JP6913659B2 - Spool valve device - Google Patents

Description

The present invention relates to a spool valve device used as a directional control valve, a pressure control valve, a flow rate control valve, or the like of a hydraulic system (hydraulic pressure system) mounted on a construction machine such as a hydraulic excavator.

In general, construction machines such as hydraulic excavators, hydraulic cranes, and wheel loaders are equipped with a hydraulic system (hydraulic system), which is 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 driven by pressure oil supplied from the hydraulic source, and a hydraulic actuator (hydraulic actuator) such as a hydraulic cylinder. It is configured to include a spool valve (spool valve device) such as a directional control valve provided between the hydraulic source and the hydraulic actuator to switch between supply and discharge of pressure oil to the hydraulic actuator.

Here, the spool valve used in the hydraulic system has a role of adjusting the opening amount by displacing the valve body called the spool in the axial direction in response to an input command and controlling the flow velocity, pressure and direction of the hydraulic system. have. In addition, the spool (land) is provided with a notch called a notch in order to improve the flow rate control performance and suppress oil impact. The notch forms a throttle portion with the housing whose flow path area is smaller than that of other portions, depending on the position of the spool.

When a liquid such as hydraulic oil passes through such a throttle portion (notch), the flow velocity sharply increases and at the same time the pressure sharply drops according to Bernoulli's principle. At this time, if the pressure of the liquid becomes lower than the saturated vapor pressure determined by the type (liquid type) of the liquid due to this sudden pressure drop, cavitation occurs in which bubbles are generated in the liquid and the liquid expands. .. Further, the bubbles generated in the throttle portion are carried on the high-speed fluid jet (cavitation jet) and flowed to the downstream side of the throttle portion.

At this time, since the relationship between the pressure Pc at the cavitation generating portion and the pressure Pd at the downstream portion is Pc <Pd, the pressure around the bubbles flowing downstream gradually recovers, and the bubbles eventually recover. It is crushed by the pressure. Then, at the moment when the bubbles are crushed and collapsed, a high impact pressure is locally generated, which may damage the surface of the equipment member and cause erosion (erosion). If this erosion occurs on the valve body or valve components, the reliability of the equipment can be reduced.

As a technique for suppressing such erosion, for example, in Patent Document 1, an annular groove is provided on the spool wall surface where the cavitation jet generated in the throttle portion collides, and bubbles of the cavitation jet are accumulated in the annular groove. The flow control valve is described.

JP-A-2010-144654

By the way, FIG. 13 shows a comparative example in which the annular groove 103 is provided on the stepped surface 102 of the spool 101. That is, in the comparative example, the annular groove 103 is provided at the collision portion of the cavitation jet generated by the annular throttle portion 106 formed by the edge 104 of the spool 101 and the housing 105. In the case of this configuration, the oil flow flows from the annular throttle portion 106 into the annular groove 103, forms a violent turbulent field in the annular groove 103, and then flows out from the annular groove 103 to the downstream side. Therefore, the flow of oil passing through the spool valve may form a complicated streamline as shown by an arrow in FIG. 13, and the flow loss may increase.

Next, consider the case where the spool 101 is provided with the notch 107. In this case, although not shown, when the oil is flowing downstream only through the notch 107, the portion where the cavitation jet generated in the throttle portion formed by the housing 105 and the notch 107 collides is the stepped surface 102. Of these, it is limited to the part facing the notch 107. At this time, if the annular groove 103 is provided on the stepped surface 102, the annular groove 103 is too large for the cavitation jet, and air bubbles cannot be sufficiently accumulated in the annular groove 103, so that erosion may not be suppressed. There is.

Further, when the throttle portion is formed by the notch 107 and the housing 105, the cavitation jet intensively collides with a specific portion, whereas the edge 104 and the housing 105 form an annular throttle portion 106. If so, cavitation jets are generated radially starting from the annular edge 104. As a result, the cavitation jets are dispersed and collide with each other over a wide area in the downstream part. Therefore, the flow state in which the contribution to the generation of erosion is large is when the throttle portion is formed by the notch 107. Therefore, based on these, it is considered that even if the technique of the annular groove of Patent Document 1 is adopted, the erosion suppressing effect cannot be sufficiently obtained and there is a high possibility that an unnecessary flow loss is generated.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a spool valve device capable of both suppressing erosion and suppressing flow loss.

The spool valve device of the present invention has a tubular housing having a spool sliding hole and having a plurality of ports separated from each other in the axial direction of the spool sliding hole, and a spool sliding hole of the housing. A spool that is movably inserted and has a large diameter portion that serves as a land for communicating or blocking between the ports and a small diameter portion that serves as a constriction are provided adjacent to each other in the axial direction, and the large diameter portion of the spool. A notch located at the boundary between the stepped surface connecting the portion and the small diameter portion and the large diameter portion and provided in the large diameter portion to communicate between the ports at a small flow rate when the spool moves. In the spool valve device provided with the above, the gas contained in the working fluid is used as bubbles on the stepped surface of the spool where the hydraulic oil flowing from the port on the high pressure side collides when the respective ports communicate with each other through the notch. There is a bottomed hole for storing.

According to the present invention, both suppression of erosion and suppression of flow loss can be achieved at the same time.

It is a front view which shows the hydraulic excavator which mounted the spool valve device by 1st Embodiment. It is a hydraulic circuit diagram for driving a hydraulic actuator which shows a hydraulic actuator, a hydraulic pump, a lever operation device, a spool valve device and the like. It is sectional drawing of the main part which shows the housing, the spool and the like of a spool valve device. It is an enlarged cross-sectional view of part (IV) in FIG. It is sectional drawing of the main part which shows the flow of the working fluid which flows through the throttle part by the notch of a spool. It is sectional drawing of the main part which shows the flow of the working fluid which flows through the annular throttle part by the edge of a spool. It is sectional drawing at the same position as FIG. 4 which shows the bottomed hole and the like by 2nd Embodiment. It is sectional drawing of the main part which shows the housing, the spool and the like of the spool valve device by 3rd Embodiment. It is an enlarged cross-sectional view seen from the arrow IX-IX direction in FIG. It is an enlarged cross-sectional view of the part (X) in FIG. It is the same cross-sectional view as FIG. 10 which shows the flow of the working fluid which flows through the throttle part by the notch of a spool. It is sectional drawing of the same position as FIG. 11 which shows the bottomed hole and the like according to 3rd Embodiment. It is a cross-sectional view of a main part at a position similar to FIG. 6 showing the flow of a working fluid according to a comparative example.

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

1 to 6 show the first embodiment. In FIG. 1, the hydraulic excavator 1, which is a typical example of a construction machine, has a self-propelled crawler-type lower traveling body 2, a swivel device 3 provided on the lower traveling body 2, and swivel on the lower traveling body 2. The upper swivel body 4 mounted so as to be swivelable via the device 3 and a work device 5 having an articulated structure provided on the front side of the upper swivel body 4 and performing excavation work and the like are included. In this case, the lower traveling body 2 and the upper turning body 4 constitute the vehicle body of the hydraulic excavator 1.

The lower traveling body 2 includes, for example, a crawler belt 2A and left and right traveling hydraulic motors (not shown) for traveling the hydraulic excavator 1 by orbiting the crawler belt 2A. The lower traveling body 2 is formed by rotating the traveling 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) described later. It travels with the work device 5.

The working device 5, which is also called a working machine or a front, includes, for example, a boom 5A, an arm 5B, a bucket 5C as a working tool, and a boom cylinder 5D, an arm cylinder 5E, and a bucket cylinder as a hydraulic actuator (hydraulic actuator) for driving them. (Working tool cylinder) 5F is included. The working device 5 operates in an up-and-down manner by expanding or contracting the cylinders 5D, 5E, and 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 described later, the hydraulic circuit mainly related to the boom cylinder 5D is shown in order to avoid complicating the drawing, and the arm cylinder 5E, the bucket cylinder 5F, and the above-mentioned left and right traveling The hydraulic circuit related to the hydraulic motor for turning and the hydraulic motor for turning described later is omitted.

The upper swivel body 4 is mounted on the lower traveling body 2 via a swivel device 3 including a swivel bearing, a swivel hydraulic motor, a speed reduction mechanism, and the like. The upper swivel body 4 works on the lower traveling body 2 by rotating a swivel 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). Turn with the device 5. The upper swivel body 4 includes a swivel frame 6 that serves as a support structure (base frame) for the upper swivel body 4, a cab 7 mounted on the swivel frame 6, a counterweight 8, and the like. In this case, in addition to the engine 12, the hydraulic pumps 13, 19 and the hydraulic oil tank 14 shown in FIG. 2 are mounted on the swivel frame 6.

The swivel frame 6 is attached to the lower traveling body 2 via the swivel device 3. A cab 7 having a driver's cab inside is provided on the left side of the front portion of the swivel frame 6. A counterweight 8 for balancing the weight with the working device 5 is provided on the rear end side of the swivel frame 6. Between the cab 7 and the counterweight 8, there is a machine room 9 in which an engine 12, hydraulic pumps 13, 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 swing body 4 (swing frame 6).

Here, a driver's seat (not shown) in which the operator is seated is provided in the cab 7. 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 operating devices include, for example, left and right traveling lever / pedal operating devices provided on the front side of the driver's seat and left and right working lever operating devices provided on both the left and right sides of the driver's seat, respectively. It is configured.

The left and right traveling lever / pedal operating devices are operated by the operator when the lower traveling body 2 is driven. The left and right work lever operating devices are operated by the operator when operating the working device 5 and when turning the upper swivel body 4. In the hydraulic circuit diagram of FIG. 2 described later, the 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 (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 operating device 22 corresponds to, for example, the operation of the working lever operating device on the right side in the front-rear direction.

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 composed of a plurality of directional control valves (only the boom directional control valve 31 is shown in FIG. 2). Output. As a result, the operator can operate (drive) the traveling hydraulic motor, the cylinders 5D, 5E, 5F of the working device 5, and the turning hydraulic motor of the turning device 3. In the hydraulic circuit diagram of FIG. 2 described later, only the boom directional control valve 31 is shown among the plurality of directional control valves constituting the control valve device 21 (for example, the left traveling directional control valve and the right traveling direction control valve). Direction control valve for use, direction control valve for turning, direction control valve for arm, direction control valve for bucket, etc. are omitted).

Next, a hydraulic drive device (hydraulic system) for driving the hydraulic excavator 1 will be described with reference to FIG. 2 in addition to 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 main hydraulic pump 13. The hydraulic circuit 11 includes 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, and a control valve device 21 (boom direction control). The valve 31) and an operating device (hereinafter, also simply referred to as a lever operating device 22) are included. Then, 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 (boom direction control valve 31), and a pump pipeline. A main discharge line 15 as a tank line, a return line 16 as a tank line, a bottom line 17 as a one-side actuator line, and a rod-side line 18 as the other actuator 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 pipe 20, and an extension side as a one-side pilot pipe. The pilot line 23 and the reduced side pilot line 24 as the other side pilot line are provided.

The engine 12 (see FIG. 1) is mounted on the swivel 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. These 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 composed of an engine 12 alone as an internal combustion engine, or may be composed of, for example, an engine and an electric motor, or an electric motor alone. ..

The main hydraulic pump 13 is mechanically (ie, power transferable) connected 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 composed of, for example, a variable displacement hydraulic pump, more specifically, a variable displacement swash plate type, sloping shaft type or radial piston type hydraulic pump. Although the main hydraulic pump 13 is shown by one hydraulic pump in FIG. 2, for example, it can be configured by a plurality of 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 boom cylinder 5D, the traveling hydraulic motor, the turning hydraulic motor, the arm cylinder 5E, and the bucket cylinder 5F.

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 line 15 is supplied to the boom cylinder 5D (bottom side oil chamber or rod side oil chamber) via the control valve device 21 (boom direction control valve 31), and is supplied to 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 (boom direction control valve 31) and the return pipeline 16. As described above, the main hydraulic pump 13 constitutes the main hydraulic source together with the hydraulic oil tank 14 for storing the hydraulic oil.

The pilot hydraulic pump 19 is mechanically connected to the engine 12 like the main hydraulic pump 13. 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 composed of, for example, a fixed-capacity 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 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 (hydraulic pilot units 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 uses the pressure oil discharged from the main hydraulic pump 13 for the boom cylinder 5D, the arm cylinder 5E, the bucket cylinder 5F, and the traveling according to the operation of various operating devices including the boom lever operating device 22. 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 a directional control valve 31) will be described as a typical example of the control valve device 21.

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

The directional control valve 31 expands or contracts the cylinder 5D by switching between supply and discharge of pressure oil to 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 units 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 line 20. The lever operating device 22 outputs the pilot pressure (secondary pressure) corresponding to the operator's lever operation to the directional control valve 31 via the extension side pilot line 23 or the reduction side pilot line 24.

That is, the lever operating device 22 supplies (outputs) a pilot pressure proportional to the amount of operation to the hydraulic pilot units 31A and 31B of the directional control valve 31 by being operated by the operator. 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 pipeline 23. It is supplied to the hydraulic pilot unit 31A of the directional control valve 31 via. As a result, the directional control valve 31 is switched 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 side oil chamber of the cylinder 5D via the bottom side pipeline 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 pipeline 18 and the return pipeline 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 pipeline 24. As a result, the directional control valve 31 is switched 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 pipeline 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 directional control valve 31 as the spool valve device will be described with reference to FIGS. 3 to 6 in addition to FIGS. 1 and 2.

The directional control valve 31, also called a spool valve, is provided between the hydraulic source (main hydraulic pump 13 and hydraulic oil tank 14) and the hydraulic actuator (cylinder 5D). The directional control valve 31 slides and displaces the spool 39 from the neutral position shown in FIG. 2 (A) to the switching position shown in (B) or (C), for example, to supply and discharge the pressure oil to the cylinder 5D. Control direction and flow rate. As shown in FIG. 3, the directional control valve 31 includes a housing 32 and a spool 39.

The housing 32 constitutes the valve body (valve housing) of the directional control valve 31. The housing 32 is formed in a tubular shape, and the inner peripheral side of the housing 32 is a spool sliding hole 33. That is, the housing 32 has a spool sliding hole 33 as a valve accommodating hole extending in the axial direction (left and right directions in FIG. 3). One side cap (not shown) is attached to one side of the housing 32 (for example, the right side in FIG. 3) so as to face the one side opening of the spool sliding hole 33, and the other side (not shown) of the housing 32 (for example). For example, on the left side of FIG. 3), a cap (not shown) on the other side is attached so as to face the opening on the other side of the spool sliding hole 33. Centering springs 31C and 31D (see FIG. 2) for holding the spool in the neutral position (A) are provided in both caps or in one cap.

As shown in FIG. 3, the spool sliding hole 33 is provided with a plurality of recessed grooves 34, 35. In this case, the spool sliding hole 33 has, for example, five concave grooves 34, 35, specifically, the central concave groove 34 located at the central portion in the axial direction, and one side in the axial direction from the central concave groove 34 (FIG. One-sided concave groove 35 located on the right side of 3), one-sided concave groove (not shown) located on one side in the axial direction (one end side of the spool sliding hole 33), and fovea centralis. The other side concave groove (not shown) located on the other side in the axial direction (left side in FIG. 3) from 34, and located on the other side in the axial direction (the other end side of the spool sliding hole 33) than the other side concave groove. A concave groove (not shown) on the other end side is provided. In FIG. 3, of the five concave grooves 34, 35, two concave grooves 34, the central concave groove 34 and the one-side concave groove 35 provided on one side in the axial direction from the central concave groove 34, 35 is shown.

The plurality of concave grooves 34 and 35 are all formed in an annular shape over the entire circumference of the spool sliding hole 33. Further, the concave grooves 34 and 35 are provided apart from each other in the axial direction of the spool sliding holes 33. In this case, between the concave grooves 34 and 35, there are switching portions 36 and 36 that project over the entire circumference toward the inner diameter side of the spool sliding hole 33, respectively. Further, the housing 32 is provided with a plurality of ports 37 and 38 separated from each other in the axial direction of the spool sliding holes 33. Ports 37 and 38 serve as passages (oil passages) through which pressure oil flows. In this case, the housing 32 is provided with, for example, five ports 37, 38, specifically, a pump port 37, a pair of actuator ports 38, and a pair of tank ports (not shown). Note that, in FIG. 3, of the five ports 37 and 38, two ports 37 and 38, the pump port 37 and one actuator port 38, are shown.

The pump port 37 is provided corresponding to the fovea centralis 34 of the spool sliding hole 33. One side of the pump port 37 that opens to the outer surface of the housing 32 is connected to the main discharge pipe line 15, and the other side that opens to the spool sliding hole 33 communicates with the fovea centralis groove 34. One of the pair of actuator ports 38, the actuator port 38, is provided corresponding to the one-side concave groove 35 of the spool sliding hole 33. For example, one side of the actuator port 38 that opens to the outer surface of the housing 32 is connected to the rod side pipeline 18, and the other side that opens to the spool sliding hole 33 communicates with the one-side concave groove 35. On the other hand, the other actuator port is provided corresponding to the concave groove on the other side of the spool sliding hole 33. For the other actuator port, for example, one side that opens to the outer surface of the housing 32 is connected to the bottom side pipeline 17, and the other side that opens to the spool sliding hole 33 communicates with the other side concave groove.

One of the pair of tank ports is provided so as to correspond to the concave groove on one end side of the spool sliding hole 33. One side of the tank port that opens to the outer surface of the housing 32 is connected to the return pipe line 16, and the other side that opens to the spool sliding hole 33 communicates with the concave groove on one end side. On the other hand, the other tank port is provided corresponding to the concave groove on the other end side of the spool sliding hole 33. The other tank port has one side that opens to the outer surface of the housing 32 connected to the return pipe line 16 and the other side that opens to the spool sliding hole 33 communicates with the concave groove on the other end side. As a result, the housing 32 is provided with a plurality of ports 37, 38 in the axial direction of the spool sliding holes 33 with the switching portions 36, 36 interposed therebetween.

The spool 39, which is a valve body, is movably inserted into the spool sliding hole 33 of the housing 32. The spool 39 slides and displaces in the spool sliding hole 33 in the axial direction according to the pilot pressure supplied to the hydraulic pilot portions 31A and 31B. As a result, the spool 39 communicates with or shuts off the plurality of ports 37 and 38 from each other. For this purpose, the spool 39 is provided with large diameter portions 40 and 41 serving as lands for communicating or blocking between the ports 37 and 38 and small diameter portions 42 serving as constrictions adjacent to each other in the axial direction. .. That is, a central large-diameter portion 40 having an outer peripheral surface having a large radial dimension is provided at the axial intermediate portion of the spool 39. Further, on both ends in the axial direction of the spool 39, a large diameter portion 41 on one side and a large diameter portion on the other side (not shown) having an outer peripheral surface having the same outer diameter as the central large diameter portion 40 are provided. There is.

Each of these large diameter portions 40 and 41 slides in the axial direction with respect to the spool sliding hole 33. In this case, there is a small diameter portion 42 between the large diameter portions 40 and 41. The small diameter portion 42 and the large diameter portions 40, 41 are connected by an annular stepped surface 43. An oil groove 44 composed of an outer peripheral surface 42A of the small diameter portion 42 and a stepped surface 43, 43 is formed between the large diameter portions 40 and 41. That is, between the large diameter portions 40 and 41, there is an oil groove 44 that is recessed over the entire circumference toward the inner diameter side of the spool 39. In other words, the spool 39 is provided with an oil groove 44 as a constricted portion and large diameter portions 40 and 41 as sliding portions, which are separated in the axial direction to communicate or shut off 37 and 38 between the ports. Has been done. The oil groove 44 forms an oil passage that connects the pump port 37 (recessed groove 34) and the actuator port 38 (recessed groove 35) according to the axial position of the spool 39.

That is, when the spool 39 is displaced to the left from the neutral position shown in FIG. 2, the space between the central concave groove 34 and the one-side concave groove 35 is between the central large-diameter portion 40 and the one-side large-diameter portion 41. It is communicated through the oil groove 44. At the same time, the other side concave groove and the other end side concave groove are communicated with each other via an oil groove between the central large diameter portion 40 and the other side large diameter portion. In this case, the pressure oil discharged from the main hydraulic pump 13 passes through the main discharge pipe line 15, the pump port 37, the central concave groove 34, between the switching portion 36 and the oil groove 44, and the one-side concave groove 35. It is guided to one of the actuator ports 38 and supplied to the rod side oil chamber of the cylinder 5D via the rod side pipeline 18. On the other hand, the pressure oil in the bottom side oil chamber of the cylinder 5D passes through the bottom side pipeline 17, the other actuator port, the other side concave groove, between the switching portion and the spool oil groove, and the other end side concave groove. It is guided to the other tank port and returned to the hydraulic oil tank 14 via the return pipeline 16. As a result, the cylinder 5D can be reduced.

Here, the boundary between the outer peripheral surface of the central large-diameter portion 40 and the stepped surface 43 is an annular edge 45. Then, as shown in FIGS. 3 to 6, the central large-diameter portion 40 of the spool 39 is located at the boundary portion (edge 45) between the central large-diameter portion 40 and the stepped surface 43 (oil groove 44). A notch 46 is provided. The notch 46 communicates between the ports 37 and 38 at a small flow rate when the spool 39 moves. That is, a notch 46 extending in the axial direction is formed on one end side (right end side) of the central large diameter portion 40. In the embodiment, the notch 46 is, for example, a quadrangular notch in which the width dimension and the depth dimension are constant with respect to the axial direction of the spool 39.

The notch 46 allows the pressure oil flowing between the adjacent recesses 34 and 35, that is, between the pump port 37 and the actuator port 38, to communicate with each other at a small flow rate. That is, the notch 46 communicates between the ports 37 and 38 at a small flow rate at a position (cracking position) at which the spool 39 communicates with each other when the spool 39 moves. As a result, between the spool 39 and the housing 32 (switching portion 36 of the spool sliding hole 33), depending on the axial position of the spool 39, the throttle portion 47 shown in FIG. 5 or the annular shape shown in FIG. 6 The drawing portion 48 of the above is formed. The throttle portion 47 shown in FIG. 5 is an opening having a small flow path area formed by the notch 46 of the spool 39 and the housing 32 (switching portion 36). The throttle portion 48 shown in FIG. 6 is an annular opening formed by the edge 45 of the spool 39 and the housing 32 (switching portion 36). The flow path area of the opening (throttle portion 48) in FIG. 6 is larger than the flow path area of the annular opening (throttle portion 47) in FIG.

Here, when the pressure oil passes through the opening between the housing 32 (switching portion 36) and the central large diameter portion 40 of the spool 39, if the opening amount of this opening is small, that is, the flow path area of the opening. If is small, this opening becomes the throttle portions 47 and 48, and there is a possibility that cavitation may occur in which bubbles are generated in the liquid (in the hydraulic oil) and the liquid expands. Then, the bubbles generated in the throttle portions 47 and 48 are flown to the downstream side of the throttle portions 47 and 48 on the cavitation jet 49 which is a high-speed fluid jet.

At this time, since the pressure in the downstream portion is higher than that in the throttle portions 47 and 48, the pressure around the bubbles is gradually recovered, and the bubbles are eventually crushed by the recovered pressure. Then, at the moment when the bubbles are crushed and collapsed, a high impact pressure is locally generated, and the surface of the equipment member, for example, the stepped surface 43 of the spool 39, the outer peripheral surface of the large diameter portion 41, and the housing 32 (one side). Erosion may occur on the inner surface of the concave groove 35) or the like.

On the other hand, FIG. 13 shows a comparative example. The thin arrow in FIG. 13 indicates the flow direction of the pressure oil. In other figures such as FIGS. 5 and 6, the thin arrow indicates the flow direction of the pressure oil. In the comparative example of FIG. 13, an annular groove 103 is provided on the stepped surface 102 of the spool 101. In the case of this configuration, the oil flow flows from the annular throttle portion 106 into the annular groove 103, as shown by the thin arrow in FIG. 13, and after forming a violent turbulent field in the annular groove 103, It flows out from the annular groove 103 to the downstream side. That is, the oil flow can form complex streamlines and increase flow loss. On the other hand, when the oil is flowing downstream only through the notch 107, the portion where the cavitation jet generated in the throttle portion formed by the housing 105 and the notch 107 collides is the portion of the stepped surface 102 facing the notch 107. Limited to only. Therefore, if the annular groove 103 is provided on the stepped surface 102, the annular groove 103 is too large for the cavitation jet, and air bubbles cannot be sufficiently accumulated in the annular groove 103, so that erosion may not be suppressed. There is.

Therefore, in the present embodiment, as shown in FIGS. 3 to 6, when the ports 37 and 38 communicate with each other through the notch 46, the stepped surface 43 of the spool 39 collides with the hydraulic oil flowing from the pump port 37 on the high pressure side. Is provided with a bottomed hole 50 that opens in the stepped surface. The bottomed hole 50 stores the gas contained in the working fluid as bubbles. That is, in the constricted portion (oil groove 44) of the spool 39, the stepped surface 43 opposite to the stepped surface 43 provided with the notch 46, and the portion where the jet generated at the notch 46 collides, is formed on the stepped surface 43. A bottomed hole 50, which is a small hole perpendicular to the hole, is provided. The site where the bottomed hole 50 is provided, that is, the jet collision site, can be identified (specified) by, for example, a visualization experiment of the flow of the working fluid, a fluid analysis, or the like.

For example, in the first embodiment, the bottomed hole 50 is provided on the stepped surface 43. That is, the bottomed hole 50 is open to the stepped surface 43. Further, the bottomed hole 50 extends parallel to the central axis of the spool 39. Further, the bottomed hole 50 is provided on the inner diameter side of the deepest portion 46A of the notch 46 in the radial direction of the spool 39. Further, the bottomed hole 50 is provided at a position corresponding to the notch 46 in the circumferential direction of the spool 39 on the stepped surface 43. In other words, the notch 46 and the bottomed hole 50 are in phase with each other in the circumferential direction of the spool 39. That is, the notch 46 and the bottomed hole 50 face each other in the axial direction of the spool 39.

The bottomed hole 50 is a circular hole. Then, as shown in FIG. 4, the inner diameter of the bottomed hole 50 is Db, the depth of the bottomed hole 50 is Hb, and the diameter of the cavitation jet 49 ejected from the notch 46 toward the stepped surface 43 is Dj. .. In this case, the inner diameter Db of the bottomed hole 50 is set to be 1 time or more and 3 times or less the diameter Dj of the cavitation jet 49. That is, the relationship between the inner diameter Db of the bottomed hole 50 and the diameter Dj of the cavitation jet 49 is set to be the following equation (1). The diameter Dj of the cavitation jet 49 can be, for example, the diameter Dj on the stepped surface 43 (that is, the diameter Dj at a position separated by a length L from the outlet portion of the notch 46).

Further, the depth Hb of the bottomed hole 50 is larger than 1/2 of the inner diameter Db of the bottomed hole 50 (radius of the bottomed hole 50). That is, the relationship between the depth Hb of the bottomed hole 50 and the inner diameter Db is set to be the following equation (2). In the first embodiment, the depth Hb of the bottomed hole 50 is the length (depth) from the stepped surface 43 in the axial direction of the spool 39.

Here, the diameter Dj of the cavitation jet 49 changes according to the distance (length L) from the outlet portion of the notch 46, which is the generation portion of the cavitation jet 49. That is, the diameter Dj of the cavitation jet 49 is defined by the following equation (3).

Here, Dn is the diameter (diameter) of the virtual circle when the opening area at the outlet of the notch 46 is assumed to be the cross-sectional area of the circle. Further, C (L) is a rate of change in the diameter Dj of the cavitation jet 49 depending on the length L from the outlet portion of the notch 46 to the jet collision portion (step surface 43). The value of this rate of change C (L) can be grasped by using experimental measurement or fluid analysis. Thereby, the inner diameter Db of the bottomed hole 50 can be set from the relationship between the length L from the outlet portion of the notch 46 to the stepped surface 43 and the diameter of the notch 46 based on the equation (3).

Although not shown, for example, when a plurality of notches are provided on the spool, a plurality of bottomed holes may be provided on the stepped surface so as to be paired with the notches. Further, the bottom surface of the bottomed hole does not necessarily have to be flat, and may be a tool shape such as a drill or a spherical shape having R.

The hydraulic excavator 1 and the directional control valve 31 according to the first embodiment have the above-described configuration, and the operation thereof will be described next.

When the operator on the cab 7 starts the engine 12, the hydraulic pumps 13 and 19 are driven by the engine 12. As a result, the pressure oil discharged from the main hydraulic pump 13 is supplied to the traveling hydraulic motor according to the lever operation and pedal operation of the traveling operation device and the work operation device (lever operation device 22) provided in the cab 7. Discharges toward 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 turning operation of the upper rotating body 4, an excavation operation by the working device 5, and the like.

Here, when the lever operating device 22 is operated, in response to this operation, from the pilot hydraulic pump 19 to one hydraulic pilot section 31A or the other hydraulic pilot section 31B of the direction control valve 31 via the lever operating device 22. Pilot pressure is supplied. As a result, the directional control valve 31 switches from the neutral position (A) to the switching position (B) or the switching position (C). At this time, the main discharge line 15 is connected to one of the bottom side line 17 and the rod side line 18 (18) via the directional control valve 31, and is connected to the main hydraulic pump 13 from the main hydraulic pump 13. Pressure oil is supplied to one of the bottom side oil chamber and the rod side oil chamber of the cylinder 5D. At the same time, the other pipe line 18 (17) of the bottom side pipe line 17 and the rod side pipe line 18 is connected to the return pipe line 16 via the directional control valve 31, and the bottom side oil chamber of the cylinder 5D. The pressure oil in the oil chamber of the other oil chamber of the rod side oil chamber is guided to the hydraulic oil tank 14.

At this time, as shown in FIG. 3, inside the directional control valve 31, the pump port 37 and the actuator port 38 communicate with each other through the notch 46 of the spool 39 as the spool 39 is displaced in the axial direction. Since the oil passage formed here, that is, the opening (throttle portion 47) formed by the notch 46 is smaller than the cross-sectional area of the other oil passages, the notch 46 causes an increase in flow velocity and a decrease in pressure. This can lead to cavitation.

As shown in FIG. 4, the cavitation generated in the notch 46 becomes a cavitation jet 49 containing air bubbles, is injected into the oil passage formed by the switching portion 36 of the housing 32 and the oil groove 44, and is injected into the spool 39 (of the spool 39). It flows into the bottomed hole 50 provided on the surface of the stepped surface 43). In this case, as shown by the arrow in FIG. 5, the flow of the working fluid (cavitation jet 49) is changed so as to fold back inside the bottomed hole 50, and from the opening of the bottomed hole 50 to the oil passage again. leak. At this time, a bubble pool is formed in the bottomed hole 50.

Next, when the spool 39 is further displaced (stroked) in the axial direction from the state of FIG. 5 as shown in FIG. 6, the pump port 37 and the actuator port 38 communicate with each other via the edge 45 of the spool 39. Since the oil passage formed here, that is, the annular opening (annular throttle portion 48) formed by the edge 45 is also smaller than the other oil passage cross-sectional areas, cavitation may occur at the edge 45. be. In this case, as shown by an arrow in FIG. 6, the flow of the working fluid (cavitation jet 49) is a radial flow unlike the case where the opening (throttle portion 47) is formed at the notch 46. That is, the cavitation jet 49 is formed radially, and most of it flows along the surface of the oil groove 44 of the spool 39 and flows out to the actuator port 38 as it is.

As described above, according to the first embodiment, the gas contained in the working fluid is used as bubbles on the stepped surface 43 of the spool 39 where the hydraulic oil flowing from the high pressure side port (pump port 37) collides with the hydraulic oil flowing through the notch 46. A bottomed hole 50 for storing is provided. Therefore, the cavitation jet 49 generated in the opening (throttle portion 47) formed by the notch 46 of the spool 39 and the spool sliding hole 33 (switching portion 36) of the housing 32 is located at a position where the jet 49 collides. It flows into the provided bottomed hole 50, and a bubble pool is formed in the bottomed hole 50. This bubble pool absorbs the impact pressure generated when the bubbles in the cavitation jet 49 collapse. That is, the bubble pool serves as a cushion that absorbs the impact pressure. As a result, the force that contributes to erosion can be attenuated, and erosion can be suppressed.

On the other hand, when an annular opening (annular drawing portion 48) is formed by the edge 45 of the spool 39 and the spool sliding hole 33 (switching portion 36) of the housing 32, the opening (throttle portion 47) is formed by the notch 46. ) Is formed, the cavitation jet 49 and the collision portion of the jet 49 are dispersed, so that the risk of erosion is low. Moreover, since most of the generated cavitation jet 49 flows along the stepped surface 43 other than the bottomed hole 50, it is possible to prevent the streamline from becoming complicated. That is, since most of the cavitation jet 49 can be smoothly flowed along the shape of the oil groove 44 of the spool 39, an increase in flow loss can be suppressed.

As a result, both suppression of erosion and suppression of flow loss can be achieved. That is, in the embodiment, under the condition that cavitation is generated by the notch 46 having a high contribution to erosion, the bottomed hole 50 can effectively suppress the erosion at the collision portion of the jet 49. On the other hand, under the condition that the jet 49 is dispersed and cavitation is caused by the annular edge 45 having a relatively low contribution to erosion, it is possible to suppress the occurrence of unnecessary flow loss. As a result, the life of the spool valve device (direction control valve 31) for erosion can be extended while suppressing the flow loss.

According to the first embodiment, the bottomed hole 50 is provided on the inner diameter side of the deepest portion 46A of the notch 46 in the radial direction of the spool 39. As a result, the cavitation jet 49, which is ejected from the notch 46 of the spool 39 and flows toward the inner diameter side of the spool 39, can be stably (effectively) flowed into the bottomed hole 50.

According to the first embodiment, the bottomed hole 50 is provided at a position of the stepped surface 43 corresponding to the notch 46 in the circumferential direction of the spool 39. As a result, the cavitation jet 49, which is ejected from the notch 46 of the spool 39 and flows in the axial direction of the spool 39, can be stably (effectively) flowed into the bottomed hole 50.

According to the embodiment, the bottomed hole 50 is a circular hole, the inner diameter Db of the bottomed hole 50 is 1 to 3 times the diameter Dj of the cavitation jet 49, and the depth Hb of the bottomed hole 50 is. It is larger than 1/2 (half) of the inner diameter Db of the bottomed hole 50. Therefore, the bottomed hole 50 can be easily machined, and a bubble pool can be reliably formed in the bottomed hole 50. As a result, under the condition that cavitation is generated by the notch 46 having a high contribution to erosion, erosion at the jet collision portion (step surface 43) is more effectively suppressed, and the spool valve device for erosion is suppressed while suppressing the manufacturing cost. The life of the (direction control valve 31) can be extended.

Next, FIG. 7 shows a second embodiment. The feature of the second embodiment is that the bottomed hole is provided over the stepped surface and the outer peripheral surface of the small diameter portion, and the bottomed hole is provided so as to coincide with or parallel to the streamline of the cavitation jet. 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.

Similar to the first embodiment, the second embodiment also collects the gas contained in the working fluid as bubbles on the stepped surface 43 of the spool 39 where the hydraulic oil flowing from the pump port 37 on the high pressure side collides. A bottomed hole 51 is provided. Here, in the first embodiment, the bottomed hole 50 is provided on the stepped surface 43. On the other hand, in the second embodiment, the bottomed hole 51 is provided over the stepped surface 43 and the outer peripheral surface 42A of the small diameter portion 42. That is, the bottomed hole 51 is open to the stepped surface 43 and the outer peripheral surface 42A of the small diameter portion 42.

Further, the bottomed hole 51 is parallel to the streamline of the cavitation jet 49 ejected from the notch 46 and directed toward the stepped surface 43. That is, the bottomed hole 51 extends in the same direction as the cavitation jet 49 travels. Therefore, the central axis of the bottomed hole 51 goes toward the inner part (bottom) of the bottomed hole 51 so as to be parallel to the streamline of the cavitation jet 49 ejected from the notch 46, and the central axis of the spool 39. It is tilted in the direction of approaching. The term "parallel" here includes not only perfect parallelism but also some deviation within the range in which the cavitation jet 49 can stably flow into the inner part of the bottomed hole 51. Further, the bottomed hole may be made to coincide with (or substantially coincide with) the streamline of the cavitation jet. That is, the central axis of the bottomed hole and the streamline of the cavitation jet may be aligned (or almost coincident) on the same straight line.

The second embodiment is to store the gas contained in the working fluid as bubbles by the bottomed hole 51 as described above, and its basic operation is exceptionally different from that according to the first embodiment described above. There is no. In particular, according to the second embodiment, the bottomed hole 51 is provided over the stepped surface 43 and the outer peripheral surface 42A of the small diameter portion 42. As a result, the cavitation jet 49, which is ejected from the notch 46 of the spool 39 and flows toward the inner diameter side of the spool 39, is stably (effectively) flowed into the bottomed hole 51 without colliding with other parts. be able to. In addition to this, according to the second embodiment, the bottomed hole 51 is parallel to the streamline of the cavitation jet 49 ejected from the notch 46 toward the stepped surface 43. As a result, the cavitation jet 49 can be stably (effectively) flowed into the deep part (bottom) of the bottomed hole 51, and can be stably (effectively) flowed out from the bottomed hole 51. ..

Next, FIGS. 8 to 11 show a third embodiment. The feature of the third embodiment is that a bottomed hole such as a keyway is provided. In the third 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.

Similar to the first embodiment, the third embodiment also collects the gas contained in the working fluid as bubbles on the stepped surface 43 of the spool 39 where the hydraulic oil flowing from the pump port 37 on the high pressure side collides. A bottomed hole 61 is provided. In the third embodiment, a bottomed hole 61 shaped like a key groove is provided on the stepped surface 43 of the spool 39 so as to open perpendicularly to the central axis of the spool 39. As shown in FIG. 9, the opening of the bottomed hole 61 has a substantially quadrangular shape.

As shown in FIG. 10, the bottom surface of the bottomed hole 61 is a curved concave recessed surface 61A. That is, the bottomed hole 61 has an R-shaped bottom surface (concave concave surface 61A). Here, the radius of the concave recessed surface 61A of the bottomed hole 61 is Rr, the diameter of the cavitation jet 49 ejected from the notch 46 toward the stepped surface 43 is Dj, and the width of the bottomed hole 61 in the circumferential direction of the spool 39. The dimension is Wr, and the depth of the bottomed hole 61 is Hr. In this case, the radius Rr of the recessed surface 61A is larger than the diameter Dj of the cavitation jet 49. That is, as shown in the following equation (4), the radius Rr of the recessed surface 61A is at least larger than the diameter of the cavitation jet 49 (jet diameter Dj) generated at the notch 46. In other words, the dimension of the bottomed hole 61 in the radial direction of the spool 39 is the diameter Dj of the cavitation jet 49 on the stepped surface 43 (that is, the diameter Dj at a position L away from the outlet of the notch 46). It's more than doubled.

Further, the width dimension Wr of the bottomed hole 61 is 1 time or more and 2 times or less the diameter Dj of the cavitation jet 49. That is, the relationship between the width dimension Wr of the bottomed hole 61 (width dimension Wr in the circumferential direction of the spool 39) and the diameter Dj of the cavitation jet 49 is set to be the following equation (5).

Further, the depth Hr of the bottomed hole 61 (the depth Hr from the stepped surface 43 in the axial direction of the spool 39) is the streamline of the cavitation jet 49 flowing into the bottomed hole 61 and the cavitation flowing out from the bottomed hole 61. The depth Hr is such that the angle formed by the streamline of the jet 49 is 0 ° to 90 ° (0 ° ≤ angle formed ≤ 90 °). As a result, the cavitation jet 49 that has flowed into the bottomed hole 61 can flow so as to fold back along the curved surface (bottom surface) of the concave recessed surface 61A of the bottomed hole 61, and the opening of the bottomed hole 61. It can be drained at an angle of 0 ° to 90 °. At this time, as shown in FIG. 11, the cavitation jet 49 can smoothly flow on the bottom surface (recessed recessed surface 61A) of the bottomed hole 61, and a swirling flow can be formed in the bottomed hole 61. Since the swirling flow collects air bubbles having a light specific density at the center of swirling, a stable air bubble pool can be formed in the bottomed hole 61. As a result, the impact pressure generated when the cavitation bubbles collapse can be effectively absorbed.

The third embodiment is to store the gas contained in the working fluid as bubbles by the bottomed hole 61 as described above, and its basic operation is exceptionally different from that according to the first embodiment described above. There is no. In particular, according to the third embodiment, the bottom surface of the bottomed hole 61 is a curved concave recessed surface 61A. Further, the radius Rr of the recessed surface 61A is made larger than the diameter Dj of the cavitation jet 49. Further, the width dimension Wr of the bottomed hole 61 is set to be 1 time or more and 2 times or less the diameter Dj of the cavitation jet 49. Further, the angle formed by the depth Hr of the bottomed hole 61 between the streamline of the cavitation jet 49 flowing into the bottomed hole 61 and the streamline of the cavitation jet 49 flowing out of the bottomed hole 61 is 0 ° to 90 °. It is set to be.

Therefore, the flow direction inflowing into the bottomed hole 61 and the flow direction outflowing can be shifted from the same straight line. As a result, a strong swirling flow can be reliably generated in the bottomed hole 61. Then, when a swirling flow is generated, a bubble pool can be stably formed in the low pressure portion at the center of the swirling flow. Therefore, under the condition that cavitation is generated by the notch 46 having a high contribution to erosion, erosion at the jet collision portion (step surface 43) is more effectively suppressed, and the spool valve device (direction control valve 31) for erosion is provided. The life can be extended.

Next, FIG. 12 shows a fourth embodiment. The feature of the fourth embodiment is that the bottomed hole is provided over the stepped surface and the outer peripheral surface of the small diameter portion, and the bottomed hole is provided parallel to the streamline of the cavitation jet. In the fourth embodiment, the same components as those in the third embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.

Similarly to the third embodiment, the fourth embodiment also has a concave recessed surface 71A in which the bottom surface of the bottomed hole 71 is curved. Here, in the third embodiment, the bottomed hole 61 is provided on the stepped surface 43. On the other hand, in the fourth embodiment, the bottomed hole 71 is provided over the stepped surface 43 and the outer peripheral surface 42A of the small diameter portion 42. That is, the bottomed hole 71 is open to the stepped surface 43 and the outer peripheral surface 42A of the small diameter portion 42. In this case, the depth dimension of the bottomed hole 71 (the depth dimension of the spool 39 in the axial direction and the depth dimension of the spool 39 in the radial direction) is such that the cavitation jet 49 flowing into the bottomed hole 71 is bottomed. It can be flowed so as to be folded back along the curved surface (bottom surface) of the concave recessed surface 71A of the hole 71, and can be discharged from the opening of the bottomed hole 71 at an angle of 0 ° to 90 °. Set.

Further, the bottomed hole 71 is parallel to the streamline of the cavitation jet 49 ejected from the notch 46 and directed toward the stepped surface 43. That is, the bottomed hole 71 extends in the same direction as the direction in which the cavitation jet 49 advances. Therefore, the central axis of the bottomed hole 71 goes toward the inner part (bottom) of the bottomed hole 71 so as to be parallel to the streamline of the cavitation jet 49 ejected from the notch 46, and the central axis of the spool 39. It is tilted in the direction of approaching. The term "parallel" here includes not only perfect parallelism but also some deviation within a range in which the cavitation jet 49 can stably flow into the inner part of the bottomed hole 71.

The fourth embodiment is to store the gas contained in the working fluid as bubbles by the bottomed hole 71 as described above, and its basic operation is exceptionally different from that according to the third embodiment described above. There is no. In particular, according to the fourth embodiment, the bottomed hole 71 is provided over the stepped surface 43 and the outer peripheral surface 42A of the small diameter portion 42. As a result, the cavitation jet 49, which is ejected from the notch 46 of the spool 39 and flows toward the inner diameter side of the spool 39, is stably (effectively) flowed into the bottomed hole 71 without colliding with other parts. be able to. In addition to this, according to the fourth embodiment, the bottomed hole 71 is parallel to the streamline of the cavitation jet 49 ejected from the notch 46 toward the stepped surface 43. As a result, the cavitation jet 49 can be stably (effectively) flowed into the inner part (bottom) of the bottomed hole 71. In this case, a swirling flow can be stably formed in the bottomed hole 71, and the impact pressure generated when the bubbles of the cavitation jet 49 collapse can be effectively absorbed.

In the first embodiment described above, a case where one notch 46 is provided on the edge 45 of the spool 39 has been described as an example. However, the present invention is not limited to this, and for example, a plurality of notches may be formed at the edge of the spool (the boundary portion between the large diameter portion and the stepped surface) at equal intervals in the circumferential direction. In this case, bottomed holes can be provided on the stepped surface according to the number of notches. For example, a plurality of bottomed holes may be provided on the stepped surface so as to be paired with each of the plurality of notches so as to face each of the notches in the axial direction. This also applies to the second embodiment, the third embodiment, and the fourth embodiment.

In the first embodiment described above, the case where the width dimension and the depth dimension of the notch 46 are a constant square notch with respect to the axial direction of the spool 39 has been described as an example. However, the present invention is not limited to this, and for example, a V notch may be used. More specifically, the width dimension of the notch may be reduced as the distance from the stepped surface increases. Further, the width dimension of the notch may be made shallower as the distance from the stepped surface increases. That is, as the notch, notches of various shapes can be adopted. Then, the position of the bottomed hole, the cross-sectional shape, the inner diameter dimension, the width dimension, the depth dimension, etc. can be set according to the shape (cross-sectional shape) of the cavitation jet formed according to the shape of the notch and the ejection direction. can. For example, the shorter the axial length of the notch, the more the cavitation jet tends to eject inward in the radial direction of the spool. Further, the spread of the cavitation jet also changes depending on the shape of the notch (for example, the inclination angle of the inner surface of the V notch with respect to the axial direction, the width dimension in the circumferential direction, etc.). In consideration of these, the position, cross-sectional shape, inner diameter dimension, width dimension, depth dimension, etc. of the bottomed hole are calculated, for example, so that the bubbles of the cavitation jet ejected from the notch can be accumulated in the bottomed hole. , Experiment, simulation, etc. to set appropriately. This also applies to the second embodiment, the third embodiment, and the fourth embodiment.

In the first embodiment described above, the port on the high pressure side is the pump port 37, and when the hydraulic oil flows from the pump port 37 toward the actuator port 38, the stepped surface 43 of the spool 39 with which the hydraulic oil collides. The case where the bottomed hole 50 is provided corresponding to the notch 46 is described as an example. However, the present invention is not limited to this, for example, the port on the high pressure side is used as an actuator port, and when the hydraulic oil flows from this actuator port toward the tank port, the step surface of the spool on which the hydraulic oil collides corresponds to the notch. A bottomed hole may be provided. This also applies to the second embodiment, the third embodiment, and the fourth embodiment.

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

In each embodiment, an engine-type hydraulic excavator 1 driven by an engine 12 has been described as an example of a construction machine. However, the present invention is not limited to this, and can be applied to, for example, a hybrid type hydraulic excavator driven by an engine and an electric motor, and an electric type hydraulic excavator driven by an electric motor. Further, it can be applied not only to hydraulic excavators but also to various construction machines such as wheel loaders, hydraulic cranes and bulldozers. Further, it is not limited to construction machinery, and can be widely applied as a spool valve device incorporated in industrial machinery and general machinery. Further, it is needless to say that each embodiment is an example, 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 Flood control circuit 11A Main flood control circuit 11B Pilot flood control circuit 16 Return pipeline (pipeline)
31 Directional control valve (spool valve device)
32 Housing 33 Spool sliding hole 37 Pump port (port)
38 Actuator port (port)
39 Spool 40 Central large diameter part (large diameter part, land)
41 Large diameter on one side (large diameter, land)
42 Small diameter (neck)
42A Peripheral surface 43 Step surface 44 Oil groove (neck)
45 edge (boundary)
46 Notch 46A Deepest part 49 Cavitation jet 50, 51, 61, 71 Bottomed hole 61A, 71A Recessed surface Db Inner diameter of bottomed hole Hb, Hr Depth of bottomed hole Dj Diameter of cavitation jet Rr Radius of recessed surface Wr bottomed hole width dimension

Claims (7)

A tubular housing having spool sliding holes and provided with a plurality of ports separated from each other in the axial direction of the spool sliding holes.
A spool that is movably inserted into the spool sliding hole of the housing and has a large diameter portion that serves as a land for communicating or blocking between the ports and a small diameter portion that serves as a constriction so as to be adjacent to each other in the axial direction. When,
It is located at the boundary between the stepped surface connecting the large-diameter portion and the small-diameter portion of the spool and the large-diameter portion, and is provided on the large-diameter portion. In a spool valve device provided with a notch for communicating at a small flow rate
When the ports communicate with each other through the notch, the stepped surface of the spool where the hydraulic oil flowing from the port on the high pressure side collides is provided with a bottomed hole for collecting the gas contained in the working fluid as bubbles. A spool valve device characterized by. In the spool valve device according to claim 1,
A spool valve device characterized in that the bottomed hole is provided over the stepped surface and the outer peripheral surface of the small diameter portion. In the spool valve device according to claim 1,
The spool valve device is characterized in that the bottomed hole is provided on the inner diameter side of the deepest portion of the notch in the radial direction of the spool. In the spool valve device according to claim 1,
The spool valve device is characterized in that the bottomed hole is provided at a position corresponding to the notch in the circumferential direction of the spool on the stepped surface. In the spool valve device according to claim 1,
A spool valve device characterized in that the bottomed hole is parallel to the streamline of a cavitation jet ejected from the notch and directed to the stepped surface. In the spool valve device according to claim 1,
The bottomed hole is a circular hole and has a circular hole.
When the inner diameter of the bottomed hole is Db, the depth of the bottomed hole is Hb, and the diameter of the cavitation jet ejected from the notch toward the stepped surface is Dj.
The inner diameter Db of the bottomed hole is 1 time or more and 3 times or less the diameter Dj of the cavitation jet.
A spool valve device characterized in that the depth Hb of the bottomed hole is larger than 1/2 of the inner diameter Db of the bottomed hole. In the spool valve device according to claim 1,
The bottom surface of the bottomed hole is a curved concave recessed surface.
The radius of the concave recessed surface of the bottomed hole is Rr, the diameter of the cavitation jet ejected from the notch toward the stepped surface is Dj, and the width dimension of the bottomed hole with respect to the circumferential direction of the spool is Wr. When the depth of the bottomed hole is Hr,
The radius Rr of the concave surface is larger than the diameter Dj of the cavitation jet.
The width dimension Wr of the bottomed hole is 1 time or more and 2 times or less the diameter Dj of the cavitation jet.
The depth Hr of the bottomed hole is such that the angle formed by the streamline of the cavitation jet flowing into the bottomed hole and the streamline of the cavitation jet flowing out of the bottomed hole is 0 ° to 90 °. A spool valve device characterized by being a cavitation.

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