JP2004278358A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a stable action of a check valve to fill fuel into a displacement enlarging chamber, and to lessen a fluctuation between cycles by stabilizing a fuel filling state into the displacement enlarging chamber, in a fuel injection valve equipped with the displacement enlarging mechanism. <P>SOLUTION: Pressure in a control chamber 4 is increased or decreased by opening or closing an interval between the control chamber 4 and a return passage 11 for applying the pressure in the valve closing direction to a nozzle needle 3 with a valve 2. A piezo-drive part 103 to drive the valve 2 enlarges and transmits an expansion and contraction of a piezo-actuator 51 by means of a greater diameter piston 52, a small diameter piston 54, and displacement enlarging chamber 53. The check valve 6 to fill fuel into the displacement chamber 53 is provided in the greater diameter piston 52. An upstream fluid chamber 71 and the return passage 11 are connected to communicate with each other via a throttle 72 not so as to be affected by the influence of the pressure fluctuation of the return passage 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel injection valve for an internal combustion engine using a piezo actuator.
[0002]
[Prior art]
A fuel injection valve that injects high-pressure fuel into a diesel engine or the like is configured to open and close an injection hole that communicates with a high-pressure fuel passage by driving a nozzle needle with an actuator. In recent years, as such a fuel injection valve, a fuel injection valve using a piezo actuator having good responsiveness as a driving source has been proposed (for example, Patent Document 1). In this fuel injection valve, the displacement of the piezo actuator is enlarged by a displacement enlargement mechanism using a hydraulic lever, and the injection is controlled by operating the valve.
[0003]
[Patent Document 1]
JP-A-2001-41125
The displacement enlargement mechanism is provided with a displacement enlargement chamber filled with fuel as hydraulic oil between a large diameter piston driven by expansion and contraction of a piezo actuator and a small diameter piston for operating a valve. When the pressure in the displacement expansion chamber increases or decreases and the small-diameter piston that has received the pressure slides, the valve position is switched accordingly, and fuel injection is performed. That is, when the piezo actuator expands and the pressure in the displacement expansion chamber rises and reaches a predetermined pressure, the small-diameter piston pushes down the valve. When the valve is unseated and the return passage is opened, the pressure in the control chamber that applies hydraulic pressure to the nozzle needle decreases, and the nozzle needle opens. On the other hand, when the piezoelectric actuator contracts and the pressure in the displacement expansion chamber decreases, the valve is seated and the return passage is closed. Accordingly, the pressure in the control chamber increases again, and the nozzle needle closes.
[0005]
Further, in the displacement magnifying mechanism, when the piezo actuator expands to increase the pressure in the displacement magnifying chamber, the fuel in the displacement magnifying chamber leaks from the clearance between the large-diameter piston and the small-diameter piston. In order to compensate for this leaked fuel, in Patent Document 1, a check valve is provided by providing a passage opening to the displacement expansion chamber, and the pressure of the displacement expansion chamber is maintained by fuel flowing through the check valve at the end of injection. are doing.
[0006]
[Problems to be solved by the invention]
However, when the piezo actuator is extended, the small diameter piston starts to move, and at the same time, the valve is unseated, and the high pressure fuel is spilled to the return passage. Therefore, the pressure in the return passage is pulsated by the spill fuel. At this time, in the conventional structure, the other end of the passage provided with the check valve communicates with the return passage, so that the check valve operation is likely to be unstable due to the influence of the pressure pulsation in the return passage. As a result, there is a concern that the state of fuel filling to the displacement expansion chamber changes every time, and the inter-cycle fluctuation of the injection amount characteristic becomes large.
[0007]
An object of the present invention is to realize a stable operation of a check valve for replenishing fuel to a displacement expansion chamber in a fuel injection valve having a displacement expansion mechanism, and to stabilize a state of fuel filling to a displacement expansion chamber. Another object of the present invention is to obtain a highly controllable fuel injection valve having a stable injection amount characteristic with a small variation between cycles.
[0008]
[Means for Solving the Problems]
The fuel injection valve according to claim 1, wherein a control chamber for applying a pressure in a valve closing direction to the nozzle needle, a control valve for increasing and decreasing the pressure in the control chamber by opening and closing between the control chamber and a return passage; A drive unit for driving the control valve, wherein the drive unit slides between a large-diameter piston that slides along with expansion and contraction of a piezo actuator and a small-diameter piston that abuts on the control valve and slides integrally therewith, It has a displacement expansion chamber filled with a working fluid. The fuel injection valve is provided between the displacement expansion chamber and the return passage, and a check valve is provided to allow the control fluid to flow only in the direction of the displacement expansion chamber to compensate the control fluid in the displacement expansion chamber. A fluid chamber provided upstream of the check valve communicates with the return passage via a throttle.
[0009]
In the conventional configuration, since the high-pressure spill fuel is ejected into the return passage at the end of the injection, the pressure in the return passage pulsates, and the operation of the check valve becomes unstable due to the influence. On the other hand, in the configuration of the present invention, since the throttle is provided upstream of the check valve, it is possible to prevent pressure pulsation in the return passage from directly acting on the check valve. Further, since a fluid chamber having a predetermined capacity is formed between the check valve and the throttle, the check valve can be operated at a stable pressure. Therefore, the fuel filling state is stabilized, the fluctuation between cycles is reduced, and a fuel injection valve excellent in controllability can be realized.
[0010]
In the configuration of the second aspect, the large-diameter piston is hollow and the check valve is housed therein.
[0011]
Preferably, by installing the check valve in the large-diameter piston, the above-described effect can be obtained without increasing the size of the device.
[0012]
In the configuration of the third aspect, the large-diameter piston is hollow, and the check valve and the fluid chamber are accommodated therein.
[0013]
Preferably, by installing the check valve and the fluid chamber in the large-diameter piston, the device can be made smaller.
[0014]
In the configuration of the fourth aspect, the throttle includes a through-hole provided in the large-diameter piston and communicating the fluid chamber with a low-pressure portion on the outer periphery of the large-diameter piston.
[0015]
Specifically, a space that communicates with the return passage is provided on the outer periphery of the large-diameter piston, and a through-hole that communicates the space with the fluid chamber is formed in a side wall of the large-diameter piston to serve as the throttle. The above effects can be easily obtained.
[0016]
In the configuration of claim 5, the throttle comprises a sliding portion clearance formed between a cylinder on which the large-diameter piston slides and an outer peripheral surface of the large-diameter piston. A passage is provided for communication with the throttle.
[0017]
Alternatively, the clearance of the sliding portion on the outer periphery of the large-diameter piston may be the throttle, and the same effect can be obtained by communicating the clearance of the sliding portion with the fluid chamber via the passage.
[0018]
In the configuration of claim 6, one end of the large-diameter piston is opened to the fluid chamber, and the other end is opened to the outer peripheral surface of the large-diameter piston. And a passage serving as the above-described throttle is provided in communication with the low-pressure section.
[0019]
Alternatively, when the large-diameter piston is at the upper end position, the passage can be formed so as to be the throttle, and the same effect can be obtained.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a fuel injection valve 1 of the present invention, which is applied to, for example, a common rail fuel injection device of a diesel engine. The fuel injection valve 1 is provided corresponding to each cylinder of the diesel engine, and receives fuel supply from a common common rail (not shown). The fuel in the fuel tank (not shown) is fed to the common rail by a high-pressure supply pump (not shown) and stored at a predetermined high pressure corresponding to the injection pressure.
[0021]
The fuel injection valve 1 is mounted such that a nozzle portion 101 (lower end portion) having a nozzle needle 3 projects into a combustion chamber (not shown). The middle part of the fuel injection valve 1 constitutes a back pressure control part 102 having a valve 2 as a control valve, and the upper end part constitutes a piezo drive part 103. The fuel injection valve 1 has a housing 13, in which the components constituting the above-described parts 101 to 103 are housed, and are connected to a return passage 11 communicating with a fuel tank and an inlet communicating with a common rail. A passage such as the high-pressure passage 12 is formed.
[0022]
The nozzle portion 101 slidably holds the stepped nozzle needle 3 in a vertical hole 31 formed in the lower end portion of the housing 13. An annular oil sump chamber 32 is formed on the outer periphery of the lower half-diameter portion of the nozzle needle 3, and high-pressure fuel from a common rail is supplied to the oil sump chamber 32 that is always in communication with the high-pressure passage 12. A sack portion 33 is formed below the vertical hole 31 so as to be continuous therewith, and an injection hole 34 for fuel injection is formed through the sack portion 33 forming wall.
[0023]
When the nozzle needle 3 is at the lower end position, the tip of the conical shape is seated on a seat provided at the boundary between the sack portion 33 and the vertical hole 31, the sack portion 33 is closed, and the fuel flows from the oil reservoir chamber 32 to the injection hole 34. Shut off supply. When the nozzle needle 3 rises and separates from the seat and the sack portion 33 is opened, fuel is injected.
[0024]
The space defined by the upper end surface of the nozzle needle 3 and the wall surface of the vertical hole 31 is a control chamber 4 for applying a back pressure to the nozzle needle 3. The control chamber 4 is always in communication with the valve chamber 21 of the back pressure control unit 102 through the main orifice 41, and is always in communication with the high-pressure passage 15 through the sub-orifice 42. The main orifice 51 and the sub-orifice 42 Fuel as a control fluid introduced from the nozzle generates back pressure of the nozzle needle 3. This back pressure acts downward on the nozzle needle 3 and urges the nozzle needle 3 in the seating direction together with the spring 43 housed in the control chamber 4. On the other hand, the high-pressure fuel in the oil storage chamber 32 acts upward on the step surface of the nozzle needle 3 to urge the nozzle needle 3 in the unseating direction.
[0025]
The back pressure control unit 102 allows the valve 2 having a three-way valve structure to selectively seat on the low-pressure seat 22 provided on the ceiling surface of the valve chamber 21 or the high-pressure seat 23 provided on the bottom surface of the valve chamber 21 to switch the flow path. Has become. The low-pressure seat 22 and the high-pressure seat 23 are provided at positions facing the ceiling surface and the bottom surface of the valve chamber 21, and the low-pressure seat 22 communicates with the return passage 11 via the spill chamber 14. The high pressure sheet 23 communicates with the high pressure passage 12 via the passage 15.
[0026]
The sub-orifice 42 moderates the pressure drop in the control chamber 4 at the start of injection and slowly opens the nozzle needle 3. Has the function of closing the valve quickly.
[0027]
The valve 2 has a pressure-balanced structure, and has a large-diameter valve portion 2 a housed in a valve chamber 21 and a sliding portion 2 b that slides in a cylinder formed below a high-pressure seat 23. An annular space is formed on the outer periphery of the small diameter portion connecting the valve portion 2a and the sliding portion 2b, and a passage 15 communicating with the high-pressure passage 12 is opened here. When the valve 2 is at the upper end position, the top surface of the valve portion 2 a sits on the low-pressure seat 22 on the ceiling surface of the valve chamber 21, and shuts off between the valve chamber 21 and the spill chamber 14. When the valve 2 is at the lower end position, the lower tapered surface of the valve portion 2 a is seated on the high-pressure seat 22 on the bottom surface of the valve chamber 21, and shuts off between the valve chamber 21 and the passage 15.
[0028]
When the valve 2 is pressed and driven by the piezo drive unit 103, the operating state is switched. Accordingly, the pressure of the control chamber 4 communicating with the valve chamber 21, that is, the back pressure of the nozzle needle 3 increases and decreases. I do. Here, the diameter of the low-pressure seat 22, the diameter of the high-pressure seat 23, and the diameter of the sliding portion 2 b are substantially the same, and when the valve 2 is seated on the low-pressure seat 22, the high-pressure The force by which fuel urges the valve portion 2a upward and the force by which the sliding portion 2b urges downward are substantially balanced. Thus, the driving force required to push down the valve portion 2a and separate from the low-pressure seat 22 during fuel injection can be reduced. Preferably, if the diameter of the low-pressure seat 22 and the diameter of the high-pressure seat 23 are slightly larger than the diameter of the sliding portion 2b, unintended opening of the valve 2 can be prevented, or injection can be quickly terminated.
[0029]
A spring 25 is accommodated below the sliding portion 2b of the valve 2 to urge the valve 2 upward. The space in which the spring 25 is housed communicates with the spill chamber 14 via the communication passage 24, and the space is closed so that no damper force is generated. In this way, downward movement of the valve 2 is not suppressed, and the valve portion 2a can be quickly separated from the low-pressure seat 22 at the start of injection.
[0030]
The piezo drive unit 103 includes a piezo actuator 51, a large-diameter piston 52, and a small-diameter piston 54 arranged coaxially in the cylinder forming member 8 disposed above the valve chamber 21 in this order from the upper side. The large-diameter piston 52 and the small-diameter piston 54 are slidably held in a cylinder provided on the cylinder forming member 8. The space between the large-diameter piston 52 and the small-diameter piston 54 is filled with fuel to form a displacement expansion chamber 53.
[0031]
The piezo actuator 51 is a general one having a capacitor structure in which piezoelectric ceramic layers such as PZT and electrode layers are alternately stacked, and has a stacking direction, that is, a vertical direction, which is an expansion and contraction direction, and is charged and discharged by a driving device (not shown). It has become. A constant initial load is applied to the piezo actuator 51 by a piezo spring 55 provided on the outer periphery of the upper end of the large-diameter piston 52. Thus, the large-diameter piston 52 moves up and down integrally with the expansion and contraction of the piezo actuator 51. The small-diameter piston 54 has a pin-shaped lower end extending to the vicinity of the low-pressure seat 22 of the back pressure control unit 102 and abutting on the top surface of the valve 2 in the valve chamber 21. A flange is formed on the outer periphery of the intermediate portion of the small diameter piston 54, and the small diameter piston 54 is urged downward by a spring supported on the flange.
[0032]
Therefore, when the piezo actuator 51 expands and presses the large-diameter piston 52, the pressing force is transmitted to the small-diameter piston 54 via the fuel in the displacement expansion chamber 53. At this time, since the small-diameter piston 54 has a smaller diameter than the large-diameter piston 52, the amount of extension of the piezo actuator 51 is expanded and converted into the vertical displacement of the small-diameter piston 54. Thus, the two large and small pistons 52 and 54 and the displacement enlargement chamber 53 function as a hydraulic displacement enlargement mechanism.
[0033]
Next, features of the present invention will be described. With the operation of the hydraulic displacement enlargement mechanism, a part of the fuel in the displacement enlargement chamber 53 leaks from the clearance between the sliding portions of the large-diameter piston 52 and the small-diameter piston 54. Therefore, a mechanism for compensating for this is provided. In the present embodiment, the large-diameter piston 52 is hollow, and the check valve 6 that allows fuel to flow only in the direction of the displacement expansion chamber 53 is accommodated therein. . The hollow portion formed in the large-diameter piston 52 has a stepped shape, and the check valve 6 includes a plate-shaped valve body 61 disposed in a large-diameter lower chamber 63 and the valve body 61 attached upward. There is a spring 62 that is urged to abut the stepped portion. The lower chamber 63 communicates with the displacement expansion chamber 53 through a passage 64. The small-diameter upper chamber becomes a fluid chamber 71 and communicates with a space 56 as a low-pressure portion formed on the outer periphery of the large-diameter piston 52 through a throttle 72 having a predetermined opening area. The throttle 72 has a through hole having one end opened to the upper inner wall of the fluid chamber 71 and the other end opened to the outer peripheral surface of the large-diameter piston 52, and the space 56 communicates with the return passage 11 through the passage 57. Therefore, when the pressure in the displacement expansion chamber 53 decreases, the check valve 6 opens, and the fuel in the return passage 11 flows through the passage 57, the throttle 72, and the fluid chamber 71, and is replenished with fuel.
[0034]
The operation of the fuel injection valve 1 having the above configuration will be described. In a state where the piezo actuator 51 is contracted in the discharge state (the state shown in the figure), since the diameter of the low-pressure seat 22 ≧ the diameter of the sliding portion 2b, the valve is driven by the pressure of the high-pressure fuel supplied from the inlet to the high-pressure passage 12. 2 is seated on the low-pressure seat 22. In this state, when a switch of a driving device (not shown) is turned on and a voltage is applied to the piezo actuator 51, the piezo actuator 51 expands and pushes down the large-diameter piston 52, and the pressure in the displacement expansion chamber 53 increases. This pressure acts on the small diameter piston 54 downward. Then, when the pressure in the displacement expansion chamber 53 reaches the pressure at which the valve 2 starts to operate [(the downward force of the small-diameter piston 54)> (the pressure at which the upward force of the valve 2)], the small-diameter piston 54 pushes the valve 2 down. Then, the valve portion 2a of the valve 2 is separated from the low-pressure seat 22 and further displaced downward to be seated on the high-pressure seat 23. When the low-pressure seat 22 is opened, the fuel in the control chamber 4 flows into the return passage 11 through the main orifice 41, the valve chamber 21, and the spill chamber 14, so that the pressure in the control chamber 4 decreases. When the downward urging force of the nozzle needle 3 becomes lower than the upward urging force, the nozzle needle 3 is unseated and fuel injection is started.
[0035]
Next, when the piezo actuator 51 is discharged, the piezo actuator 51 contracts, the large-diameter piston 52 moves upward, the pressure in the displacement expansion chamber 53 drops, and the pushing force of the valve 2 is released. Thereby, the high-pressure seat 23 communicating with the high-pressure passage 12 is opened, and the high-pressure fuel flowing into the control chamber 4 through the passage 15, the valve chamber 21 and the main orifice 41 and the high-pressure fuel flowing through the sub-orifice 42. As a result, the pressure in the control chamber 4 increases again. Then, the needle 3 is seated and the injection ends.
[0036]
By the way, at the start of the injection, the low-pressure seat 22 is opened, and the high-pressure fuel in the valve chamber 21 and the control chamber 4 is jetted into the spill chamber 14, and the pressure in the return passage 11 pulsates due to the spill fuel. On the other hand, during the injection, the pressure in the displacement expansion chamber rises to about 10 MPa, so that the fuel in the displacement expansion chamber 53 leaks from the clearance between the sliding portions of the large-diameter piston 52 and the small-diameter piston 54. Therefore, when the piezo actuator 51 contracts at the end of the injection, the pressure in the displacement expansion chamber 53 decreases, and the valve element 61 of the check valve 6 opens to replenish the fuel in the displacement expansion chamber 53.
[0037]
At this time, in the conventional configuration, there is a problem that the operation of the check valve 6 becomes unstable due to the influence of the pressure pulsation of the return passage 11 caused by the high-pressure spill fuel. Since the throttle 72 is provided upstream, it is possible to prevent the pressure pulsation of the return passage 11 from directly acting on the check valve 6. Further, since the fluid chamber 71 having a predetermined capacity is formed between the check valve 6 and the throttle 72, the check valve 6 can be operated at a stable pressure. Therefore, the fuel filling state is stabilized and the fluctuation between cycles can be reduced, so that the injection controllability is greatly improved. Further, since the check valve 6 and the fluid chamber 71 having a predetermined capacity are accommodated in the large-diameter piston 52, the size of the apparatus does not increase.
[0038]
FIG. 2 shows a second embodiment of the present invention. In the first embodiment, the throttle 72 is provided in the side wall of the large-diameter piston 52 so that the fluid chamber 71 provided upstream of the check valve 6 communicates with the space 56 on the outer periphery of the large-diameter piston 52. However, as shown in FIG. 2, a sliding portion clearance 73 between the sliding portion of the large-diameter piston 52 and the cylinder provided on the cylinder forming member 8 can be used as a throttle. The large-diameter piston 52 has a hollow lower half and accommodates the check valve 6, and a passage 74 is formed in the upper inner wall of the fluid chamber 71 upstream of which one end is opened and the other end is opened in the sliding portion clearance 73. You. The other basic configuration is the same as that of the first embodiment, and the description is omitted.
[0039]
According to the above configuration, a fluid chamber 71 having a predetermined capacity is provided upstream of the check valve 6 and communicates with the return passage 11 through the sliding portion clearance 73 serving as a throttle, so that the fluid chamber 71 is not affected by pressure pulsation. The same effect of stably operating the check valve 6 can be obtained.
[0040]
Note that the sliding portion clearance 73 does not make the outer diameter of the large-diameter piston 52 or the inner diameter of the cylinder constant, even if the outer diameter of the large-diameter piston 52 and the inner diameter of the cylinder are constant and the opening area is constant in the axial direction. For example, the sliding portion clearance 73 on the space 56 side, that is, the return passage 11 side, is larger than the sliding portion clearance 73 on the displacement expansion chamber 53 side so that the axial opening area of the sliding portion clearance 73 changes. May be set to be large.
[0041]
FIG. 3 shows a third embodiment of the present invention. In the present embodiment, the check valve 6 is housed with the lower half of the large-diameter piston 52 hollow, and a passage 74 extending laterally from the upper inner wall of the fluid chamber 71 upstream thereof is formed. The passage 74 is configured to form a throttle 75 communicating with the space 56 on the outer periphery of the large-diameter piston 52 with a predetermined opening area in the illustrated state where the large-diameter piston 52 is at the upper end position. The other basic configuration is the same as that of the first embodiment, and the description is omitted.
[0042]
According to the above configuration, a fluid chamber 71 having a predetermined capacity is provided upstream of the check valve 6 and communicates with the return passage 11 via the throttle 75 at the end of the injection so that the check valve is not affected by the pressure pulsation. 6 can be operated stably.
[0043]
In each of the above embodiments, the valve 2 has a three-way valve structure, but a configuration in which the nozzle needle 3 is opened and closed using a two-way valve may be used. Further, in each of the above embodiments, both the main orifice 51 and the sub orifice 42 are provided, but a configuration in which the sub orifice 42 is not provided may be adopted.
[Brief description of the drawings]
FIG. 1 is an overall sectional view of a fuel injection valve according to a first embodiment of the present invention.
FIG. 2 is an overall sectional view of a fuel injection valve according to a second embodiment of the present invention.
FIG. 3 is an overall sectional view of a fuel injection valve according to a third embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 1 fuel injection valve 11 return passage 12 high-pressure passage 13 housing 14 spill chamber 2 valve 2a valve portion 2b sliding portion 21 valve chamber 22 low-pressure seat 23 high-pressure seat 26 spill chamber 3 nozzle needle 34 injection hole 4 control chamber 41 main orifice 42 sub Orifice 51 Piezo actuator 52 Large diameter piston 53 Displacement expansion chamber 54 Small diameter piston 56 Space (low pressure part)
6 Check valve 61 Valve element 62 Spring 71 Fluid chamber 72 Restrictor 73 Sliding part clearance (restrictor)
74 passage 75 throttle 8 cylinder forming member 101 nozzle section 102 back pressure control section 103 piezo drive section (drive section)

Claims (6)

A control chamber for applying pressure in the valve closing direction to the nozzle needle, a control valve for increasing and decreasing the pressure in the control chamber by opening and closing between the control chamber and the return passage, and a drive unit for driving the control valve A displacement expansion chamber in which a working fluid is filled between a large-diameter piston that slides in accordance with expansion and contraction of a piezo actuator and a small-diameter piston that abuts on the control valve and slides integrally therewith. A fuel injection valve having a check positioned between the displacement expansion chamber and the return passage, for allowing control fluid to flow only in the direction of the displacement expansion chamber and for supplementing the control fluid to the displacement expansion chamber. A fuel injection valve comprising: a valve; and a fluid chamber provided upstream of the check valve and the return passage communicated via a throttle. 2. The fuel injection valve according to claim 1, wherein the large-diameter piston is hollow and the check valve is housed therein. 2. The fuel injection valve according to claim 1, wherein the large-diameter piston is hollow and houses the check valve and the fluid chamber therein. 4. The fuel injection valve according to claim 3, wherein the throttle comprises a through-hole provided in the large-diameter piston and communicating the fluid chamber with a low-pressure portion on the outer periphery of the large-diameter piston. The throttle comprises a sliding portion clearance formed between a cylinder on which the large-diameter piston slides and an outer peripheral surface of the large-diameter piston, and a passage for communicating the fluid chamber and the throttle with the large-diameter piston. The fuel injection valve according to claim 3, further comprising: The large-diameter piston has one end open to the fluid chamber and the other end opened to the outer peripheral surface of the large-diameter piston, and communicates with the low-pressure portion on the outer periphery of the large-diameter piston when the large-diameter piston is at the upper end position. 4. The fuel injection valve according to claim 3, wherein a passage serving as the throttle is provided.

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