JP2011058369A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine, which reduces a load applied to the drive system of a high-pressure pump when the internal combustion engine is restarted from an automatically stopped state. <P>SOLUTION: This control device controls the internal combustion engine by an accumulator fuel injection device and performs idling stop control, including: an idling stop condition satisfaction detection section detecting the satisfaction of a predetermined idling stop condition and also outputting instructions to automatically stop the internal combustion engine; a restart condition satisfaction detection section detecting the satisfaction of a predetermined restart condition during the automatic stop of the internal combustion engine and also outputting instructions to restart the internal combustion engine; a rail pressure detection section detecting pressure in a common rail; and a flow rate control valve control section closing a flow rate control valve for a predetermined time after restarting the internal combustion engine when the pressure in the common rail is higher than a predetermined threshold in restarting the internal combustion engine. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control device for controlling an internal combustion engine using an accumulator fuel injection device. In particular, the present invention relates to a control device for an internal combustion engine capable of executing idling stop control.

  Conventionally, as a device for injecting fuel into a cylinder of an internal combustion engine such as a diesel engine, an accumulator fuel injection device (common rail system) provided with a common rail for accumulating high-pressure fuel supplied by a high-pressure pump is known. It is used. A plurality of fuel injection valves are connected to the common rail, and various fuels are controlled by controlling the valve opening timing and valve opening time of each fuel injection valve while high-pressure fuel is supplied to each fuel injection valve. Fuel is injected into the cylinder of the internal combustion engine in an injection pattern.

  In this accumulator fuel injection device, the high pressure pump is usually configured to be driven by the power of the internal combustion engine. Specifically, the camshaft of the high-pressure pump is connected to the drive shaft of the internal combustion engine via a gear, and the high-pressure pump also operates during operation of the internal combustion engine, while the high-pressure pump also stops when the internal combustion engine stops. .

  In the accumulator fuel injection device, the pressure in the common rail (hereinafter referred to as “rail pressure”) greatly affects the fuel injection characteristics. As a rail pressure control method, there is a control method in which the flow rate of fuel supplied to the pressurizing chamber of the high pressure pump is adjusted by a flow control valve, and the flow rate of high pressure fuel supplied from the high pressure pump to the common rail is adjusted.

  In the control of an internal combustion engine using such an accumulator type fuel injection device, in recent years, the internal combustion engine has been suspended during the temporary stop of a vehicle on which the internal combustion engine is mounted for the purpose of improving fuel consumption, reducing the amount of exhaust gas, and noise. An idling stop control for automatically stopping the vehicle has been put into practical use. In the idling stop control, the internal combustion engine is automatically stopped when a predetermined idling stop condition is satisfied, and the internal combustion engine is restarted when a predetermined restart condition is satisfied during the automatic stop.

  In a vehicle equipped with an internal combustion engine capable of executing the idling stop control, restartability from the automatic stop state is an element that has an important influence on the merchantability. Therefore, a control device for an internal combustion engine has been proposed that can shorten the stop time during the idling stop control of the internal combustion engine and can reliably improve the restartability. More specifically, when the internal combustion engine is automatically stopped by idling stop control, the discharge flow rate of the high-pressure pump is increased and the load of the internal combustion engine is adjusted to stop the crank angle at a predetermined crank angle suitable for restarting. A control device for an internal combustion engine is disclosed in which fuel injection is started simultaneously with the starter operation at the time of restart (see Patent Document 1).

JP 2008-163796 A (Full text, all figures)

  When the internal combustion engine is, for example, a diesel engine, the compression ratio in the engine is sufficient to improve the restartability from the automatic stop state of the engine, and the fuel injection by the pressure accumulation type fuel injection device is possible. Is a factor. Of these two factors, whether or not the compression ratio is sufficient is a problem on the engine side, and whether or not fuel injection is possible is a problem on the accumulator fuel injection apparatus side. Whether or not fuel injection is possible in the accumulator type fuel injection device depends on whether or not the rail pressure is secured to a pressure higher than the pressure at which fuel can be normally injected (hereinafter referred to as “injectable pressure”).

  Therefore, in order to improve the restartability of the internal combustion engine, control may be performed so that the rail pressure is maintained at a high level even during the automatic stop of the internal combustion engine by the idling stop control. At this time, even if the fuel injection valve, the high-pressure pump, the pressure control valve, etc. connected to the common rail are closed, a part of the high-pressure fuel is released from a minute gap existing in the fuel high-pressure system including these. In some cases, the rail pressure gradually decreases due to leakage into the fuel low pressure system. Therefore, the target value of the rail pressure when starting to maintain the rail pressure during automatic stop is set to a value higher than the injectable pressure.

  Here, when the internal combustion engine is started while the rail pressure is maintained at a high level when the internal combustion engine is restarted, the driving torque generated when the high-pressure pump starts to move is remarkably increased, which greatly increases the driving system of the high-pressure pump. Will give a heavy load. Specifically, a fuel discharge valve that opens when the pressure in the pressurizing chamber exceeds the sum of the rail pressure and the set force of the valve spring is provided between the pressurizing chamber of the high-pressure pump and the common rail. Therefore, if the fuel is supplied to the pressurizing chamber of the high-pressure pump when the internal combustion engine is restarted and the high-pressure pump is driven in a state where the rail pressure is high, the period until the fuel discharge valve is opened is The pressure of is significantly increased. As a result, a large force for pushing up the plunger for pressurizing the fuel is required, and a great load is generated on the drive system of the high-pressure pump.

  In addition, when the high-pressure pump is stopped, the lubricating oil or lubricating fuel flows out at the contact portion between the cam fixed to the camshaft and the tappet that transmits the rotational force of the cam as the lifting force of the plunger, and the oil film is insufficient. It is in a state. Thus, if a large load is applied to the drive system of the high-pressure pump when the high-pressure pump starts to move when the oil film at the contact portion between the tappet and the cam is insufficient, the durability of the high-pressure pump is reduced. Connected.

  Therefore, the inventor of the present invention diligently tried to apply a high pressure pump when the rail pressure was higher than necessary when the internal combustion engine was restarted from the automatic stop state of the internal combustion engine by the idling stop control. The inventors have found that the above-described problem can be solved by delaying the fuel supply start timing to the pressure chamber by a predetermined time, and have completed the present invention. That is, an object of the present invention is to provide a control device for an internal combustion engine that can reduce a load applied to a drive system of a high-pressure pump when the internal combustion engine is restarted from an automatic stop state.

  According to the present invention, a pressure accumulation type fuel injection device comprising: a common rail to which a fuel injection valve is connected; a high pressure pump that pumps fuel to the common rail; and a flow rate control valve that adjusts the flow rate of fuel supplied to the high pressure pump. The control device for controlling the internal combustion engine by means of the control device for the internal combustion engine capable of executing the idling stop control detects that a predetermined idling stop condition is satisfied and instructs the internal combustion engine to automatically stop. An idling stop condition establishment detection unit that outputs a restart condition establishment detection unit that detects that a predetermined restart condition is established during automatic stop of the internal combustion engine and outputs an instruction to restart the internal combustion engine; A rail pressure detector for detecting the pressure in the common rail, and the pressure in the common rail when the internal combustion engine is restarted. A control device for an internal combustion engine comprising: a flow control valve control unit that closes the flow control valve for a predetermined time after the internal combustion engine is restarted, The problems described above can be solved.

  In configuring the control device for an internal combustion engine of the present invention, the first threshold value is preferably a value based on an allowable load from the high-pressure pump to the drive system of the high-pressure pump.

  Further, in configuring the control device for an internal combustion engine of the present invention, the flow control valve control unit maintains the flow control valve in a closed state during the automatic stop of the internal combustion engine, and in the common rail during the automatic stop of the internal combustion engine. It is preferable to open the flow control valve when the pressure falls below the first threshold.

  Further, in configuring the control device for an internal combustion engine of the present invention, the flow control valve control unit maintains the flow control valve in an open state when the internal combustion engine is automatically stopped, and when a predetermined restart condition is satisfied, It is preferable to close the flow rate control valve when it is determined that the pressure is equal to or higher than the first threshold value.

  In configuring the control device for an internal combustion engine of the present invention, the flow control valve control unit is configured so that, after restarting the internal combustion engine, the pressure in the common rail is greater than the first threshold value and the fuel from the fuel injection valve It is preferable to open the flow control valve when the pressure in the common rail quickly becomes less than the second threshold value that becomes less than the first threshold value due to the injection.

  Further, in configuring the control device for an internal combustion engine of the present invention, the flow control valve control unit opens the flow control valve when the rotational speed of the internal combustion engine becomes equal to or higher than a predetermined threshold after the internal combustion engine is restarted. Is preferred.

  According to the control device for an internal combustion engine of the present invention, when the rail pressure is maintained in an unnecessarily high state when the internal combustion engine is restarted from the automatic stop state by the idling stop control, the pressurization of the high pressure pump is performed. The fuel supply start timing to the chamber is delayed by a predetermined time. Therefore, when the rail pressure is high, fuel is not supplied to the pressurizing chamber of the high-pressure pump, the pressure in the pressurizing chamber is prevented from significantly increasing, and the load on the drive system of the high-pressure pump is reduced. The Even if the supply of fuel to the pressurizing chamber is started after a lapse of a predetermined time and the pressure in the pressurizing chamber is increased and a load is applied to the drive system, the tappet and the cam after the high pressure pump starts to move. Since the lubricating oil or the lubricating fuel penetrates into the contact area with the oil film to form an oil film, a decrease in the durability of the high-pressure pump can be suppressed.

1 is an overall view showing a configuration example of an accumulator fuel injection device. It is a figure for demonstrating the structural example of a high pressure pump. It is a block diagram for demonstrating the example of a structure of the control apparatus of the internal combustion engine concerning embodiment of this invention. It is a time chart for demonstrating the control at the time of maintaining a rail pressure in the high state at the time of the automatic stop of an internal combustion engine. It is a time chart for demonstrating control when a rail pressure falls at the time of the automatic stop of an internal combustion engine. It is a control flow performed by the control device for an internal combustion engine according to the embodiment of the present invention.

  Embodiments relating to a control device for an internal combustion engine according to the present invention will be specifically described below with reference to the drawings. However, this embodiment shows one aspect of the present invention and does not limit the present invention, and the aspect can be arbitrarily changed within the scope of the present invention. In addition, what attached | subjected the same code | symbol in each figure has shown the same member, and description is abbreviate | omitted suitably.

1. Accumulated Fuel Injection Device FIG. 1 shows a configuration example of an accumulator fuel injection device 50 used for controlling an internal combustion engine. The accumulator fuel injection device 50 is a device for injecting fuel into a cylinder of a diesel engine 40 mounted on a vehicle, and includes a fuel tank 1, a low pressure pump 2, a flow control valve 8, and a high pressure pump. 5, common rail 10, pressure control valve 12, fuel injection valve 13, control device 60 and the like as main elements.

  The low pressure pump 2 and the pressurizing chamber 5a of the high pressure pump 5 are connected by low pressure fuel passages 18a and 18b. The pressurizing chamber 5a of the high pressure pump 5 and the common rail 10, and the common rail 10 and the fuel injection valve 13 are respectively high pressure fuel. The passages 37 and 39 are connected. Further, return passages 30 a to 30 c for returning surplus fuel not injected from the fuel injection valve 13 to the fuel tank 1 are connected to the high-pressure pump 5, the common rail 10, the fuel injection valve 13, and the like.

  A flow control valve 8 is provided in the middle of the low-pressure fuel passage 18 b in the high-pressure pump 5. The flow rate control valve 8 is, for example, an electromagnetic proportional flow rate control valve in which the stroke amount of the valve body is variable depending on the supply current value and the area of the fuel passage is adjustable, and the fuel sent to the pressurizing chamber 5a. It is used to adjust the flow rate. The flow rate control valve 8 used in the present embodiment is configured as a normally open flow rate control valve in which a fuel flow path is fully opened in a non-energized state. However, it may be a normally closed flow control valve in which the fuel flow path is fully closed in a non-energized state.

  A pressure adjusting valve 14 disposed in parallel with the flow control valve 8 is provided in the fuel passage branched from the low pressure fuel passage 18 b upstream of the flow control valve 8. The pressure regulating valve 14 is connected to a return passage 30 a that communicates with the fuel tank 1. The pressure regulating valve 14 is an overflow valve that is opened when the differential pressure between the front and rear, that is, the pressure difference between the pressure in the low pressure fuel passage 18b and the pressure in the return passage 30a exceeds a predetermined value. ing. Therefore, in a state where the fuel is being pumped by the low-pressure pump 2, the pressure in the low-pressure fuel passages 18a and 18b is adjusted to be larger than the pressure in the return passage 30a by a predetermined differential pressure.

  The low pressure pump 2 sucks up the fuel in the fuel tank 1 and pumps it, and supplies the fuel to the pressurizing chamber 5a of the high pressure pump 5 through the low pressure fuel passages 18a and 18b. A low-pressure pump 2 shown in FIG. 1 is an in-tank electric pump provided in a fuel tank 1 and is driven by a voltage supplied from a battery to pump fuel. However, the low pressure pump 2 may be provided outside the fuel tank 1, or may be a gear pump that is driven by the power of the diesel engine 40.

  The high-pressure pump 5 pressurizes fuel introduced into the pressurizing chamber 5 a by the low-pressure pump 2 through the fuel intake valve 6 by the plunger 7, and supplies high-pressure fuel to the common rail through the fuel discharge valve 9 and the high-pressure fuel passage 37. 10 to pump. The fuel discharge valve 9 has a check valve structure in which the sealing performance is improved as the rail pressure located on the discharge side is higher.

  The cam 15 that drives the high-pressure pump 5 is fixed to a cam shaft that is connected to a drive shaft of the diesel engine 40 via a gear. The high-pressure pump 5 shown in FIG. 1 includes two plungers 7. The two plungers 7 are pushed up by cams 15 and fuel is pressurized in the two pressurizing chambers 5a to the common rail 10. High pressure fuel is pumped.

  The high-pressure pump 5 of the pressure-accumulation fuel injection device 50 of this embodiment has a fuel-lubricated configuration that uses fuel for injection as lubricating oil, and the fuel that is sent into the high-pressure pump 5 via the low-pressure fuel passage 18a is Once it flows into the cam chamber 16, it is further sent to the pressurizing chamber 5a via the low-pressure fuel passage 18b.

  The common rail 10 accumulates high-pressure fuel pumped from the high-pressure pump 5 and supplies high-pressure fuel to the plurality of fuel injection valves 13 connected via the high-pressure fuel passage 39. The common rail 10 is provided with a pressure control valve 12 and a pressure sensor 21. Among these, the pressure sensor 21 is a known pressure sensor such as a piezoelectric element sensor or a semiconductor sensor.

  The pressure control valve 12 is, for example, an electromagnetic proportional control valve in which the stroke amount of the valve body is variable depending on the supply current value and the area of the fuel passage is adjustable. The amount of power supplied to the pressure control valve 12 is controlled according to the target rail pressure and the required injection amount, and the rail pressure is adjusted by adjusting the flow rate of the high-pressure fuel discharged from the common rail 10 to the return passage 30b. .

  The fuel injection valve 13 connected to the common rail 10 includes a nozzle body provided with an injection hole and a nozzle needle that opens and closes the injection hole by advancing and retreating. In the fuel injection valve 13, the injection hole is closed by applying a back pressure to the rear end side of the nozzle needle, while the injection hole is opened by releasing the applied back pressure, and the high pressure supplied from the common rail 10. The fuel is injected into the cylinder of the diesel engine. The fuel injection valve 13 is capable of normal fuel injection when the rail pressure is equal to or higher than a predetermined injectable pressure.

  As the fuel injection valve 13, a piezo injector provided with a piezo element as back pressure control means, or an electromagnetically controlled fuel injection valve provided with an electromagnetic solenoid as back pressure control means is used. In the present embodiment, a piezo injector is used, and this piezo injector employs a structure in which fuel does not easily leak into the return passage 30c other than a passage for releasing back pressure.

2. High Pressure Pump FIG. 2 shows an example of a specific configuration of the high pressure pump 5. The high-pressure pump 5 includes a pump housing 51, a cylinder head 52 mounted in a cylindrical space 51a of the pump housing 51, a plunger 7 slidably held by a cylinder 52a of the cylinder head 52, and both ends of the cylinder head 52 and A spring 55, which is locked to the spring seat 59 and biases the plunger 7 downward, is interposed between the plunger 7 and the cam 15, and is used to push up the plunger 7 while centering as the cam 15 rotates. And a tappet structure 58. The fuel intake valve 6 is disposed in the upper opening of the cylinder 52a of the cylinder head 52, and the fuel discharge valve 9 is disposed in the lateral direction with respect to the axial direction of the cylinder 52a via the fuel discharge passage 52b. ing.
In FIG. 2, the flow control valve 8 and the pressure adjustment valve 14 provided in the high-pressure pump 5 are not shown.

  In the high-pressure pump 5, a part of the cylinder 52a of the cylinder head 52 is closed by the inner peripheral surface of the cylinder head 52, the plunger 7, the fuel intake valve 6, and the fuel discharge valve 9, and is configured as a pressurizing chamber 5a. Yes. The fuel that has flowed into the pressurizing chamber 5a through the fuel intake valve 6 is pressurized by the plunger 7 that is pushed up by the rotational movement of the cam 15 in the pressurizing chamber 5a. The pressure in the pressurizing chamber 5a exceeds the sum of the set force of the valve spring of the fuel discharge valve 9 and the rail pressure, and the fuel discharge valve 9 is pushed open, so that pressurized fuel is pumped toward the common rail. The

As described above, in the high-pressure pump 5, after the fuel pumped by the low-pressure pump flows into the cam chamber 16, a part thereof goes back and forth between the cam chamber 16 and the cylindrical space 51 a. This fuel is produced by contacting the roller 54 of the tappet structure 58 with the cam 15, the sliding portion between the cylindrical space 51 a and the tappet structure 58, the sliding portion between the cylinder 52 a and the plunger 7, and the camshaft 11. And reaches the sliding portion of the pump housing 51 with the bearing and functions as a lubricating oil.

  In the state where the high-pressure pump 5 is driven, the fuel in the cam chamber 16 spreads to each contact portion or sliding portion by the winding by the cam 15 or the discharge pressure of the low-pressure pump 2, and fuel lubrication using the fuel for injection is performed. Functions normally. On the other hand, when the high-pressure pump 5 is stopped, the fuel in the cam chamber 16 does not easily reach each contact part or sliding part, and the fuel flows out from each contact part or sliding part. , Oil film tends to be insufficient.

3. FIG. 3 shows functional parts of the control device 60 of the diesel engine 40 according to the present embodiment that are related to the control performed when the diesel engine 40 is restarted from the automatic stop state by the idling stop control. A configuration example represented by blocks is shown.

  The control device 60 includes an idling stop control unit 63 including an idling stop condition establishment detection unit 61 and a restart condition establishment detection unit 62, a target rail pressure calculation unit 65, a rail pressure detection unit 67, and a rail pressure determination unit 69. A fuel injection valve control unit 71, a flow rate control valve control unit 73, a pressure control valve control unit 75, and the like. The control device 60 is configured around a microcomputer having a known configuration, and each unit is realized by executing a program by the microcomputer. Further, the control device 60 is provided with a RAM (Random Access Memory) (not shown) for storing calculation results and detection results at each unit.

(1) Idling stop control unit The idling stop control unit 63 stops the fuel injection and stops the diesel engine 40 when the idling stop condition establishment detection unit 61 detects that the predetermined idling stop condition is established. An instruction signal is transmitted to the injection valve control unit 71. At this time, the idling stop control unit 63 transmits an instruction signal to the pressure control valve control unit 75 so as to energize the pressure control valve 12 with a predetermined holding current A1.

  Further, the idling stop control unit 63 resumes fuel injection when the restart condition establishment detection unit 62 detects that the predetermined restart condition is established while the diesel engine 40 is automatically stopped by the idling stop control. Then, an instruction signal is transmitted to the fuel injection valve control unit 71 so as to restart the diesel engine 40. When the restart condition is satisfied, the idling stop control unit 63 transmits a signal indicating that the restart condition is satisfied to the rail pressure determination unit 69, the flow rate control valve control unit 73, and the pressure control valve control unit 75.

  The idling stop conditions detected by the idling stop condition establishment detection unit 61 include, for example, that the engine switch Sw is on, that the detection position Sg of the gear sensor is neutral, that the side brake Br is applied, The detection position Sb of the pedal sensor is in a depressed state, the rotational speed Ne of the diesel engine 40 is below a predetermined threshold value, the state where the vehicle speed V is 0 continues for a predetermined time or more, etc. However, the present invention is not limited to this.

  The restart condition detected by the restart condition establishment detection unit 62 is that the detection position Sg of the gear sensor is released from the neutral state during the automatic stop of the diesel engine 40, the side brake Br is released, Some conditions such as the accelerator pedal Acc being depressed may be satisfied, but the present invention is not limited to this.

(2) Fuel Injection Valve Control Unit The fuel injection valve control unit 71 calculates the target fuel injection amount Qtgt based on the engine speed Ne, the accelerator operation amount Acc, and the like, and the fuel injection valve 13 corresponding to the target fuel injection amount Qtgt. And a control signal is output to the fuel injection valve 13. The fuel injection valve control unit 71 stops fuel injection when a signal indicating that the idling stop condition is satisfied is transmitted from the idling stop control unit 63, and resumes fuel injection when a signal indicating that the restart condition is satisfied is transmitted. To do.

(3) Target rail pressure calculation unit and rail pressure detection unit The target rail pressure calculation unit 65 calculates the target rail pressure Ptgt based on the engine speed Ne, the accelerator operation amount Acc, and the like, and stores it in the RAM. The rail pressure detection unit 67 continuously reads the sensor value of the pressure sensor 21 provided in the common rail 10, obtains the detected rail pressure Psensor, and stores it in the RAM.

(4) Rail pressure determination unit When a signal indicating that the idling stop condition is satisfied is transmitted from the idling stop condition satisfaction detection unit 61, the rail pressure determination unit 69 continuously reads the subsequent detection rail pressure Psensor and detects the detected rail pressure. It is determined whether Psensor is equal to or greater than a predetermined first threshold value Prail_thr1. The first threshold value Prail_thr1 is set to a value that does not increase the load on the drive system of the high-pressure pump 5 even when driving of the high-pressure pump 5 is started. For example, the first threshold value Prail_thr1 is larger than the injectable pressure at which normal injection from the fuel injection valve 13 is possible, and the holding current A1 is supplied to the pressure control valve 12 when the diesel engine 40 is automatically stopped by the idling stop control. The value is smaller than the rail pressure that is sometimes assumed.

  When the detected rail pressure Psensor is equal to or higher than the first threshold value Prail_thr1, the rail pressure determination unit 69 transmits an instruction signal to the flow control valve control unit 73 to close the flow control valve 8. On the other hand, when the detected rail pressure Psensor is lower than the first threshold value Prail_thr1, the rail pressure determination unit 69 transmits an instruction signal to the flow control valve control unit 73 to open the flow control valve 8.

(5) Flow rate control valve control unit and pressure control valve control unit The flow rate control valve control unit 73 and the pressure control valve control unit 75 are basically configured so that the detected rail pressure Psensor becomes the target rail pressure Ptgt. The energization control of the control valve 8 or the pressure control valve 12 is executed. Specifically, the flow control valve control unit 73 controls the flow rate of the fuel supplied to the pressurizing chamber 5 a of the high pressure pump 5 by adjusting the opening degree of the flow control valve 8, and from the high pressure pump 5 to the common rail 10. The rail pressure is adjusted by changing the flow rate of the high-pressure fuel that is pumped. Further, the pressure control valve control unit 75 controls the flow rate of the return fuel discharged from the common rail 10 to the return passage 30b by adjusting the opening of the pressure control valve 12, thereby adjusting the rail pressure.

  Whether the rail pressure is controlled by the flow rate control valve control unit 73, the pressure control valve control unit 75, or the combination of the two control units depends on the running state of the vehicle and the operating state of the diesel engine 40. It is divided according to. However, in any control mode, at least the flow rate control valve 8 is opened in order to supply fuel to the pressurizing chamber 5a of the high-pressure pump 5.

  Further, when a signal indicating that the idling stop condition is satisfied is transmitted from the idling stop control unit 63, the pressure control valve control unit 75 performs control to continuously energize the predetermined holding current A1 to the pressure control valve 12. . This holding current A1 is a control value such that the rail pressure is adjusted to a value larger than the injectable pressure, and even when the diesel engine 40 automatically stops for a relatively long time, the rail pressure at the time of restarting is maintained. Is set to such a value that is ensured to be equal to or higher than the injectable pressure.

Since the holding current A1 is energized to the pressure control valve 12, after the diesel engine 40 is automatically stopped, in the initial stage, the high pressure in the common rail 10 until the rail pressure becomes _a pressure Pra _{= a1} corresponding to the holding current A1. A part of the fuel is discharged to the return passage 30b. After that, although the rail pressure gradually decreases due to fuel leakage from a minute gap existing in the fuel high-pressure system, the rail pressure at the time of restart is higher than the injectable pressure unless the diesel engine 40 is stopped for a long time. To be easily maintained.

  Further, when a signal indicating that the idling stop condition is satisfied is transmitted from the idling stop control unit 63, the flow control valve control unit 73 interrupts energization to the flow control valve 8. Since the flow control valve 8 of the present embodiment has a normally open configuration, the flow control valve 8 is fully opened when power is cut off when the diesel engine 40 is automatically stopped. On the other hand, when the diesel engine 40 is automatically stopped by the idling stop control, the flow control valve control unit 73 energizes the flow control valve 8 in accordance with the instruction signal transmitted from the rail pressure determination unit 69 and turns the flow control valve 8 on. Fully closed. The flow control valve 8 may be fully closed at the same time when the idling stop condition is satisfied.

  During the automatic stop of the diesel engine 40, the detection condition pressure detection sensor 62 maintains the detection rail pressure Psensor at the first threshold value Prail_thr1 or more and the flow rate control valve 8 is closed. When establishment is detected, the flow control valve control unit 73 maintains the flow control valve 8 in a closed state even after the diesel engine 40 is restarted.

  Thus, by delaying the fuel supply start timing to the pressurizing chamber 5a of the high-pressure pump 5 when the diesel engine 40 is restarted, the detected rail pressure Psensor is set to the first threshold value Prail_thr1 by the fuel injection from the fuel injection valve 13. The fuel is not supplied to the pressurizing chamber 5a until the pressure falls below, and a large force is not required to raise the plunger 7. Therefore, it is possible to avoid applying a great load to the drive system of the high-pressure pump 5 while the oil film at the contact portion between the cam 15 and the roller 54 of the tappet structure 58 is insufficient.

  When the detected rail pressure Psensor falls below the first threshold value Prail_thr1, the lubricating fuel penetrates into the contact portion between the cam 15 and the roller 54 of the tappet structure 58 with the rotation of the high-pressure pump 5, and the oil film Is formed. Therefore, the fuel supply to the pressurizing chamber 5a is started after the oil film at the contact portion is in a sufficient state.

  In the case of the control device 60 of the present embodiment, after the diesel engine 40 is restarted, when the detected rail pressure Psensor falls below the second threshold value Prail_thr2 that is slightly larger than the first threshold value Prail_thr1, Fuel supply to the pressure chamber 5a is started. The second threshold value Prail_thr2 is set so that the detected rail pressure Psensor is the first threshold value during the delay time in consideration of the delay time from when the flow control valve 8 is opened until the pressurized chamber 5a is filled with fuel. It is set to a value that is assumed to be Prail_thr1 or less. Therefore, compared with the case where the flow rate control valve 8 is opened after the detected rail pressure Psensor is actually less than or equal to the first threshold value Prail_thr1, the power consumption can be reduced and the fuel to the pressurizing chamber 5a can be reduced. It is possible to return to the normal rail pressure control mode at an early stage because the supply start time is earlier.

  In addition, after the restart of the diesel engine 40, the fuel supply start timing to the pressurizing chamber 5a of the high-pressure pump 5 is not limited to the method of determining using the second threshold value Prail_thr2 as described above, but after the start of fuel injection. The maximum time that the rail pressure is assumed to be equal to or lower than the second threshold value Prail_thr2 can be set in advance.

3. Specific Flow of Control of Internal Combustion Engine Next, an example of control of the diesel engine 40 executed by the control device 60 of the internal combustion engine described above will be described based on the time charts of FIGS. 4 and 5 and the control flow of FIG. I will explain it. The time charts of FIGS. 4 and 5 show changes over time in engine speed Ne, actual rail pressure Pact, and flow control valve 8 during idling stop control. FIG. 4 shows that the diesel engine 40 is being automatically stopped. FIG. 5 shows an example in which the diesel engine 40 is restarted while the rail pressure Pact is maintained at the first threshold value Prail_thr1 or more, and FIG. 5 shows that the rail pressure Pact is the first threshold value during the automatic stop of the diesel engine 40. An example in the case of falling below Prail_thr1 is shown.

  In the control flow of FIG. 6, in step S11 after the start, it is determined whether or not a predetermined idling stop condition is satisfied (period t0 to t1 in FIGS. 4 and 5). When the idling stop condition is satisfied, the process proceeds to step S12, the fuel injection by the fuel injection valve 13 is stopped to stop the diesel engine 40, and the energization of the holding current A1 to the pressure control valve 12 is started in step S13 (FIG. 4 and FIG. 4). T1 in FIG.

  Next, in step S14, the rotational speed Ne of the diesel engine 40 is read, and it is determined whether or not the rotational speed Ne has become zero. This step S14 is repeated until the rotational speed Ne of the diesel engine 40 becomes zero (period t1 to t2 in FIGS. 4 and 5), and when the rotational speed Ne becomes zero (t2 in FIGS. 4 and 5). In step S15, the detected rail pressure Psensor is read, and it is determined whether the detected rail pressure Psensor is equal to or higher than the first threshold value Prail_thr1 (period t2 to t3 in FIG. 4 and t2 to t3 in FIG. 5). 'Period).

  If the detected rail pressure Psensor is equal to or higher than the first threshold value Prail_thr1, the process proceeds to step S16, and even if the predetermined restart condition is satisfied and the high-pressure pump 5 starts moving, the drive system of the high-pressure pump 5 is greatly increased. The flow rate control valve 8 is closed so that a heavy load is not applied. Next, in step S17, it is determined whether or not a predetermined restart condition is satisfied. If not satisfied, the process returns to step S15 and the comparison between the detected rail pressure Psensor and the first threshold value Prail_thr1 is repeated (t2 in FIG. 4). ~ T3 period). On the other hand, when the restart condition is satisfied, the process proceeds to step S18 to restart the fuel injection from the fuel injection valve 13 and restart the diesel engine 40 (t3 in FIG. 4).

  After the diesel engine 40 is restarted, the detected rail pressure Psensor is read in step S19 and it is determined whether or not the detected rail pressure Psensor is equal to or lower than the second threshold value Prail_thr2 (period t3 to t4 in FIG. 4). ). When the rail pressure decreases with fuel injection from the fuel injection valve and the detected rail pressure Psensor becomes equal to or lower than the second threshold value Prail_thr2, the control for closing the flow control valve 8 is canceled in step S20, and normal rail pressure control is performed. The mode is changed (t4 in FIG. 4).

  On the other hand, if the detected rail pressure Psensor is less than the first threshold value Prail_thr1 in step S15, the drive system of the high-pressure pump 5 is activated even when the predetermined restart condition is satisfied and the high-pressure pump 5 starts to move. Since a large load is not applied, the process proceeds to step S21, the flow control valve 8 is opened (t3 ′ in FIG. 5), and the process waits until the restart condition is satisfied in step S22 ( (Period from t3 ′ to t4 ′ in FIG. 5). When the restart condition is satisfied, the routine proceeds to step S23, where the fuel injection from the fuel injection valve 13 is restarted and the diesel engine 40 is restarted (t4 'in FIG. 5).

  According to the control executed when the diesel engine 40 is restarted from the automatic stop state as described above, the fuel is supplied to the pressurizing chamber 5a of the high pressure pump 5 when the rail pressure is relatively high at the time of restart. It is avoided that the start time is delayed and a large load is applied to the drive system of the high-pressure pump 5. Therefore, a decrease in durability of the high pressure pump can be suppressed.

4). Application Example In the control device 60 for an internal combustion engine of the embodiment described so far, the detected rail pressure Psensor and the first threshold value Prail_thr1 are continuously compared immediately after the diesel engine 40 is automatically stopped by the idling stop control. As long as the detected rail pressure Psensor is equal to or higher than the first threshold value Prail_thr1, the flow rate control valve 8 is controlled to be fully closed. Instead of such control, the flow control valve 8 is fully opened until the restart condition is satisfied, and the detected rail pressure Psensor read when the restart condition is satisfied is equal to or higher than the first threshold value Prail_thr1. Whether or not the flow control valve 8 is closed for a predetermined time when the diesel engine 40 is restarted may be determined.

  Further, the control device 60 is configured so that the rotational speed of the diesel engine 40 can be detected by using the rotational speed sensor provided in the diesel engine 40, and pressurization is performed so that the rotational speed of the diesel engine 40 becomes equal to or higher than a predetermined threshold value. It may be a condition for starting the fuel supply to the chamber 5a. Even when the fuel supply start condition is set as described above, the rotation of the cam 15 causes the lubricating oil to permeate into the contact portion between the cam 15 and the roller 54 to form an oil film. Even when a load is applied, a decrease in durability of the high-pressure pump 5 can be reduced.

Further, in the above-described embodiment, the fuel injection valve is not provided with a fuel leak passage other than the fuel used for back pressure control, and the pressure accumulation is configured such that the rail pressure is not easily lowered when the diesel engine 40 is automatically stopped. Although the example using the fuel injection device 50 has been described, the present invention is not limited to the case where such a pressure accumulation fuel injection device 50 is used.
Even when the fuel injection valve has a leak passage for fuel other than the fuel used for back pressure control and the rail pressure is reduced when the diesel engine automatically stops, the pressure accumulation type fuel injection device is used. When the rail pressure is relatively high at the time of restart, delaying the fuel supply start timing to the pressurizing chamber of the high-pressure pump ensures the restartability of the diesel engine while moving to the drive system of the high-pressure pump. Can be reduced.

1: Fuel tank, 2: Low pressure pump, 5: High pressure pump, 5a: Pressurization chamber, 6: Fuel intake valve, 7: Plunger, 8: Flow control valve, 9: Fuel discharge valve, 10: Common rail, 12: Pressure Control valve, 13: fuel injection valve, 14: pressure regulating valve (overflow valve), 15: cam, 16: cam chamber, 18a and 18b: low pressure fuel passage, 21: pressure sensor, 30a, 30b and 30c: return passage, 37:39: high pressure fuel passage, 40: internal combustion engine (diesel engine), 50: accumulator fuel injection device, 51: pump housing, 52: cylinder head, 52a: cylinder, 52b: fuel discharge passage, 55: spring, 58 : Tappet structure, 59: spring seat, 60: control device, 61: idling stop condition establishment detection unit, 62: restart condition establishment detection unit, 63: Id ring stop control unit, 65: target rail pressure calculating unit, 67: rail pressure detector, 69: rail pressure determination section, 71: fuel injection valve control unit, 73: flow control valve control unit, 75: pressure control valve control unit

Claims (6)

An internal combustion engine includes a common rail connected to a fuel injection valve, a high-pressure pump that pumps fuel to the common rail, and a flow rate control valve that adjusts the flow rate of fuel supplied to the high-pressure pump. In a control device for controlling an internal combustion engine capable of performing idling stop control,
An idling stop condition establishment detection unit that detects that a predetermined idling stop condition is established and outputs an instruction to automatically stop the internal combustion engine;
A restart condition establishment detection unit that detects that a predetermined restart condition is established during automatic stop of the internal combustion engine and outputs an instruction to restart the internal combustion engine;
A rail pressure detector for detecting the pressure in the common rail;
A flow rate control valve that closes the flow rate control valve for a predetermined time after the restart of the internal combustion engine when the pressure in the common rail is equal to or greater than a predetermined first threshold when the internal combustion engine is restarted. A control unit;
A control device for an internal combustion engine, comprising:   2. The control apparatus for an internal combustion engine according to claim 1, wherein the first threshold value is a value based on an allowable load from the high pressure pump to a drive system of the high pressure pump.   The flow control valve control unit maintains the flow control valve in a closed state when the internal combustion engine is automatically stopped, and the pressure in the common rail falls below the first threshold value during the automatic stop of the internal combustion engine. 3. The control device for an internal combustion engine according to claim 1, wherein the flow control valve is sometimes opened.   The flow rate control valve control unit maintains the flow rate control valve in an open state when the internal combustion engine is automatically stopped, and when the predetermined restart condition is satisfied, the pressure of the common rail is equal to or higher than the first threshold value. 3. The control apparatus for an internal combustion engine according to claim 1, wherein the flow control valve is closed when the determination is made.   After the internal combustion engine is restarted, the flow control valve control unit is configured such that the pressure in the common rail is greater than the first threshold value, and the pressure in the common rail is quickly increased by fuel injection from the fuel injection valve. The control device for an internal combustion engine according to any one of claims 1 to 4, wherein the flow rate control valve is opened when the flow rate control valve is less than or equal to a second threshold value that is less than the first threshold value.   5. The flow rate control valve control unit opens the flow rate control valve when the number of revolutions of the internal combustion engine becomes equal to or higher than a predetermined threshold after restarting the internal combustion engine. The control apparatus for an internal combustion engine according to claim 1.

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