spool valve

Abstract

A valve core (3) is slidably inserted into the sliding hole (21) of the first housing (2). A servo chamber (41) is formed in the second housing (4) coaxial with the sliding hole (21). A sleeve (5) is slidably inserted into the servo chamber (41). A nut (71) is fixed on a piston (6) that is slidably fitted with the sleeve (5), and a screw shaft (72) that is screwed with the nut (71) is rotated by an electric motor (74). The second housing (4) has an input port (4a) and an outlet port (4b), and the first pressure chamber (42) is connected to the input port. The second pressure chamber (43) is separated from the input port (4a) and the outlet port (4b) by the piston (6) in a balanced state where the forces acting on the sleeve (5) from both sides are balanced. When the piston (6) moves from the balanced state, it is connected to the input port (4a) or the outlet port (4b).

Description

Technical Field

[0001] This invention relates to a spool valve that moves a valve core via an electric motor. Background Art

[0002] As a type of flow control valve used in hydraulic circuits, a spool valve is known. In such a spool valve, the valve core can be slidably inserted into a sliding hole in the housing, and the flow rate of the fluid flowing in the flow path formed in the housing is controlled by the position of the valve core.

[0003] Among spool valves, there are spool valves where the valve core moves due to pilot pressure and spool valves where the valve core moves due to an electric motor. For example, Patent Document 1 discloses a spool valve in which a direct-acting mechanism converting rotary motion into linear motion is provided between the electric motor and the valve core. Specifically, in this spool valve, the valve core is connected to a piston, a nut is fixed on the piston, and a screw shaft that engages with the nut rotates via an electric motor.

[0004] Existing technical documents:

[0005] Patent documents:

[0006] Patent document 1: International Publication No. 2019 / 138945. Summary of the Invention

[0007] The problem the invention aims to solve:

[0008] However, in the spool valve disclosed in Patent Document 1, when the diameter of the valve core is large, the force (also known as flow force) exerted on the fluid flowing through the flow path by the valve core increases. Therefore, precise control of the valve core position requires a larger output electric motor, leading to increased cost and a larger size of the spool valve itself.

[0009] Therefore, the object of the present invention is to provide a spool valve that can precisely control the position of the valve core even when the output of the electric motor is small.

[0010] Solution methods:

[0011] To solve the aforementioned problem, the slide valve of the present invention is characterized by comprising: a first housing having a plurality of flow paths and a sliding hole; a valve core slidably inserted into the sliding hole; a second housing forming a servo chamber coaxial with the sliding hole; a sleeve slidably inserted into the servo chamber, dividing the servo chamber into a first pressure chamber adjacent to the first housing and a second pressure chamber away from the first housing, and connected to the valve core in the first pressure chamber; a piston slidably fitted with the sleeve and extending beyond the second pressure chamber from within the sleeve; a nut fixed to the piston; and a screw shaft screwed into the nut; and so on. The second housing has an input port and an outlet port connected to a pressure source of the working fluid. The first pressure chamber is connected to the input port. The second pressure chamber is isolated from the input port and the outlet port by the piston when the working fluid in the first pressure chamber acts on the sleeve in a balanced state, and when the piston moves from the balanced state toward the valve core, it is connected to the input port. When the piston moves from the balanced state toward the valve core, it is connected to the outlet port.

[0012] According to the above structure, when the piston moves from its equilibrium state towards the valve core via the electric motor, the second pressure chamber connects to the input port. Therefore, the pressure in the second pressure chamber increases, and the sleeve also moves towards the valve core. However, when the sleeve moves past its equilibrium position, the second pressure chamber connects to the discharge port, and the pressure in the second pressure chamber decreases. Through this action, the sleeve stops at a position where it re-establishes equilibrium. That is, the sleeve moves along with the piston. The same applies when the piston moves from its equilibrium state away from the valve core via the electric motor.

[0013] On the other hand, if the piston does not move, a balanced state is maintained. That is, the second pressure chamber is isolated from the inlet port and the outlet port by the piston. Therefore, even if the fluid flowing from the flow path of the first housing is subjected to force, the sleeve will not move due to the incompressibility of the working fluid in the second pressure chamber.

[0014] Thus, in this invention, since the force exerted on the fluid flowing through the flow path by the valve core does not affect the electric motor, the position of the valve core can be precisely controlled even if the output of the electric motor is small.

[0015] Invention effects:

[0016] According to the present invention, the position of the valve core can be precisely controlled even when the output of the electric motor is small. Attached Figure Description

[0017] Figure 1This is a cross-sectional view showing the overall structure of a slide valve according to an embodiment of the present invention;

[0018] Figure 2 yes Figure 1 A cross-sectional view of a portion of the slide valve shown;

[0019] Figure 3 yes Figure 2 Enlarged view of the main parts. Detailed Implementation

[0020] Figure 1 A slide valve 1 according to one embodiment of the present invention is shown. In this embodiment, the slide valve 1 is a three-position valve having three ports 2a to 2c. However, the slide valve 1 may also be a two-position valve. In addition, the number of ports of the slide valve 1 can be appropriately varied.

[0021] Specifically, the slide valve 1 includes a first housing 2 with ports 2a to 2c formed on its outer surface and a valve core 3 held in the first housing 2. Additionally, the slide valve 1 includes a second housing 4, a casing 73, and an electric motor 74, all coaxially arranged with the valve core 3. The second housing 4 is mounted on the first housing 2, and the electric motor 74 is mounted on the second housing 4 via the casing 73.

[0022] A sliding hole 21 is formed inside the first housing 2. The valve core 3 can be slidably inserted into the sliding hole 21. In addition, the first housing 2 has three flow paths 22 to 24 from the sliding hole 21 to the ports 2a to 2c. Furthermore, the number of flow paths formed in the first housing 2 can be appropriately changed according to the number of ports.

[0023] The valve core 3 has two annular grooves 31 and 32. For ease of explanation, the axial side of the valve core 3 will be referred to as one of the grooves below. Figure 1 The right side is called the right side, and the other side is called the right side. Figure 1 The left side is referred to as the left side. When the valve core 3 is in the neutral position, it isolates flow path 22 from flow paths 23 and 24. When the valve core 3 moves to the right from the neutral position, flow path 22 is connected to flow path 23 via annular groove 31. When the valve core 3 moves to the left from the neutral position, flow path 22 is connected to flow path 24 via annular groove 32.

[0024] In this embodiment, when the valve core 3 is in the neutral position, its left end protrudes from the first housing 2. However, the length of the valve core 3 can be appropriately changed, or the left end of the valve core 3 can be accommodated within the first housing 2 when in the neutral position. Furthermore, in this embodiment, the left end of the valve core 3 is formed to be smaller than the diameter of the sliding hole 21, but it could also be formed to be the same diameter as the sliding hole 21. Alternatively, if the left end of the valve core 3 does not interfere with the first housing 2 within its movable range, then the left end of the valve core 3 can be formed to be larger than the diameter of the sliding hole 21.

[0025] Second shell 4 Figure 2 As shown, a servo chamber 41 is formed coaxially with the sliding hole 21 of the first housing 2. That is, the second housing 4 is formed with a deeper bottom hole whose center line is aligned with the sliding hole 21. This bottom hole is covered by the first housing 2 and the valve core 3, thereby forming the servo chamber 41.

[0026] The sleeve 5 can be slidably inserted into the servo chamber 41. That is, the sleeve 5 divides the servo chamber 41 into a first pressure chamber 42 adjacent to the first housing 2 and a second pressure chamber 43 away from the first housing 2. The sleeve 5 includes a cylindrical portion surrounding the internal space and a blocking portion blocking the internal space from the right. That is, the internal space of the sleeve 5 is only open on the left side.

[0027] The sleeve 5 is connected to the valve core 3 within the first pressure chamber 42. In this embodiment, the right end of the sleeve 5 is connected to the left end of the valve core 3 via a universal joint. Specifically, the left end of the valve core 3 is provided with a groove 35, which holds the ball 15. On the other hand, the right end of the sleeve 5 is provided with a plate-shaped protrusion 45 that inserts into the groove 35, and the protrusion 45 is provided with a hole that engages with the ball 15.

[0028] However, in a different embodiment, the right end of the sleeve 5 may be provided with a groove 35 for retaining the ball 15, and the left end of the valve core 3 may be provided with a protrusion 45 that inserts into the groove 35. Alternatively, the right end of the sleeve 5 and the left end of the valve core 3 may be connected by a connector other than a universal joint (e.g., a ball joint or spherical joint).

[0029] Piston 6 extends to the left beyond the second pressure chamber 43 from inside sleeve 5. Piston 6 and sleeve 5 are slidably engaged. Piston 6 penetrates the portion of the second housing 4 located to the left of the second pressure chamber 43. The left-side portion of piston 6 located outside the second housing 4 is received within sleeve 73.

[0030] A nut 71 is fixed to the left side of the piston 6. More specifically, a retaining hole 65 opening to the left is provided on the left side of the piston 6 along the center line of the piston 6, and the nut 71 is inserted into the retaining hole 65. In addition, the piston 6 is guided by a guide mechanism (not shown) so that it can only move in the left and right directions (i.e., rotation is prohibited).

[0031] A screw shaft 72 is screwed onto the nut 71. The screw shaft 72 is rotated by the aforementioned electric motor 74. That is, when the electric motor 74 rotates the screw shaft 72 in one direction, the piston 6 with the nut 71 fixed to it moves to the right; when the electric motor 74 rotates the screw shaft 72 in the opposite direction, the piston 6 with the nut 71 fixed to it moves to the left. Furthermore, as will be explained in detail later, because the sleeve 5 moves along with the piston 6, the valve core 3 connected to the sleeve 5 also moves by the same amount in the same direction as the piston 6.

[0032] Furthermore, in this embodiment, such as Figure 3 As shown, a mechanism for maintaining the valve core 3 in a neutral position when no power is supplied to the electric motor 74 is provided between the left side portion of the piston 6 and the housing 73. This mechanism includes a coil spring 81 configured with the nut 71 located inside, a first spring seat 82 supporting both ends of the coil spring 81, and a second spring seat 83.

[0033] The coil spring 81 applies a force to the piston 6 to maintain the valve core 3 in a neutral position. The first spring seat 82 and the second spring seat 83 are both annular and can be slidably engaged with the left side of the piston 6.

[0034] The piston 6 has a flange 66 at its left end that abuts against the first spring seat 82. In addition, a stop 67 that abuts against the second spring seat 83 is installed on the piston 6 at a position separating it from the flange 66 to the right.

[0035] In addition, a first step portion 84 is provided on the inner side of the cylindrical housing 73 at a position corresponding to the flange 66, and a second step portion 85 is provided at a position corresponding to the stop member 67.

[0036] According to this structure, when the electric motor 74 is not powered, the first spring seat 82 abuts against both the flange 66 and the first step portion 84 through the force applied by the coil spring 81, and the second spring seat 83 abuts against both the stop member 67 and the second step portion 85. This maintains the valve core 3 in a neutral position.

[0037] When piston 6 moves to the right from the neutral position of valve core 3, the first spring seat 82 is pushed apart from the first step portion 84 by flange 66, and the stop 67 is separated from the second spring seat 83. Conversely, when piston 6 moves to the left from the neutral position of valve core 3, flange 66 is separated from the first spring seat 82, and the second spring seat 83 is pushed apart from the second step portion 85 by stop 67.

[0038] Next, refer to Figure 2 The second shell 4 and its internal structure are described in detail.

[0039] The outer surface of the second housing 4 has an input port 4a that is connected to the pressure source 11 (e.g., a hydraulic pump) of the working fluid; and a drain port 4b that is connected to, for example, a tank 12 for the working fluid. For example, when the liquid flowing between the flow paths 22 and 24 of the first housing 2 is oil, the working fluid supplied from the pressure source 11 to the input port 4a may be the same oil.

[0040] The second housing 4 has a first flow path 44 from the input port 4a to the first pressure chamber 42. That is, the first pressure chamber 42 is connected to the input port 4a through the first flow path 44.

[0041] The bottom (right side portion) of the internal space of the sleeve 5 forms a discharge chamber 53 facing the right end face of the piston 6. In addition, the sleeve 5 is provided with a plurality of transverse holes 54, 55 extending radially outward from the discharge chamber 53.

[0042] The inner circumferential surface of the servo chamber 41 of the second housing 4 has an annular groove 46 at a position corresponding to the transverse holes 54 and 55. In addition, the second housing 4 forms a second flow path 47 from the bottom of the annular groove 46 to the discharge port 4b.

[0043] The piston 6 has a longitudinal hole 63 along its centerline. The longitudinal hole 63 connects the discharge chamber 53 to the aforementioned retaining hole 65.

[0044] Furthermore, the outer peripheral surface of the piston 6 is provided with a first annular groove 61 and a second annular groove 62 located closer to the right than the first annular groove 61. Thereby, a land portion 60 is formed between the first annular groove 61 and the second annular groove 62.

[0045] The sleeve 5 is provided with a first flow path 51 connecting the first pressure chamber 42 and the first annular groove 61, and a second flow path 52 is formed for connecting the second pressure chamber 43 with the first annular groove 61 or the second annular groove 62. The second flow path 52 has a first opening 52a for the first annular groove 61 and a second opening 52b for the second annular groove 62 on the inner circumferential surface of the sleeve 5.

[0046] The distance from the left end of the first opening 52a to the right end of the second opening 52b is set to be equal to the width of the platform surface 60 (the distance from the first annular groove 61 to the second annular groove 62). In addition, the piston 6 is provided with a plurality of transverse holes 64 extending from the bottom of the second annular groove 62 to the longitudinal hole 63.

[0047] The outer diameter of sleeve 5 is set to be larger than the maximum diameter of valve core 3 in sliding hole 21. Therefore, a force F1 acts to the left within sleeve 5 due to the working fluid in the first pressure chamber 42. When the pressure in the first pressure chamber 42 is P1, the maximum diameter of valve core 3 in sliding hole 21 is Da, and the outer diameter of sleeve 5 is Db, F1 = P1 × π × ((Db / 2)) 2 -(Da / 2) 2 ).

[0048] On the other hand, a force F2 is exerted to the right within the sleeve 5 due to the working fluid in the second pressure chamber 43. When the pressure in the second pressure chamber 43 is P2, the outer diameter of the sleeve 5 is Db, and the diameter of the piston 6 is Dc, F2 = P1 × π × ((Db / 2)) 2-(Dc / 2) 2 ).

[0049] In the structure described above, the pressure P2 of the second pressure chamber 43 is adjusted by balancing the leftward force F1 and the rightward force F2 acting on the sleeve 5 (F1 = F2). In this balanced state, the sleeve 5 is located where the first opening 52a and the second opening 52b of the second flow path 52 are blocked by the platform 60 of the piston 6. Therefore, the second pressure chamber 43 is isolated from the inlet port 4a and the outlet port 4b by the piston 6.

[0050] When piston 6 moves to the right (near valve core 3) from its equilibrium state via electric motor 74, the second pressure chamber 43 connects to input port 4a through the second flow path 52, first annular groove 61, first flow path 51, first pressure chamber 42, and first flow path 44. Therefore, the pressure in the second pressure chamber 43 increases, and sleeve 5 also moves to the right. However, when sleeve 5 moves to the right beyond its equilibrium position, the second pressure chamber 43 connects to discharge port 4b through the second flow path 52, second annular groove 62, transverse hole 64, longitudinal hole 63, discharge chamber 53, transverse holes 54 and 55, annular groove 46, and second flow path 47, and the pressure in the second pressure chamber 43 decreases. Through this action, sleeve 5 stops at a position where it re-establishes equilibrium. That is, sleeve 5 moves to the right following the movement of piston 6 to the right.

[0051] Conversely, when piston 6 moves to the left (away from valve core 3) from its equilibrium state via electric motor 74, the second pressure chamber 43 connects to discharge port 4b through the second flow path 52, second annular groove 62, transverse hole 64, longitudinal hole 63, discharge chamber 53, transverse holes 54 and 55, annular groove 46, and second flow path 47. Therefore, the pressure in the second pressure chamber 43 decreases, and sleeve 5 also moves to the left. However, when sleeve 5 moves to the left beyond its equilibrium position, the second pressure chamber 43 connects to input port 4a through the second flow path 52, first annular groove 61, first flow path 51, first pressure chamber 42, and first flow path 44, and the pressure in the second pressure chamber 43 increases. Through this action, sleeve 5 stops at the position where it re-establishes equilibrium. That is, sleeve 5 moves to the left following the leftward movement of piston 6.

[0052] On the other hand, if the piston 6 does not move, a balanced state is maintained. That is, the second pressure chamber 43 is isolated from the inlet port 4a and the outlet port 4b by the piston 6. Therefore, even if the fluid flowing from the valve core 3 through the flow paths 22 to 24 of the first housing 2 is subjected to force, the sleeve 5 will not move due to the incompressibility of the working fluid in the second pressure chamber 43.

[0053] Thus, in this invention, since the force exerted on the valve core 3 by the fluid flowing between flow paths 22 and 24 does not affect the electric motor 74, the position of the valve core 3 can be precisely controlled even if the output of the electric motor 74 is small.

[0054] (Modified example)

[0055] This invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of this invention.

[0056] For example, the coil spring 81 for maintaining the valve core 3 in a neutral position may not be provided. However, if the coil spring 81 is provided as in the embodiment described above, the valve core 3 can be maintained in a certain position even when the force exerted on the valve core 3 by the fluid flowing between flow paths 22 and 24 is large, regardless of whether the electric motor 74 is powered or not. Moreover, since the coil spring 81 is configured such that the nut 71 is located inside, it is not necessary to increase the overall length of the slide valve 1 for the configuration of the coil spring 81.

[0057] (Summarize)

[0058] The slide valve of the present invention is characterized by comprising: a first housing having a plurality of flow paths and a sliding hole; a valve core slidably inserted into the sliding hole; a second housing having a servo chamber coaxial with the sliding hole; a sleeve slidably inserted into the servo chamber, dividing the servo chamber into a first pressure chamber adjacent to the first housing and a second pressure chamber away from the first housing, and connected to the valve core in the first pressure chamber; a piston slidably fitted with the sleeve and extending beyond the second pressure chamber from within the sleeve; a nut fixed to the piston; a screw shaft screwed into the nut; and a mechanism for... An electric motor that rotates the screw shaft; the second housing has an input port and a discharge port connected to a pressure source of the working fluid; the first pressure chamber is connected to the input port; the second pressure chamber is isolated from the input port and the discharge port by the piston when the working fluid in the first pressure chamber acts on the sleeve and the working fluid in the second pressure chamber acts on the sleeve in a balanced state; when the piston moves from the balanced state toward the valve core, it is connected to the input port; when the piston moves from the balanced state toward the valve core, it is connected to the discharge port.

[0059] According to the above structure, when the piston moves from its equilibrium state towards the valve core via the electric motor, the second pressure chamber connects to the input port. Therefore, the pressure in the second pressure chamber increases, and the sleeve also moves towards the valve core. However, when the sleeve moves past its equilibrium position, the second pressure chamber connects to the discharge port, and the pressure in the second pressure chamber decreases. Through this action, the sleeve stops at a position where it re-establishes equilibrium. That is, the sleeve moves along with the piston. The same applies when the piston moves from its equilibrium state away from the valve core via the electric motor.

[0060] On the other hand, if the piston does not move, a balanced state is maintained. That is, the second pressure chamber is isolated from the inlet port and the outlet port by the piston. Therefore, even if the valve core is subjected to force from the fluid flowing through the flow path in the first housing, the sleeve will not move due to the incompressibility of the working fluid in the second pressure chamber.

[0061] Thus, in this invention, since the force exerted on the valve core by the fluid flowing between the flow paths does not affect the electric motor, the position of the valve core can be precisely controlled even if the output of the electric motor is small.

[0062] Alternatively, the aforementioned spool valve may also include a coil spring configured with the nut located internally, which applies a force to the piston to maintain the valve core in a neutral position. With this configuration, the valve core can be maintained in a certain position even when the force exerted on it by the fluid flowing through the flow path is large, regardless of whether power is supplied to the electric motor. Furthermore, because the coil spring is configured with the nut located internally, it is not necessary to increase the overall length of the spool valve to accommodate the coil spring configuration.

[0063] Symbol explanation:

[0064] 1. Spool valve

[0065] 11. Pressure Sources

[0066] 2 First shell

[0067] 21 Sliding hole

[0068] 22~24 flow path

[0069] 3 Valve core

[0070] 4 Second shell

[0071] 4a Input Port

[0072] 4b Discharge port

[0073] 41 Server Room

[0074] 42 First Pressure Chamber

[0075] 43 Second pressure chamber

[0076] 5 sleeves

[0077] 6 Pistons

[0078] 71 Nuts

[0079] 72 Screw Shaft

[0080] 74 Electric Motor

[0081] 81 Coil Spring

Claims

1. A slide valve, comprising: A first housing with multiple flow paths and sliding holes is formed; A valve core that can be slidably inserted into the sliding hole; A second housing is formed in the servo chamber coaxial with the sliding hole; A sleeve is slidably inserted into the servo chamber to divide the servo chamber into a first pressure chamber adjacent to the first housing and a second pressure chamber away from the first housing, and is connected to the valve core in the first pressure chamber; A piston that can slidably engage with the sleeve and extends from within the sleeve beyond the second pressure chamber; A nut fixed to the piston; The screw shaft that engages with the nut; An electric motor that rotates the screw shaft; as well as A coil spring is configured such that the nut is located internally and applies an applied force to the piston to maintain the valve core in a neutral position; The second housing has an input port and a discharge port for connection to a pressure source of the working fluid. The first pressure chamber is connected to the input port. In a balanced state where the force exerted by the working fluid in the first pressure chamber on the sleeve is equal to the force exerted by the working fluid in the second pressure chamber on the sleeve, the second pressure chamber is isolated from the input port and the discharge port by the piston. When the piston moves from the balanced state toward the valve core, it connects with the input port, and when the piston moves from the balanced state toward the valve core, it connects with the discharge port.

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