Spool valve

Abstract

To enable stable operation of a spool valve including an electric device.SOLUTION: A spool valve 1 comprises: a spool 2; a housing 3 that accommodates the spool so that the spool is reciprocally movable along an axis X; and an electric device 4 that switches a path for a hydraulic fluid by moving the spool along the axis. The spool has a first end surface 24 perpendicular to the axis. The housing has a locking surface 35 for positioning the spool at a neutral position by locking the first end surface of the spool. At least one of the first end surface and the locking surface has projections and recesses.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Patent Document 1 describes a hydraulic supply device equipped with a spool valve. The spool of the spool valve is biased to a neutral position by a spring. When hydraulic oil is supplied to a pressure adjustment port connected to a pressure adjustment circuit, the spool moves from the neutral position to a second position against the biasing force of the spring. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-125576 A Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, the field of technology for moving objects, including aircraft, has seen a trend toward electrification. Regarding spool valves for switching hydraulic oil paths, the adoption of spool valves that move the spool with an electric device, for example, an electric motor, instead of conventional spool valves that operate with hydraulic pressure, is being considered.

[0005] However, the inventors of the present application have noticed that in a spool valve equipped with an electric device, a phenomenon occurs in which the spool does not move even if the electric device has the ability to move the spool.

[0006] The techniques disclosed herein enable stable operation of a spool valve equipped with an electrically actuated device. [Means for solving the problem]

[0007] In a spool valve equipped with an electric device, the capacity of the electric device is set on the assumption that an equal hydraulic load acts on both the first side of the spool and the second side opposite to the first side. In other words, the hydraulic load acting on the spool in the direction of spool movement is usually substantially canceled out.

[0008] However, according to the inventor's study, it was found that the hydraulic load acting on the first side of the spool and the hydraulic load acting on the second side may become uneven. The inventor found that this phenomenon occurs because, when the first end face of the first side of the spool and the locking face of the housing are in contact with each other, it is difficult to supply hydraulic oil between the first end face and the locking face, or it takes a long time to supply hydraulic oil between the first end face and the locking face.

[0009] FIG 8 illustrates a spool valve 10 equipped with an electric device 40. A spool 20 is accommodated in a housing 30 so as to be reciprocatable in a direction along an axis X. The spool 20 extends in a direction along the axis X. A hydraulic load acting on a first side (i.e., the right side in FIG 8) of the spool 20 and a hydraulic load acting on a second side (i.e., the left side in FIG 8) are essentially equal to each other.

[0010] The electric device 40 is connected to a first end surface 240 of the spool 20. A spring 340 is located on a second end surface 250 of the spool 20. The spring 340 biases the spool 20 in the direction of the first side. The electric device 40 pushes the spool 20 in the direction of the second side against the biasing force of the spring 340.

[0011] 8, in the spool valve 10, the first end face 240 of the spool 20 and a locking face 350 of the housing 30 are locked to each other by the biasing force of the spring 340, so that the spool 20 is positioned in a neutral position. In order to ensure positional accuracy of the neutral position, the first end face 240 and the locking face 350 are in contact with each other on planes perpendicular to the axis X.

[0012] Here, if the machining precision of the first end face 240 and the locking surface 350 is high, the planes perpendicular to the axis X are in close contact with each other over the entire surfaces of the first end face 240 and the locking surface 350, so that the gap between the first end face 240 and the locking surface 350 becomes extremely small.

[0013] If the gap between the first end surface 240 and the locking surface 350 is extremely small, it is difficult to supply the hydraulic oil to the gap, or it takes a long time to supply the hydraulic oil (see the dashed arrow in FIG. 8). As a result, the load due to the hydraulic pressure acting on the first side of the spool 20 and the load due to the hydraulic pressure acting on the second side become uneven. In this case, the load due to the hydraulic pressure acting on the second side is higher than the load due to the hydraulic pressure acting on the first side. When the electric device 40 tries to move the spool 20 from the neutral position to the second position, the electric device 40 must move the spool 20 not only against the biasing force of the spring 340 and the friction acting on the spool 20 when the spool 20 moves, but also against the load difference due to the hydraulic pressure acting on the spool 20. The capacity of the electric device 40 becomes insufficient, and the spool 20 does not move.

[0014] In the conventional spool valves described in the above-mentioned patent documents, even if the load due to the hydraulic pressure acting on both sides of the spool is uneven, the spool can move by supplying a high hydraulic pressure to the pressure regulating port. In conventional spool valves that use hydraulic pressure, the unevenness of the load due to the hydraulic pressure acting on both sides of the spool has not been recognized as a technical problem.

[0015] Here, when the spool valve is a spool valve for an aircraft, the aircraft takes off and lands in areas with high temperatures, for example, above 50°C, and flies in the air at extremely low temperatures, for example, below -50°C. The temperature range in which the spool valve mounted on the aircraft is used is significantly wider than the temperature range of a spool valve used in a general environment. Due to the wide temperature range in which the valve is used, the viscosity of the hydraulic oil changes significantly from low viscosity to high viscosity.

[0016] The inventors of the present application have found that the phenomenon of the spool not moving is particularly noticeable when the temperature of the hydraulic oil is low. This is thought to be because when the temperature of the hydraulic oil is low, the viscosity of the hydraulic oil increases, making it more difficult for the hydraulic oil to be supplied between the first end face and the locking face, or taking more time to be supplied.

[0017] In order to solve the problem of the spool not moving, it is possible to increase the capacity of the electric device. However, an electric device with high capacity will require a larger spool valve. A large spool valve is disadvantageous as a spool valve mounted on a moving object.

[0018] In view of the cause of the phenomenon in which the spool does not move, the inventor of the present application has adopted a structure that makes it easy for hydraulic oil to be supplied between the first end face and the locking surface, thereby ensuring stable operation of the spool valve. Specifically, since the cause of the malfunction is the flat surfaces being in close contact over the entire surface of the first end face and the locking surface, the inventor of the present application has adopted a structure for the spool valve that forms a gap between the first end face and the locking surface through which hydraulic oil can flow.

[0019] Specifically, the technology disclosed herein relates to a spool valve that switches the path of hydraulic oil. A spool and a housing having a sleeve hole into which the spool is inserted and accommodating the spool so as to be capable of reciprocating along an axis; an electric device connected to the spool and configured to switch hydraulic fluid paths by moving the spool along the axis; The spool has a first end surface on a first side in a direction along the axis and perpendicular to the axis, The housing has a locking surface that is perpendicular to the axis and that locks onto the first end surface of the spool, At least one of the first end surface and the locking surface has projections and recesses.

[0020] The first end surface of the spool and the locking surface of the housing, which are surfaces perpendicular to the axis, are engaged with each other. The first end surface of the spool and the locking surface of the housing may be engaged with each other when the spool is in a neutral position, for example.

[0021] At least one of the first end face and the locking surface has projections and recesses. The projections and recesses prevent the first end face and the locking surface from being in close contact with each other over the entire surfaces of the first end face and the locking surface, and form a partial gap between the first end face and the locking surface. The projections and recesses may be through-holes such as slits.

[0022] When the first end face of the spool and the locking surface of the housing are locked together, hydraulic oil is supplied between the first end face and the locking surface through a gap formed between the first end face and the locking surface. Even if the hydraulic oil becomes cold and its viscosity increases, the hydraulic oil is still supplied between the first end face and the locking surface.

[0023] As a result, the hydraulic load acting on the first side of the spool and the hydraulic load acting on the second side opposite to the first side are equal or approximately equal. Since the hydraulic load acting on the spool in the axial direction is substantially cancelled out, the spool can move without increasing the capacity of the electric device. Therefore, the spool valve operates stably. In addition, the spool valve does not become large.

[0024] At least one of the first end surface and the locking surface may have a recess formed therein.

[0025] The recess recessed from the first end surface and / or the locking surface forms a gap without being in close contact with the locking surface and / or the first end surface. The hydraulic oil is supplied between the first end surface and the locking surface through the recess.

[0026] In addition, in the first end face and the locking surface, the flat surfaces abut against each other at locations where no recesses are formed. When the locking state between the first end face and the locking surface determines the neutral position of the spool, the abutment of the flat surfaces determines the neutral position of the spool with high precision.

[0027] At least one of the first end surface and the locking surface may have a protrusion formed thereon that protrudes from the surface.

[0028] The protrusions protruding from the first end face and / or the locking surface come into contact with the flat surface of the locking surface and / or the first end face, so that gaps are formed between the first end face and the locking surface at locations where no protrusions are formed. The hydraulic oil is supplied between the first end face and the locking surface through the gaps.

[0029] Furthermore, when the neutral position of the spool is determined by the engagement state between the first end face and the engagement surface, the neutral position of the spool is determined with high precision by the projection coming into contact with the flat surface.

[0030] A shim may be fixed to the first end surface or the locking surface, the shim being interposed between the first end surface and the locking surface.

[0031] A shim fixed to the first end face or the locking surface abuts against the locking surface or the first end face, forming a gap between the first end face and the locking surface. Hydraulic oil is supplied between the first end face and the locking surface through the gap.

[0032] Furthermore, when the neutral position of the spool is determined by the engagement state between the first end face and the engagement surface, the neutral position of the spool is determined with high precision by the shim abutting against the engagement surface or the first end face.

[0033] The shim may have a notch formed therein, the notch extending in a direction perpendicular to the axis.

[0034] The notch forms a gap extending in a direction perpendicular to the axis between the first end face and the locking surface when the first end face and the locking surface are engaged with each other. The gap extending in a direction perpendicular to the axis promotes the supply of hydraulic oil between the first end face and the locking surface.

[0035] The spool valve further includes a spring that biases the spool toward a neutral position by contacting a second end surface opposite to the first end surface in a direction along the axis, The electric device may be connected to the first end surface of the spool and may move the spool in a direction away from the first end surface and the locking surface against the biasing force of the spring.

[0036] As described above, the hydraulic load acting on the spool in the axial direction is substantially canceled out, so the electric device only needs to output the spring force and a force that counters the friction of the moving spool. The capacity of the electric device can be set to the minimum required capacity, making it possible to reduce the size of the electric device and the spool valve.

[0037] The spool valve may be a double-acting type having a first electric device connected to a first end face of the spool and a second electric device connected to a second end face of the spool. In this structure, the housing may have a first locking surface that locks to the first end face of the spool and a second locking surface that locks to the second end face of the spool, and at least one of the first end face and the first locking surface may have unevenness, and at least one of the second end face and the second locking surface may have unevenness.

[0038] Since hydraulic oil is easily supplied to the gap between the first end face and the first locking surface and the gap between the second end face and the second locking surface, the hydraulic load acting on the first end face of the spool and the hydraulic load acting on the second end face become equal or nearly equal. The reciprocating spool valve operates stably.

[0039] The spool valve may be for use in an aircraft.

[0040] Since spool valves for aircraft are used in a wide temperature range, they may be used in a state where the viscosity of the hydraulic oil is significantly increased. In the above-mentioned spool valve, the hydraulic oil is stably supplied between the first end face and the locking face even when the viscosity of the hydraulic oil is high, so that the spool valve operates stably. The above-mentioned spool valve is suitable for spool valves for aircraft. Effect of the Invention

[0041] The spool valve equipped with the above-mentioned electric device operates stably. [Brief description of the drawings]

[0042] [Figure 1] FIG. 1 is a cross-sectional view of a spool valve. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of the spool valve. [Diagram 3] FIG. 3 is a perspective view of the spool. [Figure 4] 4(a), (b), and (c) show modified examples of the spool. [Diagram 5] 5(a), (b), and (c) show modified examples of the spool. [Figure 6] FIG. 6 shows a modified example of a spool valve, and (b) is a cross-section taken along line bb of (a). [Figure 7] FIG. 7 shows a modified spool valve. [Figure 8] FIG. 8 shows a conventional spool valve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] Hereinafter, an embodiment of a spool valve will be described with reference to the drawings. The spool valve described here is merely an example.

[0044] (Overall structure of spool valve) 1 and 2 illustrate a spool valve 1. The spool valve 1 is used as a switching valve for switching the path of hydraulic oil in a hydraulic circuit mounted on an aircraft, for example. The application of the spool valve 1 is not limited to aircraft. The spool valve 1 can be mounted on various moving objects, such as automobiles and railroad cars.

[0045] The spool valve 1 includes a spool 2 , a housing 3 , and an electric device 4 .

[0046] The housing 3 accommodates the spool 2. The housing 3 has a sleeve 31 and a housing body 33. The sleeve 31 has a sleeve hole 311 extending along the axis X. A plurality of ports 32 are formed in the sleeve 31. The multiple ports 32 are aligned in a direction along the axis X. The multiple ports 32 each communicate with the sleeve hole 311.

[0047] It is also possible to omit the sleeve 31 and have the housing body 33 formed with a sleeve hole extending along the axis X and a port.

[0048] The housing body 33 holds the sleeve 31. The housing body 33 has an oil passage 331 that communicates with the port 32. The housing body 33 also supports a spring 34. The spring 34 expands and contracts in the direction along the axis X.

[0049] The spool 2 is inserted into the sleeve hole 311. The spool 2 extends along the axis X. The spool 2 can reciprocate along the axis X within the sleeve hole 311.

[0050] The spool 2 has a first land 21 and a second land 22. The first land 21 and the second land 22 each have an outer diameter corresponding to the inner diameter of the sleeve hole 311. The first land 21 is located at a first end of the spool 2, and the second land 22 is located at a second end of the spool 2. The first end of the spool 2 is the right end in FIG. 1, and the second end of the spool 2 is the end opposite to the first end, which is the left end in FIG. 1. As the spool 2 reciprocates along the axis X, the first land 21 and the second land 22 open and close the multiple ports 32. This allows the spool valve 1 to switch the path of the hydraulic oil.

[0051] The second land 22 of the spool 2 has a second end face 25. The second end face 25 is the face of the second land 22 on the spring 34 side and is a face perpendicular to the axis X. In the illustrated spool 2, the outer diameter of the second end face 25 is smaller than the outer diameter of the second land 22, and as shown in FIG. 1, a step 210 is formed on the outer periphery of the second end face 25. The above-mentioned spring 34 abuts against the second end face 25. The spring 34 biases the spool 2 to the right in FIG. 1.

[0052] The first land 21 of the spool 2 has a first end face 24. The first end face 24 is a face of the first land 21 opposite to the spring 34 and perpendicular to the axis X.

[0053] The housing 3 has a locking surface 35. The locking surface 35 is a surface perpendicular to the axis X and is a surface that locks with the first end surface 24. When the spring 34 urges the spool 2 to the right in FIG. 1, the first end surface 24 and the locking surface 35 lock with each other, thereby restricting the spool 2 from moving further to the right. The position of the spool 2 where the first end surface 24 and the locking surface 35 lock with each other is the neutral position of the spool 2. The spring 34 urges the spool 2 so that the spool 2 is in the neutral position.

[0054] A rod 23 is connected to the first land 21 of the spool 2. More specifically, the rod 23 is connected to a first end surface 24. Therefore, the first end surface 24 has an annular shape, as shown in FIG.

[0055] Here, the pressure-receiving area of ​​the first side of the spool 2 is equal to the pressure-receiving area of ​​the second side in the direction along the axis X. The pressure-receiving area of ​​the first side is the total area of ​​the annular first end face 24 and the end face of the rod 23 (the surface against which a cam 421 described later comes into contact), and the pressure-receiving area of ​​the second side is the total area of ​​the circular second end face 25 and the step 210 on the outer periphery of the second end face 25. As a result, the hydraulic load acting on the first side of the spool 2 is equal to the hydraulic load acting on the second side, and the hydraulic load acting on the spool 2 in the direction along the axis X is substantially cancelled out.

[0056] The spool 2 and the rod 23 are integrated. The rod 23 extends from the first end surface 24 in the opposite direction to the spring 34. The rod 23 passes through a through hole 36 formed in the locking surface 35 and protrudes outside the sleeve hole 311.

[0057] The electric device 4 has an electric motor 41 and a conversion mechanism 42. The conversion mechanism 42 converts the torque of the electric motor 41 into the movement of the spool 2 in the direction along the axis X. Specifically, the conversion mechanism 42 has a cam 421 attached to the shaft 411 of the electric motor 41. The shaft 411 extends in a direction perpendicular to the axis X. The cam 421 abuts against the end of the rod 23. When the electric motor 41 is driven to rotate the cam 421 and the peak of the cam 421 moves toward the spring 34, the peak of the cam 421 pushes the rod 23 toward the spring 34. As a result, the spool 2 moves toward the spring 34 against the biasing force of the spring 34 and the friction of the moving spool 2. Also, when the peak of the cam 421 moves in the opposite direction to the spring 34 due to the rotation of the cam 421, the biasing force of the spring 34 moves the spool 2 in the opposite direction to the spring 34. Thus, the spool 2 reciprocates along the axis X within the sleeve hole 311 .

[0058] The electric device 4 is not limited to the combination of the electric motor 41 and the conversion mechanism 42. The conversion mechanism 42 is not limited to a mechanism using the cam 421.

[0059] (Structure of the first end face) 2 and 3, the first end surface 24 of the spool valve 1 has projections and recesses. More specifically, a shim 5 is fixed to the first end surface 24. The shim 5 is a flat plate having a smaller diameter than the first end surface 24 and a predetermined thickness t. The shim 5 has an insertion hole 51 into which the rod 23 of the spool 2 is inserted, and has a notch 52 extending in the radial direction and connected to the insertion hole 51. The shim 5 has a C-shape as a whole.

[0060] By fixing the shim 5 to the first end face 24, when the spool 2 is biased by the spring 34, the surface of the shim 5 comes into direct contact with the locking surface 35 (see also FIG. 2). Therefore, when the spool 2 is in the neutral position, a gap 61 extending along the periphery of the first end face 24 is formed between the first end face 24 and the locking surface 35, and a gap 62 extending in the radial direction of the first end face 24 is formed at the cutout 52. In addition, the insertion hole 51 communicates with the through hole 36.

[0061] As shown in FIG. 8, when the first end face 240 and the locking surface 350 are in close contact with each other as flat surfaces over the entire surfaces of the first end face 240 and the locking surface 350, it is difficult to supply hydraulic oil between the first end face 240 and the locking surface 350, or it takes a long time to supply hydraulic oil between them.

[0062] In contrast, as shown in Figure 2, when a shim 5 is interposed between the first end face 24 and the locking surface 35 to provide unevenness, hydraulic oil is more likely to be supplied between the first end face 24 and the locking surface 35 from the through hole 36 through the gaps 61, 62 formed between the first end face 24 and the locking surface 35.

[0063] As a result, the hydraulic load acting on the first side of the spool 2 and the hydraulic load acting on the second side thereof become equal or approximately equal, and the force pressing the first end face 24 against the locking face 35 is weakened. The electric device 4 can stably move the spool 2.

[0064] Even if the temperature of the hydraulic oil drops and its viscosity increases, the hydraulic oil is supplied or is quickly supplied between the first end surface 24 and the locking surface 35. The spool valve 1 operates stably even at low temperatures. The spool valve 1 is useful as a spool valve 1 for aircraft.

[0065] In addition, since the force pressing the first end face 24 against the locking face 35 is weakened, it is sufficient for the electric device 4 to have the ability to resist the biasing force of the spring 34 and the movement resistance of the spool 2. A small electric motor 41 can be used for the spool valve 1. The spool valve 1 is made smaller. The small spool valve 1 is suitable for spool valves for various moving bodies, including aircraft.

[0066] (Modification) The above-mentioned shim 5 may be fixed to the locking surface 35 of the housing 3 instead of being fixed to the first end surface 24 of the spool 2. Also, the first end surface 24 of the spool 2 may be cut into a shape as shown in Fig. 3, so that the spool 2 has a structure similar to that in which the shim 5 is fixed to the first end surface 24.

[0067] 3. However, the radially extending notch 52 forms a gap 62 between the first end face 24 and the locking surface 35, which is continuous with the through hole 36 of the housing 3 through the insertion hole 51 and extends in a direction perpendicular to the axis X. Therefore, the hydraulic oil is quickly supplied between the first end face 24 and the locking surface 35.

[0068] The technology disclosed herein is characterized in that at least one of the first end face 24 and the locking face 35 has projections and recesses, and the projections and recesses form a gap through which hydraulic oil flows between the first end face 24 and the locking face 35. The projections and recesses can be formed without using the shim 5.

[0069] Instead of interposing the shim 5 between the first end face 24 and the locking surface 35, a recess recessed from the first end face 24 may be formed in the first end face 24, as shown in Fig. 4 for example. The shape of the recess may be various shapes.

[0070] For example, as illustrated in Fig. 4(a), a plurality of grooves 71 extending in the radial direction of the first end face 24 may be formed radially. In addition, instead of forming a plurality of grooves radially, for example, as illustrated in Fig. 4(b), one or a plurality of grooves 72 extending in a specific direction may be formed in the first end face 24. Furthermore, one or a plurality of grooves extending in the circumferential direction may be formed in the first end face 24. Furthermore, a plurality of grooves extending in random directions may be formed in the first end face 24.

[0071] As shown in FIG. 4(c), a plurality of recesses 73 may be formed in the first end face 24 in the circumferential direction thereof, lined up at intervals.

[0072] The shape of the recess may be other than that exemplified in FIG.

[0073] When the first end face 24 and the locking surface 35 are engaged with each other, these recesses 71, 72, and 73 formed in the first end face 24 do not come into contact with the locking surface 35, forming a gap. The hydraulic oil is supplied between the first end face 24 and the locking surface 35 through these recesses 71, 72, and 73.

[0074] Furthermore, flat surfaces abut against each other at locations where the recesses 71, 72, and 73 are not formed on the first end surface 24 and the locking surface 35. This makes it possible to determine the neutral position of the spool 2 with high accuracy.

[0075] Instead of forming the recesses 71, 72, and 73 in the first end face 24, a protrusion protruding from the first end face 24 may be formed in the first end face 24, as shown in Fig. 5 for example. The shape of the protrusion may be of various shapes.

[0076] For example, as illustrated in Fig. 5(a), a plurality of ridges 81 extending in the radial direction of the first end face 24 may be formed radially. In addition, the present invention is not limited to forming a plurality of ridges radially, and for example, as illustrated in Fig. 5(b), one or more ridges 82 extending in a specific direction may be formed on the first end face 24. Furthermore, one or more ridges extending in the circumferential direction may be formed on the first end face 24. Furthermore, a plurality of ridges extending in random directions may be formed on the first end face 24.

[0077] As illustrated in FIG. 5(c), a plurality of protrusions 83 may be formed in the circumferential direction of the first end face 24, lined up at intervals.

[0078] The shape of the convex portion may be other than that exemplified in FIG.

[0079] These protrusions 81, 82, and 83 formed on the first end face 24 come into contact with the locking surface 35, so that gaps are formed in the first end face 24 and the locking surface 35 at locations where no protrusions are formed. The hydraulic oil is supplied between the first end face 24 and the locking surface 35 through these gaps.

[0080] Furthermore, the protrusions 81, 82, and 83 come into contact with the locking surface 35, so that the neutral position of the spool 2 is determined with high precision.

[0081] Instead of the first end face 24 of the spool 2 having projections and recesses, the locking surface 35 of the housing 3 may have projections and recesses. For example, as shown in Fig. 6, a plurality of radially extending grooves 91 may be formed radially in the locking surface 35 as recesses formed in the locking surface 35. The grooves 91 may be connected to the through holes 36.

[0082] The recesses formed on the locking surface 35 may have various shapes as shown in Figures 4(a), (b), and (c). Also, protrusions as shown in Figures 5(a), (b), and (c) may be formed on the locking surface 35.

[0083] Moreover, each of the first end face 24 and the locking face 35 may have projections and recesses. However, in order to determine the neutral position of the spool 2, it is preferable that the first end face 24 and the locking face 35 have flat surfaces that abut against each other at least in part.

[0084] 1 and 2, the housing body 33 has the locking surface 35, but when the sleeve 31 has a lid portion 37 that closes the opening at its end as illustrated in Fig. 7, the lid portion 37 forms the locking surface 38 that locks with the first end surface 24 of the spool 2. In this case, the locking surface 38 of the lid portion 37 may be formed with, for example, a groove 91 similar to that shown in Fig. 6 or various recesses / projections. Also, a shim 5 may be fixed to the locking surface 38 of the lid portion 37.

[0085] Incidentally, instead of forming various recesses / protrusions on the engagement surface 38 of the lid portion 37, various recesses / protrusions may be formed on the first end face 24, or a shim 5 may be fixed against the engagement surface 38.

[0086] The spool valve may be of a double-acting type. The double-acting type spool valve includes a second electric device instead of the spring 34. The second electric device is connected to the second end face 25 of the spool 2. The housing 3 has a (first) locking surface 35 that locks to the first end face 24 of the spool 2, and a second locking surface that locks to the second end face 25 of the spool 2. In the double-acting type spool valve, at least one of the first end face 24 and the first locking surface 35 may have unevenness, and at least one of the second end face 25 and the second locking surface may have unevenness. Since the hydraulic oil is easily supplied to the gap between the first end face 24 and the first locking surface 35 and the gap between the second end face 25 and the second locking surface, the load due to the hydraulic pressure acting on the first end face 24 of the spool 2 and the load due to the hydraulic pressure acting on the second end face 25 become equal or approximately equal. The double acting spool valve operates stably. [Explanation of symbols]

[0087] 1 Spool valve 2 Spools 24 1st end face 25 Second end face 3. Housing 311 Sleeve hole 34 Spring 35 Locking surface 4. Electric Devices 5. Sim 52 Notch 71 Groove (recess) 72 Groove (recess) 73 Hole (recess) 81 Convex stripe (convex part) 82 Convex stripe (convex part) 83 Protrusion (convex part) 91 Groove (recess) X-axis

Claims

1. A spool valve that switches the path of hydraulic fluid, Spool and A housing having a sleeve hole into which the spool is inserted and which houses the spool so as to be able to reciprocate along its axis, The system includes an electric device connected to the spool and which switches the path of the hydraulic fluid by moving the spool along the shaft, The spool has a first end face of a first land located at the first end in the direction along the axis, and has a first end face perpendicular to the axis. The housing has a locking surface perpendicular to the axis that engages with the first end face of the spool, The first land has an outer diameter corresponding to the inner diameter of the sleeve hole, At least one of the first end face and the locking face has irregularities, The aforementioned irregularities supply hydraulic fluid between the first end face and the locking surface, and the hydraulic pressure acting on the first side of the spool due to the hydraulic fluid supplied between the first end face and the locking surface is maintained within the housing of the spool valve.

2. In the spool valve according to claim 1, A spool valve in which a recess is formed in at least one of the first end face and the locking face, recessed from the surface.

3. In the spool valve according to claim 1, A spool valve having a protrusion formed on at least one of the first end face and the locking face, which protrudes from the surface.

4. In the spool valve according to claim 1, A spool valve in which a shim interposed between the first end face and the locking surface is fixed to the first end face or the locking surface.

5. In the spool valve according to claim 4, A spool valve in which the shim has a notch formed therein that extends in a direction perpendicular to the shaft.

6. In the spool valve according to claim 1, The device further includes a spring that strikes a second end face opposite to the first end face in the direction along the aforementioned axis, thereby biasing the spool to a neutral position. The electric device is a spool valve connected to the first end face of the spool and moves the spool in a direction that separates the first end face from the locking surface, against the biasing force of the spring.

7. In the spool valve according to claim 6, The spool has a second land on the second side opposite to the first side in the direction along the shaft, which has a second end face and an outer diameter corresponding to the inner diameter of the sleeve hole. A spool valve having a housing that accommodates the spring and maintains the hydraulic pressure acting on the second side of the spool, and having a housing space isolated from the outside of the housing.

8. In the spool valve according to any one of claims 1 to 7, A spool valve, intended for aircraft.

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