วาล์วควบคุมการไหล

Abstract

แก้ไขบทสรุป30 / 05 / 59 ภายในตัวเรือนวาล์ว(2)ที่จัดให้มีพร้อมกับเส้นทางการไหลเส้นทางแรก(10)และเส้นทาง การไหลเส้นทางที่สอง(11)ซึ่งต่อขนานกับช่องแรก(5)และช่องที่สอง(6),จัดให้มีช่องของวาล์วเข็ม (22)ซึ่งเปิด / ปิดรูของวาล์วบังคับของเหลว(21)ในเส้นทางการไหลเส้นทางแรก(10),วาล์วกันย้อน (13)ซึ่งเปิด / ปิดเส้นทางการไหลเส้นทางที่สอง(11)และลูกสูบ(28)ซึ่งกระทำการควบคุมการเปิด / ปิด ของช่องวาล์วเข็ม  (22)  ผ่านทางอันตรกิริยาของความดันของของไหลที่ถูกใส่เข้าไปในห้อง แรงดัน(38)และแรงสปริงของสปริงกด(39)ช่องของวาล์วเข็ม(22)ถูกสร้างขึ้นที่ปลายสุดของก้าน (23)ที่ถูกต่อเข้ากับลูกสูบ(28)ภายในก้าน(23)และช่องของวาล์วเข็ม(22)สร้างรูนำไฟฟ้าขึ้นมา(40) ที่ต่อรูของวาล์วบังคับของเหลว(21)และห้องแรงดัน(38)เข้าด้วยกัน ---------------------------------------------------------------------------           ภายในตัวเรือนวาล์ว(2)ที่จัดให้มีพร้อมกับเส้นทางการไหลเส้นทางแรก(10)และ เส้นทางการไหลเส้นทางที่สอง(11)ซึ่งต่อขนานกับช่องแรก(5)และช่องที่สอง(6),จัดให้มี ช่องของวาล์วเข็ม(22)ซึ่งเปิด / ปิดรูของวาลล์วบังคับของเหลว(21)ในเส้นทางการไหลเส้นทาง แรก(10),วาล์วกันย้อน(13)ซึ่งเปิด / ปิดเส้นทางการไหลเส้นทางที่สอง(11)และลูกสูบ(28)ซึ่ง กระทำการควบคุมการเปิด / ปิดของช่องของวาล์วเข็ม(22)ผ่านทางอันตรกิริยาของความดันของ ของไหลที่ถูกใส่เข้าไปในห้องแรงดัน(38)และแรงสปิงของสปิงกด(39)ช่องของวาล์วเข็ม (22)ถูกสร้างขึ้นที่ปลายสุดของก้าน(23)ที่ถูกต่อเข้ากับลูกสูบ(28)ภายในก้าน(23)และช่อง ของวาล์วเข็ม(22)สร้างรูนำไฟฟ้าขึ้นมา(40)ที่ต่อรูของวาล์วบังคับของเหลว(21)และห้อง แรงดัน(38)เข้าด้วยกัน;

Description

The present invention relates to a fluid control valve that controls the flow rate, pressure, etc., of pressurized fluid supplied to or discharged from an actuator such as a fluid pressure cylinder. Fluid control valves that control the flow rate and pressure of the pressurized fluid supplied to or discharged from an actuator, such as a fluid pressure cylinder, when driving the actuator, are known to have various configurations, as disclosed in, for example, Patent Document 1 and Patent Document 2. These types of fluid control valves are typically configured to have various functions depending on the intended use. These include meter-in control, which limits the flow rate during supply and leaves the flow rate unrestricted during exhaust; meter-out control, which leaves the flow rate unrestricted during supply and limits the flow rate during exhaust; and rapid exhaust during exhaust to prevent delays in operation. However, conventional fluid control valves, which individually incorporate needle valves, flow control valves, or check valves inside the valve housing, tend to be complex and large, making them inconvenient to adjust and handle, and thus impractical to use. Therefore, there has been a desire for the emergence of smaller, more user-friendly fluid control valves. Japanese Patent Publication No. 2000-320503, Japanese Patent Publication No. 2000-322128 The object of the present invention is to provide a fluid control valve with a rational design structure that is simpler and more compact by incorporating needle valves, flow control valves, check valves, etc., into the valve housing in a rational combination and arrangement. To achieve the above object, the fluid control valve of the present invention includes a first port into which a pressure fluid is input and a second port from which the pressure fluid is output. Inside the valve housing, there are a first flow path and a second flow path that connect the first port and the second port in parallel, a needle valve portion that opens and closes the first flow path, a check valve portion that opens and closes the second flow path, and an opening / closing control portion that controls the opening and closing of the needle valve portion. The needle valve portion, the opening / closing control portion, and the check valve portion are coaxially arranged along one axis. The needle valve portion has a throttle hole that forms a part of the first flow path and a needle valve body that opens and closes the throttle hole. The needle valve body is formed at the tip of a rod that extends linearly along the axis and is displaceable in the axial direction together with the rod. The check valve portion is configured to block the flow of fluid from the first port toward the second port and allow the flow of fluid from the second port toward the first port. The opening / closing control portion has a piston provided on the rod, a pressure chamber formed on one side of the piston, and a compression spring provided on the other side of the piston for setting the operating pressure of the piston. Inside the rod and the needle valve body, a through hole that connects the throttle hole and the pressure chamber is formed. One end of the through hole opens at the tip of the needle valve body, and the other end of the through hole communicates with the pressure chamber. In the present invention, the needle valve body occupies an initial position that restrictively opens the throttle hole while the fluid pressure in the second port is lower than the set pressure by the compression spring. When the fluid pressure in the second port becomes higher than the set pressure by the compression spring, the needle valve body is configured to displace together with the piston and the rod to fully open or fully close the throttle hole. According to a specific configuration aspect of the present invention, a partition wall that partitions the needle valve portion and the opening / closing control portion is formed in the valve housing. The rod penetrates through the partition wall in an airtight and slidable manner via a sealing member. The needle valve body is integrally formed on the tip side portion of the rod beyond the sealing member, and the piston is provided on the rear end side portion of the rod beyond the sealing member. In this case, it is desirable that the diameter of the sliding portion of the rod that slidably moves in an airtight manner inside the partition wall is larger than the diameter of the needle valve body. Preferably in the present invention, there is an opening degree adjustment mechanism for adjusting the initial opening degree of the needle valve portion. According to one specific configuration of the present invention, the opening degree adjustment mechanism is formed by connecting the rod and the piston so as to be displaceable relative to each other in the axial direction by screw coupling, and the initial opening degree is adjusted by adjusting the position of the rod relative to the piston, thereby displacing the needle valve body. According to another specific configuration of the present invention, the opening degree adjustment mechanism includes a handle for rotating the rod and a cam mechanism for displacing the rod in the axial direction by the rotation of the rod. The cam mechanism preferably has a helical cam surface formed in the valve housing so as to surround the rod and a movable body formed on the rod that contacts the cam surface, and the initial opening degree is adjusted by rotating the rod with the handle and moving the movable body along the cam surface, thereby displacing the rod and the needle valve body in the axial direction. According to yet another specific configuration of the present invention, the opening degree adjustment mechanism comprises an adjustment rod connected to the rod and an adjustment member that moves the adjustment rod forward and backward, wherein the adjustment member is screw-connected to the valve housing so as to be able to move forward and backward, and the initial opening degree is adjusted by moving the rod forward and backward via the adjustment rod using the adjustment member. Furthermore, in the present invention, the opening / closing control unit is configured such that the compression spring biases the piston in the direction that closes the needle valve body and the fluid pressure introduced into the pressure chamber presses the piston in the direction that opens the needle valve body, or the opening / closing control unit is configured such that the compression spring biases the piston in the direction that opens the needle valve body and the fluid pressure introduced into the pressure chamber presses the piston in the direction that closes the needle valve body. According to the present invention, by combining the functions of a needle valve and a flow control valve in a known fluid control valve and incorporating them coaxially within the valve housing, it is possible to obtain a fluid control valve with a simpler structure, smaller size, and a rational design compared to known fluid control valves. This is a cross-sectional view of the initial state showing the first embodiment of the fluid control valve according to the present invention. This is an enlarged view of the main part of Figure 1. This is a plan view of Figure 1. This is a cross-sectional view showing the fully open state of the fluid control valve of Figure 1. This is a circuit diagram showing an example of a control circuit that controls a fluid pressure cylinder using the fluid control valve of Figure 1. This is a cross-sectional view of the initial state showing the second embodiment of the fluid control valve according to the present invention. This is a cross-sectional view of the fluid control valve of Figure 6 in the fully closed state. This is a circuit diagram showing an example of a control circuit that controls a fluid pressure cylinder using the fluid control valve of Figure 6. This is a cross-sectional view showing the initial opening of the needle valve portion of the third embodiment of the fluid control valve according to the present invention, when the initial opening of the needle valve portion is adjusted to the minimum opening. This is a partially broken perspective view showing the spiral cam surface by breaking the valve housing. This is a perspective view of the needle valve body. This is a cross-sectional view of the needle valve portion of the fluid control valve of Figure 9 when the initial opening of the needle valve portion is adjusted to the maximum opening. Figures 1-4 show a first embodiment of the fluid control valve according to the present invention, in which the fluid control valve 1A is a meter-in control type fluid control valve that controls the flow rate of pressurized fluid (e.g., compressed air) supplied to a fluid pressure actuator such as a fluid pressure cylinder. The fluid control valve 1A has a valve housing 2 having a first port into which pressurized fluid is input and a second port out which pressurized fluid is output. The valve housing 2 consists of a cylindrical main block 3 having the second port 6 on the first end 3a side, which is one end in the direction of the axis L of the central hole, and a port block 4 having the first port 5 at its tip. The fitting portion 3c of the main block 3 is fitted into the cylindrical portion 4a formed at the rear end of the port block 4 so as to be rotatable relative to the axis L, and O-rings 7 are interposed between the inner circumferential surfaces of the upper and lower ends of the cylindrical portion 4a and the outer circumferential surfaces of the upper and lower ends of the fitting portion 3c, respectively. A simple connection type pipe fitting 8 is attached to the first port 5. When one end of a pipe connected to a fluid pressure cylinder or the like is inserted into the pipe fitting 8, a plurality of locking pieces 8a bite into the outer circumference of the pipe and lock it in place, preventing the pipe from coming loose. When the release bush 8b is pushed into the pipe fitting 8, the tip of the release bush 8b spreads the locking pieces 8a outward, separating them from the pipe, thereby allowing the pipe to be removed. Inside the main block 3, there is a first flow path 10 and a second flow path 11 connecting the first port 5 and the second port 6 in parallel, a needle valve section 12 for opening and closing the first flow path 10, a check valve section 13 for opening and closing the second flow path 11, and an opening / closing control section 14 for controlling the opening and closing of the needle valve section 12. The needle valve section 12, the check valve section 13, the opening / closing control section 14, and the second port 6 are arranged coaxially along one of the axes L. To form the first flow path 10 and the second flow path 11, a stepped cylindrical member 15 with a diameter that changes in multiple stages is inserted into the first end 3a side of the main block 3, with the smaller diameter side facing inward into the main block 3. The second port 6 is formed at the outer end (lower end in the figure) of the cylindrical member 15. The first flow path 10 is formed inside the cylindrical member 15, with one end leading to the second port 6. The second flow path 11 is formed between the outer circumference of the cylindrical member 15 and the inner circumference of the main block 3. One end of the second flow path 11 and the second port 6 are in communication through a plurality of communication holes 16 formed on the side surface of the cylindrical member 15. Furthermore, the first flow path 10 and the second flow path 11 merge within the valve chamber 17 where the inner end (upper end in the figure) of the cylindrical member 15 is located to form a single unified flow path, which then communicates with the first port 5 through the first flow path hole 18 formed on the side surface of the main block 3, the annular flow path 19 formed between the inner circumference of the cylindrical portion 4a and the outer circumference of the fitting portion 3c, and the second flow path hole 20 formed in the port block 4. Therefore, the unified flow path is both a part of the first flow path 10 and a part of the second flow path 11. A throttling hole 21 is formed inside the smallest diameter portion 15a on the inner end side of the cylindrical member 15, which constitutes part of the needle valve portion 12. This throttling hole 21 forms part of the first flow path 10, and a conical valve head 22a that gradually tapers to the tip of the needle valve body 22 is fitted into this throttling hole 21 from the valve chamber 17 side, and the needle valve portion 12 is formed by the needle valve body 22 and the throttling hole 21. The needle valve body 22 is formed at the tip of a cylindrical rod 23, and the rear end of the rod 23 extends linearly along the axis L to the opening / closing control unit 14. The needle valve body 22 and the rod 23 are integrally formed from a single rod-shaped metal material. The inner end (upper end in the figure) of the small-diameter portion 15a of the cylindrical member 15 is bent outward in the diametrical direction of the small-diameter portion 15a, and then bent back inward in the diametrical direction of the small-diameter portion 15a, with its inner diameter end 15b facing the conical portion 22b connected to the upper end of the valve head 22a of the needle valve body 22. The check valve portion 13 is formed of a lip-type sealing member having a V-shaped cross-section, and is positioned to surround the outer circumference of the small-diameter portion 15a of the cylindrical member 15, with the lip 13a facing in a direction that blocks the flow of fluid from the first port 5 to the second port 6, while allowing the flow of fluid from the second port 6 to the first port 5. A partition wall 25 is formed in the main block 3, separating the needle valve section 12 from the opening / closing control unit 14. The rod 23 passes through the interior of a sliding hole 26 formed in the partition wall 25 in an airtight and slidable manner via a sealing member 27 attached to the outer circumference of the rod 23. The needle valve body 22 is formed on the portion of the rod 23 located on the needle valve section 12 side, beyond the sealing member 27, and a piston 28 is attached to the portion located on the opening / closing control unit 14 side, beyond the sealing member 27. The sealing member 27 is a lip-type sealing member and is arranged to block the flow of pressurized fluid from the valve chamber 17 toward the opening / closing control unit 14, while allowing the flow of pressurized fluid from the opening / closing control unit 14 toward the valve chamber 17. The diameter of the portion of the rod 23 that slides airtightly within the sliding hole 26 (sliding portion) 23a is larger than the diameter of the needle valve body 22, that is, the diameter of the cylindrical portion 22d connected to the sliding portion 23a via a conical portion 22c, and the diameter of the valve head 22a connected to the cylindrical portion 22d via a conical portion 22b. Due to this difference in diameter between the sliding portion 23a and the needle valve body 22, when fluid pressure acts on the needle valve body 22, an upward force in the diagram, i.e., a force in the valve-opening direction, acts on the needle valve body 22. The piston 28 is slidably housed in a piston chamber 29 formed inside the second end 3b side of the main block 3 via a sealing member 30 attached to the outer circumference of the piston 28, and is connected to the rod 23 by a screw connection. That is, by screwing the male screw portion 23b formed on a part of the rod 23 into the screw hole 31a formed on a part of the central hole 31 of the piston 28, the piston 28 and the rod 23 are screw-connected to each other, and by rotating the rod 23 and adjusting the position of the rod 23 relative to the piston 28 in the axial direction L, the degree to which the valve head 22a of the needle valve body 22 enters the throttling hole 21, that is, the initial opening degree of the throttling hole 21 by the needle valve body 22 can be arbitrarily adjusted. Therefore, the above configuration in which the piston 28 and the rod 23 are screw-connected can be said to be an opening degree adjustment mechanism 32 for adjusting the initial opening degree of the throttling hole 21. Reference numeral 23c in the figure indicates an operating groove for locking the tip of a screwdriver when rotating the rod 23, and reference numeral 33 indicates a sealing member that seals the space between the outer circumference of the rod 23 and the inner circumference of the piston 28. An end cap 34 is fixed to the end of the piston chamber 29 on the second end 3b side. As can be seen in Figure 3, the end cap 34 has a non-circular guide hole 35 with a pair of parallel flat portions 35a on a part of its inner circumference. A non-circular guide portion 36, which has the same outer shape as the guide hole 35, is fitted into the guide hole 35 at the upper end of the piston 28, and the upper end of the rod 23 is exposed to the outside of the end cap 34 within this guide portion 36. The guide portion 36 and the guide hole 35 are for preventing the piston 28 from rotating when the rod 23 is rotated, and constitute a rotation prevention mechanism for the piston 28. Within the piston chamber 29, a pressure chamber 38 for introducing pressurized fluid is formed between the first surface (lower surface) 28a of the piston 28 and the partition wall 25, and a compression spring 39 is interposed between the second surface (upper surface) 28b of the piston 28 and the end cap 34. To introduce pressurized fluid into the pressure chamber 38, a passage hole 40 is formed inside the rod 23 and the needle valve body 22, connecting the first passage 10 (second port 6) and the pressure chamber 38. The first end 40a of the passage hole 40 opens at the tip of the needle valve body 22, and the second end 40b on the opposite side of the passage hole 40 opens on the side of the rod 23, closer to the pressure chamber 38 than the sealing member 27, and communicates with the pressure chamber 38 through a gap 41 between the outer circumference of the rod 23 and the inner circumference of the sliding hole 26. Furthermore, the rod 23 moves back and forth in the axial direction L, thereby controlling the opening and closing of the needle valve body 22. This is achieved through the interaction of the pressure fluid acting on the needle valve body 22 in the upward direction (opening direction) as shown in the figure, the pressure fluid acting on the piston 28 in the pressure chamber 38 as shown in the figure, and the spring force of the compression spring 39 acting on the piston 28 in the downward direction (closing direction) as shown in the figure. In the fluid control valve 1A having the above configuration, as shown in Figure 1, under normal conditions when no fluid pressure is acting on the needle valve body 22 and piston 28, the spring force of the compression spring 39 pushes the piston 28 down to its lowered end position, causing it to contact the stop portion 38a of the pressure chamber 38. As a result, the rod 23 and needle valve body 22 occupy their initial positions, and the valve head 22a of the needle valve body 22 restrictively opens the throttling hole 21. The degree of opening of the throttling hole 21 at this time is the initial opening degree. From this state, when pressurized fluid is supplied to the first port 5, the pressurized fluid flows through the first flow path 10 toward the second port 6 from the restrictively open throttling hole 21 in a reduced pressure or flow rate restricted state. At this time, the fluid pressure acts upward on the needle valve body 22 as shown in the figure, and at the same time acts upward on the piston 28 as it flows into the pressure chamber 38 through the conduction hole 40. However, because the pressure is low, the spring force of the compression spring 39 maintains the rod 23 and the needle valve body 22 in their initial positions. When the fluid pressure in the second port 6 increases, the fluid pressure is introduced into the pressure chamber 38 through the conduction hole 40 and acts upward on the piston 28. When this force exceeds the spring force of the compression spring 39, that is, when it exceeds the set pressure set by the compression spring 39, the piston 28 and rod 23 rise, as shown in Figure 4, causing the valve head 22a of the needle valve body 22 to completely exit the throttling hole 21, and the needle valve section 12 opens completely. Therefore, the configuration of the needle valve section 12 and the opening / closing control section 14 can be said to be a combination of the functions of a needle valve and a flow control valve in a known fluid control valve 1A. By combining the functions of a needle valve and a flow control valve in a known fluid control valve in this way, and by incorporating it coaxially into the valve housing, the configuration of the fluid control valve 1A is simplified compared to a known fluid pressure control valve, making it possible to obtain a fluid control valve 1A with a compact and rational design structure. The fluid control valve 1A is used to control the fluid pressure cylinder 70, for example, as shown in the fluid circuit in Figure 5. In this example, the first port 5 of the fluid control valve 1A is connected to a five-port solenoid valve 71, and the second port 6 is connected to the head-side port 72a of the fluid pressure cylinder 70. A speed control valve 73, consisting of a check valve 73a and a throttle valve 73b, is connected between the rod-side port 72b of the fluid pressure cylinder 70 and the solenoid valve 71. In the fluid circuit described above, in the state shown in Figure 5, since no pressurized fluid (e.g., compressed air) is supplied to the first port 5 of the fluid control valve 1A, as shown in Figures 1 and 2, the needle valve body 22 of the fluid control valve 1A occupies its initial position, and the throttling hole 21 is in a state of limited opening. When the solenoid valve 71 switches over from this state and pressurized fluid is supplied to the first port 5 of the fluid control valve 1A, the pressurized fluid flows from the throttling hole 21 through the first flow path 10 to the second port 6 in a flow-limiting state, and from the second port 6 into the head-side cylinder chamber 70a of the fluid pressure cylinder 70, causing the cylinder piston 74 to move slowly by meter-in control. At this time, the pressurized fluid also flows into the pressure chamber 38 through the conduction hole 40, but because the pressure in the head-side cylinder chamber 70a is low while the cylinder piston 74 is moving, the needle valve body 22 maintains its initial position, which is the release position, by the spring force of the compression spring 39. On the other hand, the pressurized fluid that has reached the check valve section 13 in the second flow path 11 from the first port 5 is blocked by the check valve section 13. When the cylinder piston 74 reaches the end of its stroke, the pressure in the head-side cylinder chamber 70a increases. When this pressure exceeds the set pressure set by the compression spring 39, as shown in Figure 4, the needle valve body 22 is pushed up by the combined force of the fluid pressure acting on the needle valve body 22 and the fluid pressure acting on the piston 28, fully opening the throttling hole 21. As a result, pressurized fluid is rapidly supplied into the head-side cylinder chamber 70a. Next, when the solenoid valve 71 is switched to the state shown in Figure 5, the pressurized fluid in the head-side cylinder chamber 70a is rapidly exhausted through the first port 5 and the solenoid valve 71 from both the throttle hole 21 and the check valve 13 of the needle valve section 12, which are in a fully open state, during the initial exhaust stage when the pressure in the head-side cylinder chamber 70a is high. Then, when the pressure in the head-side cylinder chamber 70a decreases, the needle valve body 22 returns to the initial position due to the spring force of the compression spring 39, and the throttle hole 21 becomes partially open, but the pressurized fluid in the head-side cylinder chamber 70a pushes open the check valve section 13 and is discharged in a free flow state through the second passage 11. Furthermore, as shown in Figures 1 and 2, the fluid control valve 1A can also be changed to a normally closed type fluid control valve, where the needle valve body 22 is in the closed position under normal conditions, by rotating the rod 23 with the opening adjustment mechanism 32 to displace the position of the rod 23 relative to the piston 28 downwards in the figure, and bringing the conical portion 22b of the needle valve body 22 into contact with the inner diameter end 15b of the cylindrical member 15. In this case, when the pressurized fluid supplied to the first port 5 acts on the needle valve body 22, the spring force of the compression spring 39 is set such that the needle valve body 22 compresses the compression spring 39 and rises slightly, thereby partially opening the throttling hole 21. Figure 6 shows a second embodiment of the fluid control valve according to the present invention. Compared to the fluid control valve 1A of the first embodiment, the configuration of the needle valve section 12 and the configuration of the opening / closing control unit 14 that controls the opening and closing of the needle valve section 12 differ in this second embodiment, but the other configurations are substantially the same. Therefore, in the following description, we will mainly describe the configuration of the needle valve section 12 and the opening / closing control unit, and in doing so, the same reference numerals used in the first embodiment will be used to describe the same components as those used in the fluid control valve 1A of the first embodiment. In the fluid control valve 1B of the second embodiment described above, the needle valve portion 12, under normal conditions, partially opens the throttling hole 21 by having the valve head 22a of the needle valve body 22 slightly fitted into the throttling hole 21. The opening degree (initial opening degree) of the needle valve body 22 at this time is determined by an opening degree adjustment mechanism 32 consisting of an adjustment member 50 that also serves as an end cap and an adjustment rod 51. This opening degree adjustment mechanism 32 will be described later. The needle valve body 22 has an annular stepped portion 22e formed between the rod 23 and the valve head 22a, based on the difference in their diameters, so as to be perpendicular to the axis L, and an annular flange portion 15c is formed at the upper end of the small diameter portion 15a of the cylindrical member 15, facing the stepped portion 22e and oriented perpendicular to the axis L. Furthermore, in the opening / closing control unit 14, the rod 23 and the piston 28 are integrally formed, a compression spring 39 is interposed between the first surface 28a of the lower surface of the piston 28 and the partition wall 25, and a pressure chamber 38 for introducing pressurized fluid is formed between the second surface 28b of the upper surface of the piston 28 and the adjustment member 50. Accordingly, the compression spring 39 biases the piston 28 in the direction that the needle valve body 22 opens the throttling hole 21, and the pressurized fluid introduced into the pressure chamber 38 presses the piston 28 in the direction that the needle valve body 22 closes the throttling hole 21. The conduit hole 40 connecting the pressure chamber 38 and the first flow path 10 penetrates the center of the rod 23, the first end 40a of the conduit hole 40 opens to the tip of the needle valve body 22, and the second end 40b on the opposite side of the conduit hole 40 opens to the pressure chamber 38 on the side of the adjustment rod 51, via the conduit hole 40 in the adjustment rod 51 which is screwed to the end of the rod 23 (or piston 28). The adjustment member 50, which forms part of the opening degree adjustment mechanism 32, serves as an end cap that airtightly covers the open second end 3b of the main block 3 to partition the pressure chamber 38, and also serves to adjust the initial opening degree of the throttling hole 21 by the needle valve body 22 by pressing the adjustment rod 51. The adjustment member 50 is screw-connected to the main block 3 so as to be able to move back and forth in the axial direction L by screwing a female screw portion 53 formed on the inner surface of the end cap 34 into a male screw portion 52 formed on the outer circumference of the end of the main block 3, and the end of the adjustment rod 51 is in contact with the inner surface of the top wall 50a of the adjustment member 50. When the adjustment member 50 is rotated and advanced toward the second port 6, the piston 28 and rod 23 are pushed downward in the figure via the adjustment rod 51, causing the valve head 22a of the needle valve body 22 to enter deeper into the throttling hole 21 and narrowing the opening of the throttling hole 21. When the adjustment member 50 is retracted, the piston 28 and rod 23 are displaced upward in the figure, causing the opening of the throttling hole 21 by the needle valve body 22 to widen. Reference numeral 54 in the figure indicates a sealing member that airtightly seals the space between the outer circumferential surface of the main block 3 and the inner circumferential surface of the adjustment member 50, and reference numeral 55 indicates a stopper that determines the position of the forward end of the adjustment member 50. When the adjustment member 50 is advanced to a position where the stopper 55 engages with the locking portion 3d inside the main block 3, the opening degree of the needle valve body 22 becomes minimum or fully closed. As shown in Figure 6, in normal operation when no fluid pressure is acting on the needle valve body 22 and piston 28, the spring force of the compression spring 39 causes the needle valve body 22 to rise, and the valve head 22a fits slightly into the throttling hole 21, leaving the throttling hole 21 partially open. Then, as shown in Figure 7, when fluid pressure is introduced into the pressure chamber 38 from the conduction hole 40 and the fluid pressure acting on the piston 28 exceeds the spring force of the compression spring 39, the valve head 22a of the needle valve body 22 fits completely into the throttling hole 21, and the stepped portion 22e abuts against the flange portion 15c at the upper end of the cylindrical member 15, closing the throttling hole 21. The fluid control valve 1B of the second embodiment is used by connecting it between both the head-side cylinder chamber 70a and the rod-side cylinder chamber 70b of the fluid pressure cylinder 70 and the 5-port solenoid valve 71, as shown in the fluid circuit in Figure 8. When the solenoid valve 71 switches from the state shown in Figure 8 and pressurized fluid is supplied to the first port 5 of the first fluid control valve 1B-1 connected to the head-side cylinder chamber 70a, this pressurized fluid flows through the first passage 10 from the restrictively opened throttling hole 21 to the second port 6 in a flow-limiting state, and from the second port 6, it flows into the head-side cylinder chamber 70a through the head-side port 72a of the fluid pressure cylinder 70, causing the cylinder piston 74 to move slowly by meter-in control. At this time, the pressurized fluid also flows into the pressure chamber 38 through the conduction hole 40, but because the pressure in the head-side cylinder chamber 70a is low while the cylinder piston 74 is moving, the needle valve body 22 maintains a restricted-open state by the spring force of the compression spring 39. On the other hand, the pressurized fluid that has reached the check valve section 13 in the second flow path 11 from the first port 5 is blocked by the check valve section 13. Furthermore, in the second fluid control valve 1B-2 connected to the rod-side cylinder chamber 70b, exhaust from the rod-side cylinder chamber 70b is discharged in a free-flow state through the rod-side port 72b and the second port 6, through the check valve section 13 of the second flow path 11, and then through the solenoid valve 71 from the first port 5. When the cylinder piston 74 reaches the stroke end, the pressure in the head-side cylinder chamber 70a increases. When this pressure exceeds the set pressure set by the compression spring 39 in the first fluid control valve 1B-1, as shown in Figure 7, the piston 28 is pushed down by the action of the pressurized fluid introduced into the pressure chamber 38, which also pushes down the needle valve body 22, causing the valve head 22a to be fully fitted into the throttling hole 21 and the stepped portion 22e to come into contact with the flange portion 15c, thereby completely closing the throttling hole 21 and maintaining the pressure in the head-side cylinder chamber 70a. In contrast, in the second fluid control valve 1B-2, the needle valve body 22 occupies the normal position, which is the restricted-open state. Next, when the solenoid valve 71 is switched to the state shown in Figure 8, the pressurized fluid in the head-side cylinder chamber 70a is discharged in a free-flow state by pushing open the check valve section 13 in the second passage 11 of the first fluid control valve 1B-1. As a result, the pressure in the head-side cylinder chamber 70a decreases, and the needle valve body 22 opens the throttle hole 21. After that, the pressurized fluid in the head-side cylinder chamber 70a is discharged through the opened throttle hole 21 and the check valve section 13. In contrast, the second fluid control valve 1B-2 performs the same operation as the first fluid control valve 1B-1 when it moves the piston 28 forward. Figures 9-12 show a third embodiment of the fluid control valve according to the present invention. The main differences between the fluid control valve 1C of this third embodiment and the fluid control valve 1A of the first embodiment are the configuration of the valve housing 2 and the configuration of the opening adjustment mechanism 32 that adjusts the initial opening of the needle valve section 12. The fluid control valve 1C of this third embodiment will be described below. In this description, components of the fluid control valve 1C that have the same function but differ in form from those of the fluid control valve 1A of the first embodiment will be described using the same reference numerals used for the fluid control valve 1A. Components that are substantially the same in form and function as those of the fluid control valve 1A will be given the same reference numerals used for the fluid control valve 1A, and their detailed description will be omitted. As shown in Figure 9, the valve housing 2 of the fluid control valve 1C has a port block 4 having a first port 5 and a main block 3 having a second port 6. In the fluid control valve 1C, as will be clear from the following explanation, the port block 4 has most of the functions that the main block 3 and cylindrical member 15 had in the fluid control valve 1A of the first embodiment. Inside the cylindrical portion 4a of the port block 4 (hereinafter referred to as the "outer cylindrical portion 4a" for convenience), a cylindrical inner cylindrical portion 4b extending along the axis L is formed concentrically with the outer cylindrical portion 4a by being integrated with the outer cylindrical portion 4a at the upper end of the outer cylindrical portion 4a, and an annular flow path 19 leading to the first port 5 is formed between the outer circumference of the inner cylindrical portion 4b and the inner circumference of the outer cylindrical portion 4a. The upper end 4c of the inner cylindrical portion 4b protrudes upward from the upper end of the outer cylindrical portion 4a, and the lower end of the inner cylindrical portion 4b protrudes downward from the lower end of the outer cylindrical portion 4a, and the main block 3 is connected to the outer circumference of the lower end of the outer cylindrical portion 4a via a sealing member 57 so as to surround the portion of the lower end of the inner cylindrical portion 4b that protrudes from the outer cylindrical portion 4a. A small-diameter portion 4d is integrally formed at the lower end of the inner cylinder portion 4b, and a first flow path 10 and a throttling hole 21 are formed inside the small-diameter portion 4d, and a second flow path 11 and a check valve portion 13 are provided on the outer circumference of the small-diameter portion 4d. The first flow path 10 communicates with the annular flow path 19 through the throttling hole 21, the valve chamber 17, and a flow path hole 59 formed on the side surface of the inner cylinder portion 4b, and the second flow path 11 communicates with the annular flow path 19 through an annular communication passage 60 formed between the outer circumference of the lower end of the inner cylinder portion 4b and the inner circumference of the main block 3. Furthermore, inside the inner cylinder portion 4b, the valve chamber 17 and the piston chamber 29 are formed via a partition wall 25. A brass cylindrical guide 58 is airtightly and fixedly fitted inside the partition wall 25, and a rod 23 is slidably supported on the guide 58 via a sealing member 27. A needle valve body 22 is integrally formed at the tip (lower end) of the rod 23, and the conical valve head 22a of the needle valve body 22 is fitted into the throttling hole 21. A piston 28 is integrally formed on the portion of the rod 23 located inside the piston chamber 29. The guide 58, being integrated with the partition wall 25, serves to partition the valve chamber 17 and the piston chamber 29, and can therefore be said to form a part of the partition wall 25. A cylindrical brass end cover 61 is attached to the upper end 4c of the inner cylinder portion 4b, and the upper end 23d of the rod 23 passes through the lid portion 61a of the end cover 61 and protrudes above the end cover 61, with a compression spring 39 interposed between the lower surface of the lid portion 61a of the end cover 61 and the upper surface of the piston 28. The opening degree adjustment mechanism 32 includes a handle 62 for rotating the rod 23 and a cam mechanism 63 that displaces the rod 23 in the axial direction L as the rod 23 rotates. The handle 62 is a cylindrical, cap-shaped member that is attached to the upper end 4c of the inner cylinder portion 4b so as to be rotatable while covering the upper end 4c, the end cover 61, and the upper end 23d of the rod 23. The upper end 4c of the rod 23 is fitted into a locking hole 62a formed inside the handle 62. The locking hole 62a is a non-circular hole having a pair of flat portions at opposing positions on its wall, and the upper end 23d of the rod 23 also has a pair of flat portions at opposing positions on its outer circumference. These flat portions abut against each other and lock together, thereby fixing the handle 62 and the rod 23 in the rotational direction. The cam mechanism 63 has a spiral cam surface 63a formed to surround the rod 23 at a position above the partition wall 25 inside the inner cylindrical portion 4b of the port block 4, and a movable body 63b formed on the rod 23. As is clear from Figure 10, the cam surface 63a is inclined in a direction in which its height gradually decreases in a clockwise direction, that is, in a direction approaching the throttling hole 21, and a stopper 63c is formed at the boundary between the lowest and highest parts of the cam surface 63a, with which the movable body 63b abuts. On the other hand, as is clear from Figure 11, the movable body 63b extends in the axial direction L along the side surface of the rod 23 from the lower surface of the piston 28 which is integrated with the rod 23, and the lower end surface 63d of the movable body 63b is in contact with the cam surface 63a. Then, when the handle 62 is used to rotate the rod 23 clockwise or counterclockwise, the movable body 63b is displaced along the inclined cam surface 63a, causing the rod 23 to move back and forth in the axial direction L, which changes the degree to which the valve head 22a of the needle valve body 22 penetrates the throttling hole 21, thereby adjusting the initial opening of the throttling hole 21. Figure 9 shows the state in which the movable body 63b contacts the lowest part of the cam surface 63a, causing the rod 23, i.e., the needle valve body 22, to occupy its maximum forward position, and the initial opening of the throttling hole 21 by the needle valve body 22 becomes the minimum opening. From this state, when the rod 23 is rotated counterclockwise by approximately one rotation using the handle 62, the movable body 63b moves counterclockwise along the cam surface 63a, causing the rod 23, i.e., the needle valve body 22, to retract in the direction of the axis L while rotating. When the movable body 63b moves to the highest part of the cam surface 63a and contacts the stopper 63c, as shown in Figure 12, the needle valve body 22 occupies its maximum retracted position, and the initial opening of the throttling hole 21 by the needle valve body 22 becomes the maximum opening. The handle 62 can be locked in any rotational position, and the initial opening of the throttling hole 21 can be arbitrarily set between the minimum and maximum openings according to the rotation angle of the handle 62. Furthermore, the configuration and operation of the fluid control valve 1C of the third embodiment, other than those described above, are substantially the same as those of the fluid control valve 1A of the first embodiment, so their description will be omitted. 1A, 1B, 1C Fluid control valve 2 Valve housing 5 First port 6 Second port 10 First flow path 11 Second flow path 13 Check valve section 14 Opening / closing control section 21 Throttle hole 22 Needle valve body 23 Rod 25 Partition wall 27 Seal member 28 Piston 32 Opening degree adjustment mechanism 38 Pressure chamber 39 Compression spring 40 Conduction hole 50 Adjustment member 51 Adjustment rod 62 Handle 63 Cam mechanism 63a Cam surface 63b Moving body L Axis