JP4952737B2 - Common rail injector - Google Patents

Description

  The present invention relates to a common rail injector for a diesel engine, and more particularly to an injector that controls a control chamber pressure for raising and lowering a nozzle needle with a three-way valve.

  2. Description of the Related Art In a diesel engine, a common rail type fuel injection device that stores a high pressure fuel by providing a common rail common to each cylinder is known. High pressure fuel is pumped from the fuel supply pump to the common rail and controlled to a predetermined pressure, and fuel is injected by driving the injector of each cylinder at a predetermined timing. Common rail injectors generally have a control chamber that applies a pressure in the valve closing direction to the nozzle needle and a control valve that controls the pressure in the control chamber. The actuator is driven by the actuator to increase or decrease the pressure in the control chamber. It is the composition to do.

  As the control valve, a three-way valve structure for selectively communicating the control chamber with the high-pressure passage or the low-pressure passage is suitably used. The valve body of the three-way valve is disposed in a valve chamber in which a low-pressure side seat leading to the low-pressure passage and a high-pressure side seat leading to the high-pressure passage are formed, moves between both seats, and switches the seat position. With the three-way valve structure, the valve body is seated on the high-pressure side seat during fuel injection and communication with the high-pressure passage is blocked, so that high-pressure fuel does not flow out through the valve chamber. For example, a piezoelectric actuator is used as the actuator. The actuator is extended by energization to separate the valve body from the low-pressure side seat, and then is seated on the high-pressure side seat. Piezo actuators are expected to provide advanced fuel injection control due to their high responsiveness.

A control valve having a three-way valve structure is described in Patent Documents 1 to 5, for example. Moreover, when it is set as the structure which has an aperture | diaphragm | squeeze downstream of a low voltage | pressure side sheet | seat (patent documents 1-4), it is advantageous in order to suppress the valve opening speed and to improve the controllability of injection quantity.
JP 2000-130614 A JP 2002-227747 A JP 2001-41125 A Special table 2001-500218 gazette JP 2001-140726 A

  By the way, in order to operate the common rail fuel injection device efficiently, it is desirable to reduce the fuel leakage as much as possible. However, Patent Documents 1 and 2 are pressure balance valves, and always leak from the sliding portion. In this case, extra work is required for the pump, and there is a problem that the fuel temperature rises due to leakage and the quality of the fuel changes. In the control valve of Patent Document 3, the valve body is a sphere, and the high-pressure side seat member and the low-pressure side seat member are separate members for accommodating the valve body. However, in this case, as described in Patent Documents 2 and 5, there is a risk of leakage due to the displacement of both members, and it is difficult to use in a region where the lift amount is small.

  Thus, Patent Document 5 proposes to provide a plurality of valve members that can move relative to each other so that they can operate normally even if they are misaligned, but the configuration is complicated. In order to improve the injection amount controllability, it is desirable to increase the nozzle closing speed. In general, it is possible to increase the nozzle closing speed by increasing the high-pressure side seat opening area, but since the piezo actuator has a characteristic in which the displacement and the generated force are inversely proportional, if the high-pressure side seat opening area is large, There is a problem that the valve closing driving force increases and energy efficiency deteriorates.

  An object of the present invention is to reduce the driving force required for closing the high-pressure side seat valve in an injector used in a common rail fuel injection device of a diesel engine, and to reduce the fuel leakage from the control valve with a simple configuration. In other words, the nozzle opening speed is reduced or the nozzle closing speed is increased, thereby increasing the energy efficiency and controlling the injection amount with high accuracy.

  In the first aspect of the invention, the injector for injecting fuel supplied from the common rail through the high-pressure passage has a three-way valve structure for increasing or decreasing the pressure in the control chamber that generates the nozzle back pressure, and the drive unit is energized. Thus, the actuator and the sliding pin member that generate displacement are used. The sliding pin member contacts the valve body of the control valve housed in the valve chamber with the pin-shaped tip, and slides in the sliding hole as the actuator is displaced to selectively select the low-pressure side seat or high-pressure side seat It is supposed to be seated on.

In the present invention, a common communication passage is provided for allowing the fuel in the high pressure passage to flow into the control chamber and for allowing the fuel in the control chamber to flow out from the control chamber, and the control valve and the high pressure passage are provided in the control valve. The pressure in the control chamber is increased / decreased by switching communication / blocking between the passage and the low-pressure passage. Then, a space formed around the pin-shaped tip between the sliding portion of the sliding pin member and the low-pressure side sheet is connected to the low-pressure passage through the throttle portion, and the sliding The relationship between the sliding diameter of the sliding portion and the sheet diameter of the high-pressure side sheet is sliding diameter ≦ the high-pressure side sheet diameter, and the relationship between the sliding diameter of the sliding portion and the sheet diameter of the low-pressure side sheet is the sliding diameter. The pressure in the control chamber communicating with the valve chamber is made to act on the valve body as an assist force in the direction of closing the high pressure side seat .

  According to the above configuration, the nozzle opening speed when the low-pressure side seat is opened is slowed down by the throttle portion set in the space formed around the tip of the sliding pin member, and the pressure in the control chamber is reduced by the pressure of the high-pressure side seat. By acting in the valve closing direction, the high-pressure side valve closing driving force can be reduced. Furthermore, by reducing the sliding diameter, the driving force required for closing the high-pressure side seat valve can be further reduced. Therefore, the high-pressure side seat diameter is increased to increase the nozzle closing speed, and the injection controllability and energy efficiency can be improved with a simple configuration.

  The invention according to claim 2 is configured such that the pressure in the control chamber communicating with the valve chamber acts as an assist force so that the high-pressure side seat closing load is equal to or less than the low-pressure side seat opening load. To do.

  Preferably, energy efficiency can be further improved by adjusting the control chamber pressure so that the high-pressure side seat closing load is equal to or less than the low-pressure side seat opening load.

  In the invention of claim 3, the actuator is a piezo actuator. By applying the present invention to a piezoelectric actuator that has a relationship in which the generated force decreases as the displacement increases, the characteristics can be used efficiently.

  According to the fourth aspect of the present invention, the control chamber pressure at which the nozzle needle can be opened is set to be 50% or more of the supply fuel pressure at the maximum pressure at which the load is maximum. In this way, it is possible to efficiently control the injection amount by making the high-pressure side seat closing load smaller than the opening load of the low-pressure side seat.

  In the invention of claim 5, the sliding pin member and the valve body are separated. Thereby, processing of a sheet part becomes easy.

  In the invention of claim 6, both end portions of the sliding pin member are formed in a pin shape smaller in diameter than the sliding diameter. Thereby, the malfunctioning by incorrect assembly | attachment can be prevented.

  As in the invention of claim 7, the sliding pin member may be a cylindrical pin having a constant diameter over the entire length. In that case, an enlarged diameter portion larger than the sliding diameter is formed at the end of the sliding hole following the low pressure side sheet, and the tip end portion of the sliding pin member is disposed, and the enlarged diameter portion is opened. An aperture is formed in Thereby, the shape of a sliding pin member is simplified and processing becomes easy.

  In the invention of claim 8, the valve body is substantially hemispherical. If the contact surface with the sliding pin member is processed into a spherical surface larger than the curvature of the sphere, the effect of preventing contact with one piece and alleviating the Hertz stress can be obtained.

  According to the ninth aspect of the present invention, at least the sliding surface of the sliding pin member is made of a super hard material or ceramic. Thereby, slidability improves and it can prevent abrasion.

  In the invention of claim 10, the sliding pin member is made of a super hard material having a Young's modulus larger than that of a metal. Thereby, the effect which prevents a deformation | transformation loss can be acquired.

  In the invention of claim 11, the valve spring for biasing the valve body to the low pressure side seat is disposed upstream of the high pressure side seat. Thereby, a valve chamber volume can be made small and responsiveness can be improved.

In the invention of claim 12, the control chamber pressure ratio when the nozzle is opened is kpo, the nozzle seat diameter on which the nozzle needle is seated is Ds, the control chamber sliding diameter is Dc, the nozzle set load is Fk, and the fuel supply pressure from the common rail Is set to Pc, and when Pc = Pcmax (maximum supply pressure), each part is configured so that the following expression is established.
Thereby, the above-described effect of reducing the high-pressure side seat valve opening load and reducing the high-pressure side seat valve closing driving force can be easily obtained.

  The present invention will be described below 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. The injector 1 is provided corresponding to each cylinder of the engine (only one of them is shown here), and is supplied with fuel 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 has a driving part 101 having a piezo actuator 6 as an upper half, and drives a nozzle part 103 having a nozzle needle 5 by using a control valve part 102 having a three-way valve structure to perform fuel injection. . The injector 1 is attached to a combustion chamber wall (not shown), and a high pressure passage communicating with a common rail (not shown) at a fuel introduction port 11 in housing members H1 to H4 in which the components of the respective parts 101 to 103 are accommodated. 12. A passage such as a low pressure passage 13 communicating with a fuel tank (not shown) is formed at the fuel outlet 14 and the housing members H1 to H4 are oil-tightly fastened and fixed by a retainer H5.

  The nozzle portion 103 slidably holds a nozzle needle 5 having a flange 51 on the outer periphery in a cylindrical portion 42 provided at the upper end portion of the housing member H1. The space in the housing member H4 constitutes an oil reservoir chamber 52, and high-pressure fuel is supplied from the common rail through the high-pressure passage 12 that opens to the upper wall. A sack portion 53 is formed at the lower end of the housing member H4, and an injection hole 54 is formed through the sack portion 53 forming wall.

  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 housing member H3 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 flange 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. A throttle part 32 for setting the nozzle valve opening speed is formed downstream of the low-pressure side seat 22 and communicates with the low-pressure passage 13 via passages 33 and 34. A passage 25 formed upstream of the high-pressure side seat 23 communicates with the high-pressure passage 12. 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. Along with this, the valve chamber 21 communicates with the high pressure passage 12 or the low pressure passage 13, and 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.

  The valve body 2 is constituted by one member, and the valve chamber 21 is constituted by abutting two housing members H2 and H3. The throttle portion 32 and the passage 33 are formed in the housing member H2, and the communication passage 41 and the passage 25 are formed in the housing member H3. In the present embodiment, a throttle smaller than the opening area of the low pressure side seat 22 is not provided between the control chamber 4 and the valve chamber 21. This is because if the aperture is set here, the nozzle closing speed is reduced. There may or may not be a throttle for setting the valve closing speed upstream of the high-pressure side seat 23, but this embodiment does not provide a throttle. Details of the configurations of the valve body 2, the low-pressure side seat 22, and the high-pressure side seat 23 will be described later.

  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. When the high-pressure supply pump starts to increase pressure when starting the engine, it is necessary to bias the valve body 2 to the low-pressure side seat 22 in order to increase the pressure quickly. However, if the valve spring 24 for that purpose is disposed in the valve chamber 21, the volume of the valve chamber 21, that is, the volume of the control chamber 4 increases, and the responsiveness decreases. Therefore, it is desirable to arrange the valve spring 24 upstream of the high-pressure side seat 22 as in this embodiment.

  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 piezoelectric actuator 6 is accommodated in the upper end portion of the vertical hole formed in the housing member H1, 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. A space in the vertical hole is a low-pressure passage 13, and a passage 33 on the housing member H <b> 2 side is connected to a passage 34 formed on the lower side thereof.

  The hydraulic transmission device 61 includes a cylindrical cylinder member 15 in which a first piston 62 and a second piston 64 having the same diameter are slidably provided, and an oil-tight chamber 63 filled with hydraulic oil is provided between the pistons. Become. The first piston 62 has a large diameter upper end projecting above the cylinder member 15 and abutting against the lower end surface of the piezo actuator 6, and a piezo spring 65 disposed between the large diameter upper end portion and the cylinder member 15 upper end surface. However, a certain initial load is applied to the piezo actuator 6 via the first piston 62. As a result, the first piston 62 moves up and down integrally with its expansion and contraction while maintaining contact with the piezoelectric actuator 6.

  A valve spring 63 is disposed in the oil tight chamber 63 to urge the second piston 64 downward, and a lower end surface of the second piston 64 is in contact with the sliding pin member 3. The sliding pin member 3 is slidably provided in a sliding hole 31 formed in the housing member H <b> 2, and a lower end thereof is in contact with the valve body 2 in the valve chamber 21. The sliding hole 31 is formed to communicate with the vertical hole of the housing member H1 and the valve chamber 21. Accordingly, when the piezo actuator 6 extends and presses the first piston 62 downward, the pressing force is converted into hydraulic pressure in the oil-tight chamber 63 and transmitted to the second piston 64. The second piston 64 drives the valve body 2 via the sliding pin member 3. The sliding pin member 3 is formed in a pin shape whose both ends are smaller than the sliding diameter, one of which is in contact with the lower end surface of the second piston 64 and the other is in contact with the upper end surface of the valve body 2.

  As shown in FIG. 2A, between the sliding portion of the sliding pin member 3 and the low pressure side sheet 22, the pin-shaped tip end portion 3 a on the valve body 2 side is between the sliding hole 31. An annular space is formed, and a throttle portion 32 is opened on the side wall of the sliding hole 31 facing the annular space. The sliding pin member 3 only needs to have a small diameter at least at the distal end portion 3a, whereby the low pressure side seat diameter can be formed smaller (when the sliding diameter is constant), and the low pressure side seat valve opening drive is performed. The power can be reduced. The valve body 2 has a flat hemispherical shape and is disposed in the valve chamber 21 so that the spherical surface is on the upper side. The contact surface of the valve body 2 with the sliding pin member 3 is processed into a spherical surface having a larger curvature than the original curvature of the valve body. This is for preventing the sliding pin member 3 per piece and alleviating the Hertz stress. The valve chamber 21 has a conical low-pressure side sheet 22 in contact with the spherical surface of the valve body 2 on the ceiling surface where the sliding hole 31 opens, and a flat surface of the valve body 2 on the bottom surface where the passage 25 opens. The high-pressure side sheet | seat 23 of the horizontal surface shape which contacts is formed.

  Thus, by making one of the seat portions into a flat sheet, even if the housing members H2 and H3 constituting the valve chamber 21 are displaced, the seat between the valve body 2 and the low-pressure side or high-pressure side sheets 22 and 23 Defects are less likely to occur. Therefore, leakage can be prevented and processing is facilitated. In addition, when considering the catching (engagement) of the foreign matter on the sheet part, the smooth spherical-conical sheet is less likely to be caught than the flat sheet having the corners. When a foreign object is caught in the high-pressure side seat part and the sheet becomes defective, the injection amount decreases, but when a foreign object is caught in the low-pressure side sheet part and the valve closing is delayed, the nozzle is closed. There is a possibility that the injection amount may increase with a delay in timing, and in order to prevent this, it is desirable that the low-pressure side seat portion has a smooth spherical-conical seat shape.

  The sliding pin member 3 is preferably configured to use an ultra-hard material or ceramic at least on the sliding surface in order to prevent wear and secure slidability. In addition, it is preferable to use a member having a high Young's modulus such as a super hard material in order to prevent deformation loss. Further, in the present embodiment, the sliding pin member 3 is a separate member from the valve body 2, but they may be combined into one member. By using a separate member, processing of the low pressure side seat portion of the valve body 2 is facilitated. As described above, in order to form the annular space between the sliding pin member 3 and the sliding hole 31, the valve body 2 side may be formed in a pin shape having a small diameter. As in the present embodiment, both ends have the same pin-like shape. Thereby, since there is no distinction between upper and lower, it is easy to assemble, and malfunction due to incorrect assembly can be prevented.

  Alternatively, as shown in FIG. 3, the sliding pin member 3 may be a cylindrical pin having the same overall length. In this case, the end portion of the slide hole 31 where the tip portion contacting the valve body 2 is located between the slide portion and the low-pressure side sheet 22 is defined as an enlarged portion 32a larger than the slide diameter. The aperture portion 32 may be formed. This simplifies the shape of the sliding pin member 3 and facilitates processing. This is particularly advantageous when the sliding pin member 3 is made of a difficult-to-work material such as a super hard material.

  In the present embodiment, the relationship between the sheet diameters of the low-pressure side sheet 22 and the high-pressure side sheet 23 is such that the low-pressure side sheet diameter ≦ the high-pressure side sheet diameter, preferably the low-pressure side sheet diameter <the high-pressure side sheet diameter. Thus, by increasing the high pressure side seat opening area larger than the low pressure side seat opening area, the pressure in the control chamber 4 can be quickly increased when the nozzle is closed, and the nozzle closing speed can be increased. Therefore, when processing the valve body 2 from a spherical member, the seat plane formed on the valve body 2 is formed near the center of the sphere. When the seat plane is away from the center of the sphere and the low-pressure side seat diameter is desired to be smaller than the high-pressure side seat diameter, the conical surface of the housing member H2 serving as the low-pressure side seat 22 has a cone apex angle close to 180 °. , The stability of the sheet will be weakened. The relationship between the sliding diameter of the sliding pin member 3 and the sheet diameters of the low-pressure side sheet 22 and the high-pressure side sheet 23 is: sliding diameter ≦ high-pressure side sheet diameter, sliding diameter ≦ low-pressure side sheet diameter. By reducing the sliding diameter, the driving force required for the on-off valve, particularly the high-pressure side valve closing can be reduced.

  The low pressure side seat 22 should have a small seat diameter in order to reduce the low pressure side seat opening load. As shown in FIG. 2A, when the low pressure side seat 22 is closed, the inside of the valve chamber 21 is at a high pressure (common rail supply pressure Pc), and this supply pressure Pc is directed upward to the low pressure side seat opening area. It is working. Therefore, by reducing the seat diameter of the low-pressure side seat 22, the low-pressure side seat opening load can be reduced and the driving force required for opening the valve can be reduced.

  Furthermore, in order to ensure the valve closing force of the high pressure side seat 23 having a large seat diameter, the fuel pressure in the valve chamber 21 is used as an assist pressure when the high pressure side seat 23 is closed. Thereby, the high pressure side valve closing driving force can be made smaller than the high pressure side seat opening area × the supply pressure. As shown in FIG. 2B, in the configuration having the throttle portion 32 downstream of the low pressure side seat 22, the pressure in the valve chamber 21 when the low pressure side seat is opened, that is, the pressure in the control chamber 4 is higher than that in the low pressure passage 13. . Therefore, by maintaining this pressure high as long as the nozzle needle 5 can be opened, the high-pressure side seat closing load is made as small as possible. When the control chamber pressure ratio kpo (the ratio of the control chamber 4 pressure at which the nozzle needle 5 can be opened) to the supply pressure is used when the nozzle is opened, the pressure in the valve chamber 21 is represented by kpo · Pc, and this pressure kpo · The pressure Pc · (1-kpo) obtained by subtracting Pc from the supply pressure Pc acts upward on (high-pressure side sheet opening area−low-pressure side sheet opening area).

Specifically, in the normal use region, the nozzle needle 5 does not fully lift and come into contact with the stopper (the upper end surface of the control chamber), and at least in the region where the supply pressure Pc is half or more of the maximum supply pressure Pcmax, Various design values are determined so that the four pressures do not become less than half of the supply pressure Pc. Preferably, the control chamber pressure ratio kpo is set so that the high-pressure side seat closing load is equal to or smaller than the low-pressure side seat closing load. As a typical example, when the sliding diameter of the sliding pin member 3 is φ0.8, the low pressure side seat diameter is φ1.2, the high pressure side seat diameter is φ1.5, and the maximum supply pressure is 200 MPa, the nozzle is opened. FIG. 4 shows the relationship between the control chamber pressure ratio kpo, the low-pressure side seat opening load, and the high-pressure side seat closing load. From this figure, the higher the control chamber pressure ratio kpo expressed by the following formula, the smaller the high-pressure side seat closing load becomes. You can see that it can be made smaller.

  In general, the output characteristics of the piezo actuator 6 are such that the generated force decreases when the piezo displacement is large. Since the generated force is small on the high pressure side seat 23 side where the displacement is large, driving energy increases if an attempt is made to secure the valve closing force of the high pressure side seat 23 when the seat diameter is large. Thus, when using the piezo actuator 6 in which the generated force decreases as the displacement increases, if the configuration of the present invention is used and the fuel pressure in the valve chamber 21 is used as the assist force, the high-pressure side seat closing load is reduced. This is advantageous. Specifically, the nozzle sheet diameter, the nozzle sliding diameter, and the nozzle set load are determined so as to satisfy the above formula.

  Next, the operation of the injector 1 having the above configuration will be described. FIG. 2A shows a state where the piezo actuator 6 of FIG. 1 is contracted in a discharged state. The valve body 2 is in an upper end position that closes the low-pressure side seat 22, and communication between the throttle portion 32, the passage 33, and the valve chamber 2 reaching the low-pressure passage 13 is blocked. The valve chamber 2 is at a high pressure by the fuel flowing from the high pressure passage 12 through the passage 25 and the high pressure side seat 23. At this time, the control chamber 4 communicating with the valve chamber 2 via the communication passage 41 is also at a high pressure. 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.

  When the piezo actuator 6 is energized from this state, the piezo actuator 6 is filled and extended. Along with this, the first piston 62 moves downward and the hydraulic oil (here, light oil) in the oil-tight chamber 63 is compressed. When the second piston 64 moves 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 a high-pressure side seat. Sitting on 23. 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 32, and the passage 33, and the pressure in the control chamber 4 drops, and the downward biasing force of the nozzle needle 5. Falls below the upward biasing force, the nozzle needle 5 is separated and fuel injection is started. At this time, since the throttle portion 32 is provided downstream of the low-pressure side sheet 22, the pressure drop in the control chamber 4 becomes gentle and the nozzle opening speed becomes small.

  Further, since the pressure kpo · Pc in the valve chamber 21 acts as an assisting force in the direction of closing the high-pressure side seat 23, the high-pressure side seat closing load becomes equal to or less than the low-pressure side seat opening load, and the high-pressure side closing is performed. The valve driving force can be reduced. Therefore, the output characteristics of the piezo actuator 6 can be used efficiently.

  When the piezo actuator 6 is discharged and contracted again, the first 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 needle 3 Sit down and the injection ends. At this time, since the low-pressure side seat diameter is equal to or less than the high-pressure side seat diameter, the pressure in the control chamber 4 rises quickly and the nozzle closing speed increases.

  FIG. 5 is a diagram showing the relationship between the nozzle opening speed and the nozzle closing speed and the injection amount controllability. FIG. 5A shows the nozzle opening speed> the nozzle closing speed, and FIG. 5B shows the nozzle opening. This is the case where the speed is less than the nozzle closing speed, and in order to make the rectangular injection level the same, the nozzle opening speed + the nozzle closing speed = constant. 5A and 5B, when the injection end instruction timing varies between B1 and B2 due to variations in drive pulse end timing (including noise effects), piezo contraction variations, etc., the injection end timing is C1 to C1. Vary between C2. At this time, as shown in FIG. 5B, when the nozzle opening speed is slower and the nozzle closing speed is faster, the injection end timing variation (injection amount variation) becomes smaller, and the injection amount controllability is improved. Recognize.

  FIG. 6 shows another example of the configuration of the hydraulic transmission device 61 of the piezo drive unit 101 according to the second 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. 6, in this embodiment, a first piston 62 having a cylindrical shape with a closed upper end is slidably provided in a cylindrical cylinder 15, and a second piston 64 having a smaller diameter is provided in the cylinder. Provide slidable. In a space surrounded by the first piston 62 and the second piston 64, an oil tight chamber 63 filled with hydraulic oil is formed. The first piston 62 is urged upward by a piezo spring 65 disposed below the first piston 62, and the sliding pin member 3 comes into contact with the lower end surface of the second piston 64 projecting downward from the cylinder of the first piston 62. ing. A check valve 67 is provided on the upper wall of the first piston 62 so as to communicate the oil-tight chamber 63 and the low-pressure portion. When the pressure in the oil-tight chamber 63 decreases due to leakage, the fuel flows from the low-pressure portion by pushing down the ball valve, and the oil-tight chamber 63 can be replenished.

  Also according to this embodiment, the same effects as those of the above embodiments can be obtained. Further, in the present embodiment, since the second piston 64 is accommodated in the first piston 62, the axial length of the hydraulic transmission device 61 is shortened. Therefore, the whole injector becomes compact.

  7 and 8 show a third embodiment of the present invention, and show another configuration example of the control valve unit 102. 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 FIGS. 7 and 8, in this embodiment, the valve body 2 has a bowl shape composed of a substantially hemispherical upper half and a columnar lower half having a smaller outer diameter. The sliding pin member 3 is a cylindrical pin having the same overall length, and the end portion of the sliding hole 31 where the tip portion is located is used as an enlarged portion 3a having a diameter larger than the sliding diameter, and a throttle portion 32 is opened here. ing. The valve spring 24 is disposed in the valve chamber 21 and is supported between the bottom surface of the valve spring 24 and the lower surface of the upper half of the valve body 2 protruding in a flange shape.

  In the configuration of the present embodiment, the valve spring 24 is not disposed in the passage upstream of the high-pressure side seat 23, so the high-pressure side seat diameter can be reduced. In this way, the driving force required for closing the high-pressure side seat 23 can be reduced, and, as in the above-described embodiment, by making the sliding diameter ≦ the high-pressure side seat diameter, the valve closing load of the high-pressure side seat 23 can be further increased. It can be reduced to improve energy efficiency. In the present embodiment, the high-pressure side sheet diameter ≦ the low-pressure side sheet diameter.

  In the above embodiment, the high-pressure side seat diameter is increased in order to increase the nozzle closing speed. However, the present invention is not limited to this, and by setting the high-pressure side seat diameter ≦ the low-pressure side seat diameter as in this embodiment. The output characteristics of the piezoelectric actuator 6 having a large generated force on the low-pressure side sheet 22 side can be effectively used.

  Further, as shown in FIG. 7, in this embodiment, the communication path 41 between the control chamber 4 and the valve chamber 21 is set as a throttle having a smaller opening area than the low-pressure side seat 22. Thereby, the fluctuation | variation of the pressure of the control chamber 4 can be suppressed, and the vibration at the time of nozzle needle valve opening can be suppressed.

  When the piezo actuator 6 is used as an actuator as in the above embodiment, since the displacement is very small, the hydraulic transmission device 61 in which the large-diameter first piston 62 and the small-diameter second piston 64 are combined is used. You can also. In this case, the displacement can be enlarged and transmitted, so that the power can be transmitted more efficiently.

  Any actuator may be used as long as it is an element that generates a displacement by energization. In addition to the piezoelectric element used in each of the above embodiments, a magnetostrictive element or the like can also be used.

It is sectional drawing which shows the whole structure of the injector which shows the 1st Embodiment of this invention. It is a figure for demonstrating the action | operation of the control valve in 1st Embodiment, (a) is a figure which shows the state which the low-pressure side seat is opening, (b) is the state where the high-pressure side seat is closed FIG. It is a principal part expanded sectional view of the injector which shows the other example of a sliding pin member shape. It is a figure which shows the relationship between the control chamber pressure ratio at the time of nozzle opening, a low-pressure side seat opening load, and a high-pressure side seat closing load. It is a figure which shows the relationship between the injection characteristic of an injector, and on-off valve speed, (a) is a figure which shows the case where valve opening speed> valve closing speed, (b) is a figure which shows the case where valve closing speed> valve opening speed. . It is sectional drawing which shows the whole structure of the injector which shows the 2nd Embodiment of this invention. It is sectional drawing which shows the whole structure of the injector which shows the 3rd Embodiment of this invention. It is a principal part expanded sectional view of FIG.

H1 to H4 Housing member H5 Retainer 1 Injector 11 Fuel introduction port 12 High pressure passage 13 Low pressure passage 14 Fuel outlet port 101 Nozzle part 102 Control valve part 103 Drive part 2 Valve body 21 Valve chamber 22 Low pressure side seat 23 High pressure side seat 24 Valve spring 25 passage 3 sliding pin member 3a pin-shaped tip 31 sliding hole 32 throttling portion 33, 34 passage 4 control chamber 41 communication passage 42 cylindrical member 5 nozzle needle 51 flange 52 oil reservoir chamber 53 sack portion 54 nozzle hole 55 nozzle Seat 6 Piezo actuator (actuator)
61 Hydraulic transmission device 62 First piston 63 Oil tight chamber 64 Second piston 65 Piezo spring 66 Valve spring

Claims (12)

An injector for injecting fuel supplied from a common rail through a high-pressure passage, and a control chamber that applies pressure in a valve closing direction to the nozzle needle;
A common communication passage for allowing the fuel in the high-pressure passage to flow into the control chamber and for letting out the fuel in the control chamber from the control chamber;
A control valve of three-way valve structure to increase or decrease the pressure in the control chamber by switching the communication and interruption between the communication passage and said high-pressure passage and the low pressure passage,
A drive unit for driving the valve body of the control valve and selectively seating on the low pressure side seat communicating with the low pressure passage or the high pressure side seat communicating with the high pressure passage;
The drive unit is in contact with the actuator that generates displacement when energized, and the valve body of the control valve whose pin-shaped tip is housed in the valve chamber, and slides in the sliding hole as the actuator is displaced. It has a sliding pin member that transmits driving force,
Between the sliding portion of the sliding pin member and the low-pressure side sheet, a space formed around the pin-shaped tip portion is connected to the low-pressure passage through the throttle portion, and
The relationship between the sliding diameter of the sliding portion and the sheet diameter of the high-pressure side sheet is set as sliding diameter ≦ high-pressure side sheet diameter,
The relationship between the sliding diameter of the sliding portion and the sheet diameter of the low-pressure side sheet is set as sliding diameter ≦ low-pressure side sheet diameter,
A common rail injector configured to cause the pressure of the control chamber communicating with the valve chamber to act on the valve body as an assisting force in a direction of closing the high-pressure side seat .   2. The common rail according to claim 1, wherein the pressure in the control chamber communicating with the valve chamber is acted as an assisting force so that the high-pressure side seat closing load is equal to or less than the low-pressure side seat opening load. For injectors.   3. The common rail injector according to claim 1, wherein the actuator is a piezo actuator.   The common rail injector according to any one of claims 1 to 3, wherein the pressure in the control chamber at which the nozzle needle can be opened is 50% or more of the supply fuel pressure at the maximum pressure at which the load is maximum.   The common rail injector according to any one of claims 1 to 4, wherein the sliding pin member and the valve body are separate bodies.   The common rail injector according to any one of claims 1 to 5, wherein both ends of the sliding pin member are formed in a pin shape having a diameter smaller than a sliding diameter.   The sliding pin member is formed of a cylindrical pin having a constant diameter, and an enlarged portion larger in diameter than the sliding diameter is formed at the end of the sliding hole following the low-pressure side sheet, and the tip of the sliding pin member The common rail injector according to any one of claims 1 to 6, wherein the throttle portion is formed so as to be disposed at the enlarged diameter portion.   The common rail injector according to any one of claims 1 to 7, wherein the valve body is substantially hemispherical, and a contact surface with the sliding pin member is processed into a spherical surface larger than a curvature of the spherical body.   9. The common rail injector according to claim 1, wherein at least a sliding surface of the sliding pin member is made of a super hard material or ceramic.   The common rail injector according to any one of claims 1 to 9, wherein the sliding pin member is a super hard material having a Young's modulus larger than that of a metal.   The common rail injector according to any one of claims 1 to 10, wherein a valve spring for urging the valve body toward the low pressure side seat is disposed upstream of the high pressure side seat. Control chamber pressure ratio when the nozzle is opened: kpo, nozzle seat diameter on which the nozzle needle is seated: Ds, control chamber sliding diameter of the nozzle needle: Dc, nozzle set load: Fk, fuel supply pressure from the common rail The common rail injector according to any one of claims 1 to 11, wherein each part is configured so that the following formula is satisfied when Pc is set and Pc = Pcmax (maximum supply pressure).