JP2008303820A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve capable of restraining an increase in a leakage quantity, when driving a valve element from a clearance formed between a large diameter part of the valve element including a small diameter part and the large diameter part and a sleeve installed in the large diameter part. <P>SOLUTION: In this fuel injection valve 1, a needle 3 is fitted in a nozzle body 2 in a slidable state, and injection from a nozzle port 2a of fuel supplied under predetermined pressure, is allowed or checked by moving the needle 3. A needle driving chamber 42 for driving the needle 3 and a pressurizing chamber 33 are communicated by a communicating passage 43. The sleeve 24 is fitted to the large diameter part 21 of the needle 3 in the slidable state. The communicating passage 43 is connected to the needle driving chamber 42 via an outer peripheral surface of the sleeve 24. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel injection valve used for supplying fuel to an internal combustion engine.

  As a fuel injection valve used for fuel supply to an internal combustion engine, etc., a piezo element is used as a drive source of a valve body, and displacement caused by deformation of the piezo element is amplified by a hydraulic mechanism using Pascal's principle. One that drives a valve body in a predetermined direction by transmitting to the valve body is widely known. For example, as this type of fuel injection valve, a stepped valve body including a small diameter portion and a large diameter portion is provided with a hole formed in the nozzle body and a collar provided above the nozzle body and a small diameter portion. By fitting the sleeve that is slid into the large diameter part of the valve body in a slidable state, the upper end surface of the collar and the inner circumference of the sleeve are fitted. A control chamber surrounded by the surface and the outer peripheral surface of the stepped valve body is formed, and the valve body is driven by applying fuel pressure (hydraulic pressure) to the control chamber by utilizing deformation of the piezo element. There is a thing (patent document 1).

JP 2006-524298 A

  In the fuel injection valve described in Patent Document 1, when the hydraulic pressure is applied to the control chamber, the hydraulic pressure acts on the inner peripheral surface of the sleeve. There is a risk that the amount of fuel leakage in the control chamber will increase due to a change in the clearance direction. When the amount of leakage increases, problems such as difficulty in maintaining the valve element in the valve open state for a long period of time and an increase in electric energy input to the piezo element arise.

  Therefore, the present invention increases the amount of leakage when driving the valve body from the clearance formed between the large diameter portion of the valve body including the small diameter portion and the large diameter portion and the sleeve attached to the large diameter portion. It aims at providing the fuel injection valve which can suppress this.

  The fuel injection valve according to the present invention prevents the fuel supplied at a predetermined pressure from being injected from the nozzle hole by being seated on the nozzle body provided with the nozzle hole and the valve seat. A valve body that moves in a direction away from the valve seat from the valve closing position and allows the fuel to be injected from the nozzle hole, and a valve that urges the valve body in a direction of seating on the valve seat A body urging member; and valve body driving means for driving the valve body in a direction away from the valve seat, wherein the nozzle body is located on a side closer to the nozzle hole, the nozzle hole A step which is located on the side far from the small-diameter hole portion and has a larger diameter than the small-diameter hole portion and a step portion formed at the boundary between the small-diameter hole portion and the large-diameter hole portion and communicates with the nozzle hole A small-diameter portion which has a hole and the valve body is located on the side close to the nozzle hole, and the small-diameter A large-diameter portion having an outer diameter larger than an outer diameter of the large-diameter hole portion and smaller than an inner diameter of the large-diameter hole portion, and the step portion of the stepped hole formed at a boundary between the small-diameter portion and the large-diameter portion. A fuel injection valve that is accommodated in the stepped hole of the nozzle body in a state in which the small diameter portion and the small diameter hole portion are slidably fitted to each other. A sleeve that is fitted to the large-diameter portion of the body in a slidable state and is accommodated in the stepped hole of the nozzle body, and a partition that blocks the opening of the stepped hole located on the far side from the nozzle hole The valve body drive means further comprises: a wall portion; and a sleeve urging member that urges the sleeve so that an end portion of the sleeve located on the side far from the nozzle hole abuts against the partition wall portion, The cylinder into which the piston is reciprocally inserted and the piston A pumping means including a pressurizing chamber partitioned by a ton and the cylinder and capable of operating the piston in a direction in which the volume of the pressurizing chamber decreases with a predetermined driving source, the small diameter portion of the valve body, The valve body driving chamber connected to the pressurizing chamber of the pump means and the valve body driving chamber defined by the stepped portion of the stepped hole and the stepped portion of the valve body, and the valve body driving via the outer peripheral surface of the sleeve A communication passage that connects the pressurizing chamber and the valve body drive chamber by being connected to a chamber, and the pump means operates the piston to operate the pressurizing chamber, the valve body operating chamber, and The above-described problem is solved by driving the valve body in the direction of separating from the valve seat via the fuel supplied into the communication passage.

  According to this fuel injection valve, since the counterpart sliding on the large diameter portion of the valve body is a sleeve separate from the nozzle body, it is formed between the small diameter portion of the valve body and the small diameter hole portion of the stepped hole. And the clearance formed between the large diameter portion of the valve body and the inner peripheral surface of the sleeve can be set separately. Thereby, these clearances can be easily made small without being restricted by processing. As a result, since the amount of leakage from these sliding parts can be reduced, it is easy to hold the valve element in the open state for a long period of time, and the energy input to the drive source of the pump means can be suppressed.

  Further, when the valve element is driven, the pressure in the communication path increases, and this communication path is connected to the valve element drive chamber via the outer peripheral surface of the sleeve. For this reason, when the valve body is driven, pressure acts in a direction in which the sleeve is tightened, so that the clearance formed between the large diameter portion of the valve body and the sleeve does not increase. Therefore, it is possible to suppress an increase in leakage from the clearance when the valve element is driven.

  Further, since the valve body is accommodated in the stepped hole and the opening of the stepped hole is blocked by the partition wall portion, the end portion of the valve body in the direction away from the valve seat is the partition wall portion. It can move until it hits. That is, since the maximum lift amount of the valve body is physically set as the interval between the end portion and the partition wall portion, it becomes easy to precisely manage the maximum lift amount of the valve body. Thereby, there is an advantage that it is possible to provide a plurality of homogeneous fuel injection valves in which variations in injection rate are suppressed.

  In one aspect of the fuel injection valve of the present invention, the valve body is provided with a valve body passage that has an opening that opens on a tip end side thereof and that is supplied with fuel to be injected from the nozzle hole. The valve body passage is configured to communicate with a gap defined by the partition wall portion, an end portion of the valve body far from the nozzle hole, and an inner peripheral surface of the sleeve, and the sleeve The end portion may be formed in a tapered shape whose inner peripheral surface side is inclined radially outward toward the partition wall portion (Claim 2). According to this aspect, the phenomenon that the pressure in the valve body drive chamber and the communication passage is temporarily lower than the pressure in the valve body passage during driving of the valve body is used as the working liquid for the valve body drive means. The fuel can be supplied or replenished. That is, when the pressure in the valve body drive chamber and the communication passage is lower than the pressure in the valve body passage, the pressure acting on the inner peripheral surface side of the sleeve becomes larger than the pressure acting on the outer peripheral surface side. And since the edge part is comprised by the inner peripheral surface side in the taper shape, the force of the direction away from a partition wall part acts on a sleeve. The force overcomes the urging force of the sleeve urging means, whereby a gap is temporarily formed between the end of the sleeve and the partition wall. Supply or replenishment of fuel to the valve body driving means is realized by the fuel filled in the valve body passage going into the communication passage through the temporarily formed gap. Therefore, this embodiment has an advantage that it is not necessary to provide a dedicated passage for supplying or replenishing the fuel as the working liquid to the valve body driving means.

  In one aspect of the fuel injection valve of the present invention, an elastic member that urges the sleeve so that the end portion of the sleeve abuts against the partition wall portion by an elastic force is provided as the sleeve urging means. The sleeve is located on the side close to the nozzle hole, has a smaller outer diameter than the outer diameter on the side far from the nozzle hole and extends in the longitudinal direction, and the sleeve on the side far from the nozzle hole. It may have a seat surface provided at an end of the thin portion and against which one end of the elastic member is abutted. According to this aspect, since the elastic member can be mounted between the seat surface of the sleeve and the step portion of the stepped hole, the contact area between the inner peripheral surface of the sleeve and the outer peripheral surface of the large diameter portion is sacrificed. Without attaching an elastic member. In addition, since the interval between the sleeve and the stepped portion of the stepped hole and the longitudinal dimension of the thin portion can be set separately, the use of the sleeve of this aspect increases the selection range of applicable elastic members. Good results.

  As described above, according to the present invention, since the communication path is connected to the valve body drive chamber via the outer peripheral surface of the sleeve, the pressure acts in the direction in which the sleeve is tightened when the valve body is driven. The clearance formed between the large diameter portion of the valve body and the sleeve does not expand. Therefore, it is possible to suppress an increase in leakage from the clearance when the valve element is driven.

  FIG. 1 is a cross-sectional view showing a main part of a fuel injection valve according to an embodiment of the present invention, and FIG. 2 is a partially enlarged view of FIG. The fuel injection valve 1 is configured as a fuel injection valve mounted on a direct injection gasoline engine that directly injects fuel into a cylinder. The fuel injection valve 1 is supplied with gasoline (fuel) held at a predetermined pressure in a pressure accumulation chamber (not shown). The fuel injection valve 1 includes a nozzle body 2 provided with an injection hole 2 a that opens in a predetermined direction, and a needle 3 as a valve body that is slidably supported by the nozzle body 2. The nozzle body 2 is provided with a valve seat 2b on which the needle 3 can be seated. The nozzle body 2 and the needle 3 are fixed to the housing 5 with a distance piece 4 as a partition wall interposed. These parts are fixed by screwing the cap 6 formed with a support hole 6 a for exposing a part of the nozzle body 2 into the housing 5.

  The housing 5 is provided with an intake 8 for taking in fuel, and the intake 8 communicates with the fuel passage 9. The fuel passage 9 includes a housing passage 10 formed in the housing 5, a needle passage 11 as a valve body passage formed in the needle 3, and a communication formed in the distance piece 4 to communicate the housing passage 10 and the needle passage 11. And a passage 12. The needle passage 11 has an opening 11a that opens to the distal end side of the needle 3, and a back pressure chamber 13 is formed between the communication passage 12 and the opening 11a. A return spring 14 as a valve body urging means is mounted inside the back pressure chamber 13, and the return spring 14 urges the needle 3 in the direction of seating on the valve seat 2b by its elastic force. FIG. 1 shows a valve closing position where the needle 3 is seated on the valve seat 2b. Since the nozzle 3 is held at this position, the nozzle hole 2a is closed. The injection from the nozzle hole 2a is prevented. On the other hand, since the nozzle hole 2a is opened when the needle 3 moves away from the valve seat 2b from the valve closing position in FIG. 1, the fuel guided in the fuel passage 9 may be injected from the nozzle hole 2a. Permissible.

  The nozzle body 2 has a stepped hole 16 having a different diameter for supporting the needle 3 slidably. The stepped hole 16 is formed axially symmetrical with respect to the center line CL so as to communicate with the nozzle hole 2a, and has a small diameter hole portion 17 located on the side close to the nozzle hole 2a, and a side far from the nozzle hole 2a. A large-diameter hole portion 18 having an inner diameter larger than that of the small-diameter hole portion 17 and a step portion 19 formed at the boundary between the small-diameter hole portion 17 and the large-diameter hole portion 18. The step portion 19 is configured as an annular surface orthogonal to the center line CL.

  The needle 3 is accommodated in the stepped hole 16 of the nozzle body 2. The needle 3 has a small-diameter portion 20 located on the side closer to the nozzle hole 2a, and is located farther from the nozzle hole 2a than the outer diameter of the small-diameter portion 20 and larger than the inner diameter of the large-diameter hole portion 18 of the stepped hole 16. A large-diameter portion 21 having a small outer diameter and a step portion 22 formed at the boundary between the small-diameter portion 20 and the large-diameter portion 21 and facing the step portion 19 of the stepped hole 16 are provided. The small diameter part 20 of the needle 3 and the small diameter hole part 17 of the stepped hole 16 are slidably fitted.

  As shown also in FIG. 2, the sleeve 24 accommodated in the stepped hole 16 is fitted in the large diameter part 21 of the needle 3 in a slidable state. The sleeve 24 has an inner peripheral surface 25 that can contact substantially the entire outer periphery of the large-diameter portion 21 of the needle 3. The end 24a of the sleeve 24 far from the nozzle hole 2a is abutted against the distance piece 4 by the elastic force of the coil spring 26 as a sleeve biasing means. The end 24 a of the sleeve 24 is formed in a tapered shape in which the inner peripheral surface side is inclined radially outward toward the distance piece 4. A gap X is defined by the inner peripheral surface of the sleeve 24, the distance piece 4 and the end 3a of the needle 3 far from the nozzle hole 2a, and the gap X and the needle passage 11 are communicated with each other.

  The other end 24 b of the sleeve 24 is in a non-contact state with the stepped portion 19 so as to form a predetermined interval with the stepped portion 19 of the stepped hole 16. The sleeve 24 has a thin portion 27 which is located on the side close to the nozzle hole 2a and has an outer diameter smaller than the outer diameter on the side far from the nozzle hole 2a. The thin portion 27 extends in the longitudinal direction of the sleeve 24. A seat surface 27a against which one end of the coil spring 26 is abutted is provided at the end of the thin portion 27 far from the nozzle hole 2a. The coil spring 26 is mounted between the seat surface 27a and the stepped portion 19 so that one end thereof is abutted against the seat surface 27a and the other end is abutted against the stepped portion 19 of the stepped hole 16. Therefore, the coil spring 26 can be mounted without sacrificing the contact area between the inner peripheral surface 25 of the sleeve 24 and the outer peripheral surface of the large diameter portion 21.

  As shown in FIG. 1, the needle 3 is driven in a direction away from the valve seat 2b by a hydraulic mechanism 30 serving as a valve body driving means. The hydraulic mechanism 30 includes a pump unit 34 as a pump unit including a cylinder 32 into which a piston 31 is reciprocally inserted, a pressurizing chamber 33 defined by the piston 31, the cylinder 32 and the distance piece 4, and a pump. A drive unit 35 that transmits the work performed by the unit 34 to the needle 3 and drives the needle 3 is provided.

  The pump part 34 is provided in the housing 5. The upper and lower openings of the cylinder 32 are closed by the distance piece 4 positioned at the lower end of the cylinder 32 and the horizontal wall 5a of the housing 5 positioned at the upper end of the cylinder 32. A piston rod 36 extends above the piston 31 so as to penetrate the lateral wall 5a, and an upper end of the piston rod 36 contacts a piezo element 37 as a drive source. A seal ring 38 is provided between the lateral wall 5 a and the piston rod 36. The piston rod 36 is urged so as to abut against the piezo element 37 by the elastic force of the return spring 39. The return spring 39 is mounted between the spring seat 40 attached to the piston rod 36 and the lateral wall 5a. The piezo element 37 is a known element whose dimension in the direction of the center line CL changes in an increasing direction when a voltage is applied. The piezo element 37 is fixed by being fitted into the upper portion of the housing 5 with the upper end portion 37a interposing the seal ring 41, and a power supply wire 37b is drawn out from the upper end portion 37a. The electric wire 37b is connected to an electric circuit (not shown). When a voltage is applied to the piezo element 37, the piston rod 36 is pushed down by being deformed so as to increase the dimension in the direction of the center line CL, so that the piston 31 operates in a direction in which the volume of the pressurizing chamber 33 decreases.

  As shown in FIG. 2, the driving unit 35 includes a needle driving chamber 42 as a valve body driving chamber constituted by the nozzle body 2 and the needle 3, and a pressurizing chamber 33 and a needle driving chamber 42 of the pump unit 34. And a communication passage 43 communicating therewith. The needle drive chamber 42 is formed in an annular shape by being partitioned by the small diameter portion 20 of the needle 3, the step portion 19 of the stepped hole 16, and the step portion 22 of the needle 3. The communication passage 43 is formed in the distance piece 4 and opens to the pressurizing chamber 33, and an annular second passage 45 defined by the outer peripheral surface of the sleeve 24 and the inner peripheral surface of the large-diameter hole portion 18. Including.

  The hydraulic mechanism 30 uses the fuel supplied into the pressurizing chamber 33, the needle drive chamber 42 and the communication passage 43 as its working liquid. According to this hydraulic mechanism 30, the pump unit 34 drives the piston 31 to reduce the volume of the pressurizing chamber 33, whereby the volume of the needle drive chamber 42 is expanded by the fuel pushed out from the pressurizing chamber 33. . That is, the needle 3 can be driven in the direction of separating from the valve seat 2b through the fuel filled in the pressurizing chamber 33, the needle drive chamber 42 and the communication passage 43. The area of the pressure surface of the piston 31 is set to several times the area of the pressure receiving surface of the needle drive chamber 42. For this reason, the lift amount of the needle 3 corresponding to several times the displacement amount of the piston 31 can be ensured according to the Pascal principle. The lift amount means the amount of movement of the needle 3 from the valve closing position. Further, as shown in FIG. 1, the hydraulic mechanism 30 is provided with a drive auxiliary chamber 46 defined by a piston 31, a cylinder 32, and a lateral wall 5 a on the opposite side of the pressurizing chamber 33. Communicates with the fuel passage 9. For this reason, since the driving of the piston 31 by the pump unit 34 is assisted by the pressure of the fuel guided to the driving assistance chamber 46, the driving force of the piston 31 is reduced. That is, energy input to the piezo element 37 can be suppressed.

  Supplying or replenishing the fuel as the working liquid to the hydraulic mechanism 30 causes the pressure in the needle drive chamber 42 and the communication passage 43 to be temporarily lower than the pressure in the needle passage 11 (back pressure chamber 13) while the needle 3 is being driven. This is done using the phenomenon. That is, when the pressure in the needle drive chamber 42 and the communication passage 45 is lower than the pressure in the back pressure chamber 13, the pressure acting on the inner peripheral surface side of the sleeve 24 due to the pressure difference acts on the outer peripheral surface side of the sleeve 24. Bigger than. Since the end 24a of the sleeve 24 is tapered on the inner peripheral surface side, a downward force in the figure acts on the sleeve 24. When the force overcomes the elastic force of the coil spring 26, a gap is temporarily formed between the end 24a of the sleeve 24 and the distance piece 4. Supply or replenishment of fuel to the hydraulic mechanism 30 is realized by the fuel filled in the back pressure chamber 13 of the needle 3 flowing into the communication path 43 through the temporarily formed gap.

  According to the fuel injection valve 1 described above, the counterpart sliding on the large-diameter portion 20 of the needle 3 is the sleeve 24 that is separate from the nozzle body 2, and therefore the small-diameter portion 20 of the needle 3 and the small diameter of the stepped hole 16. The clearance formed between the hole portion 17 and the clearance formed between the large diameter portion 21 of the needle 3 and the inner peripheral surface of the sleeve 24 can be set separately. Thereby, these clearances can be easily made small without being restricted by processing. As a result, since the amount of leakage from these sliding portions can be reduced, it is easy to hold the needle 3 in a valve-opened state for a long period of time, and the electric energy input to the piezo element 37 can be suppressed.

  Further, when the needle 3 is driven, the pressure in the communication path 43 increases, but the communication path 45 is connected to the needle drive chamber 42 via the outer peripheral surface of the sleeve 24. For this reason, when the needle 3 is driven, pressure acts in the direction in which the sleeve 24 is tightened, so that the clearance formed between the large diameter portion 21 of the needle 3 and the sleeve 24 does not widen. Therefore, an increase in the amount of leakage from the clearance during driving of the needle 3 can be suppressed.

  Further, as shown in FIG. 2, the needle 3 is accommodated in the stepped hole 16 of the nozzle body 2, and the opening of the stepped hole 16 is closed by the distance piece 4. Can move until it hits the distance piece 4. That is, since the maximum lift amount of the needle 3 is physically set as the gap G between the upper end of the needle 3 and the distance piece 4, it becomes easy to precisely manage the maximum lift amount. Thereby, it is possible to easily provide a plurality of homogeneous fuel injection valves in which variations in injection rate are suppressed.

  This invention is not limited to the above form, It can implement with a various form. Although the present invention can be implemented as a fuel injection valve of a type in which a passage is formed in the valve body as shown in the figure, the present invention is pressurized to a space formed between the periphery of the valve body and the nozzle body with a predetermined pressure. It is also possible to implement as a fuel injection valve of a type to which a fresh fuel is supplied.

  The sleeve urging means is not limited to the coil spring as shown in the figure, and various elastic members such as a cylindrical slit spring having a plurality of slits, a wave washer, and a disc spring may be employed.

Sectional drawing which showed the principal part of the fuel injection valve which concerns on one form of this invention. The elements on larger scale of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection valve 2 Nozzle body 2a Injection hole 2b Valve seat 3 Needle (valve body)
4 Distance piece (partition wall)
11 Valve body passage 11a Opening part 14 Return spring (valve body urging member)
16 Stepped hole 17 Small diameter hole 18 Large diameter hole 19 Step part 20 Small diameter part 21 Large diameter part 22 Step part 24 Sleeve 24a End part 25 Inner peripheral surface 26 Coil spring (sleeve biasing member)
27 Thin portion 27a Seat surface 30 Hydraulic mechanism (valve drive means)
31 Piston 32 Cylinder 33 Pressurizing chamber 34 Pump part (pump means)
42 Needle drive chamber (valve drive chamber)
43 Communication path X Gap G Interval

Claims (3)

A nozzle body provided with an injection hole and a valve seat, and a valve closing position that prevents fuel supplied at a predetermined pressure from being injected from the injection hole by being seated on the valve seat. A valve body that moves in a separating direction and allows the fuel to be injected from the nozzle hole; a valve body urging member that urges the valve body in a direction of seating on the valve seat; and the valve Valve body driving means for driving the body in a direction away from the valve seat, and the nozzle body is located on the side farther from the nozzle hole, the small diameter hole portion located on the side closer to the nozzle hole The valve includes a large-diameter hole portion having an inner diameter larger than that of the small-diameter hole portion and a stepped portion formed at a boundary between the small-diameter hole portion and the large-diameter hole portion and communicates with the injection hole. The body has a small diameter portion located on the side closer to the nozzle hole and a larger diameter than the outer diameter of the small diameter portion. A large-diameter portion having an outer diameter smaller than the inner diameter of the large-diameter hole portion, and a step portion that is formed at a boundary between the small-diameter portion and the large-diameter portion and faces the step portion of the stepped hole. And the fuel injection valve accommodated in the stepped hole of the nozzle body in a state in which the small diameter portion and the small diameter hole portion are slidably fitted together,
A sleeve that is slidably fitted to the large-diameter portion of the valve body and is accommodated in the stepped hole of the nozzle body, and an opening of the stepped hole that is located on the side farther from the injection hole. A partition wall portion that closes; and a sleeve urging member that urges the sleeve so that an end portion of the sleeve located on a side far from the nozzle hole abuts against the partition wall portion,
The valve body driving means includes a cylinder into which a piston is reciprocally inserted, a pressurizing chamber defined by the piston and the cylinder, and a direction in which the volume of the pressurizing chamber decreases with a predetermined driving source. A pump means capable of operating the piston, a valve body drive chamber defined by the small diameter portion of the valve body, the step portion of the stepped hole, and the step portion of the valve body, and the addition of the pump means. A pumping means connected to the pressure chamber and connected to the valve body drive chamber via the outer peripheral surface of the sleeve to communicate the pressure chamber and the valve body drive chamber; Operating the piston in the direction of separating the valve body from the valve seat via the fuel supplied to the pressurizing chamber, the valve body working chamber, and the communication passage. Fuel injection valve. The valve body is provided with a valve body passage that has an opening that opens on a tip side thereof and that is supplied with fuel to be injected from the nozzle hole.
The valve body passage is configured to communicate with a gap defined by the partition wall portion, an end of the valve body on the side far from the nozzle hole, and an inner peripheral surface of the sleeve,
2. The fuel injection valve according to claim 1, wherein the end portion of the sleeve is formed in a tapered shape in which an inner peripheral surface side is inclined radially outward toward the partition wall portion. As the sleeve urging means, an elastic member that urges the sleeve so that the end portion of the sleeve abuts against the partition wall portion by an elastic force is provided,
The sleeve is located on the side close to the nozzle hole and has a thin wall portion having an outer diameter smaller than the outer diameter on the side far from the nozzle hole and extending in the longitudinal direction, and the thin wall portion on the side far from the nozzle hole. The fuel injection valve according to claim 1, further comprising a seat surface provided at an end and against which one end of the elastic member is abutted.

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