JP6209764B2 - Fuel injection nozzle for common rail - Google Patents

Description

  The present invention relates to a common rail fuel injection nozzle applied to inject fuel into a diesel engine used in an automobile such as a hybrid automobile.

  2. Description of the Related Art Conventionally, a diesel engine fuel injection device is a common rail type fuel injection device in which a fuel injection device is accumulated at a high pressure, high pressure fuel is sent to a fuel injection nozzle, and a needle valve in the nozzle portion is opened from a valve seat to inject high pressure fuel. Injectors have been developed. The common rail type fuel injection device is used in the latest engine because it can inject fuel of 2000 bar or more in multiple stages. The biggest drawback of the fuel injection system is that it is expensive, and the cost of the injection system parts and the engine parts other than the injection system are so high that it is said to be the same. For this reason, diesel engines are said to be one of the causes that do not spread in Japan due to the road conditions with short mileage while having extremely high thermal efficiency.

  2. Description of the Related Art Conventionally, as a fuel injection device for an internal combustion engine, a device that sufficiently utilizes a responsiveness of a piezoelectric element and a leak resistance and mounting property of a solenoid type fuel injection nozzle to sufficiently secure a lift amount of a control piston is known. The fuel injection device of the internal combustion engine is connected to a needle valve by a control piston to control the sliding of the needle valve, and a return spring arranged in the fuel chamber urges the needle valve in the nozzle closing direction to change the voltage. The lift of the control piston is controlled by the piezoelectric element displaced by. The displacement of the piezoelectric element is enlarged by the lever action of the displacement magnifying mechanism and transmitted to the control piston to ensure the lift amount of the control piston and the needle valve (see, for example, Patent Document 1).

  As an injection rate control device for a fuel injection nozzle, a device that appropriately performs sub-injection and main injection to improve engine combustion and reduce nitrogen oxide emissions is known. The fuel injection nozzle is provided with a free piston press-contacted to the upper end of a spring so as to be slidable in the vertical direction, a laminated piezoelectric element in contact with the upper surface of the piston, and a voltage applied between the terminals of the piezoelectric element. The element expands and contracts in the vertical direction to change the elastic force of the spring. In the fuel injection nozzle, the controller controls the piezoelectric element based on the detection output of a sensor that detects the operating state of the engine (see, for example, Patent Document 2).

  In addition, the present applicant has previously applied for a patent by developing a unit injector capable of delicately controlling fuel injection by controlling the spring force of a spring acting on a needle valve using a driving body. The unit injector is disposed in a balance chamber provided in a nozzle holder in which a nozzle is disposed, and a force that presses the needle valve against a valve seat formed on the nozzle and a force in a direction opposite to the spring force of the spring. And a laminated piezoelectric actuator to be actuated. In the unit injector, a spring and a laminated piezoelectric actuator are arranged in series in a balance chamber formed in a spring holder (see, for example, Patent Document 3).

JP 09-217666 A JP 05-44591 A JP 2012-137019 A

  However, the conventional common rail fuel injection nozzle controls the hydraulic pressure by a piezo actuator or solenoid and lifts the needle valve to inject fuel, but this method requires a complicated hydraulic system, There was a limit to the responsiveness to operate. Further, the needle valve in the unit injector is structured to automatically move by the pressure generated by the plunger and inject fuel, so it is not suitable for finely controlling the injection state. A structure has been developed that allows the injection of the high-pressure fuel produced by the plunger with an electromagnetic solenoid so that it can be injected multiple times. However, since the needle valve is not driven directly by the actuator, fine control is provided by the common rail. In addition to being inferior to the fuel injection device, the structure as described above is added, so that the structure becomes complicated and the advantages of the common rail fuel injection device are impaired.

  By the way, in the fuel injection device, a piezo element, that is, a piezoelectric element is used as an auxiliary means for operating the needle valve. However, as in the background art described above, all of the piezoelectric elements are arranged in the head portion of the fuel injection nozzle. It was not satisfactory as an actuator that counteracts the spring force of the spring that pushes down the needle valve with this command.

  An object of the present invention is to solve the above-described problem. The spring force of a pressing spring pressing the needle valve via a push rod, that is, the closing force of the needle valve is directly applied to an actuator such as a piezo actuator. It is a structure that directly releases the spring force and opens the nozzle hole by the needle valve by a simple operation, and is very simple and secures high responsiveness to the operation of the needle valve, and the injection during one cycle of the engine To provide a fuel injection nozzle for common rails that can be used more frequently than conventional ones, reduce the emission of harmful substances in exhaust gas accurately by burning fuel, and contribute to improving engine performance It is.

The present invention provides a nozzle body formed with a nozzle hole at a tip, a fuel reservoir for supplying fuel to the nozzle, and a fuel passage for supplying the fuel to the fuel reservoir, and disposed in the nozzle body. A needle valve that lifts in response to the fuel pressure of the fuel to open the nozzle hole, and the nozzle hole is closed via the needle valve by the spring force of a pressure spring disposed in a chamber in the nozzle body. In a common rail fuel injection nozzle comprising a push rod that pushes in a direction,
One end is supported and disposed in the nozzle body, and the other end is disposed to face the end of the push rod. The actuator has the one end disposed on the nozzle body. A fuel pressure piston constituted by fuel supported by a piston pedestal or supported by an actuator pedestal disposed on the piston pedestal and supplied to a gap between the actuator pedestal and the piston pedestal, and a predetermined pressure for the fuel pressure piston A non-return valve provided in a low-pressure fuel passage formed in the nozzle body in order to maintain the predetermined fuel pressure, and the non-return valve responds to the operation of the actuator. The low pressure fuel passage for supplying the fuel to the piston is closed to maintain the fuel pressure of the fuel pressure piston; The fuel pressure piston has a pressure receiving area for generating a predetermined force, and the fuel pressure maintained in the fuel pressure piston is the fuel pressure by the high pressure fuel acting on the needle valve. Is set to a smaller value,
The actuator is actuated in response to a command from a controller to lift the push rod, and the needle valve is freed by lift of the push rod and lifted by fuel pressure to open the nozzle hole, The fuel injection nozzle for a common rail is characterized by injecting the fuel from the fuel passage and the fuel reservoir through the injection hole.

  In the fuel injection nozzle for common rail, the actuator is formed in a cylindrical body with a central hole through which the push rod is inserted, one end is supported and disposed on the nozzle body, and the other end is the central part of the cylindrical body. The push rod is opposed to the flange portion formed at the end portion of the push rod inserted through the hole, and the push rod resists the spring force of the pressing spring through the flange portion by the operation of the actuator. Is to lift.

  Alternatively, in the common rail fuel injection nozzle, the push rod includes an end plate portion that receives the spring force of the pressing spring at one end, and a rod portion that faces the needle valve at the other end, and the actuator Is formed in a solid structure, and is housed in a cylindrical portion of the push rod formed between the end plate portion of the push rod and the rod portion, and the actuator has one end at the nozzle body. And the other end is disposed opposite to the end face plate of the push rod, and the push rod resists the spring force of the pressing spring through the end face plate by the operation of the actuator. Thus, the push rod is lifted.

Further, the common rail fuel injection nozzle of this is to reduce adjusting the gap between the flange portion of the other end and the push rod of the one end and the gap between the piston pedestal and / or the actuator of the actuator, A shim is interposed in the gap.

  In the common rail fuel injection nozzle, the fuel supplied to the fuel pressure piston is supplied from a fuel tank through a low pressure fuel passage formed in the nozzle body by a fuel pump.

  Further, in this common rail fuel injection nozzle, the force that causes the needle valve to act in the closing direction of the nozzle hole is the fuel pressure accumulated by pressurizing the fuel from the fuel tank in addition to the spring force of the pressing spring. It depends on the fuel pressure supplied from the chamber. The pressing spring has one end supported by the nozzle body and the other end supported directly by the push rod or by a pressing piston interposed between the push rod and the pressing spring.

  The actuator is a piezo actuator formed by stacking piezo elements, and the piezo actuator is applied in response to a command from the controller and is operated in accordance with an applied voltage to the piezo actuator. The needle valve is lifted by extending the push rod by extending to a predetermined length.

  The fuel supplied to the fuel reservoir through the fuel passage is supplied from a fuel accumulator chamber that accumulates pressurized fuel from a fuel pressurizing high-pressure pump that pressurizes fuel in a fuel tank. The fuel overflowed from the gap between the nozzle body and the nozzle body is returned to the fuel tank through the balance chamber and the overflow fuel passage formed in the nozzle body.

  Since this common rail fuel injection nozzle is configured as described above, the pressing spring is contracted by the extension of the actuator, particularly the piezoelectric actuator, and the spring force of the pressing spring is canceled by the extension of the piezoelectric actuator, and the spring force is reduced. When released, the needle valve can be lifted to open the nozzle hole. That is, a valve opening force acts on the needle valve in the direction of opening the nozzle hole due to the fuel pressure of the high-pressure fuel supplied to the fuel reservoir. The opening force of the needle valve is a force obtained by multiplying the area obtained by subtracting the cross-sectional area of the needle valve seat from the cross-sectional area of the needle valve sliding portion by the fuel pressure. On the other hand, the needle valve is pressed against the needle valve in the closing direction by the spring force of the pressing spring. Therefore, when this common rail fuel injection nozzle releases the force holding the needle valve by the extension of the piezo actuator consisting of a stack of piezo elements, the needle valve moves in the opening direction by the fuel pressure due to the fuel pressure. Can be made. In addition, for example, when a DC voltage of 150 V is applied to the piezo actuator, the total length of the piezo laminate is 10 mm, and the amount of elongation is 10 μm to 15 μm with respect to the actuator pedestal. When the total length is 30 mm, it becomes 30 μm to 45 μm when 150 V is applied, and the elongation of the piezoelectric laminate is almost proportional to the voltage. That is, the piezo actuator is operated in response to a command from the controller, with the applied voltage being controlled, and is extended to a predetermined length that is predetermined according to the applied voltage to the piezo actuator to lift the push rod and the needle. Lift the valve and open the nozzle hole. The piezo actuator is placed between the flange of the push rod and the pedestal piston or the nozzle body, but there is no gap between the flange of the push rod and the end of the piezo actuator. Since this is a value obtained by accumulating tolerances, that is, variations of many nozzle parts, the piezo actuator needs to set the gap short in consideration of the variations.

  By the way, even when the length of the gap due to component variation is measured during assembly of the fuel injection nozzle for the common rail, and the gap is adjusted with a shim or the like corresponding to the gap, it is difficult to adjust with a gap of about 5 μm. Furthermore, considering the familiarity of the seat part of the needle valve and the linear expansion of each component, a clearance of 10 μm to 15 μm is necessary for the gap. Therefore, by arranging an actuator base in the gap and always setting the gap to zero, the elongation of the piezo actuator can be effectively used to lift the needle valve. Further, by increasing the pressure receiving area for the piezo actuator (including a check valve), it is possible to minimize the length that the fuel is compressed and the pedestal is lowered even when the force of the piezo actuator is applied. If the pressure applied to the pressure receiving portion of the actuator pedestal is too large, the pedestal surface rises by that pressure and the nozzle needle valve opens, so that the fuel pressure is preferably such that the fuel is fed from the fuel tank by the high pressure pump. In this case, the length of the pedestal is about 3 to 5 μm. Furthermore, by using a piston to press the needle valve in the valve closing direction, when the fuel pressure is high, the pressing force is automatically increased and the sealing performance can be secured. If only the spring force of the pressure spring is used, it will be undesirably large because it will overcome the valve opening force at high pressure, but the present invention does not allow the operation of the piezo actuator, ie, the amount of extension, to act directly on the push rod. As the push rod is released from the needle valve, the response is extremely good. If the piezo actuator is formed in a cylindrical shape through which the push rod is inserted, the structure itself is simplified, but the manufacturing cost of the piezo actuator is increased. Alternatively, if the push rod is formed in a cylindrical shape through which the piezo actuator is inserted, the shape of the push rod will be complicated, but the piezo actuator can be configured in a solid shape, and the machining of the piezo actuator is easy and contributes to cost reduction. it can.

It is a circuit diagram which shows the outline of the fuel-injection apparatus incorporating the fuel-injection nozzle for common rails by this invention. It is sectional drawing which shows 1st Example of the fuel injection nozzle for common rails by this invention. It is an expanded sectional view of the principal part of the fuel injection nozzle for common rails of FIG. It is sectional drawing which shows 2nd Example of the fuel injection nozzle for common rails by this invention. It is sectional drawing which shows 3rd Example of the fuel injection nozzle for common rails by this invention. It is sectional drawing which shows 4th Example of the fuel injection nozzle for common rails by this invention. It is an expanded sectional view which shows the area | region where the push rod and piezoelectric actuator in the fuel injection nozzle for common rails of FIG. 6 are located. It is sectional drawing which shows the AA cross section of FIG. 7 in the fuel injection nozzle for common rails of FIG. It is a top view which shows the actuator base in the fuel injection nozzle for common rails of FIG. It is a front view which shows the actuator base of FIG. It is explanatory drawing which shows the piezoelectric actuator integrated in the fuel injection nozzle for common rails shown in FIG.2, FIG.4, and FIG.5. It is explanatory drawing which shows the piezoelectric actuator integrated in the fuel injection nozzle for common rails shown in FIG.

  Hereinafter, an embodiment of the fuel injection nozzle for common rail will be described with reference to the drawings. First, an embodiment of the common rail fuel injection nozzle will be described with reference to FIGS. The common rail fuel injection nozzle 50 is preferably applied to, for example, a hybrid vehicle equipped with a diesel engine. The common rail fuel injection nozzle is fixed to an engine body or the like by a screw 51 provided in the nozzle body 1. In the common rail fuel injection nozzle 50, high-pressure fuel from the high-pressure fuel pipe 27 is supplied to the fuel reservoir 33, the needle valve 2 is raised by the high-pressure fuel pressure, the nozzle hole 17 is opened, and the fuel is in the combustion chamber, that is, the engine. The fuel is injected along the fuel injection locus 18. The nozzle body 1 constituting the common rail fuel injection nozzle 50 is located between a nozzle body 1B incorporating a needle valve 2, an upper portion 1U having a high-pressure fuel inlet 9 and an overflow fuel outlet, and between the nozzle body 1B and the upper portion 1U. The intermediate portion 1 </ b> M, the support portion 1 </ b> S that supports the pressing piston 6 interposed between the pressing spring 7 and the push rod 5, and the nozzle case 1 </ b> C that accommodates these and includes the screw portion 51. In the nozzle case 1C, an upper portion 1U, a support portion 1S, an intermediate portion 1M, and a nozzle body 1B constituting the nozzle body 1 are accommodated and fixed. The high-pressure fuel passage 8 is formed in communication with the upper part 1U, the support part 1S, the intermediate part 1M, and the nozzle body 1B. The nozzle case 1C is provided with a threaded portion 51 on the outer peripheral surface for attaching the common rail fuel injection nozzle 50 to an engine cylinder head or the like.

  A spring accommodating chamber 42S formed by a recess in the upper portion 1U of the nozzle body 1 accommodates a pressing spring 7 that pushes the push rod 5 in the valve closing direction, and a balance chamber 42 penetrating the intermediate portion 1M includes A piezo actuator 3 that is a laminated body of piezo elements provided with a central hole 3H that is disposed around the push rod 5 and the push rod 5, that is, the push rod 5 is disposed. As shown in FIG. 11, the piezo actuator 3 is formed with a through hole 86 through which the push rod 5 is inserted. In the common rail fuel injection nozzle 50, a piston pedestal 16 is interposed between the nozzle body 1 </ b> B and the intermediate portion 1 </ b> M, and a shoulder portion 15 </ b> S of the actuator pedestal 15 is provided on the piston pedestal 16. 43 is supported by a fuel pressure piston 39P formed by a gap 39, and is seated with a gap 40 formed between the upper end surface 47 of the needle valve 2. The actuator pedestal 15 is opposed to an end portion 36 of the piezo actuator 3 which is an actuator via a gap 34C. The piston pedestal 16 is formed with a recess 44 communicating with the low-pressure fuel passage 10, and the check valve 14 including the ball 31 and the spring 32 is disposed in the recess 44. The end portion of the low-pressure fuel passage 10 formed in the intermediate portion 1M is formed in a seat portion where a ball 31 constituting the check valve 14 is pressed against a spring 32 and seated. The needle valve 2 is disposed so as to form a fuel passage 49 around a hollow hole formed in the nozzle body 1B, and is seated on a valve seat 41 formed in the nozzle body 1B. The needle valve 2 includes a large-diameter portion 2L serving as a needle-valve sliding portion 46 accommodated in the nozzle body 1, a small-diameter portion 2S that forms a fuel passage 49 around the tip, and a tip side located in the conical hole 54 of the nozzle body 1. The boundary between the large-diameter portion 2L and the small-diameter portion 2S is located in the fuel reservoir 33 of the nozzle body 1B and is formed in the step portion 45. The high-pressure fuel 30H passes from the high-pressure fuel inlet 9 formed in the upper portion 1U, around the needle valve between the high-pressure fuel passage 8, the fuel reservoir 33 formed in the nozzle body 1B, and the needle valve 2 and the nozzle body 1. It is supplied to the formed fuel passage 49. In the fuel injection nozzle 50 for the common rail, when the push-down force of the push rod 5 to the needle valve 2 becomes free, the high-pressure fuel 30H of the fuel reservoir 33 mainly acts on the step 45 of the needle valve 2 and moves the needle valve 2 up and down. Will be moved. When the needle valve 2 moves up and down, the needle valve 2 comes into contact with the valve seat 41 on which the needle valve 2 is seated, and the needle valve 2 opens and closes the nozzle hole 17 formed in the nozzle body 1B. The fuel is injected from the nozzle hole 17 that is open.

  As shown in FIG. 1, the high-pressure fuel 30 </ b> H supplied to the common rail fuel injection nozzle 50 is supplied from the fuel 30 contained in the fuel tank 20 to the fuel pressurizing high-pressure pump 22 through the pressurizing fuel adjustment valve 21. The fuel 30 is pressurized and pressurized to a high pressure. The high-pressure fuel 30 </ b> H that has been increased in pressure by the high-pressure pump 22 is accumulated in the fuel accumulation chamber 23, and is sent from the fuel accumulation chamber 23 to the high-pressure fuel passage 8 of the common rail fuel injection nozzle 50 through the high-pressure fuel pipe 27. The controller 24 is configured to control the flow rate of fuel fed into the combustion chamber, that is, the engine, in accordance with vehicle speed and engine state detection information. The fuel leaked into the balance chamber 42 in the common rail fuel injection nozzle 50 is returned to the fuel tank 20 from the overflow fuel outlet 13 through the overflow fuel return pipe 29 through the overflow fuel passage 12. Further, since the fuel pressure piston 39P constituting the pressing piston is formed in the gap 39 between the actuator base 15 and the piston base 16, the low pressure fuel passage 10 for supplying low pressure fuel to the gap 39 can be formed. The low pressure fuel passage 10 is configured such that the fuel 30 in the fuel tank 20 is supplied from the low pressure fuel inlet 11 through the low pressure fuel pipe 28. For the low pressure fuel in the nozzle body 1, the check valve 14 is provided on the piston base 16 that forms the low pressure fuel passage 10 in order to configure the fuel pressure piston 39 </ b> P with low pressure fuel. The controller 24 adjusts the fuel pressure in the fuel pressure accumulating chamber 23 and controls the application of voltage to a piezo actuator 3 (described later) provided in the common rail fuel injection nozzle 50 so that the operation of the piezo actuator 3 is controlled by the engine cycle. Control in response to

The common rail fuel injection nozzle 50 is generally formed with a nozzle hole 17 at the tip, a fuel reservoir 33 at an intermediate portion communicating with the nozzle hole 17, and a fuel passage 8 for supplying high-pressure fuel 30H to the fuel reservoir 33. Nozzle body 1, needle valve 2 that lifts in response to the fuel pressure of high-pressure fuel 30H to open nozzle hole 17 and inject high-pressure fuel 30H from nozzle hole 17, and a pressure spring disposed in nozzle body 1 7 is provided with a push rod 5 that presses the needle valve 2 in the nozzle hole closing direction with a spring force of 7. In particular, the needle valve 2 is inserted into the nozzle body 1B so as to move up and down in the nozzle body 1B, and when released from the push-down force by the push rod 5, it is raised by the fuel pressure and provided in the nozzle body 1B. The injection hole 17 is opened, and high-pressure fuel 30H is injected from the injection hole 17. The nozzle body 1B has an upper large-diameter hole 52, a lower small-diameter hole 53, a fuel reservoir 33 between the large-diameter hole 52 and the small-diameter hole 53, a conical hole 54 on the tip side where the valve seat 41 is formed, And the nozzle hole 17 formed in the site | part of the conical hole 54 is formed. The needle valve 2 includes a large diameter portion 2L that slides within the large diameter hole 52 of the nozzle body 1B, a small diameter portion 2S that moves up and down within the small diameter hole 53 of the nozzle body 1B, and a space between the large diameter portion 2L and the small diameter portion 2S. And a conical valve portion 2 </ b> V seated on a valve seat 41 formed in the conical hole 54 by moving up and down in the conical hole 54 of the nozzle body 1 </ b> B. The push rod 5 is disposed in the balance chamber 42 of the intermediate portion 1M of the nozzle body 1, and the distal end of the push rod 5 has a hollow hole in the actuator pedestal 15 that is a pedestal piston disposed in the lower portion of the balance chamber 42. The needle valve 2 extends through the needle valve 2. A front end surface 48 of the push rod 5 pressed down by the spring force of the pressing spring 7 is in contact with an upper end surface 47 constituting an upper contact surface of the needle valve 2. Accordingly, the needle valve 2 becomes free when the push rod 5 is released by the spring force of the pressing spring 7, and only the fuel pressure acts. The fuel pressure urged by the needle valve 2, that is, the valve opening force of the needle valve 2 is such that the diameter of the large-diameter hole 52 of the nozzle body 1B is D1, and the cone of the nozzle body 1B on which the conical valve portion 2V of the needle valve 2 is seated. If the diameter of the valve seat 41 formed in the hole 54 is D2, the cross-sectional area [π (D1 / 2) ² ] of the large-diameter hole 52 of the nozzle body 1B, which is the sliding portion of the needle valve 2, determines the needle valve 2 The fuel pressure is applied to the area [π (D1 / 2) ² −π (D2 / 2) ² ]] obtained by subtracting the cross-sectional area [π (D2 / 2) ² ] of the valve seat 41 of the conical valve portion 2V or the nozzle body 1B. It is the power of the multiplied value. On the other hand, the spring force of the pressing spring 7 acts on the needle valve 2 to press the needle valve 2 in the valve closing direction.

  Specifically, as shown in FIGS. 2 and 3, the common rail fuel injection nozzle has one end 36 supported and disposed on the nozzle body 1 around the push rod 5 in the nozzle body 1. The piezo actuator 3 constituting the actuator is disposed so that the end portion 37 faces the flange portion 35 formed at the end portion of the push rod 5. Specifically, a flange portion 35 is integrally formed on the end portion 37 of the push rod 5. The piezoelectric actuator 3 is supported by an actuator base 15 seated on a piston base 16 interposed between a nozzle body 1B constituting the nozzle body 1 and an intermediate part 1M via a gap 34C, and the other end is a flange part 35. Are arranged with a predetermined gap, preferably zero gap. Information on the pressure signal of the fuel pressure accumulation chamber 23 is sent to the controller 24 through the line 25, and information 90 from the engine, the vehicle device and the like is input. Therefore, when a voltage is applied to the electrodes 4 (+ and −) of the piezo actuator 3 through the wiring 26 in response to a command from the controller 24, the piezo actuator 3 generates an elongation corresponding to the applied voltage, and the piezo actuator 3 corresponds to the elongation. A force is generated to lift the push rod 5 in the valve opening direction, the needle valve 2 is freed by the lift of the push rod 5, the needle valve 2 is lifted by the fuel pressure, the nozzle hole 17 is opened, and the fuel is injected. Injected along the track 18. In the present invention, a piezoelectric actuator 3 formed by stacking piezoelectric elements is used as the actuator. Further, when the common rail fuel injection nozzle 50 is energized from the power source to the positive and negative electrodes 4 of the piezo actuator 3 in response to a command from the controller 24 and the piezo actuator 3 generates expansion, the common rail fuel injection nozzle 50 is pushed in response to the expansion of the piezo actuator 3. When the rod 5 is lifted, the pressing spring 7 contracts, and when the push rod 5 is lifted, the spring force of the pressing spring 7 is released from the needle valve 2, the needle valve 2 is lifted by fuel pressure, and the needle valve 2 is ejected from the injection hole 7. The high-pressure fuel 30H is injected from the injection hole 7 into the combustion chamber (not shown). Therefore, when the spring force of the pressure spring 7 acting on the push rod 5 that pushes down the needle valve 2 is released by the extension of the piezoelectric actuator 3, the common rail fuel injection nozzle 50 loses the force to push down the needle valve 2. 2 lifts with fuel pressure.

  The end portion 36 of the piezo actuator 3 is supported by an actuator base 15 that forms a seating surface, and the end portion 37 of the piezo actuator 3 faces the flange portion 35 of the push rod 5 with a gap 38 therebetween. . Since the clearance 38 is close to the clearance zero to improve the response of the piezo actuator 3, the check valve 14 is activated when the piezo actuator 3 is urged into the clearance 39 between the actuator base 15 and the piston base 16. The low pressure fuel passage 10 is closed to form a fuel pressure piston 39P. That is, the common rail fuel injection nozzle 50 is supported by the shoulder of the actuator base 15 being disposed on the step 43 of the piston base 16, and the shoulder of the actuator base 15 and the step 43 of the piston base 16. A gap 39 is formed between them. Low-pressure fuel is supplied to the gap 39 through the check valve 14 formed in the piston base 16 and the low-pressure fuel passage 10, whereby the gap 39 is configured as a fuel pressure piston 39P. Low pressure fuel is supplied to the clearance 39 from the low pressure fuel passage 10, which is a fuel passage formed in the nozzle body 1, to the check valve 14 formed in the piston base 16. In the fuel pressure piston 39P, when the piezo actuator 3 is energized, the end 36 of the piezo actuator 3 pushes down the actuator base 15, the fuel 30 existing in the gap 39 is pressurized, and the ball 31 is formed in the intermediate portion 1M. The low-pressure fuel passage 10 is configured to be seated on the valve seat at the end of the low-pressure fuel passage 10 and closed. The check valve 14 acts to close the fuel passage 10 of the fuel pressure piston 39P in response to the operation of the piezo actuator 3. The actuator pedestal 15 has a pressure receiving area for generating a predetermined force on the fuel pressure piston 39P, and the fuel pressure supplied to the fuel pressure piston 39P is a fuel generated by the high pressure fuel 30H acting on the needle valve 2. It is set to a value smaller than the pressure. The fuel pressure by the fuel of the fuel pressure piston 39P is the supply pressure of the fuel supplied from the fuel tank 20.

  In the common rail fuel injection nozzle 50, the force that causes the needle valve 2 to act in the closing direction of the nozzle hole 17 is supplied from the spring force of the pressing spring 7 and the fuel pressure accumulation chamber 23 that pressurizes and accumulates fuel from the fuel tank 20. And the fuel pressure of the high pressure fuel 30H. The pressing spring 7 has one end supported by the nozzle body 1 and the other end supported by the push rod 5 and a pressing piston 6 interposed between the push rod 5 and the pressing spring 7. In the common rail fuel injection nozzle 50, the high-pressure fuel 30 </ b> H supplied to the fuel reservoir 33 is supplied from the fuel pressure accumulation chamber 23 that accumulates the pressurized fuel from the fuel pressurizing high-pressure pump 22 that pressurizes the fuel in the fuel tank 20. ing. Further, the fuel that overflows from the gap between the needle valve 2 and the nozzle body 1 from the fuel reservoir 33 is returned to the overflow fuel outlet 13 or the fuel tank 20 through the overflow fuel passage 12 formed in the nozzle body 1. The low pressure fuel set to a fuel pressure lower than the high pressure fuel 30H supplied to the fuel pressure piston 39P is supplied from the fuel tank 20 through the low pressure fuel passage 10 formed in the nozzle body 1 by the fuel pump 19.

  Next, a second embodiment of the common rail fuel injection nozzle will be described with reference to FIG. The common rail fuel injection nozzle of the second embodiment is obtained by eliminating the pressing piston from the first embodiment shown in FIG. Compared with the first embodiment, the nozzle body 1 has no support portion 1S, and an upper portion 1U and an intermediate portion 1M are integrally formed. The common rail fuel injection nozzle 50 does not have the pressing piston 6 of the first embodiment between the push rod 5 and the pressing spring 7, and the pressing spring 7 directly contacts the upper surface of the flange portion 35 of the push rod 5. The spring force 7 is directly urged to the push rod 5. Accordingly, the balance chamber 42 formed in the nozzle body 1 is formed in a straight hollow, and the pressing spring 7 is disposed in the spring accommodating chamber 42S, and the push rod 5 and the piezoelectric actuator 3 are disposed in the balance chamber 42. ing. The second embodiment is. Since the operation itself is the same as in the first embodiment, the same reference numerals are given to the same members, and duplicate descriptions are omitted.

Next, a third embodiment of the common rail fuel injection nozzle will be described with reference to FIG. The common rail fuel injection nozzle of the third embodiment has a simple configuration in which the actuator base, which is an actuator base, is eliminated from the second embodiment shown in FIG. 4, and the low-pressure fuel passage 10 and the check valve 14 are accordingly eliminated. Is. The common rail fuel injection nozzle 50 according to the third embodiment has a structure in which the check valve 14 is not provided in the fuel pressure piston 39P and the low pressure fuel passage 10 as compared with the first embodiment. The end surface of the portion 36 is supported by the actuator pedestal 15P via a shim 34, and the end 37 at the other end faces the flange portion 35 of the push rod 5 via the shim 34 so as to eliminate a gap. Has no function of the fuel pressure piston as in the first embodiment and the second embodiment, and a gap generated between the members, for example, a gap 38 between the piezo actuator 3 and the flange portion 35 and between the piezo actuator 3 and the actuator base 15P. Since the gaps and the like are adjusted by the shims 34, it is necessary to manufacture various members with high precision, so that the gaps become zero by the shims 34. There needs to be an integer. The third embodiment is. Compared with the first embodiment and the second embodiment, the operation itself is the same, and thus the same members are denoted by the same reference numerals, and redundant description is omitted.

Next, a fourth embodiment of the common rail fuel injection nozzle will be described with reference to FIG. Compared with the first to third embodiments, the fourth embodiment includes a piezo actuator as an actuator, and a push rod that lifts by operation of the piezo actuator, that is, in response to an instruction from the controller. Is the same technical idea. In the first to third embodiments, the piezo actuator 3 is formed in a cylindrical body with a central hole 3H through which the push rod is inserted, and is formed at the end of the push rod 5 through which the piezo actuator 3 is inserted. Opposing the portion 35, the push rod 5 lifts the push rod 3 against the spring force of the pressing spring 7 through the flange portion 35 by the operation of the actuator 3. In contrast, in the fourth embodiment, the piezo actuator 3A is formed in a solid structure, the push rod 5A is formed in a cylindrical shape with a hollow hole 5H, and the piezo actuator 3A is placed in the hollow hole 5H of the cylindrical portion 5D. It is inserted and accommodated. That is, the push rod 5A is provided with an end face plate portion 5C that receives the spring force of the pressing spring 7 at one end and a rod portion 5B that faces the needle valve 2 at the other end. The piezoelectric actuator 3A is housed in a cylinder portion 5D of a push rod 5A formed between the end surface plate portion 5C and the rod portion 5B, and the piezoelectric actuator 3A is supported and arranged on an actuator base 15A whose one end surface 3L is supported by the nozzle body 1. And the other end surface 3U is disposed in contact with the end plate portion 5C of the push rod 5A so that the push rod 5A is actuated by the spring force of the pressing spring 7 via the end plate portion 55C by the operation of the piezoelectric actuator 3A. The push rod 5A is lifted against this.

In the fourth embodiment, the piezo actuator 3A has a solid structure such as a round shape, a quadrangular shape, an oval shape, etc., as shown in FIG. 12, and can reduce the manufacturing cost. As for the push rod 5A, a pair of crescent-shaped holes 85 are formed around the rod portion 5B that is integrated with the end of the cylindrical portion 5D on the needle valve 2 side. The lower end surface 5L of the rod portion 5B forms a pressing surface that closes the needle valve 2 by pressing the upper end surface of the needle valve 2 when the push rod 5 is not lifted. The upper end surface 5U of the rod portion 5B forms a gap 38A and faces the lower end surface 3L of the piezo actuator 3A, and contacts the lower end surface 3L of the piezo actuator 3A when the push rod 5A is lifted. In other words, the gap 38A between the lower end surface 3L and the upper end surface 5U is set to be at least larger than or equal to the amount of elongation that extends due to the application of the piezoelectric actuator 3A. The actuator pedestal 15A has a lower end shoulder portion 15S supported by a stepped portion 43 of the piston pedestal 16 via a combustion pressure piston 39P formed by a gap 39, and an upper end portion of a pair of crescent moons of the push rod 3A. A pair of crescent-shaped convex portions 84 that are respectively inserted through the shaped holes 85 are provided. A central hole 87 through which the rod portion 5B of the push rod 5A is inserted is formed in the actuator base 15A. The piezoelectric actuator 3A has its lower end surface 3L disposed and supported by the upper end surfaces 15U of the pair of crescent-shaped convex portions 84 of the actuator base 15A, and the upper end surface 3U faces and contacts the end surface plate portion 5C of the push rod 5A. It is arranged. In the fourth embodiment, when the piezo actuator 3A is applied according to the command of the controller 24, the piezo actuator 3A expands and pushes up the end face plate portion 5C of the push rod 5A against the spring force of the pressing spring 6 to push the push rod. When 5A lifts, the lower end surface 5L of the rod portion 5B of the push rod 5A is separated from the upper end surface of the needle valve 2, and the needle valve 2 is released from the spring force of the pressing spring 6. When the needle valve 2 is released from the spring force of the pressing spring 6, the needle valve 2 is lifted by the fuel pressure, the injection hole 17 is opened, and the fuel 30 is combusted along the fuel injection path 18 from the injection hole 17. (Not shown). Here, the fourth embodiment is. Compared with the first to third embodiments, the operation itself is basically the same. Therefore, the same reference numerals are given to the same members, and the duplicate description is omitted.

  The common rail fuel injection nozzle according to the present invention is preferably applied to, for example, a diesel engine in a hybrid vehicle.

DESCRIPTION OF SYMBOLS 1 Nozzle body 2 Needle valve 3, 3A Piezo actuator 4 Electrode 5, 5A Push rod 6 Pressing piston 7 Pressing spring 8 High pressure fuel passage 10 Low pressure fuel passage 12 Overflow fuel passage 14 Check valve 15, 15A Actuator base 16 Piston base 17 Injection Hole 19 Fuel pump 20 Fuel tank 23 Fuel pressure storage chamber 24 Controller 30 Fuel 30H High pressure fuel 33 Fuel reservoir 34 Shim 35 Flange 36, 37 Ends 38, 39, 39A, 40 Clearance 39P Fuel pressure piston 42 Balance chamber 49 Fuel passage 50 Fuel injection nozzle

Claims (9)

A nozzle body formed with a nozzle hole at the tip, a fuel reservoir for supplying fuel to the nozzle hole, and a fuel passage for supplying the fuel to the fuel reservoir, and a fuel for the fuel disposed in the nozzle body A needle valve that lifts in response to pressure to open the nozzle hole, and a spring force of a pressing spring disposed in a chamber in the nozzle body presses the nozzle hole in the closing direction via the needle valve. In a common rail fuel injection nozzle comprising a push rod,
One end is supported and disposed in the nozzle body, and the other end is disposed to face the end of the push rod. The actuator has the one end disposed on the nozzle body. A fuel pressure piston constituted by fuel supported by a piston pedestal or supported by an actuator pedestal disposed on the piston pedestal and supplied to a gap between the actuator pedestal and the piston pedestal, and a predetermined pressure for the fuel pressure piston A non-return valve provided in a low-pressure fuel passage formed in the nozzle body in order to maintain the predetermined fuel pressure, and the non-return valve responds to the operation of the actuator. The low pressure fuel passage for supplying the fuel to the piston is closed to maintain the fuel pressure of the fuel pressure piston; The fuel pressure piston has a pressure receiving area for generating a predetermined force, and the fuel pressure maintained in the fuel pressure piston is the fuel pressure by the high pressure fuel acting on the needle valve. Is set to a smaller value,
The actuator is actuated in response to a command from a controller to lift the push rod, and the needle valve is freed by lift of the push rod and lifted by fuel pressure to open the nozzle hole, The fuel injection nozzle for a common rail, wherein the fuel from the fuel passage and the fuel reservoir is injected through the injection hole. The actuator is formed in a cylindrical body with a central hole through which the push rod is inserted, one end of which is supported and disposed on the nozzle body, and the other end is inserted into the central hole of the cylindrical body. facing the flange portion formed in part, claims characterized that you lifts the push rod against the spring force of the pressure spring the push rod through the flange portion by the operation of said actuator Item 2. The fuel injection nozzle for common rails according to item 1. The push rod includes an end face plate portion that receives the spring force of the pressing spring at one end, and a rod portion that faces the needle valve at the other end,
The actuator is formed in a solid structure, and is accommodated in a cylindrical portion of the push rod formed between the end face plate portion of the push rod and the rod portion,
The actuator has one end supported by the nozzle body and the other end opposed to the end plate portion of the push rod, and when the actuator is operated, the push rod moves the end plate portion . The common rail fuel injection nozzle according to claim 1, wherein the push rod is lifted against the spring force of the pressing spring. In order to adjust the clearance between the one end of the actuator and the piston pedestal and / or the clearance between the other end of the actuator and the flange portion of the push rod, a shim is interposed in the clearance. The fuel injection nozzle for a common rail according to any one of claims 1 to 3 . The fuel supplied to the fuel pressure piston according to any one of claims 1 to 4, characterized in that it is supplied through the low-pressure fuel passage formed in the nozzle body by a fuel pump from a fuel tank Fuel injection nozzle for common rail. In addition to the spring force of the pressing spring, the force that causes the needle valve to act in the closing direction of the nozzle hole is based on the fuel pressure supplied from the fuel accumulator chamber that has pressurized and accumulated fuel from the fuel tank. The fuel injection nozzle for common rails according to any one of claims 1 to 5 . The press spring is characterized in that one end is supported by the nozzle body and the other end is supported directly by the push rod or by a press piston interposed between the push rod and the press spring. The fuel injection nozzle for common rails of any one of 1-6 . The actuator is a piezo actuator formed by stacking piezo elements, and the piezo actuator is applied and operated in response to a command from the controller, and is determined in advance according to an applied voltage to the piezo actuator. common rail fuel injection nozzle according to any one of claims 1 to 7, characterized in that to lift the predetermined by lifting the push rod extending the length the needle valve that is. The fuel supplied to the fuel reservoir through the fuel passage is supplied from a fuel accumulator chamber that accumulates pressurized fuel from a fuel pressurizing high-pressure pump that pressurizes fuel in a fuel tank. The common rail according to any one of claims 1 to 8 , wherein the fuel overflowed from a gap with the nozzle body is returned to the fuel tank through the balance chamber and an overflow fuel passage formed in the nozzle body. Fuel injection nozzle.

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