JP4345696B2 - Common rail injector - Google Patents

Description

  The present invention relates to an injector used in a common rail fuel injection device for a diesel engine.

  In a common rail fuel injection device for a diesel engine, a common rail is provided for each cylinder to accumulate high-pressure fuel, and an injector is driven at a predetermined timing to inject a predetermined amount of fuel into each cylinder. As a common rail injector, there is a piezo injector using a piezo actuator as a drive unit, and high fuel injection control is expected because of its high responsiveness. Here, the drive unit of the piezo injector is usually provided with a hydraulic transmission device that transmits the displacement of the piezo actuator via hydraulic pressure.

For example, Patent Documents 1 to 3 are known as conventional techniques of an injector including a hydraulic transmission device.
JP 2002-115617 A US Patent Application Publication No. 2002-0104976 US Patent Application Publication No. 2003-0155540

  The piezo injector is generally configured to control the back pressure of the nozzle needle with a control valve. However, the piezoelectric actuator cannot be directly coupled to the control valve because of a large difference in coefficient of thermal expansion from the housing member. Therefore, an oil-tight transmission device is used when power is transmitted from the piezoelectric actuator side member to the control valve side member. The hydraulic transmission device has a first piston on the piezo side that is displaced integrally with the piezo actuator, and a second piston on the valve side that drives the valve body of the control valve, and is arranged in series in the cylinder. An oil-tight chamber is provided between the pistons. The control valve opens and closes between the control chamber that applies back pressure to the nozzle needle and the low-pressure passage, and closes the low-pressure passage when the piezo actuator is not energized. At this time, the control chamber is in high pressure in communication with the high pressure passage, and the nozzle needle closes the nozzle hole.

  When the piezo actuator is energized, the first piston is displaced together with the piezo actuator to increase the pressure in the oil tight chamber. Along with this, when the second piston pushes down the valve body of the control valve and opens the low pressure passage, the pressure in the control chamber drops, the nozzle needle is lifted, and fuel is injected. In this way, by interposing the hydraulic pressure, there is an advantage that a good heat transfer performance can be maintained by absorbing the amount of thermal deformation different among the constituent members by the fuel inflow / fuel leak into the oil tight chamber. Further, as in Patent Documents 1 to 3, if the first piston has a large diameter and the second piston has a small diameter, the displacement can be enlarged and transmitted according to the pressure receiving area ratio of both pistons.

  However, the conventional configuration requires a certain sliding length for both the first piston and the second piston, so that the axial length of the hydraulic transmission device becomes long. As a result, there is a problem that the total length of the injector using the piezo actuator becomes long.

  Accordingly, an object of the present invention is to ensure the sliding length when transmitting the displacement of a piezoelectric actuator or the like in an injector used in a common rail fuel injection device of a diesel engine, and the entire length of the displacement transmission device, and thus the total length of the injector. Is to make the whole compact.

The common rail injector according to the present invention increases or decreases the pressure in the control chamber by opening and closing the control chamber between the control chamber that applies the pressure in the valve closing direction to the nozzle needle and the low-pressure passage. The drive unit that drives the valve body of the control valve includes an actuator that generates displacement by energization, a first piston that slides in the cylinder integrally with the actuator, a second piston that drives the valve body, and between the pistons. An oil-tight chamber formed in The first piston is formed in a cylindrical shape with a closed upper end, and a second piston is slidably inserted in the cylindrical portion in the vertical direction to form a space surrounded by the inner peripheral surface of the cylindrical portion and the second piston end surface. Filled with hydraulic oil to form an oil tight chamber.
The common rail injector according to claim 1 is configured such that a ring-shaped spring is disposed on the lower end side of the first piston to apply an upward load and to apply a preset force to the piezoelectric actuator or the like. In addition, a ring member smaller than the sliding diameter of the second piston is provided on the lower end side of the first piston, and a plurality of disc springs by a single ring-shaped spring or a combination of series or parallel or both are used. The inner diameter side end edge portion is arranged so as to contact the lower end surface of the ring member.
The common rail injector according to claim 2 is provided with a slit spring for applying an upward load as a preset force of the actuator, instead of the ring-shaped spring. A seat surface that supports the upper end side of the slit spring is formed on the outer periphery of the upper end of the first piston, and a seat surface that supports the lower end side of the slit spring is formed on the outer periphery of the lower end of the second piston. A ring-shaped member is disposed, and the ring-shaped member is disposed so as to block the space between the cylinder and the low-pressure passage.
According to a third aspect of the present invention, the common rail injector includes a spring member disposed on the upper end side or the outer periphery of the second piston, for example, in an oil-tight chamber. And a recessed part is provided in the upper end part of a 2nd piston, a volume reduction member is accommodated in the inside, and a spring member is arrange | positioned around a volume reduction member as a coil spring.

According to the above configuration, the second piston is accommodated in the cylindrical portion of the first piston and the sliding range is configured to overlap, so that when the piezo actuator or the like is displaced, the sliding length of each piston is secured, The axial length of the device can be shortened. Therefore, since the length of the hydraulic transmission device is shorter than the conventional structure in which the first and second pistons are arranged in a straight line, the overall length of the injector can be shortened and a compact structure can be achieved.
Furthermore, the common rail injector according to the first aspect makes it easy to set the set length by disposing the ring-shaped spring at the above position. Furthermore, when a ring member smaller than the sliding diameter of the second piston is provided on the lower end side of the first piston and the ring-shaped spring is arranged as described above, the outer diameter of the ring-shaped spring can be increased, and the spring constant Can be reduced. Moreover, the assembly is easy and the load fluctuation at the time of displacement can be suppressed.
The common rail injector according to claim 2 can be easily installed by utilizing the space on the outer peripheral side of the first piston by the slit spring. At this time, a preset force can be applied to the actuator via a seating surface formed on the outer periphery of the upper end of the first piston, and if a ring-shaped member forming the seating surface is provided on the outer periphery of the lower end of the second piston, The spring height can be easily adjusted. Further, when the ring-shaped member is arranged as described above, leakage from the control valve can be prevented from flowing into the drive unit, and mixing of air into the oil-tight chamber and occurrence of cavitation erosion can be prevented.
The common rail injector according to claim 3 can bias the second piston toward the valve body of the control valve with a simple structure. If the spring member is arranged around the volume reducing member as a coil spring, the structure is simple, the volume of the oil tight chamber can be reduced, and the driving force transmission efficiency can be improved.

If the cylinder is formed by the vertical hole formed in the injector body as in the invention of claim 4 , the first piston can be stably displaced in the vertical direction by being guided by the inner peripheral surface thereof.

As in the fifth aspect of the invention, if the first piston is provided with a large diameter portion serving as a guide portion at the upper end portion and the lower end portion thereof and the guide portion is guided to the inner peripheral surface of the cylinder, the injector body is Even when it bends, slidability can be secured.

As in the sixth aspect of the present invention, a ring-shaped spring can be arranged on the lower end side of the first piston so as to apply an upward load and apply a preset force to the piezo actuator or the like. By setting a spring at this position, setting of the set length is facilitated.

As in the invention of claim 7 , the ring-shaped spring is a single series single spring, or a plurality of disc springs of various combinations using series or parallel or both, and the outer diameter side edge of the first piston is If it arrange | positions so that it may contact | abut to a lower end surface, the friction of the inner and outer periphery by a displacement can be eliminated.

As in the invention of claim 8, a ring member smaller than the sliding diameter of the second piston is provided on the lower end side of the first piston, and various ring-shaped springs are used in a single series, in series or in parallel, or both. You may arrange | position so that the internal-diameter side edge part may contact | abut the lower end surface of a ring member as several disc springs by a combination. At this time, the outer diameter of the ring-shaped spring can be increased, and the spring constant can be decreased. Moreover, the assembly is easy and the load fluctuation at the time of displacement can be suppressed.

As in the ninth aspect of the invention, instead of the ring-shaped spring, a slit spring for applying an upward load as a preset force of the actuator can be arranged, and the space on the outer peripheral side of the first piston is utilized. Easy to install.

If the seat surface which supports the upper end side of the said slit spring is formed in the upper-end outer peripheral part of the said 1st piston like invention of Claim 10 , installation of a slit spring will be easy, via this seat surface A preset force can be applied to the actuator.

If the ring-shaped member which makes the seat surface which supports the lower end side of the said slit spring is arrange | positioned on the outer periphery of the lower end part of the said 2nd piston like invention of Claim 11 , the height adjustment of a slit spring can be performed easily. .

When the ring-shaped member is disposed so as to block the space between the cylinder interior and the low-pressure passage as in the invention of claim 12 , the leakage from the control valve is suppressed from flowing into the drive unit, Prevents air from entering the oil-tight chamber and cavitation and erosion.

  If a check valve is provided between the oil-tight chamber and the low-pressure passage as in the invention of claim 13 to permit the inflow of hydraulic oil only to the oil-tight chamber, leakage from the sliding portion during operation is facilitated. Can be replenished.

  When the check valve has no spring member as in the invention of the fourteenth aspect, the volume of the oil tight chamber can be reduced and the driving force transmission efficiency can be increased.

  According to a fifteenth aspect of the present invention, a chamber for accommodating a valve body is formed at an abutting portion between a plate-like check valve member closely arranged on the upper end side of the first piston and the first piston, and a low pressure passage In addition, the check valve can be configured by communicating the oil tight chamber and the structure can be simplified.

  When the lower end surface of the check valve member and the upper end surface of the first piston are pressed against each other and contact with each other in a plane as in the invention of claim 16, steps such as press-fitting and joining are unnecessary.

  If the pressing force of the lower end surface of the check valve member and the upper end surface of the first piston is applied by a spring member that applies a preset force to the actuator, as in the invention of claim 17, the pressing member is specially provided. There is no need to place them.

  When the contact end surface of the check valve member and the actuator is configured by combining a convex spherical surface and a concave conical surface or a flat surface as in the invention of the eighteenth aspect, the number of parts can be reduced by also serving as a misalignment absorbing member.

  According to a nineteenth aspect of the present invention, a chamber in which a valve body is accommodated is formed by a recess provided on the lower end surface of the check valve member and an upper end surface of the first piston, and the check valve lift amount is formed by the recess and the valve body. Is determined, the check valve structure becomes simple and the lift amount can be easily adjusted.

  As in the twentieth aspect of the invention, the check valve includes a chamber that is closed when the valve body moves to the upper end position due to an increase in pressure in the oil-tight chamber. If the passage that connects the chamber and the oil-tight chamber is opened on the bottom surface of the chamber that is not closed when the valve element moves to the lower end position due to the pressure drop in the oil-tight chamber, the check valve structure is simplified. The spring member is unnecessary.

  If the closed end portion and the cylindrical portion of the first piston are configured as separate members as in the invention of claim 21, processing in the cylindrical portion on the closed end side becomes easy and can be manufactured at low cost.

  When a piezoelectric actuator having high response is used as the actuator as in the invention of claim 22, a compact and high-performance common rail injector can be realized.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of an injector 1 according to the first embodiment, which will be described as an application example of a diesel engine to a common rail fuel injection device. An injector 1 provided for each cylinder of the engine (only one of them is shown here) is supplied with fuel (light oil here) from a common rail. In the common rail, fuel pumped by a high-pressure supply pump is stored at a predetermined high pressure corresponding to the injection pressure.

  In the figure, an injector 1 uses a drive unit 101 having a piezo actuator 6 as an upper half, and uses a control valve unit 102 as a control valve to drive a nozzle unit 103 having a nozzle needle 5 to perform fuel injection. The injector 1 is attached to a combustion chamber wall (not shown), and in the body members B1 to B4 constituting the injector body in which the components of the respective parts 101 to 103 are accommodated, a fuel rail 11 is connected to a common rail (not shown). A passage such as a high pressure passage 12 that communicates with the fuel tank and a low pressure passage 13 that communicates with a fuel tank (not shown) at the fuel outlet 14 are formed. The body members B1 to B4 are oil-tightly fastened and fixed by the retainer B5.

  The nozzle portion 103 slidably holds a nozzle needle 5 having a large-diameter portion 51 serving as a seat for the spring 56 in a cylindrical portion 42 provided at the upper end portion of the body member B1. The space in the body member B4 constitutes an oil reservoir chamber 52, and high-pressure fuel is supplied from the common rail through the high-pressure passage 12 opened in the upper wall thereof. A sac portion 53 is formed at the lower end of the body member B4, and an injection hole 54 for injecting fuel through the sack portion 53 forming wall is formed.

  When the nozzle needle 5 is in the lower end position, a conical tip is seated on a nozzle sheet 55 provided at the boundary between the oil reservoir chamber 52 and the sac portion 53, the sac portion 53 is closed, and the nozzle hole is ejected from the oil reservoir chamber 52. The fuel supply to 54 is cut off. When the nozzle needle 5 is lifted and separated from the nozzle seat 55 and the sack portion 53 is opened, fuel is injected.

  A space defined by the upper end surface of the nozzle needle 5, the inner wall surface of the cylindrical portion 42, and the lower end surface of the body member B3 serves as a control chamber 4 for controlling the nozzle back pressure. Fuel as control oil is introduced into the control chamber 4 from the high-pressure passage 12 through the valve chamber 21 and the passage 25 of the control valve section 102, and the back pressure of the nozzle needle 5 is generated. This back pressure acts downward on the nozzle needle 5 and urges the nozzle needle 5 in the valve closing direction together with the spring 56 held between the large diameter portion 51 and the lower end surface of the cylindrical portion 42. On the other hand, the high-pressure fuel in the oil reservoir chamber 52 acts upward on the conical surface of the tip of the nozzle needle 5 to urge the nozzle needle 5 in the valve opening direction.

  The control valve portion 102 having a three-way valve structure has a valve chamber 21 that is always in communication with the control chamber 4 of the nozzle portion 103 via a communication passage 41, and a substantially spherical valve body 2 that is accommodated in the valve chamber 21. ing. A low pressure side seat 22 is formed in the opening provided on the ceiling surface of the valve chamber 21, and a high pressure side seat 23 is formed in the opposed bottom opening, and the valve body 2 is selectively seated on either of the seats 22, 23. It is supposed to be. The low-pressure side seat 22 communicates with the low-pressure passage 13 via the narrowed portion 31 and the passage 32 formed downstream, while the high-pressure side seat 23 communicates with the high-pressure passage 12 via the upstream passage 25. By providing the throttle portion 31 downstream of the low-pressure side sheet 22, the nozzle opening speed can be kept low, and the injection amount controllability is improved. Further, the valve chamber 21 is always in communication with the control chamber 4 of the nozzle portion 103 via the communication passage 41.

  The valve body 2 moves up and down by being pressed by the drive unit 101, and the seat position of the valve body 2 is switched. When the valve body 2 is in the upper end position, the substantially spherical surface is seated on the low-pressure side seat 22 on the ceiling surface of the valve chamber 21 to block communication with the low-pressure passage 13. When the valve body 2 is at the lower end position, the horizontal bottom surface is seated on the high-pressure side seat 23 on the bottom surface of the valve chamber 21 to block communication with the high-pressure passage 12. Accordingly, the pressure in the control chamber 4 communicating with the valve chamber 21, that is, the back pressure of the nozzle needle 5 increases or decreases. If one of the seat portions is a flat sheet, even if the body members B2 and B3 constituting the valve chamber 21 are misaligned, the sheet failure between the valve body 2 and the low-pressure side or high-pressure side sheets 22 and 23 is less likely to occur. There is a leak prevention effect. In addition, processing becomes easy.

  A valve spring 24 is disposed at the end of the passage 25 on the valve chamber 21 side to urge the valve body 2 upward. By disposing the valve spring 24 outside the valve chamber 21, the volume of the valve chamber 21, that is, the volume of the control chamber 4 can be reduced, so that the response is improved. Further, by allowing the valve body 2 to be seated on the low-pressure side seat 22 by the valve spring 24, the high-pressure supply pump can promptly start boosting when the engine is started.

  The drive unit 101 transmits the driving force of the piezo actuator 6 as an actuator to the valve body 2 of the control valve unit 102 using the hydraulic transmission device 61 and the sliding pin member 3. The piezo actuator 6 is accommodated in the upper end portion of the vertical hole formed in the body member B1, and the hydraulic transmission device 61 is accommodated in the lower end portion. The piezo actuator 6 has a piezo stack in which piezoelectric ceramic layers such as PZT and electrode layers are alternately stacked, and is charged and discharged by a drive circuit (not shown) with the stacking direction (vertical direction) as an expansion / contraction direction. There is a low pressure passage 13 at the side of the vertical hole, and the lower end thereof is connected to a passage 32 formed in the body member B2.

  The hydraulic transmission device 61 includes a cylinder 15 in the lower half of the vertical hole, a piezo piston 62 as a first piston slidably provided in the cylinder 15, and a second piston slidably provided in the piezo piston 62. As a valve piston 64 and an oil tight chamber 63 filled with hydraulic oil between both pistons. The configuration of the pistons 62 and 64 and the oil-tight chamber 63 is a characteristic part of the present invention and will be described in detail below.

  The piezo piston 62 has a cylindrical shape with an upper end closed, and the lower end surface of the piezo actuator 6 is in contact with the upper end surface thereof. The piezo piston 62 has a constant diameter and an outer peripheral surface that is in close contact with the inner peripheral surface of the cylinder 15. The piezoelectric piston 62 is guided by the inner peripheral surface and slides in the vertical direction. A ring member 7 having a smaller diameter than the valve piston 64 is integrally provided at the lower end side of the piezo piston 62, and a piezo preset spring 65 as a ring-shaped spring is disposed between the ring member 7 and the body member B2. The piezo preset spring 65 is a disk spring having a C-shaped cross section, and is arranged so that the inner diameter side edge is in contact with the lower end surface of the ring member 7. As a result, an upward load is applied to the lower end surface of the piezo piston 62, the piezo piston 62 is pressed against the piezo actuator 6 and can be displaced integrally, and is used as a piezo preset force of the piezo actuator 6.

  The piezo preset spring 65 may be a ring-shaped spring, and may have other shapes such as a corrugated spring in addition to a disc spring. Setting the piezo preset spring 65 on the lower end side of the piezo piston 62 makes it easy to set the set length. By interposing the ring member 7 as in this embodiment, the outer diameter of the piezo preset spring 65 can be increased and the spring constant can be decreased. Moreover, the assembly is easy and the effect of suppressing the load fluctuation at the time of displacement is obtained. In addition, as shown as 2nd Embodiment in FIG. 2, it can also comprise with a disk spring with a cross-sectional reverse C shape. In this case, the ring member 7 is not provided, and the outer diameter side edge portion is disposed so as to be in contact with and supported by the stepped portion 71 provided on the lower end surface of the piezo piston 62. In this way, there is no friction between the inner and outer periphery due to displacement, and the number of parts can be reduced.

Also, a plurality of disc springs can be used. Arbitrary spring constants can be realized by arranging them in appropriate combination in series or in parallel. In that case, a guide member can be newly used in addition to using the lower end of the small diameter of the valve piston 64 or the inner diameter of the injector body as a guide for the disc spring. An example thereof will be described with reference to FIG.

  FIGS. 3A and 3B show the third and fourth embodiments, in which two disc springs are used as the piezo preset spring 65, and the cross-sectional inverted C-shape is directly above the disc-shaped spring. Combined so that the disc springs overlap. Thus, when a plurality of disc springs are used in series, the spring constant can be reduced. At this time, in the third embodiment shown in FIG. 3A, the small-diameter lower end 642 of the valve piston 64 is set to have a constant diameter, and the outer peripheral surface thereof becomes an inner diameter guide of the ring-shaped piezo preset spring 65. ing. The inner circumferential surface 73 of the body member B1 can be used as an outer diameter guide for the piezo preset spring 65. In this case, since the disc spring does not contact the valve piston 64, the driving force of the valve piston 64 is not lost. Further, as shown in the drawing, a ring plate-like height adjustment plate 72 can be disposed below the piezo preset spring 65.

  The fourth embodiment of FIG. 3B is also an example in which two disc springs are overlapped to form a piezo preset spring 65. In this embodiment, the guide member 74 is further provided separately. The guide member 73 has a cylindrical portion protruding upward at the center of the ring plate, and the outer peripheral surface of the cylindrical portion is used as an inner diameter guide of the piezo preset spring 65. Since the cylindrical portion is disposed around the lower end portion 641 of the small diameter of the valve piston 64 with a gap, it does not contact the valve piston 64 even as an inner diameter guide, and the driving force is not lost. Further, the guide member 74 can also serve as the height adjustment plate 72.

  The valve piston 64 has a sliding portion having a constant diameter inserted into the cylindrical portion of the piezo piston 62 from below, and is slidable with respect to the inner peripheral surface thereof. The lower end portion of the small diameter of the valve piston 64 protrudes downward from the cylindrical portion of the piezo piston 62 and is in contact with the sliding pin member 3. A space surrounded by the upper inner wall surface of the cylindrical portion of the piezo piston 62 and the upper end surface of the valve piston 64 is filled with fuel as hydraulic oil to form an oil tight chamber 63. A spring member 66 such as a coil spring or a corrugated spring is disposed in the oil tight chamber 63 to urge the valve piston 64 toward the valve body 2 of the control valve portion 102. Arranging the spring member 66 in the oil-tight chamber 63 is preferable because the configuration can be simplified.

  In the upper end portion of the piezo piston 62, there is provided a check valve 8 that allows the oil-tight chamber 63 and the low-pressure passage 13 to communicate with each other and allows only hydraulic oil to flow toward the oil-tight chamber. The check valve 8 is configured by disposing ball-shaped valve bodies in passages that open to the oil-tight chamber 63 and the low-pressure passage 13 respectively. The check valve 8 can replenish the fuel from the low pressure passage 13 to the oil-tight chamber 63 when the pressure in the oil-tight chamber 63 decreases due to a fuel leak or the like.

  The sliding pin member 3 is slidably provided in a sliding hole formed in the body member B <b> 2, and a lower end thereof is in contact with the valve body 2 in the valve chamber 21. Both ends of the sliding pin member 3 are formed in a pin shape having a small diameter, and a throttle portion 31 is opened in an annular space formed between the pin-shaped tip on the valve body 2 side and the sliding hole. . Therefore, when the sliding pin member 3 pushes down the valve body 2, the valve chamber 21 and the low pressure passage 13 communicate with each other through the annular space and the throttle portion 3.

  Accordingly, when the piezo actuator 6 extends and presses the piezo piston 62 downward, the pressing force is transmitted to the valve piston 64 via the fuel in the oil-tight chamber 63. Since piezoelectric ceramics such as PZT constituting the piezo actuator are different from metal in the amount of thermal deformation, it is preferable to use a displacement transmission device utilizing hydraulic pressure as described above as means for mixing both. Thereby, the amount of thermal deformation that differs between the members can be absorbed by the fuel inflow and the fuel leak into the oil-tight chamber 63, and good transmission performance can be maintained.

  Next, the operation of the injector 1 in this embodiment will be described. FIG. 1 shows a state where the piezo actuator 6 is contracted in a discharged state. The valve body 2 is urged upward by the fuel pressure in the valve chamber 21 and the force of the valve spring 24 and is at the upper end position for closing the low pressure side seat 22, and the throttle portion 31, the passage 32 and the valve chamber reaching the low pressure passage 13. Communication with 21 is cut off. The high pressure side seat 23 is open, and the control chamber 4 communicating with the valve chamber 21 via the communication passage 41 is at a high pressure due to fuel flowing from the high pressure passage 12 via the passage 25 and the high pressure side seat 23. . The nozzle needle 5 is seated on the nozzle seat 55 by the pressure of the control chamber 4 and the biasing force of the spring 56, and fuel is not injected.

  From this state, when the piezo actuator 6 is energized, the piezo actuator 6 is charged and extended. Along with this, the piezo piston 62 moves downward and the hydraulic oil (light oil here) in the oil-tight chamber 63 is compressed. When the valve piston 64 is moved downward by the pressure of the hydraulic oil and the sliding pin member 3 pushes down the valve body 2, the valve body 2 is separated from the low-pressure side seat 22, and is further displaced downward to cause the high-pressure side seat 23. Sit on. As a result, the control chamber 4 communicates with the low pressure passage 13 via the valve chamber 21, the low pressure side seat 22, the throttle portion 31, and the passage 32, and the pressure in the control chamber 4 drops. When the downward biasing force of the nozzle needle 5 falls below the upward biasing force, the nozzle needle 5 moves away and fuel injection is started.

  Next, when the piezo actuator 6 is discharged again and contracted, the piezo piston 62 moves upward, the pressure in the oil-tight chamber 63 drops, and the push-down force of the valve body 2 is released. Therefore, the valve body 2 is seated on the low pressure side seat 22, the space between the control chamber 4 and the low pressure passage 13 is cut off, and the pressure of the control chamber 4 rises again by the high pressure fuel flowing in through the passage 25, and the nozzle needle 5 Sits down and the injection ends.

  According to this embodiment, the displacement of the piezo actuator 6 can be efficiently transmitted using the hydraulic transmission device 61, and fuel injection can be performed with good controllability. In addition, since the hydraulic transmission device 61 is configured so that the piezo piston 62 is cylindrical and the valve piston 64 slides on the inner periphery thereof, the overall length of the device can be significantly shortened while ensuring the piston sliding length. it can. This effect is apparent when compared with a configuration in which the piezo piston 62 and the valve piston 64 are arranged in a straight line as shown in FIG. Further, in the present embodiment, since the vertical hole of the body member B1 is used as the cylinder 15, as compared with the configuration in which the cylinder forming member 16 is disposed in the vertical hole and the piezo piston 62 and the valve piston 64 are guided as shown in FIG. Stable sliding is possible. Therefore, a compact, high-response and high-performance injector 1 can be realized.

  FIG. 4 shows another configuration example of the piezo piston 62 according to the fifth embodiment of the present invention. The overall configuration and basic operation of the injector 1 are the same as those in the first embodiment, and a description thereof will be omitted. As shown in FIG. 4, in the present embodiment, the outer diameter of the piezo piston 62 is not set to a constant diameter, and the upper end 621 and the lower end 622 serving as a guide portion are set to have larger diameters than other portions. Thereby, only the outer peripheral surfaces of the upper end portion 621 and the lower end portion 622 serving as the guide portions abut against the cylinder 15 and slide, and a gap is formed between the intermediate portion of the piezo piston 62 and the cylinder 15. In this way, by adopting a configuration in which the piezo piston 62 is guided at the two positions of the upper end portion 621 and the lower end portion 622, it is possible to ensure slidability even when a problem such as deformation occurs in the body member B1.

  FIG. 5 is a sixth embodiment of the present invention and shows another configuration example of the check valve 8 and the oil tight chamber 63. The overall configuration and basic operation of the injector 1 are the same as those in the first embodiment, and a description thereof will be omitted. As shown in FIG. 5, in the present embodiment, the check valve 8 is configured using a check valve member 81 arranged on the upper side of the piezo piston 62. The check valve member 81 has a substantially conical recess 83 opened at the lower end surface, and a ball-shaped valve element 82 is accommodated in a chamber surrounded by the recess 83 and the upper end surface of the piezo piston 62. An opening 84 connected to a passage 85 provided in the check valve member 81 is formed on the ceiling surface of the recess 83, and the passage 85 opens to the side surface of the check valve member 81 and communicates with the low pressure passage 13. Yes. The bottom of the recess 83 is formed to have a slightly larger diameter, and one or more passages 86 extending through the upper end surface of the piezo piston 62 to the oil-tight chamber 63 are opened in the outer periphery of the large diameter.

  The ball-shaped valve body 82 is held in a chamber surrounded by the recess 83 and the upper end surface of the piezo piston 62 and is moved in the vertical direction by the pressure of the oil-tight chamber 63. When the pressure in the oil tight chamber 63 decreases due to a fuel leak or the like, as shown in the drawing, the ball-shaped valve body 82 moves to the lower end position, and passes from the low pressure passage 13 through the passage 85, the opening 84, the recess 83, and the passage 86, Fuel is supplied to the oil tight chamber 63. The passage 86 is formed at a position that is not closed even when the valve body 82 is at the lower end position. When the pressure in the oil tight chamber 63 rises, the ball-shaped valve body 82 rises with the fuel pressure flowing into the recess 83 from the passage 86 and closes the opening 82. The lift amount is determined by the shape of the ball-shaped valve body 82 and the recess 83. By setting it as such a structure, the check valve 8 can be comprised simply, without providing a spring member.

  The check valve member 81 is sandwiched between the piezoelectric actuator 6 and the piezoelectric piston 62. The lower end surface of the check valve member 81 and the upper end surface of the piezo piston 62 are brought into contact with each other by being pressed against each other by a piezo preset spring 65 (see FIG. 1) disposed on the lower end side of the piezo piston 62. With this configuration, steps such as press-fitting and joining are not necessary. Further, by using the piezo preset spring 65 of the piezo actuator 6, oil tightness can be ensured without increasing the number of members. Further, the upper end surface of the check valve member 81 is formed in a gentle substantially concave conical surface shape, and is in contact with the lower end surface of the piezoelectric actuator 6 having a substantially convex spherical shape. By doing so, even if a deviation occurs in the positional relationship between the two members (angle, axis, etc.), the driving force can be transmitted by absorbing the deviation. In order to obtain this effect, the upper end surface of the check valve member 81 and the lower end surface of the piezo actuator 6 are not limited to the shape described above, but may be any shape that provides the same effect. For example, various combinations such as one having a substantially spherical shape and the other having a substantially convex spherical shape or a substantially concave conical surface shape can be employed, and the number of parts can be reduced by also serving as a misalignment absorbing member.

  A concave portion 641 is formed on the upper end surface of the valve piston 64 constituting the oil tight chamber 63, and a columnar volume reducing member 67 is disposed in the concave portion 641. The coil spring 66 is disposed in the recess 641 so as to surround the volume reduction member 67. In this way, the coil spring 66 can be supported with a simple configuration, and the volume of the oil-tight chamber 63 can be reduced, so that responsiveness can be improved and driving force transmission efficiency can be improved.

  FIG. 6 shows another example of the configuration of the piezo piston 62 according to the seventh embodiment of the present invention. The overall configuration and basic operation of the injector 10 are the same as those in the first embodiment, and a description thereof will be omitted. As shown in FIG. 6, in this embodiment, the piezo piston 62 with the upper end closed is composed of two members: a cylindrical portion 62b that opens at both ends and a plate member 62a that closes the upper end. The lower end surface of the plate member 62a and the upper end surface of the cylindrical portion 62b are pressed against each other by a piezo preset spring 65 to ensure oil tightness. The other oil tight transmission device 61 and the check valve 8 are the same as those in the fourth embodiment.

  According to the present embodiment, the piezo piston 62 is divided into two members, that is, the plate member 62a and the cylindrical portion 62b on the closed end side, so that the cylindrical portion (particularly on the closed end side) is compared with the case of using one member. Can be manufactured at low cost. In addition, when a step is not required on the lower end surface of the cylindrical portion 62b, a vertically symmetrical structure can be obtained, so that assembly is facilitated.

  As described above, according to the present invention, in the mechanism for transmitting the displacement of the actuator via hydraulic pressure, one of the two pistons is formed in a cylindrical shape and accommodates the other, so that the influence of the sliding length on the total length of the apparatus Will greatly reduce. Any actuator may be used as long as it is an element that generates displacement when energized. Examples of the actuator include a magnetostrictive element and the like in addition to the piezoelectric element used in each of the above embodiments. Therefore, the whole injector can be formed compactly.

  In the above embodiment, the upper end surface of the cylindrical portion 62b and the lower end surface of the plate member 62a constituting the piezo piston are in close contact with the piezo preset spring 65, but as shown in FIG. 7 as an eighth embodiment, The plate member 62a may be inserted into the inner diameter of the cylindrical portion 62b. In this case, the plate member 62a is in close contact with the check valve member 81 by the spring member 66, and the cylindrical portion 62b is in close contact with the check valve member 81 by the piezo preset spring 65 to ensure oil tightness. In the present embodiment, the plate member 62a is not in contact with the inner diameter of the injector body and does not cause relative displacement with respect to the cylindrical portion 62b, so that one sliding portion can be reduced. Here, the spring member 66 is a corrugated spring and has an advantage that the volume of the oil-tight chamber 63 can be reduced.

  FIG. 8 shows a ninth embodiment of the present invention. In each of the above embodiments, the preset spring 65, which is a ring-shaped spring, is used to apply a preset force to the piezo actuator 6, but in this embodiment, a slit spring 68 is used instead of the ring-shaped spring. The overall configuration and basic operation of the injector 1 are the same as those in the first embodiment, and a description thereof will be omitted. As shown in FIG. 8, in this embodiment, the upper end 621 of the piezo piston 62 is used as a guide portion having a larger diameter than the other portions, and only the outer peripheral surface of the upper end 621 contacts and slides on the cylinder 15. . A gap is formed between the small diameter cylindrical portion of the piezo piston 62 and the cylinder 15, and a slit spring 68 is disposed in this gap.

  The slit spring 68 has a known configuration, and imparts spring characteristics by, for example, forming a plurality of circumferential slits in a cylindrical material. The upper end portion 621 of the piezo piston 62 is provided with a seat surface 623 that supports the upper end edge of the slit spring 68, and the slit spring applies a preload to the piezo actuator 6 via the seat surface 623. A ring-shaped member 75 is provided on the lower end side of the slit spring 68, and its upper surface forms a seating surface that supports the lower end edge of the slit spring 68. The outer periphery of the cylindrical portion of the piezo piston 62 serves as an inner peripheral guide for the slit spring 68. In this embodiment, the coil spring 66 is not disposed in the oil-tight chamber 63 but is disposed on the outer periphery of the lower half of the valve piston 64 that protrudes below the piezo piston 62. A flange 643 is provided on the outer periphery of the lower half of the valve piston 64, and the coil spring 66 is held between the flange 643 and the lower end surface of the piezo piston 62.

  The ring-shaped member 75 is used as a height adjusting member for adjusting the set length of the slit spring 68. The ring-shaped member 75 may have a shape having a cylindrical guide portion on the inner periphery or the outer periphery, like the guide member 74 (see FIG. 3B). The ring-shaped member 75 is placed on the upper surface of the body member B <b> 2 so as to be in close contact with the inner peripheral surface of the lower end portion of the cylinder 15. As a result, the space between the passage 32 that opens to the upper surface of the body member B2 and connects to the low pressure passage 13 and the internal space of the cylinder 15 is blocked by the ring-shaped member 75, so that leakage from the control valve portion 102 is driven. It is possible to suppress the flow into the hydraulic transmission device 61 and the piezo actuator 6 of the portion 101, and to prevent air from entering the oil tight chamber 63 and the occurrence of cavitation erosion.

  In the above embodiment, the control valve portion 102 has a three-way valve structure, but a two-way valve structure that switches between the communication state and the cutoff state between the valve chamber 21 and the low pressure passage 13 instead of the three-way valve structure. Of course, it can be applied to the above injectors. Moreover, a valve body shape and other structures can also be changed.

It is sectional drawing which shows the whole structure of the injector which shows the 1st Embodiment of this invention. It is sectional drawing which shows the principal part structure of the injector which shows the 2nd Embodiment of this invention. (A), (b) is sectional drawing which shows the principal part structure of the injector which shows the 3rd, 4th embodiment of this invention, respectively. It is sectional drawing which shows the principal part structure of the injector which shows the 5th Embodiment of this invention. It is sectional drawing which shows the principal part structure of the injector which shows the 6th Embodiment of this invention. It is sectional drawing which shows the principal part structure of the injector which shows the 7th Embodiment of this invention. It is sectional drawing which shows the principal part structure of the injector which shows the 8th Embodiment of this invention. It is sectional drawing which shows the principal part structure of the injector which shows the 9th Embodiment of this invention. It is sectional drawing which shows the principal part structure of the injector which has arrange | positioned two pistons on a straight line.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injector 12 High pressure path 13 Low pressure path 101 Nozzle part 102 Control valve part 103 Piezo drive part 2 Valve needle 21 Valve chamber 22 Low pressure side seat 23 High pressure side sheet 4 Control chamber 41 Communication path 5 Nozzle needle 52 Oil reservoir chamber 54 Injection hole 6 Piezo actuator (actuator)
61 Hydraulic transmission device 62 Piezo piston (first piston)
63 Oiltight chamber 64 Valve piston (second piston)
65 Piezo preset spring (ring shaped spring)
66 Spring member 67 Volume reduction member 68 Slit spring 7 Ring member 8 Check valve 81 Check valve member 82 Valve body 83 Recess 84 Opening 85, 86 Passage

Claims (22)

An injector for injecting fuel supplied from a common rail through a high-pressure passage, the control chamber for applying a pressure in the valve closing direction to the nozzle needle, and opening and closing between the control chamber and the low-pressure passage. A control valve that increases and decreases the pressure of the control valve, and a drive unit that drives the valve body of the control valve, and the drive unit slides in the cylinder integrally with the actuator, and an actuator that generates displacement by energization. A piston, a second piston for driving the valve body, and an oil-tight chamber formed between the two pistons. The first piston has a cylindrical shape with an upper end closed, and the second piston is vertically moved in the cylindrical portion. Slidably inserted in the direction, filled with hydraulic oil in the space surrounded by the upper inner wall surface of the cylindrical portion and the upper end surface of the second piston to form the oil tight chamber ,
A ring-shaped spring that loads an upward load serving as a preset force of the actuator is disposed on the lower end side of the first piston,
The ring-shaped spring is a single disc in series, or a plurality of disc springs in various combinations using series or parallel or both, and the inner diameter side edge is provided on the lower end side of the first piston. An injector for a common rail, which is disposed so as to abut on a lower end surface of a ring member smaller than a sliding diameter of the second piston . An injector for injecting fuel supplied from a common rail through a high-pressure passage, the control chamber for applying a pressure in the valve closing direction to the nozzle needle, and opening and closing between the control chamber and the low-pressure passage. A control valve that increases and decreases the pressure of the control valve, and a drive unit that drives the valve body of the control valve, and the drive unit slides in the cylinder integrally with the actuator, and an actuator that generates displacement by energization. A piston, a second piston for driving the valve body, and an oil-tight chamber formed between the two pistons. The first piston has a cylindrical shape with an upper end closed, and the second piston is vertically moved in the cylindrical portion. Slidably inserted in the direction, filled with hydraulic oil in the space surrounded by the upper inner wall surface of the cylindrical portion and the upper end surface of the second piston to form the oil tight chamber,
On the outer periphery of the first piston, a slit spring for applying an upward load as a preset force of the actuator is disposed,
A ring that forms a seat surface that supports the upper end side of the slit spring on the outer periphery of the upper end of the first piston, and that forms a seat surface that supports the lower end side of the slit spring on the outer periphery of the lower end of the second piston. Arranged,
An injector for a common rail , wherein the ring-shaped member is disposed so as to block between a space in the cylinder and the low-pressure passage . An injector for injecting fuel supplied from a common rail through a high-pressure passage, the control chamber for applying a pressure in the valve closing direction to the nozzle needle, and opening and closing between the control chamber and the low-pressure passage. A control valve that increases and decreases the pressure of the control valve, and a drive unit that drives the valve body of the control valve, and the drive unit slides in the cylinder integrally with the actuator, and an actuator that generates displacement by energization. A piston, a second piston for driving the valve body, and an oil-tight chamber formed between the two pistons. The first piston has a cylindrical shape with an upper end closed, and the second piston is vertically moved in the cylindrical portion. Slidably inserted in the direction, filled with hydraulic oil in the space surrounded by the upper inner wall surface of the cylindrical portion and the upper end surface of the second piston to form the oil tight chamber,
A spring member disposed on an upper end side or an outer periphery of the second piston and biasing the second piston toward the valve body;
A common rail injector , wherein a concave portion is provided in an upper end portion of the second piston, a volume reducing member is accommodated therein, and a coil spring serving as the spring member is disposed around the volume reducing member . The common rail injector according to any one of claims 1 to 3, wherein the cylinder is formed by a vertical hole formed in an injector body, and the first piston slides while being guided by an inner peripheral surface thereof . The common rail injector according to claim 4 , wherein a large-diameter portion serving as a guide portion is provided at an upper end portion and a lower end portion of the first piston, and the guide portion is guided to an inner peripheral surface of the cylinder . The common rail injector according to claim 3, wherein a ring-shaped spring for applying an upward load serving as a preset force of the actuator is disposed on a lower end side of the first piston . The ring-shaped spring is a single disc in series, or a plurality of disc springs in various combinations using series or parallel or both, so that the outer edge of the outer side contacts the lower end surface of the first piston. 7. The common rail injector according to claim 6 , wherein the common rail injector is disposed . The ring-shaped spring is a single disc in series, or a plurality of disc springs in various combinations using series or parallel or both, and the inner diameter side edge is provided on the lower end side of the first piston. The common rail injector according to claim 6 , wherein the common rail injector is disposed so as to contact a lower end surface of a ring member smaller than a sliding diameter of the second piston . The common rail injector according to claim 3, wherein a slit spring for applying an upward load serving as a preset force of the actuator is disposed on an outer periphery of the first piston . The common rail injector according to claim 9, wherein a seating surface that supports an upper end side of the slit spring is formed on an upper end outer peripheral portion of the first piston . The common rail injector according to claim 10, wherein a ring-shaped member that forms a seating surface that supports the lower end side of the slit spring is disposed on the outer periphery of the lower end of the second piston . The common rail injector according to claim 11 , wherein the ring-shaped member is disposed so as to block between the space in the cylinder and the low-pressure passage .   The common rail injector according to any one of claims 1 to 12, wherein a check valve is provided between the oil tight chamber and the low pressure passage so as to allow only an inflow of hydraulic oil into the oil tight chamber.   The common rail injector according to claim 13, wherein the check valve does not include a spring member.   The check valve is formed in a plate-like check valve member arranged in close contact with the upper end surface of the first piston, and an abutting portion of the first piston and the check valve member, and accommodates the valve body. The common rail injector according to claim 14, further comprising a chamber and a passage communicating the chamber with the low pressure passage and the oil tight chamber.   The common rail injector according to claim 15, wherein a lower end surface of the check valve member and an upper end surface of the first piston are in contact with each other by being pressed against each other.   The common rail injector according to claim 16, wherein the pressing force of the lower end surface of the check valve member and the upper end surface of the first piston is provided by a spring member that applies a preset force to the actuator.   The common rail injector according to claim 16, wherein the contact end surfaces of the check valve member and the actuator have a shape capable of absorbing misalignment by combining a convex spherical surface and a concave conical surface or a flat surface.   The recess is provided on the lower end surface of the check valve member and the upper end surface of the first piston forms the chamber, and the check valve lift amount is determined by the recess and the valve body disposed therein. The injector for a common rail according to any one of claims 14 to 18.   A passage communicating the chamber and the low-pressure passage is opened in a ceiling surface of the chamber that is closed when the valve element moves to the upper end position due to an increase in pressure in the oil-tight chamber, and the chamber communicates with the oil-tight chamber. 20. The common rail injector according to claim 19, wherein a passage is opened at a bottom surface of the chamber that is not closed when the valve element moves to a lower end position due to a pressure drop in the oil tight chamber.   21. The common rail injector according to claim 1, wherein the closed end portion and the cylindrical portion of the first piston are configured as separate members.   The common rail injector according to any one of claims 1 to 21, wherein the actuator is a piezoelectric actuator.

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