to the low pressure passage, and a low pressure for adjusting the fuel in the low pressure passage to a feed pressure A regulator, a high-pressure fuel pump that draws fuel in the low-pressure passage and discharges the fuel into the pressure accumulation chamber, a discharge valve that allows only fuel to flow from the high-pressure fuel pump to the pressure accumulation chamber, and a fuel in the pressure accumulation chamber In a fuel injection control device for a direct injection engine having a fuel pressure control valve for adjusting pressure, a fuel temperature detection for directly or indirectly detecting the temperature of fuel in the pressure accumulating chamber. And the fuel pressure in the pressure accumulating chamber detected by the fuel pressure sensor is lower than a saturated vapor pressure corresponding to the fuel temperature detected by the fuel temperature detecting means. During this time, the forced drive of the fuel injection valve in the cylinder in the exhaust stroke is started.

According to the fuel injection control device for a direct injection engine according to the present invention, the low pressure fuel pump is operating, and the fuel pressure in the pressure accumulating chamber detected by the fuel pressure sensor is adjusted by the low pressure pressure regulator. Since the forced drive of the fuel injection valve in the cylinder in the exhaust stroke is started when it is lower, the vapor generated in the pressure accumulation chamber is discharged into the combustion chamber through the fuel injection valve of the exhaust stroke cylinder Therefore, it is possible to shorten the pressure increase time of the fuel in the pressure accumulating chamber without increasing the cost.
According to the fuel injection control device for a direct injection engine according to the present invention, the low pressure fuel pump is operating, and the fuel pressure detected by the fuel pressure sensor is saturated corresponding to the detected fuel temperature. When the vapor pressure is lower, the forced drive of the fuel injection valve in the cylinder in the exhaust stroke is started, so that the vapor generated in the pressure accumulating chamber passes into the combustion chamber through the fuel injection valve of the exhaust stroke cylinder. It is possible to discharge the fuel, and the pressure increase time of the fuel in the pressure accumulating chamber can be shortened without increasing the cost.

  Further, according to the fuel injection control device for a cylinder injection engine according to the present invention, the fuel injection valve in the exhaust stroke cylinder can be forcibly driven to promote vapor discharge in the pressure accumulating chamber. The driving time of the valve can be changed without changing the driving time corresponding to the injection amount required by the engine. Therefore, even when the fuel pressure in the pressure accumulating chamber rises faster than expected, the amount of fuel that contributes to combustion (the amount of fuel injected in the intake stroke cylinder) does not become excessive, resulting in rich misfires and engine It does not cause oil dilution.

  Further, according to the fuel injection control device for a cylinder injection engine according to the present invention, the fuel injection valve of the exhaust stroke cylinder in which the pressure in the combustion chamber does not become higher than the feed pressure is forcibly driven. The vapor discharged into the combustion chamber is prevented from flowing back into the pressure accumulating chamber.

Embodiment 1 FIG.
Hereinafter, a fuel injection control device for a direct injection engine according to Embodiment 1 of the present invention will be described in detail with reference to the drawings. 1 is a block diagram showing a fuel injection control device for a direct injection engine according to Embodiment 1 of the present invention.

  In FIG. 1, a fuel injection valve 39 (four in the figure) provided for each cylinder of the engine 40 is connected to a pressure accumulating chamber 36, which is a common high-pressure fuel pipe, at one end thereof. The fuel in 36 is distributed and supplied to each fuel injection valve 39. Each other end of the fuel injection valve 39 is disposed so as to directly inject fuel into each combustion chamber of the engine 40. Each fuel injection valve 39 is controlled to open and close, so that high pressure fuel is directly injected into the combustion chamber of the corresponding cylinder. The fuel injected from each fuel injection valve 39 is mixed with the air in the combustion chamber and becomes an air-fuel mixture. A fuel pressure sensor 61 is attached to the pressure accumulating chamber 36 as a means for detecting the internal fuel pressure.

  The engine 40 is provided with a starter (not shown) for applying a rotational force to the crankshaft by cranking at the time of starting. This starter operates in response to an operation of an ignition switch (not shown) by the driver. That is, the ignition switch is movable between an OFF position and an ON position, and between an ON position and a START position, as is well known. The starter is operated while the ignition switch is operated from the ON position to the START position.

  The low-pressure fuel pump 31 is driven by an electric motor (not shown) that uses a battery as a power source. In the first embodiment, the low-pressure fuel pump 31 starts operating when the ignition switch is operated from the OFF position to the ON position, and is stopped when the ignition switch is operated from the ON position to the OFF position. The low pressure fuel pump 31 is connected to the high pressure fuel pump 20 through the low pressure passage 33. The low pressure fuel pump 31 pumps fuel from the fuel tank 30 and discharges the fuel toward the high pressure fuel pump 20.

  The low-pressure fuel pump 31 is characterized by a large discharge amount and a low discharge pressure. Further, since it is driven by the electric motor, the discharge characteristic of the low-pressure fuel pump 31 at the time of starting is not affected by the rotational fluctuation of the engine 40. In the middle of the low-pressure passage 33, a low-pressure pressure regulator 32 is provided for adjusting the fuel pressure in the low-pressure passage 33 to a constant value (feed pressure).

  The high pressure fuel pump 20 includes a pump plunger 22, a pressurizing chamber 23, and a fuel pressure control valve 10. The pump plunger 22 reciprocates in the pump cylinder 21 based on the rotation of the cam 25 attached to the cam shaft 24 of the engine 40. Accordingly, the operation start timing of the pump plunger 22 is the same as the timing at which the camshaft 24 starts rotating, that is, the timing at which the starter starts operating when the ignition switch is operated from the ON position to the START position.

  The pressurizing chamber 23 is partitioned by the pump cylinder 21 and the pump plunger 22, and the low-pressure passage 33 described above is connected to the pressurizing chamber 23. In the pressurizing chamber 23, a connection point with the low-pressure passage 33 is a fuel suction port 23a. The pressurizing chamber 23 is connected to a pressure accumulating chamber 36 through a high-pressure fuel passage 35. In the middle of the high-pressure fuel passage 35, a discharge valve 34 for preventing a back flow of the fuel discharged from the high-pressure fuel pump 20 is provided.

  The fuel pressure control valve 10 includes an electromagnetic solenoid 11 and performs an opening / closing operation by controlling energization of the electromagnetic solenoid 11. In a state where the energization to the electromagnetic solenoid 11 is stopped, the fuel pressure control valve 10 is opened by the spring 12. That is, the fuel inlet 23a is opened, and the low pressure passage 33 and the pressurizing chamber 23 are in communication with each other. In this state, when the pump plunger 22 moves in the direction of increasing the volume of the pressurizing chamber 23 (downward in FIG. 5) (during the intake stroke), the fuel sent from the low pressure fuel pump 31 is transferred to the low pressure passage. The air is sucked into the pressurizing chamber 23 through 33.

  When the pump plunger 22 moves in the direction in which the volume of the pressurizing chamber 23 contracts (upward in FIG. 5) (during the pressure feed stroke), the fuel pressure control valve 10 is applied to the spring 12 by energizing the electromagnetic solenoid 11. The valve is closed against it. That is, the fuel inlet 23a is closed, and the communication between the low pressure passage 33 and the pressurizing chamber 23 is blocked. With the movement of the pump plunger 22, the fuel pressure in the pressurizing chamber 23 rises and the discharge valve 34 is opened, so that fuel is supplied into the pressure accumulating chamber 36 through the high-pressure fuel passage 35.

  The fuel discharge amount in the high-pressure fuel pump 20 is adjusted by controlling the valve closing start timing of the fuel pressure control valve 10 and adjusting the valve closing period of the fuel pressure control valve 10 during the pumping stroke. . That is, if the valve closing start timing of the fuel pressure control valve 10 is advanced to extend the valve closing period, the fuel discharge amount increases. On the contrary, if the valve closing start time of the fuel pressure control valve 10 is delayed to shorten the valve closing period, the fuel discharge amount is reduced. The fuel pressure in the pressure accumulating chamber 36 is controlled by adjusting the fuel discharge amount of the high-pressure fuel pump 20 as described above.

  In the first embodiment, the engine 40 is a four-cylinder engine, and the high-pressure fuel pump 20 is configured to pump fuel twice with respect to two rotations of the crankshaft. That is, the high-pressure fuel pump 20 pumps fuel once for two fuel injections in the two cylinders of the engine 40. In the high-pressure fuel pump 20 configured as described above, the fuel discharge amount per one time is smaller than that of the low-pressure fuel pump 31 (tens of tens of the discharge amount of the low-pressure fuel pump 31), but the discharge pressure is low-pressure fuel. It is characterized by being higher than the pump 31 (tens of times the discharge pressure of the low-pressure fuel pump 31).

  A relief valve 37 is disposed in a relief passage 38 that connects the pressure accumulating chamber 36 and the fuel tank 30. When the fuel pressure in the pressure accumulation chamber 36 becomes excessively high, the relief valve 37 is opened and the high-pressure fuel in the pressure accumulation chamber 36 flows out to the fuel tank 30. Therefore, it is suppressed that the fuel pressure in the pressure accumulating chamber 36 becomes excessively high.

  The electronic control unit (hereinafter referred to as ECU) 60 controls the fuel injection amount from the fuel injection valve 39, the injection timing, and the energization of the fuel pressure control valve 10. In addition to the detection signal of the fuel pressure sensor 61 that detects the fuel pressure in the pressure accumulating chamber 36, the ECU 60 reads detection signals of various sensors that will be described later that detect the operating state of the engine, such as the engine rotation speed, the intake air amount, and the engine water temperature. Thus, the fuel injection amount required by the engine 40 and an appropriate fuel injection timing are calculated, and an injection signal corresponding to the calculation result is output to the fuel injection valve 39 to execute fuel injection. Further, the ECU 60 performs control for boosting the fuel when the engine is started. This control is performed in order to promote atomization of the spray by increasing the fuel injection pressure at the start of the engine, thereby reducing the amount of injection at the start and reducing the generation of black smoke.

  Next, a specific configuration of the ECU 60 will be described. FIG. 2 is a block diagram showing a specific configuration of the ECU 60 according to the present invention. The same parts as those in FIG. 1 are given the same reference numerals. In FIG. 2, the phase detection means 602 detects the shaft position PH of the engine 40 based on the output signals of the crank angle sensor 64 and the cam angle sensor 65, and outputs the detected shaft position PH. The shaft position PH output from the phase detection unit 602 is input to a vapor discharge control unit 601 and a fuel injection valve driving unit 604 described later. If the shaft position PH of the engine 40 is known, it is possible to determine which cylinder is in which stroke state.

  The fuel injection amount calculation means 603 calculates the fuel injection amount per cylinder (engine 40) from the engine rotational speed NE obtained from the output signal of the crank angle sensor 64 and the intake air amount QA obtained from the output signal of the air flow sensor 66. Required injection amount) QF. The fuel injection amount QF per cylinder calculated by the fuel injection amount calculation unit 603 is output to a fuel injection valve driving unit 604 described later.

  The fuel injection valve driving unit 604 receives the shaft position PH of the engine 40 detected by the phase detection unit 602 and the fuel injection amount QF per cylinder calculated by the fuel injection amount calculation unit 603. The fuel injection valve 39 is driven and controlled at a predetermined driving timing and a driving time corresponding to the fuel injection amount QF. In the case of a cylinder injection engine, the fuel injection valve 39 is driven in the intake stroke or the compression stroke as the amount of fuel that contributes to combustion.

  The vapor discharge control means 601 is detected by the fuel pressure PF in the pressure accumulating chamber 39 detected by the fuel pressure sensor 61, the signal IG indicating the ON / OFF state of the ignition switch 62, and the fuel temperature estimation means 63 as the fuel temperature detection means. The detected fuel temperature TF, the engine speed NE obtained from the output signal of the crank angle sensor 63, the shaft position PH of the engine 40 detected by the phase detecting means 602, and the fuel remaining amount sensor 67. The remaining fuel amount LF is input, and vapor discharge control described later is performed.

  The fuel temperature estimating means 63 is configured to indirectly estimate the fuel temperature in the pressure accumulating chamber 36 using a sensor that detects engine temperature information such as engine water temperature and intake air temperature. Instead of the fuel temperature estimating means 63, a fuel temperature sensor capable of directly measuring the fuel temperature in the pressure accumulating chamber 36 may be used.

  The fuel injected into the cylinder of the internal combustion engine has a saturated vapor pressure characteristic as shown in FIG. That is, in FIG. 3, the horizontal axis indicates the fuel temperature, and the vertical axis indicates the fuel pressure. For example, when the fuel temperature is TX, the fuel pressure that becomes the saturated vapor pressure is PX. At this time, the region where the fuel pressure is higher than PX is a vapor non-generating region because of the physical properties of the fuel, the fuel is not vaporized and there is no vaporized component, but the region where the fuel pressure is lower than PX is the vapor generating region. Yes, fuel vaporization occurs and vaporized components are present.

  FIG. 4 is a time chart for explaining the vapor discharge control of the vapor discharge means 601, wherein (a) shows the state of the signal IG indicating the ON / OFF state of the ignition switch 62, and ON indicates that the ignition switch 62 is ON. The signal level when in the position, OFF is the signal level when the ignition switch 62 is in the OFF position. (B) shows the state of operation and stop of the low-pressure fuel pump 31, (c) shows the state of forcible drive of the fuel injection valve 39 in the exhaust stroke cylinder, and (d) shows the fuel pressure PF in the pressure accumulating chamber 36. Shows the behavior.

  In FIG. 4, the initial value of the fuel pressure PF in the pressure accumulating chamber 36 indicates the case of atmospheric pressure. Further, regarding the behavior of the fuel pressure PF in the pressure accumulating chamber 36, the time when vapor is not generated is indicated by a one-dot chain line, the time when vapor is generated is indicated by a two-dot chain line, and the fuel is generated when vapor is generated. A solid line indicates when the injection valve is forcibly driven.

  Now, in FIG. 4, when the ignition switch 62 is operated from OFF to ON at time T1, and the signal IG indicating the operating state changes from OFF level to ON level, the low pressure fuel pump is synchronized with this. 31 also starts operation. At this time, the fuel pressure PF in the pressure accumulating chamber 36 starts to increase from the atmospheric pressure to the feed pressure when the low-pressure fuel pump 31 starts operating.

  Here, in the case where no vapor is generated in the pressure accumulating chamber 36, the fuel pressure PF rises rapidly by the low pressure fuel pump 31 operating for a predetermined time TP as shown by a one-dot chain line in FIG. The feed pressure is reached by the time T2.

  On the other hand, in the case where vapor is generated in the pressure accumulating chamber 36, it takes time to compress the vapor existing in the pressure accumulating chamber 36, and the increase in the fuel pressure PF is significantly slowed. As shown by the two-dot chain line, The feed pressure is finally reached at time T5.

  Further, when the fuel injection valve is forcibly driven when vapor is generated in the pressure accumulating chamber 36, as shown by the solid line, the low-pressure fuel pump 31 is operated at the time T2 when it is operated for a time TP or more. Since the fuel pressure PF does not reach the predetermined pressure PX even at the time point, the fuel injection valve 39 of the exhaust stroke cylinder is forcibly driven between times T2 and T3 as shown in FIG. The vapor in the pressure accumulating chamber 36 is discharged through the fuel injection valve 39. As a result, the fuel pressure PF rises rapidly and reaches the feed pressure at time T4 earlier than time T5.

  Further, the vapor discharge control means 601 determines the fuel pressure in the pressure accumulating chamber 39 detected by the fuel pressure sensor 61 when it is determined that the low pressure fuel pump 31 is operating due to the low pressure fuel pump 31 operating for a predetermined time TP or more. Even when the PF has not reached the saturated vapor pressure with respect to the fuel temperature detected by the fuel temperature detecting means 63, the fuel injection valve driving means 604 is forced to drive the fuel injection valve 39 in the cylinder in the exhaust stroke. Then, a forced drive command for the exhaust stroke cylinder is output, and the fuel injection valve 39 is forcibly driven. As a result, the vapor in the pressure accumulating chamber 36 is discharged through the forcibly driven fuel injection valve 39, the fuel pressure PF rises rapidly, and reaches the feed pressure at time T4 earlier than time T5.

  The vapor discharge control means 601 that operates as described above is a low-pressure fuel pump when the elapsed time after the ignition switch 62 changes state from OFF to ON, that is, when the operation of the low-pressure fuel pump 31 has exceeded a predetermined time TP. It is determined that 31 is operating.

  The vapor discharge control means 601 is configured to end the output of the exhaust stroke cylinder forcible drive command when the fuel pressure PF in the pressure accumulating chamber 39 detected by the fuel pressure sensor 61 reaches a predetermined pressure PX. Yes. As a result, the fuel injection valve driving means 604 ends the forced drive control of the fuel injection valve 39 in the cylinder in the exhaust stroke.

  Further, the vapor discharge control means 601 outputs a forced drive command for the exhaust stroke cylinder, and then the forced drive of the fuel injection valve 39 in the cylinder in the exhaust stroke is continued a predetermined number of times or for a predetermined time or more. Is also configured to end the output of the forced drive command for the exhaust stroke cylinder. As a result, the fuel injection valve driving means 604 ends the forced drive control of the fuel injection valve 39 in the cylinder in the exhaust stroke.

  Further, the vapor discharge control means 601 is configured to prohibit the forced drive of the fuel injection valve in the exhaust stroke cylinder when the fuel remaining amount FL detected by the fuel remaining amount sensor is below a predetermined amount.

  The aforementioned fuel injection valve drive means 604 starts forced drive of the fuel injection valve 39 in the cylinder in the exhaust stroke when a forced drive command for the exhaust stroke cylinder is input from the vapor discharge control means 601. When the engine 40 is rotating, when the fuel injection valve 39 in the cylinder in the exhaust stroke is forcibly driven and controlled, the drive control of the fuel injection valve 39 in the cylinder in the intake stroke at the same time is also controlled by the engine. 40 is driven in a driving time corresponding to the fuel injection amount QF required.

  Next, a series of operations of the vapor discharge control means 62 configured as described above will be described. FIG. 5 is a flowchart for explaining the operation. The subroutine of FIG. 5 is executed from the time when the signal IG indicates that the ignition switch 62 is in the ON position. In the following description of the operation, it is assumed that the fuel pressure control valve 10 is opened in the high pressure fuel pump 20 and the low pressure fuel pump 31 has the signal IG turned on and the ignition switch 62 is turned on before starting the engine. The operation shall be started from the time when the position is indicated.

  In FIG. 5, in step S101, it is determined whether or not the signal IG indicating ON / OFF of the ignition switch 62 indicates immediately after the ignition switch 62 is operated from the OFF position to the ON position. If the ignition switch 62 has just been operated from the OFF position to the ON position (YES), the process proceeds to step S102, the operating time TP of the low-pressure fuel pump 31 is cleared to zero, and then the process proceeds to step S103. The number C of forced driving of the fuel injection valve 39 in the exhaust stroke cylinder is cleared to zero. Further, the process proceeds to step S104, and the forced driving command flag F of the fuel injection valve 39 in the exhaust stroke cylinder is cleared to zero. Proceed to

  On the other hand, if it is determined in step S101 described above that the ignition switch 62 is not immediately after being operated from the OFF position to the ON position (NO), the process proceeds from step S101 to step S105 to operate the low-pressure fuel pump 31. The time TP is incremented to [TP = TP + 1], and the process proceeds to step S106.

  In step S106, it is determined whether or not the shaft position PH of the engine 40 has been detected by the phase detection means 602, that is, whether or not the stroke of each cylinder can be detected. If the shaft position PH of the engine 40 has been detected (YES), the process proceeds to step S107. On the other hand, if the shaft position PH has not been detected (NO), nothing is done and the process returns.

  In step S107, it is determined whether or not the operating time TP of the low-pressure fuel pump 31 has passed a predetermined time. Here, when the operating time TP of the low-pressure fuel pump 31 has exceeded the predetermined time (YES), the process proceeds to step S108, the fuel pressure PF in the pressure accumulation chamber 36 is read, and the process proceeds to step S109. On the other hand, if the operating time TP has not passed the predetermined time (in the case of NO), the process proceeds from step S107 to step S115.

  In step S109, it is determined whether or not the fuel pressure PF in the pressure accumulating chamber 36 read in step S108 has reached the predetermined pressure PX. Here, when the fuel pressure PF in the pressure accumulation chamber 36 does not reach the predetermined pressure PX (YES), the process proceeds to step S110. On the other hand, if the fuel pressure PF has reached the predetermined pressure PX (NO), the process proceeds to step S115.

  In step S110, it is determined whether or not the number C of forced driving of the fuel injection valve 39 in the exhaust stroke cylinder has reached the predetermined number CX. Here, if the number of forced driving times C has not reached the predetermined number of times CX (YES), the process proceeds to step S111. On the other hand, if the number of forced driving times C has reached the predetermined number of times CX (NO), the process proceeds to step S114, the forced injection command flag F of the fuel injection valve in the exhaust stroke cylinder is cleared to zero, and the process proceeds to step S115.

  In step S111, it is determined whether or not the fuel remaining amount LF detected by the fuel remaining amount sensor 67 is equal to or greater than a predetermined amount LX. If the remaining fuel amount LF is equal to or greater than the predetermined amount LX (YES), the process proceeds to step S112, the forced drive command flag F of the fuel injection valve 39 in the exhaust stroke cylinder is set to “1”, and then step S113. Then, the forcible drive count C is incremented to [C = C + 1], and the process proceeds to step S115.

  On the other hand, if it is determined in step S111 that the remaining fuel amount LF is less than the predetermined amount LX (NO), the process proceeds from step S111 to step S114 to forcibly drive the fuel injection valve for the exhaust stroke cylinder. F is cleared to zero and the process proceeds to step S115.

  In step S115, it is determined whether or not the forced drive command flag F of the fuel injection valve 39 in the exhaust stroke cylinder is set to “1”. If the forcible drive command flag F is [F = 1] (YES), the routine proceeds to step S116 where the fuel injection valve drive means 604 forcibly drives the fuel injection valve 39 in the exhaust stroke cylinder. To exit and return.

  On the other hand, if it is determined in step S115 that the forced drive command flag F is [F = 0] (NO), the routine proceeds to step S117, where the fuel injection valve in the exhaust stroke cylinder by the fuel injection valve driving means 604 is obtained. The forced drive of 39 is prohibited, and the process is returned and the process returns.

  The above-described series of operations of the vapor discharge control means 601 can function even when the engine 40 is stopped if the phase position when the engine 40 is stopped can be detected. .

  According to the fuel injection control device for a direct injection engine according to the first embodiment of the present invention, the low pressure fuel pump is operating, and the fuel pressure in the pressure accumulating chamber detected by the fuel pressure sensor is below a predetermined pressure. Since the forced drive of the fuel injection valve in the cylinder in the exhaust stroke is started, the vapor generated in the pressure accumulation chamber can be discharged into the combustion chamber through the fuel injection valve of the exhaust stroke cylinder Thus, the pressure increase time of the fuel in the pressure accumulating chamber can be shortened without increasing the cost.

  Further, according to the fuel injection control device for an in-cylinder injection engine according to Embodiment 1 of the present invention, it is possible to promote vapor discharge in the pressure accumulating chamber by forcibly driving the fuel injection valve in the exhaust stroke cylinder. The drive time of the fuel injection valve in the intake stroke cylinder can be left unchanged without changing the drive time corresponding to the injection amount required by the engine. Therefore, even when the fuel pressure in the pressure accumulating chamber rises faster than expected, the amount of fuel that contributes to combustion (the amount of fuel injected in the intake stroke cylinder) does not become excessive, resulting in rich misfires and engine It does not cause oil dilution.

  Furthermore, according to the fuel injection control device for a direct injection engine according to the first embodiment of the present invention, the fuel injection valve of the exhaust stroke cylinder in which the pressure in the combustion chamber does not become higher than the feed pressure is forcibly driven. Therefore, the vapor once discharged to the combustion chamber is prevented from flowing back to the pressure accumulating chamber.

  Further, according to the fuel injection control device for a direct injection engine according to the first embodiment of the present invention, when the fuel pressure in the pressure accumulating chamber is below the predetermined value set as the pressure value lower than the feed pressure. Since it is determined that vapor is generated in the pressure accumulating chamber, the fuel pressure in the pressure accumulating chamber decreases to near atmospheric pressure as when the fuel in the fuel tank is filled from the empty state. In this state, the fuel injection valve of the exhaust stroke cylinder can be forcibly driven after accurately determining that the vapor exists in the pressure accumulating chamber.

  Furthermore, according to the fuel injection control device for a direct injection engine according to the first embodiment of the present invention, when the detected fuel pressure in the pressure accumulating chamber is lower than the saturated vapor pressure corresponding to the fuel temperature in the pressure accumulating chamber. Because it is judged that vapor is generated in the pressure accumulator chamber, the fuel pressure in the pressure accumulator chamber has dropped to near atmospheric pressure as when the engine was stopped after a load operation of the engine in a high temperature environment. Even in the absence, it is possible to forcibly drive the fuel injection valve of the exhaust stroke cylinder after accurately determining that the vapor exists in the pressure accumulating chamber.

  By the way, by forcibly driving the fuel injection valve in the cylinder in the exhaust stroke, the vapor is discharged into the combustion chamber, and the fuel pressure in the pressure accumulating chamber is quickly increased. However, when the vapor is discharged and the pressure accumulating chamber begins to fill with fuel, the fuel itself is discharged into the combustion chamber instead of the vapor, and further, this fuel may flow into the exhaust pipe, which may deteriorate the exhaust gas. come. According to the fuel injection control device for a direct injection engine according to Embodiment 1 of the present invention, when the fuel pressure in the pressure accumulating chamber becomes equal to or higher than the predetermined pressure, the forced drive of the fuel injection valve of the exhaust stroke cylinder is finished immediately. As a result, the above-mentioned concerns can be avoided. The predetermined pressure when the forced drive of the fuel injection valve in the exhaust stroke cylinder ends is assumed to be the same pressure value as the predetermined pressure when the forced drive of the fuel injection valve in the cylinder in the exhaust stroke is started. However, the pressure values need not be the same, and hysteresis may be set between the two predetermined values in advance based on actual machine behavior in order to stabilize the control operation and optimize the effect.

  On the other hand, for example, when starting the engine without running out of gas, when the output value of the fuel pressure sensor is stuck at a value equivalent to atmospheric pressure, or when the fuel system is damaged and a large amount of fuel leaks It is expected that the fuel pressure will not increase even if the fuel injection valve is forcibly driven in the cylinder in the exhaust stroke. In that case, the fuel injection valve open / close drive (so-called fuel injection valve stroke) is continued for a long time in the absence of fuel in the pressure accumulator chamber, which may cause performance deterioration due to abnormal heat generation or wear of the fuel injection valve. is there. According to the fuel injection control device for a direct injection engine according to Embodiment 1 of the present invention, when the forced drive of the fuel injection valve in the cylinder in the exhaust stroke is continued a predetermined number of times or for a predetermined time or more, the exhaust stroke Since the forced drive of the fuel injection valve in the cylinder is terminated, the above-mentioned concern can be avoided. Here, the predetermined number of times or the predetermined time is set in advance as a value equal to or less than the number of operations that does not impair the reliability of the fuel injection valve even if the fuel injection valve is intermittently driven in a state where there is no fuel circulation. The

  Further, according to the fuel injection control device for a direct injection engine according to Embodiment 1 of the present invention, when the remaining amount of fuel in the fuel tank is below a predetermined amount, the fuel injection valve is forced in the exhaust stroke cylinder. By prohibiting the driving itself, abnormal heat generation and wear of the fuel injection valve due to the stroke of the fuel injection valve are prevented.

It is a block diagram which shows the structure of the fuel-injection control apparatus of the cylinder injection engine which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of ECU in the fuel-injection control apparatus of the cylinder injection engine which concerns on Embodiment 1 of this invention. It is a characteristic view which shows the saturated vapor pressure characteristic of a fuel. It is a time chart explaining operation | movement of the fuel-injection control apparatus of the cylinder injection engine which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the fuel-injection control apparatus of the cylinder injection engine which concerns on Embodiment 1 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel pressure control valve 11 Electromagnetic solenoid 12 Spring 20 High pressure fuel pump 21 Pump cylinder 22 Pump plunger 23 Pressurizing chamber 23a Fuel inlet 24 Cam shaft 25 Pump cam 30 Fuel tank 31 Low pressure fuel pump 32 Low pressure pressure regulator 33 Low pressure passage 34 Discharge valve 35 High pressure fuel passage 36 Pressure accumulating chamber 37 Relief valve 38 Relief passage 39 Fuel injection valve 40 Engine 60 ECU
Reference Signs List 61 Fuel pressure sensor 62 Ignition switch 63 Fuel temperature estimation means 64 Crank angle sensor 65 Cam angle sensor 66 Air flow sensor 67 Fuel remaining amount sensor 601 Vapor discharge control means 602 Phase detection output means 603 Fuel injection amount calculation means 604 Fuel injection valve drive means TP Operation time of the low-pressure fuel pump PF Fuel pressure in the pressure accumulator chamber LF Fuel level in the fuel tank

Claims (6)

A fuel injection valve arranged for each cylinder so as to inject fuel directly into the combustion chamber, a pressure accumulation chamber connected in common with the fuel injection valve for storing high-pressure fuel, and a fuel pressure for detecting the pressure of the fuel in the pressure accumulation chamber A sensor, a low-pressure fuel pump that pumps up fuel in a fuel tank and discharges the fuel into a low-pressure passage; a low-pressure pressure regulator that adjusts fuel in the low-pressure passage to a feed pressure; In-cylinder injection comprising: a high-pressure fuel pump that discharges to the pressure chamber; a discharge valve that allows only fuel to flow from the high-pressure fuel pump to the pressure accumulation chamber; and a fuel pressure control valve that adjusts the pressure of the fuel in the pressure accumulation chamber In an engine fuel injection control device,
When the low-pressure fuel pump is operating and the fuel pressure in the pressure accumulating chamber detected by the fuel pressure sensor is lower than the feed pressure , forced driving of the fuel injection valve in the cylinder in the exhaust stroke is started. A fuel injection control device for an in-cylinder injection engine. When the fuel pressure in the accumulator chamber which is detected by the pressure sensor becomes the feed pressure above the cylinder according to claim 1, characterized in that to terminate the forced driving of the fuel injection valve in the cylinder in the exhaust stroke A fuel injection control device for an internal injection engine. A fuel injection valve arranged for each cylinder so as to inject fuel directly into the combustion chamber, a pressure accumulation chamber connected in common with the fuel injection valve for storing high-pressure fuel, and a fuel pressure for detecting the pressure of the fuel in the pressure accumulation chamber A sensor, a low-pressure fuel pump that pumps up fuel in a fuel tank and discharges the fuel into a low-pressure passage; a low-pressure pressure regulator that adjusts fuel in the low-pressure passage to a feed pressure; In-cylinder injection comprising: a high-pressure fuel pump that discharges to the pressure chamber; a discharge valve that allows only fuel to flow from the high-pressure fuel pump to the pressure accumulation chamber; and a fuel pressure control valve that adjusts the pressure of the fuel in the pressure accumulation chamber In an engine fuel injection control device,
A fuel temperature detecting means for directly or indirectly detecting the temperature of the fuel in the pressure accumulating chamber;
When the low-pressure fuel pump is operating and the fuel pressure in the pressure accumulating chamber detected by the fuel pressure sensor is below a saturated vapor pressure corresponding to the fuel temperature detected by the fuel temperature detecting means, A fuel injection control device for an in-cylinder injection engine, which starts forcibly driving a fuel injection valve in a cylinder in an exhaust stroke. When the fuel pressure in the accumulator chamber which is detected by said fuel pressure sensor becomes the saturated vapor pressure or more, according to claim 3, characterized in that to terminate the forced driving of the fuel injection valve in the cylinder in the exhaust stroke A fuel injection control device for a cylinder injection engine. The forced drive of the fuel injection valve in the cylinder in the exhaust stroke is terminated when the forced drive of the fuel injection valve in the cylinder in the exhaust stroke has passed a predetermined number of times or a predetermined time or more. The fuel injection control device for a direct injection engine according to any one of claims 1 to 4 .   A fuel remaining amount sensor for detecting a fuel remaining amount in the fuel tank, and a fuel injection valve in a cylinder in an exhaust stroke when the fuel remaining amount detected by the fuel remaining amount sensor is below a predetermined amount; 6. The fuel injection control device for a direct injection engine according to claim 1, wherein forcible driving is prohibited.

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