JP2017015033A - Injection controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection controller capable of suppressing deviation between an actual injection amount and a target injection amount, even in a case where an injection amount of fuel is minute.SOLUTION: An injection controller 20, when a target injection amount as a target value of an injection amount of fuel from a fuel injection valve 10 is larger than a predetermined threshold injection amount, controls operation of a piezoelectric actuator 500 so that a needle 400 moves to a maximum injection position at which an injection ratio is maximum, and when the target injection amount is equal to or less than the threshold injection amount, restricts operation of the piezoelectric actuator 500 so that the needle 400 operates within a range not exceeding a preset suppression injection position as a position when opening is made smaller than that at the maximum injection position.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an injection control device that controls the operation of a fuel injection valve in an internal combustion engine.

  A fuel injection valve that injects fuel in an internal combustion engine changes the opening of an injection port by the movement of a valve body provided therein, whereby the fuel injection rate (the amount of fuel injected per unit time) Is something that changes. An actuator for moving the valve body is provided inside the fuel injection valve. The injection control device adjusts the position of the valve body, that is, the opening degree of the injection port by controlling the operation of the actuator, and makes the fuel injection amount from the fuel injection valve coincide with the target injection amount.

  In the fuel injection valve described in Patent Document 1 below, a piezoelectric actuator is used as an actuator. As the drive voltage applied to the piezoelectric actuator increases, the valve element moves to the valve opening side (the side opposite to the injection port). After the valve body reaches the position on the most valve opening side in the moving range, the fuel injection amount is adjusted by adjusting the time during which the valve is open.

JP 2009-299494 A

  In the fuel injection valve having a configuration in which the opening degree is changed by changing the position of the valve body as in the fuel injection valve described in Patent Document 1, when a minute amount of fuel is to be injected, The difference between the actual injection amount and the target injection amount tends to increase. This is because when the valve body reaches the position on the most open side, the valve body collides with the inner wall of the fuel injection valve and rebounds, and the valve body temporarily returns to the valve closing side position. Is attributed.

  When the fuel injection amount is relatively large, since the valve body returns to the (maximum) valve opening position after the valve body rebounds as described above, the influence of the rebound on the fuel injection amount is small. However, when the fuel injection amount is relatively small, the fuel injection ends before the bounced valve body returns to the original position, so the influence of the rebound on the fuel injection amount becomes large. .

  The present invention has been made in view of such a problem, and an object thereof is to suppress a deviation between the actual injection amount and the target injection amount even when the fuel injection amount is very small. It is an object of the present invention to provide an injection control device that can perform the above-described operation.

  In order to solve the above problems, an injection control device according to the present invention is an injection control device that controls the operation of a fuel injection valve in an internal combustion engine, and the fuel injection valve is used for changing the opening of an injection port. The valve body is moved by an actuator, thereby changing the fuel injection rate. The target injection amount, which is the target value of the fuel injection amount from the fuel injection valve, is larger than the predetermined threshold injection amount. In this case, the operation of the actuator is controlled so that the valve body moves to the maximum injection position where the injection rate becomes maximum, and when the target injection amount is equal to or less than the threshold injection amount, the valve body is The operation of the actuator is limited so as to operate within a range that does not exceed the suppression injection position set in advance as a position where the opening degree becomes smaller.

  In such an injection control device, when the target injection amount is relatively small and equal to or less than the threshold injection amount, the operation of the valve body is limited. Specifically, the operation of the actuator is limited so that the valve element operates within a range that does not exceed a preset suppression injection position. Since the position of the valve body at the time of fuel injection is limited to be within the range from the valve closing position to the suppression injection position, a phenomenon that the valve body reaches the position closest to the valve opening side and rebounds may occur. It is suppressed. As a result, a phenomenon in which the fuel injection amount is reduced due to the influence of rebound is less likely to occur, and a deviation between the actual injection amount and the target injection amount is suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where the injection quantity of fuel is very small, the injection control apparatus which can suppress the shift | offset | difference between actual injection quantity and target injection quantity is provided.

It is a figure which shows typically the structure of the injection control apparatus which concerns on embodiment of this invention, and the fuel injection valve used as the control object. It is a figure which shows the example of the rectangular wave input as an injection command value, and the change of the drive voltage applied to a piezoelectric actuator. It is a figure which shows the relationship between an injection command value and injection quantity. It is a figure which shows the example of the waveform of the actual drive voltage corresponding to various injection command values. FIG. 5 is a diagram showing a change in an actual fuel injection rate when the drive voltage shown in FIG. 4 is input. It is a flowchart which shows the flow of the process performed with the injection control apparatus of FIG. It is a figure which shows the example of the rectangular wave input as an injection command value and the change of the drive voltage applied to a piezoelectric actuator in the case of performing the conventional control. It is a figure which shows the example of the rectangular wave input as an injection command value and the change of the drive voltage applied to a piezoelectric actuator in the case of performing the conventional control. It is a figure which shows the relationship between the injection command value and the injection quantity when the conventional control is performed. It is a figure which shows the example of the waveform of the actual drive voltage corresponding to various injection command values when the conventional control is performed. It is a figure which shows the change of the actual fuel injection rate when the drive voltage shown by FIG. 10 is input.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same constituent elements in the drawings will be denoted by the same reference numerals as much as possible, and redundant description will be omitted.

  With reference to FIG. 1, an injection control device 20 according to an embodiment of the present invention and a fuel injection valve 10 that is a control target of the injection control device 20 will be described. First, a specific structure of the fuel injection valve 10 will be described.

  The fuel injection valve 10 is for injecting fuel into an internal combustion engine (not shown) of a vehicle, and is also called a so-called injector. The fuel injection valve 10 includes a housing 100, a cap 200, a nozzle body 300, a needle 400, a piezoelectric actuator 500, and a piston 600.

  The housing 100 is a portion formed as a substantially cylindrical container. Inside the housing 100, a piezoelectric actuator 500 and a piston 600 described later are accommodated. A fuel supply pipe 110 is connected to the side surface of the housing 100. The fuel supply pipe 110 is a pipe for supplying fuel from a fuel pump (not shown) to the fuel injection valve 10. The fuel fed from the fuel pump flows into the housing 100 through the fuel supply pipe 110 and is then injected from an injection port 310 formed at the tip of the nozzle body 300.

  The internal space of the housing 100 is partitioned by a partition plate 120. A part of the piezoelectric actuator 500 and the piston 600 is accommodated in a space above the partition plate 120 (on the side opposite to the nozzle body 300). Another part of the piston 600 is housed in a space below the partition plate 120 (on the nozzle body 300 side). The fuel supplied to the fuel injection valve 10 through the fuel supply pipe 110 flows only into the space below the partition plate 120 and does not flow into the space where the piezoelectric actuator 500 is disposed.

  A flow path 130 is formed below the partition plate 120 in the housing 100. One end (upper end) of the flow path 130 is connected to the inside of the fuel supply pipe 110, and the other end (lower end) is formed to extend to the lower end of the housing 100.

  The cap 200 is a lid-like member, and is disposed so as to cover one end side (the lower end side in FIG. 1) of the housing 100. The inner peripheral surface of the cap 200 is subjected to female screw processing, and the outer peripheral surface of the housing 100 is subjected to male screw processing. The cap 200 is fixed in a state where it is screwed into the housing 100. The cap 200 is formed with a through hole 201 through which a later-described nozzle body 300 is inserted.

  Inside the cap 200, a substantially disc-shaped partition plate 210 is disposed between the housing 100 and the nozzle body 300 while being sandwiched between the two. The lower end of the housing 100 is in contact with the upper surface 211 of the partition plate 210. The upper end of the nozzle body 300 is in contact with the lower surface 212 of the partition plate 210.

  Two through holes 213 and 214 are formed in the partition plate 210 so as to penetrate from the upper surface 211 to the lower surface 212. The upper end of the through hole 213 is opened at a position facing the lower end of the flow path 130. Further, the lower end of the through hole 213 is opened at a position substantially coincident with the central axis of the nozzle body 300. Through the through-hole 213, the flow path 130 and the back pressure chamber 410 (described later) of the needle 400 are communicated.

  The upper end of the through hole 214 is opened at a position facing the lower end surface of the piston 600. The lower end of the through hole 214 is opened at a position facing the upper end of the flow path 330 formed on the outer peripheral side of the needle 400. The pressurizing chamber 140 (described later) and the flow path 330 are communicated with each other through the through hole 214.

  The nozzle body 300 is a member that accommodates the needle 400 therein, and a part of the nozzle body 300 is disposed inside the cap 200, and the other part faces the outside (downward in FIG. 1) from the through hole 201. Protruding. An injection port 310 that is a fuel outlet is formed at the tip of the protruding portion. Further, a valve seat 320 that is a portion with which the tip of the needle 400 abuts is provided in the vicinity of the injection port 310 on the inner wall surface of the nozzle body 300.

  The needle 400 is a member formed in an elongated rod shape, and functions as a valve body for adjusting the opening of the fuel injection valve 10. The needle 400 is accommodated in the internal space of the nozzle body 300, and is held in a movable state along the vertical direction in FIG. The portion of the needle 400 near the partition plate 210 has a larger diameter than the other portions. Hereinafter, this portion is referred to as “expanded diameter portion 430”.

  A back pressure chamber 410 is formed inside the needle 400. The back pressure chamber 410 is an elongated space formed along the longitudinal direction (vertical direction) of the needle 400, and the upper end thereof is open. The lower end of the through hole 213 is disposed at a position facing the opening.

  The lower end of the back pressure chamber 410 is higher than the lower end of the needle 400. Further, a plurality of openings 420 are formed near the lower end of the back pressure chamber 410 so that the back pressure chamber 410 communicates with the outside. For this reason, the fuel supplied through the fuel supply pipe 110 flows into the back pressure chamber 410 through the flow path 130 and the through hole 213 in order, and then passes through the opening 420 to the outside of the needle 400 (inside the nozzle body 300). To leak.

  However, when the position of the needle 400 is on the lowermost side (the injection port 310 side) as shown in FIG. 1 and the tip of the needle 400 is in contact with the valve seat 320, the fuel passing through the opening 420 is It is not ejected from the ejection port 310. When the needle 400 moves upward (opposite to the injection port 310) and the tip of the needle 400 and the valve seat 320 are separated from each other, the fuel passing through the opening 420 is injected from the injection port 310.

  The higher the needle 400 is on the upper side, that is, the larger the opening of the injection port 310, the higher the fuel injection rate (the amount of fuel injected from the injection port 310 per unit time). When the needle 400 is at the uppermost side in the movable range and the upper end surface 440 of the needle 400 is in contact with the lower surface 212 of the partition plate 210, the fuel injection rate is maximized.

  A spring 301 is accommodated in the back pressure chamber 410. The needle 400 is urged downward by the elastic force of the spring 301. For this reason, when the fuel is not injected, the tip of the needle 400 is pressed against the valve seat 320 by the elastic force of the spring 301.

  A cylindrical sleeve 350 is disposed on the outer peripheral side of the needle 400. The inner surface of the sleeve 350 is in contact with the outer surface of the enlarged diameter portion 430. The sleeve 350 is accommodated in the internal space of the nozzle body 300 so as to be slidable in the vertical direction with respect to the needle 400.

  A flow path 330 is formed between the outer peripheral surface of the sleeve 350 and the inner wall surface of the nozzle body 300. The upper end portion of the flow path 330 is connected to the lower end of the through hole 214. Further, the lower end portion of the flow path 330 is connected to a drive chamber 340 that is a space formed on the lower side of the enlarged diameter portion 430. That is, the through hole 214 and the drive chamber 340 are communicated with each other by the flow path 330.

  A spring 360 is accommodated in the flow path 330. The sleeve 350 is biased upward by the elastic force of the spring 360. Therefore, the upper end of the sleeve 350 is pressed against the lower surface 212 of the partition plate 210.

  The piezoelectric actuator 500 is an actuator constituted by a piezoelectric element, and expands and contracts according to the magnitude of a driving voltage applied from the outside. The upper end portion 510 of the piezoelectric actuator 500 is fixed to the top plate of the housing 100, and the lower end portion thereof is in contact with the upper end portion of the piston 600. As the drive voltage increases, the longitudinal dimension of the piezoelectric actuator 500 increases and the piston 600 is pushed downward. Further, when the driving voltage decreases, the longitudinal dimension of the piezoelectric actuator 500 decreases, and the piston 600 is pulled upward (by a spring 150 described later).

  An upper end portion 510 of the piezoelectric actuator 500 is inserted through a through hole formed in the top plate of the housing 100, and a part thereof is exposed to the outside. Application of the drive voltage to the piezoelectric actuator 500 is performed through the portion. A seal ring 520 is disposed between the upper end portion 510 and the housing 100.

  The piston 600 is a member that moves up and down according to the expansion and contraction of the piezoelectric actuator 500. The piston 600 as a whole has a substantially cylindrical shape, and is arranged in a state where the longitudinal direction thereof coincides with the longitudinal direction of the housing 100. A portion on the upper side (piezoelectric actuator 500 side) of the piston 600 is a small-diameter portion 610 having a relatively small cross-sectional diameter. Further, the lower portion (partition plate 210 side) of the piston 600 is a large-diameter portion 620 having a relatively large cross-sectional diameter.

  A plate-like spring seat 611 is fixed at a position close to the piezoelectric actuator 500 in the small diameter portion 610. A spring 150 is disposed between the spring seat 611 and the partition plate 120. The spring seat 611 is biased upward by the elastic force of the spring 150. For this reason, the upper end of the piston 600 is always pressed against the lower end of the piezoelectric actuator 500.

  The small diameter portion 610 of the piston 600 is in a state of penetrating the partition plate 120. A seal ring 630 is disposed between the small diameter portion 610 and the partition plate 120. The seal ring 630 prevents the fuel from leaking to the piezoelectric actuator 500 side from the partition plate 120.

  A gap is formed between the lower end surface of the large diameter portion 620 and the upper surface 211 of the partition plate 210, and the gap serves as the pressurizing chamber 140. The pressurizing chamber 140 is always filled with fuel. The volume of the pressurizing chamber 140 changes as the piston 600 moves.

  The operation of the fuel injection valve 10 will be described. When the drive voltage is not applied to the piezoelectric actuator 500 and the longitudinal dimension of the piezoelectric actuator 500 (hereinafter simply referred to as “length”) is the shortest, the tip of the needle 400 is elastic of the spring 301. It is pressed against the valve seat 320 by force. For this reason, fuel is not injected from the injection port 310.

  When a drive voltage is applied to the piezoelectric actuator 500 and the length of the piezoelectric actuator 500 increases, the piston 600 moves downward accordingly. The volume of the pressurizing chamber 140 becomes small, and a part of the fuel filled in the pressurizing chamber 140 flows into the flow path 330 and the drive chamber 340 through the through hole 214. Thereby, the pressure of the fuel in the drive chamber 340 increases, and the needle 400 receives a force directed upward. The needle 400 moves upward, and its tip is separated from the valve seat 320. As a result, fuel injection from the injection port 310 is started.

  When the drive voltage applied to the piezoelectric actuator 500 is increased and the length of the piezoelectric actuator 500 is further increased, the piston 600 further moves downward. The needle 400 further moves upward, and the opening of the injection port 310 increases, so that the fuel injection rate increases. As described above, the fuel injection rate increases in accordance with the magnitude of the drive voltage applied to the piezoelectric actuator 500.

  The injection control device 20 will be described. The injection control device 20 is a control device configured as a computer system including a CPU, a ROM, a RAM, and the like. The injection control device 20 adjusts the drive voltage applied to the piezoelectric actuator 500 to thereby indicate the fuel injection rate and the injection amount from the fuel injection valve 10 (the total amount of fuel injected in one injection). The same applies to the following).

  A pressure detector 30 is provided in the middle of the fuel supply pipe 110. The pressure detection device 30 is a device for measuring the fuel pressure inside the fuel supply pipe 110. The fuel pressure measured by the pressure detection device 30 is input to the injection control device 20.

  The injection control device 20 can acquire the pressure fluctuation at the time of fuel injection from the pressure detection device 30, and can calculate the actual fuel injection amount based on the fluctuation. That is, the pressure detection device 30 corresponds to the “injection amount detection unit” of the present invention. The correspondence relationship between the pressure fluctuation (for example, the amplitude of the pressure change) and the injection amount is obtained in advance through experiments or the like, and the correspondence relationship is stored in the injection control device 20 as a map. The injection control device 20 calculates the injection amount from the measured pressure fluctuation by referring to the map.

  In the present embodiment, the method for adjusting the drive voltage during fuel injection is different from the conventional control method. Prior to describing the control method according to the present embodiment, the conventional control method will be described with reference to FIGS.

  FIG. 7A is a graph showing a waveform of a signal generated as a command value for the fuel injection amount. The waveform is generated inside the injection control device 20 and input to a driver (not shown) for outputting a drive voltage to the piezoelectric actuator 500.

  In the example of FIG. 7A, a rectangular wave is obtained such that the magnitude of the voltage becomes the value V01 in the period from time t0 to time t20. When such a rectangular wave is input, the driver outputs a drive voltage to the piezoelectric actuator 500 so that the injection amount corresponds to the length of the period from time t0 to time t20.

  FIG. 7B shows the waveform of the drive voltage applied to the piezoelectric actuator 500. Although the waveform is drawn in a straight line, the actual waveform is a curve as shown in FIG.

  As shown in FIG. 7B, the driving voltage gradually increases after time t0 when the input of the rectangular wave to the driver is started. Along with this, the needle 400 moves toward the partition plate 210, and the opening degree of the injection port 310 gradually increases. Fuel begins to be injected from the injection port 310, and the injection rate gradually increases.

  At the subsequent time t10, the drive voltage becomes the maximum value (value V10). The opening degree of the injection port 310 is maximized, and the injection rate is also maximized. At this time, the upper end of the needle 400 is in contact with the partition plate 210.

  After time t10, the state where the injection rate is maximum is maintained. The driving voltage at this time is maintained substantially constant at the value V10 (in practice, gradually decreases). Meanwhile, fuel injection at the maximum injection rate is continued.

  The drive voltage gradually decreases after time t20 when the input of the rectangular wave to the driver is completed. Along with this, the needle 400 moves toward the valve seat 320 side, and the opening of the injection port 310 gradually decreases. The fuel injection rate gradually decreases and becomes 0 at the same time as the needle 400 abuts the valve seat 320 (time t30).

  The fuel injection amount is approximately proportional to the area of the figure surrounded by the graph of FIG. Also, the longer the pulse width of the rectangular wave shown in FIG. 7A, that is, the length of the period during which the voltage is the value V01, the greater the actual injection amount. The injection control device 20 stores the relationship between the injection amount and the pulse width as a map. The injection control device 20 inputs an injection command value (target injection amount), which is a command value for the injection amount, to the driver as a rectangular wave having a pulse width corresponding thereto. In the following description, “injection command value” is used as a word indicating the pulse width of the rectangular wave input to the driver.

  In FIG. 7B, a period from time t0 to time t10 is a period in which the drive voltage applied to the piezoelectric actuator 500 increases. Since this period can also be said to be a period during which electric charges are accumulated in the piezoelectric actuator 500, the period is also referred to as a “charging period” below.

  The period from time t10 to time t20 is a period in which the drive voltage applied to the piezoelectric actuator 500 is maintained substantially constant. Hereinafter, this period is also referred to as “maintenance period”.

  A period from time t20 to time t30 is a period in which the drive voltage applied to the piezoelectric actuator 500 decreases. Since this period can also be said to be a period during which electric charges are discharged from the piezoelectric actuator 500, the period will also be referred to as a “discharge period” hereinafter.

  When the injection amount from the fuel injection valve 10 is made very small, the injection command value becomes small. For this reason, as shown in FIG. 8, there may be a case where the discharge is started before the drive voltage reaches the value V10. In the example of FIG. 8, the charging period ends at time t08 prior to time t10, and the discharging period starts at the same time (without passing through the sustaining period). The maximum value of the applied drive voltage is a value V08 smaller than the value V10. The dotted line DL1 in FIG. 8B shows the same waveform as that in the graph in FIG.

  By the way, when the injection command value (pulse width) is relatively small as in the example of FIG. 8 and the discharge period starts simultaneously with the end of the charging period, the actual injection is performed even if the injection command value is increased. There is a tendency to produce areas where the amount does not increase.

  As shown in FIG. 9, when the injection command value is increased, the injection amount is increased to a value Q10 substantially in proportion to this. However, after that, even if the injection command value is increased, the injection amount does not increase. Thereafter, when the injection command value is further increased, the injection amount starts to increase again.

  Such a phenomenon is caused when the upper end surface 440 of the needle 400 collides with the lower surface 212 of the partition plate 210 when the needle 400 changes its position during the charging period.

  That is, the needle 400 rebounds due to the impact of the collision with the partition plate 210, and the position temporarily returns to the valve seat 320 side (valve closing side). Thereby, the opening degree of the injection port 310 becomes small, and an injection rate will fall temporarily.

  When the injection command value is large as in the example of FIG. 7, the needle 400 returns to its original position (position where it abuts on the partition plate 210) after the needle 400 rebounds as described above. For this reason, the influence of the rebound on the fuel injection amount is small. However, when the injection command value is small as in the example of FIG. 8, the fuel injection is finished before the bounced needle 400 returns to the original position, and therefore, the influence of the bounce on the fuel injection amount. It gets bigger. If the linearity between the injection command value and the actual injection amount is lost due to the bounce, it becomes difficult to accurately control the injection amount from the fuel injection valve 10.

  FIG. 10 shows examples of actual drive voltage waveforms corresponding to various injection command values. Of these waveforms, the waveform indicated by line G20 is the waveform of the drive voltage corresponding to the largest injection command value. In the waveform, the period from time t0 to time t10 is a charging period, and the drive voltage reaches the maximum value at time t10. Further, a period from time t10 to time t20 is a sustain period, and a period after time t20 is a discharge period. That is, it can be said that the line G20 in FIG. 10 shows the actual waveform in FIG.

  Of the waveforms shown in FIG. 10, the waveform indicated by line G <b> 10 is the waveform of the drive voltage corresponding to the smallest injection command value. The plurality of waveforms shown between the line G10 and the line G20 are obtained by drawing the waveform of the drive voltage corresponding to each injection command value while increasing the injection command value by a certain value. .

  All of the waveforms shown in FIG. 10 other than those shown by the line G20 correspond to relatively small injection command values, and no sustain period exists. That is, the waveform is such that the discharging period starts at the same time as the charging period ends.

  FIG. 11 shows the change over time in each injection rate when the drive voltage shown in FIG. 10 is input to the piezoelectric actuator 500. Among these plural waveforms, what is indicated by a line G21 is a change over time in the injection rate when the drive voltage indicated by the line G20 in FIG. 10 is input. Also, what is indicated by a line G11 is a change over time in the injection rate when the drive voltage indicated by the line G10 in FIG. 10 is input. The fuel injection amount is equal to the area of each figure surrounded by each waveform.

  As already described, the plurality of waveforms shown in FIG. 10 are drawn while increasing the injection command value by a certain value. Therefore, the waveforms of the respective injection rates shown in FIG. 11 should also be drawn at equal intervals. However, as in the part surrounded by the dotted line A2 in FIG. 11, the interval between the waveforms is very narrow in some parts. This indicates that the amount of injection (that is, the area of each graph) does not change much even if the injection command value is changed as a result of the rebound of the needle 400 as described above.

  Furthermore, when the injection rate increases as in the portion surrounded by the dotted line A1 in FIG. 11, the waveform may pulsate. This is considered to be a phenomenon that occurs due to the relatively long period (charge period) during which the needle 400 moves. When such pulsation occurs, it becomes more difficult to accurately control the injection amount from the fuel injection valve 10.

  In the injection control device 20 according to the present embodiment, control different from the conventional control is performed in order to prevent the needle 400 from rebounding and pulsation of the injection rate as described above. The contents of the control will be described with reference to FIG.

  FIG. 2 is a view similar to FIG. 7 and FIG. That is, FIG. 2A shows a waveform of a rectangular wave input to a driver (not shown), and FIG. 2B shows a waveform when the above waveform is input. 5 is a waveform of a drive voltage applied to the piezoelectric actuator 500. The waveform of the rectangular wave shown in FIG. 2A is the same as the waveform of the rectangular wave shown in FIG. Therefore, the waveform of the drive voltage shown in FIG. 2B is the waveform of the drive voltage applied to the piezoelectric actuator 500 when the injection command value is the same as the example of FIG. The dotted line DL1 in FIG. 2B shows the same waveform as the graph in FIG. 7B.

  Unlike the conventional control described with reference to FIGS. 7 and 8, in this embodiment, when the injection command value is equal to or less than a predetermined threshold, the magnitude of the applied drive voltage does not exceed the value V05. Adjustments are made as follows.

  Here, the “predetermined threshold value” is an injection command value (pulse width of a rectangular wave) that matches the length of the period from time t0 to time t10 in FIG. That is, when the conventional control shown in FIG. 7 or the like is performed, the injection command value is such that the discharge is performed immediately after the applied drive voltage increases to V10. However, the “predetermined threshold value” is not necessarily a value as described above. It may be set to a value shorter than the length of the period from time t0 to time t10, or may be set to a value longer than the length of the period from time t0 to time t10.

  As shown in FIG. 2B, also in the present embodiment, the drive voltage increases with the same slope as that of the dotted line DL1 after time t0. However, when the drive voltage reaches the value V05 at time t05, the drive voltage is maintained at the value V05 thereafter. Thereafter, when the input of the rectangular wave to the driver is completed at time t08, the discharge is started. The driving voltage gradually decreases from the value V05 and finally becomes zero.

  The value V05 set as the upper limit of the drive voltage is a value smaller than the value V10 and larger than 0. For this reason, the needle 400 does not move to a position corresponding to the driving voltage of the value V10, that is, a position where it abuts on the partition plate 210 (maximum injection position), and to a position closer to the valve seat 320 than that. Only move. The position of the needle 400 corresponding to the drive voltage of the value V05 corresponds to the “suppressed injection position” of the present invention.

  As described above, as a result of the operation of the piezoelectric actuator 500 being restricted by adjusting the drive voltage, the needle 400 does not move over the entire movable range, but operates within a range that does not exceed the suppression injection position. Become. As a result, the occurrence of a phenomenon in which the needle 400 collides with the partition plate 210 and rebounds is suppressed.

  When the injection command value is very short and shorter than the length of the period from time t0 to time t05, the discharge is started before the drive voltage reaches the value V05. For this reason, the operation of the needle 400 is the same as the operation when the conventional control is performed.

  Further, when the injection command value exceeds the predetermined threshold value, the control for limiting the drive voltage to the value V05 or less is not performed as described above. In this case, similarly to the conventional control described with reference to FIG. 7, the drive voltage increases to the value V10. That is, the needle 400 moves to the maximum injection position where the injection rate is maximized.

  As a result of the control as described above, the relationship between the injection command value and the injection amount in the present embodiment is not as shown in FIG. 9, but as shown in FIG. The dotted line DL2 in FIG. 3 shows the same waveform as the graph in FIG. Further, in FIG. 3, the above-described threshold value for the injection command value (an injection command value that matches the length of the period from time t0 to time t10) is shown as a value TM10.

  In the present embodiment, when the injection command value is smaller than the value TM10, the drive voltage is limited to the value V05 or less as described above. For this reason, compared with the case where the conventional control is performed, the injection amount is smaller as indicated by the arrow AR1. As is apparent from the waveform of the graph shown in FIG. 3, the relationship between the injection command value and the injection amount is substantially proportional, and the linearity is maintained. Accordingly, it is easier to control the injection amount from the fuel injection valve 10 accurately (so as to be in accordance with the injection command value) compared to the conventional art.

  FIG. 4 is a diagram similar to FIG. 10 and shows examples of waveforms of actual drive voltages corresponding to various injection command values when the control according to the present embodiment is performed. Of these multiple waveforms, the waveform indicated by line G40 is the waveform of the drive voltage corresponding to the largest injection command value. Further, what is indicated by a line G30 is a waveform of the drive voltage corresponding to the smallest injection command value. The plurality of waveforms shown between the line G30 and the line G40 are obtained by drawing the waveform of the drive voltage corresponding to each injection command value while increasing the injection command value by a certain value. .

  In the control according to the present embodiment, the applied drive voltage is limited to a value V05 or less. For this reason, in any of the waveforms shown in FIG. 4, the charging period ends at time t05 at the latest.

  FIG. 5 is a diagram similar to FIG. 11, and shows the time variation of each injection rate when the drive voltage shown in FIG. 4 is input to the piezoelectric actuator 500. Among these plural waveforms, what is indicated by a line G41 is a change over time in the injection rate when the drive voltage indicated by the line G40 in FIG. 4 is input. Also, what is indicated by a line G31 is a change over time in the injection rate when the drive voltage indicated by the line G30 in FIG. 4 is input. Also in FIG. 5, the fuel injection amount is equal to the area of each figure surrounded by each waveform.

  In the graph of FIG. 5, the pulsation of the injection rate as shown by the dotted line A1 of FIG. 11 does not occur. Further, there is no region where the interval between the injection rate waveforms is locally narrow, as indicated by the dotted line A2 in FIG. This is because the charging period is shortened due to the limitation of the driving voltage, and the collision between the needle 400 and the partition plate 210 is suppressed.

  Details of specific processing performed in the injection control device 20 will be described with reference to FIG. The series of processes shown in FIG. 6 is a process performed for setting the upper limit value of the drive voltage, and is repeatedly executed every time a predetermined period elapses. In parallel with this processing, fuel injection in the internal combustion engine is also repeatedly performed.

  In first step S01, it is determined whether or not the injection command value is equal to or less than a threshold value (value TM10). That is, it is determined whether or not the injection command value is equal to or shorter than the length of the period from time t0 to time t10.

  As already described, in the injection control device 20, the relationship between the injection amount and the pulse width as shown in FIG. 3 is stored in advance as a map. This relationship changes according to the fuel pressure inside the fuel injection valve 10. For this reason, the injection control device 20 stores a plurality of maps corresponding to the fuel pressure.

  In the injection control device 20, an appropriate map is selected based on the pressure measured by the pressure detection device 30. Thereafter, based on the map, a necessary injection amount (target value of the injection amount) is converted into an injection command value. The injection command value to be compared with the value TM10 in step S01 is calculated by the above method.

  If the injection command value is equal to or less than the value TM10, the process proceeds to step S02. In step S02, the upper limit value of the drive voltage is changed from the value V10 to the value V05. Thereafter, as described with reference to FIG. 2, the magnitude of the drive voltage applied to the piezoelectric actuator 500 falls within the range from 0 to the value V05. Thereafter, the fuel injection valve 10 performs fuel injection in a state where the drive voltage is limited in this way.

  In step S03 following step S02, the actual injection amount is calculated. As already described, the calculation is performed based on the pressure variation measured by the pressure detection device 30.

  In step S04 following step S03, it is determined whether or not the deviation of the injection amount is within a predetermined allowable range. The deviation of the injection amount here is an absolute value of the difference between the actual injection amount from the fuel injection valve 10, the injection amount calculated based on the map shown in FIG. If the deviation of the injection amount is within the allowable range, the process proceeds to step S05.

  In step S05, the map used for calculation of the injection amount command value in step S01 is updated. Specifically, the map is rewritten so that the injection amount value corresponding to the current injection command value becomes the actual injection amount value calculated in step S03. As a result, even when the state of the fuel injection valve 10 changes due to deterioration over time, the actual injection amount is suppressed from greatly deviating from the injection amount command value.

  In step S04, when the deviation of the injection amount is not within the predetermined allowable range, the process proceeds to step S06. The transition to step S06 means that the relationship between the injection command value and the injection amount is not linear as shown in FIG. 3 even when the drive voltage is limited to be equal to or lower than the upper limit value (value V05). That is. In other words, the set upper limit value (value V05) is not appropriate. Therefore, in step S06, the upper limit value is corrected.

  For example, when the actual injection amount is smaller than the injection amount corresponding to the injection amount command value, correction is performed to increase the upper limit value. On the contrary, when the actual injection amount is larger than the injection amount corresponding to the injection amount command value, correction is performed to decrease the upper limit value. Thereafter, the processes after step S02 are repeated. As a result of such correction of the upper limit value, the deviation of the injection amount gradually decreases, and the fuel injection amount approaches a more accurate value.

  Thus, in the present embodiment, the upper limit value of the drive voltage is changed based on the actual injection amount detected by the pressure detection device 30. In other words, the suppression injection position that is the upper end (the position when closest to the partition plate 210) in the range in which the needle 400 can move is changed. Since the suppression injection position is changed based on the actual injection amount, the relationship between the injection command value and the injection amount can be made closer to linearity more reliably.

  If the injection command value exceeds the value TM10 in step S01, the series of processes shown in FIG. In this case, the upper limit value of the drive voltage is not limited, and is applied to the piezoelectric actuator in the range from 0 to the value V10. That is, the same control as the conventional one described with reference to FIGS. 7 and 8 is performed.

  In the present embodiment, the actual fuel injection amount is calculated based on the pressure fluctuation measured by the pressure detection device 30. Instead of such an aspect, the fuel injection amount may be calculated or measured by another method. For example, the moving speed of the needle 400 may be measured, and the fuel injection amount may be calculated based on the measurement result.

  Further, the upper limit value of the drive voltage may be adjusted based on parameters other than the actual injection amount. For example, the injection rate characteristic may be calculated based on the moving speed of the needle 400, and the upper limit value of the drive voltage may be adjusted based on the injection rate characteristic.

  The actuator mounted in the fuel injection valve 10 may be a piezoelectric actuator made of a piezo element as in the present embodiment, or may be an actuator made of a solenoid. In this case, the injection control device adjusts the operating range of the needle 400 by limiting the magnitude of the current supplied to the solenoid.

  When the fuel injection valve 10 is provided in each of a plurality of cylinders of the vehicle and these controls are performed by the injection control device 20, the waveform of the pressure detected for each fuel injection valve 10 (pressure detection device 30). The control may be performed so as to reduce the difference in the injection amount between the cylinders by comparing the waveforms detected in (1). For example, the waveform of the rectangular wave input to the fuel injector 10 may be adjusted for each cylinder based on the detected pressure waveform. Specifically, the valve opening period and the valve closing period may be calculated based on the peak value of the pressure waveform and the rising or falling timing, and the waveform of the rectangular wave may be corrected.

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In other words, those specific examples that have been appropriately modified by those skilled in the art are also included in the scope of the present invention as long as they have the characteristics of the present invention. For example, the elements included in each of the specific examples described above and their arrangement, materials, conditions, shapes, sizes, and the like are not limited to those illustrated, but can be changed as appropriate. Moreover, each element with which each embodiment mentioned above is provided can be combined as long as technically possible, and the combination of these is also included in the scope of the present invention as long as it includes the features of the present invention.

10: Fuel injection valve 20: Injection control device 30: Pressure detection device 310: Injection port 400: Needle 500: Piezoelectric actuator

Claims (3)

An injection control device (20) for controlling the operation of a fuel injection valve (10) in an internal combustion engine,
The fuel injection valve is configured to move a valve body (400) for changing the opening of the injection port (310) by an actuator (500), thereby changing the fuel injection rate.
When the target injection amount, which is the target value of the fuel injection amount from the fuel injection valve, is larger than a predetermined threshold injection amount, the valve body is moved to the maximum injection position where the injection rate becomes maximum. To control the operation of the actuator,
When the target injection amount is equal to or less than the threshold injection amount,
Injection control characterized in that the operation of the actuator is limited so that the valve body operates within a range that does not exceed a suppression injection position preset as a position where the opening is smaller than the maximum injection position. apparatus. An injection amount detector (30) for detecting the amount of fuel injected from the fuel injection valve;
The injection control device according to claim 1, wherein the suppression injection position is changed based on an injection amount detected by the injection amount detection unit.   The injection control device according to claim 2, wherein the injection amount detection unit detects an injection amount based on a fuel pressure fluctuation inside the fuel injection valve.

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