Spool valve

Abstract

A spool valve (1) comprises: a sleeve (10) including an inlet port (11) and an outlet port (12); a spool (20) received in the sleeve (10); a biasing device (30) that presses a proximal end portion (20a) of the spool (20) toward a distal end portion (20b) of the spool (20); and a pressure detection port (56) that opens toward the distal end portion (20b). The spool (20) includes: a first land portion (21) positioned between the pressure detection port (56) and the inlet port (11); a second land portion (22); a groove portion (23) positioned between the first land portion (21) and the second land portion (22); a recessed portion (27) formed in the outer peripheral surface of the second land portion (22); and a communication passage (28) for a working fluid which is formed in the second land portion (22) and which allows communication between the groove portion (23) and the recessed portion (27). In the sleeve (10), a through hole (50) that faces the recessed portion (27) of the spool (20) is formed.

Description

[Technical field]

[0001] The present disclosure relates to a spool valve. [Background technology]

[0002] A spool valve has a sleeve and a spool housed in the sleeve, and opens and closes a flow path by movement of the spool. The sleeve is provided with a spool housing hole, and has an inlet port and an outlet port for the working fluid on its side. The spool has a land portion (large diameter portion) having an outer diameter approximately equal to the diameter of the sleeve housing hole, and a groove portion (small diameter portion) recessed radially inward from the outer circumferential surface of the land portion. The groove portion has a width that allows communication between the inlet port and the outlet port. The opening degree of the spool valve is adjusted according to the position of the groove portion due to the movement of the spool.

[0003] When the spool valve is open, the working fluid flows into the inlet port and is discharged from the outlet port through the groove. A force due to the flow of the working fluid acts on the inner surface of each groove near the inlet port and the outlet port. For example, when either the inlet port or the outlet port is throttled by the spool (in other words, when it is slightly open), a jet of the working fluid is generated. When the balance of the forces on the inlet port side and the outlet port side is broken by the pressure fluctuation caused by this jet, forces are generated in the spool in both the axial and radial directions. In general, these forces are called fluid forces. Since the axial fluid force acts in the direction to close the valve, when the valve is open with a small opening, the working fluid is likely to pulsate and pressure control is likely to become unstable. Patent Document 1 discloses a spool-type pressure control valve intended to suppress this pulsation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-169212 A Summary of the Invention [Problem to be solved by the invention]

[0005] Ideally, it is desirable for pressure control valves and flow control valves to be able to control the pressure of the working fluid at a constant level regardless of whether the flow rate of the working fluid increases or decreases. However, these valves have a so-called override characteristic in which the pressure of the working fluid increases as the flow rate of the working fluid increases. The above-mentioned fluid forces also affect this override characteristic. For example, when the fluid forces increase, the ratio of the change in pressure of the working fluid to the change in flow rate of the working fluid increases, making it difficult to control the pressure or flow rate.

[0006] An object of the present disclosure is to provide a spool valve that suppresses the effect of fluid force on override characteristics and that can be applied to a pressure control valve or a flow control valve. [Means for solving the problem]

[0007] A spool valve according to one aspect of the present disclosure is Connect to the inflow route Inlet port and The working fluid the sleeve extending in the axial direction and including an outlet port, a spool housed within the sleeve so as to be movable in the axial direction, a biasing device including a biasing member that presses a base end of the spool toward a tip end of the spool, and a pressure inspection port that opens toward the tip end of the spool, the spool including a first land portion located between the pressure inspection port and the inlet port in the axial direction, a second land portion located at a position capable of blocking the outlet port, a groove portion located between the first land portion and the second land portion and having a width capable of communicating between the inlet port and the outlet port, a recess formed on an outer circumferential surface of the second land portion, and a communication passage for the working fluid formed within the second land portion and communicating between the groove portion and the recess, the sleeve including a first land portion facing the recess of the spool, At the same time, the inlet passage is connected to the inlet passage or to a flow passage to which the inlet passage is connected. A through hole is formed. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a spool valve that can be applied to a pressure control valve or a flow control valve, while suppressing the effect of fluid force on the override characteristic. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a spool valve according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a cross-sectional view of a spool valve including a shaft. [Diagram 3] 3 is an enlarged cross-sectional view of the periphery of a groove portion of the spool shown in FIG. 2. [Figure 4] 3A is a cross-sectional view of a spool valve taken along line IVA-IVA in FIG. 2, and FIG. 3B is a cross-sectional view taken along line IVB-IVB in FIG. 2. [Diagram 5] 1A and 1B are planar developments showing several examples of outlet ports as viewed from a radial direction, in which (a) shows a first example of the outlet port, and (b) shows a second example of the outlet port. [Figure 6] 1A and 1B are diagrams showing the results of a numerical analysis using CFD on the static pressure distribution in a groove portion near the outlet port on a cross section perpendicular to the axis, where (a) is a diagram showing the static pressure distribution in a comparative example, and (b) is a diagram showing the static pressure distribution in this embodiment. [Figure 7] 1A and 1B are diagrams showing the results of a numerical analysis using CFD (Computational Fluid Dynamics) on the velocity distribution of a jet on a cross section including the axis, in which (a) is a diagram showing the velocity distribution of a jet in a comparative example, and (b) is a diagram showing the velocity distribution of a jet in this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, several embodiments of the present disclosure will be described. In addition, common parts in each drawing are given the same reference numerals, and duplicated explanations will be omitted. The spool valve according to the present embodiment can be applied as a pressure control valve or a flow control valve in an environment where electrical control is difficult, such as a fuel supply system of an aircraft.

[0011] A spool valve 1 according to this embodiment will be described. Fig. 1 is a perspective view of the spool valve 1, and Fig. 2 is a cross-sectional view of the spool valve 1 including the shaft 2. Fig. 3 is an enlarged cross-sectional view of the periphery of the groove portion 23 of the spool 20 shown in Fig. 2. Fig. 4 is a cross-sectional view of the spool valve 1, where (a) is a cross-sectional view taken along line IVA-IVA in Fig. 2, and (b) is a cross-sectional view taken along line IVB-IVB in Fig. 2.

[0012] For ease of explanation, the extension direction of the shaft 2 is referred to as the axial direction AD, and the circumferential and radial directions centered on the shaft 2 are referred to as the circumferential direction CD and the radial direction RD, respectively. The shaft 2 is the central axis of the sleeve 10 (described later) and the spool 20 (described later). The direction in which the spool 20 opens the outlet port 12 of the sleeve 10 (to the right in FIG. 2) is referred to as the opening direction, and the direction in which the spool 20 closes the outlet port 12 of the sleeve 10 (to the left in FIG. 2) is referred to as the closing direction. Both the opening direction and the closing direction are parallel to the axial direction AD.

[0013] As shown in Fig. 1, the spool valve 1 according to this embodiment has a substantially cylindrical outer shape extending in an axial direction AD. The spool valve 1 includes a sleeve 10, a spool (piston) 20, and an urging device 30. As shown in Fig. 2, the spool valve 1 is attached to the housing 40 by being inserted into a mounting hole 43 formed in the housing 40, for example.

[0014] First, the sleeve 10 will be described. The sleeve 10 is a hollow cylindrical member extending in the axial direction AD, and accommodates the spool 20 in an accommodation hole 13 so as to be movable in the axial direction AD. The accommodation hole 13 is formed in the sleeve 10 and extends in the axial direction AD with the shaft 2 as its center.

[0015] An inlet port 11 and an outlet port 12 are provided on the outer circumferential surface 10a of the sleeve 10. The inlet port 11 is an inlet for the working fluid, and is connected to an inlet passage 41 formed in the housing 40. As shown in Fig. 4(a) , the inlet port 11 has a predetermined width in the axial direction AD, and is formed over the entire area in the circumferential direction CD except for the area where the rib 14 is provided. The inlet port 11 is always connected to the groove portion 23 of the spool 20.

[0016] The outlet port 12 is located between the inlet port 11 and the base end 20a of the spool 20. The outlet port 12 is an outlet for the working fluid, and communicates with an outlet passage 42 formed in the housing 40. As shown in FIG. 4(b), the outlet port 12 is formed in a plurality of regions 15 (FIG. 5) arranged at intervals in the circumferential direction CD. Each region 15 defines the outer shape of the outlet port 12. The regions 15 are located, for example, at equal intervals along the circumferential direction CD (for example, every 90° around the axis 2).

[0017] The outlet port 12 will now be described in detail. 5 is a planar development showing several examples of the outlet port 12 as viewed from the radial direction RD, where (a) is a diagram showing a first example of the outlet port 12 and (b) is a diagram showing a second example of the outlet port 12. As shown in these figures, the outlet port 12 is a single opening, and is formed in a plurality of regions 15 arranged at intervals in the circumferential direction CD. The outlet port 12 is also divided into a first portion (segment) 17 and a second portion (segment) 18. The first portion 17 is located closer to the inlet port 11 than the second portion 18. The second portion 18 is located farther from the inlet port 11 than the first portion 17.

[0018] In the developed surface of FIG. 5, the outer shape of the first portion 17 has an isosceles triangle or a shape similar thereto with the apex 17a facing the inlet port 11. That is, the width of the first portion 17 along the circumferential direction CD increases as it approaches the second portion 18. The increase rate of the width in the circumferential direction CD may be constant as shown in FIG. 5(a), or may increase according to an exponential function or a function having an increase rate similar to an exponential function as shown in FIG. 5(b). In the latter case, the outer shape of the first portion 17 has two sides 17b, 17b forming the apex angle curved toward the first portion 17 (toward the inside of the second portion) compared to the triangular outer shape shown in FIG. 5(a).

[0019] 5, the outer shape of the second portion 18 is a rectangle having sides extending in both the axial direction AD and the circumferential direction CD. That is, the width of the first portion 17 along the circumferential direction CD is constant.

[0020] For convenience of explanation, the area 15 of the outlet port 12 shown in Fig. 5 is expanded outward from the area where the opening of the outlet port 12 is formed. However, in reality, the opening of the outlet port 12 coincides with the area 15 of the outlet port 12.

[0021] Furthermore, the shape of region 15 is not limited to the above-mentioned substantially pentagonal shape. That is, region 15 may be composed of only first portion 17 or only second portion 18 depending on the specifications of spool valve 1.

[0022] A through hole 50 is formed in the outer circumferential surface 10a of the sleeve 10. The through hole 50 extends in the radial direction RD and communicates with a flow passage 47 formed in the housing 40. The through hole 50 also communicates with the accommodation hole 13. Therefore, the working fluid flows between the second land portion 22 and the sleeve 10 through the through hole 50. The working fluid also flows between the first land portion 21 and the sleeve 10 through a similar through hole (not shown). By allowing the working fluid to flow into these gaps, the inflow of fluid from the inflow path 41 into the gaps is prevented, and the sticking of the spool 20 due to the inflow of potential contaminants is prevented.

[0023] The flow path 47 is connected to the inflow path 41 or a flow path (not shown) to which the inflow path 41 is connected. The flow path 47 is a flow path whose cleanliness is maintained by redundantly connecting filters with small pressure loss. Therefore, the pressure in the flow path 47 is equal to the pressure in the inflow path 41. The flow path 47 may be connected to the outflow path 42 or a flow path (not shown) to which the outflow path 42 is connected. In this case, the amount of fluid flowing through the flow path 47 is relatively less than the fluid flowing through the inflow path 41 due to the above-mentioned filter. Therefore, the pressure in the flow path 47 is equal to the pressure in the outflow path 42.

[0024] As shown in FIG. 3, a protrusion 51 is provided on the outer peripheral surface 10a of the sleeve 10. Each protrusion 51 protrudes radially outward and is formed in an annular shape centered on the shaft 2. The protrusion 51 also has a groove 52 recessed inward in the radial direction RD. A seal member 53 (see FIG. 2), such as an O-ring, is fitted in the groove 52. When the spool valve 1 is inserted into the mounting hole 43, the seal member 53 is pressed against the inner peripheral surface 43a of the mounting hole 43 formed in the housing 40 by elastic deformation. This separates the space (gap) between the sleeve 10 and the housing 40, preventing leakage of the working fluid that has flowed into the separated space. In addition, the pressure contact of the seal member 53 stably maintains the position of the sleeve 10 in the mounting hole 43.

[0025] As shown in FIG. 3, a washer (lid) 55 is provided at the tip 10b of the sleeve 10. The washer 55 is a disk that covers the accommodation hole 13, and a pressure inspection port 56 is formed at its center. As shown in FIG. 1, the pressure inspection port 56 penetrates the washer 55 in the axial direction AD and communicates between the pressure inspection flow passage 45 and the accommodation hole 13. The washer 55 may be provided separately from the sleeve 10, or may be formed from a single base material together with the sleeve 10 as the tip surface of the sleeve 10. The pressure inspection flow passage 45 is connected to the inflow passage 41 or a flow passage (not shown) to which the inflow passage 41 is connected. Therefore, the pressure in the pressure inspection flow passage 45 is equal to the pressure in the inflow passage 41.

[0026] Next, the spool 20 will be described. The spool 20 is a rod-shaped member with a circular cross section that extends in an axial direction AD from a base end 20a to a tip end 20b. As shown in Fig. 1, the spool 20 is accommodated in an accommodation hole 13 formed in the sleeve 10 so as to be movable (reciprocable) in the axial direction AD.

[0027] The spool 20 includes a first land portion (large diameter portion) 21, a second land portion (large diameter portion) 22, and a groove portion (small diameter portion) 23. The first land portion 21 and the second land portion 22 have an outer diameter that is approximately equal to (i.e., slightly smaller than) the inner diameter of the accommodation hole 13, and are arranged in the axial direction AD with the groove portion 23 sandwiched therebetween. The first land portion 21 is located between the pressure inspection port 56 (washer 55) and the inlet port 11 in the axial direction AD. On the other hand, the second land portion 22 is located at a position where the outlet port 12 can be blocked by the movement of the sleeve 10. Note that a plurality of grooves (so-called labyrinth grooves) (not shown) for preventing hydraulic lock are formed on each of the outer circumferential surface 21a of the first land portion 21 and the outer circumferential surface 22a of the second land portion 22.

[0028] The groove 23 is located between the first land portion 21 and the second land portion 22, and is recessed radially inward from the outer circumferential surface of the spool 20, and extends over the entire area in the circumferential direction CD. Thus, the groove 23 is formed in an annular shape centered on the shaft 2. The groove 23 has a width in the axial direction AD that allows communication between the inlet port 11 and the outlet port 12, and forms a flow path for the working fluid within the groove 23.

[0029] The inner surface of groove portion (small diameter portion) 23 includes a cylindrical surface (intermediate portion) 24, a first annular surface (expanded diameter portion) 25, and a second annular surface (expanded diameter portion) 26. Cylindrical surface 24 has a constant diameter and extends in an axial direction AD about axis 2.

[0030] The first annular surface 25 extends from the cylindrical surface 24 toward the outer circumferential surface 21a of the first land portion 21 while curving, and is connected to the outer circumferential surface 21a. The first annular surface 25 gradually deflects the flow of the working fluid flowing from the inlet port 11 into the groove portion 23 from the radial direction RD to the axial direction AD.

[0031] The second annular surface 26 extends from the cylindrical surface 24 toward the outer circumferential surface 22a of the second land portion 22 while curving, and connects to the outer circumferential surface 22a. The second annular surface 26 gradually deflects the flow of the working fluid flowing out from the groove portion 23 to the outlet port 12 from the axial direction AD to the radial direction RD. The continuous deflection by each annular surface suppresses excessive collision of the working fluid with the groove portion 23, and reduces the excessive pressure on the spool 20 caused by the collision.

[0032] 3, a recess 27 is formed in the outer peripheral surface 22a of the second land portion 22. The recess 27 faces the through hole 50 and extends over the entire area in the circumferential direction CD. Therefore, the recess 27 is formed in an annular shape centered on the shaft 2. In addition, the recess 27 has a width in the axial direction AD that maintains a state in which it faces the through hole 50 regardless of the position of the spool 20.

[0033] A plurality of communication passages 28 are formed in the second land portion 22. The communication passages 28 extend from the recess 27 to the groove portion 23 in the axial direction AD as holes having, for example, a circular cross section, and communicate between the groove portion 23 and the recess 27. The communication passages 28 open to the second annular surface 26. As shown in FIG. 10, the communication passages 28 are positioned at equal intervals in the circumferential direction CD (for example, every 90° around the axis 2). The number and angular intervals of the communication passages 28 can be set arbitrarily. The cross-sectional area of ​​the communication passages 28 perpendicular to the extension direction has a value that allows the working fluid to be supplied from the recess 27 to the groove portion 23 without excessive delay when the spool valve 1 is in an open state.

[0034] The groove 23 moves in the axial direction AD as the spool 20 moves. Depending on the position of the groove 23, the inlet port 11 and the outlet port 12 are connected or disconnected via the groove 23. In addition, the flow rate of the working fluid can be adjusted by changing the opening area of ​​the groove 23 relative to the outlet port 12.

[0035] Next, the biasing device 30 will be described. The biasing device 30 biases the base end 20a of the spool 20 toward the tip end 20b (i.e., toward the valve closing direction). As shown in Fig. 2, the biasing device 30 has a spring 31 as a biasing member, a pair of retainers 32, 32, and an operating part (handle) 33. The spring 31 presses the base end 20a of the spool 20 toward the tip end 20b of the spool. The spring 31 is a so-called compression coil spring, and has a spring constant that generates a biasing force within a predetermined range. The spring 31 is housed in the operating part 33 in a state where it is held by the pair of retainers 32, 32 from both sides in the axial direction AD.

[0036] The operating part 33 is a hollow cylindrical member with a bottom, and has a storage section 34 that opens toward the spool 20. The storage section 34 stores the spring 31 and the pair of retainers 32, 32. A screw thread 35 is formed on an outer peripheral surface 33a of the operating part 33, and the screw thread 35 screws into a screw groove 44 formed on an inner peripheral surface 43a of the mounting hole 43. Therefore, the operating part 33 moves in the axial direction AD by rotating about the axis 2. In addition, an annular groove 37 is formed in a portion of the outer peripheral surface 33a of the operating part 33 between the screw thread 35 and an edge portion 36 of the operating part 33 facing the spool 20 (see FIG. 3), and a seal member 53 is attached to this groove 37. When the operating portion 33 is inserted into the mounting hole 43, the sealing member 53 is pressed toward the inner surface 43a of the mounting hole 43, and this elastic deformation prevents leakage of the working fluid from between the outer surface 33a of the operating portion 33 and the inner surface 43a of the mounting hole 43.

[0037] Regardless of the position of the operating part 33, the accommodation part 34 of the operating part 33 communicates with the drain passage 46. The drain passage 46 is connected to the outflow passage 42 or a passage (not shown) connected to the outflow passage 42 via an orifice (not shown). Therefore, the pressure in the accommodation part 34 changes gradually so as to maintain equilibrium with the pressure in the outflow passage 42. A groove (notch) 38 may be formed in the edge part 36 of the operating part 33. By forming the groove 38, communication between the drain passage 46 and the accommodation part 34 is maintained even if the edge part 36 of the operating part 33 comes into contact with the spool 20.

[0038] By rotating the operating part 33, the operating part 33 approaches or moves away from the sleeve 10. When the operating part 33 approaches the sleeve 10, the spring 31 contracts, and the biasing force of the spring 31 and the pressure inside the operating part 33 are transmitted to the spool 20 via the retainer 32. Therefore, the pressure on the spool valve 1 can be adjusted by adjusting the number of rotations of the operating part 33. In this embodiment, the pressure can be set simply by mechanically rotating the operating part 33. In other words, electrical control using a solenoid or the like is not required.

[0039] Next, the operation of the spool valve 1 will be described. The operation of the spool valve 1 according to this embodiment as a pressure control valve or a flow control valve is basically the same as that of a conventional pressure control valve or a flow control valve equipped with a spool. That is, the position of the spool 20 is determined according to the difference between the pressure on the spool 20 by the biasing device 30 and the pressure of the working fluid in the pressure inspection port 56, and the opening area (opening degree) of the outlet port is determined according to this position.

[0040] Furthermore, as the flow rate of the working fluid flowing out of the outlet port 12 increases, the contraction of the spring 31 increases and the biasing force at that flow rate also increases. As the flow rate increases, the fluid force due to the jet at the outlet port 12 also increases. Therefore, when the spool valve 1 is in an open state, the pressure of the working fluid increases as the flow rate increases (override characteristic). However, when the spool valve 1 functions as a pressure control valve or a flow rate control valve, it is desirable to be able to control the pressure of the working fluid to a constant value regardless of whether the flow rate increases or decreases.

[0041] Therefore, in this embodiment, a plurality of communication passages 28 that communicate between the groove 23 and the recess 27 are formed in the second land portion 22. A flow passage 47 (see FIG. 2) in the housing 40 that communicates with the through hole 50 connects to the inflow passage 41 or a flow passage (not shown) to which the inflow passage 41 is connected. Therefore, the pressure in the recess 27 and the pressure in the communication passage 28 are both equal to the pressure in the inflow passage 41. In addition, the groove 23 always communicates with the inflow passage 41 via the inlet port 11. Therefore, when the spool valve 1 is in a closed state, there is no flow of the working fluid, so the pressure in the groove 23 and the pressure in the communication passage 28 are equal.

[0042] When the spool valve 1 is in an open state, a jet of working fluid is generated near the outlet port 12. Therefore, the static pressure around the second annular surface 26 of the groove portion 23 decreases. However, the communication passage 28 opens into the second annular surface 26. As described above, the pressure in the communication passage 28 is equal to the pressure in the inlet passage 41. Therefore, when the static pressure around the second annular surface 26 decreases, working fluid is supplied to that area from the communication passage 28, and the decrease in static pressure is suppressed.

[0043] Supplying the working fluid through the communication passage 28 suppresses a drop in static pressure, reduces the force due to the static pressure on the surface of the spool 20 facing the communication passage 28, and reduces the fluid force in the axial direction AD. As a result, the fluid force in the axial direction AD acting in the direction to close the valve is reduced, improving the override characteristics.

[0044] The improvement of this override characteristic will now be described. FIG. 6 is a diagram showing the results of a numerical analysis using CFD on the static pressure distribution in the groove portion 23 near the outlet port on a cross section perpendicular to the axis 2. FIG. 6(a) shows the static pressure distribution in a comparative example, and FIG. 6(b) shows the static pressure distribution in this embodiment. In both cases, the change in static pressure is represented by light and dark colors, with darker (darker black) areas indicating lower static pressure. In the comparative example shown in FIG. 6(a), the communication passage 28 of this embodiment is not formed. Except for this point, the two are assumed to have the same configuration.

[0045] In Fig. 6(b), the low pressure region 62A shown in Fig. 6(a) is shown by a hatched region, and the communication passage 28 opening to the second annular surface 26 is shown by a dotted line. Focusing on the region 63 surrounded by the two-dot chain line, it can be seen that the area of ​​the low pressure region 62B shown in Fig. 6(b) is smaller than the area of ​​the low pressure region 62A shown in Fig. 6(a), and that the region with the most significant pressure drop (i.e., the darkest region), which is distributed near the boundary between the groove portion 23 and the outlet port 12, has also been reduced. In other words, the drop in static pressure within the region 63 is suppressed.

[0046] A decrease in static pressure in a certain region means an increase in dynamic pressure in that region. In other words, a decrease in static pressure suggests an acceleration of the working fluid in that region. For this reason, the reduction in low-pressure region 62B shown in FIG. 6(b) suggests a decrease in the velocity of the jet 60 of the working fluid, that is, a decrease in the fluid force.

[0047] FIG. 7 shows the results of a numerical analysis using CFD (Computational Fluid Dynamics) on the velocity distribution of the jet on a cross section including the axis 2. FIG. 7(a) shows the velocity distribution of the jet in a comparative example, and FIG. 7(b) shows the velocity distribution of the jet in this embodiment. In the comparative example, the communication passage 28 of this embodiment is not formed. However, the outer shape of the outlet port 112 in the comparative example is the same as the outer shape of the outlet port 12 in this embodiment, and the opening area of ​​the outlet port in both analyses is set to the same value. In addition, this value is half the opening area when the outlet port is fully open.

[0048] As shown in Figures 7(a) and 7(b), in both analysis results, the jet 60 of the working fluid flows generally radially outward, but is slightly inclined toward the opening direction of the spool valve 1 (to the right in the figures). Also, when focusing on the region 65 at the same position surrounded by the dotted line, the jet 60 shown in Figure 7(b) is thinner than the jet 60 shown in Figure 7(a). In particular, when comparing the velocity distribution within the region 65 at the same position in both figures, a relatively high-speed flow occurs over a wide area in Figure 7(a), whereas flows of similar speed are reduced and their distribution is narrowed in Figure 7(b).

[0049] The vicinity of the boundary surface between the groove portion 23 and the outlet port 12 is the starting point of the jet of working fluid. The velocity component of the jet 60 flowing in the opening direction of the spool valve 1 contributes to the fluid force in the axial direction AD acting in the closing direction of the spool valve 1. Therefore, compared with the result of the comparative example shown in Fig. 7(a), the result shown in Fig. 7(b) shows that, of the velocity components of the jet 60, the velocity component that contributes to the fluid force in the axial direction AD is reduced.

[0050] Therefore, by providing the communication passage, the fluid force in the axial direction can be reduced. That is, according to this embodiment, the effect of the fluid force on the override characteristic of the pressure control valve or the flow control valve can be suppressed. In other words, the override characteristic can be improved.

[0051] In addition, the reduction of the axial fluid force is achieved by supplying the working fluid to the space in the groove close to the outlet port through a communication passage. Therefore, there is no need to locally modify the shape of the inner surface of the groove of the spool, such as by creating a recess. This makes it possible to prevent foreign matter in the working fluid from adhering to the groove, and the original performance of the spool valve can be maintained for a long period of time, even in an environment where foreign matter is likely to be mixed into the working fluid.

[0052] The present disclosure is not limited to the above-described embodiment, but is defined by the claims, and includes all modifications within the meaning and scope equivalent to the claims.

Claims

[Claim 1] a sleeve extending axially therethrough, the sleeve including an inlet port for connecting to an inlet passage for a hydraulic fluid and an outlet port for the hydraulic fluid; A spool accommodated in the sleeve so as to be movable in the axial direction; a biasing device including a biasing member that presses a base end of the spool toward a tip end of the spool; a pressure inspection port that opens toward the tip end of the spool; Equipped with The spool is a first land portion located between the pressure inspection port and the inlet port in the axial direction; a second land portion located at a position capable of blocking the outlet port; a groove portion located between the first land portion and the second land portion and having a width allowing communication between the inlet port and the outlet port; a recess formed on an outer circumferential surface of the second land portion; a communication passage for the working fluid formed in the second land portion and communicating between the groove portion and the recess portion; Including, The sleeve has a through hole that faces the recess of the spool and is connected to the inlet passage or a flow passage to which the inlet passage is connected. Spool valve.

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