JP2008215101A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the injection pressure of fuel by an injector high in a fuel injection device without adding an inexpensive device or a member. <P>SOLUTION: An ECU of the fuel injection device performs a temporary valve closing operation for displacing a needle in the opening direction of an injection hole after displacing it temporarily in the closing direction in one injection stroke from when the needle opens the injection hole from a fully closed state until the needle closes the injection hole. Pressure waves generated accompanying opening of the injection hole can be used by the temporary valve closing operation mainly comprising operation of an existing needle. Thereby, in the fuel injection device, the injection pressure of fuel by the injector can be made high without adding an expensive device or a member by only alternating a control flow. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel injection device that injects and supplies fuel to an engine.

  2. Description of the Related Art Conventionally, a fuel injection device includes an injector that opens a nozzle hole with a needle and injects fuel, and a control unit that gives a command to an actuator that lifts the needle and controls injection of fuel by the injector. In recent years, with the increasing demand for reduction of black smoke and the like, the fuel injection pressure by the injector is also increased in the fuel injection device, and various technical studies have been conducted to achieve further higher pressure.

  For example, an injector is equipped with a pressure-increasing mechanism that boosts fuel according to Pascal's principle, and a fuel injection device that increases the injection pressure by an injector having this pressure-increasing mechanism (see, for example, Patent Document 1), fuel supply such as a common rail A fuel injection device that includes a valve device that opens and closes a fuel supply flow path from a source to an injector, and that uses this pressure device to increase the injection pressure by using a pressure wave generated when the nozzle hole is opened and closed (for example, Patent Documents) 2), a fuel injection device that equips an injector with a dynamic pressure piston that moves due to a decrease in fuel pressure accompanying opening of the nozzle hole and increases the fuel, and increases the injection pressure with the injector having the dynamic pressure piston (for example, Patent Document 3) is disclosed.

However, the fuel injection device described in Patent Document 1 needs to be provided with a pressure increasing mechanism in the injector, the fuel injection device described in Patent Document 2 needs to include a valve device, and the fuel injection device described in Patent Document 3 The device needs to equip the injector with a dynamic pressure piston. Therefore, the fuel injection devices described in Patent Documents 1 to 3 all require expensive equipment and members and are expensive.
JP 2002-539372 A JP 2006-170153 A JP 2000-130293 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to increase the fuel injection pressure by the injector without adding expensive equipment or members in the fuel injection device. is there.

[Means of Claim 1]
The fuel injection device according to claim 1, which injects and supplies fuel to the engine, gives a command to an injector that opens a nozzle hole by a needle and injects the fuel, and an actuator that lifts the needle, Control means for controlling fuel injection by the injector. The control means performs a temporary valve closing operation in which the needle is temporarily displaced in the closing direction and then displaced in the opening direction in one injection stroke until the needle is opened from the fully closed state to the closed state.

  Thereby, the pressure wave generated with the opening and closing of the nozzle hole can be used by a temporary valve closing operation with the existing needle as the main operation. For this reason, in the fuel injection device, the fuel injection pressure by the injector can be increased only by modifying the control means without adding expensive equipment and members.

[Means of claim 2]
According to the fuel injection device of the second aspect, the needle is displaced in the closing direction from the first lift position on the open side with respect to the fully closed position by the temporary valve closing operation, and is opened on the open side with respect to the fully closed position. The second lift position that is closer to the first lift position is reached, and then the second lift position is displaced in the opening direction.

[Means of claim 3]
According to the fuel injection device of the third aspect, the injector forms a back pressure chamber that applies fuel pressure to the needle in the closing direction, and a nozzle chamber through which the fuel injected through the injection hole flows in and out. The means operates the flow of fuel into and out of the back pressure chamber according to a command to the actuator, thereby increasing or decreasing the fuel pressure in the back pressure chamber to displace the needle in the closing direction or the opening direction. The temporary valve closing operation is performed by temporarily increasing the fuel pressure in the back pressure chamber and then decreasing it.

[Means of claim 4]
According to the fuel injection device of the fourth aspect, the control means temporarily closes the valve when the pressure reduction wave of the fuel pressure in the nozzle chamber caused by opening of the nozzle hole is reflected at the free end to reach the nozzle chamber. Perform the operation.

[Means of claim 5]
The fuel injection device according to claim 5 is disposed in a common rail that accumulates fuel in a high pressure state and distributes the fuel to the injector, and a fuel passage that guides the fuel from the common rail to the nozzle chamber, and detects the fuel pressure in the fuel passage. And a fuel pressure detecting means. Then, the control means determines the timing for performing the temporary valve closing operation based on the detection value obtained from the fuel pressure detection means.
As a result, the control means can accurately grasp when the pressure wave generated in the nozzle chamber returns to the nozzle chamber, so that the valve closing operation can be performed more effectively.

[Means of claim 6]
According to the fuel injection device of the sixth aspect, the control means calculates the required amount of fuel to be injected by the injector in one injection stroke according to the operating state of the engine, and temporarily closes the valve in one injection stroke. The number of times to perform is determined according to the required amount of fuel.
As the required amount of fuel increases, the time required for one injection stroke becomes longer. Therefore, the number of times the pressure wave reciprocates between a fuel supply source such as a common rail and the injector per injection stroke increases. Therefore, by determining the number of times that the temporary valve closing operation is performed in one injection stroke according to the required amount of fuel, the pressure wave can be effectively used without being attenuated unnecessarily.

[Means of Claim 7]
According to the fuel injection device of the seventh aspect, the nozzle hole is closed when the seat portion provided at the tip of the needle is seated at a predetermined seating position. The displacement in the closing direction due to the temporary valve closing operation is such that the flow path cross-sectional area formed between the seat part and the seating position (referred to as the seat part opening area) (Referred to as an area).
If the seat opening area is smaller than the total cross-sectional area of the nozzle hole, the pressure loss due to the fuel passing through the part that forms the seat opening area increases, and the effect of high pressure by the temporary closing operation is greatly reduced. End up. Therefore, by performing the displacement in the closing direction in a range where the seat opening area is equal to or larger than the total nozzle hole cross-sectional area, it is possible to prevent the high pressure effect due to the temporary valve closing operation from being reduced.

  The fuel injection device of the best mode 1 is to inject and supply fuel to an engine. The injector opens a nozzle hole with a needle and injects the fuel, and gives an instruction to an actuator that lifts the needle. And control means for controlling the fuel injection. Then, the control means performs a temporary valve closing operation in which the needle is temporarily displaced in the closing direction and then displaced in the opening direction in one injection stroke until the needle is opened from the fully closed state to the closed state.

  Here, the needle is displaced in the closing direction from the first lift position on the open side with respect to the fully closed position by the temporary valve closing operation, so that the needle is open on the open side with respect to the fully closed position and on the close side with respect to the first lift position. The second lift position is reached, and then the second lift position is displaced in the opening direction.

The injector forms a back pressure chamber that applies fuel pressure to the needle in a closing direction, and a nozzle chamber through which fuel injected through the injection hole flows in and out. By operating the flow of fuel into and out of the valve, the fuel pressure in the back pressure chamber is increased or decreased to displace the needle in the closing direction or the opening direction. The temporary valve closing operation is performed by temporarily increasing the fuel pressure in the back pressure chamber and then decreasing it.
Further, the control means performs a temporary valve closing operation when the pressure reduction wave of the fuel pressure in the nozzle chamber generated by opening the nozzle hole is reflected at the free end to become a pressure increase wave and reach the nozzle chamber.

  In addition, this fuel injection device is arranged in a common rail that accumulates fuel in a high pressure state and distributes the fuel to the injector, and a fuel passage that leads to the fuel from the common rail to the nozzle chamber, and detects the fuel pressure in the fuel passage. Means. Then, the control means determines the timing for performing the temporary valve closing operation based on the detection value obtained from the fuel pressure detection means.

Further, the control means calculates the required amount of fuel to be injected by the injector in one injection stroke according to the operating state of the engine, and determines the number of times that the temporary valve closing operation is performed in one injection stroke according to the required amount of fuel. Decide.
Further, the nozzle hole is closed by seating a seat portion provided at the tip of the needle at a predetermined seating position. And the displacement of the closing direction by temporary valve closing operation is performed in the range from which a seat part opening area becomes more than a nozzle hole total cross-sectional area.

[Configuration of Example 1]
The configuration of the fuel injection device 1 according to the first embodiment will be described with reference to FIG.
The fuel injection device 1 injects and supplies fuel to an engine (not shown). The injector 3 opens the injection hole 2a with the needle 2 and injects the fuel, and the actuator 4 of the injector 3 is instructed. And an electronic control unit (referred to as ECU) 5 as a control means for controlling fuel injection by the injector 3.

  The injector 3 is mounted on an engine, for example, receives fuel distribution from a common rail 8 that accumulates fuel in a high pressure state, and injects fuel distributed from the common rail 8 into a cylinder of the engine. The common rail 8 is supplied with fuel pressurized by a supply pump (not shown), and the pressure of the fuel accumulated in the common rail 8 (referred to as common rail pressure) is detected by a rail pressure sensor 9 and the rail pressure is detected. The detected value is output to the ECU 5.

  The injector 3 includes a needle 2 that opens and closes the nozzle hole 2a, and an electromagnetic two-way valve as an actuator 4 that generates a driving force for lifting the needle 2 in the opening direction (hereinafter, the actuator 4 is referred to as this electromagnetic two-way valve. (Referred to as an electromagnetic valve 4), and a spring 11 for urging the needle 2 in the closing direction. A nozzle chamber 11a through which fuel injected through the injection hole 2a flows in and out is formed on the tip side of the needle 2, and the fuel pressure in the nozzle chamber 11a urges the needle 2 in the opening direction. Further, a back pressure chamber 12 is formed on the rear end side of the needle 2, and the fuel pressure (referred to as back pressure) in the back pressure chamber 12 biases the needle 2 in the closing direction.

  A fuel flow path 14 for receiving fuel from the common rail 8 is connected to the nozzle chamber 11a, and the nozzle chamber 11a is always in communication with the common rail 8 through the fuel flow path 14. A fuel flow path 15 branched from the fuel flow path 14 and a fuel flow path 17 leading to the fuel tank 16 are connected to the back pressure chamber 12. The fuel flow paths 15 and 17 have throttles 18 and 19, respectively. Is provided.

  The fuel flow path 14 is provided with a fuel pressure sensor 19a as a fuel pressure detection means for detecting the fuel pressure, and the detected value of the fuel pressure in the fuel flow path 14 is output to the ECU 5. Further, the electromagnetic valve 4 is disposed in the fuel flow path 17, and the fuel flow path 17 is opened and closed by the electromagnetic valve 4. Further, a fuel temperature sensor 20 is disposed in the fuel flow path 17 to detect the temperature of the fuel flowing through the fuel flow path 17, and the detected value of this temperature is output to the ECU 5.

  Here, the solenoid valve 4 is arranged so as to open the fuel flow path 17 when energized and close the fuel flow path 17 when de-energized, and the throttles 18 and 19 The flow rate of the fuel flowing out from the back pressure chamber 12 through the passage 17 is provided to be larger than the flow rate of the fuel flowing into the back pressure chamber 12 through the fuel flow path 15.

As a result, when energization to the solenoid valve 4 is turned on, the amount of fuel outflow from the back pressure chamber 12 increases and the back pressure decreases. Therefore, the urging force acting on the needle 2 in the closing direction (mainly the resultant force of the urging force due to the back pressure and the urging force due to the spring 11) acts in the opening direction (mainly the fuel in the nozzle chamber 11a). And the needle 2 is driven in the opening direction. As a result, the nozzle hole 2a is opened, and fuel is injected at an injection pressure equivalent to the fuel pressure in the nozzle chamber 11a.
The nozzle hole 2 a is closed when the seat portion 24 provided at the tip of the needle 2 is seated at a predetermined seating position 28, and is opened when the seat portion 24 is separated from the seating position 28.

  When the energization of the solenoid valve 4 is turned off, the fuel outflow from the back pressure chamber 12 stops and the back pressure increases. For this reason, the urging force acting on the needle 2 in the closing direction becomes stronger than the urging force acting on the opening direction, and the needle 2 is driven in the closing direction. As a result, the nozzle hole 2a is closed, and fuel injection ends.

  The ECU 5 is a well-known microcomputer including a storage device such as a CPU, ROM, and RAM, an input device, an output device, and the like that perform a control function and an arithmetic function. The ECU 5 receives input of detection values from various sensors indicating the operating state of the engine such as the rail pressure sensor 9, the fuel pressure sensor 19a, and the fuel temperature sensor 20, and energizes the electromagnetic valve 4 based on these detection values. Various command values for turning on and off are calculated. Then, the ECU 5 performs output based on the calculated command value, and turns on / off the energization of the electromagnetic valve 4.

  That is, the ECU 5 controls the injection by operating the fuel flow into and out of the back pressure chamber 12 according to a command to the electromagnetic valve 4 to increase or decrease the back pressure to displace the needle 2 in the closing direction or the opening direction. That is, the ECU 5 performs injection by the injector 3 based on various detection values, when to start the injection by the injector 3 (when the needle 2 opens the injection hole 2a from the fully closed state: the injection start timing Tinj), and The required amount of fuel (referred to as the required injection amount) is calculated. The required injection amount is a required amount of fuel to be injected in one injection stroke until the needle 2 opens the injection hole 2a from the fully closed state and then closes.

  Then, the ECU 5 finishes one injection stroke from the energization start timing Ton and the energization start timing Ton based on the injection start timing Tinj, the required injection amount, and the like. A period (referred to as a total energization period Tq) until the time of stopping energization is calculated. Then, the ECU 5 performs output based on the energization start timing Ton and the total energization period Tq, turns on / off the energization of the electromagnetic valve 4, and controls the injection by the injector 3.

  Here, there is a time delay between the start of injection by the injector 3 and the start of energization of the solenoid valve 4 and between the stop of injection and the stop of energization (the delay between the start of injection and the start of energization, (Injection start delay τd, and the delay between the injection stop and energization stop is the injection stop delay τc). The injection start delay τd and the injection stop delay τc vary mainly according to the common rail pressure. Therefore, the ECU 5 calculates the injection start delay τd and the injection stop delay τc based on the detection values obtained from the rail pressure sensor 9, calculates the energization start timing Ton taking into account the injection start delay τd, and the injection stop delay τc. Is added to calculate the total energization period Tq.

  The term “injection stop” means “the needle 2 starts displacement in the closing direction to close the nozzle hole 2a”. The end of one injection stroke is not when the injection is stopped, but when the nozzle hole 2a is closed and fully closed, and fuel is no longer injected.

  Further, the ECU 5 performs a temporary valve closing operation for displacing the needle 2 in the opening direction after temporarily displacing the needle 2 in the closing direction in one injection stroke. That is, the ECU 5 temporarily stops energization to the solenoid valve 4 until the total energization period Tq elapses from the energization start timing Ton, and then starts energization again. That is, the ECU 5 temporarily closes the fuel flow path 17 to increase the back pressure, and then opens the fuel flow path 17 again to decrease the back pressure to perform a temporary valve closing operation.

  This temporary valve closing operation is performed in order to increase the fuel injection pressure using the pressure wave generated when the nozzle hole 2a is opened and closed. That is, by opening the nozzle hole 2a from the fully closed state, a pressure wave is generated in the fuel pressure in the nozzle chamber 11a. Then, the ECU 5 performs a temporary valve closing operation when the pressure wave reflected by the free end (referred to as a reflected pressure wave) propagates to the nozzle chamber 11 a through the fuel flow path 14. Thereby, the reflected pressure wave is amplified in the nozzle chamber 11a, and the fuel pressure (that is, the injection pressure) in the nozzle chamber 11a is increased.

  Here, the ECU 5 determines the timing for performing the temporary closing operation based on the detected value of the fuel pressure in the fuel flow path 14 obtained from the fuel pressure sensor 19a. That is, the ECU 5 directly grasps the time when the pressure wave or the reflected pressure wave passes through the detection portion by the fuel pressure sensor 19a, and determines the time when the temporary valve closing operation is performed based on this passage time.

  Further, the ECU 5 determines the number of times of performing the temporary valve closing operation in one injection stroke according to the required injection amount (specifically, according to the total energization period Tq calculated based on the required injection amount). That is, a pressure wave is generated even when the needle 2 is displaced in the opening direction by the temporary valve closing operation. Therefore, in order to effectively use such a pressure wave, the number of times of performing the temporary valve closing operation depends on the required injection amount. Decide. In addition, ECU5 can also determine the frequency | count of performing a temporary valve closing operation to zero based on the value of the total energization period Tq. That is, the ECU 5 can end the injection without performing the temporary closing operation when the required injection amount is small and the total energization period Tq is short.

  Here, the needle 2 is displaced in the closing direction from the first lift position on the open side with respect to the fully closed position by the temporary valve closing operation, so that the needle 2 is on the open side with respect to the fully closed position and on the close side with respect to the first lift position. The second lift position is reached, and then the second lift position is displaced in the opening direction (see FIG. 2). The displacement in the closing direction due to the temporary valve closing operation is such that the flow path cross-sectional area formed between the seat part 24 and the seating position 28 (referred to as the seat part opening area) (Refer to FIG. 2).

That is, if the displacement amount of the needle 2 when the seat portion opening area and the nozzle hole total cross-sectional area are equal is the defined lift HL, the displacement amount of the needle 2 is smaller than the defined lift HL (that is, the seat portion opening area). Is smaller than the total nozzle hole cross-sectional area), the pressure loss when the fuel passes between the seat portion 24 and the seating position 28 increases, and the effect of increasing the pressure by the temporary closing operation is greatly reduced. End up. Therefore, the ECU 5 sets a displacement amount of the needle 2 to be larger than the specified lift HL during a period in which energization to the solenoid valve 4 is temporarily stopped in the temporary closing operation (a temporary closing operation period Tint). calculate.
Hereinafter, a control method for performing the temporary valve closing operation will be described in detail.

[Control Method of Example 1]
A control method of the fuel injection device 1 according to the first embodiment will be described with reference to the flowchart of FIG.
First, in step S1, the injection start timing Tinj and the required injection amount are calculated based on various detection values. In step S2, the injection start delay τd and the injection stop delay τc are calculated based on the detection values obtained from the rail pressure sensor 9. calculate. In step S3, the energization start timing Ton and the total energization period Tq are calculated based on the injection start timing Tinj, the required injection amount, the injection start delay τd, the injection stop delay τc, and the like.

  Next, in step S4, it is determined whether or not the time has reached the energization start timing Ton. If the time has reached the energization start timing Ton (YES), the process proceeds to step S5 to start energization of the solenoid valve 4. If the time is not the energization start timing Ton (NO), the system waits until the energization start timing Ton is reached.

  Next, in step S6, it is determined whether or not the time has reached the injection start timing Tinj. If the time has reached the injection start timing Tinj (YES), the process proceeds to step S7 to calculate the pressure wave reciprocation time Tr. If the injection start timing Tinj is not reached (NO), the system waits until the injection start timing Tinj is reached.

  Here, the pressure wave reciprocation time Tr means that after a pressure wave is generated in the nozzle chamber 11a (that is, after the needle 2 opens the nozzle hole 2a from the fully closed state), the pressure wave is freed by the common rail 8 at the free end. This is the time required for reflection to become a reflected pressure wave and for the reflected pressure wave to propagate to the nozzle chamber 11a. The pressure wave reciprocation time Tr is calculated by dividing the reciprocating distance between the nozzle chamber 11a and the common rail 8 (that is, twice the distance of the fuel flow path 14) by the sonic velocity, and the sonic velocity is calculated by the rail pressure sensor. 9 and the detection value from the fuel temperature sensor 20 are calculated.

Next, in step S8, it is determined whether or not the remaining injection period is longer than the pressure wave reciprocation time Tr. If the remaining injection period is longer than the pressure wave reciprocation time Tr (YES), the process proceeds to step S9 and the remaining injection is performed. If the period is not longer than the pressure wave reciprocation time Tr (NO), the process proceeds to step S15.
Here, the remaining injection period is a period from the present time to the injection stop timing (that is, the timing at which the needle 2 starts displacement in the closing direction to close the nozzle hole 2a).

  That is, in step S8, it is determined whether or not the injection continues until a time when the reflected pressure wave can be used to increase the injection pressure. Then, if it is determined that the injection continues until the time when the reflected pressure wave can be used, the process proceeds to step S9 to step S14, the temporary valve closing operation is executed, and if it is determined that the injection does not continue until the time when the reflected pressure wave can be used. Then, the process proceeds to steps S15 and S16 to end the injection.

  Steps S7 to S14 are steps in which the number of processes increases with the number of times that the temporary valve closing operation is performed. When the process in step S8 is the first time, the present time is the injection start timing Tinj, and the remaining injection period is Tq−τd + τc.

In step S9, a time delay between the stop of energization in the temporary valve closing operation and the start of displacement of the needle 2 in the closing direction (referred to as a temporary valve closing delay τcint), the restart of energization in the temporary valve closing operation, and the needle 2 A time delay from the start of displacement in the opening direction (restart valve delay τdint) is calculated. The temporary valve closing delay τcint and the restart valve delay τdint are also calculated based on the detected value from the rail pressure sensor 9.
In step S10, an energization stop timing (temporary valve closing operation start timing Toff ′) for the temporary valve closing operation and a temporary valve closing operation period Tint are calculated.

  Here, the temporary valve closing operation start timing Toff ′ is calculated based on the pressure wave reciprocating time Tr, the temporary valve closing delay τcint, and the like, and the temporary valve closing operation period Tint is the restart valve delay τdint, the specified lift HL, the rail pressure, and the like. It is calculated based on the detection value of the sensor 9 and the like. Note that the pressure wave reciprocation time Tr used for calculating the temporary valve closing operation start timing Toff 'is a value recalculated based on the detected value from the fuel pressure sensor 19a. That is, the pressure wave reciprocation time Tr is recalculated based on the time when the pressure wave or the reflected pressure wave passes through the detection site by the fuel pressure sensor 19a, and the valve closing operation is temporarily performed using the recalculated pressure wave reciprocation time Tr. The start time Toff ′ is calculated.

  Further, the displacement speed in the closing direction of the needle 2 necessary for calculating the temporary valve closing operation period Tint mainly varies depending on the common rail pressure, and is thus calculated based on the detected value of the rail pressure sensor 9. Furthermore, in order to prevent the increase in the high pressure effect due to the temporary closing operation, the temporary closing operation period Tint is calculated so that the displacement amount of the needle 2 does not become smaller than the specified lift HL.

  In step S11, it is determined whether or not the time has reached the temporary valve closing operation start timing Toff '. If the time has reached the temporary valve closing operation start timing Toff' (YES), the process proceeds to step S12 and the electromagnetic valve 4 is moved. If the time is not the temporary valve closing operation start timing Toff ′ (NO), the system waits until the temporary valve closing operation start timing Toff ′ is reached.

  Next, in step S13, it is determined whether or not the time has elapsed from the temporary valve closing operation start timing Toff 'by the temporary valve closing operation period Tint. If the temporary valve closing operation period Tint has elapsed from the temporary valve closing operation start timing Toff '(YES), the process proceeds to step S14, energization of the electromagnetic valve 4 is resumed, the process returns to step S7, and has elapsed. If not (NO), the process waits until it elapses.

  In step S15, it is determined whether or not the time has elapsed from the energization start timing Ton by the total energization period Tq. That is, in step S15, it is determined whether or not one injection stroke is completed. If the time has elapsed from the energization start timing Ton by the total energization period Tq (YES), the process proceeds to step S16 and the solenoid valve 4 is reached. If the current is not passed (NO), the system waits until the current has passed.

[Operation of Example 1]
The operation of the fuel injection device 1 according to the first embodiment will be described with reference to the time chart of FIG.
First, when the time reaches the energization start timing Ton, energization to the solenoid valve 4 is started, and when the time reaches the injection start timing Tinj, the needle 2 starts to be displaced in the opening direction and opens the nozzle hole 2a from the fully closed state. The injection start timing Tinj is delayed from the energization start timing Ton by the injection start delay τd.

  When the needle 2 opens the nozzle hole 2a from the fully closed state, the fuel pressure (that is, the injection pressure) in the nozzle chamber 11a suddenly drops and then rises and stabilizes. That is, the pressure wave generated in the nozzle chamber 11a due to the opening of the nozzle hole 2a is in the form of a decompression wave, and this decompression wave propagates toward the common rail 8 using the fuel flowing through the fuel flow path 14 as a medium.

  This decompression wave is reflected at the common rail 8 at the free end, changed into a sudden sudden rise and a sudden drop following the sudden rise, and reflected and propagated toward the nozzle chamber 11a using the fuel flowing through the fuel flow path 14 as a medium. . In other words, the reflected pressure wave is in the form of a boosted wave due to free end reflection at the common rail 8, and this boosted wave enters the nozzle chamber 11a at a time that approximately coincides with the time when the pressure wave reciprocation time Tr has elapsed from the injection start timing Tinj. Propagate.

  On the other hand, a temporary valve closing operation start timing Toff ′ is calculated as a time at which the temporary valve closing operation is started (that is, a time at which energization to the electromagnetic valve 4 is stopped). It is calculated as a time before the temporary valve closing delay τcint from the time when the boost wave propagates to the nozzle chamber 11a. For this reason, energization to the solenoid valve 4 is stopped before the time when the injection pressure starts to increase due to the boost wave.

  As a result, the needle 2 starts to be displaced in the closing direction almost simultaneously with the pressure wave being propagated to the nozzle chamber 11a and the injection pressure starting to rise. The boost wave is amplified more than the decompression wave generated at the injection start timing Tinj, and the injection pressure is increased. In addition, the injection rate is temporarily increased by increasing the injection pressure.

  Then, when the time has elapsed from the temporary valve closing operation start timing Toff ′ by the time of the temporary valve closing operation period Tint, the energization to the electromagnetic valve 4 is resumed, and the needle 2 is displaced in the opening direction with a delay of the restart valve delay τdint from the resumption of energization. start. In the temporary valve closing operation, the displacement amount of the needle 2 does not become smaller than the specified lift HL.

  Eventually, when the time elapses from the energization start timing Ton for the total energization period Tq, energization to the solenoid valve 4 is stopped to stop the injection, and the needle 2 is displaced in the closing direction with a delay of the injection stop delay τc from the energization stop. start.

[Effect of Example 1]
According to the fuel injection device 1 of the first embodiment, the ECU 5 temporarily displaces the needle 2 in the closing direction in one injection stroke until the needle 2 opens the nozzle hole 2a from the fully closed state and then closes. Temporarily closes the valve to be displaced in the opening direction.
Thereby, the pressure wave generated with the opening of the nozzle hole 2a can be used by the temporary valve closing operation with the existing needle 2 as the main operation. Therefore, in the fuel injection device 1, the fuel injection pressure by the injector 3 can be increased only by modifying the control flow without adding expensive equipment and members.

The fuel injection device 1 also includes a fuel pressure sensor 19a that detects the fuel pressure in the fuel flow path 14, and the ECU 5 calculates a temporary valve closing operation start timing Toff ′ based on a detection value obtained from the fuel pressure sensor 19a. The pressure wave reciprocation time Tr necessary for the calculation is recalculated.
Thereby, since ECU5 can grasp | ascertain the time when the pressure wave which generate | occur | produced in the nozzle chamber 11a returns to the nozzle chamber 11a with high precision, it can perform temporary valve closing operation more effectively.

Further, the ECU 5 calculates the required injection amount according to various detection values indicating the operating state of the engine, and calculates the number of times that the temporary valve closing operation is performed in one injection stroke based on the required injection amount and the like. It is determined according to the period Tq.
Since the total energization period Tq becomes longer as the required injection amount increases, the number of times the pressure wave reciprocates between the common rail 8 and the injector 3 per injection stroke also increases. Therefore, by determining the number of times of performing the temporary valve closing operation in one injection stroke according to the total energization period Tq, the pressure wave can be effectively used without being attenuated unnecessarily.

Further, the displacement in the closing direction due to the temporary valve closing operation is performed in a range where the seat opening area is equal to or larger than the total nozzle hole cross-sectional area.
If the seat opening area is smaller than the total cross-sectional area of the nozzle hole, the pressure loss due to the fuel passing through the part that forms the seat opening area increases, and the effect of high pressure by the temporary closing operation is greatly reduced. End up. Therefore, by performing the displacement in the closing direction in a range where the seat opening area is equal to or larger than the total nozzle hole cross-sectional area, it is possible to prevent the high pressure effect due to the temporary valve closing operation from being reduced.

[Modification]
According to the fuel injection device 1 of the first embodiment, the ECU 5 considers that a pressure wave is generated at the calculated injection start timing Tinj, and performs a temporary valve closing operation based on the injection start timing Tinj. Equipped with a needle displacement sensor that detects the amount of displacement 2 and grasps the generation time of the pressure wave based on the detection value from the needle displacement sensor, and the generation time of the pressure wave based on the detection value from the needle displacement sensor The valve closing operation may be performed based on the above. In this case, since the generation time of the pressure wave can be grasped with high accuracy, the effect of increasing the pressure by the temporary closing operation can be enhanced.

  Further, according to the fuel injection device 1 of the first embodiment, the ECU 5 equips the fuel flow path 14 with the fuel pressure sensor 19a, and recalculates the pressure wave reciprocation time Tr based on the detected value from the fuel pressure sensor 19a. The recalculated pressure wave reciprocation time Tr was used to calculate the temporary valve closing operation start timing Toff ′. However, the value of the pressure wave reciprocation time Tr before recalculation (that is, the reciprocation between the nozzle chamber 11a and the common rail 8). The temporary valve closing operation start timing Toff ′ may be calculated using a value calculated by dividing the distance by the speed of sound.

  The needle displacement sensor and the fuel pressure sensor 19a are less expensive than the pressure increasing mechanism described in Patent Document 1, the valve device described in Patent Document 2, and the dynamic pressure piston described in Patent Document 3, and the needle displacement sensor Even if the quantity sensor and the fuel pressure sensor 19a are provided, the injection pressure can be increased at a low cost.

  Further, according to the fuel injection device 1 of the first embodiment, the fuel temperature sensor 20 is disposed in the fuel flow path 17, and the speed of sound is calculated based on the temperature of the fuel flowing through the fuel flow path 17. The fuel temperature sensor 20 can be arranged at any part as long as the fuel flows in the flow paths 14 and 15.

It is explanatory drawing which shows the structure of a fuel-injection apparatus. (A) is a correlation diagram showing the correlation between the needle displacement, the seat opening area, and the total nozzle hole cross-sectional area, (b) is an explanatory diagram showing the allowable range of the needle displacement in the temporary closing operation. is there. It is a flowchart which shows the control flow of a fuel-injection apparatus. (A) is a time chart showing the transition of energization to the solenoid valve, (b) is a time chart showing the transition of the displacement amount of the needle, (c) is a time chart showing the transition of the injection pressure, (D) is a time chart which shows transition of an injection rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection apparatus 2 Needle 2a Injection hole 3 Injector 4 Electromagnetic valve (actuator)
5 ECU (control means)
8 Common rail 11a Nozzle chamber 12 Back pressure chamber 14 Fuel flow path 19a Fuel pressure sensor (fuel pressure detecting means)
24 Seat part 28 Seating position

Claims (7)

In a fuel injection device for injecting and supplying fuel to an engine,
An injector that opens a nozzle hole with a needle and injects fuel;
A control means for giving a command to an actuator for lifting the needle and controlling fuel injection by the injector;
The control means performs a temporary valve closing operation in which the needle is displaced in the opening direction after being temporarily displaced in the closing direction in one injection stroke until the needle is opened from the fully closed position to the closed position. A fuel injection device characterized in that: The fuel injection device according to claim 1,
The needle is displaced in the closing direction from the first lift position on the open side with respect to the fully closed position by the temporary valve closing operation, so that the needle is on the open side with respect to the fully closed position and on the close side with respect to the first lift position. The fuel injection device, which reaches a second lift position and is then displaced in an opening direction from the second lift position. The fuel injection device according to claim 1 or 2,
The injector forms a back pressure chamber that applies a fuel pressure to the needle in a closing direction, and a nozzle chamber into which fuel injected through the injection hole flows in and out.
The control means operates the flow of fuel into and out of the back pressure chamber according to a command to the actuator, thereby increasing or decreasing the fuel pressure in the back pressure chamber to displace the needle in the closing direction or the opening direction,
The fuel injection device according to claim 1, wherein the temporary valve closing operation is performed by temporarily increasing the fuel pressure in the back pressure chamber and then decreasing the fuel pressure. The fuel injection device according to claim 3, wherein
The control means performs the temporary valve closing operation when a reduced pressure wave of the fuel pressure in the nozzle chamber generated by opening the nozzle hole is reflected at a free end to become a boosted wave and reaches the nozzle chamber. Fuel injection device. The fuel injection device according to claim 4, wherein
A common rail that accumulates fuel in a high pressure state and distributes the fuel to the injector;
A fuel pressure detecting means arranged in a fuel flow path for guiding fuel from the common rail to the nozzle chamber and detecting a fuel pressure in the fuel flow path;
The fuel injection device according to claim 1, wherein the control means determines a timing for performing the temporary valve closing operation based on a detection value obtained from the fuel pressure detection means. The fuel injection device according to any one of claims 1 to 5,
The control means includes
Calculating a required amount of fuel to be injected by the injector in the one injection stroke according to an operating state of the engine;
The number of times that the temporary valve closing operation is performed in the one injection stroke is determined according to the required amount of the fuel. The fuel injection device according to any one of claims 1 to 6,
The nozzle hole is closed by seating a seat portion provided at the tip of the needle at a predetermined seating position,
The displacement in the closing direction by the temporary valve closing operation is performed in a range in which a flow path cross-sectional area formed between the seat portion and the seating position is equal to or larger than a flow path cross-sectional area of the nozzle hole. Fuel injection device.

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