JP2009114951A - Injector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain wear of a contact part and thereby prevent breakage of an piezoelectric element in an injector where an annular counter surface formed in a piezo-actuator and an annular counter surface formed in a body contact each other at a position on a storage hole side with respect to a sealing means for axially positioning the piezo-actuator. <P>SOLUTION: When a portion whereat counter surfaces 19, 413c contact each other is represented by a contact part (A). A fuel guiding path 413e is provided in the counter surfaces 19, 413c for guiding a fuel in a storage hole 17 to the contact part (A). Thereby, the contact part (A) is in a fluid lubricating state so that discharge of wear debris is promoted by the flow of the fuel guided to the contact part (A) for restraining wear of the contact part (A). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an injector that controls opening / closing operation of a nozzle by a piezo actuator.

  A conventional fuel injection device is configured to inject and supply high-pressure fuel stored in a common rail into a combustion chamber of each cylinder of an internal combustion engine via an injector. The injector includes a nozzle that opens and closes an injection hole with a needle and injects fuel when the valve is opened, and a piezo actuator that controls the opening and closing operation of the nozzle by controlling the pressure acting on the side of the needle opposite to the injection hole.

The injector shown in Patent Document 1 has a sealing means disposed on one end side of the piezo actuator, in which a housing hole for accommodating the piezo actuator and a lead wire extraction hole for taking out the lead wire are formed in the body. This prevents the fuel from flowing out from the storage hole to the lead wire extraction hole. In addition, the annular facing surface formed on the piezo actuator and the annular facing surface formed on the body abut at the position closer to the storage hole than the sealing means, thereby positioning the piezo actuator in the axial direction.
German Patent Application No. 10140529

  However, in the injector shown in Patent Document 1, the part actually in contact with each other, that is, the contact part, is deformed slightly by the reaction force when the piezo actuator is driven, and wear of the contact part occurs. To do. At that time, since the contact portion is in a line contact state in an annular shape, the fuel flow is interrupted, and wear powder is not discharged from the contact portion, thereby promoting wear. When wear progresses, the deflection of the spring that preloads the piezo stack decreases, which reduces the preload, and in the worst case, tensile stress is generated in the piezo element, which may damage the piezo element. is there.

  The present invention has been made in view of the above points, and an object of the present invention is to prevent wear of a contact portion and prevent damage to a piezo element.

  In order to achieve the above object, according to the first aspect of the present invention, the lead hole for taking out the housing hole (17) and the lead wire (411) into which the piezo actuator (4) is housed and fuel is introduced. A cylindrical body (1) in which a take-out hole (18) is formed is provided, and a lead wire take-out hole (18) from the storage hole (17) by a sealing means (414) arranged on one end side of the piezo actuator (4). Is prevented from flowing out, and the annular facing surface (413c) formed on the piezo actuator (4) and the annular facing surface (19) formed on the body (1) are accommodated more than the sealing means (414). In the injector in which the piezo actuator (4) is positioned in the axial direction by abutting at the position on the hole (17) side, the portions that are in contact with each other in the opposing surfaces (19, 413c) When the contact portion (A) is used, a fuel guide passage (413e) for guiding the fuel in the storage hole (17) to the contact portion (A) is provided on the opposing surface (19, 413c). .

  According to this, the fuel guided to the contact part (A) brings the contact part (A) into a fluid lubrication state, and the flow of fuel guided to the contact part (A) promotes the discharge of wear powder. In combination with this, wear of the contact portion (A) is suppressed.

  According to a second aspect of the present invention, in the injector according to the first aspect, one of the opposed surface (413c) of the piezo actuator (4) and the opposed surface (19) of the body (1) is a conical surface. Is a spherical surface. According to this, alignment of the piezoelectric actuator (4) and the body (1) is easy.

  According to a third aspect of the invention, in the injector according to the first or second aspect, the fuel guide passage (413e) is a groove and is provided only on the opposing surface (413c) of the piezo actuator (4). It is characterized by that.

  According to this, since the opposing surface (19) of the body (1) is the back of the hole, the opposing surface (413c) of the piezo actuator (4) is the outer surface, so that the groove can be easily processed.

  According to a fourth aspect of the present invention, in the injector according to any one of the first to third aspects, the fuel guide passage (413e) is a radial line when viewed in the axial direction of the piezo actuator (4). It is characterized by being inclined with respect to.

  According to this, fuel lubrication to the entire circumference of the contact portion (A) is easier than when the fuel guide passage (413e) is made radial.

  According to a fifth aspect of the present invention, in the injector according to any one of the first to fourth aspects, a plurality of fuel guide passages (413e) are arranged along the circumferential direction. According to this, fuel lubrication to the entire circumference of the contact portion (A) is easy to be performed.

  According to a sixth aspect of the invention, in the injector of the fifth aspect, the fuel guide passages (413e) are arranged at equal intervals along the circumferential direction. According to this, fuel lubrication can be uniformly performed on the entire circumference of the contact portion (A).

  According to a seventh aspect of the present invention, in the injector according to any one of the first to sixth aspects, the fuel pressure in the storage hole (17) is controlled to be higher than the atmospheric pressure, and the body (1) A low-pressure fuel passage (16) for returning the fuel to the fuel tank (100), and a storage hole (17) at a position on the side opposite to the lead-out hole (18) from the opposing surface (413c) of the piezoelectric actuator (4). An injector comprising a low-pressure communication passage (16a) communicating with the low-pressure fuel passage (16), wherein the volume of the space between the contact portion (A) and the low-pressure communication passage (16a) is V1, and the contact V2> (Pb / P0− when the volume of the space between the part (A) and the sealing means (414) is V2, the atmospheric pressure is P0, and the control fuel pressure in the storage hole (17) is Pb. 1) It is V1.

  By the way, when the injector is used with the lead wire extraction hole (18) above the storage hole (17), for example, if air enters the storage hole (17) due to lack of gas, the contact portion (A) And air accumulates in the space between the low pressure communication passage (16a) and the space between the contact portion (A) and the sealing means (414). However, by setting V2> (Pb / P0-1) V1, when the inside of the storage hole (17) rises to the control fuel pressure Pb, the air is compressed and the liquid level reaches above the contact portion (A). Ascending, the contact portion (A) is lubricated.

  In addition, the code | symbol in the bracket | parenthesis of each means described in a claim and this column shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 is a diagram schematically showing an overall configuration of a fuel injection device including an injector according to the first embodiment.

  The injector is attached to a cylinder head of an internal combustion engine (more specifically, a diesel engine, not shown), and injects high-pressure fuel stored in a pressure accumulator (not shown) into the cylinder of the internal combustion engine. .

  As shown in FIG. 1, an injector body 1 is made of metal, a fuel inlet portion 11 into which high-pressure fuel from an accumulator is introduced, and a fuel outlet portion that allows fuel inside the injector to flow out toward a fuel tank 100. 12.

  A nozzle 2 that injects fuel when the valve is opened is disposed on one end side of the body 1 in the axial direction. The nozzle 2 includes a needle 21 slidably held on the body 1, a nozzle spring 22 that urges the needle 21 in a valve closing direction, and a nozzle cylinder 23 in which a piston portion 21 a of the needle 21 is inserted. is doing.

  At one end of the body 1 in the axial direction, an injection hole 24 communicating with the fuel inlet 11 through the high-pressure fuel passage 13 is formed, and high-pressure fuel is injected from the injection hole 24 into the cylinder of the internal combustion engine. Yes. A tapered valve seat 25 is formed on the upstream side of the injection hole 24, and the injection hole 24 is opened and closed when the seat portion 21 b formed on the needle 21 contacts and separates from the valve seat 25.

  The piston part 21a is slidably and liquid-tightly inserted into the nozzle cylinder 23. The piston part 21a and the nozzle cylinder 23 form a control chamber 26 in which the internal fuel pressure can be switched between high pressure and low pressure. ing. The needle 21 is urged in the valve closing direction by the fuel pressure in the control chamber 26 and is opened in the valve opening direction by the high pressure fuel guided from the fuel inlet 11 to the nozzle hole 24 side through the high pressure fuel passage 13. Be energized.

  A valve chamber 14 in which the control valve 3 for controlling the pressure in the control chamber 26 is housed is formed in the intermediate portion in the axial direction of the body 1. The valve chamber 14 is always in communication with the control chamber 26 via the communication passage 15. The valve chamber 14 is connected to a high pressure communication passage 13 a branched from the high pressure fuel passage 13. Further, the valve chamber 14 is connected to the fuel outlet portion 12 through a low-pressure fuel passage 16.

  The control valve 3 is opened between the valve chamber 14 and the high pressure communication passage 13a and between the valve chamber 14 and the high pressure communication passage 13a, and between the valve chamber 14 and the high pressure communication passage 13a. In addition, a valve spring 32 that biases the valve body 31 in a direction in which the space between the valve chamber 14 and the low-pressure fuel passage 16 is closed is provided.

  The body 1 is formed with a cylindrical storage hole 17 on the other end side in the axial direction from the valve chamber 14 in which the actuator 4 that drives the control valve 3 is stored. The storage hole 17 is connected to the low pressure fuel passage 16 via the low pressure communication passage 16a.

  The actuator 4 includes a cylindrical piezo actuator 41 in which a large number of piezo elements are stacked and expands and contracts due to charge and discharge, and a transmission unit that transmits the expansion and contraction displacement of the piezo actuator 41 to the valve body 31 of the control valve 3. .

  Two lead wires 411 for power feeding are joined to the piezoelectric actuator 41. A cylindrical lead wire extraction hole 18 for extracting the lead wire 411 to the outside is formed on the other end side in the axial direction of the body 1.

  The transmission part of the actuator 4 is configured as follows. A first piston 43 and a second piston 44 are slidably and liquid-tightly inserted into the actuator cylinder 42, and a liquid chamber filled with fuel is provided between the first piston 43 and the second piston 44. 45 is formed.

  The first piston 43 is urged toward the piezo actuator 41 by a first spring 46 and is directly driven by the piezo actuator 41. When the piezoelectric actuator 41 is extended, the pressure of the liquid chamber 45 is increased by the first piston 43.

  The second piston 44 is urged toward the valve body 31 side of the control valve 3 by the second spring 47 and is actuated by receiving the pressure of the liquid chamber 45 to drive the valve body 31. When the piezo actuator 41 is extended, the second piston 44 operates by receiving the pressure of the liquid chamber 45 that has been increased in pressure, and the space between the valve chamber 14 and the high-pressure communication passage 13a is closed and the valve chamber 14 The valve body 31 is driven to a position where the space between the low pressure fuel passage 16 is opened. On the other hand, when the piezoelectric actuator 41 contracts, that is, when the pressure in the liquid chamber 45 is low, the second piston 44 is pushed back toward the first piston 43 by the valve spring 32 of the control valve 3 against the second spring 47.

  A back pressure valve 120 that controls the pressure on the low pressure fuel passage 16 side is disposed in the return path 110 that connects the fuel tank 100 and the fuel outlet portion 12. Incidentally, while the pressure of the high pressure fuel stored in the pressure accumulator is 100 MPa or more, the back pressure valve 120 controls the pressure on the low pressure fuel passage 16 side to about 1 MPa.

  Electric power is supplied to the piezo actuator 41 via the piezo drive circuit 130. The piezo drive circuit 130 can control the voltage applied to the piezo actuator 41 in order to change the extension amount of the piezo actuator 41. Further, in the piezo drive circuit 130, the applied voltage to the piezo actuator 41 and the energization timing to the piezo actuator 41 are controlled by an electronic control circuit (hereinafter referred to as ECU) 140.

  The ECU 140 includes a well-known microcomputer including a CPU, ROM, EEPROM, RAM, and the like (not shown), and performs arithmetic processing according to a program stored in the microcomputer. The ECU 140 receives signals from various sensors (not shown) that detect the intake air amount, the accelerator pedal depression amount, the internal combustion engine speed, the fuel pressure in the accumulator, and the like.

  2 is a front cross-sectional view of the main part of the injector of FIG. 1, FIG. 3 (a) is a front view showing the holding member 413 alone of FIG. 2, and FIG. 3 (b) is a plan view of FIG.

  As shown in FIGS. 2 and 3, the body 1 is formed with an annular body-side facing surface 19 at the boundary between the accommodation hole 17 and the lead wire take-out hole 18. The body-side facing surface 19 is a conical surface that expands from the lead wire take-out hole 18 side toward the storage hole 17 side.

  The piezo actuator 41 includes a piezo stack 412 in which a large number of piezo elements are stacked, and one end of the piezo stack 412 is held by a metal-made cylindrical holding member 413. The lead wire 411 is led from the piezo stack 412 to the lead wire take-out hole 18 through a hole (not shown) formed in the holding member 413. Further, the gap between the lead wire 411 and the holding member 413 is sealed by a seal member (not shown).

The holding member 413 includes a large-diameter portion 413a disposed in the storage hole 17, a small-diameter portion 413b having a smaller diameter than the large-diameter portion 413a and disposed in the lead wire take-out hole 18, and a large-diameter portion 413a and a small-diameter portion. And an annular holding member side facing surface 413c formed at the boundary portion of 413b. The holding member side facing surface 413c is a spherical surface that expands from the small diameter portion 413b side toward the large diameter portion 413a side. The holding member side facing surface 413c is in contact with the body side facing surface 19 so that the piezo actuator 41 is positioned in the axial direction. The opposing surfaces 19 and 413c are in line contact with each other in a ring shape at a portion indicated by a one-dot chain line. Since the holding member side facing surface 413c is a spherical surface and the body side facing surface 19 is a conical surface, alignment of the piezo actuator 41 and the body 1 is easy.

  An annular O-ring groove 413d is formed on the outer peripheral surface of the small-diameter portion 413b, and an O-ring 414 as a sealing means is disposed in the O-ring groove 413d. The O-ring 414 prevents fuel from flowing from the storage hole 17 to the lead wire extraction hole 18.

  A fuel guide passage 413e that guides the fuel in the storage hole 17 to the contact portion A is provided on the holding member side facing surface 413c. The fuel guide passage 413e is a groove that is continuous from the end on the holding member side facing surface 413c on the large diameter portion 413a side to the end on the small diameter portion 413b side, and is radially spaced at equal intervals along the circumferential direction. Is arranged. The fuel guide passage 413e is provided only on the holding member side facing surface 413c among the facing surfaces 19, 413c, and is formed by cutting, laser processing, electric discharge machining, or the like. Since the body-side facing surface 19 is at the back of the hole, the holding member-side facing surface 413c is an outer surface, and therefore, the fuel guide passage 413e is provided rather than the case where the fuel guide passage 413e is provided on the body-side facing surface 19. Is easy to process.

  Here, as shown in FIG. 2, when the injector is used in a state where the lead wire extraction hole 18 is above the storage hole 17, if air is mixed into the storage hole 17 due to lack of gas, for example, Air accumulates in the space from the upper end of the communication passage 16a to the O-ring 414.

  The volume of the space between the contact portion A and the upper end of the low-pressure communication passage 16 in the space in which the air accumulates is V1, and the volume of the space between the contact portion A and the O-ring 414 in the space in which the air accumulates. Is set to V2, the atmospheric pressure is set to P0, and the control fuel pressure in the storage hole 17 controlled by the back pressure valve 120 is set to Pb, the volumes V1, V2 so that V2> (Pb / P0-1) V1. Is set.

  Next, the operation of the fuel injection device will be described. First, when the piezo actuator 41 is energized, the piezo actuator 41 extends to drive the first piston 43, and the pressure of the liquid chamber 45 is increased by the first piston 43. The second piston 44 is driven toward the valve body 31 side of the control valve 3 by the pressure of the liquid chamber 45 that has been increased in pressure. When the valve body 31 is driven by the second piston 44, the valve chamber 14 and the high-pressure communication passage 13a are closed, and the valve chamber 14 and the low-pressure fuel passage 16 are opened.

  As a result, the pressure in the control chamber 26 decreases and the force for urging the needle 21 in the valve closing direction is reduced, so that the needle 21 moves in the valve opening direction, and the seat portion 21b moves away from the valve seat 25 and the injection hole. 24 is opened, and fuel is injected from the nozzle hole 24 into the cylinder of the internal combustion engine.

  Thereafter, when the energization to the piezo actuator 41 is stopped, the piezo actuator 41 contracts, so that the first piston 43 is returned to the piezo actuator 41 side by the first spring 46. Further, the valve body 31 and the second piston 44 are returned to the first piston 43 side by the valve spring 32.

  Thereby, the space between the valve chamber 14 and the high-pressure communication passage 13a is opened, and the space between the valve chamber 14 and the low-pressure fuel passage 16 is closed. Therefore, the high pressure fuel from the pressure accumulator is introduced into the control chamber 26 via the high pressure fuel passage 13, the high pressure communication passage 13 a, the valve chamber 14, and the communication passage 15.

  As a result, the pressure in the control chamber 26 rises and the force for urging the needle 21 in the valve closing direction increases, so that the needle 21 moves in the valve closing direction, and the seat portion 21b is seated on the valve seat 25 and sprayed. The hole 24 is closed and the fuel injection is finished.

  During the above operation, the fuel in the storage hole 17 is guided to the contact portion A by the fuel guide passage 413e, so that the contact portion A is in a fluid lubrication state. Further, the abrasion powder is discharged from the contact portion A to other parts by the flow of fuel guided to the contact portion A. Therefore, the contact portion A is brought into a fluid lubrication state and the discharge of wear powder is promoted, so that the wear of the contact portion A is suppressed.

  In addition, since a plurality of fuel guide passages 413e are arranged along the circumferential direction, fuel lubrication to the entire circumference of the contact portion A is easy, and furthermore, the fuel guide passages 413e are equally spaced along the circumferential direction. Due to the arrangement, fuel lubrication can be uniformly performed on the entire circumference of the contact portion A.

  Further, when the injector is used in a state in which the lead wire extraction hole 18 is above the storage hole 17, for example, if air enters the storage hole 17 due to lack of gas, the space from the upper end of the low-pressure communication passage 16a to the ring 414 Air accumulates in the air. However, since V2> (Pb / P0-1) V1, the air accumulated in the space from the upper end of the low-pressure communication passage 16a to the O-ring 414 when the inside of the storage hole 17 rises to the control fuel pressure Pb after refueling. Is compressed and the liquid level rises above the contact portion A, and the contact portion A is reliably lubricated.

(Second Embodiment)
A second embodiment of the present invention will be described. FIG. 4A is a front view showing a holding member 413 alone in the injector according to the second embodiment, and FIG. 4B is a plan view of FIG. The same or equivalent parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  Although the fuel guide passages 413e in the injector according to the first embodiment are arranged radially, the fuel guide passages 413e of this embodiment are arranged in a radial line when viewed in the axial direction of the piezo actuator as shown in FIG. It is inclined with respect to. In this case, when the fuel flows through the fuel guide passage 413e, the fuel moves while rotating in the circumferential direction. Therefore, fuel lubrication to the entire circumference of the contact portion A is performed more than when the fuel guide passage 413e is made radial. Cheap.

(Other embodiments)
In each of the above embodiments, the fuel guide passage 413e is provided only on the holding member side facing surface 413c. However, the fuel guide passage 413e may be provided only on the body side facing surface 19, or the holding member side facing surface 413c and the body. It may be provided on both side facing surfaces 19.

  In each of the above embodiments, the body side facing surface 19 is a conical surface and the holding member side facing surface 413c is a spherical surface. However, the body side facing surface 19 is a spherical surface and the holding member side facing surface 413c is a conical surface. Alternatively, both the body side facing surface 19 and the holding member side facing surface 413c may be conical surfaces. Further, it may be a curved surface other than a spherical surface. Furthermore, both the body side facing surface 19 and the holding member side facing surface 413c may be flat surfaces perpendicular to the axis of the piezo actuator.

  The fuel guide passage 413e may be arranged in a mesh shape. In this case, the fuel guide passage 413e can be formed by pressing or cutting.

It is a figure showing typically the whole fuel injection device composition provided with the injector concerning a 1st embodiment of the present invention. FIG. 2 is a front sectional view of a main part of the injector of FIG. (A) is a front view which shows the holding member 413 single-piece | unit of FIG. 2, (b) is a top view of (a). (A) is a front view which shows the holding member 413 single-piece | unit in the injector which concerns on 2nd Embodiment of this invention, (b) is a top view of (a).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Body, 2 ... Nozzle, 4 ... Piezo actuator, 17 ... Storage hole, 18 ... Lead wire taking-out hole, 19 ... Opposing surface, 411 ... Lead wire, 413c ... Opposing surface, 413e ... Fuel guide passage, 414 ... O-ring (Sealing means), A: contact portion.

Claims (7)

A cylindrical piezo actuator (4) that expands and contracts by charge and discharge of electric charge;
A power supply lead wire (411) joined to the piezoelectric actuator (4);
A nozzle (2) that opens or closes according to the energization state of the piezo actuator (4) and injects fuel when the valve is opened;
A tubular body (17) in which the piezoelectric actuator (4) is stored and a storage hole (17) for introducing fuel and a lead wire extraction hole (18) for extracting the lead wire (411) to the outside are formed. 1)
The seal means (414) disposed on one end side of the piezo actuator (4) prevents fuel from flowing out from the storage hole (17) into the lead wire take-out hole (18),
An annular facing surface (413c) formed on the piezo actuator (4) and an annular facing surface (19) formed on the body (1) are formed in the housing hole (17) more than the sealing means (414). In the injector in which the piezoelectric actuator (4) is positioned in the axial direction by contacting at a position on the side,
A fuel guide passage (413e) that guides the fuel in the storage hole (17) to the contact portion (A) when the contact portion in the opposing surfaces (19, 413c) is the contact portion (A). Is provided on the facing surface (19, 413c). The injector according to claim 1, wherein one of the opposing surface (413c) of the piezoelectric actuator (4) and the opposing surface (19) of the body (1) is a conical surface and the other is a spherical surface. . The injector according to claim 1 or 2, wherein the fuel guide passage (413e) is a groove and is provided only on a facing surface (413c) of the piezo actuator (4). The fuel guide passage (413e) is inclined with respect to a radial line when viewed in the axial direction of the piezo actuator (4). The described injector. The injector according to any one of claims 1 to 4, wherein a plurality of the fuel guide passages (413e) are arranged along a circumferential direction. The injector according to claim 5, wherein the fuel guide passages (413e) are arranged at equal intervals along a circumferential direction. The fuel pressure in the storage hole (17) is controlled to be higher than atmospheric pressure;
The body (1) has a low pressure fuel passage (16) for returning leaked fuel to the fuel tank (100), and a side opposite to the lead wire extraction hole (18) from the opposing surface (413c) of the piezoelectric actuator (4). An injector comprising a low-pressure communication passage (16a) communicating the storage hole (17) and the low-pressure fuel passage (16) at a position of
The volume of the space between the contact part (A) and the low-pressure communication passage (16a) is V1,
The volume of the space between the contact part (A) and the sealing means (414) is V2,
The atmospheric pressure is P0,
When the control fuel pressure in the storage hole (17) is Pb,
The injector according to any one of claims 1 to 6, wherein V2> (Pb / P0-1) V1.

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