JP4412384B2 - Fuel injection device - Google Patents

Description

  The present invention relates to a fuel injection device.

A pressure control chamber formed on the inner end of the needle valve and an intermediate chamber of a pressure-increasing piston for increasing the injection pressure, and the high-pressure fuel in the common rail supplied into the pressure control chamber is fed into the fuel discharge passage. The needle valve is opened to discharge the fuel to inject fuel, and the high-pressure fuel in the common rail supplied into the intermediate chamber is discharged into the fuel discharge passage to operate the pressure-increasing piston to increase the fuel injection pressure. In the fuel injection apparatus, the pressure control chamber and the intermediate chamber are connected to the fuel discharge passage via a three-position switching type three-way valve, and the pressure control is performed when the injection pressure is increased during fuel injection by the switching action of the three-way valve. Both the chamber and the intermediate chamber are connected to the fuel discharge passage, and when the injection pressure is not increased during fuel injection, that is, when the operation of the boosting piston is stopped, only the pressure control chamber is discharged. The fuel injection system to be coupled to the road are known (e.g., see Patent Document 1).
JP 2003-106235 A

By the way, in the above-mentioned three-position switching type three-way valve, the valve element is one of one end position, intermediate position, and the other end position by changing the excitation current value supplied to the solenoid coil for driving the valve element. Moved to one position. In this case, it is theoretically possible to stop the valve body at an intermediate position with electromagnetic force, but in reality, the position of the valve body is extremely unstable, and is intended to be mounted on a particularly vibrated engine. In the present fuel injection apparatus, it is not desired to use a three-position switching type three-way valve in which the valve body is positioned at an intermediate position by electromagnetic force. Further, if the valve body is to be positioned at three positions, the lift amount of the valve body must be increased. In order to increase the lift amount of the valve body, the electromagnetic coil must be considerably enlarged. However, it is extremely difficult to increase the size of the electromagnetic coil in the fuel injection valve.
An object of the present invention is to provide a fuel injection device capable of controlling a pressure increasing action by a pressure increasing piston using a stable two-position switching type three-way valve.

That is, according to the present invention, the pressure control chamber formed on the inner end portion of the needle valve and the intermediate chamber of the pressure increasing piston for increasing the injection pressure are placed in the common rail through the two-position switching type three-way valve. By selectively connecting to the fuel discharge passage, the high pressure fuel in the common rail supplied into the pressure control chamber is discharged into the fuel discharge passage, the needle valve is opened to perform fuel injection, and the fuel is supplied into the intermediate chamber In a fuel injection device in which a high pressure fuel in a common rail is discharged into a fuel discharge passage to operate a pressure increasing piston to increase a fuel injection pressure , the fuel pressure in the common rail is preliminarily set in accordance with the operating state of the engine. contain altered between lower than a defined fuel pressure low-pressure fuel region with a predetermined fuel pressure is higher the high-pressure fuel region than in the fuel flow passage communicating between the three-way valve and the intermediate chamber Between room control valve disposed intermediate chamber control valve causes the intermediate chamber control valve to supply the high pressure fuel in the common rail to an intermediate chamber control valve for the intermediate chamber control valve actuated actuated by the high pressure fuel in the common rail of the engine The flow area of the fuel circulation passage is controlled according to the change in the fuel pressure in the common rail according to the operating state. When the fuel pressure in the common rail reaches the high pressure side fuel region, the flow in the fuel circulation passage by the intermediate chamber control valve is controlled. When the fuel pressure in the common rail becomes the low pressure side fuel region by the pressure increase piston by the road area control, the fuel pressure in the common rail is increased by the flow area control of the fuel flow passage by the intermediate chamber control valve. The pressure increasing action by the pressure-increasing piston is weakened or the operation of the pressure-increasing piston is stopped as compared with the case in the side fuel region.

  Stable fuel injection action and stable pressure increase control can be ensured.

  FIG. 1 schematically shows the entire fuel injection apparatus, and a portion 1 surrounded by a one-dot chain line in FIG. 1 indicates a fuel injection valve attached to the engine. As shown in FIG. 1, the fuel injection device includes a common rail 2 for storing high-pressure fuel, and fuel in the fuel tank 3 is supplied into the common rail 2 via a high-pressure fuel pump 4. The fuel pressure in the common rail 2 is maintained at the target fuel pressure corresponding to the engine operating state by controlling the discharge amount of the high pressure fuel pump 4, and the high pressure fuel in the common rail 2 maintained at the target fuel pressure is the high pressure fuel. It is supplied to the fuel injection valve 1 through the supply passage 5.

  As shown in FIG. 1, the fuel injection valve 1 includes a nozzle portion 6 for injecting fuel into the combustion chamber, a pressure intensifier 7 for increasing the injection pressure, and a three-way valve 8 for switching the fuel passage. It has. This three-way valve 8 is a two-position switching type three-way valve that is switched to one of two positions, one end position indicated by 8a in FIG. 1 and the other end position indicated by 8b in FIG. Consists of. The nozzle portion 6 includes a needle valve 9, and a nozzle hole 10 (not shown) that is controlled to open and close by the tip portion of the needle valve 9 is formed at the tip of the nozzle portion 6. A nozzle chamber 11 filled with high-pressure fuel to be injected is formed around the needle valve 9, and a pressure control chamber 12 filled with fuel is formed on the top surface of the needle valve 9. A compression spring 13 is inserted into the pressure control chamber 12 so that the needle valve 9 is directed downward, that is, in the valve closing direction. The pressure control chamber 12 is connected to the three-way valve 8 via the fuel flow passage 14. It is connected.

  On the other hand, the pressure booster 7 includes a pressure increasing piston 17 composed of a large-diameter piston 15 and a small-diameter piston 16 which are integrally formed. A high-pressure chamber 18 filled with high-pressure fuel is formed on the top surface of the large-diameter piston 15 opposite to the small-diameter piston 16, and the high-pressure chamber 18 is connected to a high-pressure fuel supply passage 19 via a high-pressure fuel supply passage 19. 5 is connected. Accordingly, the fuel pressure in the common rail 2 (hereinafter referred to as common rail pressure) is constantly acting in the high pressure chamber 18. On the other hand, an intermediate chamber 20 filled with fuel is formed on the end face of the large-diameter piston 15 around the small-diameter piston 16, and the large-diameter piston 15 faces the high-pressure chamber 18 in the intermediate chamber 20. An urging compression spring 21 is inserted. Further, a pressure increasing chamber 22 filled with fuel is formed on the end face of the small diameter piston 16 opposite to the large diameter piston 15, and the pressure increasing chamber 22 and the nozzle chamber 11 are provided with a high pressure fuel supply passage 23, a high pressure. A check valve 24 that can flow only from the fuel supply passage 19 toward the high-pressure fuel supply passage 23 is connected to the high-pressure fuel supply passage 5 via the high-pressure fuel supply passage 19.

  On the other hand, an intermediate chamber control valve 26 is disposed in a fuel flow passage 25 that communicates the three-way valve 8 and the intermediate chamber 20, and the flow passage area of the fuel flow passage 25 is controlled by the intermediate chamber control valve 26. In other words, the intermediate chamber control valve 26 is connected to the three-way valve 8 on the one hand via the fuel flow passage 25a and the fuel flow passage 14, and is connected to the intermediate chamber 20 on the other hand via the fuel flow passage 26b. Further, the high pressure fuel in the common rail 2 is supplied to the intermediate chamber control valve 26 through the high pressure fuel supply passages 5 and 19 and the high pressure fuel supply passage 27 for valve operation.

  On the other hand, in addition to the high-pressure fuel supply passage 5 and the fuel circulation passage 14, for example, a fuel discharge passage 28 connected to the inside of the fuel tank 3 is connected to the three-way valve 8. The three-way valve 8 is driven by an actuator 29 such as an electromagnetic solenoid or a piezoelectric element, and the fuel flow passage 14 is selectively connected to either the high-pressure fuel supply passage 5 or the fuel discharge passage 28 by the three-way valve 8. The

Next, the operation of the needle valve 9 and the pressure increasing piston 17 when the intermediate chamber control valve 26 fully opens the flow path of the fuel circulation passage 25 will be described with reference to FIG.
FIG. 1 shows a case where the fuel flow passage 14 is connected to the high-pressure fuel supply passage 5 by the fuel passage switching action by the three-way valve 8. In this case, both the inside of the pressure control chamber 12 and the inside of the intermediate chamber 20 are shown. Common rail pressure. On the other hand, at this time, the inside of the nozzle chamber 11, the high pressure chamber 18, and the pressure increasing chamber 22 are also at the common rail pressure. At this time, the force of lowering the needle valve 9 by the fuel pressure in the pressure control chamber 12 and the spring force of the compression spring 13 is stronger than the force of raising the needle valve 9 by the fuel pressure in the nozzle chamber 11. Therefore, the needle valve 9 is lowered, and as a result, the needle valve 9 is closed, so that fuel injection from the nozzle 10 is stopped. On the other hand, as for the pressure intensifier 7, the inside of the high pressure chamber 18, the intermediate chamber 20, and the pressure intensifying chamber 22 are all at the common rail pressure as described above. Therefore, at this time, as shown in FIG. Is held in a raised state by the spring force of the compression spring 21.

  On the other hand, when the fuel flow passage 14 is connected to the fuel discharge passage 28 by the passage switching action by the three-way valve 8, the fuel pressure in the pressure control chamber 12 of the nozzle portion 6 is lowered, so that the needle valve 9 rises. The needle valve 9 is opened and the fuel in the nozzle chamber 11 is injected from the nozzle 10. On the other hand, since the fuel pressure in the intermediate chamber 20 decreases at this time, a large downward force acts on the pressure increasing piston 17, and as a result, the fuel pressure in the pressure increasing chamber 22 becomes higher than the common rail pressure. Accordingly, at this time, the fuel pressure in the nozzle chamber 11 connected to the pressure increasing chamber 22 via the high-pressure fuel supply passage 23 is also higher than the common rail pressure, and this high fuel pressure is maintained during fuel injection. Maintained. Therefore, when the needle valve 9 is opened, fuel is injected from the nozzle 10 with an injection pressure higher than the common rail pressure.

  Next, when the fuel flow passage 14 is again connected to the high pressure fuel supply passage 5 as shown in FIG. 1 by the fuel passage switching action by the three-way valve 8, the pressure control chamber 12 of the nozzle portion 6 becomes the common rail pressure, and as a result, the fuel Is stopped. At this time, the pressure in the intermediate chamber 20 of the pressure booster 7 also becomes the common rail pressure, and as a result, the pressure boosting piston 17 is held in the raised state again as shown in FIG. 1 by the spring force of the compression spring 23.

  On the other hand, when the intermediate chamber control valve 26 blocks the fuel circulation passage 25, the fuel circulation passage 25a may be connected to the high pressure fuel supply passage 5 or to the fuel discharge passage 28 by the switching action of the three-way valve 8. The fuel pressure in the intermediate chamber 20 does not fluctuate, and therefore the booster piston 17 does not operate. Accordingly, at this time, the inside of the nozzle chamber 11 is always at the common rail pressure, and thus the injection pressure at the time of fuel injection is the common rail pressure. Thus, the intermediate chamber control valve 26 controls the pressure increasing action by the pressure increasing piston 17.

  Now, in a compression ignition type internal combustion engine, the machine noise is low at a light load, particularly at idling operation, and therefore, if a large combustion noise is generated at this time, the passenger is uncomfortable. By the way, if the injection pressure is increased and the injection rate is increased during light load operation or idling operation, the combustion pressure suddenly rises and combustion noise is generated. Therefore, at this time, in order to reduce the combustion noise, the injection pressure, that is, the common rail pressure is reduced. It needs to be lowered. On the other hand, since it is necessary to inject a large amount of fuel within a certain period during high load operation, the injection pressure is increased and the common rail pressure is increased. Thus, the common rail pressure is low when the engine load or the engine output torque is small, and is increased as the engine load or the engine output torque increases.

  On the other hand, in order to further increase the engine output during engine high load operation, it is necessary to inject more fuel within a certain period. Therefore, in the present invention, the injection pressure is increased by operating the pressure-increasing piston 17 in order to inject as much fuel as possible within a certain period during engine high load operation. Since the common rail pressure is increased as the engine output torque is increased, the injection pressure is increased by the pressure increasing piston 17 in the present invention when the common rail pressure is increased. That is, in the present invention, as shown in FIG. 2, when the fuel pressure in the common rail 2 is in the high-pressure side fuel region II higher than the predetermined fuel pressure, the pressure-increasing piston 17 is operated and the fuel pressure in the common rail 2 is Is in the low-pressure side fuel region I lower than the predetermined fuel pressure, or the pressure-increasing action by the pressure-increasing piston 17 is weakened or increased as compared with when the fuel pressure in the common rail 2 is in the high-pressure side fuel region II. The operation of the piston 17 is stopped. In FIG. 2, the vertical axis TQ indicates the output torque of the engine, and the horizontal axis NE indicates the engine speed. Further, in order to operate the pressure-increasing piston 17, high-pressure fuel in the intermediate chamber 20 must be discharged into the fuel discharge passage 28, and discharging such high-pressure fuel in this way results in energy loss. Therefore, it is preferable to reduce the discharge amount of the high-pressure fuel as much as possible. In this regard, in the present invention, the discharge amount of the high-pressure fuel is reduced by stopping the operation of the pressure-increasing piston 17 in the low-pressure side fuel region I in FIG.

  Next, referring to FIGS. 3A and 3B, when the fuel pressure in the common rail 2 is in the high-pressure side fuel region II shown in FIG. 2, the pressure-increasing piston 17 is operated, and the fuel pressure in the common rail 2 is changed. A first embodiment of the intermediate chamber control valve 26 in which the operation of the pressure-increasing piston 17 is stopped when in the low-pressure side fuel region I shown in FIG. 2 will be described.

  Referring to FIG. 3A, the intermediate chamber control valve 26 is formed on a cylindrical valve chamber 30, a valve body 31 reciprocating in the valve chamber 30, an end face in the axial direction of the valve body 31, and a high pressure. A high-pressure chamber 32 connected to the common rail 2 through a fuel supply passage 27 is provided. An annular concave groove 33 is formed on the outer peripheral surface of the central portion in the axial direction of the valve body 31, whereby the valve bodies 31 are spaced apart from each other in the axial direction and connected to each other and the inner periphery of the valve chamber 30. The first valve element 31a and the second valve element 31b slide on the surface. In this embodiment, the first valve body 31a and the second valve body 31b have the same outer diameter.

  As shown in FIG. 3A, the high-pressure chamber 32 is formed on the outer end surface of the first valve body 31a, and the end chamber 34 is formed on the outer end surface of the second valve body 31b. An inter-valve chamber 35 is formed in the recessed groove 33 between the first valve body 31a and the second valve body 31b. On the other hand, a spring member 36 that urges the first valve body 31 a and the second valve body 32 b toward the high pressure chamber 32 is inserted into the end chamber 34, and this end chamber 34 is connected to the fuel discharge passage 28. The The fuel flow passages 25a and 25b are aligned, and a three-way valve side fuel flow opening 37 and a fuel flow passage 25b connected to the three-way valve 8 through the fuel flow passage 25a are provided on the inner peripheral surface of the valve chamber 30. An intermediate chamber side fuel circulation opening 38 connected to the intermediate chamber 20 is formed.

  When the fuel pressure in the common rail 2 is in the low-pressure side fuel region I shown in FIG. 2, the valve element 31 is raised by the spring force of the spring member 36 as shown in FIG. The side fuel circulation opening 37 and the intermediate chamber side fuel circulation opening 38 are closed by the outer peripheral surface of the second valve body 31b. That is, the fuel flow passage 25 is blocked by the intermediate chamber control valve 26. Accordingly, at this time, the operation of the pressure increasing piston 17 is stopped, and the injection pressure becomes the common rail pressure.

  On the other hand, when the fuel pressure in the common rail 2 is in the high-pressure side fuel region II shown in FIG. 2, the valve body 31 is moved by the common rail pressure in the high-pressure chamber 32 as shown in FIG. The three-way valve side fuel circulation opening 37 and the intermediate chamber side fuel circulation opening 38 are both opened into the valve chamber 35 by being pushed down against the spring force. That is, the intermediate chamber control valve 26 fully opens the flow path of the fuel circulation passage 25. Therefore, at this time, when the fuel flow passage 14 is connected to the high pressure fuel supply passage 5 by the flow path switching action by the three-way valve 8, the high pressure fuel in the common rail 2 is sent into the intermediate chamber 20, and the fuel flow passage 14 becomes the fuel discharge passage. When connected to 28, the high pressure fuel in the intermediate chamber 20 is discharged, so that the pressure increasing piston 17 increases the pressure.

  In the first embodiment shown in FIG. 3, the high pressure fuel in the common rail 2 is supplied into the fuel flow passage 25a regardless of whether the valve element 31 is in the state shown in FIG. 3A or in the state shown in FIG. Then, the high-pressure fuel leaks into the end chamber 34 through the outer periphery of the second valve body 31b and the inner wall surface of the valve chamber 30, and the fuel leaked into the end chamber 34 is discharged to the fuel discharge passage 28. . However, such a structure in which high-pressure fuel leaks is not preferable because the driving energy of the high-pressure fuel pump 4 increases. The embodiment described below shows a structure in which high-pressure fuel does not leak. In the embodiments described below, the same reference numerals are used for the same structures as those shown in FIG.

  4A and 4B show a second embodiment. The second embodiment is different from the first embodiment in that the end chamber 34 has a fuel passage 40 having a smaller channel cross section than the fuel circulation passages 25a and 25b in order not to cause leakage of high-pressure fuel in the intermediate chamber control valve 26. It is connected to the fuel flow passage 25a via Also in the second embodiment, when the fuel pressure in the common rail 2 is in the high pressure side fuel region II shown in FIG. 2, the pressure increasing piston 17 is operated, and the fuel pressure in the common rail 2 is low pressure side fuel shown in FIG. While the operation of the pressure-increasing piston 17 is stopped when in the region I, the movement of the valve body 31 when performing the pressure-increasing action by providing the fuel passage 40 is slightly different from that in the first embodiment.

  That is, when the fuel pressure in the common rail 2 is in the low-pressure side fuel region I shown in FIG. 2, the valve body 31 rises as shown in FIG. 4 (A). At this time, the second valve body 31b The fuel circulation passages 25a and 25b are blocked. When the fuel pressure in the fuel flow passage 25a varies due to the flow path switching action by the three-way valve 8, the fuel pressure in the end chamber 34 also varies, but the fuel pressure in the high pressure chamber 32 is not so high, so the valve element 31 As shown in FIG. 4 (A), the raised position is maintained.

  On the other hand, when the fuel pressure in the common rail 2 is in the high-pressure side fuel region II shown in FIG. 2, the fuel pressure in the high-pressure chamber 32 becomes high. At this time, when the fuel flow passage 25a is connected to the high-pressure fuel flow passage 5 by the flow path switching action by the three-way valve 8, the fuel pressure in the end chamber 34 becomes higher, so that the valve body is shown in FIG. 31 rises. However, actually, even if the flow passage area of the fuel passage 40 is small or the fuel circulation passage 25a is connected to the high-pressure fuel circulation passage 5 due to the inertia of the valve body 31, the valve body 31 does not rise immediately, and FIG. ), The intermediate chamber control valve 26 is maintained in a state in which the flow path of the fuel circulation passage 25 is fully opened. Accordingly, high pressure fuel is supplied into the intermediate chamber 20 during this period.

  Next, when the fuel flow passage 25a is connected to the fuel discharge passage 28 by the flow path switching action by the three-way valve 8, the fuel pressure in the end chamber 34 decreases, so that the valve body 31 is moved as shown in FIG. The intermediate chamber control valve 26 fully opens the flow path of the fuel circulation passage 25. As a result, the fuel pressure in the intermediate chamber 20 decreases, and the pressure increasing action by the pressure increasing piston 17 is performed.

  5A and 5B show a third embodiment. In the first embodiment and the second embodiment, an upward force is applied to the valve body 31 by the spring force of the spring member 36, so that a large and strong spring member is required as the spring member 36. In the third embodiment, the outer diameter of the second valve body 31b is made smaller than the outer diameter of the first valve body 31a, and the end chamber 34 is connected to the common rail 2 via the high-pressure fuel supply passage 41 to thereby connect the end chamber. The fuel pressure in 34 is a common rail pressure, and a small and weak spring member 36 is used as the spring member 36 by applying downward fuel pressure to the valve body 31 by the difference in cross-sectional area between the first valve body 31a and the second valve body 31b. Can be used. In the third embodiment, the inter-valve chamber 35 is always connected to the fuel circulation passage 25a via the fuel passage 42 having a smaller passage area than the fuel circulation passage 25a.

  Also in the third embodiment, when the fuel pressure in the common rail 2 is in the low pressure side fuel region I shown in FIG. 2, the valve element 31 is raised as shown in FIG. The fuel flow passages 25a and 25b are blocked by the second valve body 31b. If the fuel pressure in the fuel flow passage 25a varies due to the flow path switching action by the three-way valve 8, the fuel pressure in the inter-valve chamber 35 also varies, but the fuel pressure in the high-pressure chamber 32 is not so high, so the valve element 31 Is held in the raised position as shown in FIG.

  On the other hand, when the fuel pressure in the common rail 2 is in the high-pressure side fuel region II shown in FIG. 2, the fuel pressure in the high-pressure chamber 32 and the end chamber 34 is high. At this time, when the fuel flow passage 25a is connected to the high-pressure fuel flow passage 5 by the flow path switching action by the three-way valve 8, the fuel pressure in the inter-valve chamber 35 becomes the common rail pressure, as shown in FIG. Further, the valve body 31 is raised by the spring force of the spring member 36. However, in actuality, even if the fuel flow passage 25a is connected to the high-pressure fuel flow passage 5 due to the inertia of the valve body 31, the valve body 31 does not rise immediately, and the intermediate chamber control valve 26 is not shown in FIG. The flow path of the fuel circulation passage 25 is maintained in a fully opened state. Accordingly, high pressure fuel is supplied into the intermediate chamber 20 during this period.

  Next, when the fuel flow passage 25a is connected to the fuel discharge passage 28 by the flow path switching action by the three-way valve 8, the fuel pressure in the inter-valve chamber 35 decreases, so that the valve body 31 is shown in FIG. Is lowered, and the intermediate chamber control valve 26 fully opens the flow path of the fuel circulation passage 25. As a result, the fuel pressure in the intermediate chamber 20 decreases, and the pressure increasing action by the pressure increasing piston 17 is performed.

  FIG. 6 shows a fourth embodiment. In the fourth embodiment, a fuel passage 43 is formed on the central axis of the valve body 31, and the high-pressure fuel in the high-pressure chamber 32 is sent into the end chamber 34 through the fuel passage 43. In the fourth embodiment, there is an advantage that it is not necessary to form the high pressure fuel supply passage 41 as shown in FIGS. 5A and 5B in the fuel injection valve 1 in order to send the high pressure fuel into the end chamber 34. is there. Further, since the difference in the passage length between the high pressure chamber 32 and the common rail 2 and the passage length between the end chamber 34 and the common rail 2 can be reduced, the pressure pulsation generated in the common rail 2 is caused in the high pressure chamber 32 and the end chamber 34. Therefore, no phase difference occurs in the pressure pulsation in the high pressure chamber 32 and the end chamber 34, and thus the valve body 31 can be prevented from vibrating.

  FIG. 7 shows a fifth embodiment. Also in the fifth embodiment, a fuel passage 44 that connects the high-pressure chamber 32 and the end chamber 34 is formed in the valve body 31, and a throttle 45 is formed in the fuel passage 44. The moving speed of the valve body 31 is determined by the moving speed of the fuel from the high pressure chamber 32 to the end chamber 34 or the moving speed of the fuel from the end chamber 34 to the high pressure chamber 32, and the valve body 31 between the fuel injection valves 1 of each cylinder. In order to eliminate variations in the moving speed, it is necessary to match the moving speed of the fuel from the high pressure chamber 32 to the end chamber 34 and from the end chamber 34 to the high pressure chamber 32. In the fifth embodiment, the movement speeds of the valve bodies 31 can be matched by forming the throttle 45 with high accuracy.

  Further, in order to eliminate the variation in the moving speed of the valve element 31 between the fuel injection valves 1, the embodiment shown in FIGS. 5A and 5B is connected to the high pressure chamber 32 and the end chamber 34 as shown in FIG. In addition, throttles 46 and 47 can be provided in the high-pressure fuel supply passages 27 and 41, respectively.

  On the other hand, in the embodiment shown in FIGS. 5A and 5B, the pressure-increasing action by the pressure-intensifying piston 17 can be increased as the common rail pressure increases depending on how the spring force of the spring member 36 is set. The operation of the intermediate chamber control valve 26 in this case is shown in FIGS. 9 (A) and 9 (B) and FIGS. 10 (A) and 10 (B). That is, in this case, when the fuel pressure in the common rail 2 is in the high-pressure side fuel region III shown in FIG. 9A, the pressure-increasing piston 17 is operated strongly, and the fuel pressure in the common rail 2 is changed to FIG. ), The pressure-increasing action by the pressure-increasing piston 17 is reduced. When the fuel pressure in the common rail 2 is in the low-pressure side fuel region I shown in FIG. The operation of 17 is stopped. In FIG. 9A, TQ indicates the engine output torque, and NE indicates the engine speed.

  That is, when the fuel pressure in the common rail 2 is in the low pressure side fuel region I shown in FIG. 9A, the fuel pressure in the common rail 2 in the embodiment shown in FIGS. 5A and 5B is shown in FIG. As in the low pressure side fuel region I, the valve body 31 is always raised as shown in FIG. 9B, and the operation of the pressure increasing piston 17 is stopped.

  On the other hand, when the fuel pressure in the common rail 2 is in the high-pressure side fuel region III shown in FIG. 9A, the fuel pressure in the common rail 2 in the embodiment shown in FIGS. 5A and 5B is shown in FIG. When the fuel flow passage 25a is connected to the fuel discharge passage 28 as in the high pressure side fuel region II, the valve body 31 is lowered to the lowest position as shown in FIG. As a result, the flow paths of the fuel circulation passages 25a and 25b are fully opened, and a strong pressure increasing action by the pressure increasing piston 17 is performed.

  On the other hand, when the fuel pressure in the common rail 2 is in the intermediate pressure side fuel region II shown in FIG. 9A, the valve element 31 is shown in FIG. 10A when the fuel circulation passage 25a is connected to the fuel discharge passage 28. As shown, the second valve element 31b partially opens the three-way valve side fuel circulation opening 37 and the intermediate chamber side fuel circulation opening 38. That is, as the fuel pressure in the common rail 2 increases, the opening areas of the fuel flow openings 37 and 38 that open into the inter-valve chamber 35 gradually increase. When the opening area of each of the fuel flow openings 37 and 38 opened in the inter-valve chamber 35 is increased, the pressure increasing action by the pressure increasing piston 17 is strengthened, and therefore FIGS. 9 (A), 9 (B) and 10 (A), In the embodiment shown in (B), the pressure increasing action by the pressure increasing piston 17 is strengthened as the fuel pressure in the common rail 2 increases.

  In the embodiment shown in FIGS. 5A and 5B to FIGS. 10A and 10B, when the fuel circulation passage 25a is connected to the high-pressure fuel supply 5, the high-pressure fuel is sufficiently in the intermediate chamber 20. There is a risk that the intermediate chamber control valve 26 shuts off the fuel flow passage 25 before being supplied, and as a result, a good pressure increasing action cannot be performed. Further, when the common rail pressure gradually decreases, the intermediate chamber control valve 26 shuts off the fuel flow passage 25 in a state where the high-pressure fuel in the intermediate chamber 20 is released, and as a result, the common rail pressure that requires pressure increase is obtained. When this happens, there is a risk that the pressure increasing action will not be performed until the intermediate chamber 20 is filled with high-pressure fuel.

  When there is such a risk, as shown in FIG. 11, the intermediate chamber 20 is connected to the common rail 2 via a check valve 48 and a throttle 49 that can flow only from the common rail 2 toward the intermediate chamber 20. do it. In this way, even if the intermediate chamber control valve 26 shuts off the fuel flow passage 25, the intermediate chamber 20 is filled with the high-pressure fuel, so that the pressure increasing action can be reliably performed when the common rail pressure to be increased is reached. .

  In this way, when the intermediate chamber 20 is connected to the common rail 2 via the check valve 48, the intermediate chamber control valve 26 may be allowed to perform an operation only for discharging the high-pressure fuel in the intermediate chamber 20.

  Further, in order to fill the intermediate chamber 20 with the high-pressure fuel, as shown in FIG. 12, the end portion 34 and the fuel circulation passage 25b or the intermediate chamber 20 have a fuel passage 50 having a smaller flow area than the fuel circulation passage 25b. You may make it connect via. In this way, since the fuel pressure in the end chamber 34 rises after the intermediate chamber 20 is filled with the high pressure fuel, the intermediate chamber control valve 26 shuts off the fuel flow passages 25a and 25b until the intermediate chamber 20 is filled with the high pressure fuel. Thus, the intermediate chamber 20 is surely filled with high-pressure fuel.

  Next, referring to FIGS. 13A and 13B, when the fuel pressure in the common rail 2 is in the high pressure side fuel region II shown in FIG. 2, the pressure increasing piston 17 is operated, and the fuel pressure in the common rail 2 is changed. 2 shows an embodiment in which the pressure increasing action by the pressure increasing piston 17 is weakened when the fuel pressure in the common rail 2 is in the high pressure side fuel region II when in the low pressure side fuel region I shown in FIG. .

  In this embodiment, the fuel flow passage 25 b connected to the intermediate chamber 20 is always in communication with the valve chamber 35, and the fuel flow passage 25 a connected to the three-way valve 8 is connected via the throttle 51 and the bypass passage 52. The valve chamber 35 is always communicated with the valve chamber 35. That is, in this embodiment, when the fuel pressure in the common rail 2 is in the low pressure side fuel region I shown in FIG. 2, the valve body 31 is raised as shown in FIG. The fuel flow opening 37 is closed by the second valve body 31b. Accordingly, at this time, the intermediate chamber 20 is always communicated with the fuel circulation passage 25a via the bypass passage 52 and the throttle 51, and as a result, a weak pressure increasing action is performed by the pressure increasing piston 17.

  On the other hand, when the fuel pressure in the common rail 2 is in the high-pressure side fuel region II shown in FIG. 2, when the fuel circulation passage 25a is connected to the fuel discharge passage 28, as shown in FIG. The fuel flow opening 37 completely opens into the inter-valve chamber 35. Therefore, at this time, a strong pressure increasing action is performed.

  14 (A) and 14 (B) show a modification of the embodiment shown in FIGS. 13 (A) and 13 (B). In this modified example, the outer diameter of the second valve body 31b is formed larger than the outer diameter of the first valve body 31a, and the end passage 34 has a flow passage area comparable to the fuel circulation passage 25a. 53 is connected to the fuel flow passage 25a. Also in this embodiment, when the fuel pressure in the common rail 2 is in the low pressure side fuel region I shown in FIG. 2, the valve element 31 is raised as shown in FIG. Is done.

  On the other hand, when the fuel pressure in the common rail 2 is in the high-pressure side fuel region II shown in FIG. 2, the fuel pressure in the high-pressure chamber 32 becomes high. At this time, when the fuel flow passage 25a is connected to the high-pressure fuel flow passage 5 by the flow path switching action of the three-way valve 8, the fuel pressure in the end chamber 34 immediately increases, so that the valve as shown in FIG. The body 31 rises. At this time, the high-pressure fuel is supplied into the intermediate chamber 20 through the throttle 51 and the bypass passage 52. Next, when the fuel flow passage 25a is connected to the fuel discharge passage 28 by the flow path switching action by the three-way valve 8, the fuel pressure in the end chamber 34 immediately decreases, so that the valve body 31 as shown in FIG. Descends. As a result, the three-way valve side fuel flow opening 37 is completely opened in the inter-valve chamber 35, and thus a strong pressure increasing action is performed.

1 is an overall view of a fuel injection device. It is a figure which shows the low pressure side fuel area | region I and the high pressure side fuel area | region II of a common rail pressure. It is a figure which shows 1st Example of an intermediate chamber control valve. It is a figure which shows 2nd Example of an intermediate chamber control valve. It is a figure which shows 3rd Example of an intermediate chamber control valve. It is a figure which shows 4th Example of an intermediate chamber control valve. It is a figure which shows 5th Example of an intermediate chamber control valve. It is a figure which shows the modification of 3rd Example of an intermediate chamber control valve. It is a figure which shows an intermediate chamber control valve. It is a figure which shows an intermediate chamber control valve. 1 is an overall view of a fuel injection device. It is a figure which shows another Example of an intermediate chamber control valve. It is a figure which shows another Example of an intermediate chamber control valve. It is a figure which shows the modification of the Example shown in FIG. 13 of an intermediate chamber control valve.

Explanation of symbols

2 Common rail 5, 19, 23, 27, 41 High-pressure fuel supply passage 6 Nozzle part 7 Booster 8 Three-way valve 9 Needle valve 12 Pressure control chamber 14, 25, 25a, 25b Fuel flow passage 17 Pressure-increasing piston 20 Intermediate chamber 22 Increase Pressure chambers 24 and 48 Check valve 26 Intermediate chamber control valve 28 Fuel discharge passage 30 Valve chamber 31 Valve body 31a First valve body 31b Second valve body 32 High pressure chamber 34 End chamber 35 Intervalve chamber 36 Spring member 37 Three-way Valve side fuel flow opening 38 Intermediate chamber side fuel flow opening 40, 42, 43, 44, 50, 53 Fuel passage

Claims (2)

The pressure control chamber formed on the inner end of the needle valve and the intermediate chamber of the booster piston for increasing the injection pressure are selectively connected to the common rail or the fuel discharge passage via a two-position switching type three-way valve. The high pressure fuel in the common rail supplied into the pressure control chamber is discharged into the fuel discharge passage to open the needle valve to perform fuel injection, and the high pressure fuel in the common rail supplied into the intermediate chamber is discharged. In a fuel injection device that operates a pressure-increasing piston to increase the fuel injection pressure by discharging the fuel into the fuel discharge passage, the fuel pressure in the common rail is higher than the fuel pressure determined in advance according to the operating state of the engine. also contain altered between the low low-pressure fuel region with a predetermined fuel pressure is higher the high-pressure fuel region than the intermediate chamber controlled fuel flow passage communicating between the three-way valve and the intermediate chamber It was placed, operated intermediate chamber control valve of the engine actuates a high-pressure fuel in the common rail the intermediate chamber control valve to supply the high pressure fuel in the common rail to the intermediate chamber control valve as an intermediate chamber control valve actuation The flow area of the fuel circulation passage is controlled according to the change in the fuel pressure in the common rail according to the state, and the fuel circulation by the intermediate chamber control valve when the fuel pressure in the common rail reaches the high pressure side fuel region. When the pressure in the common rail is increased by the passage area control of the passage and the fuel pressure in the common rail reaches the low pressure side fuel region, the common rail is controlled by the passage area control of the fuel circulation passage by the intermediate chamber control valve. A fuel injection device in which the pressure-increasing action by the pressure-increasing piston is weakened or the operation of the pressure-increasing piston is stopped compared to when the internal fuel pressure is in the high-pressure side fuel region.   When the fuel pressure in the common rail is in the high pressure side fuel region, the intermediate chamber control valve opens the flow path of the fuel circulation passage when the fuel circulation passage is connected to the fuel discharge passage by the switching action of the three-way valve, When the fuel pressure in the common rail is in the low-pressure side fuel region, when the fuel flow passage is connected to the fuel discharge passage by the switching action of the three-way valve, the flow passage of the fuel flow passage is smaller than the flow passage area when fully opened. The fuel injection device according to claim 1, wherein the fuel injection device is configured to be able to flow or to block the fuel flow passage.

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