JP6734825B2 - Spool valve device - Google Patents

Description

The present invention relates to a spool valve device used as, for example, a direction control valve, a pressure control valve, a flow rate control valve, etc. of a hydraulic system (hydraulic pressure system) mounted on a construction machine such as a hydraulic excavator.

Generally, a construction machine such as a hydraulic excavator, a hydraulic crane, a wheel loader, or the like is equipped with a hydraulic system (fluid pressure system) also called a hydraulic drive device (hydraulic drive device). Such a hydraulic system includes, for example, a hydraulic source (hydraulic pressure source) such as a hydraulic pump, a hydraulic motor (hydraulic actuator) such as a hydraulic motor and a hydraulic cylinder driven by pressure oil supplied from the hydraulic source, It is configured to include a spool valve (spool valve device) such as a directional control valve that is provided between the hydraulic power source and the hydraulic actuator and that switches the supply and discharge of the pressure oil to and from the hydraulic actuator.

Here, the spool valve used in the hydraulic system plays a role of controlling the flow rate, pressure and direction of the hydraulic system by adjusting the opening amount by axially displacing a valve element called a spool in accordance with an input command. have. When a liquid such as hydraulic oil passes through the spool valve, a force may be generated in the axial rotation direction of the spool due to the viscous resistance and dynamic pressure (so-called fluid force) of the liquid, and the spool may rotate.

In this case, if the spool continues to rotate, the sliding portion between the spool and the housing may be worn. Then, if this wear progresses, there is a risk that the flow loss may increase due to leakage between the spool and the housing, and the device life may be shortened due to the deformation of the spool. Further, the abrasion powder generated by abrasion is caught in the sliding portion, which may cause the spool to stick (fix). In this case, control of the hydraulic circuit may be lost.

As a technique for solving these problems, for example, Patent Document 1 describes a spool valve provided with a rotation restricting portion that restricts rotation of a spool. This spool valve has a structure that allows the spool to freely slide in the axial direction and restricts only the rotation direction. That is, it is possible to prevent the spool from rotating regardless of the axial position of the spool. According to this technique, it is considered that the rotation of the spool can be prevented by the rotation restricting portion and the wear of the spool sliding portion can be reduced.

However, in the case of the technique described in Patent Document 1, the spool has a rotation restricting portion at the end, and the spool is provided with a notch called a notch for improving flow rate control performance and preventing oil hammering. Has been. Then, when the fluid (hydraulic oil) passes through this notch, the flow velocity sharply increases according to Bernoulli's law, and at the same time, the pressure sharply decreases. At this time, when the pressure of the liquid becomes lower than the saturated vapor pressure determined by the type (liquid type) of the liquid due to this rapid pressure decrease, bubbles are generated in the liquid and cavitation occurs to expand. ..

Furthermore, the bubbles generated in the notch (throttle portion) ride on the high-speed fluid jet and are made to flow to the downstream portion of the notch. At this time, since the pressure in the downstream portion becomes higher than that in the notch in which cavitation occurs, the pressure around the bubble gradually recovers, and the bubble is eventually crushed by this recovered pressure. At the moment when the bubbles are crushed and collapsed, a high impact pressure is locally generated, which may damage the surface of the device member and cause erosion.

In the technique of Patent Document 1, since the spool does not rotate, the cavitation jet generated at the notch continues to collide with the housing wall surface on the downstream side, which may cause erosion on the housing wall surface. Moreover, since the cavitation jet continues to be concentrated and ejected at the same position, the progress of erosion (corrosion speed) is fast, which may shorten the life of the device excessively.

In order to solve such an erosion problem, for example, the technique described in Patent Document 2 may be adopted. Patent Document 2 describes a technique for suppressing the occurrence of erosion by forming a part in which valve cavitation occurs with a material having high erosion resistance and high hardness.

JP-A-03-163274 (Patent No. 2873841) JP 2010-5495 A (Patent No. 5540475)

As described above, the spool valve has a trade-off relationship between erosion and wear due to rotation of the spool. When the rotation of the spool is restricted to suppress the wear due to the rotation as in the technique of Patent Document 1, the rotational position of the notch is fixed, so that erosion may easily occur. Here, for example, the use of the material (material) having high erosion resistance described in Patent Document 2 can be cited as an effective countermeasure. However, a material with high erosion resistance is more expensive than a commonly used material (for example, iron), and it is necessary to use the material for a part (for example, a housing) where erosion is predicted to occur. May lead to a decrease in spool valve productivity and an increase in cost.

An object of the present invention is to provide a spool valve device that can improve the life while suppressing the increase in cost.

A spool valve device of the present invention includes a cylindrical housing having a spool sliding hole, and a plurality of ports provided in the axial direction of the spool sliding hole with a switching portion interposed therebetween, and a spool sliding hole of the housing. Located at the boundary between the land and the oil groove of the spool, and a spool in which the oil groove and the land are axially separated from each other so as to communicate or block between the ports. In the spool valve device, which is provided on the land and has a notch that allows the ports to communicate with each other at a small flow rate at a cracking position that allows the ports to communicate with each other when the spool moves, wherein the inner peripheral surface of the low-pressure side port hydraulic oil flowing from the high pressure side port when communicating via notches collide, at least one bottomed bubble reservoir consisting of a small hole is provided, the bubble reservoir Is D, the diameter of bubbles generated by cavitation when hydraulic oil passes through the notch is Db, and the bubbles are ejected from the notch toward the inner peripheral surface of the low-pressure side port. When the diameter of the jet is Dc and the depth of the small hole from the inner peripheral surface of the low-pressure side port is L, the hole diameter D of the small hole is larger than the diameter Db of the bubble and the diameter of the jet. It is set to be smaller than Dc, and the depth L of the small hole is set to be larger than the hole diameter D of the small hole .

According to the present invention, it is possible to improve life while suppressing an increase in cost. That is, at least one small hole is provided on the wall surface of the housing on which the cavitation jet collides. The small holes serve as a bubble reservoir due to the inclusion of bubbles due to cavitation inside, and a turbulent flow field can be formed on the opening side of the small holes. That is, at the jet collision portion where the cavitation jet collides, at least one small hole provided on the wall surface of the housing forms a bubble reservoir and a turbulent flow field. As a result, it is possible to induce (cause) the collapse of the bubbles and the flow that reduces the impact pressure at the time of the collapse in the jet collision portion, and it is possible to suppress the occurrence of erosion. As a result, the life can be improved while suppressing the cost increase due to the material change.

It is a front view showing a hydraulic excavator in which the spool valve device by a 1st embodiment is carried. FIG. 6 is a hydraulic circuit diagram for driving a hydraulic actuator showing a lever operating device, a spool valve device, and the like. It is a longitudinal section showing a spool valve device in which a spool is in a neutral position. FIG. 4 is an enlarged cross-sectional view corresponding to part (IV) in FIG. 3 when the spool is displaced to the right from the neutral position. It is the arrow line view seen from the arrow V direction in FIG. It is explanatory drawing (cross section) which shows the relationship between a cavitation jet and a small hole. It is an important section sectional view showing a spool valve device by a 2nd embodiment. FIG. 8 is a view seen from the direction of the arrow VIII in FIG. 7.

Hereinafter, an embodiment of the spool valve device of the present invention will be described in detail with reference to the accompanying drawings, taking a case where the embodiment is applied to a directional control valve mounted on a hydraulic excavator as an example.

1 to 6 show a first embodiment. In FIG. 1, a hydraulic excavator 1 that is a typical example of a construction machine includes a crawler-type lower traveling body 2 that is self-propelled, a turning device 3 that is provided on the lower traveling body 2, and a turning structure that moves on the lower traveling body 2. It is configured to include an upper revolving structure 4 which is rotatably mounted via a device 3, and a working device 5 of an articulated structure which is provided on the front side of the upper revolving structure 4 and which performs excavation work and the like. In this case, the lower traveling body 2 and the upper revolving body 4 form the vehicle body of the hydraulic excavator 1.

The lower traveling body 2 is configured to include, for example, a crawler belt 2A and left and right traveling hydraulic motors (not shown) that cause the hydraulic excavator 1 to travel by orbitally driving the crawler belt 2A. The lower traveling body 2 rotates the traveling hydraulic motor, which is a hydraulic motor (hydraulic actuator), based on the supply of pressure oil from a main hydraulic pump 13 (see FIG. 2), which will be described later. It travels with the working device 5.

The work device 5, which is also called a work machine or a front, includes, for example, a boom 5A, an arm 5B, a bucket 5C as a work tool, and a boom cylinder 5D, an arm cylinder 5E, and a bucket cylinder as hydraulic actuators (hydraulic actuators) for driving these. (Working tool cylinder) 5F. The work device 5 moves downward (oscillates) by expanding or contracting the cylinders 5D, 5E, 5F, which are hydraulic cylinders, based on the supply of pressure oil from the main hydraulic pump 13 (see FIG. 2). In the hydraulic circuit diagram of FIG. 2, which will be described later, in order to avoid complicating the drawing, the hydraulic circuit mainly relating to the boom cylinder 5D is shown, and the arm cylinder 5E, the bucket cylinder 5F, and the left and right traveling directions described above. The hydraulic circuit for the hydraulic motor for turning and the hydraulic motor for turning described later is omitted.

The upper revolving structure 4 is mounted on the lower traveling structure 2 via a revolving device 3 including a revolving bearing, a revolving hydraulic motor, a speed reducing mechanism, and the like. The upper swing body 4 works on the lower traveling body 2 by rotating a swing hydraulic motor, which is a hydraulic motor (hydraulic actuator), based on the supply of pressure oil from the main hydraulic pump 13 (see FIG. 2). Swirl with device 5. The upper swing body 4 is configured to include a swing frame 6 serving as a support structure (base frame) for the upper swing body 4, a cab 7 mounted on the swing frame 6, a counterweight 8, and the like. In this case, in addition to the engine 12, the hydraulic pumps 13 and 19, the hydraulic oil tank 14 and the like shown in FIG. 2 are mounted on the swing frame 6.

The revolving frame 6 is attached to the lower traveling body 2 via the revolving device 3. On the left side of the front part of the revolving frame 6, a cab 7 whose inside is a cab is provided. A counterweight 8 is provided on the rear end side of the revolving frame 6 to balance the weight with the working device 5. Between the cab 7 and the counterweight 8 is a machine room 9 in which the engine 12, hydraulic pumps 13 and 19 (see FIG. 2) and the like are housed. Further, a control valve device 21 described later is installed at substantially the center (center) of the upper revolving structure 4 (revolving frame 6).

Here, inside the cab 7, a driver's seat (not shown) in which an operator is seated is provided. An operating device for operating the hydraulic excavator 1 (only the boom lever operating device 22 is shown in FIG. 2) is provided around the driver's seat. The operation device includes, for example, left and right traveling lever/pedal operation devices provided on the front side of the driver's seat, and left and right work lever operation devices provided on both left and right sides of the driver's seat, respectively. It is configured.

The left and right traveling lever/pedal operation devices are operated by an operator when the lower traveling structure 2 is traveling. The left and right work lever operating devices are operated by an operator when operating the work device 5 and when rotating the upper swing body 4. In the hydraulic circuit diagram of FIG. 2, which will be described later, a boom lever operating device 22 for operating (swinging) the boom 5A of the working device 5 among various operating devices (traveling operating device and working operating device). Only the left and right traveling lever/pedal operating devices, turning lever operating devices, arm lever operating devices, bucket lever operating devices, etc. are omitted. The boom lever operation device 22 corresponds to, for example, an operation in the front-rear direction of the work lever operation device on the right side.

The operating device sends a pilot signal (pilot pressure) according to an operator's operation (lever operation, pedal operation) to a control valve device 21 including a plurality of directional control valves (only the boom directional control valve 31 is shown in FIG. 2). Output. Thus, the operator can operate (drive) the traveling hydraulic motor, the cylinders 5D, 5E, 5F of the working device 5 and the revolving hydraulic motor of the revolving device 3. In the hydraulic circuit diagram of FIG. 2, which will be described later, only the boom directional control valve 31 among the plurality of directional control valves forming the control valve device 21 is shown (for example, the left traveling directional control valve, the right traveling directional control valve). Direction control valve, turning direction control valve, arm direction control valve, bucket direction control valve, etc. are omitted).

Next, a hydraulic drive device (hydraulic system) for driving the hydraulic excavator 1 will be described with reference to FIG. 2 as well as FIG.

As shown in FIG. 2, the hydraulic excavator 1 includes a hydraulic circuit 11 that operates (drives) the hydraulic excavator 1 based on the pressure oil supplied from the hydraulic pump 13. The hydraulic circuit 11 is configured to include a main hydraulic circuit 11A including a hydraulic actuator (hereinafter, also simply referred to as a cylinder 5D) and a pilot hydraulic circuit 11B for operating the cylinder 5D.

That is, the hydraulic circuit 11 includes a cylinder 5D, an engine 12 (see FIG. 1), a main hydraulic pump 13, a hydraulic oil tank 14 as a tank, a pilot hydraulic pump 19, a control valve device 21 (boom direction control). The valve 31) and an operating device (hereinafter, also simply referred to as lever operating device 22) are included. In addition to the cylinder 5D, the main hydraulic circuit 11A of the hydraulic circuit 11 includes an engine 12, a main hydraulic pump 13, a hydraulic oil tank 14, a control valve device 21 (a boom directional control valve 31), and a pump line. A main discharge pipe line 15, a return pipe line 16 as a tank pipe line, a bottom side pipe line 17 as one side actuator pipe line, and a rod side pipe line 18 as another side actuator pipe line. There is. On the other hand, the pilot hydraulic circuit 11B of the hydraulic circuit 11 includes an engine 12, a pilot hydraulic pump 19, a hydraulic oil tank 14, a lever operating device 22, a pilot discharge pipeline 20, and an extension side as a one-side pilot pipeline. The pilot line 23 and the reduction side pilot line 24 as the other side pilot line are provided.

The engine 12 (see FIG. 1) is mounted on the swing frame 6. The engine 12 is composed of an internal combustion engine such as a diesel engine. A main hydraulic pump 13 and a pilot hydraulic pump 19 are attached to the output side of the engine 12. The hydraulic pumps 13 and 19 are rotationally driven by the engine 12. The drive source (power source) for driving the hydraulic pumps 13 and 19 can be constituted by the engine 12 alone which is the internal combustion engine, or may be constituted by, for example, the engine and the electric motor or the electric motor alone. ..

The main hydraulic pump 13 is mechanically (that is, capable of transmitting power) to the engine 12. The main hydraulic pump 13 supplies pressure oil to the main hydraulic circuit 11A including the cylinder 5D. The main hydraulic pump 13 is configured by, for example, a variable displacement hydraulic pump, more specifically, a variable displacement swash plate type, oblique shaft type, or radial piston type hydraulic pump. Although the main hydraulic pump 13 is shown as a single hydraulic pump in FIG. 2, it may be composed of, for example, two or more hydraulic pumps.

The main hydraulic pump 13 is connected to the cylinder 5D via a control valve device 21 (boom directional control valve 31). The main hydraulic pump 13 supplies pressure oil to the cylinder 5D. Although not shown, the main hydraulic pump 13 supplies pressure oil to, for example, the traveling hydraulic motor, the turning hydraulic motor, the arm cylinder 5E, and the bucket cylinder 5F in addition to the boom cylinder 5D.

The main hydraulic pump 13 discharges the hydraulic oil stored in the hydraulic oil tank 14 to the main discharge pipeline 15 as pressure oil. The pressure oil discharged to the main discharge pipe line 15 is supplied to (the bottom side oil chamber or the rod side oil chamber of) the boom cylinder 5D via the control valve device 21 (the boom direction control valve 31), and the boom cylinder 5D. The pressure oil in (the rod-side oil chamber or the bottom-side oil chamber) returns to the hydraulic oil tank 14 via the control valve device 21 (the boom direction control valve 31) and the return pipe line 16. As described above, the main hydraulic pump 13 constitutes a main hydraulic pressure source together with the hydraulic oil tank 14 that stores hydraulic oil.

Like the main hydraulic pump 13, the pilot hydraulic pump 19 is mechanically connected to the engine 12. The pilot hydraulic pump 19 supplies pressure oil to the pilot hydraulic circuit 11B for operating the cylinder 5D. The pilot hydraulic pump 19 is configured by, for example, a fixed displacement gear pump or a swash plate hydraulic pump. The pilot hydraulic pump 19 discharges the hydraulic oil stored in the hydraulic oil tank 14 to the pilot discharge pipeline 20 as pressure oil. That is, the pilot hydraulic pump 19 constitutes a pilot hydraulic power source together with the hydraulic oil tank 14.

The pilot hydraulic pump 19 is connected to the lever operating device 22. The pilot hydraulic pump 19 supplies pressure oil (primary pressure) to the lever operating device 22. In this case, the pressure oil of the pilot hydraulic pump 19 is supplied to the control valve device 21 (the hydraulic pilot portions 31A and 31B of the boom directional control valve 31) via the lever operating device 22.

The control valve device 21 is a control valve group including a plurality of directional control valves including a boom directional control valve 31. The control valve device 21 controls the pressure oil discharged from the main hydraulic pump 13 according to the operation of various operating devices including the boom lever operating device 22, the boom cylinder 5D, the arm cylinder 5E, the bucket cylinder 5F, and the traveling cylinder. It is distributed to the hydraulic motor and the turning hydraulic motor. In the following description, the boom directional control valve 31 (hereinafter, also simply referred to as the directional control valve 31) will be described as a representative example of the control valve device 21.

The direction control valve 31 controls the direction of the pressure oil supplied from the main hydraulic pump 13 to the cylinder 5D according to the switching signal (pilot pressure) by the operation of the lever operating device 22 arranged in the cab 7. As a result, the cylinder 5D is driven (extended or contracted) by the pressure oil (operating oil) supplied (discharged) from the main hydraulic pump 13. The directional control valve 31 is configured by a pilot operated directional control valve, for example, a 5-port 3-position (or 6-port 3-position, 4-port 3-position) hydraulic pilot type directional control valve.

The directional control valve 31 extends or contracts the cylinder 5D by switching supply and discharge of pressure oil to and from the cylinder 5D between the main hydraulic pump 13 and the cylinder 5D. A switching signal (pilot pressure) based on the operation of the lever operating device 22 is supplied to the hydraulic pilot portions 31A and 31B of the directional control valve 31. As a result, the directional control valve 31 is switched from the neutral position (A) to the switching positions (B) and (C).

The lever operating device 22 is arranged in the cab 7 of the upper swing body 4. The lever operating device 22 is composed of, for example, a lever type pressure reducing valve type pilot valve. Pressure oil (primary pressure) from the pilot hydraulic pump 19 is supplied to the lever operating device 22 through the pilot discharge pipe line 20. The lever operating device 22 outputs a pilot pressure (secondary pressure) according to the lever operation of the operator to the directional control valve 31 via the extension side pilot conduit 23 or the contraction side pilot conduit 24.

That is, the lever operating device 22 is operated by the operator to supply (output) a pilot pressure proportional to the operation amount to the hydraulic pilot portions 31A and 31B of the directional control valve 31. For example, when the lever operating device 22 is operated in the direction of extending the cylinder 5D (that is, when the raising operation for raising the boom 5A is performed), the pilot pressure generated by this operation is the extension side pilot pipe line 23. Is supplied to the hydraulic pilot portion 31A of the directional control valve 31 via. As a result, the directional control valve 31 switches from the neutral position (A) to the switching position (B), and the pressure oil from the main hydraulic pump 13 is supplied to the bottom oil chamber of the cylinder 5D via the bottom pipe line 17. Then, the pressure oil in the rod-side oil chamber of the cylinder 5D returns to the hydraulic oil tank 14 via the rod-side conduit 18 and the return conduit 16.

On the other hand, for example, when the lever operating device 22 is operated in the direction of reducing the cylinder 5D (that is, when the lowering operation for lowering the boom 5A is performed), the pilot pressure generated by this operation is reduced. It is supplied to the hydraulic pilot portion 31B of the directional control valve 31 via the side pilot conduit 24. As a result, the directional control valve 31 switches from the neutral position (A) to the switching position (C), and the pressure oil from the main hydraulic pump 13 is supplied to the rod side oil chamber of the cylinder 5D via the rod side conduit 18. Then, the pressure oil in the bottom side oil chamber of the cylinder 5D returns to the hydraulic oil tank 14 via the bottom side pipeline 17 and the return pipeline 16.

Next, the direction control valve 31 as the spool valve device will be described with reference to FIGS. 3 and 6 in addition to FIGS. 1 and 2.

The direction control valve 31 is provided between the hydraulic power source (the main hydraulic pump 13 and the hydraulic oil tank 14) and the hydraulic actuator (cylinder 5D). The directional control valve 31 slidably displaces the spool 41 from the neutral position shown in FIG. 2A to the switching position shown in FIG. 2B or 2C, thereby supplying or discharging the pressure oil to or from the cylinder 5D. Control direction and flow rate. The direction control valve 31 is formed symmetrically in the axial direction of the spool 41 with the pump port 38 as a boundary. The directional control valve 31 includes a housing 32, a spool 41, left and right caps 45A and 45B, left and right springs 47A and 47B, and left and right rotation restricting portions 48A and 48B. ing.

The housing 32 constitutes the valve body of the directional control valve 31. As shown in FIG. 3, the housing 32 is formed in a tubular shape, and a spool sliding hole 33 is formed on the inner peripheral side of the housing 32. In other words, the housing 32 has a spool sliding hole 33 extending in the axial direction (left and right directions in FIG. 2). On one side (left side in FIG. 2) of the housing 32, a left cap 45A as one cap is attached so as to face one side opening (left side opening) of the spool sliding hole 33. On the other side (right side in FIG. 2) of the housing 32, a right cap 45B as the other cap is attached so as to face the other side opening (right side opening) of the spool sliding hole 33.

A central concave groove 34 is formed in the axial center of the spool sliding hole 33. A left side groove 35</b>A as one side groove is formed on one side (left side) in the axial direction of the spool sliding hole 33 with respect to the central groove 34. Further, a left end side concave groove 36A as one end side concave groove is provided on one side in the axial direction of the spool sliding hole 33 relative to the left side concave groove 35A, that is, on one end side (left end side) of the spool sliding hole 33. Has been formed. On the other hand, on the other side (right side) in the axial direction of the spool slide hole 33 with respect to the central groove 34, a right side groove 35B as another side groove is formed. Further, on the other side in the axial direction of the right side groove 35B of the spool sliding hole 33, that is, on the other end side (right end side) of the spool sliding hole 33, a right end side concave groove as the other end side concave groove. 36B is formed.

Each of these recessed grooves 34, 35A, 35B, 36A, 36B is formed in an annular shape over the entire circumference of the spool sliding hole 33. The recessed grooves 34, 35A, 35B, 36A, 36B are provided so as to be separated from each other in the axial direction of the spool sliding hole 33. In this case, switching portions 37, 37 are formed between the respective concave grooves 34, 35A, 35B, 36A, 36B so as to project over the entire circumference toward the inner diameter side of the spool sliding hole 33.

Further, the housing 32 is provided with five ports, that is, a pump port 38, a pair of actuator ports 39A and 39B, and a pair of tank ports 40A and 40B, which are spaced apart from each other in the axial direction of the spool sliding hole 33. ing. The pump port 38 provided in the central portion of the housing 32 in the axial direction is connected to the main discharge pipe line 15 on one side opening to the outer surface of the housing 32, and to the central concave groove 34 on the other side opening to the spool sliding hole 33. It is in communication.

The left actuator port 39A, which is one (left) actuator port of the pair of actuator ports 39A and 39B, is connected to the bottom side conduit 17 on one side that opens to the outer surface of the housing 32 and opens to the spool sliding hole 33. The other side that communicates with the left recessed groove 35A. On the other hand, in the right actuator port 39B as the other (right) actuator port, one side opening to the outer surface of the housing 32 is connected to the rod side conduit 18, and the other side opening to the spool sliding hole 33 is the right side. It communicates with the groove 35B.

The left tank port 40A, which is one (left) tank port of the pair of tank ports 40A and 40B, is connected to the return conduit 16 at one side that opens to the outer surface of the housing 32 and opens to the spool sliding hole 33. The other side communicates with the left end side concave groove 36A. On the other hand, in the right tank port 40B as the other (right) tank port, one side opening to the outer surface of the housing 32 is connected to the return pipe line 16 and the other side opening to the spool sliding hole 33 is the right end side. It communicates with the groove 36B. Thereby, the housing 32 is provided with a plurality of ports 38, 39A, 39B, 40A, 40B in the axial direction of the spool sliding hole 33 with the switching portions 37, 37 interposed therebetween.

The spool 41 is movably (slidingly) inserted into the spool sliding hole 33 of the housing 32. The spool 41 is slidably displaced in the spool sliding hole 33 in the axial direction according to the pilot pressure supplied to the hydraulic pilot portions 31A and 31B. A central land 42 as a land (first land) is provided at an axially intermediate portion of the spool 41. Further, a left side land 43A and a right side land 43B as lands (second land and third land) are also provided on both axial ends of the spool 41. These lands 42, 43A, 43B slide axially in the spool sliding hole 33. In this case, between the lands 42, 43A, 43B, there are oil grooves 44, 44 recessed over the entire circumference toward the inner diameter side of the spool 41. That is, the spool 41 is provided with oil grooves 44, 44 and lands 42, 43A, 43B that are axially separated from each other in order to communicate or block the ports 38, 39A, 39B, 40A, 40B. ..

On one end side (left end side) of the central land 42, a plurality of notches 42A (only one is shown in FIG. 3) extending in the axial direction are formed at equal intervals in the circumferential direction. On the other end side (right end side) of the central land 42, a plurality of notches 42B (only one is shown in FIG. 3) extending in the axial direction are formed at equal intervals in the circumferential direction. These notches 42A and 42B are provided in the central land 42 at the boundary between the central land 42 and the oil groove 44. The one (left) notch 42A communicates a small amount of pressure oil that flows between the central groove 34 and the left groove 35A, that is, between the pump port 38 and the left actuator port 39A. The other (right) notch 42B communicates a small amount of pressure oil flowing between the central groove 34 and the right groove 35B, that is, between the pump port 38 and the right actuator port 39B. That is, the notches 42A, 42B allow the ports 38, 39A, 39B to communicate with each other at a small flow rate at a position (cracking position) where the ports 38, 39A, 39B communicate with each other when the spool 41 moves.

On the right end side (the other end side) of the left land 43A, a plurality of notches 43A1 (only one is shown in FIG. 3) extending in the axial direction are formed at equal intervals in the circumferential direction. The notch 43A1 is provided in the left land 43A at the boundary between the left land 43A and the oil groove 44. The notch 43A1 communicates a small amount of pressure oil that flows between the left concave groove 35A and the left end concave groove 36A, that is, between the left actuator port 39A and the left tank port 40A. That is, the notch 43A1 allows the ports 39A and 40A to communicate at a small flow rate at a position (cracking position) where the ports 39A and 40A communicate with each other when the spool 41 moves. A left protruding shaft portion 49A is provided at the left end portion (one end portion) of the left land 43A, that is, the left end portion (one end portion) of the spool 41.

On the other hand, on the left end side (one end side) of the right land 43B, a plurality of notches 43B1 (only one is shown in FIG. 3) extending in the axial direction are formed at equal intervals in the circumferential direction. The notch 43B1 is located at the boundary between the right land 43B and the oil groove 44, and is provided in the right land 43B. The notch 43B1 communicates a small amount of pressure oil that flows between the right concave groove 35B and the right end concave groove 36B, that is, between the right actuator port 39B and the right tank port 40B. That is, the notch 43B1 allows the ports 39B and 40B to communicate with each other at a small flow rate at a position (cracking position) where the ports 39B and 40B communicate with each other when the spool 41 moves. A right protruding shaft portion 49B is provided at the right end portion (other end portion) of the right land 43B, that is, at the right end portion (other end portion) of the spool 41.

Here, for example, when the spool 41 is displaced rightward from the neutral position shown in FIG. 3, the center groove 42 and the left groove 35A are separated from each other via the oil groove 44 between the center land 42 and the left land 43A. The spaces are connected. Along with this, the right side recessed groove 35B and the right end side recessed groove 36B communicate with each other via the oil groove 44 between the center land 42 and the right side land 43B. In this case, the pressure oil discharged from the main hydraulic pump 13 passes through the main discharge pipeline 15, the pump port 38, the central groove 34, the switching portion 37 and the oil groove 44, and the left groove 35A. It is guided to the left actuator port 39A and supplied to the bottom side oil chamber of the cylinder 5D via the bottom side pipe line 17. Thereby, the cylinder 5D can be extended. At this time, the pressure oil in the rod-side oil chamber of the cylinder 5D flows through the rod-side conduit 18, the right actuator port 39B, the right groove 35B, the switching portion 37 and the oil groove 44, and the right end groove 36B. It is guided to the right tank port 40B through the return line 16 and returned to the hydraulic oil tank 14 via the return line 16.

The left cap 45A is formed in a cylindrical shape with a bottom, and is attached to the housing 32 so as to close the left end opening of the spool sliding hole 33. The left cap 45A is provided with a connection port 45A1 to which the extension pilot line 23 is connected. Inside the left cap 45A is a hydraulic pilot portion 31A for slidingly displacing the spool 41 in the axial direction. A left spring receiver 46A and a left spring 47A are provided in the hydraulic pilot portion 31A. The left spring receiver 46A is fitted on the outer peripheral side of the left protruding shaft portion 49A. The left spring 47A is provided on the outer peripheral side of the left protruding shaft portion 49A between the bottom portion of the left cap 45A and the left spring receiver 46A. The left spring 47A biases the spool 41 toward the neutral position (A) via the left spring receiver 46A.

The right cap 45B is formed in a cylindrical shape with a bottom, and is attached to the housing 32 so as to close the right end opening of the spool sliding hole 33. The right cap 45B is provided with a connection port 45B1 to which the reduction side pilot conduit 24 is connected. Inside the right cap 45B is a hydraulic pilot portion 31B for slidingly displacing the spool 41 in the axial direction. A right spring receiver 46B and a right spring 47B are provided inside the hydraulic pilot portion 31B. The right spring receiver 46B is fitted on the outer peripheral side of the right protruding shaft portion 49B. The right spring 47B is provided on the outer peripheral side of the right protruding shaft portion 49B between the bottom portion of the right cap 45B and the right spring receiver 46B. The right spring 47B biases the spool 41 toward the neutral position (A) via the right spring receiver 46B.

Next, the left and right rotation restricting portions 48A and 48B for allowing the axial displacement of the spool 41 and restricting (blocking) the rotation of the spool 41 will be described. The left rotation restricting portion 48A as one rotation restricting portion and the right rotation restricting portion 48B as the other rotation restricting portion have the same configuration except that the left and right sides are different. Therefore, with respect to the right rotation restricting portion 48B, the same components as those of the left rotation restricting portion 48A are denoted by reference numeral "B", and the description thereof will be omitted.

The left rotation restricting portion 48A is provided between the left end of the spool 41 and the left cap 45A. The left rotation restricting portion 48A restricts rotation of the spool 41 in the spool sliding hole 33 when the spool 41 is displaced toward the left cap 45A side. The left rotation restricting portion 48A includes a left protruding shaft portion 49A as one protruding shaft portion and a left protruding portion 50A as one protruding portion.

The left protruding shaft portion 49A is provided at the left end of the spool 41 and protrudes axially toward the inside of the left cap 45A. The left protruding shaft portion 49A is formed of a cylindrical body and is integrally formed with the left land 43A. The left protruding shaft portion 49A is provided with an engagement groove 49A1 that engages with the left protruding portion 50A.

The left protrusion 50A is provided on the bottom of the left cap 45A. The left protrusion 50A projects from the bottom of the left cap 45A toward the engagement groove 49A1. The left protrusion 50A is formed corresponding to the engagement groove 49A1 of the left protrusion shaft portion 49A. The left protrusion 50A is formed in a plate shape, for example. The left protrusion 50A enters into the engagement groove 49A1 when the spool 41 is displaced leftward from the neutral position. As a result, the spool 41 is allowed to be displaced in the axial direction, and the rotation of the spool 41 is blocked (restricted).

By the way, when the rotation of the spool 41 is restricted, the wear of the spool 41 and the housing 32 due to the rotation of the spool 41 can be suppressed. However, in this case, for example, the positions of the notches 43A1 and 43B1 of the left and right lands 43A and 43B in the rotational direction are fixed. Therefore, the cavitation jet generated in the notches 43A1 and 43B1 tends to collide with the same position on the downstream housing wall surface. That is, the cavitation jet generated at the notch 43A1 tends to collide with the same position on the inner surface (inner peripheral surface, bottom surface) of the left end side concave groove 36A, and the cavitation jet generated at the notch 43B1 becomes the inner surface of the right end side concave groove 36B. It tends to collide with the same position (inner surface, bottom surface). As a result, erosion may easily occur on the inner surface of the left end side groove 36A and the inner surface of the right end side groove 36B.

That is, when the spool 41 is displaced to the right, the right actuator port 39B and the right tank port 40B communicate with each other via the notch 43B1 of the right land 43B of the spool 41. At this time, the cross-sectional area of the oil passage formed by this notch 43B1 becomes smaller than the cross-sectional area of the oil passage of other parts. Therefore, an increase in the flow velocity of the hydraulic oil and a decrease in the pressure occur in the notch 43B1, which may cause cavitation. Then, as shown in FIG. 6, the cavitation generated in the notch 43B1 becomes a cavitation jet 52 which is a flow of the hydraulic oil accompanied by the bubbles 51 and collides with the inner peripheral surface 36B1 of the right end side concave groove 36B. As a result, erosion may occur on the inner peripheral surface 36B1 of the right end side groove 36B. Moreover, in the case of the configuration in which the rotation of the spool 41 is restricted, the cavitation jet flow 52 is concentrated and ejected at the same position, which may accelerate the progress of erosion (erosion speed).

On the other hand, in the embodiment, on the wall surface of the housing (the inner peripheral surface 36A1 of the left end side concave groove 36A and the inner peripheral surface 36B1 of the right end side concave groove 36B), the bubble reservoir 53 including the small holes 53A and 53A having a bottom is formed. It is provided. That is, as shown in FIG. 4, the inner peripheral surface 36B1 serving as the bottom surface of the right end side groove 36B is provided with a bubble reservoir 53 composed of a plurality of bottomed small holes 53A, 53A. In this case, the inner peripheral surface 36B1 of the right end side concave groove 36B has a low pressure side against which hydraulic oil flowing from the high pressure side right actuator port 39B collides when the right actuator port 39B and the right tank port 40B communicate with each other through the notch 43B1. Corresponding to the inner peripheral surface (oil passage wall surface) on the right tank port 40B side.

In addition, as shown in FIG. 3, in the inner peripheral surface 36A1 of the left end side concave groove 36A, similarly to the inner peripheral surface 36B1 of the right end side concave groove 36B, a bubble pool composed of a plurality of bottomed small holes 53A, 53A. 53 is provided. Note that the small holes 53A and 53A of the left end side concave groove 36A have the same configuration as the small holes 53A and 53A of the right end side concave groove 36B except that the left and right sides are different, and henceforth, the small holes 53A of the right end side concave groove 36B will be mainly described below. 53A will be described as a typical example. Further, in FIGS. 3 to 6 (FIGS. 7 and 8 described later), the small holes 53A, the bubbles 51, the jet flow 52 and the like are exaggeratedly shown.

As shown in FIG. 6, the small holes 53A and 53A serve as a bubble reservoir 53 when bubbles 51 due to cavitation enter. The bubble reservoir 53 absorbs an impact pressure generated when the cavitation bubbles 51 collapse. That is, the bubbles 51 of the bubble pool 53 absorb the impact pressure of the collapsing bubbles 51, thereby attenuating the force that contributes to (participates in) the erosion. Further, a vortex 54 is generated by the liquid (working oil) flowing through the edges (opening edges) of the small holes 53A, 53A. Due to the generation of the vortex 54, the pressure field of the jet collision portion (that is, near the inner peripheral surface 36B1 of the right end side groove 36B) against which the cavitation jet 52 collides is disturbed (in other words, the pressure field near the inner peripheral surface 36B1 is disturbed. A flow field is formed). As a result, pressure recovery in the vicinity of the jet impingement portion is less likely to occur, and the generation of impact force due to the collapse of the bubbles 51 can be suppressed.

Here, the small holes 53A, 53A forming the bubble reservoir 53 are provided in a portion of the inner peripheral surface 36B1 of the right end side concave groove 36B corresponding to the notch 43B1. That is, the small holes 53A and 53A are provided at positions corresponding to the notches 43B1 in the circumferential direction of the spool 41. Therefore, when the spool 41 is displaced in the axial direction, the notch 43B1 and the small holes 53A, 53A face each other in the radial direction of the spool 41 and the spool sliding hole 33.

As shown in FIGS. 4 and 6, the diameter of the small hole 53A forming the bubble reservoir 53 is D, and the diameter of the bubble 51 generated by cavitation when hydraulic oil (oil liquid) passes through the notch 43B1. Let Db be the diameter of the jet flow 52 ejected from the notch 43B1 and heading toward the inner peripheral surface 36B1 of the right end side groove 36B. At this time, the hole diameter D of the small hole 53A is set to be larger than the diameter Db of the bubble 51 and smaller than the diameter Dc of the jet flow 52, as shown in the following Expression 1. This makes it easier for the air bubbles 51 to accumulate in the small holes 53A (easy to enter). The diameter Dc of the cavitation jet 52 can be the diameter Dc of the cavitation jet 52 at a position immediately before the collision with the inner peripheral surface 36B1 of the right end side groove 36B. For example, since Db is about 10 μm and Dc is about 10 mm, it is considered that D is about 0.5 to 3 mm (more preferably about 1 mm).

Assuming that the depth of the small hole 53A from the inner peripheral surface 36B1 of the right end side concave groove 36B is L, the depth L of the small hole 53A is the hole diameter D of the small hole 53A as shown in the following mathematical formula 2. Is set larger than. Thereby, the bubbles 51 can be accumulated in the small holes 53A in the depth direction (the bubbles 51 can be stacked in the depth direction). The depth L of the small hole 53A may be, for example, about 1.5 to 3 times the hole diameter D.

Further, as shown in FIGS. 5 and 6, the dimension of the portion where the small hole 53A is provided in the axial direction of the right end side groove 36B (left and right directions in FIGS. 5 and 6) is X, and the right end side groove Let Y be the dimension of the portion where the small hole 53A is provided in the circumferential direction of 36B (upward and downward in FIG. 5). At this time, for example, as shown in the following formula 3, the dimensions X and Y of the portion where the small hole 53A is provided can be set to be larger than the diameter Dc of the diameter of the cavitation jet 52. In this case, the jet flow 52 can collide within the range where the small holes 53A are provided.

Although a plurality of small holes 53A are provided in the embodiment, one (single) small hole may be provided. That is, the bubble reservoir may be formed by a single small hole having a bottom. When a plurality of small holes 53A are provided, the diameter dimension D and the depth dimension L of each small hole 53A may be the same for all small holes 53A or may be different as necessary. Further, as shown in FIG. 5, in the embodiment, the plurality of small holes 53A are arranged at equal intervals and form a rectangular (quadrangle) formation as a whole, but the present invention is not limited to this, and a circle, You may arrange|position so that it may become the shape of other shapes, such as an ellipse, a triangle, or a polygon more than a pentagon. That is, the diameter dimension D, the depth dimension L of the small hole 53A, the position and range of the small hole 53A, the arrangement of the small hole 53A, and the formation can suppress erosion (in other words, collapse or collapse of the bubble 51). In order to induce a flow for reducing the impact pressure at the time), it can be appropriately set according to the intention of the designer, the specifications of the directional control valve 31, and the like.

The hydraulic excavator 1 and the directional control valve 31 according to the first embodiment have the above-described configurations, and their operations will be described next.

When an operator riding in the cab 7 starts the engine 12, the engine 12 drives the hydraulic pumps 13 and 19. As a result, the pressure oil discharged from the hydraulic pumps 13 and 19 is supplied to the traveling hydraulic motor according to the lever operation and the pedal operation of the traveling operating device and the working operating device (lever operating device 22) provided in the cab 7. , The swing hydraulic motor, the boom cylinder 5D of the working device 5, the arm cylinder 5E, and the bucket cylinder 5F. As a result, the hydraulic excavator 1 can perform a traveling operation by the lower traveling body 2, a revolving operation of the upper revolving body 4, an excavation work by the work device 5, and the like.

Here, for example, when the lever operating device 22 is operated in a direction to extend the cylinder 5D (that is, a raising operation for raising the boom 5A is performed), the hydraulic pressure of the directional control valve 31 from the lever operating device 22. Pilot pressure is supplied to the pilot portion 31A. As a result, the directional control valve 31 switches from the neutral position (A) to the switching position (B). That is, as shown in FIG. 3, pilot pressure is supplied from the lever operating device 22 to the hydraulic pilot portion 31A in the left cap 45A, and the spool 41 slides rightward against the right spring 47B in the right cap 45B. Displace.

As a result, the pump port 38 of the housing 32 and the left actuator port 39A pass through the central concave groove 34, the notch 42A of the central land 42, the oil groove 44 between the central land 42 and the left land 43A, and the left concave groove 35A. Communicate with each other. Further, the right actuator port 39B and the right tank port 40B communicate with each other through the right concave groove 35B, the oil groove 44 between the central land 42 and the right land 43B, the notch 43B1 of the right land 43B, and the right end side concave groove 36B. To do. As a result, the pressure oil from the main hydraulic pump 13 is supplied to the bottom side oil chamber of the cylinder 5D via the main discharge pipe line 15, the pump port 38, the left actuator port 39A, and the bottom side pipe line 17. The pressure oil in the rod-side oil chamber of the cylinder 5D is discharged into the hydraulic oil tank 14 via the rod-side conduit 18, the right actuator port 39B, the right tank port 40B, and the return conduit 16. As a result, the cylinder 5D extends.

At this time, since the cross-sectional area of the oil passage formed by the notch 43B1 of the right land 43B is smaller than the cross-sectional area of the oil passage of the other portion, the notch 43B1 causes an increase in the flow velocity of the hydraulic oil and a decrease in pressure. However, this may cause cavitation. Then, as shown in FIG. 6, the cavitation jet 52 generated in the notch 43B1 collides with the inner peripheral surface 36B1 of the right end side groove 36B. On the other hand, when the lever operating device 22 is operated in the direction of reducing the cylinder 5D (that is, the lowering operation for lowering the boom 5A is performed), the cavitation jet generated in the notch 43A1 of the left land 43A is generated. (Not shown) collides with the inner peripheral surface 36A1 of the left end side concave groove 36A.

In this case, in the first embodiment, the inner peripheral surfaces of the housing grooves against which the cavitation jet 52 collides, that is, the inner peripheral surfaces of the low pressure side tank ports 40A, 40B side inner peripheral surfaces (oil passage wall surfaces) 36A, 36B. The surfaces 36A1 and 36B1 are provided with a plurality of small holes 53A and 53A. Therefore, the cavitation jet 52 generated in the notches 43A1 and 43B1 which are the openings of the spool 41 and the switching portion 37 has the surface of the member having the plurality of small holes 53A and 53A (the inner peripheral surfaces 36A1 and 36B1 of the concave grooves 36A and 36B). ). In this case, the bubbles 51 due to cavitation enter the small holes 53A, 53A, so that the bubble pool 53 is formed in the small holes 53A, 53A.

The bubble pool 53 absorbs the impact pressure generated when the cavitation bubbles 51 collapse, and thus can attenuate the force involved (contribution) in the erosion. In addition, a vortex 54, 54 is generated by the liquid (hydraulic oil) flowing through the edge (opening edge) of the small holes 53A, 53A, and the cavitation jet 52 collides with the jet collision portion (that is, The pressure field on the inner peripheral surfaces 36A1 and 36B1 of the concave grooves 36A and 36B is disturbed (a turbulent flow field is formed). As a result, pressure recovery in the vicinity of the jet impingement portion is less likely to occur, and the generation of impact force due to the collapse of the bubbles 51 is suppressed. As a result, erosion at the jet impingement portion can be suppressed, and the life of the directional control valve 31 with respect to erosion can be extended. In this case, since erosion can be suppressed without using an expensive material having high erosion resistance, the life can be improved while suppressing an increase in cost.

In the first embodiment, the small holes 53A, 53A forming the bubble reservoir 53 are notches 43A1 in the inner peripheral surfaces of the low pressure side tank ports 40A, 40B (the inner peripheral surfaces 36A1, 36B1 of the concave grooves 36A, 36B). , 43B1. Therefore, the cavitation jet flow 52 generated in the notches 43A1 and 43B1 can be advanced toward the small holes 53A and 53A. As a result, the damping of the force that contributes to (contributes to) the erosion and the suppression of the generation of the impact force due to the collapse of the bubble 51 are stably performed at the jet collision portion (in the vicinity of the inner peripheral surfaces 36A1 and 36B1 of the concave grooves 36A and 36B). It can be carried out.

In the first embodiment, the hole diameter D of the small holes 53A, 53A is set to be larger than the diameter Db of the bubble 51 and smaller than the diameter Dc of the jet flow 52. Therefore, it is possible to satisfy both “to form the bubble reservoir 53 in the small holes 53A and 53A” and “to generate the vortices 54 and 54 at the opening edges of the small holes 53A and 53A”. That is, the bubbles 51 can be stably accumulated in the small holes 53A and 53A, and the vortices 54 and 54 can be stably generated at the opening edges of the small holes 53A and 53A.

Further, in the first embodiment, the depth L of the small holes 53A, 53A is set to be larger than the hole diameter D. Therefore, the bubbles 51 can be accumulated in the depth direction of the small holes 53A, 53A (the depth direction bubbles 51 can be stacked). Thereby, the bubble reservoir 53 can be stably formed in the small holes 53A, 53A.

Next, FIGS. 7 and 8 show a second embodiment. The feature of the second embodiment resides in that a bubble reservoir composed of a plurality of bottomed small holes is provided on the inner wall surface of a plug that can be attached to and detached from a housing. In the second embodiment, the same components as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.

The housing 32 is provided with a through hole 61 extending in a direction orthogonal to the axial direction of the spool sliding hole 33. When the inner peripheral surface 36B1 of the right end side concave groove 36B, that is, the right actuator port 39B and the right tank port 40B communicate with each other through the notch 43B1, the through hole 61 collides with the hydraulic oil flowing from the high pressure side right actuator port 39B. It opens to the inner peripheral surface (oil passage wall surface) on the right tank port 40B side on the low pressure side. The through hole 61 of the housing 32 is provided with a plug 62 which is made of a member different from the housing 32 and seals the through hole 61 in a liquid-tight manner.

The plug 62 is attached to the through hole 61 by screwing, for example. The inner wall surface 62A of the plug 62 is provided with a bubble reservoir 53 composed of a plurality of bottomed small holes 53A, 53A. In this case, it is preferable that the inner wall surface 62A of the plug 62 be formed as the same surface as the inner peripheral surface 36B1 of the right end side concave groove 36B that is the inner peripheral surface of the low pressure side port 40B. That is, the size and shape of the plug 62 can be set so that when the plug 62 is attached to the through hole 61, the inner wall surface 62A of the plug 62 is flush with the inner peripheral surface 36B1 of the right end side groove 36B. preferable. In other words, it is preferable that the inner wall surface 62A of the plug 62 and the inner peripheral surface 36B1 of the right end side concave groove 36B are smoothly continuous peripheral surfaces.

Further, for example, a seal member (not shown) also called a seal ring (O-ring) is provided between the inner peripheral surface of the through hole 61 and the outer peripheral surface of the plug 62 so as to make the space therebetween liquid-tight. Can be sealed. The plug 62 may be made of, for example, the same material (material) as the housing 32, or may be made of a material (material) different from that of the housing 32. For example, the plug 62 may be made of a material having higher durability against erosion than the housing 32 (for example, a material having a high hardness), or the surface of the plug 62 (inner wall surface 62A) may be subjected to a heat treatment, a hardening treatment such as a surface treatment, or the like. May be given.

The second embodiment is configured such that the plug 62 as described above is provided with a bubble reservoir 53 composed of a plurality of bottomed small holes 53A, 53A, and the basic operation thereof is the same as that of the first embodiment described above. There is no particular difference from the embodiment. That is, also in the second embodiment, as in the first embodiment, it is possible to improve the life while suppressing the increase in cost.

In particular, in the second embodiment, the small hole 53A forming the bubble reservoir 53 is provided on the inner wall surface 62A of the plug 62 which is a member separate from the housing 32. Therefore, the small hole 53A can be processed more easily (simpler) than the structure in which the small hole is directly provided on the wall surface of the oil passage in the housing 32. Even if erosion can be suppressed by the small holes 53A, for example, erosion may progress if it is exposed to the jet flow 52 (see FIG. 6) for a very long time. Even in this case, the state of the oil passage of the directional control valve 31 can be returned to the original state (new state) simply by exchanging the plug 62, which is the erosion generation site. As described above, in the embodiment, the small hole 53A can be easily formed inside the directional control valve 31 (the inner surface of the spool sliding hole 33), and the erosion progresses in the jet collision portion due to long-term operation. Even in case of doing, the oil passage can be easily regenerated. This makes it possible to achieve both "low cost" and "long life" at a high level.

In the second embodiment, the inner wall surface 62A of the plug 62 is formed as the same surface as the inner peripheral surface 36B1 of the right end side concave groove 36B which is the inner peripheral surface of the low pressure side port 40B. Therefore, the inner wall surface 62A of the plug 62 and the inner peripheral surface 36B1 of the right end side groove 36B can be smoothly continuous. As a result, from this aspect as well, it is possible to achieve both "forming the bubble reservoir 53 in the small hole 53A" and "generating the vortex 54 at the opening edge of the small hole 53A".

In each of the embodiments, the case where the bubble reservoir 53 including the plurality of bottomed small holes 53A is provided in the left end side concave groove 36A and the right end side concave groove 36B has been described as an example. However, the present invention is not limited to this, and for example, the left recessed groove 35A and the right recessed groove 35B may be provided with a bubble reservoir formed of a plurality of bottomed small holes. That is, when the pump port 38 and the actuator ports 39A, 39B communicate with each other through the notches 42A, 42B, the inner peripheral surface on the side of the low pressure side actuator ports 39A, 39B against which the hydraulic oil flowing from the high pressure side pump port 38 collides ( That is, a plurality of small holes may be provided on the inner peripheral surface of the left concave groove 35A and the inner peripheral surface of the right concave groove 35B.

In each of the embodiments, the case where the bubble reservoir 53 including the plurality of small holes 53A is provided in the left end side concave groove 36A and the right end side concave groove 36B has been described as an example. However, the present invention is not limited to this, and a configuration may be adopted in which a bubble reservoir composed of a single (one) small hole is provided. That is, a configuration may be employed in which a bubble reservoir composed of a single (one) small hole is provided on the inner peripheral surface of the low-pressure side port side.

In each of the embodiments, the case where the small holes 53A and 53A forming the bubble reservoir 53 are provided in a portion of the inner peripheral surface 36B1 of the right end side groove 36B corresponding to the notch 43B1 has been described as an example. However, the configuration is not limited to this, and may be provided, for example, over the entire circumference of the inner peripheral surface 36B1 of the right end side concave groove 36B.

In each of the embodiments, as the spool valve device, the directional control valve 31 for switching the supply and the discharge of the pressure oil to the boom cylinder 5D has been described as an example. However, the invention is not limited to this, and may be applied to, for example, a directional control valve used for an arm cylinder 5E, a bucket cylinder 5F, a traveling hydraulic motor, a turning hydraulic motor, or the like. In addition to this, it can be applied to various spool valve devices (spool valves) such as a pressure control valve and a flow rate control valve.

In each embodiment, the hydraulic excavator 1 of the engine type driven by the engine 12 is described as an example of the construction machine. However, the present invention is not limited to this, and can be applied to, for example, a hybrid hydraulic excavator driven by an engine and an electric motor, and an electric hydraulic excavator driven by an electric motor. Further, the invention is not limited to hydraulic excavators, but can be widely applied to various construction machines such as wheel loaders, hydraulic cranes and bulldozers. Further, it is needless to say that each embodiment is an exemplification, and partial replacement or combination of the configurations shown in different embodiments is possible.

1 Hydraulic excavator (construction machinery)
5D boom cylinder (hydraulic actuator)
11 hydraulic circuit 11A main hydraulic circuit 11B pilot hydraulic circuit 31 directional control valve (spool valve device)
32 Housing 33 Spool sliding hole 37 Switching part 34 Central concave groove (concave groove)
35A Left side groove (concave groove, one side groove)
35B Right side groove (concave groove, other side groove)
36A Left end side concave groove (concave groove, one end side concave groove)
36B Right end side concave groove (concave groove) Other end side concave groove)
36A1, 36B1 inner peripheral surface (inner peripheral surface of low-pressure side port)
38 Pump port (port)
39A Left actuator port (port)
39B Right actuator port (port)
40A Left tank port (port)
40B Right tank port (port)
41 spool 42 central land (land)
43A Left land (land)
43B Right Land (Land)
42A, 42B, 43A1, 43B1 Notch 44 Oil groove 51 Bubble 52 Cavitation jet (jet flow)
53 Bubble Reservoir 53A Small Hole 61 Through Hole 62 Plug 62A Inner Wall Surface

Claims (4)

A tubular housing having a spool sliding hole and provided with a plurality of ports in the axial direction of the spool sliding hole with the switching portion interposed therebetween;
A spool having an oil groove and a land, which are movably inserted into a spool sliding hole of the housing and are axially separated from each other so as to communicate or block between the ports;
A cracking position is provided at the land located at the boundary between the land of the spool and the oil groove, and allows the ports to communicate with each other when the spool moves. In a spool valve device including a notch,
Wherein the inner peripheral surface of the low pressure side ports each port hydraulic fluid collides flowing from the high pressure side port when communicating through said notch, at least one bottomed bubble reservoir consisting of a small hole is provided ,
The diameter of the small hole forming the bubble reservoir is D, the diameter of the bubble generated by cavitation when hydraulic oil passes through the notch is Db, and the inner peripheral surface of the low-pressure side port ejected from the notch. Let Dc be the diameter of the jet flowing toward and L be the depth of the small hole from the inner peripheral surface of the low-pressure side port.
The hole diameter D of the small hole is set to be larger than the diameter Db of the bubble and smaller than the diameter Dc of the jet flow,
The spool valve device , wherein the depth L of the small hole is set to be larger than the hole diameter D of the small hole . The housing is provided with a through hole that is orthogonal to the axial direction of the spool sliding hole and opens on the inner peripheral surface of the low-pressure side port.
The housing is provided with a plug formed of a member different from the housing and sealing the through hole in a liquid-tight manner,
The spool valve device according to claim 1, wherein the bubble reservoir is provided on an inner wall surface of the plug. The spool valve device according to claim 1, wherein the small hole forming the bubble reservoir is provided in a portion of the inner peripheral surface of the low-pressure side port corresponding to the notch. The spool valve device according to claim 2, wherein an inner wall surface of the plug is formed to be flush with an inner peripheral surface of the low-pressure side port.

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