JP2008215186A - Fuel injection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately control the injection start timing and an injection amount regardless of aged deterioration and fluctuation in characteristics of a piezostack among individuals. <P>SOLUTION: In a fuel injection system provided with a fuel injection valve 1 which forces a control valve 3 to close between a valve chamber 14 and high-pressure fuel passage 13 by charging a piezostack 41, and also forces a nozzle 2 to be opened, load generated by the piezostack 41 is detected by a load sensor 7. When the load of the piezostack 41 reaches a threshold, the control valve 3 is determined to close between the valve chamber 14 and high-pressure fuel passage 13 so that response time of the control valve 3 is calculated. Charging speed to the piezostack 41 is corrected to make the response time of the control valve 3 match a target control valve response time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel injection device for injecting fuel into an internal combustion engine.

The conventional fuel injection device controls the operation of the on-off valve of the nozzle by using a piezo stack that expands and contracts due to charge and discharge of charges (see, for example, Patent Document 1).
JP 58-152161 A

  However, in the conventional fuel injection device, the relationship between the charging voltage applied to the piezo stack (hereinafter referred to as piezo voltage) and the amount of expansion / contraction of the piezo stack varies among individuals and also changes with time. As a result, the injection start timing deviates from the target injection start timing due to individual variation, or the injection start timing changes over time due to deterioration over time, and there is a problem that the injection start timing and the injection amount cannot be accurately controlled. It was.

  SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to make it possible to control the injection start timing and the injection amount with high accuracy regardless of the variability of individual characteristics of the piezo stack and the deterioration over time.

  The present invention is configured such that by charging the piezo stack (41), the control valve (3) closes the space between the valve chamber (14) and the high-pressure fuel passage (13) to open the nozzle (2). A fuel injection device having a fuel injection valve (1), a load sensor (7) for detecting a load generated by the piezo stack (41), and a drive circuit (130 for supplying a charging current to the piezo stack (41). ), A control device (140) for controlling the operation of the drive circuit (130) by outputting a drive signal to the drive circuit (130), and charging the piezo stack (41) after starting the piezo stack (41) ) Response time calculation means (S104) for calculating the control valve response time until the load reaches the threshold value, and response time correction means (S104) for correcting the drive signal so that the control valve response time matches the target control valve response time. Characterized in that it comprises 106).

  Here, of the time from the start of charging to the piezo stack (41) to the start of injection, the control valve (3) is connected to the valve chamber (14) from the start of charging to the piezo stack (41). ) And the high-pressure fuel passage (13) is affected by the characteristics of the piezo stack (41), but the control valve (3) is connected between the valve chamber (14) and the high-pressure fuel passage (13). The time from when the interval is closed to when the injection is started is not affected by the characteristics of the piezo stack (41).

  In the present invention, when the load of the piezo stack (41) reaches a threshold value, the control valve (3) determines that the space between the valve chamber (14) and the high-pressure fuel passage (13) is closed, and the control valve response. Calculate time. Therefore, according to the present invention, the control valve response time can be made to coincide with the target control valve response time regardless of the individual variation of the characteristics of the piezo stack (41) or deterioration with time. The injection start timing and the injection amount can be accurately controlled regardless of the individual variation in characteristics and deterioration with time.

  In this case, if the charging speed for the piezo stack (41) is changed by correcting the drive signal, the control valve response time can be easily adjusted.

  By the way, when the control valve (3) is in contact with the high pressure side seat surface (34), the control valve (3) is attached in a direction away from the high pressure side seat surface (34) by the fuel pressure in the high pressure fuel passage (13). Therefore, in order to ensure that the space between the valve chamber (14) and the high pressure fuel passage (13) is closed, the control valve (3) is moved to the high pressure side seat surface (34) as the fuel pressure increases. It is necessary to press with great force.

  Therefore, by increasing the threshold value as the fuel pressure in the high pressure fuel passage (13) increases, the control valve (3) substantially closes the space between the valve chamber (14) and the high pressure fuel passage (13). The timing can be accurately detected, and thus the control valve response time can be accurately calculated.

  Further, the load of the piezo stack (41) detected by the load sensor (7) when a predetermined time has elapsed from the charging start time is defined as a first time load, and the load is applied when a predetermined time elapses after the predetermined time elapses. When the load of the piezo stack (41) detected by the sensor (7) is the second time load, it can be determined that the second time load is equal to or greater than the first time load.

  Here, the first time load corresponds to the load of the piezo stack (41) in the vicinity of the timing when the control valve (3) leaves the low pressure side seat surface (33), and the second time load is the control valve (3). Corresponds to the load of the piezo stack (41) immediately before coming into contact with the high-pressure side seat surface (34). According to this, it is possible to detect a malfunction of the control valve (3) due to an abnormality of the piezo stack (41).

  Further, if it is determined that the control valve response time is out of the allowable time range, it is possible to detect a malfunction of the control valve (3) due to an abnormality of the piezo stack (41). it can.

  Further, when the load of the piezo stack (41) detected by the load sensor (7) after the piezo stack (41) is completely charged is used as the post-charge load, the drive signal is set so that the post-charge load falls within the allowable load range. Can be corrected.

  In this way, it is possible to prevent a seal failure due to insufficient control valve pressing load on the high pressure side seat surface (34), and to control the control valve (3) or high pressure side seat surface (34 due to excessive control valve pressing load. ) Can be prevented or suppressed.

  Further, if the charge energy amount for the piezo stack (41) is changed by correcting the drive signal, the post-charge load can be easily adjusted.

  Further, if it is determined that the state is abnormal when the correction value of the charge energy amount for the piezo stack (41) is out of a predetermined allowable range, an abnormality of the piezo stack (41) can be detected. it can.

  In addition, the code | symbol in the bracket | parenthesis of each means described in a claim and this column shows the correspondence with the specific means as described in embodiment mentioned later.

  An embodiment of the present invention will be described. 1 is a cross-sectional view showing the overall configuration of a fuel injection device according to an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of a portion A in FIG. 1, and FIG. 3 is a perspective view showing a load sensor and a piezo stack in FIG. It is.

  The fuel injection device according to the present embodiment has a high pressure stored in a pressure accumulator (not shown) in which a fuel injection valve 1 is mounted on a cylinder head of a multi-cylinder internal combustion engine (more specifically, a diesel engine, not shown). The fuel is injected into the cylinder of the internal combustion engine.

  As shown in FIGS. 1 to 3, the body 1 a of the fuel injection valve 1 flows out toward the fuel tank 100, and the fuel inlet portion 11 into which the high pressure fuel from the pressure accumulator is introduced and the fuel inside the fuel injection valve 1. And a fuel outlet 12 to be operated.

  A nozzle 2 that injects fuel when the valve is opened is disposed on one end side of the body 1a in the axial direction. The nozzle 2 includes a needle 21 that is slidably held on the body 1a, a nozzle spring 22 that urges the needle 21 in a valve closing direction, and a nozzle cylinder 23 in which the piston portion 21a of the needle 21 is inserted. is doing.

  At one end in the axial direction of the body 1a, an injection hole 24 communicating with the fuel inlet 11 through the high-pressure fuel passage 13 is formed, and high-pressure fuel is injected from the injection hole 24 into the cylinder of the internal combustion engine. Yes. A tapered valve seat 25 is formed on the upstream side of the injection hole 24, and the injection hole 24 is opened and closed when the seat portion 21 b formed on the needle 21 contacts and separates from the valve seat 25.

  The piston part 21a is slidably and liquid-tightly inserted into the nozzle cylinder 23. The piston part 21a and the nozzle cylinder 23 form a control chamber 26 in which the internal fuel pressure can be switched between high pressure and low pressure. ing. The needle 21 is urged in the valve closing direction by the fuel pressure in the control chamber 26 and is opened in the valve opening direction by the high pressure fuel guided from the fuel inlet 11 to the nozzle hole 24 side through the high pressure fuel passage 13. Be energized.

  A valve chamber 14 in which the control valve 3 for controlling the pressure in the control chamber 26 is housed is formed in the intermediate portion in the axial direction of the body 1a. The control chamber 26 is always in communication with the valve chamber 14 via the communication passage 15. More specifically, the control chamber 26 communicates only with the valve chamber 14. A common orifice 50 is provided in the communication passage 15.

  The valve chamber 14 is connected to a high pressure communication passage 13 a branched from the high pressure fuel passage 13. Further, the valve chamber 14 is connected to the fuel outlet portion 12 through a low pressure fuel passage 16. An out orifice 60 is provided in the low pressure fuel passage 16.

  The control valve 3 opens and closes between the valve chamber 14 and the low-pressure fuel passage 16 by contacting and separating from the low-pressure side seat surface 33, and contacts and separates from the valve chamber 14 and the high-pressure communication passage 13a by contacting and separating from the high-pressure side seat surface 34. A valve body 31 that opens and closes the valve body, and a valve spring 32 that biases the valve body 31 in such a direction that the space between the valve chamber 14 and the high-pressure communication passage 13a is opened and the space between the valve chamber 14 and the low-pressure fuel passage 16 is closed. have.

  An actuator chamber 17 in which the actuator 4 that drives the control valve 3 is housed is formed at the other axial end of the body 1a. The actuator chamber 17 is connected to the low pressure fuel passage 16 via the low pressure communication passage 16a.

  The actuator 4 includes a piezo stack 41 in which a large number of piezo elements are stacked and expands and contracts due to charge and discharge, and a transmission unit that transmits the expansion and contraction displacement of the piezo stack 41 to the valve body 31 of the control valve 3.

  The transmission unit is configured as follows. A first piston 43 and a second piston 44 are slidably and liquid-tightly inserted into the actuator cylinder 42, and a liquid chamber filled with fuel is provided between the first piston 43 and the second piston 44. 45 is formed.

  The first piston 43 is urged toward the piezo stack 41 by a first spring 46 and is directly driven by the piezo stack 41. When the piezo stack 41 is extended, the pressure of the liquid chamber 45 is increased by the first piston 43.

  The second piston 44 is urged toward the valve body 31 side of the control valve 3 by the second spring 47 and is actuated by receiving the pressure of the liquid chamber 45 to drive the valve body 31. When the piezo stack 41 extends, the second piston 44 operates by receiving the pressure of the liquid chamber 45 that has been increased in pressure, and the valve chamber 14 and the high-pressure communication passage 13a are closed and the valve chamber 14 The valve body 31 is driven to a position where the space between the low pressure fuel passage 16 is opened. On the other hand, when the piezo stack 41 contracts, that is, when the pressure in the liquid chamber 45 is low, the second piston 44 is pushed back toward the first piston 43 by the valve spring 32 of the control valve 3 against the second spring 47.

  A load sensor 7 that detects a load generated by the piezo stack 41 is disposed adjacent to the piezo stack 41 on the side opposite to the piezo stack 41. The load sensor 7 is configured by laminating a large number of piezo elements, and detects a load by utilizing the piezoelectric effect of the piezo elements.

  A back pressure valve 120 that controls the pressure on the low pressure fuel passage 16 side is disposed in the return path 110 that connects the fuel tank 100 and the fuel outlet portion 12. Incidentally, while the pressure of the high pressure fuel stored in the pressure accumulator is 100 MPa or more, the back pressure valve 120 controls the pressure on the low pressure fuel passage 16 side to about 1 MPa.

  A charging current is supplied to the piezo stack 41 via the drive circuit 130. The drive circuit 130 is controlled by an electronic control unit (hereinafter referred to as ECU) 140.

  In this embodiment, the piezo stack 41 is driven by a multi-switching method (hereinafter referred to as an MS method).

  That is, the drive circuit 130 includes a switching element (not shown) that can directly disconnect the DC power supply in a path through which the piezo stack 41 is energized from the DC power supply (not shown) via the inductor (not shown). The MS method is to charge the piezo stack 41 in several times by turning on / off the switching element a plurality of times based on a charge control signal from the ECU 140. While the switching element is on, a charging current that gradually increases flows to the piezo stack 41. When the switching element is turned off, a charging current gradually decreasing flows to the piezo stack 41 by the flywheel action. In this way, the piezo voltage continues to increase while the charging current flows through the piezo stack 41. The detailed driving method and circuit configuration of the MS method are well known in, for example, Japanese Patent Application Laid-Open No. 2001-53348.

  The charge and voltage signals from the load sensor 7 are input to the ECU 140 via the drive circuit 130. The ECU 140 includes an MPU 1401, an AD converter 1402, a DSP 1403, and the like, and calculates the load generated by the piezo stack 41 by performing high-speed A / D processing on the input charge and voltage signals.

  The ECU 140 includes a ROM, EEPROM, RAM, and the like (not shown), and the MPU 1401 performs arithmetic processing according to a program stored in the ROM. The ECU 140 receives signals from various sensors (not shown) that detect the intake air amount, the accelerator pedal depression amount, the internal combustion engine speed, the fuel pressure in the accumulator, and the like.

  Next, the operation of the fuel injection device will be described. When a charging current is supplied to the piezo stack 41 via the drive circuit 130 and the piezo voltage rises, the piezo stack 41 extends and the first piston 43 is driven, and the pressure of the liquid chamber 45 is increased by the first piston 43. . The second piston 44 is driven toward the valve body 31 side of the control valve 3 by the pressure of the liquid chamber 45 that has been increased in pressure.

  Then, when the valve body 31 is driven by the second piston 44, the valve body 31 comes into contact with the high-pressure side seat surface 34 to close the space between the valve chamber 14 and the high-pressure communication passage 13a. Is separated from the low-pressure side seat surface 33 and the space between the valve chamber 14 and the low-pressure fuel passage 16 is opened. Therefore, the fuel in the control chamber 26 is returned to the fuel tank 100 via the common orifice 50, the communication passage 15, the valve chamber 14, the out orifice 60, and the low pressure fuel passage 16.

  As a result, the pressure in the control chamber 26 decreases and the force for urging the needle 21 in the valve closing direction is reduced, so that the needle 21 moves in the valve opening direction, and the seat portion 21b moves away from the valve seat 25 and the injection hole. 24 is opened, and fuel is injected from the nozzle hole 24 into the cylinder of the internal combustion engine.

  After that, when the electric charge is discharged from the piezo stack 41 and the piezo voltage decreases, the piezo stack 41 contracts and the first piston 43 is returned to the piezo stack 41 side by the first spring 46. Further, the valve body 31 and the second piston 44 are returned to the first piston 43 side by the valve spring 32.

  As a result, the valve body 31 is separated from the high pressure side seat surface 34 to open the valve chamber 14 and the high pressure communication passage 13a, and the valve body 31 contacts the low pressure side seat surface 33 so that the valve chamber 14 and the low pressure fuel The space between the passage 16 is closed. Therefore, the high pressure fuel from the pressure accumulator is introduced into the control chamber 26 through the high pressure fuel passage 13, the high pressure communication passage 13 a, the valve chamber 14, the communication passage 15, and the common orifice 50.

  As a result, the pressure in the control chamber 26 rises and the force for urging the needle 21 in the valve closing direction increases, so that the needle 21 moves in the valve closing direction, and the seat portion 21b is seated on the valve seat 25 and sprayed. The hole 24 is closed and the fuel injection is finished.

  Next, control when driving the piezo stack 41 of the fuel injection device will be described in detail with reference to FIGS. 4 and 5. 4 is a flowchart showing a control process executed by the ECU 140, and FIG. 5 is a time chart showing an operation example when the control process is performed.

  The process shown in FIG. 4 is started when an injection permission signal for permitting fuel to be injected from the fuel injection valve 1 is turned on.

  As shown in FIG. 4, when the injection permission signal is turned on, in step S100, a charge control signal for controlling the operation of the drive circuit 130 is output to the drive circuit 130. While the charge control signal is on, the switching element described above is turned on and a charging current gradually increasing flows to the piezo stack 41. When the charge control signal is turned off, the switching element is turned off and the piezo stack is operated by a flywheel action. A charging current that gradually decreases to 41 flows, whereby the piezo voltage continues to increase. The charge control signal corresponds to the drive signal of the present invention.

  In the next step S101, the load sensor 7 detects a load generated by the piezo stack 41 (hereinafter referred to as a piezo load) at the first time Ta and the second time Tb.

  Here, a time T0 in FIG. 5 is a time when the supply of the charging current from the driving circuit 130 to the piezo stack 41 is started, and is hereinafter referred to as a charging start time. The first time Ta is when a predetermined time has elapsed from the charging start time T0, and is preset in the vicinity of the timing at which the valve body 31 is separated from the low-pressure side seat surface 33. The first time Ta is stored in the ROM of the ECU 140. The piezo load Fa detected at the first time Ta is hereinafter referred to as a first time load.

  The second time Tb is a time when a predetermined time has elapsed from the first time Ta, and is set in advance at a timing immediately before the valve body 31 comes into contact with the high-pressure side seat surface 34. The second time Tb is stored in the ROM of the ECU 140. The piezo load Fb detected at the second time Tb is hereinafter referred to as a second time load.

  In the next step S102, the first time load Fa and the second time load Fb are compared to determine whether or not the valve body 31 is separated from the low pressure side seat surface 33. Step S102 corresponds to the first abnormality determination means of the present invention.

  Here, in a state where the valve body 31 is in contact with the low pressure side seat surface 33, the valve body 31 is biased toward the low pressure side seat surface 33 due to the pressure difference between the valve chamber 14 and the low pressure fuel passage 16. On the other hand, when the valve body 31 is not in contact with either the low-pressure side seat surface 33 or the high-pressure side seat surface 34, no force is generated to bias the valve body 31 toward the low-pressure side seat surface 33 due to the pressure difference. . Therefore, if Fa> Fb (YES in S101), it is determined that the valve body 31 is operating normally, and the process proceeds to step S103.

  In step S103, the timing Tc (hereinafter referred to as the high-pressure side closing time) at which the valve body 31 is in contact with the high-pressure side seat surface 34 and the space between the valve chamber 14 and the high-pressure fuel passage 13 is closed is detected. Specifically, when the valve body 31 comes into contact with the high-pressure side seat surface 34, the piezo load increases. Therefore, when the piezo load reaches the threshold value Fc after the second time Tb, the valve body 31 moves to the high-pressure side seat surface. 34 is assumed to be closed.

  By the way, when the valve body 31 is in contact with the high pressure side seat surface 34, the valve body 31 is urged away from the high pressure side seat surface 34 by the fuel pressure in the high pressure fuel passage 13. In order to reliably close the space between the fuel passage 13 and the fuel pressure, the valve body 31 needs to be pressed against the high-pressure side seat surface 34 with a larger force.

  Therefore, in the present embodiment, as shown in FIG. 6, the threshold value Fc is increased as the fuel pressure Pc in the accumulator (hereinafter referred to as common rail pressure) increases. According to this, it is possible to accurately detect the timing at which the valve body 31 substantially closes the space between the valve chamber 14 and the high-pressure fuel passage 13. A map defining the relationship shown in FIG. 6 is stored in the ROM of the ECU 140.

  In step S104 as response time calculation means, a time ΔT (hereinafter referred to as control valve response) from when charging of the piezo stack 41 is started until the valve element 31 closes between the valve chamber 14 and the high-pressure fuel passage 13 is performed. Time). Specifically, the control valve response time ΔT is a time from the charging start time T0 to the high-pressure side closing time Tc (that is, ΔT = Tc−T0).

  In the next step S105, it is determined whether or not the control valve response time ΔT is within a predetermined allowable range (ΔTmin ≦ ΔT ≦ ΔTmax). This step S105 corresponds to the second abnormality determination means of the present invention.

  In the present embodiment, the control valve response time ΔT is set to the target control valve response time ΔTp by appropriately correcting the increase speed Vc of the piezo voltage when the piezo stack 41 is charged (hereinafter referred to as the charging speed). As shown in FIG. 7, ΔTmin is an allowable minimum value of the control valve response time ΔT that can be corrected, and ΔTmax is an allowable maximum value of the control valve response time ΔT that can be corrected. It should be noted that the allowable minimum value ΔTmin and the allowable maximum value ΔTmax of the control valve response time ΔT that can be corrected are stored in the ROM of the ECU 140.

  If the control valve response time ΔT is within the allowable range (ΔTmin ≦ ΔT ≦ ΔTmax) (YES in S105), the process proceeds to step S106.

  In step S106 as response time correction means, the charging speed Vc at the next injection and the charging control signal at the next injection (that is, the corrected charging control signal) are calculated. Specifically, the charging speed Vc at the next injection is calculated based on the target control valve response time ΔTp at the next injection so that the control valve response time ΔT matches the target control valve response time ΔTp. Further, a corrected charge control signal for realizing the charging speed Vc at the next injection is calculated.

  For example, when the target control valve response time ΔTp at the next injection is shorter than the control valve response time ΔT at the current injection, the charging speed Vc at the next injection is increased. Specifically, as indicated by a one-dot chain line in FIG. 5, the period during which the gradually increasing charging current flows to the piezo stack 41 is lengthened by increasing the ON time of the first charge control signal at the next injection. At this time, the ON time of the second and subsequent charge control signals at the next injection is shortened so that the total charge energy amount at the next injection becomes equal to the total charge energy amount at the current injection. On the other hand, when the target control valve response time ΔTp at the next injection is longer than the control valve response time ΔT at the current injection, the on-time of the first charge control signal at the next injection is shortened to charge at the next injection Reduce the speed Vc.

  The charging speed Vc is obtained by an arithmetic expression stored in the ROM of the ECU 140. Further, a map defining the relationship between the charging speed Vc and the charging control signal is stored in the ROM of the ECU 140, and the charging control signal corresponding to the charging speed Vc at the next injection is obtained using the map.

  Next, in step S107, a piezo load F1 (hereinafter referred to as a post-charge load) at the third time Td when the piezo load is stabilized after the piezo stack 41 is charged is measured. The third time Td is stored in the ROM of the ECU 140.

  Next, in step S108, a load error ΔF (that is, ΔF = F1-F0) between the post-charge load F1 and the target post-charge load F0 is obtained. The target post-charge load F0 is stored in the ROM of the ECU 140.

  Next, in step S109, it is determined whether or not the load error ΔF is within a predetermined range (ΔFmin ≦ ΔF ≦ ΔFmax). In the present embodiment, the post-charge load F1 is set to an appropriate magnitude (ie, within the allowable load range) by further correcting the charge control signal obtained in step S106 and appropriately correcting the charge energy amount. However, as shown in FIG. 8, ΔFmin is an allowable minimum value of the load error ΔF, and ΔFmax is an allowable maximum value of the load error ΔF. The allowable minimum value ΔFmin and the allowable maximum value ΔFmax of the load error ΔF are stored in the ROM of the ECU 140.

  If the load error ΔF is within the predetermined range (YES in S109), in other words, if the post-charge load F1 is within the allowable load range, the process proceeds to step S110. In step S110, the current charging energy amount E0 is held, and the charging energy amount E1 at the next injection is set to E0. Therefore, the charge control signal obtained in step S106 is not corrected, and the post-charge load F1 at the next injection does not change.

  On the other hand, if step S109 is NO, that is, if the load error ΔF is not within the predetermined range, the process proceeds to step S111. In step S111, a charge energy correction value ΔE (a function of the load error ΔF) is calculated based on the load error ΔF. A map (see FIG. 8) defining the relationship between the load error ΔF and the charging energy correction value ΔE is stored in the ROM of the ECU 140, and the charging energy correction value ΔE is obtained using the map.

  Next, in step S112 as the third abnormality determining means, it is determined whether or not the charging energy correction value ΔE is within a predetermined range (ΔEmin ≦ ΔE ≦ ΔEmax). As shown in FIG. 8, ΔEmin is an allowable minimum value of charging energy correction value ΔE, and ΔEmax is an allowable maximum value of charging energy correction value ΔE. The allowable minimum value ΔEmin and the allowable maximum value ΔEmax of the charging energy correction value ΔE are stored in the ROM of the ECU 140.

  If the charging energy correction value ΔE is within a predetermined range (ΔEmin ≦ ΔE ≦ ΔEmax) (YES in step S112), the process proceeds to step S113.

  In step S113 as post-charge load correcting means, a charge energy amount E1 at the next injection and a charge control signal at the next injection (that is, a corrected charge control signal) are calculated.

  Specifically, a value obtained by adding the charging energy correction value ΔE to the charging energy amount E0 at the current injection is set as the charging energy amount E1 at the next injection. Moreover, in order to implement | achieve the charge energy amount E1 at the time of next injection, the charge control signal calculated | required by step S106 is further correct | amended. For example, when the charge energy correction value ΔE is positive, the on-time of the last charge control signal in the charge control signal obtained in step S106 is lengthened. When the charge energy correction value ΔE is negative, the on-time of the last charge control signal in the charge control signal obtained in step S106 is shortened.

  A map defining the relationship between the charging energy amount E1 at the next injection and the correction amount of the charging control signal is stored in the ROM of the ECU 140, and the correction amount of the charging control signal is obtained using the map.

  In the next step S100, the charge control signal obtained in step S106 or the charge control signal further corrected in step S113 is output to the drive circuit 130.

  Here, of the time from the start of charging to the piezo stack 41 to the start of injection, the valve element 31 is connected to the valve chamber 14 and the high-pressure fuel passage 13 after the charging to the piezo stack 41 is started. The time until the interval is closed is affected by the characteristics of the piezo stack 41, but the time from when the valve body 31 closes between the valve chamber 14 and the high pressure fuel passage 13 until the injection is started is Not affected by characteristics.

  Therefore, by controlling the charging of the piezo stack 41 based on the charging control signal obtained in step S106, the charging of the piezo stack 41 is started regardless of the individual variation of the characteristics of the piezo stack 41 or deterioration with time. Since the control valve response time ΔT until the valve body 31 closes between the valve chamber 14 and the high pressure fuel passage 13 can be made to coincide with the target control valve response time ΔTp, the characteristics of the piezo stack 41 vary among individuals. In addition, the injection start timing and the injection amount can be accurately controlled regardless of deterioration with time.

  Further, by controlling the charging of the piezo stack 41 based on the charging control signal corrected in step S113, the post-charging load F1 is adjusted within the allowable load range, so the valve element 31 to the high-pressure side seat surface 34 is adjusted. It is possible to prevent a sealing failure due to a lack of the pressing load, and to prevent or suppress wear of the valve body 31 and the high-pressure side seat surface 34 due to an excessive pressing load.

  In step S114 executed subsequent to step S110 or step S113, it is determined whether or not the injection permission signal is turned off. If it is determined in this step that the injection permission signal is not turned off, it is continuously monitored whether or not the injection permission signal is turned off. If it is determined in this step that the injection permission signal is turned off, the process proceeds to step 115.

  In step 115, a discharge control signal is output to the drive circuit 130, and the electric charge charged in the piezo stack 41 is discharged by a known method. As a result, the valve body 31 is separated from the high pressure side seat surface 34 to open the valve chamber 14 and the high pressure communication passage 13a, and the valve body 31 contacts the low pressure side seat surface 33 so that the valve chamber 14 and the low pressure fuel The space between the passage 16 is closed and the fuel injection is completed. And after performing the process of step 115, this flow is complete | finished.

  When step S102 is NO (ie, Fa ≦ Fb), when step S105 is NO (ie, ΔTmin> ΔT> ΔTmax), and when step S112 is NO (ie, ΔEmin> ΔE> ΔEmax), the piezo stack 41 Then, it is determined that the control valve 3 is malfunctioning due to an abnormality of the transmission unit or the like, and the process proceeds to step S116.

  In step S116, information on which cylinder fuel injection valve 1 is determined to be abnormal in steps S102, S105, and S112 is stored in the EEPROM of ECU 140, and fuel injection in that cylinder is performed. Take a ban.

It is sectional drawing which shows the whole structure of the fuel-injection apparatus which concerns on one Embodiment of this invention. It is an expanded sectional view of the A section of FIG. It is a perspective view which shows the load sensor and piezo stack of FIG. It is a flowchart which shows the control processing performed in ECU140 of FIG. It is a time chart which shows the operation example when the control processing of FIG. 4 is performed. It is a characteristic view which shows the relationship between the common rail pressure Pc and the threshold value Fc. It is a characteristic view which shows the relationship between control valve response time (DELTA) T and charging speed Vc. FIG. 6 is a characteristic diagram showing a relationship between a load error ΔF and a charging energy correction value ΔE.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel injection valve, 2 ... Nozzle, 3 ... Control valve, 7 ... Load sensor, 13 ... High pressure fuel passage, 14 ... Valve chamber, 15 ... Communication passage, 16 ... Low pressure fuel passage, 21 ... Needle, 24 ... Injection hole , 26 ... control chamber, 33 ... low pressure side seat surface, 34 ... high pressure side seat surface, 41 ... piezo stack, 130 ... drive circuit, 140 ... control device.

Claims (8)

It is arranged in the valve chamber (14), opens and closes the valve chamber (14) and the low-pressure fuel passage (16) by contacting and separating from the low-pressure side seat surface (33), A control valve (3) that opens and closes between the valve chamber (14) and the high-pressure fuel passage (13).
A piezo stack (41) that expands and contracts due to charge and discharge of electric charges and drives the control valve (3);
A control chamber (26) that is always in communication with the valve chamber (14) via a communication passage (15);
A nozzle (2) urged in a direction in which the needle (21) closes the nozzle hole (24) by the fuel pressure in the control chamber (26),
By charging the piezo stack (41), the control valve (3) is configured to close the space between the valve chamber (14) and the high pressure fuel passage (13) and open the nozzle (2). A fuel injection device having a fuel injection valve (1),
A load sensor (7) for detecting a load generated by the piezo stack (41);
A drive circuit (130) for supplying a charging current to the piezo stack (41);
A control device (140) for controlling the operation of the drive circuit (130) by outputting a drive signal to the drive circuit (130);
When the supply start of charging current from the drive circuit (130) to the piezo stack (41) is a charge start time, the piezo stack (41) detected by the load sensor (7) from the charge start time. Response time calculating means (S104) for calculating a control valve response time until the load reaches a threshold value;
The control valve response time calculated by the response time calculation means (S104) is compared with the target control valve response time, and the drive signal is corrected so that the control valve response time matches the target control valve response time. A fuel injection device comprising response time correction means (S106). 2. The fuel injection device according to claim 1, wherein a charging speed of the piezo stack is changed by correcting the driving signal. 3. The fuel injection device according to claim 1 or 2, wherein the response time calculation means (S104) increases the threshold value as the fuel pressure in the high-pressure fuel passage (13) increases. The load of the piezo stack (41) detected by the load sensor (7) when a predetermined time has elapsed from the charging start time is defined as a first time load, and a predetermined time has elapsed after the predetermined time has elapsed. When the load of the piezo stack (41) detected by the load sensor (7) is a second time load,
4. The apparatus according to claim 1, further comprising first abnormality determination means (S <b> 102) that determines that the second time load is an abnormal state when the second time load is equal to or greater than the first time load. Fuel injection device. A second abnormality determining means (S105) for determining that the control valve response time calculated by the response time calculating means (S104) is out of an allowable time range is determined as an abnormal state. The fuel injection device according to any one of 1 to 4. When the load of the piezo stack (41) detected by the load sensor (7) after the charge of the piezo stack (41) is completed is a post-charge load,
The fuel injection device according to any one of claims 1 to 5, further comprising post-charge load correction means (S113) for correcting the drive signal so that the post-charge load falls within an allowable load range. The fuel injection device according to claim 6, wherein the charge energy amount for the piezo stack (41) is changed by the correction of the drive signal. The third abnormality determining means (S112) for determining that the correction value of the charging energy amount for the piezo stack (41) is in an abnormal state when the value is outside a predetermined allowable range. The fuel injection device described.

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