JP2009079485A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve capable of suppressing inappropriate transition of a fuel injection rate due to inner needle bounce. <P>SOLUTION: The fuel injection valve 2 consists of an inner injection hole group 14, an outer injection hole group 15, a control chamber 20, an inner needle 12 and an outer needle 13. The inner needle opens/closes the injection hole of the inside injection hole group. The outer needle opens/closes the injection hole of the outside injection hole group. Lifts of the inner needle and outer needle are controlled by pressure of fuel in the control chamber. The fuel injection valve is equipped with a pressure control means for controlling pressure in the control chamber so as to make the pressure difference before/after pressure increase not higher than critical pressure difference when the pressure of fuel in the control chamber is increased during the increase of the needle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

    The present invention relates to a fuel injection valve.

  In recent years, as a fuel injection valve used in an internal combustion engine (particularly, a diesel engine), two injection hole groups are provided, fuel injection from only one injection hole group, and fuel injection from both injection hole groups, Fuel injection valves that can be used properly have been developed. In such a fuel injection valve, in general, in a low-load operation state, spray is atomized by injecting fuel only from one nozzle hole group having a small diameter and in a high-load operation state, In addition, it is possible to inject a large amount of fuel in a short time by injecting fuel from the nozzle hole group having a large nozzle hole diameter. As a result, it is possible to perform appropriate fuel injection according to the engine operating state, and it is possible to reduce harmful substances contained in the exhaust gas and to achieve low fuel consumption and high output of the internal combustion engine.

  As such a fuel injection valve, for example, a cylindrical outer needle and an inner needle coaxially provided inside the outer needle are provided, and the outer needle opens and closes the injection hole of one injection hole group. A fuel injection valve in which an inner needle opens and closes the nozzle holes of the other nozzle hole group is known (for example, Patent Document 1).

  In particular, in the fuel injection valve disclosed in Patent Document 1, the outer needle and the inner needle are made to flow out of the control chamber provided on the rear end side of the outer needle and the inner needle to reduce the pressure in the control chamber. Are raised (lifted) sequentially. Specifically, when the fuel is caused to flow out from the control chamber, the outer needle is first started to rise, and fuel injection is performed only from the injection holes of one injection hole group. After that, when the outer needle is raised to a certain extent, the rear end surface of the outer needle comes into contact with the lower surface of the protrusion provided behind the inner needle, and then the outer needle and the inner needle are raised together. Thus, fuel injection from the nozzle holes of both nozzle hole groups is performed. However, if the outflow of fuel from the control chamber stops before the outer needle is raised to some extent, the inner needle will not start to rise, and therefore one of the injections from the start to the end of fuel injection will not start. Fuel injection is performed only from the nozzle holes of the hole group.

JP 2005-320904 A JP 2001-241370 A

  By the way, as described above, in the fuel injection valve disclosed in Patent Document 1, it is intended that the outer needle and the inner needle are integrally raised after the outer needle is raised to some extent. Thus, by raising both needles, the transition of the fuel injection rate from the fuel injection valve can be optimized. Further, the opening time of the fuel injection valve with respect to the required fuel injection amount is set on the assumption that both the needles rise as described above.

  However, when the rear end surface of the outer needle collides with the lower surface of the protrusion provided behind the inner needle after the outer needle has raised to some extent, almost all the momentum of the outer needle is transmitted to the inner needle. Therefore, only the inner needle then rises and the rise of the outer needle may stop (inner needle bounce). In this case, after the outer needle rises to some extent, the outer needle and the inner needle do not rise together. In particular, when the inner needle bounce occurs, the fuel pressure in the pressure control chamber subsequently vibrates up and down, and accordingly, the lift of the inner needle also vibrates up and down. For this reason, the transition of the fuel injection rate from the fuel injection valve cannot be optimized, and the amount of fuel actually injected from the fuel injection valve is different from the required fuel injection amount. End up.

  Therefore, an object of the present invention is to provide a fuel injection valve that can suppress an inappropriate transition of the fuel injection rate due to the inner needle bounce.

In order to solve the above-described problem, the first invention includes a first nozzle hole group and a second nozzle hole group, a control chamber, a first needle and a second needle, and the first needle is a first jet. In a fuel injection valve that opens and closes the nozzle holes of the hole group, the second needle opens and closes the nozzle holes of the second nozzle hole group, and the lift of the first needle and the second needle is controlled by the fuel pressure in the control chamber, Pressure control means is further provided for controlling the pressure in the control chamber so that when the pressure of the fuel in the control chamber rises while the needle is raised, the differential pressure before and after the pressure rise becomes equal to or lower than the limit differential pressure.
According to the first invention, when the fuel pressure in the control chamber rises while the needle is rising, the pressure in the control chamber is controlled so that the differential pressure before and after the pressure rise becomes equal to or lower than the limit differential pressure. For this reason, even if the inner needle bounce occurs and the pressure in the control chamber suddenly rises, the degree of the rise is small, and hence the subsequent pressure fluctuation of the fuel in the control chamber is suppressed.

  According to a second aspect, in the first aspect, the pressure control means includes a variable volume chamber communicating with the control chamber, and the volume of the chamber is increased as the differential pressure before and after the pressure increase is increased.

  According to a third invention, in the first invention, the pressure control means includes a communication passage communicating with the control chamber and the fuel outflow passage, and an on-off valve for opening and closing the communication passage, and the on-off valve is configured with the pressure The valve is opened when the differential pressure before and after the rise is greater than the limit differential pressure.

  In order to solve the above-mentioned problems, in the fourth invention, the first nozzle hole group and the second nozzle hole group, the control chamber, the first needle and the second needle are provided, and the first needle is the first nozzle. In a fuel injection valve that opens and closes the nozzle holes of the hole group, the second needle opens and closes the nozzle holes of the second nozzle hole group, and the lift of the first needle and the second needle is controlled by the fuel pressure in the control chamber, Pressure control means is provided for controlling the pressure in the control chamber so that when the pressure of the fuel in the control chamber rises while the needle is rising, the pressure rise speed is less than the limit speed.

  According to a fifth aspect, in the fourth aspect, the pressure control means includes a variable volume chamber communicating with the control chamber, and the volume of the chamber is increased at a speed corresponding to the pressure increase speed.

  According to a sixth aspect, in the fourth aspect, the pressure control means includes a communication passage communicating with the control chamber and the fuel outflow passage, and an opening / closing valve for opening / closing the communication passage, and the opening / closing valve includes the pressure The valve is opened when the ascending speed is faster than the limit speed.

  According to a seventh aspect, in the third or sixth aspect, a direct communication path that directly communicates with the control chamber is provided on one side of the on-off valve, and the other side communicates with the control chamber via an orifice. An indirect communication passage is provided, and the on-off valve opens when the differential pressure between the pressure received from the fuel in the direct communication passage and the pressure received from the fuel in the indirect communication passage is greater than a certain differential pressure.

  In an eighth invention, in any one of the first to seventh inventions, either one of a fuel inflow passage and a fuel outflow passage is selectively communicated with the control chamber.

  According to the present invention, it is possible to suppress the pressure fluctuation of the fuel in the control chamber that occurs after the occurrence of the inner needle bounce, and therefore it is possible to suppress an inappropriate transition of the fuel injection rate due to the inner needle bounce.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a fuel injection valve according to a first embodiment of the present invention, in which only the outer needle is raised on the left side of FIG. 1, and both the outer needle and inner needle are on the right side of FIG. It shows a raised state.

  The fuel injection device of this embodiment includes a common rail (fuel accumulator) 1 that is supplied with high-pressure fuel from a fuel tank by a high-pressure pump, an engine combustion chamber or an intake port (not shown) that is supplied with high-pressure fuel from the common rail 1. The fuel injection valve 2 which injects a fuel in the inside and the fuel tank (fuel recovery part) 3 which stores the fuel which should be injected are provided. Moreover, the fuel pressure in the common rail 1 is kept at a relatively high pressure (for example, 80 MPa to 140 MPa).

  As shown in FIG. 1, the fuel injection valve 2 is a cylindrical nozzle body 11, a solid inner needle 12 disposed coaxially with the nozzle body 11, and a coaxial arrangement with the nozzle body 11. And a hollow outer needle 13. The nozzle body 11 has a hollow space therein, and both needles 12 and 13 are accommodated in the hollow space. The outer needle 13 has a hollow space inside, and the inner needle 12 is received in the hollow space. Two nozzle hole groups 14 and 15 are provided at the tip of the nozzle body 11. Of these nozzle hole groups, the nozzle holes of the inner nozzle hole group 14 are opened and closed by the inner needle 12 and the outer nozzle hole group 15. The nozzle hole is opened and closed by the outer needle 13. Each nozzle hole group 14 and 15 is constituted by one or more nozzle holes. In the present specification, the lower side of FIG. 1, that is, the side where the nozzle body 11 is provided with the nozzle hole groups 14 and 15 is the lower side, and the upper side of FIG. 1, ie, the side where the nozzle hole group is not provided. It demonstrates as upper.

  A nozzle chamber 16 through which fuel to be injected from the fuel injection valve 2 flows is formed between the inner surface of the nozzle body 11 and the outer peripheral surface of the outer needle 13 and the outer surface of the inner needle 12. The nozzle chamber 16 communicates with the high-pressure fuel inflow passage 17 that communicates with the common rail 1 and also communicates with the nozzle holes of the nozzle hole groups 14 and 15 provided at the tip of the nozzle body 11.

  The inner needle 12 and the outer needle 13 are slidable in the axial direction thereof, and the injection holes of the injection hole groups 14 and 15 are opened and closed by the sliding of the needles 12 and 13 in the axial direction. That is, when the needles 12 and 13 are raised (lifted), each nozzle hole of the inner nozzle hole group 14 and the outer nozzle hole group 15 and the nozzle chamber 16 communicate with each other, and fuel is injected from each nozzle hole. On the other hand, the needles 12 and 13 are in the lowest position (not raised), and the tips of the needles 12 and 13 are placed on a sheet formed on the inner wall surface of the tip of the nozzle body 11. In some cases, each nozzle hole is closed, so that the fuel injection from each nozzle hole is stopped.

  The inner needle 12 is biased downward in the axial direction by the inner needle spring 18 so as to close each nozzle hole of the inner nozzle hole group 14. The outer needle 13 is urged downward in the axial direction by the outer needle spring 19 so as to close each nozzle hole of the outer nozzle group 15. A pressure control chamber 20 is defined between the upper end surfaces of the needles 12 and 13 and the inner surface of the nozzle body 11. Fuel is supplied into the pressure control chamber 20, and both needles 12 and 13 receive a downward force (in the direction of closing the nozzle hole) due to the fuel pressure in the pressure control chamber 20. That is, the inner needle 12 and the outer needle 13 receive a downward force from the springs 18 and 19 and the fuel in the pressure control chamber 20. On the contrary, the inner needle 12 and the outer needle 13 receive upward force (injection hole opening direction) due to the fuel pressure in the nozzle chamber 16.

  Therefore, in the inner needle 12, the downward force that the inner needle 12 receives due to the fuel pressure in the inner needle spring 18 and the pressure control chamber 20 is the same as the upward force that the inner needle 12 receives due to the fuel pressure in the nozzle chamber 16. When it is present or larger, the inner needle 12 is lowered or each nozzle hole of the inner nozzle hole group 14 is kept closed. Conversely, when the downward force received by the inner needle 12 due to the fuel pressure in the inner needle spring 18 and the pressure control chamber 20 is smaller than the upward force received by the inner needle 12 due to the fuel pressure in the nozzle chamber 16, Needle 12 is raised.

  The same can be said for the outer needle 13. The downward force received by the outer needle 13 by the fuel pressure in the outer needle spring 19 and the pressure control chamber 20 is the upward force received by the outer needle 13 by the fuel pressure in the nozzle chamber 16. When the force is equal to or greater than the above-described force, the outer needle 13 is lowered or the nozzle holes of the outer nozzle hole group 15 are kept closed. On the contrary, when the downward force received by the outer needle 13 due to the fuel pressure in the outer needle spring 19 and the pressure control chamber 20 is smaller than the upward force received by the outer needle 13 due to the fuel pressure in the nozzle chamber 16, Needle 13 is raised.

  In the present embodiment, the urging force of the outer needle spring 19 is weaker than the urging force of the inner needle spring 18. Accordingly, the downward force received by the outer needle 13 by the fuel pressure in the outer needle spring 19 and the pressure control chamber 20 is the downward force received by the inner needle 12 by the fuel pressure in the inner needle spring 18 and the pressure control chamber 20. If the fuel pressure in the pressure control chamber 20 decreases, the outer needle 13 starts to rise before the inner needle 12.

  The pressure control chamber 20 communicates with a fuel inflow / outflow passage 21, and an orifice 22 is provided on the fuel inflow / outflow passage 21. The fuel inflow / outflow passage 21 communicates with the three-way valve 23, and the three-way valve 23 communicates with the high-pressure fuel inflow passage 17 and the fuel outflow passage 24. The high pressure fuel inflow passage 17 and the fuel outflow passage 24 communicate with the common rail 1 and the fuel tank 3, respectively. Therefore, when the three-way valve 23 is at a position where the fuel inflow / outflow passage 21 and the high pressure fuel inflow passage 17 are connected (hereinafter referred to as “fuel inflow position”), the three way valve 23, the fuel outflow / inflow passage from the high pressure fuel inflow passage 17. Fuel is caused to flow into the pressure control chamber 20 via 21. Therefore, the fuel pressure in the pressure control chamber 20 is raised to a high fuel pressure of the common rail 1 (hereinafter referred to as “rail pressure”). On the other hand, when the three-way valve 23 is at a position where the fuel inflow / outflow passage 21 and the fuel outflow passage 24 are connected (hereinafter referred to as “fuel outflow position”), the fuel inflow / outflow passage 21 and the three-way valve 23 are connected from the pressure control chamber 20. Then, the fuel flows out to the fuel outflow passage 24.

  Even when the three-way valve 23 is in the fuel inflow position and the fuel flows into the pressure control chamber 20, the three-way valve 23 is in the fuel outflow position and the fuel flows out of the pressure control chamber 20. However, inflow and outflow fuel passes through the orifice 22. Therefore, in any case, the fuel pressure in the pressure control chamber 20 does not change suddenly but gradually changes.

  The three-way valve 23 is controlled by a solenoid actuator that is controlled by an ECU (not shown). However, the means for controlling the three-way valve 23 may not be a solenoid actuator, but may be another type of actuator such as a piezoelectric element or a giant magnetostrictive element. If the fuel inflow / outflow passage 21 can be switched between the state in which the fuel inflow / outflow passage 21 is connected to the high pressure fuel inflow passage 17 and the state in which the fuel outflow / inflow passage 21 is connected to the fuel outflow passage 24, other valves, etc. can be used instead of the three-way valve. It may be used.

  In the fuel injection valve 2 configured as described above, when the fuel injection is to be performed, first, the three-way valve 23 in the fuel inflow position is switched to the fuel outflow position. As a result, the fuel in the pressure control chamber 20 flows out into the fuel tank 3 through the fuel inflow / outflow passage 21, the orifice 22, the three-way valve 23, and the fuel outflow passage 24. Along with this, the fuel pressure in the pressure control chamber 20 gradually decreases. First, the outer needle 13 having a weak spring biasing force starts to rise, and fuel injection from each nozzle hole of the outer nozzle hole group 15 is started. (The state on the left side of FIG. 1).

  If the three-way valve 23 continues to be maintained at the fuel outflow position even if the outer needle 13 rises to some extent, the fuel pressure in the pressure control chamber 20 further decreases, the inner needle 12 begins to rise, and the inner injection Fuel injection is also started from each nozzle hole of the hole group 14 (state on the right side in FIG. 1). Thereafter, when the three-way valve 23 is switched to the fuel inflow position, the fuel flows into the pressure control chamber 20 through the high-pressure fuel inflow passage 17, the three-way valve 23, the fuel inflow / outflow passage 21, and the orifice 22. As a result, the fuel pressure in the pressure control chamber 20 gradually rises, and both the inner needle 12 and the outer needle 13 are lowered, and the inner injection hole group 14 is first closed, and then the outer injection hole group 15 is closed. The fuel injection is terminated.

  On the other hand, if the three-way valve 23 is switched to the fuel inflow position before the outer needle 13 is raised to some extent, the fuel flows into the pressure control chamber 20, and the fuel pressure in the pressure control chamber 20 is accordingly increased. Rise gradually. As a result, the outer needle 13 is lowered, and finally the outer nozzle hole group 15 is closed, and fuel injection is terminated. In this case, fuel injection from the injection holes of the inner injection hole group 14 is not performed during fuel injection from the fuel injection valve 2. By controlling the three-way valve 23 in this way, a small amount of fuel can be injected from the fuel injection valve 2.

  FIG. 2 is a diagram showing the transition of the lift amount and the fuel injection rate of the needles 12 and 13 from the start to the end of fuel injection, and the solid lines in the figure indicate the injection holes of the outer injection hole group 15 and the inner injection hole group 14. The case where fuel injection is performed from both of the nozzle holes is shown, and the broken line in the figure shows the case where fuel injection is performed only from the nozzle holes of the outer nozzle group 15.

  As can be seen from FIG. 2, after the three-way valve 23 is switched to the fuel outflow position and fuel injection is started, the outer needle 13 is first raised, and fuel injection from the outer injection hole group 15 is started. As a result, the fuel injection rate increases. When the outer needle 13 rises to some extent (hx in FIG. 2), the fuel injection rate does not increase due to the rise of the outer needle 13, and the fuel injection rate becomes substantially constant. Thereafter, when the outer needle 13 is raised by a certain amount hy, the shoulder 31 provided at the rear end of the outer needle 13 and the lower surface of the annular protrusion 30 provided behind the inner needle 12 come into contact with each other, and the outer needle 13 The rise of 13 stops temporarily. Thereafter, both the outer needle 13 and the inner needle 12 begin to rise, and along with this, fuel injection is performed from the injection holes of the inner injection hole group 14, so that the fuel injection rate increases again. On the other hand, when the three-way valve 23 is switched to the fuel inflow position relatively early, the inner needle 12 does not rise, so that it does not rise again after the fuel injection rate becomes substantially constant as described above (FIG. Middle dashed line).

  Further, the fuel injection valve 2 of the present embodiment is provided with a bypass passage 35 that communicates with the pressure control chamber 20 and the fuel inflow / outflow passage 21 and bypasses the orifice 22. A cylinder 36 is provided in the middle of the bypass passage 35, and an open / close valve 37 for opening and closing the bypass passage 35 is provided in the cylinder 36.

  When the on-off valve 37 is moving downward (in the valve closing direction) in the cylinder 36, the bypass passage 35 is blocked by the on-off valve 37, and the flow of fuel through the bypass passage 35 is prohibited. On the other hand, when the on-off valve 37 moves upward (in the valve opening direction) in the cylinder 36, the bypass passage 35 is opened, and the fuel flow through the bypass passage 35 is allowed. The on-off valve 37 is urged downward by the on-off valve spring 38, that is, in the valve closing direction.

  Further, the fuel injection valve 2 of the present embodiment is provided with a delay pressure supply path 39 that communicates the end of the cylinder 36 opposite to the side where the bypass passage 35 is disposed and the pressure control chamber 20. The delay pressure supply passage 39 is provided with an orifice 40. Therefore, the pressure of the fuel in the delay pressure supply passage 39 is applied to one side of the on-off valve 37, and the pressure of the fuel in the bypass passage 35, that is, inside the pressure control chamber 20 is on the other side of the on-off valve 37. The fuel pressure is applied.

  For this reason, the on-off valve 37 has a downward force (in the valve closing direction) received by the on-off valve 37 by the fuel pressure in the on-off valve spring 38 and the delay pressure supply passage 39. When the upward force (opening direction) force that 37 receives is equal to or greater than the upward force, the on-off valve 37 is closed. On the contrary, the downward force received by the on-off valve 37 due to the fuel pressure in the on-off valve spring 38 and the delay pressure supply passage 39 is the upward force (opening direction) received by the on-off valve 37 by the fuel pressure in the pressure control chamber 20. When it is smaller than the force, the on-off valve 37 is opened.

  When fuel is not injected from the fuel injection valve 2, that is, when the three-way valve 23 is maintained at the fuel inflow position, both the pressure control chamber 20 and the delay pressure supply passage 39 are at rail pressure. For this reason, the downward force received by the on-off valve 37 due to the fuel pressure in the delay pressure supply passage 39 is equal to the upward force received by the on-off valve 37 due to the fuel pressure in the pressure control chamber 20. Since the spring 38 is biased downward, the on-off valve 37 is closed.

  In addition, when the fuel pressure in the pressure control chamber 20 is lowered by setting the three-way valve 23 to the fuel outflow position, the fuel pressure in the delay pressure supply path 39 is higher than the fuel pressure in the pressure control chamber 20. That is, the fuel pressure in the pressure control chamber 20 gradually decreases by setting the three-way valve 23 to the fuel outflow position, but the fuel pressure in the delay pressure supply passage 39 is controlled by the presence of the orifice 40. The fuel pressure in the chamber 20 decreases later than the fuel pressure. Therefore, in this case, the downward force received by the on-off valve 37 due to the fuel pressure in the on-off valve spring 38 and the delay pressure supply passage 39 is upward (the valve opening direction) received by the on-off valve 37 by the fuel pressure in the pressure control chamber 20. Therefore, the on-off valve 37 is maintained in a closed state.

  Thereafter, when the fuel pressure in the pressure control chamber 20 rises by setting the three-way valve 23 to the fuel inflow position, the fuel pressure in the delay pressure supply passage 39 becomes lower than the fuel pressure in the pressure control chamber 20. That is, the fuel pressure in the pressure control chamber 20 gradually increases by setting the three-way valve 23 to the fuel outflow position, but the fuel pressure in the delay pressure supply path 39 is controlled by the presence of the orifice 40. The fuel pressure rises later than the fuel pressure in the chamber 20. However, in this case, due to the presence of the orifice 22, the rate of increase of the fuel pressure in the pressure control chamber 20 is not so fast. For this reason, the differential pressure between the fuel pressure in the pressure control chamber 20 and the fuel pressure in the delay pressure supply path 39 is not so high. Therefore, the difference between the downward force received by the on-off valve 37 due to the fuel pressure in the delay pressure supply passage 39 and the upward force received by the on-off valve 37 due to the fuel pressure in the pressure control chamber 20 is the difference between the on-off valve spring 38. Therefore, the on-off valve 37 is maintained in a closed state.

  From the above, when both the needles 12 and 13 are operating normally during fuel injection from the fuel injection valve 2, the on-off valve 37 is always closed, There is no fuel flow.

  By the way, in order to achieve the ideal injection rate transition as described above, the outer needle 13 is raised by the predetermined amount hy, and the shoulder 31 of the outer needle 13 and the lower surface of the protrusion 30 of the inner needle 12 come into contact with each other. After that, the inner needle 12 and the outer needle 13 are integrated with each other in a state in which the lower surface of the protruding portion 30 of the inner needle 12 is in contact with the shoulder 31 of the outer needle 13, that is, in a mode in which the shoulder 31 pushes up the protruding portion 30. Need to rise.

  However, in practice, when the shoulder 31 of the outer needle 13 collides with the lower surface of the protrusion 30 of the inner needle 12, almost all the momentum of the outer needle 13 may be transmitted to the inner needle 12. . In this case, thereafter, only the inner needle 12 rapidly rises, and the rise of the outer needle 13 stops. That is, the outer needle 13 and the inner needle 12 do not rise together. Such a phenomenon is called inner needle bounce.

  FIG. 3 is a diagram illustrating changes in the fuel pressure and the needle lift amount in the pressure control chamber 20 when the inner needle bounce occurs. Time 0 in the figure indicates the time when the shoulder 31 of the outer needle 13 collides with the lower surface of the protrusion 30 of the inner needle 12. As shown in FIG. 3, when the inner needle bounce occurs, the inner needle 12 rises, and the fuel pressure in the pressure control chamber 20 rises rapidly with this. Thereafter, when the fuel pressure in the pressure control chamber 20 increases, the rise of the inner needle 12 is stopped by this, and then the inner needle 12 is lowered. The extent to which the inner needle 12 is lowered increases as the fuel pressure in the pressure control chamber 20 increases. Thereafter, the inner needle 12 vibrates.

  That is, when the inner needle bounce occurs, the fuel pressure in the pressure control chamber 20 subsequently vibrates up and down, and accordingly, the lift amount of the inner needle 12 also vibrates up and down. As a result, the transition of the fuel injection rate from the fuel injection valve 2 cannot be made appropriate as shown in FIG. If the fuel injection rate from the fuel injection valve cannot be controlled appropriately in this way, the combustion of the air-fuel mixture in the combustion chamber of the internal combustion engine will be worsened, resulting in a decrease in engine output, deterioration in fuel consumption and exhaust emission. Will be worsened.

  Here, in the fuel injection valve 2 of the present embodiment, when the inner needle bounce occurs as described above, when the inner needle 12 rises rapidly, the fuel pressure in the pressure control chamber 20 also rises abruptly. . In this case, the rising speed of the fuel pressure in the pressure control chamber 20 is fast. In this way, when the fuel pressure in the pressure control chamber 20 suddenly rises, the fuel pressure in the pressure control chamber 20 and the delay in the pressure control chamber 20 differ from the case where the rate of increase in the fuel pressure in the pressure control chamber 20 is not so fast as described above. The differential pressure from the fuel pressure in the pressure supply path 39 is large. Therefore, the difference between the downward force received by the on-off valve 37 due to the fuel pressure in the delay pressure supply passage 39 and the upward force received by the on-off valve 37 due to the fuel pressure in the pressure control chamber 20 is the difference between the on-off valve spring 38. Therefore, the on-off valve 37 is opened.

  That is, according to the fuel injection valve 2 of the present embodiment, when an inner needle bounce occurs while the needles 12 and 13 are raised, and the fuel pressure in the pressure control chamber 20 suddenly rises, the inner needle bounce occurs. The differential pressure between the fuel pressure in the delay pressure supply passage 39 substantially equal to the fuel pressure in the previous pressure control chamber 20 and the fuel pressure in the pressure control chamber 20 increased by the occurrence of the inner needle bounce is larger than the limit differential pressure. Then, the on-off valve 37 is opened, and the fuel in the pressure control chamber 20 flows out through the bypass passage 35. In other words, the differential pressure between the fuel pressure in the delay pressure supply passage 39 that is substantially equal to the fuel pressure in the pressure control chamber 20 before the occurrence of the inner needle bounce and the fuel pressure in the pressure control chamber 20 that has increased due to the occurrence of the inner needle bounce. The fuel pressure in the pressure control chamber 20 is controlled so that is less than the limit differential pressure.

  Here, the limit differential pressure can be arbitrarily set according to the elastic force of the on-off valve spring 38. However, the limit differential pressure is a predetermined time (period in which the fuel pressure is increased when the inner needle bounce occurs) when the fuel flows into the pressure control chamber 20 by setting the three-way valve 23 to the fuel inflow position. Is set to be larger than the fuel pressure in the pressure control chamber 20 (the amount of increase in the fuel pressure) that rises at the same time).

  In other words, the pressure difference between the fuel pressure in the pressure control chamber 20 that has risen during a predetermined period after the occurrence of the inner needle bounce and the fuel pressure in the delay pressure supply passage 39 that has risen during the same period is equal to or greater than a certain differential pressure. When the fuel pressure in the pressure control chamber 20 rises at such a speed, that is, when the increase speed of the fuel pressure in the pressure control chamber 20 becomes faster than the limit speed, the on-off valve 37 is opened. . In other words, according to the fuel injection valve 2 of the present embodiment, the fuel pressure in the pressure control chamber 20 is controlled so that the rising speed of the fuel pressure in the pressure control chamber 20 is equal to or lower than the limit speed.

  Here, the limit speed can be arbitrarily set according to the elastic force of the on-off valve spring 38. However, the limit speed is set to a speed higher than the rate of increase of the fuel pressure in the pressure control chamber 20 when the fuel flows into the pressure control chamber 20 by setting the three-way valve 23 to the fuel inflow position.

  As described above, according to the fuel injection valve 2 of the present embodiment, even if the inner needle bounce occurs, the fuel pressure in the pressure control chamber 20 does not increase as shown in FIG. It does not descend as shown in 3. Therefore, the vibration of the fuel pressure in the pressure control chamber 20 and the vibration of the lift amount of the inner needle 12 generated thereafter are also suppressed as compared with the case shown in FIG. As a result, the fuel injection amount from the fuel injection valve 2 can be controlled relatively appropriately, and the decrease in engine output, the deterioration in fuel consumption, and the deterioration in exhaust emission can be suppressed.

  In the above-described embodiment, the fuel flows into the pressure control chamber 20 and the fuel flows out from the pressure control chamber 20 through the same passage (the fuel inflow / outflow passage 21). However, the fuel injection valve 2 may not have such a configuration, and a passage through which fuel flows into the pressure control chamber 20 and a passage through which fuel flows out from the pressure control chamber 20 may be provided separately.

  Next, the fuel injection valve 2 'according to the second embodiment of the present invention will be described with reference to FIG. The configuration of the fuel injection valve 2 ′ shown in FIG. 4 is basically the same as the configuration of the fuel injection valve 2 of the first embodiment shown in FIG. 1. Therefore, the description of the same configuration is omitted.

  In the fuel injection valve 2 ′ of the present embodiment, a cylinder 45 is provided instead of the bypass passage 35, the on-off valve 37, and the like, unlike the fuel injection valve 2 of the first embodiment. A piston 46 slidable in the cylinder 45 is disposed in the cylinder 45, and the piston 46 is urged to one side in the cylinder 45 by a piston spring 47.

  One end of the cylinder 45 communicates with the pressure control chamber 20 via the control chamber communication passage 48, and the other end communicates with the delay pressure supply path 49. The delay pressure supply passage 49 is provided with an orifice 50. Accordingly, the fuel pressure in the delay pressure supply passage 39 is applied to one side (upper side) of the piston 46, and the fuel pressure in the pressure control chamber 20 is applied to the other side (lower side) of the piston 46. .

  Therefore, when the downward force received by the piston 46 due to the fuel pressure in the piston spring 47 and the delay pressure supply passage 49 is greater than the upward force received by the piston 46 due to the fuel pressure in the pressure control chamber 20, the piston 46 is Can be lowered. As a result, the volume of the chamber 51 defined by the cylinder 45 and the piston 46 and communicating with the pressure control chamber 20 is reduced. Conversely, when the downward force received by the piston 46 due to the fuel pressure in the piston spring 47 and the delay pressure supply passage 49 is smaller than the upward force received by the piston 46 due to the fuel pressure in the pressure control chamber 20, the piston 46. Is raised, and thus the volume of the chamber 51 is increased.

  In the fuel injection valve 2 ′ configured in this way, when fuel injection is not performed from the fuel injection valve 2 ′, that is, when the three-way valve 23 is maintained at the fuel inflow position, the pressure control chamber 20 and the delay Both of the pressure supply paths 50 have rail pressure. For this reason, the downward force received by the piston 46 due to the fuel pressure in the delay pressure supply passage 50 is equal to the upward force received by the piston 46 due to the fuel pressure in the pressure control chamber 20, and the piston 47 is a piston spring 47. Therefore, the piston 47 is lowered, so that the volume of the chamber 51 is reduced.

  Further, when the fuel pressure in the pressure control chamber 20 is lowered by switching the three-way valve 23 to the fuel outflow position, the fuel pressure in the delay pressure supply passage 49 is greater than the fuel pressure in the pressure control chamber 20 due to the presence of the orifice 40. Is also expensive. Accordingly, in this case, the downward force received by the piston 46 due to the fuel pressure in the piston spring 47 and the delay pressure supply passage 39 is larger than the upward force received by the piston 46 due to the fuel pressure in the pressure control chamber 20. 46 is maintained in a lowered state, so that the volume of the chamber 51 is small.

  Thereafter, when the fuel pressure in the pressure control chamber 20 rises by switching the three-way valve 23 to the fuel inflow position, the fuel pressure in the delay pressure supply passage 49 becomes lower than the fuel pressure in the pressure control chamber 20. However, in this case, due to the presence of the orifice 22, the rising speed of the fuel pressure in the pressure control chamber 20 is not so fast. For this reason, the differential pressure between the fuel pressure in the pressure control chamber 20 and the fuel pressure in the delay pressure supply passage 49 is not very high. Therefore, the difference between the downward force received by the piston 46 due to the fuel pressure in the delay pressure supply passage 39 and the upward force received by the piston 46 due to the fuel pressure in the pressure control chamber 20 is larger than the biasing force of the piston spring 47. Thus, the piston 46 is maintained in a lowered state.

  As described above, when both the needles 12 and 13 are operating normally during fuel injection from the fuel injection valve 2 ′, the piston 46 is always in a lowered state, and the volume of the chamber 51 remains small. Maintained.

  However, when the inner needle bounce occurs as described above, when the inner needle 12 rapidly rises, the fuel pressure in the pressure control chamber 20 also suddenly rises, and the fuel pressure in the pressure control chamber 20 and the delay pressure supply path The differential pressure from the fuel pressure in 49 is large. Therefore, the difference between the downward force received by the piston 46 due to the fuel pressure in the delay pressure supply passage 49 and the upward force received by the piston 46 due to the fuel pressure in the pressure control chamber 20 is greater than the biasing force of the piston spring 47. Therefore, the piston 46 rises.

  When the piston 46 rises, the volume of the chamber 51 increases. For this reason, fuel flows into the chamber 51 from the pressure control chamber 20 via the control chamber communication passage 48, and the fuel pressure in the pressure control chamber 20 is reduced.

  That is, according to the fuel injection valve 2 ′ of the present embodiment, when the needle needle bounces while the needles 12 and 13 are raised and the fuel pressure in the pressure control chamber 20 suddenly rises, the inner needle bounce is generated. The pressure difference between the fuel pressure in the delay pressure supply passage 49 substantially equal to the fuel pressure in the pressure control chamber 20 before the occurrence and the fuel pressure in the pressure control chamber 20 increased by the occurrence of the inner needle bounce is larger than the limit differential pressure. As a result, the piston 46 is raised and the fuel in the pressure control chamber 20 flows into the chamber 51. In other words, the differential pressure between the fuel pressure in the delay pressure supply passage 49 that is substantially equal to the fuel pressure in the pressure control chamber 20 before the occurrence of the inner needle bounce and the fuel pressure in the pressure control chamber 20 that has increased due to the occurrence of the inner needle bounce. The fuel pressure in the pressure control chamber 20 is controlled so that is less than the limit differential pressure.

  In other words, the pressure difference between the fuel pressure in the pressure control chamber 20 that has risen during a predetermined period after the occurrence of the inner needle bounce and the fuel pressure in the delay pressure supply passage 49 that has risen during the same period is a constant differential pressure. When the fuel pressure in the pressure control chamber 20 increases at such a speed, that is, when the increase speed of the fuel pressure in the pressure control chamber 20 becomes faster than the limit speed, the piston 46 is raised. In other words, according to the fuel injection valve 2 ′ of the present embodiment, the fuel pressure in the pressure control chamber 20 is controlled so that the rising speed of the fuel pressure in the pressure control chamber 20 is equal to or lower than the limit speed.

  As described above, according to the fuel injection valve 2 ′ of the present embodiment, even if the inner needle bounce occurs, the fuel pressure in the pressure control chamber 20 does not increase so much, and thus the inner needle 12 does not decrease so much. Therefore, the vibration of the fuel pressure in the pressure control chamber 20 and the vibration of the lift amount of the inner needle 12 that occur thereafter are also suppressed. As a result, the fuel injection amount from the fuel injection valve 2 ′ can be controlled relatively appropriately, and the engine output, fuel consumption, and exhaust emission can be prevented from decreasing.

  In the above embodiment, when the fuel pressure in the pressure control chamber 20 is increased by setting the three-way valve 23 to the fuel inflow position, the fuel pressure in the delay pressure supply passage 49 and the fuel in the pressure control chamber 20 are increased. The biasing force of the piston spring 47 is set so that the piston 46 does not rise even if there is a difference in pressure.

  However, the biasing force of the piston spring 47 may be set so that the piston 46 rises even when the fuel pressure in the pressure control chamber 20 rises by setting the three-way valve 23 to the fuel inflow position. In this case, when the increase in the fuel pressure in the pressure control chamber 20 due to the inner needle bounce is not so large, the piston 46 rises and the fuel in the pressure control chamber 20 flows out into the chamber 51. Therefore, the fuel outflow into the chamber 51 can be started from the time when the fuel pressure in the pressure control chamber 20 does not increase so much by the inner needle bounce. For this reason, the vibration of the fuel pressure in the pressure control chamber 20 and the vibration of the lift amount of the inner needle 12 can be more reliably suppressed. However, in this case, since the piston 46 slightly rises when the fuel pressure in the pressure control chamber 20 rises immediately after switching the three-way valve 23 to the fuel inflow position, the lowering of the needles 12 and 13 starts slightly. Be late.

  Next, a modified example of the fuel injection valve 2 'according to the second embodiment of the present invention will be described with reference to FIG. In the fuel injection valve 2 ′ shown in FIG. 5, the delay pressure supply path 49 and the orifice 50 are not provided as compared with the fuel injection valve 2 ′ of the second embodiment shown in FIG. 4. Therefore, only the downward force received from the piston spring 47 and the upward force received from the fuel in the pressure control chamber 20 are applied to the piston 46. Therefore, the piston 46 rises when the fuel pressure in the pressure control chamber 20 increases, and descends when the fuel pressure in the pressure control chamber 20 decreases.

  Therefore, in the fuel injection valve 2 ′ of this modification, the volume of the chamber 51 increases when the fuel pressure in the pressure control chamber 20 increases, and the volume decreases when the fuel pressure in the pressure control chamber 20 decreases. For this reason, the chamber 51 functions as a damper that attenuates fluctuations in the fuel pressure in the pressure control chamber 20. Therefore, when the fuel pressure in the pressure control chamber 20 suddenly rises due to the occurrence of the inner needle bounce, the volume of the chamber 51 increases and the pressure rise is suppressed, and conversely, the fuel pressure in the pressure control chamber 20 suddenly increases. In this case, the volume of the chamber is reduced and the pressure drop is suppressed.

  Thus, by the chamber 51 acting as a damper, the fuel pressure in the delay pressure supply passage 49 that is substantially equal to the fuel pressure in the pressure control chamber 20 before the inner needle bounce is generated, and the pressure control that is increased by the occurrence of the inner needle bounce. The pressure difference from the fuel pressure in the chamber 20 is maintained to be equal to or lower than the limit pressure difference. In other words, the fuel pressure in the pressure control chamber 20 is controlled so that the rising speed of the fuel pressure in the pressure control chamber 20 is less than the limit speed.

  According to the fuel injection valve 2 ′ of this modified example, it is possible to suppress the vibration of the fuel pressure in the pressure control chamber 20, and to suppress the vibration of the lift amount of the inner needle 12 accordingly. However, in this case, the piston 46 slightly lowers or rises when the fuel pressure in the pressure control chamber 20 decreases or increases immediately after switching the three-way valve 23 to the fuel outflow position or immediately after switching to the fuel inflow position. The start of raising or lowering of the needles 12 and 13 is slightly delayed.

It is a schematic sectional drawing which shows the fuel injection valve of 1st embodiment of this invention. It is a figure which shows transition of the lift amount of a needle and the fuel injection rate from the start to the end of fuel injection. It is a figure which shows transition of the fuel pressure in a pressure control chamber, and needle lift amount when an inner needle bounce arises. It is a schematic sectional drawing which shows the fuel injection valve of 2nd embodiment of this invention. It is a schematic sectional drawing which shows the example of a change of the fuel injection valve of 2nd embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Common rail 2 Fuel injection valve 3 Fuel tank 11 Nozzle body 12 Inner needle 13 Outer needle 14 Inner injection hole group 15 Outer injection hole group 16 Nozzle chamber 20 Pressure control chamber 23 Three-way valve 36 Cylinder 37 Open / close valve 38 Open / close valve spring 40 Orifice

Claims (8)

The first nozzle hole group and the second nozzle hole group, a control chamber, a first needle and a second needle are provided, the first needle opens and closes the nozzle holes of the first nozzle hole group, and the second needle In the fuel injection valve that opens and closes the nozzle holes of the two nozzle hole groups, and the lift of the first needle and the second needle is controlled by the pressure of the fuel in the control chamber,
Fuel injection further comprising pressure control means for controlling the pressure in the control chamber so that the differential pressure before and after the pressure rise when the pressure of the fuel in the control chamber rises while the needle is rising valve.   The fuel injection valve according to claim 1, wherein the pressure control means includes a variable volume chamber communicating with the control chamber, and the volume of the chamber is increased as the differential pressure before and after the pressure increase is increased.   The pressure control means includes a communication passage communicating with the control chamber and the fuel outflow passage, and an opening / closing valve for opening / closing the communication passage, and the opening / closing valve has a pressure difference before and after the pressure increase larger than a limit differential pressure. 2. The fuel injection valve according to claim 1, wherein the fuel injection valve is opened in the case. The first nozzle hole group and the second nozzle hole group, a control chamber, a first needle and a second needle are provided, the first needle opens and closes the nozzle holes of the first nozzle hole group, and the second needle In the fuel injection valve that opens and closes the nozzle holes of the two nozzle hole groups, and the lift of the first needle and the second needle is controlled by the pressure of the fuel in the control chamber,
A fuel injection valve provided with pressure control means for controlling the pressure in the control chamber so that, when the pressure of the fuel in the control chamber rises while the needle is rising, the pressure increase speed is less than the limit speed.   The fuel injection valve according to claim 4, wherein the pressure control means includes a variable volume chamber communicating with the control chamber, and the volume of the chamber is increased at a speed corresponding to the pressure increase speed.   The pressure control means includes a communication passage communicating with the control chamber and the fuel outflow passage, and an opening / closing valve for opening / closing the communication passage, and the opening / closing valve opens when the pressure increase rate is faster than a limit speed. The fuel injection valve according to claim 4.   One side of the on-off valve is provided with a direct communication path that directly communicates with the control chamber, and the other side is provided with an indirect communication path that communicates with the control chamber via an orifice. The fuel control valve according to claim 3 or 6, wherein the valve opens when a differential pressure between the pressure received from the fuel and the pressure received from the fuel in the indirect communication passage becomes greater than a certain differential pressure.   The fuel injection valve according to any one of claims 1 to 7, wherein either one of a fuel inflow passage and a fuel outflow passage is selectively communicated with the control chamber.

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