JP4998366B2 - solenoid valve - Google Patents

Description

  The present invention relates to an electromagnetic valve that performs hydraulic pressure control by operating a spool by movement of a plunger according to a current supplied to a coil.

  2. Description of the Related Art Conventionally, an electromagnetic valve shown in Patent Document 1 is known as an electromagnetic valve that performs hydraulic control by operating a spool by movement of a plunger according to a current supplied to a coil. This solenoid valve is configured by integrating a pilot pressure control valve with a pressure regulating valve. When the pilot hydraulic pressure supplied from the pilot pressure control valve to the pressure regulating valve is less than a predetermined value, the sub spool is biased in the pilot pressure control spool direction by the biasing force of the second spring, and the main spool is driven by the thrust by the pilot hydraulic pressure and the output hydraulic pressure. Move to a position that balances the feedback force. As a result, the output hydraulic pressure is adjusted to a control pressure proportional to the pilot hydraulic pressure.

When the pilot oil pressure exceeds a predetermined value, the sub-spool overcomes the urging force of the second spring and moves, so that the feedback oil chamber communicates with the drain port and the feedback force of the feedback oil chamber becomes 0 (zero). )become. Thereby, the output hydraulic pressure becomes equal to the supply pressure.
Thus, the hydraulic characteristic of the solenoid valve is switched to two stages by changing the feedback force according to the pilot hydraulic pressure.
JP 2001-280516 A (Pages 6 to 8, FIG. 4)

  By the way, in order to switch the hydraulic characteristics in two stages without using a sub-spool as described above, the valve sleeve is further provided with a second feedback port that opens and closes according to the movement of the plunger, and a control pressure is applied to this port. It is necessary to introduce.

  However, when the overall length of the valve sleeve is increased to provide the second feedback port, not only the mounting compatibility with the conventional solenoid valve that uses only one feedback port is maintained, but also the size of the valve sleeve increases. As a result, there is a problem that mountability is lowered. In addition, since the number of parts increases due to the addition of ports, there is a problem that the manufacturing cost increases.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electromagnetic valve capable of adjusting hydraulic characteristics in two stages without increasing the overall length.

  In order to achieve the above object, in the solenoid valve according to claim 1, the solenoid portion (20) in which the plunger (23) is magnetically attracted in accordance with the current (I) supplied to the coil (22). ), And a valve hole (72 to 74) is formed coaxially with the plunger attached to the solenoid portion, and a supply port (76) for supplying hydraulic oil to the valve hole and the operation from the valve hole. A discharge port (77) for discharging oil, an output port (75) provided between the supply port and the discharge port and outputting the hydraulic oil as a control pressure (P) from the valve hole; A valve sleeve (70) formed with a feedback port (78) for introducing a part of the hydraulic oil output from the output port into the valve hole, and slidably guided and supported by the valve hole. A pool (80) for controlling communication between the output port and the supply port and a first land portion (81) for controlling communication between the output port and the discharge port according to movement of the plunger; A solenoid valve (10) comprising: two land portions (82) and a spool formed with a feedback portion (82b, 83a, 86) having an area difference on which the control pressure introduced through the feedback port acts The spool is switched from a state in which the control pressure is introduced into the feedback unit to a state in which the introduction is blocked while the spool moves in the anti-plunger direction, and the control pressure is applied. The area of the non-plunger side pressure receiving surface (81a) of the first land portion is larger than the area of the plunger side pressure receiving surface (82a) of the second land portion. And technical features to be formed to be larger.

  In the first aspect of the invention, the spool that is slidably guided and supported by the valve hole of the valve sleeve is configured to control communication between the output port and the discharge port in accordance with the movement of the plunger in the valve sleeve direction. A land portion, a second land portion for controlling communication between the output port and the supply port, and a feedback portion having an area difference on which a control pressure introduced via the feedback port acts are formed. The spool is formed so as to switch from a state in which the control pressure is introduced into the feedback portion while the spool is moved in the anti-plunger direction to a state in which the introduction is blocked. In addition, the spool is formed such that the area of the counter-plunger side pressure receiving surface of the first land portion on which the control pressure acts is larger than the area of the plunger side pressure receiving surface of the second land portion.

  When the control pressure is introduced into the feedback unit because the current supplied to the coil is low and the spool has not moved to the predetermined position, the feedback force (hereinafter referred to as the feedback force) corresponding to the area difference is applied to the feedback unit. (Also referred to as first feedback force) acts. On the other hand, when the current supplied to the coil increases and the spool moves beyond the predetermined position in the anti-plunger direction, the introduction of the control pressure to the feedback unit is cut off, and the first described above. Feedback power disappears.

  When the spool moves in the direction opposite to the plunger in accordance with the current supplied to the coil, the pressure corresponding to the control pressure is used regardless of the communication state between the output port and the discharge port and the communication state between the output port and the supply port. Acts on both the non-plunger side pressure receiving surface of the first land portion and the plunger side pressure receiving surface of the second land portion. At this time, since the area of the counter plunger side pressure receiving surface is formed to be larger than the area of the plunger side pressure receiving surface, a feedback force (hereinafter referred to as a second pressure force) is applied so as to press the first land portion in the plunger direction. (Also referred to as feedback force).

  As described above, when the current supplied to the coil is low and the spool has not moved to the predetermined position, both the first feedback force and the second feedback force act, and the current supplied to the coil is high. When the valve moves beyond the predetermined position, only the second feedback force acts, so the output characteristic (hydraulic characteristic) of the control pressure output according to the current supplied to the coil is adjusted in two stages. be able to.

In particular, in a conventional solenoid valve having a feedback portion, the hydraulic characteristics can be increased in two stages by simply making the area of the counter-plunger side pressure receiving surface of the first land portion larger than the area of the plunger side pressure receiving surface of the second land portion. Therefore, the mounting compatibility with the conventional solenoid valve can be maintained without increasing the overall length of the valve sleeve.
Therefore, the hydraulic characteristics of the solenoid valve can be adjusted in two stages without increasing the overall length.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing a schematic configuration of a solenoid valve 10 according to the present embodiment. Here, in FIG. 1, the upper stage shows a non-excitation state, and the lower stage shows a maximum control pressure output state (maximum stroke state). 2 is an enlarged cross-sectional view showing a fitting relationship between the valve sleeve 70 and the spool 80 of FIG.

  For example, the solenoid valve 10 controls hydraulic oil output in an oil pan of an automatic transmission for a vehicle to realize hydraulic control. As shown in FIG. 1, as shown in FIG. The spool portion 60 is provided at one end. The solenoid unit 20 mainly includes a stator core 21, a coil 22, a plunger 23, and the like, and the spool unit 60 includes a valve sleeve 70, a spool 80, and the like.

  The stator core 21 includes a yoke part 30 and a core part 40 made of a magnetic material. The yoke portion 30 includes a substantially disc-shaped bottom portion 31, an outer cylindrical portion 32 protruding in a cylindrical shape from the outer peripheral edge of the bottom portion 31, and a cylindrical shape coaxial with the outer cylindrical portion 32 from a substantially intermediate portion in the radial direction of the bottom portion 31. It is comprised from the inner cylinder part 33 which protrudes in a shape. Note that the protruding length of the inner cylinder portion 33 from the bottom portion 31 is shorter than the protruding length of the outer cylinder portion 32 from the bottom portion 31.

  The core portion 40 includes an annular flange portion 41 and a cylindrical portion 42 that protrudes coaxially from the center of the flange portion 41. A suction part 43 that plays a role of exerting a magnetic attraction force with respect to the plunger 23 is provided at the projecting side end of the cylindrical part 42. The suction part 43 has a required attraction force characteristic and the like. Accordingly, the tapered portion 43a is formed to have a predetermined gradient.

  The core portion 40 includes a first inner peripheral hole 44 constituting an inner peripheral side of the suction portion 43, a second inner peripheral hole 45 having a smaller diameter than the first inner peripheral hole 44, A third inner peripheral hole 46 having a diameter smaller than that of the second inner peripheral hole 45 and a fourth inner peripheral hole 47 having a diameter larger than that of the third inner peripheral hole 46 are formed coaxially. Here, the second inner peripheral hole 45 and the end surface 48 connecting the second inner peripheral hole 45 and the third inner peripheral hole 46 constitute an annular stepped portion 49.

  As shown in FIG. 1, the yoke portion 30 and the core portion 40 are configured such that the outer peripheral side end portion of the flange portion 41 is fitted to a step portion 32 a provided in the vicinity of the opening end of the outer cylinder portion 32 and the inner cylinder portion 33. The suction part 43 of the cylindrical part 42 is arranged coaxially with each other in a state where it is magnetically separated by a magnetic resistance part (air gap) 51. At that time, the coil 22 wound around the bobbin is disposed so as to be surrounded by the outer cylinder part 32, the bottom part 31 and the inner cylinder part 33 of the yoke part 30, and the cylindrical part 42 and the flange part 41 of the core part 40. Yes.

  In the plunger 23, a plunger main body 23a made of a magnetic material and a projecting portion 23b that protrudes coaxially from a spool side end surface of the plunger main body 23a into a small-diameter cylindrical shape are integrally formed, and a center hole 23c is formed in the plunger main body 23a. And it is formed so that the protrusion part 23b may be penetrated.

  The plunger body 23 a is formed so that its outer diameter is slightly smaller than the inner diameter of the first inner peripheral hole 44 of the core portion 40. Further, the protruding portion 23b is formed so that a predetermined air gap is interposed between the outer peripheral surface and the second inner peripheral hole 45 of the core portion 40 when entering the annular step portion 49 as described later. Yes.

  A shaft 24 formed of a non-magnetic material is coaxially fixed in the center hole 23c of the plunger 23 so as to penetrate the plunger 23 by a part of the press-fitting. The portion of the shaft 24 protruding from the plunger 23 is formed so that its outer diameter is smaller than the inner diameter of the third inner peripheral hole 46 of the core portion 40.

  The shaft 24 projecting from the plunger 23 toward the core portion is provided with a stopper 25 for contacting the end surface 48 of the annular step portion 49 of the core portion 40 to restrict the movement of the plunger 23 toward the core portion. .

  The plunger main body 23 a is slidably supported by the inner peripheral surface of the inner cylindrical portion 33 in the yoke portion 30 of the stator core 21 via the bush 52 on the outer peripheral surface thereof. Further, the shaft 24 is slidably supported by a fourth inner peripheral hole 47 of the core portion 40 of the stator core 21 via a bush 53 on the outer peripheral surface of the tip portion thereof. As a result, the plunger 23 and the shaft 24 are coaxially and slidably supported in the stator core 21.

  By configuring the solenoid unit 20 in this way, a magnetic circuit is configured with the stator core 21 and the plunger 23 in accordance with the current supplied to the coil 22. When magnetic flux flows through the magnetic circuit, the plunger 23 and the shaft 24 are coupled to the core of the protruding portion 23b in addition to the magnetic attractive force generated between the vicinity of the outer edge of the core side end surface of the plunger main body 23a and the attracting portion 43 of the core portion 40. Due to the magnetic attractive force generated between the vicinity of the outer edge of the side end surface and the vicinity of the plunger side edge of the annular stepped portion 49 of the core portion 40, it moves in the axial direction (spool direction) close to the core portion 40.

  A valve sleeve 70 for slidably fitting the spool 80 is disposed on the outer surface of the flange portion 41 located on the opening end side of the outer tube portion 32. And the solenoid part 20 and the spool part 60 are crimped by crimping the opening side cylindrical end part 32b of the outer cylinder part 32 in a state where the flange part 71 and the flange part 41 formed on the valve sleeve 70 are joined. Are joined together.

  As shown in FIGS. 1 and 2, the valve sleeve 70 is formed with a first valve hole 72, a second valve hole 73, and a third valve hole 74 having different diameters and connected to the third valve hole 74. A spring accommodating hole 74a is formed. Each of these valve holes 72 to 74 and the spring accommodating hole 74 a are formed so as to extend coaxially with the stator core 21 and the plunger 23.

  The spool 80 has a first land portion 81 that can be fitted in the first valve hole 72, a second land portion 82 that can be fitted in the second valve hole 73, and a second land portion 82 that can be fitted in the third valve hole 74. Three land portions 83 are provided.

  The first land portion 81 and the second land portion 82 are provided apart from each other by a predetermined amount in the axial direction, and are connected to each other by a small diameter portion 84. An annular groove 72a is formed in the connecting portion of the first valve hole 72 and the second valve hole 73 corresponding to the small diameter portion 84, and an output for outputting hydraulic oil as a control pressure to the annular groove 72a. Port 75 is in communication.

  As shown in FIG. 2, the non-plunger side pressure receiving surface 81a of the first land portion 81 and the plunger side pressure receiving surface 82a of the second land portion 82 are formed to face each other so that the control pressure acts together. . Here, the non-plunger side pressure receiving surface 81a is formed so that the area thereof is larger than the area of the plunger side pressure receiving surface 82a.

  A supply port 76 for supplying hydraulic oil to the second valve hole 73 is formed in the valve sleeve 70, and the opening degree of the supply port 76 is controlled by the movement of the second land portion 82 in the axial direction. It is configured to be. Further, the valve sleeve 70 is formed with a discharge port 77 for discharging hydraulic oil from the first valve hole 72, and the opening degree of the discharge port 77 moves in the axial direction of the first land portion 81. It is comprised so that it may be controlled by.

  As shown in FIG. 2, an annular groove 73a is formed in the vicinity of the third valve hole of the second valve hole 73, and the portion of the second valve hole 73 closer to the third valve hole than the annular groove 73a is In particular, it is also referred to as one side end portion 73b. A feedback port 78 is formed in the annular groove 73a, and this feedback port 78 communicates with the output port 75 via a communication path (not shown).

  The second land portion 82 and the third land portion 83 are provided apart from each other by a predetermined amount in the axial direction, and are connected to each other by a small diameter portion 85. The non-plunger side pressure receiving surface 82b of the second land portion 82 and the plunger side pressure receiving surface 83a of the third land portion 83 are opposed to each other so that a feedback pressure corresponding to a control pressure introduced through the feedback port 78 acts together. Is formed.

  Here, the non-plunger side pressure receiving surface 82b is formed so that the area thereof is larger than the area of the plunger side pressure receiving surface 83a (see FIG. 2). The portion having the non-plunger side pressure receiving surface 82b and the plunger side pressure receiving surface 83a (hereinafter also referred to as the feedback portion 86) corresponds to “a feedback portion having an area difference on which the control pressure acts” described in the claims. To do.

  A control pressure is introduced to the feedback portion 86 formed in this way via the feedback port 78 when the second land portion 82 is not fitted to the one end portion 73 b of the second valve hole 73. When the second land portion 82 is fitted to the one end portion 73 b of the second valve hole 73, the introduction of the control pressure to the feedback portion 86 via the feedback port 78 is blocked.

  The valve sleeve 70 is formed with a drain port 79 communicating with the spring accommodating hole 74a. In addition, a shaft portion 87 that abuts against the spool-side end surface of the shaft 24 protrudes from one end of the spool 80.

  The open end of the spring accommodating hole 74 a is closed by a plug 90 that is screwed into a screw hole formed on the inner peripheral surface thereof, and a spring 91 is provided between the plug 90 and the spool 80. The spool 80 is pressed toward the plunger 23 by the urging force of the spring 91, whereby the shaft 24 press-fitted into the plunger 23 via the shaft portion 87 of the spool 80 abuts against the bottom portion 31 of the normal yoke portion 30. It is held in the initial position. At the initial position of the plunger 23, the spool side edge of the plunger 23 is disposed so as to substantially coincide with the end of the suction portion 43 of the core portion 40 in the axial direction (see the upper part of FIG. 1).

  The operation of the electromagnetic valve 10 according to this embodiment configured as described above will be described with reference to FIG. FIG. 3 is a graph showing the relationship between the current I supplied to the coil 22 and the control pressure P output from the output port 75.

  When the coil 22 is in a non-excited state, the spool 80 presses the plunger 23 in the anti-spool direction by the urging force of the spring 91 and holds the plunger 23 at an initial position where it abuts against the bottom 31 of the yoke portion. In this non-excited state, the output port 75 is disconnected from the supply port 76 and is also connected to the discharge port 77, whereby the control pressure P output from the output port 75 is maintained at approximately 0 pa. Has been.

  On the other hand, when the coil 22 is excited by supplying the current I, a magnetic flux flows through a magnetic circuit constituted by the stator core 21 and the plunger 23. Thereby, between the core side end surface outer edge vicinity of the plunger main body 23a and the suction part 43 of the core part 40, and the core side end surface outer edge vicinity of the protrusion part 23b, and the plunger side edge vicinity of the annular step part 49 of the core part 40 In between, magnetic attraction force is generated.

  By these magnetic attraction forces, the plunger 23 and the shaft 24 are attracted toward the attracting portion, and the spool 80 moves in the anti-plunger direction. By this movement, the second land portion 82 starts to open the supply port 76 and the first land portion 81 starts to limit the opening area of the discharge port 77, so that the control pressure P of the output port 75 gradually increases.

At this time, hydraulic oil corresponding to the control pressure P output from the output port 75 is introduced into the feedback unit 86 via the communication path and the feedback port 78. Thus, the feedback force corresponding to the area difference between the counter-plunger-side pressure receiving surface 82b and the plunger-side pressure receiving surface 83a (hereinafter, also referred to as a first feedback force F ₁₎ is, the plunger 23 urging force in the same direction of the spring 91 Works.

Further, a pressure corresponding to the control pressure P acts on both the non-plunger side pressure receiving surface 81 a of the first land portion 81 and the plunger side pressure receiving surface 82 a of the second land portion 82. The non-plunger side pressure receiving surface 81a is formed so that the area thereof is larger than the area of the plunger side pressure receiving surface 82a. Therefore, a feedback force (hereinafter referred to as a second pressure force) is applied to press the first land portion 81 in the plunger direction. Feedback force F ₂ ) acts on the plunger 23 in the same direction as the biasing force of the spring 91.

As a result, the spool 80 includes each of the above magnetic attraction force generated in response to the current I supplied to the coil 22, the biasing force of the spring 91, the first feedback force F ₁ and the second feedback force F ₂ and balanced Move to the anti-plunger direction to the position. At this time, the control pressure P which is output from the output port 75 increases in proportion to the current I supplied to the coil 22 (see P ₁ in FIG. 3).

  When the magnetic attraction force increases due to the increase in the current I supplied to the coil 22, the spool 80 further moves in the anti-plunger direction. When the second land portion 82 is fitted to the one side end portion 73b of the second valve hole 73 by the movement of the spool 80, the introduction of the control pressure P to the feedback portion 86 is blocked.

Therefore, since the first feedback force F ₁ disappears, the spool 80 without substantially increasing the current I is further moved in the counter-plunger direction. As a result, when the opening degree of the supply port 76 by the second land portion 82 is maximized and the discharge port 77 is fully closed by the first land portion 81, the control pressure P rapidly increases to the maximum control pressure Pm (FIG. reference _{P 2} of 3).

As described above, the relationship between the current I supplied to the coil 22 and the control pressure P output from the output port 75 varies depending on whether or not the first feedback force F ₁ is applied to the spool 80. That is, the hydraulic characteristic of the electromagnetic valve 10 can be adjusted in two stages.

In particular, during the movement of the spool 80 in the anti-plunger direction, the introduction of the control pressure P to the feedback portion 86 is cut off and the first feedback force F ₁ is lost, so the first feedback force F ₁ is lost. The maximum control pressure Pm can be output at a lower current than in the case where the control is not performed (see FIG. 3).

  As described above, in the solenoid valve 10 according to the first embodiment, the spool 80 slidably guided and supported by the valve holes 72 to 74 of the valve sleeve 70 has the plunger 23 in the valve sleeve direction. Via a feedback port 78, a first land portion 81 that controls communication between the output port 75 and the discharge port 77, a second land portion 82 that controls communication between the output port 75 and the supply port 76, and a feedback port 78. Thus, a feedback portion 86 having an area difference on which the control pressure P introduced is applied. The spool 80 is formed so as to switch from a state in which the control pressure P is introduced into the feedback portion 86 while the spool 80 moves in the anti-plunger direction to a state in which the introduction is blocked. The spool 80 is formed so that the area of the counter-plunger side pressure receiving surface 81a of the first land portion 81 on which the control pressure P acts is larger than the area of the plunger side pressure receiving surface 82a of the second land portion 82. Yes.

Since the current I supplied to the coil 22 is low and the spool 80 is not moved to a predetermined position, specifically, the position where the second land portion 82 is fitted to the one end 73 b of the second valve hole 73. When the control pressure P is introduced into the feedback unit 86, the first feedback force F ₁ corresponding to the area difference acts on the feedback unit 86. On the other hand, when the current I supplied to the coil 22 increases and the spool 80 moves in the anti-plunger direction beyond the predetermined position, switching to the state where the introduction of the control pressure to the feedback unit 86 is interrupted, first feedback force _{F 1} is lost.

Further, when the spool 80 moves in the anti-plunger direction according to the current I supplied to the coil 22, regardless of the communication state between the output port 75 and the discharge port 77 and the communication state between the output port 75 and the supply port 76. The pressure corresponding to the control pressure P acts on both the non-plunger side pressure receiving surface 81a of the first land portion 81 and the plunger side pressure receiving surface 82a of the second land portion 82. At this time, the counter-plunger-side pressure receiving surface 81a is formed so that the area thereof is larger than the area of the plunger-side pressure receiving surface 82a, so that the second feedback force is applied so as to press the first land portion 81 in the plunger direction. F ₂ is acting.

Thus, when the current I supplied to the coil 22 is low and the spool 80 has not moved to the position where the spool 80 is fitted to the one end 73b of the second valve hole 73 at the second land portion 82, The first feedback force F ₁ and the second feedback force F ₂ act together, the current I supplied to the coil 22 is high, and the spool 80 has a second land portion 82 at one side end 73 b of the second valve hole 73. when moving beyond the position for fitting the, only the second feedback force F ₂ is applied, the output characteristic of the control pressure P which is output in response to the current I supplied to the coil 22 (the hydraulic pressure characteristic) It can be adjusted in two stages.

In particular, in the conventional solenoid valve in which the feedback portion 86 is formed, the area of the non-plunger side pressure receiving surface 81a of the first land portion 81 is simply made larger than the area of the plunger side pressure receiving surface 82a of the second land portion 82. Since the hydraulic characteristics are adjusted in two stages, the mounting compatibility with the conventional solenoid valve can be maintained without increasing the overall length of the valve sleeve 70.
Therefore, the hydraulic characteristics of the electromagnetic valve 10 can be adjusted in two stages without increasing the overall length.

It is sectional drawing which shows the structure outline | summary of the solenoid valve which concerns on this embodiment. It is an expanded sectional view which shows the fitting relationship of the valve sleeve and spool of FIG. It is a graph which shows the relationship between the electric current supplied to a coil, and the control pressure output from an output port.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Solenoid valve 23 ... Plunger 60 ... Spool part 70 ... Valve sleeve 72 ... 1st valve hole (valve hole)
73 ... Second valve hole (valve hole)
74 ... Third valve hole (valve hole)
75 ... Output port 76 ... Supply port 77 ... Discharge port 78 ... Feedback port 80 ... Spool 81 ... First land portion 81a ... Non-plunger side pressure receiving surface 82 ... Second land portion 82a ... Plunger side pressure receiving surface 82b ... Anti-plunger side pressure receiving surface 83 ... third land portions 83a ... plunger side pressure receiving surface 86 ... feedback portion F 1 _... first feedback force F 2 _... second feedback force I ... current P ... control pressure

Claims (1)

A solenoid part in which the plunger is magnetically attracted according to the current supplied to the coil;
A valve hole is formed coaxially with the plunger attached to the solenoid portion, and a supply port for supplying hydraulic oil to the valve hole, a discharge port for discharging the hydraulic oil from the valve hole, and the supply An output port provided between the port and the discharge port for outputting the hydraulic oil as a control pressure from the valve hole and a part of the hydraulic oil output from the output port are introduced into the valve hole. A valve sleeve formed with a feedback port for,
A spool that is slidably guided and supported in the valve hole, and that controls communication between the output port and the discharge port according to the movement of the plunger, between the first land portion, the output port, and the supply port. A spool formed with a second land portion for controlling communication of the feedback portion and a feedback portion having an area difference on which the control pressure introduced through the feedback port acts;
A solenoid valve comprising:
The spool is switched from a state in which the control pressure is introduced into the feedback portion while the spool is moved in the anti-plunger direction to a state in which the introduction is cut off, and the first land on which the control pressure acts. An electromagnetic valve characterized in that the area of the counter-plunger side pressure receiving surface of the portion is formed to be larger than the area of the plunger side pressure receiving surface of the second land portion.

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