Valve device

Abstract

To improve stabilization of flow of hydraulic oil in a valve device that controls flow of hydraulic oil supplied / discharged to / from a plurality of hydraulic actuators of a construction machine.SOLUTION: A valve device according to one embodiment is a valve device for a construction machine that controls a flow of hydraulic oil supplied / discharged to / from a plurality of hydraulic actuators including a boom cylinder, and comprises: a first spool and a second spool spaced apart from each other in an axial direction; a plurality of spool holes including a spool hole for a boom cylinder into which the first spool and the second spool are inserted; and a housing having a first pump passage, a second pump passage, a first tank passage, a second tank passage, a rod side passage, and a head side passage, where an annular space around one of the small diameter parts of the first spool communicates with the first tank passage when the first spool is in at least a first neutral position, and an annular space around one of the small diameter parts of the second spool communicates with the second tank passage when the second spool is in at least a second neutral position.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a valve device that controls the flow of hydraulic oil supplied to and discharged from a plurality of hydraulic actuators equipped in a construction machine. [Background technology]

[0002] Patent Document 1 discloses a valve device including a housing having a pump passage, a first supply / discharge passage, a second supply / discharge passage, and a tank passage, and having a first pilot chamber, a second pilot chamber, and a third pilot chamber formed therein, and a first spool and a second spool that are independent of each other. The valve device is called a "directional / flow control valve" in Patent Document 1. In this valve device, since the first spool and the second spool are independent of each other, the first spool can be moved according to the pressure difference between the first pilot chamber and the third pilot chamber, and the second spool can be moved according to the pressure difference between the second pilot chamber and the third pilot chamber. This enables independent metering control on the meter-in side or the meter-out side regardless of which direction the hydraulic actuator operates in. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 080311 Summary of the Invention [Problem to be solved by the invention]

[0004] Construction machinery such as hydraulic excavators and hydraulic cranes are equipped with multiple hydraulic actuators. When the valve gear of Patent Document 1 is applied to a valve gear for individually operating multiple hydraulic actuators of a construction machinery, there is room for improvement in terms of stabilizing the flow of hydraulic oil.

[0005] Therefore, an object of the present disclosure is to improve the stability of the flow of hydraulic oil in a valve device that controls the flow of hydraulic oil supplied to and discharged from multiple hydraulic actuators of a construction machine. [Means for solving the problem]

[0006] A valve device according to one aspect of the present disclosure is a valve device for a construction machine that controls a flow of hydraulic oil supplied to and discharged from a plurality of hydraulic actuators including a boom cylinder, the valve device comprising: a first spool and a second spool spaced apart from each other in an axial direction; a plurality of spool holes including a boom cylinder spool hole into which the first spool and the second spool are inserted; a first pump passage, a second pump passage, a first tank passage, and a second tank passage connected to the boom cylinder spool hole; a rod side passage connected to the boom cylinder spool hole and connected to a rod side chamber of the boom cylinder; a head side passage connected to the boom cylinder spool hole and connected to a head side chamber of the boom cylinder; and a first pilot chamber and a second pilot chamber located on both sides of the boom cylinder spool hole, wherein a portion of the boom cylinder spool hole between the first spool and the second spool constitutes a third pilot chamber, each of the first tank passage and the second tank passage intersects with the plurality of spool holes, and the first spool is connected to the first pilot chamber. the second spool moves between a first neutral position where the rod side passage is blocked from both the first pump passage and the first tank passage and a first boom drive position where the rod side passage is communicated with either the first pump passage or the first tank passage in response to a pressure difference between a pilot chamber and the third pilot chamber, and the second spool moves between a second neutral position where the head side passage is blocked from both the second pump passage and the second tank passage and a first boom drive position where the rod side passage is communicated with either the first pump passage or the first tank passage in response to a pressure difference between the second pilot chamber and the third pilot chamber. a second boom drive position for communicating with either one of the first spool and the second spool, and each of the first spool and the second spool includes three or more land portions spaced apart in the axial direction and two or more small diameter portions connecting adjacent ones of the land portions, an annular space around one of the two or more small diameter portions of the first spool communicates with the first tank passage when the first spool is in at least the first neutral position, and an annular space around one of the two or more small diameter portions of the second spool communicates with the first tank passage when the first spool is in at least the first neutral position,The second spool communicates with the second tank passage at least when the second spool is in the second neutral position.

[0007] A valve device according to another aspect of the present disclosure is a valve device for a construction machine that controls a flow of hydraulic oil supplied to and discharged from a plurality of hydraulic actuators including a boom cylinder, the valve device comprising: a first spool and a second spool spaced apart from each other in the axial direction; a plurality of spool holes including a boom cylinder spool hole into which the first spool and the second spool are inserted; a first pump passage, a second pump passage, a first tank passage, and a second tank passage connected to the boom cylinder spool hole; a rod side passage connected to the boom cylinder spool hole and connected to a rod side chamber of the boom cylinder; a head side passage connected to the boom cylinder spool hole and connected to a head side chamber of the boom cylinder; and a first pilot chamber and a second pilot chamber located on both sides of the boom cylinder spool hole, wherein a portion of the boom cylinder spool hole between the first spool and the second spool constitutes a third pilot chamber, and the first spool has a first pump side land portion that opens and closes between the rod side passage and the first pump passage, and a second pilot chamber that opens and closes between the rod side passage and the first pump passage. the second spool includes a first tank side land portion that opens and closes between the head side passage and the first tank passage, and a first small diameter portion that connects the first pump side land portion and the first tank side land portion, and the second spool includes a second inner land portion that isolates the second pump passage from a third pilot chamber, a second intermediate land portion that opens and closes between the head side passage and the second pump passage and also between the head side passage and the second tank passage, a second outer land portion that isolates the second tank passage from a second pilot chamber, and a first small diameter portion that connects the second inner land portion and the second intermediate land portion. and a second inner small diameter portion connecting the second outer land portion and the second intermediate land portion, and a second outer small diameter portion connecting the second outer land portion and the second intermediate land portion, the first pump side land portion having a plurality of first notches arranged at intervals in the circumferential direction at an end portion on the first small diameter portion side of the outer peripheral surface of the first pump side land portion for communicating between the rod side passage and the first pump passage, and at least one of the plurality of first notches has a taper whose depth decreases as it moves away from the end face of the first pump side land portion to which the first small diameter portion is connected. Effect of the Invention

[0008] According to the present disclosure, in a valve device that controls the flow of hydraulic oil supplied to and discharged from a plurality of hydraulic actuators of a construction machine, it is possible to improve the stability of the flow of hydraulic oil. [Brief description of the drawings]

[0009] [Figure 1] 1 is a side view of a hydraulic excavator on which a valve device according to an embodiment is mounted. [Diagram 2] FIG. 2 is a diagram showing a portion of a hydraulic circuit including a valve device. [Diagram 3] FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 13 is a diagram illustrating a state in which the spaced spool in the valve device is in a boom lowered position. [Figure 6] 13 is a diagram illustrating a state in which the spaced spool in the valve device is in a boom-raising position. FIG. [Figure 7] FIG. 2 is a side cross-sectional view of a spaced spool taken along a plane parallel to the axial direction. [Figure 8] 6 is a graph showing the relationship between the stroke amount of a spool and the opening area of ​​a meter-in passage when the boom is lowered. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a valve device according to an embodiment will be described with reference to the drawings.

[0011] 1 is a side view of a hydraulic excavator 1 on which a valve device according to this embodiment is mounted. The hydraulic excavator 1 is self-propelled and includes a running body 2. The hydraulic excavator 1 also includes a rotating body 3 rotatably supported on the running body 2, and a boom that moves up and down relative to the rotating body 3. An arm is swingably connected to the tip of the boom, and a bucket is swingably connected to the tip of the arm. A cabin 4 in which a driver's seat is installed is disposed on the rotating body 3. The hydraulic excavator 1 does not have to be self-propelled.

[0012] The hydraulic excavator 1 includes a plurality of hydraulic actuators 5. Specifically, the hydraulic excavator 1 includes, as the hydraulic actuators 5, a boom cylinder 5A for raising and lowering the boom, an arm cylinder 5B for swinging the arm, and a bucket cylinder 5C for swinging the bucket. Although not shown, the hydraulic excavator 1 may also include, as bidirectional hydraulic actuators, a left traveling motor for driving the left crawler of the traveling body 2, a right traveling motor for driving the right crawler, and a swing motor for swinging the swing body 3. The flow of hydraulic oil supplied to and discharged from these plurality of hydraulic actuators 5 is controlled by the valve device of this embodiment.

[0013] Fig. 2 is a diagram showing a part of a hydraulic circuit including the valve device 10 of this embodiment. Specifically, Fig. 2 shows only a circuit related to supply and discharge control for the boom cylinder 5A among the multiple hydraulic actuators 5, and omits circuits related to supply and discharge control for the other hydraulic actuators 5. The valve device 10 controls the flow of hydraulic oil supplied from the hydraulic pump 6 to the multiple hydraulic actuators 5. The valve device 10 is interposed between the hydraulic pump 6 and the multiple hydraulic actuators 5 in the hydraulic circuit.

[0014] As shown in FIG. 2, boom cylinder 5A includes a rod side chamber 5a to which hydraulic oil is supplied when the boom is lowered, i.e., when the boom is driven in the direction of gravity, and a head side chamber 5b to which hydraulic oil is supplied when the boom is raised, i.e., when the boom is driven in the anti-gravity direction.

[0015] Fig. 3 is a top view of the valve device 10. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3. As shown in Fig. 3, the valve device 10 includes a housing 11 and a plurality of spools 12 slidably held in the housing 11.

[0016] The housing 11 includes a housing main body 11A having a substantially rectangular parallelepiped shape and a block 11B extending along one side of the housing main body 11A. The housing 11 also includes first covers 11C and second covers 11D, the number of which is the same as the number of spools 12. However, the configuration of the housing 11 is not limited to this and can be changed as appropriate.

[0017] The housing body 11A includes a first surface 21 facing downward and a second surface 22 facing upward. The housing body 11A also includes a plurality of spool holes 23. As shown in FIG. 4, each spool hole 23 extends in the vertical direction. Each spool hole 23 penetrates the housing body 11A in the vertical direction and opens to the first surface 21 and the second surface 22. The plurality of spool holes 23 are parallel to one another. That is, like the spool holes 23, the plurality of spools 12 are also parallel to one another and extend in the vertical direction.

[0018] 3, the multiple spool holes 23 are arranged in a line perpendicular to the up-down direction. The multiple spools 12 are held in the housing body 11A in a state where they are arranged in a line perpendicular to the up-down direction.

[0019] The multiple spool holes 23 correspond to the multiple hydraulic actuators 5, respectively. That is, the number of the spool holes 23 is the same as the number of the hydraulic actuators 5. The corresponding hydraulic actuator 5 is controlled by the spool 12 sliding in each spool hole 23. As shown in FIG. 3, the number of the spool holes 23 is five. For example, the multiple spool holes 23 include a spool hole 23A for the boom cylinder 5A. The multiple spool holes 23 also include a spool hole for the arm cylinder 5B and a spool hole for the bucket cylinder 5C. The number of the spool holes 23 may be four or less or six or more. The number of the spool holes 23 may be different from the number of the hydraulic actuators 5.

[0020] The cross-sectional view of Fig. 4 is a view cut along the center line of spool hole 23A for boom cylinder 5A among the multiple spool holes 23. As shown in Fig. 4, spool 12A for the boom cylinder inserted into spool hole 23A for the boom cylinder is a spaced spool. That is, spool 12A for the boom cylinder includes first spool 50 and second spool 60 spaced apart from each other in the axial direction within spool hole 23A. First spool 50 is located below second spool 60. Details of first spool 50 and second spool 60 will be described later.

[0021] In this embodiment, although not shown in Figures 3 and 4, a pump port 24a and a tank port 24b are arranged on one surface of the housing body 11A. As shown in Figure 2, the pump port 24a is connected to the hydraulic pump 6 by a pipe, and the tank port 24b is connected to the tank 7 by a pipe.

[0022] As shown in FIG. 2, the housing body 11A has a supply passage 25 extending from the pump port 24a to all the spool holes 23. The supply passage 25 includes a transverse passage 25c extending in the arrangement direction of the spool 12 near the center of the spool hole 23, and a first pump passage 25a and a second pump passage 25b that guide the hydraulic oil from the transverse passage 25c to the boom cylinder spool hole 23A. A check valve 26 is disposed between the transverse passage 25c in the supply passage 25 and the first pump passage 25a and the second pump passage 25b. The check valve 26 prevents the hydraulic oil from flowing back from the spool hole 23A to the transverse passage 25c. As shown in FIG. 4, the second pump passage 25b is connected to the spool hole 23A above the first pump passage 25a.

[0023] 2, the housing body 11A has discharge passages 27 that extend from all of the spool holes 23 to the tank port 24b. The discharge passages 27 include two passages, a first tank passage 27a and a second tank passage 27b, that extend in the arrangement direction of the spools 12 so as to pass through both ends of each spool hole 23, and an outlet passage 27c that connects the first tank passage 27a and the second tank passage 27b to the tank port 24b.

[0024] 3, the first tank passage 27a and the second tank passage 27b each extend so as to cross the multiple spool holes 23. In other words, the first tank passage 27a and the second tank passage 27b each intersect with the multiple spool holes 23.

[0025] 4, the first tank passage 27a and the second tank passage 27b are connected to the spool hole 23A outside the first pump passage 25a and the second pump passage 25b in the axial direction of the boom cylinder spool hole 23A. More specifically, the first tank passage 27a is connected to the spool hole 23A below the first pump passage 25a, and the second tank passage 27b is connected to the spool hole 23A above the second pump passage 25b.

[0026] As shown in Fig. 4, a rod side port 24c and a head side port 24d corresponding to the boom cylinder spool 12A are arranged on one surface of the housing body 11A. As shown in Fig. 2, the rod side port 24c is connected to the rod side chamber 5a of the boom cylinder 5A by piping, and the head side port 24d is connected to the head side chamber 5b of the boom cylinder 5A by piping.

[0027] The housing main body 11A includes a rod side passage 28. The rod side passage 28 connects between the rod side port 24c and the spool hole 23A. That is, the rod side passage 28 is connected to the rod side chamber 5a of the boom cylinder 5A through the rod side port 24c. As shown in FIG. 4, the rod side passage 28 is connected to the spool hole 23A on the opposite side of the second pump passage 25b with respect to the first pump passage 25a in the axial direction of the spool hole 23A, that is, below the first pump passage 25a. The rod side passage 28 is connected to the spool hole 23A between the first pump passage 25a and the first tank passage 27a in the axial direction of the spool hole 23A.

[0028] The housing main body 11A includes a head side passage 29. The head side passage 29 connects between the head side port 24d and the spool hole 23A. That is, the head side passage 29 is connected to the head side chamber 5b of the boom cylinder 5A through the head side port 24d. As shown in FIG. 4, the head side passage 29 is connected to the spool hole 23A on the opposite side of the first pump passage 25a with respect to the second pump passage 25b in the axial direction of the spool hole 23A, that is, above the second pump passage 25b. The head side passage 29 is connected to the spool hole 23A between the second pump passage 25b and the second tank passage 27b in the axial direction of the spool hole 23A.

[0029] The housing 11 has a first pilot chamber P1 and a second pilot chamber P2 located on both sides of the spool hole 23A. Specifically, the first cover 11C has a container-like shape. The first cover 11C is attached to the first surface 21 so that the opening edge of the first cover 11C surrounds the opening at the lower end of the spool hole 23A. In this way, the opening of the first cover 11C is closed by the first surface 21 of the housing main body 11A, thereby forming the first pilot chamber P1. In addition, the second cover 11D has a container-like shape. The second cover 11D is attached to the second surface 22 so that the opening edge of the second cover 11D surrounds the opening at the upper end of the spool hole 23A. In this way, the opening of the second cover 11D is closed by the second surface 22 of the housing main body 11A, thereby forming the second pilot chamber P2.

[0030] A first spring 31 is disposed in the first pilot chamber P1, which applies a biasing force to the first spool 50 to maintain the first spool 50 in a neutral position. The first spring 31 directly biases the first spool 50 toward the second spool 60 via a spring seat. Meanwhile, a headed rod 32 is attached to the end face of the first spool 50 opposite the second spool 60, and the first spring 31 biases the first spool 50 in the opposite direction to the second spool 60 via the spring seat and the headed rod 32.

[0031] Similarly, a second spring 33 is disposed within the second pilot chamber P2, which applies a biasing force to the second spool 60 to maintain the second spool 60 in a neutral position. The second spring 33 directly biases the second spool 60 toward the first spool 50 via a spring seat. Meanwhile, a headed rod 34 is attached to the end face of the second spool 60 opposite the first spool 50, and the second spring 33 biases the second spool 60 in the opposite direction to the first spool 50 via the spring seat and the headed rod 34.

[0032] The first spring 31 and the second spring 33 have the same configuration. That is, the biasing force that the first spring 31 applies to the first spool 50 is equal to the biasing force that the second spring 33 applies to the second spool 60. Note that the first spring 31 and the second spring 33 may have different configurations, and the biasing force that the first spring 31 applies to the first spool 50 may be different from the biasing force that the second spring 33 applies to the second spool 60.

[0033] The portion of boom cylinder spool hole 23A between first spool 50 and second spool 60 constitutes third pilot chamber P3. Boom cylinder spool 12A, which is a spaced spool, supplies and discharges hydraulic oil to boom cylinder 5A or prohibits the supply and discharge of hydraulic oil to boom cylinder 5A depending on the pressure in each pilot chamber, first pilot chamber P1, second pilot chamber P2, and third pilot chamber P3.

[0034] 2, the valve device 10 includes a first solenoid proportional valve 41 for adjusting the pressure of the first pilot chamber P1, a second solenoid proportional valve 42 for adjusting the pressure of the second pilot chamber P2, and a third solenoid proportional valve 43 for adjusting the pressure of the third pilot chamber P3. The first solenoid proportional valve 41 is connected to the first pilot chamber P1 through a pilot passage 44. The second solenoid proportional valve 42 is connected to the second pilot chamber P2 through a pilot passage 45. The third solenoid proportional valve 43 is connected to the third pilot chamber P3 through a pilot passage 46.

[0035] The valve device 10 includes a primary pressure passage 47 and a drain passage 48. The first solenoid proportional valve 41, the second solenoid proportional valve 42, and the third solenoid proportional valve 43 are connected to the primary pressure passage 47. The primary pressure passage 47 has a primary pressure port 24e in the housing 11. The primary pressure port 24e is connected to the auxiliary pump 8 by a primary pressure piping. The first solenoid proportional valve 41, the second solenoid proportional valve 42, and the third solenoid proportional valve 43 are connected to the drain passage 48. The drain passage 48 is connected to, for example, the tank 7.

[0036] The first solenoid proportional valve 41 outputs secondary pressure to a first pilot chamber P1 of the boom cylinder spool 12A, or communicates the first pilot chamber P1 with a drain passage 48. The second solenoid proportional valve 42 outputs secondary pressure to a second pilot chamber P2 of the boom cylinder spool 12A, or communicates the second pilot chamber P2 with a drain passage 48. The third solenoid proportional valve 43 outputs secondary pressure to a third pilot chamber P3 of the boom cylinder spool 12A, or communicates the third pilot chamber P3 with a drain passage 48.

[0037] The multiple spools 12 may include a spaced spool in addition to the spool 12A for the boom cylinder. The valve device 10 includes a set of a first solenoid proportional valve 41, a second solenoid proportional valve 42, and a third solenoid proportional valve 43 for the spaced spool. Among the multiple spools 12, the spools other than the spaced spool are integral spools. The integral spool supplies or discharges hydraulic oil to or inhibits the supply or discharge of hydraulic oil to the hydraulic actuator 5 corresponding to the integral spool, depending on the pressure of a first pilot chamber facing the lower end of the integral spool and a second pilot chamber facing the upper end of the integral spool. The valve device 10 includes a set of a first solenoid proportional valve 41 and a second solenoid proportional valve 42 for the integral spool.

[0038] In this embodiment, as shown in Fig. 3, the second electromagnetic proportional valve 42 corresponding to each spool 12 is attached to the block 11B. Similarly, the third electromagnetic proportional valve 43 corresponding to the separated type spool 12 is also attached to the block 11B. Meanwhile, the first electromagnetic proportional valve 41 corresponding to each spool 12 is attached to the first cover 11C. However, the method of attaching the first electromagnetic proportional valve 41, the second electromagnetic proportional valve 42, and the third electromagnetic proportional valve 43 to the housing 11 is not limited to this. For example, the first electromagnetic proportional valve 41 may be attached to the block 11B together with the second electromagnetic proportional valve 42 and the third electromagnetic proportional valve 43, or may be directly attached to the housing main body 11A.

[0039] (Details of the boom cylinder spool) Next, boom cylinder spool 12A will be described in more detail with reference to Figures 4 to 7. Boom cylinder spool 12A supplies and discharges hydraulic oil to and from boom cylinder 5A, or prohibits the supply and discharge of hydraulic oil to and from boom cylinder 5A, depending on the pressure in each pilot chamber, i.e., first pilot chamber P1, second pilot chamber P2, and third pilot chamber P3.

[0040] The first spool 50 switches whether the rod side passage 28 is connected to the supply passage 25 or the discharge passage 27, and the second spool 60 switches whether the head side passage 29 is connected to the supply passage 25 or the discharge passage 27.

[0041] The first spool 50 moves between a first neutral position, a first boom lowering position, and a first boom raising position in response to the pressure difference between the first pilot chamber P1 and the third pilot chamber P3. The second spool 60 moves between a second neutral position, a second boom lowering position, and a second boom raising position in response to the pressure difference between the second pilot chamber P2 and the third pilot chamber P3. FIG. 4 shows a state in which the first spool 50 is in the first neutral position and the second spool 60 is in the second neutral position. FIG. 5 shows a state in which the first spool 50 is in the first boom lowering position and the second spool 60 is in the second boom lowering position. FIG. 6 shows a state in which the first spool 50 is in the first boom raising position and the second spool 60 is in the second boom raising position. The first boom lowering position and the first boom raising position correspond to the first boom driving position, and the second boom lowering position and the second boom raising position correspond to the second boom driving position. 5 and 6, a part of the housing 11 is omitted.

[0042] 4, when the first spool 50 is in the first neutral position and the second spool 60 is in the second neutral position, the supply and discharge of hydraulic oil to the boom cylinder 5A is prohibited and the boom does not drive. More specifically, when the first spool 50 is in the first neutral position, the first spool 50 blocks the rod-side passage 28 from both the first pump passage 25a and the first tank passage 27a, and when the second spool 60 is in the second neutral position, the first spool 50 blocks the head-side passage 29 from both the second pump passage 25b and the second tank passage 27b.

[0043] As shown in FIG. 5, when the first spool 50 and the second spool 60 move closer to each other, the first spool 50 is in the first boom lowering position, and the second spool 60 is in the second boom lowering position. When the first spool 50 is in the first boom lowering position, the first spool 50 connects the rod-side passage 28 to the first pump passage 25a, and when the second spool 60 is in the second boom lowering position, the first spool 50 connects the head-side passage 29 to the second tank passage 27b. This causes hydraulic oil to be supplied to the rod-side chamber 5a of the boom cylinder 5A, and hydraulic oil to be discharged from the head-side chamber 5b. As a result, the boom is driven in the downward direction.

[0044] As shown in FIG. 6, when the first spool 50 and the second spool 60 move away from each other, the position of the first spool 50 becomes the first boom raising position, and the position of the second spool 60 becomes the second boom raising position. When the first spool 50 is in the first boom raising position, the first spool 50 connects the rod side passage 28 to the first tank passage 27a, and when the second spool 60 is in the second boom raising position, the first spool 50 connects the head side passage 29 to the second pump passage 25b. This causes hydraulic oil to be supplied to the head side chamber 5b of the boom cylinder 5A, and hydraulic oil to be discharged from the rod side chamber 5a. As a result, the boom is driven in the upward direction.

[0045] (Structure of the first spool) The first spool 50 includes a first inner land portion 51, a first inner small diameter portion 52, a first intermediate land portion 53, a first outer small diameter portion 54, and a first outer land portion 55. The first inner land portion 51, the first inner small diameter portion 52, the first intermediate land portion 53, the first outer small diameter portion 54, and the first outer land portion 55 are arranged in this order in a direction from the third pilot chamber P3 toward the first pilot chamber P1. That is, the first inner small diameter portion 52 connects the first inner land portion 51 and the first intermediate land portion 53, and the first outer small diameter portion 54 connects the first intermediate land portion 53 and the first outer land portion 55. The first inner land portion 51 corresponds to the first pump side land portion, the first intermediate land portion 53 corresponds to the first tank side land portion, and the first inner small diameter portion 52 corresponds to the first small diameter portion.

[0046] The first inner land portion 51, the first intermediate land portion 53, and the first outer land portion 55 slide relative to the spool hole 23A. The first inner small diameter portion 52 and the first outer small diameter portion 54 are smaller than the diameter of the spool hole 23A, in other words, the diameters of the land portions 51, 53, and 55 of the first spool 50. That is, annular spaces S1 and S2 into which the hydraulic oil flows are formed around the first inner small diameter portion 52 in the spool hole 23A and around the first outer small diameter portion 54 in the spool hole 23A, respectively. The diameter of the first outer small diameter portion 54 is larger than the diameter of the first inner small diameter portion 52.

[0047] The first inner land portion 51 isolates the first pump passage 25a from the third pilot chamber P3. The first inner land portion 51 also opens and closes the connection between the rod side passage 28 and the first pump passage 25a. The first intermediate land portion 53 opens and closes the connection between the rod side passage 28 and the first tank passage 27a. The first outer land portion 55 isolates the first tank passage 27a from the first pilot chamber P1.

[0048] When the first spool 50 is at least in the first neutral position, the first inner land portion 51 blocks communication between the rod side passage 28 and the first pump passage 25a, and the first intermediate land portion 53 blocks communication between the rod side passage 28 and the first tank passage 27a. As shown in Fig. 4, when the first spool 50 is in the first neutral position, the outer peripheral surface of the first inner land portion 51 blocks an end of the first pump passage 25a.

[0049] The annular space S2 around the first outer small diameter portion 54 communicates with the first tank passage 27a when the first spool 50 is at least in the first neutral position. As shown in Fig. 4, in this embodiment, the portion of the first tank passage 27a that intersects with the spool hole 23A and the first outer small diameter portion 54 have the same width in the axial direction of the spool hole 23A. Furthermore, when the first spool 50 is in the first neutral position, the entire first outer small diameter portion 54 overlaps the intersection portion of the first tank passage 27a with the spool hole 23A when viewed perpendicularly to the axial direction of the spool hole 23A.

[0050] However, the width in the axial direction of the spool hole 23A may be different between the portion of the first tank passage 27a that intersects with the spool hole 23A and the first outer small diameter portion 54. Furthermore, when the first spool 50 is in the first neutral position, it is preferable that more than half of the first outer small diameter portion 54 overlaps with the intersection of the first tank passage 27a with the spool hole 23A when viewed perpendicular to the axial direction of the spool hole 23A.

[0051] (Structure of the second spool) The second spool 60 includes a second inner land portion 61, a second inner small diameter portion 62, a second intermediate land portion 63, a second outer small diameter portion 64, and a second outer land portion 65. The second inner land portion 61, the second inner small diameter portion 62, the second intermediate land portion 63, the second outer small diameter portion 64, and the second outer land portion 65 are arranged in this order in a direction from the third pilot chamber P3 toward the second pilot chamber P2. That is, the second inner small diameter portion 62 connects the second inner land portion 61 and the second intermediate land portion 63, and the second outer small diameter portion 64 connects the second intermediate land portion 63 and the second outer land portion 65.

[0052] The second inner land portion 61, the second intermediate land portion 63, and the second outer land portion 65 slide relative to the spool hole 23A. The second inner small diameter portion 62 and the second outer small diameter portion 64 are smaller than the diameter of the spool hole 23A, in other words, the diameters of the land portions 61, 63, and 65 of the second spool 60. That is, annular spaces S3 and S4 into which the hydraulic oil flows are formed around the second inner small diameter portion 62 in the spool hole 23A and around the second outer small diameter portion 64 in the spool hole 23A, respectively.

[0053] The second inner land portion 61 isolates the second pump passage 25b from the third pilot chamber P3. The second intermediate land portion 63 opens and closes between the head side passage 29 and the second pump passage 25b, and also opens and closes between the head side passage 29 and the second tank passage 27b. The second outer land portion 65 isolates the second tank passage 27b from the second pilot chamber P2.

[0054] The annular space S4 around the second outer small diameter portion 64 communicates with the second tank passage 27b when the second spool 60 is at least in the second neutral position. As shown in Fig. 4, in this embodiment, the second outer small diameter portion 64 has a larger width in the axial direction of the spool hole 23A than the portion of the second tank passage 27b that intersects with the spool hole 23A. In addition, when the second spool 60 is in the second neutral position, more than half of the second outer small diameter portion 64 overlaps with the portion of the second tank passage 27b that intersects with the spool hole 23A when viewed perpendicularly to the axial direction of the spool hole 23A.

[0055] When the second spool 60 is at least in the second neutral position, the second intermediate land portion 63 blocks communication between the head side passage 29 and the second pump passage 25b, and also blocks communication between the head side passage 29 and the second tank passage 27b. As shown in Fig. 4, when the second spool 60 is in the second neutral position, the outer peripheral surface of the second intermediate land portion 63 blocks the end of the head side passage 29.

[0056] (notch) 4, the first inner land portion 51 has a plurality of first notches 51a for communicating between the rod side passage 28 and the first pump passage 25a. The plurality of first notches 51a are arranged at intervals in the circumferential direction at an end portion on the first inner small diameter portion 52 side of the outer circumferential surface of the first inner land portion 51. Each of the plurality of first notches 51a extends in the axial direction of the spool hole 23A from the end face of the first inner land portion 51 on the first inner small diameter portion 52 side.

[0057] The first intermediate land portion 53 has a plurality of second notches 53a for communicating between the rod side passage 28 and the first tank passage 27a. The plurality of second notches 53a are arranged at intervals in the circumferential direction at an end portion on the first inner small diameter portion 52 side of the outer circumferential surface of the first intermediate land portion 53. Each of the plurality of second notches 53a extends in the axial direction of the spool hole 23A from the end face of the first intermediate land portion 53 on the first inner small diameter portion 52 side.

[0058] The second intermediate land portion 63 has a plurality of third notches 63a for communicating between the head side passage 29 and the second pump passage 25b. The third notches 63a are arranged at intervals in the circumferential direction at an end portion on the second inner small diameter portion 62 side of the outer circumferential surface of the second intermediate land portion 63. Each of the third notches 63a extends in the axial direction of the spool hole 23A from the end face of the second intermediate land portion 63 on the second inner small diameter portion 62 side.

[0059] The second intermediate land portion 63 has a plurality of fourth notches 63b for communicating between the head-side passage 29 and the second tank passage 27b. The plurality of fourth notches 63b are arranged at intervals in the circumferential direction at an end portion on the second outer small diameter portion 64 side of the outer circumferential surface of the second intermediate land portion 63. The plurality of fourth notches 63b each extend in the axial direction of the spool hole 23A from an end face of the second intermediate land portion 63 on the second outer small diameter portion 64 side. The number of the plurality of fourth notches 63b is greater than the number of the plurality of third notches 63a.

[0060] Fig. 7 is a side cross-sectional view of the spaced spool taken along a plane parallel to the axial direction, in which the first notch 51a, the second notch 53a, the third notch 63a, the fourth notch 63b, as well as the shapes of the air vent passage 65a and the leak passages 81 and 82 described below are shown cut away for easy understanding.

[0061] As shown in FIG. 7, the first notch 51a and the second notch 53a have different bottom shapes from the third notch 63a and the fourth notch 63b. The bottoms of the first notch 51a and the second notch 53a are inclined radially outward as they move away from the end face of the land portion toward the axial center. More specifically, the first notch 51a has a taper that decreases in depth as it moves away from the end face of the first inner land portion 51 to which the first inner small diameter portion 52 is connected. The second notch 53a has a taper that decreases in depth as it moves away from the end face of the first intermediate land portion 53 to which the first inner small diameter portion 52 is connected. On the other hand, the bottoms of the third notch 63a and the fourth notch 63b are kept at a constant distance from the axial center of the spool 12A from one end to the other end in the axial direction.

[0062] (Air vent passage) The second outer land portion 65 has an air vent passage 65a. The air vent passage 65a extends in the second spool axial direction from the end face of the second outer land portion 65 facing the second pilot chamber P2. As shown in FIG. 4, the air vent passage 65a is disposed on the outer circumferential surface of the second outer land portion 65. That is, the air vent passage 65a is a notch extending in the axial direction on the outer circumferential surface of the second outer land portion 65 from the end face of the second outer land portion 65 facing the second pilot chamber P2. The air vent passage 65a may pass through the inside of the second outer land portion 65.

[0063] The air bleed passage 65a blocks the second pilot chamber P2 from the second tank passage 27b when the second spool 60 is in the second neutral position, and connects the second pilot chamber P2 to the second tank passage 27b when the second spool 60 moves a predetermined distance or more in a direction away from the second pilot chamber P2 from the neutral position.

[0064] The function of the air vent passage 65a will be described. More specifically, in the valve device 10 of this embodiment, the second spool 60 is located above the first spool 50. When time passes with the spool 12A not moving, such as when the construction machine is left unused for a certain period of time, air bubbles in the hydraulic oil in the first pilot chamber P1 and the spool hole 23A pass through the gap between the inner peripheral surface of the spool hole 23A and the outer peripheral surface of the spool 12A and gradually rise to the first pilot chamber P1 and the second pilot chamber P2, which is located above the spool hole 23A and includes the third pilot chamber P3. For this reason, air accumulates in the second pilot chamber P2 over time. In this way, even if air accumulates in the second pilot chamber P2, by performing, for example, a full stroke of the second spool 60 in a direction approaching the first spool 50 when starting to use the hydraulic excavator 1, the air accumulated in the second pilot chamber P2 can be released through the air vent passage 65a to the second tank passage 27b, which has a lower pressure than the second pilot chamber P2.

[0065] (Leak passage) As shown in FIG. 7, the first spool 50 has a first leak passage 81 extending from a portion located on the outer circumferential surface of the first inner land portion 51 closer to the third pilot chamber P3 than the connection point between the boom cylinder spool hole 23A and the first pump passage 25a to the first outer small diameter portion 54. The first leak passage 81 includes a first inlet port 81a and a first outlet port 81b. The first inlet port 81a is disposed in a portion of the first inner land portion 51 that blocks the first pump passage 25a from the third pilot chamber P3. The first outlet port 81b is disposed in the first outer small diameter portion 54. The portion of the first leak passage 81 between the first inlet port 81a and the first outlet port 81b passes through the inside of the first spool 50.

[0066] More specifically, a first leak groove 51b is provided on the outer circumferential surface of the first inner land portion 51. The first leak groove 51b is positioned on the outer circumferential surface of the first inner land portion 51 so as to always be located between the third pilot chamber P3 and the connection point of the first pump passage 25a in the boom cylinder spool hole 23A, even when the first spool 50 and the second spool 60 move away from each other. A first inlet port 81a is disposed in the first leak groove 51b.

[0067] The second spool 60 has a second leak passage 82 extending from a portion of the outer circumferential surface of the second inner land portion 61 that is closer to the third pilot chamber P3 than the connection point between the boom cylinder spool hole 23A and the second pump passage 25b to the second outer small diameter portion 64. The second leak passage 82 includes a second inlet port 82a and a second outlet port 82b. The second inlet port 82a is disposed in a portion of the second inner land portion 61 that blocks the second pump passage 25b from the third pilot chamber P3. The second outlet port 82b is disposed in the second outer small diameter portion 64. A portion of the second leak passage 82 between the second inlet port 82a and the second outlet port 82b passes through the inside of the second spool 60.

[0068] More specifically, a second leak groove 61a is provided on the outer circumferential surface of the second inner land portion 61. The second leak groove 61a is positioned on the outer circumferential surface of the second inner land portion 61 so as to always be located between the third pilot chamber P3 and the connection point of the second pump passage 25b in the boom cylinder spool hole 23A, even when the first spool 50 and the second spool 60 move away from each other. A second inlet port 82a is disposed in the second leak groove 61a.

[0069] (Identification mark) As shown in FIG. 4, the first spool 50 has a first identification mark 91 for identifying the first spool 50. The first identification mark 91 is disposed on the outer circumferential surface of the first inner small diameter portion 52. The first identification mark 91 is, for example, an engraving. The first identification mark 91 may be directly engraved on the small diameter portion of the first spool 50. Alternatively, the first identification mark 91 may be engraved on another member, such as a nameplate, attached to the small diameter portion of the first spool 50. The engraving may be, for example, a laser engraving or may be a marking using a punch or an air pen. The type of the first spool 50 can be ascertained by the first identification mark 91.

[0070] The first identification mark 91 includes not only information for identifying the first spool 50, but also information for identifying the first spring 31 that biases the first spool 50. Specifically, in this embodiment, the first cover 11C, the first spring 31, the headed rod 32, and the first spool 50 constitute a single unit that is integrally attached to the housing main body 11A, and the first identification mark 91 enables identification of this unit. In other words, the first identification mark 91 also makes it possible to ascertain the type of the first spring 31, etc.

[0071] In this embodiment, the first inner small diameter portion 52 is longer in the axial direction than the first outer small diameter portion 54. Therefore, since there is more space for arranging a mark on the outer peripheral surface of the first inner small diameter portion 52, the first identification mark 91 is arranged on the outer peripheral surface of the first inner small diameter portion 52, but the first identification mark 91 may be arranged on the first outer small diameter portion 54.

[0072] The second spool 60 has a second identification mark 92 for identifying the second spool 60. The second identification mark 92 is disposed on the outer circumferential surface of the second outer small diameter portion 64. The second identification mark 92 is, for example, an engraving. For example, the second identification mark 92 may be directly engraved on the small diameter portion of the second spool 60. Alternatively, the second identification mark 92 may be engraved on another member, such as a nameplate, attached to the small diameter portion of the second spool 60. The engraving may be, for example, a laser engraving or may be a marking using a punch or an air pen. The type of the second spool 60 can be ascertained by the second identification mark 92.

[0073] The second identification mark 92 includes not only information for identifying the second spool 60, but also information for identifying the second spring 33 that biases the second spool 60. Specifically, in this embodiment, the second cover 11D, the second spring 33, the headed rod 34, and the second spool 60 constitute a single unit that is integrally attached to the housing main body 11A, and the second identification mark 92 enables identification of this unit. In other words, the second identification mark 92 also makes it possible to ascertain the type of the second spring 33, etc.

[0074] In this embodiment, the second inner small diameter portion 62 and the second outer small diameter portion 64 have approximately the same axial length. Since the hydraulic pressure in the annular space S3 around the second inner small diameter portion 62 is lower than the hydraulic pressure in the annular space S4 around the second outer small diameter portion 64, in this embodiment, the second identification mark 92 is disposed on the outer circumferential surface of the second outer small diameter portion 64 so as to avoid exposure to high pressure as much as possible. However, the second identification mark 92 may be disposed on the second inner small diameter portion 62.

[0075] (Action and effect) As described above, in the valve device 10 of this embodiment, when the first spool 50 is in the first neutral position, the annular space S2 around the first outer small diameter portion 54 communicates with the first tank passage 27a, and when the second spool 60 is in the second neutral position, the annular space S4 around the second outer small diameter portion 64 communicates with the second tank passage 27b. This makes it possible to ensure a flow path cross-sectional area at the intersection of the first tank passage 27a and the second tank passage 27b with the boom cylinder spool hole 23A, and to reduce the pressure loss of the hydraulic oil flowing through the first tank passage 27a and the second tank passage 27b. This improves the stability of the flow of the hydraulic oil.

[0076] Incidentally, when the second spool 60 is moved to lower the boom and hydraulic oil flows from the head side passage 29 to the second tank passage 27b, the flow rate of hydraulic oil from the head side passage 29 to the second tank passage 27b is large. In this embodiment, when the second spool 60 is in the second neutral position, the end of the head side passage 29 is blocked by the outer circumferential surface of the second intermediate land portion 63. Therefore, when hydraulic oil flows from the head side passage 29 to the second tank passage 27b, the pressure of the head side passage 29 is received by the outer circumferential surface of the second intermediate land portion 63, and the pressure of the annular space S4 around the second outer small diameter portion 64 is kept low. Therefore, when the boom is lowered, the second spool 60 is less likely to receive the axial fluid force from the hydraulic oil.

[0077] Furthermore, in this embodiment, the number of the multiple fourth notches 63b is greater than the number of the multiple third notches 63a, so that the flow rate of hydraulic oil sent from the head side chamber 5b to the tank 7 through the multiple fourth notches 63b when lowering the boom can be increased.

[0078] In this embodiment, the first notches 51a have a taper that reduces the depth as it moves away from the end face of the first inner land portion 51 to which the first inner small diameter portion 52 is connected. This can prevent the amount of change in the opening area relative to the stroke of the first spool 50 when the boom is lowered from increasing. FIG. 8 is a graph showing the relationship between the stroke amount of the first spool 50 when the boom is lowered and the opening area of ​​the meter-in passage, in other words, the opening area of ​​the passage from the first pump passage 25a to the rod-side passage 28. As shown in FIG. 8, by making the first notches 51a have the above-mentioned tapered shape, the increase rate of the passage cross-sectional area surrounded by the first notches 51a and the inner circumferential surface of the spool hole 23A relative to the stroke amount of the first spool 50 is kept constant or approximately constant. This can prevent a large amount of hydraulic oil from flowing into the rod-side chamber 5a when the boom is lowered.

[0079] In addition, in this embodiment, hydraulic oil that leaks from the first pump passage 25a side between the outer peripheral surface of the first inner land portion 51 and the inner peripheral surface of the boom cylinder spool hole 23A can be discharged to the first tank passage 27a through the first leak passage 81, and hydraulic oil that leaks from the second pump passage 25b side between the outer peripheral surface of the second inner land portion 61 and the inner peripheral surface of the boom cylinder spool hole 23A can be discharged to the second tank passage 27b through the second leak passage 82.

[0080] In this embodiment, the first spool 50 has the first identification mark 91, and the second spool 60 has the second identification mark 92, making it possible to identify the first spool 50 and the second spool 60. In addition, the first identification mark 91 and the second identification mark 92 are disposed at locations that are not in contact with the housing 11, so deterioration of each identification mark can be suppressed.

[0081] In addition, in this embodiment, the diameter of the first outer small diameter portion 54 is larger than the diameter of the first inner small diameter portion 52. By making the diameter of the first outer small diameter portion 54 larger in this manner, it is possible to support the hydraulic pressure that is received in the axial direction by the end face of the first intermediate land portion 53 opposite to the first outer small diameter portion 54 when the hydraulic oil flows from the rod side passage 28 to the first tank passage 27a.

[0082] (Other embodiments) The present disclosure is not limited to the above-described embodiments, and the configuration can be changed, added, or deleted.

[0083] In the above embodiment, the valve device is mounted on a hydraulic excavator, but the construction machine on which the valve device is mounted is not limited to this. For example, the construction machine may be another construction machine equipped with a boom cylinder, such as a hydraulic crane.

[0084] In the above embodiment, the multiple spools 12 extend in the vertical direction, but the orientation of the spools 12 is not limited to this. For example, the attitude of the valve device can be freely determined depending on the construction machine in which the valve device is installed. For example, the multiple spools and multiple spool holes in the valve device may be inclined with respect to the vertical direction or may extend in the horizontal direction.

[0085] In the above embodiment, all of the multiple spools 12 are arranged in a row, but the arrangement of the multiple spools 12 is not limited to this. The multiple spools 12 may be arranged in two or more rows.

[0086] The shapes of the first spool 50 and the second spool 60 are not limited to those described in the above embodiment. For example, the axial width and diameter of the land portions and small diameter portions included in the first spool 50 and the second spool 60 can be changed as appropriate. For example, the diameter of the first outer small diameter portion 54 may be the same as the diameter of the first inner small diameter portion 52, or may be smaller than the diameter of the first inner small diameter portion 52.

[0087] In the above embodiment, the first spool 50 is configured to include three land portions 51, 53, and 55, but the first spool 50 may include four or more land portions. For example, the first inner land portion 51 may be configured to include a first sub-land portion and a second sub-land portion that are axially connected to each other by a small diameter portion. In this case, the first sub-land portion may open and close between the rod side passage 28 and the first pump passage 25a, and the second sub-land portion may block the first pump passage 25a from the third pilot chamber P3. In addition, the annular space around the small diameter portion that connects the first sub-land portion and the second sub-land portion may communicate with the first pump passage 25a when the first spool 50 is at least in the first neutral position. In addition, the first leak groove 51b may be disposed on the outer circumferential surface of the second sub-land portion. In this way, the first inner land portion may include a plurality of sub-lands as long as it has the functions described in the above embodiment, i.e., the function of opening and closing between the rod side passage and the first pump passage and the function of blocking between the first pump passage and the third pilot chamber. Similarly, each of the first intermediate land portion and the first outer land portion may include a plurality of sub-lands as long as it has the functions of each of the land portions described in the above embodiment.

[0088] In the above embodiment, the second spool 60 is configured to include three land portions 61, 63, and 65, but the second spool 60 may include four or more land portions. For example, the second intermediate land portion 63 may be configured to include a third sub land portion and a fourth sub land portion that are axially connected to each other by a small diameter portion. In this case, the third sub land portion may open and close between the head side passage 29 and the second pump passage 25b, and the fourth sub land portion may open and close between the head side passage 29 and the second tank passage 27b. The annular space around the small diameter portion connecting the third sub land portion and the fourth sub land portion may be in communication with the head side passage 29 when the second spool 60 is at least in the second neutral position. In this way, the second intermediate land portion may include multiple sub land portions as long as it has the function described in the above embodiment, that is, the function of opening and closing between the head side passage and the second pump passage and the function of opening and closing between the head side passage and the second tank passage. Similarly, each of the second inner land portion and the second outer land portion may include a plurality of sub-lands as long as the land portion has the function of each of the land portions described in the above embodiment.

[0089] The first spool 50 may include only two land portions. For example, the first spool may include a first pump side land portion that opens and closes between the rod side passage and the first pump passage, a first tank side land portion that opens and closes between the rod side passage and the first tank passage, and a first small diameter portion that connects the first pump side land portion and the first tank side land portion. In this case, when the first spool is in a first neutral position that blocks the rod side passage from both the first pump passage and the first tank passage, the end of the first tank passage may be closed by the outer circumferential surface of the first tank side land portion.

[0090] As long as the first spool and the second spool have the functions of each spool, the land portion of each spool may have a groove on the outer circumferential surface of the land portion. For example, the groove on the outer circumferential surface of the land portion may extend in the circumferential direction or in the axial direction. For example, in the above embodiment, the first inner land portion 51 has the first leak groove 51b on the outer circumferential surface, but the first inner land portion 51 may have a groove other than the first leak groove 51b on the outer circumferential surface. Also, in the above embodiment, the second inner land portion 61 has the second leak groove 61a on the outer circumferential surface, but the second inner land portion 61 may have a groove other than the second leak groove 61a on the outer circumferential surface.

[0091] The second outer land portion 65 has an air vent passage 65a, but instead of the second outer land portion 65 having the air vent passage 65a, or in addition to the second outer land portion 65 having the air vent passage 65a, the first outer land portion 55 may have an air vent passage.

[0092] In the above embodiment, the second intermediate land portion 63 may not have the multiple fourth notches 63b for communicating the head-side passage 29 and the second tank passage 27b. In addition, the shape and number of each of the first notches 51a, the second notches 53a, the third notches 63a, and the fourth notches 63b are not limited to the above description and the contents of the drawings. For example, all of the first notches 51a may have the above-mentioned taper, or some of the multiple first notches may not have a taper. It is sufficient that at least one of the multiple first notches has a taper.

[0093] Only one of the first spool 50 and the second spool 60 may have an identification mark, or neither the first spool 50 nor the second spool 60 may have an identification mark. The first identification mark 91 and the second identification mark 92 do not need to include information for identifying the spring.

[0094] Contrary to the above embodiment, when the first spool 50 and the second spool 60 move toward each other, the rod side passage 28 and the head side passage 29 may be connected to the supply passage 25 and the discharge passage 27, respectively, and when the first spool 50 and the second spool 60 move away from each other, the head side passage 29 and the rod side passage 28 may be connected to the supply passage 25 and the discharge passage 27, respectively.

[0095] In the above embodiment, the first pump passage 25a, the rod side passage 28, and the first tank passage 27a are connected to the spool hole 23A in this order in the direction from the third pilot chamber P3 to the first pilot chamber P1, but the connection point between the first pump passage 25a and the spool hole 23A and the connection point between the first tank passage 27a and the spool hole 23A may be reversed. Also, in the above embodiment, the second pump passage 25b, the head side passage 29, and the second tank passage 27b are connected to the spool hole 23A in this order in the direction from the third pilot chamber P3 to the second pilot chamber P2, but the connection point between the second pump passage 25b and the spool hole 23A and the connection point between the second tank passage 27b and the spool hole 23A may be reversed.

[0096] [Disclosure form] Each of the following aspects is a disclosure of a preferred embodiment.

[0097] [Aspect 1] A valve device for a construction machine that controls the flow of hydraulic oil supplied to and discharged from a plurality of hydraulic actuators including a boom cylinder, a first spool and a second spool spaced axially from each other; a housing having a plurality of spool holes including a boom cylinder spool hole into which the first spool and the second spool are inserted, a first pump passage, a second pump passage, a first tank passage and a second tank passage connected to the boom cylinder spool holes, a rod side passage connected to the boom cylinder spool hole and connected to a rod side chamber of the boom cylinder, a head side passage connected to the boom cylinder spool hole and connected to a head side chamber of the boom cylinder, and a first pilot chamber and a second pilot chamber located on both sides of the boom cylinder spool hole, a portion between the first spool and the second spool in the boom cylinder spool hole constitutes a third pilot chamber, each of the first tank passage and the second tank passage intersects with the plurality of spool holes; the first spool moves between a first neutral position in which the rod side passage is blocked from both the first pump passage and the first tank passage and a first boom drive position in which the rod side passage is communicated with either the first pump passage or the first tank passage in response to a pressure difference between the first pilot chamber and the third pilot chamber, the second spool moves between a second neutral position in which the head side passage is blocked from both the second pump passage and the second tank passage and a second boom drive position in which the head side passage is communicated with either the second pump passage or the second tank passage in response to a pressure difference between the second pilot chamber and the third pilot chamber, Each of the first spool and the second spool includes three or more land portions spaced apart in the axial direction and two or more small diameter portions connecting adjacent ones of the land portions, an annular space around one of the two or more small diameter portions of the first spool communicates with the first tank passage when the first spool is in at least the first neutral position; a valve device, wherein an annular space around one of the two or more smaller diameter portions of the second spool communicates with the second tank passage when the second spool is in at least the second neutral position.

[0098] According to the above configuration, when the first spool is in the first neutral position, the annular space around the small diameter portion of the first spool communicates with the first tank passage, and when the second spool is in the second neutral position, the annular space around the small diameter portion of the second spool communicates with the second tank passage. This makes it possible to ensure a sufficient flow passage cross-sectional area at the intersection of the first tank passage and the second tank passage with the boom cylinder spool hole, thereby reducing the pressure loss of the hydraulic oil flowing through the first tank passage and the second tank passage. This improves the stability of the flow of the hydraulic oil.

[0099] [Aspect 2] The three or more lands of the first spool are a first inner land portion that opens and closes between the rod side passage and the first pump passage; a first intermediate land portion that opens and closes between the rod side passage and the first tank passage; a first outer land portion that blocks the first tank passage from a first pilot chamber, The two or more small diameter portions of the first spool include a first inner small diameter portion connecting the first inner land portion and the first intermediate land portion; a first outer small diameter portion connecting the first outer land portion and the first intermediate land portion, The three or more lands of the second spool are a second inner land portion isolating the second pump passage from a third pilot chamber; and a second intermediate land portion that opens and closes between the head side passage and the second pump passage and also opens and closes between the head side passage and the second tank passage; a second outer land portion that blocks the second tank passage from a second pilot chamber, The two or more small diameter portions of the second spool include a second inner small diameter portion connecting the second inner land portion and the second intermediate land portion; 2. The valve apparatus of claim 1, further comprising a second outer reduced diameter portion connecting the second outer land portion and the second intermediate land portion.

[0100] When the second spool is moved to lower the boom and hydraulic oil flows from the head-side passage to the second tank passage, the flow rate of hydraulic oil from the head-side passage to the second tank passage is large. According to the above configuration, when the second spool is in the second neutral position, the head-side passage is blocked by the second intermediate land portion. Therefore, when hydraulic oil flows from the head-side passage to the second tank passage, the pressure of the head-side passage is received by the outer peripheral surface of the second intermediate land portion, and the pressure in the annular space around the second outer small diameter portion is kept low. Therefore, the second spool can be less susceptible to fluid force from the hydraulic oil when the boom is lowered.

[0101] [Aspect 3] when the first spool is in at least the first neutral position, the first inner land portion blocks communication between the rod side passage and the first pump passage, and the first intermediate land portion blocks communication between the rod side passage and the first tank passage, 3. The valve device of claim 2, wherein when the second spool is in at least the second neutral position, the second intermediate land portion blocks communication between the head side passage and the second pump passage and blocks communication between the head side passage and the second tank passage.

[0102] According to the above configuration, when the first spool is in the first neutral position and the second spool is in the second neutral position, hydraulic oil is not supplied to or discharged from the boom cylinder, so the boom can be stopped.

[0103] [Aspect 4] the first inner land portion has a plurality of first notches arranged at intervals in a circumferential direction at an end portion of an outer circumferential surface of the first inner land portion on the side of the first inner small diameter portion, for communicating the rod side passage and the first pump passage, the first intermediate land portion has a plurality of second notches arranged at intervals in a circumferential direction at an end portion of an outer circumferential surface of the first intermediate land portion on the side of the first inner small diameter portion, for communicating between the rod side passage and the first tank passage, The valve device of claim 2 or 3, wherein the second intermediate land portion has a plurality of third notches arranged at intervals in the circumferential direction at an end portion of the outer circumferential surface of the second intermediate land portion on the second inner small diameter portion side for communicating between the head side passage and the second pump passage.

[0104] According to the above configuration, it is possible to improve controllability of the flow rate of each flow of hydraulic oil, that is, the flow of hydraulic oil from the first pump passage to the rod side passage, the flow of hydraulic oil from the rod side passage to the first tank passage, and the flow of hydraulic oil from the second pump passage to the head side passage.

[0105] [Aspect 5] the second intermediate land portion has a plurality of fourth notches arranged at intervals in a circumferential direction at an end portion of an outer circumferential surface of the second intermediate land portion on the second outer small diameter portion side for communicating between the head side passage and the second tank passage, 5. The valve apparatus of claim 4, wherein a number of the plurality of fourth notches is greater than a number of the plurality of third notches.

[0106] According to this configuration, the flow rate of hydraulic oil sent from the head side chamber to the tank through the multiple fourth notches when the boom is lowered can be increased.

[0107] [Aspect 6] A valve device as described in aspect 4 or 5, wherein at least one of the plurality of first notches has a taper that reduces in depth as it moves away from an end face of the first inner land portion to which the first inner small diameter portion is connected.

[0108] According to the above configuration, it is possible to prevent the amount of change in the opening area relative to the stroke of the first spool when the boom is lowered from becoming large, thereby preventing a large amount of hydraulic oil from flowing into the rod side chamber when the boom is lowered.

[0109] [Aspect 7] A valve device as described in any of aspects 2 to 6, wherein the second outer land portion has an air vent passage that blocks the second tank passage from the second pilot chamber when the second spool is in the second neutral position, and that connects the second pilot chamber and the second tank passage when the second spool moves a predetermined distance or more from the second neutral position in a direction away from the second pilot chamber.

[0110] According to the above configuration, for example, if the valve device is disposed such that the second spool is positioned above the first spool over time, air will accumulate over time in the second pilot chamber located above the boom cylinder spool hole. In such a case, the movement of the second spool allows the air accumulated in the second pilot chamber to escape to the external second tank passage via the air vent passage.

[0111] [Aspect 8] the first spool has a first leak passage extending from a portion of an outer circumferential surface of the first inner land portion that is located closer to the third pilot chamber than a connection point between the boom cylinder spool hole and the first pump passage, to the first outer small diameter portion, A valve device described in any one of aspects 2 to 7, wherein the second spool has a second leak passage extending from a portion on the outer peripheral surface of the second inner land portion that is located on the third pilot chamber side of the connection point between the boom cylinder spool hole and the second pump passage, to the second outer small diameter portion.

[0112] According to the above configuration, hydraulic oil that leaks from the first pump passage side between the outer peripheral surface of the first inner land portion and the inner peripheral surface of the spool hole for the boom cylinder can be discharged to the first tank passage through the first leak passage, and hydraulic oil that leaks from the second pump passage side between the outer peripheral surface of the second inner land portion and the inner peripheral surface of the spool hole for the boom cylinder can be discharged to the second tank passage through the second leak passage.

[0113] [Aspect 9] The first inner land portion has a first leak groove on an outer peripheral surface thereof, the first leak passage includes a first inlet port disposed in the first leak groove and a first outlet port disposed in the first outer small diameter portion; The second inner land portion has a second leak groove on an outer peripheral surface thereof, 9. The valve device of claim 8, wherein the second leak passage includes a second inlet port disposed in the second leak groove and a second outlet port disposed in the second outer reduced diameter portion.

[0114] [Aspect 10] A valve device described in any one of aspects 2 to 9, wherein at least one of the first spool and the second spool has an identification mark on an outer surface of the small diameter portion of the at least one spool for identifying the at least one spool.

[0115] According to the above-mentioned configuration, at least one of the first spool and the second spool can be identified by the identification mark. In addition, since the identification mark is disposed on the small diameter portion that is not in contact with the housing, deterioration of the identification mark can be suppressed.

[0116] [Aspect 11] A valve device according to any one of aspects 2 to 10, wherein a diameter of the first outer small diameter portion is greater than a diameter of the first inner small diameter portion.

[0117] According to the above configuration, by increasing the diameter of the first outer small diameter portion, when hydraulic oil flows from the rod side passage to the first tank passage, the end face of the first intermediate land portion opposite the first outer small diameter portion can support the hydraulic pressure that it receives in the axial direction.

[0118] [Aspect 12] A valve device for a construction machine that controls the flow of hydraulic oil supplied to and discharged from a plurality of hydraulic actuators including a boom cylinder, a first spool and a second spool spaced axially from each other; a housing having a plurality of spool holes including a boom cylinder spool hole into which the first spool and the second spool are inserted, a first pump passage, a second pump passage, a first tank passage and a second tank passage connected to the boom cylinder spool holes, a rod side passage connected to the boom cylinder spool hole and connected to a rod side chamber of the boom cylinder, a head side passage connected to the boom cylinder spool hole and connected to a head side chamber of the boom cylinder, and a first pilot chamber and a second pilot chamber located on both sides of the boom cylinder spool hole, a portion between the first spool and the second spool in the boom cylinder spool hole constitutes a third pilot chamber, The first spool is a first pump side land portion that opens and closes between the rod side passage and the first pump passage; a first tank side land portion that opens and closes between the rod side passage and the first tank passage; a first small diameter portion connecting the first pump side land portion and the first tank side land portion, The second spool is a second inner land portion isolating the second pump passage from a third pilot chamber; and a second intermediate land portion that opens and closes between the head side passage and the second pump passage and also opens and closes between the head side passage and the second tank passage; a second outer land portion that blocks the second tank passage from a second pilot chamber; a second inner small diameter portion connecting the second inner land portion and the second intermediate land portion; a second outer small diameter portion connecting the second outer land portion and the second intermediate land portion, the first pump side land portion has a plurality of first notches arranged at intervals in a circumferential direction at an end portion of an outer circumferential surface of the first pump side land portion on the side of the first small diameter portion for communicating between the rod side passage and the first pump passage, At least one of the plurality of first notches has a taper that decreases in depth as it moves away from an end face of the first pump side land portion to which the first small diameter portion is connected.

[0119] According to the above configuration, it is possible to prevent the amount of change in the opening area relative to the stroke of the first spool when the boom is lowered from becoming large. This makes it possible to suppress a large amount of hydraulic oil from flowing into the rod side chamber when the boom is lowered. This makes it possible to improve the stability of the hydraulic oil flow. [Explanation of symbols]

[0120] 5A: Boom cylinder 5a: Rod side chamber 5b: Head chamber 10: Valve gear 11: Housing 12: Spool 12A: Boom cylinder spool 23: Spool hole 23A: Spool hole for boom cylinder 25a: First pump passage 25b: Second pump passage 27a: First tank passage 27b: Second tank passage 28: Rod side passage 29: Head side passage 50: First spool 51: First inner land part 51a: 1st notch 51b: First leak groove 52: 1st inner small diameter part 53: First intermediate land section 53a: 2nd notch 54: 1st outer small diameter part 55: First outer land part 60: Second spool 61: Second inner land part 61a: Second leak groove 62: 2nd inner small diameter part 63: Second intermediate land section 63a: 3rd notch 63b: 4th notch 64: 2nd outer small diameter part 65: Second outer land 65a: Air vent passage 81: First leak passage 81a: First inlet port 81b: First exit port 82: Second leak passage 82a: Second inlet port 82b: 2nd exit port 91: First identification mark 92: Second identification mark P1: First pilot room P2: Second pilot room P3: 3rd pilot room

Claims

1. A valve device for a construction machine that controls the flow of hydraulic oil supplied to and discharged from a plurality of hydraulic actuators including a boom cylinder, a first spool and a second spool spaced axially from each other; a housing having a plurality of spool holes including a boom cylinder spool hole into which the first spool and the second spool are inserted, a first pump passage, a second pump passage, a first tank passage and a second tank passage connected to the boom cylinder spool holes, a rod side passage connected to the boom cylinder spool hole and connected to a rod side chamber of the boom cylinder, a head side passage connected to the boom cylinder spool hole and connected to a head side chamber of the boom cylinder, and a first pilot chamber and a second pilot chamber located on both sides of the boom cylinder spool hole, a portion of the boom cylinder spool hole between the first spool and the second spool constitutes a third pilot chamber, each of the first tank passage and the second tank passage intersects with the plurality of spool holes; the first spool moves between a first neutral position in which the rod side passage is blocked from both the first pump passage and the first tank passage and a first boom drive position in which the rod side passage is communicated with either the first pump passage or the first tank passage in response to a pressure difference between the first pilot chamber and the third pilot chamber, the second spool moves between a second neutral position in which the head side passage is blocked from both the second pump passage and the second tank passage and a second boom drive position in which the head side passage is communicated with either the second pump passage or the second tank passage in response to a pressure difference between the second pilot chamber and the third pilot chamber, Each of the first spool and the second spool includes three or more land portions spaced apart in the axial direction and two or more small diameter portions connecting adjacent ones of the land portions, an annular space around one of the two or more small diameter portions of the first spool communicates with the first tank passage when the first spool is in at least the first neutral position; a valve assembly, wherein an annular space around one of the two or more smaller diameter portions of the second spool communicates with the second tank passage when the second spool is in at least the second neutral position.

2. The three or more lands of the first spool include a first inner land portion that opens and closes between the rod side passage and the first pump passage; a first intermediate land portion that opens and closes between the rod side passage and the first tank passage; a first outer land portion that blocks the first tank passage from a first pilot chamber, The two or more small diameter portions of the first spool include a first inner small diameter portion connecting the first inner land portion and the first intermediate land portion; a first outer small diameter portion connecting the first outer land portion and the first intermediate land portion, The three or more lands of the second spool include: a second inner land portion isolating the second pump passage from a third pilot chamber; a second intermediate land portion that opens and closes between the head side passage and the second pump passage and also opens and closes between the head side passage and the second tank passage; a second outer land portion that blocks the second tank passage from a second pilot chamber, The two or more small diameter portions of the second spool include a second inner small diameter portion connecting the second inner land portion and the second intermediate land portion; 2. The valve assembly of claim 1, further comprising a second outer reduced diameter portion connecting said second outer land portion and said second intermediate land portion.

3. when the first spool is in at least the first neutral position, the first inner land portion blocks communication between the rod side passage and the first pump passage, and the first intermediate land portion blocks communication between the rod side passage and the first tank passage, 3. The valve device according to claim 2, wherein, when the second spool is in at least the second neutral position, the second intermediate land portion blocks communication between the head side passage and the second pump passage and blocks communication between the head side passage and the second tank passage.

4. the first inner land portion has a plurality of first notches arranged at intervals in a circumferential direction at an end portion of an outer circumferential surface of the first inner land portion on the side of the first inner small diameter portion, for communicating between the rod side passage and the first pump passage, the first intermediate land portion has a plurality of second notches arranged at intervals in a circumferential direction at an end portion of an outer circumferential surface of the first intermediate land portion on the side of the first inner small diameter portion, for communicating between the rod side passage and the first tank passage, 4. The valve device according to claim 2, wherein the second intermediate land portion has a plurality of third notches arranged at intervals in the circumferential direction at an end portion of an outer circumferential surface of the second intermediate land portion on the second inner small diameter portion side, for communicating between the head side passage and the second pump passage.

5. the second intermediate land portion has a plurality of fourth notches arranged at intervals in a circumferential direction at an end portion of an outer circumferential surface of the second intermediate land portion on the second outer small diameter portion side, for communicating between the head side passage and the second tank passage, The valve arrangement of claim 4 , wherein the number of said plurality of fourth notches is greater than the number of said plurality of third notches.

6. 5. The valve device of claim 4, wherein at least one of the plurality of first notches has a taper that decreases in depth with increasing distance from an end face of the first inner land portion to which the first inner reduced diameter portion is connected.

7. 4. The valve device according to claim 2 or 3, wherein the second outer land portion has an air vent passage that blocks the second tank passage from the second pilot chamber when the second spool is in the second neutral position, and that connects the second pilot chamber and the second tank passage when the second spool moves a predetermined distance or more from the second neutral position in a direction away from the second pilot chamber.

8. the first spool has a first leak passage extending from a portion of an outer circumferential surface of the first inner land portion that is located closer to the third pilot chamber than a connection point between the boom cylinder spool hole and the first pump passage, to the first outer small diameter portion, 4. The valve device according to claim 2, wherein the second spool has a second leak passage extending from a portion on an outer circumferential surface of the second inner land portion that is located closer to the third pilot chamber than a connection point between the boom cylinder spool hole and the second pump passage, to the second outer small diameter portion.

9. The first inner land portion has a first leak groove on an outer peripheral surface thereof, the first leak passage includes a first inlet port disposed in the first leak groove and a first outlet port disposed in the first outer small diameter portion; The second inner land portion has a second leak groove on an outer peripheral surface thereof, 9. The valve arrangement of claim 8, wherein the second leak passage includes a second inlet port disposed in the second leak groove and a second outlet port disposed in the second outer reduced diameter portion.

10. 4. The valve device according to claim 2, wherein at least one of the first spool and the second spool has an identification mark for identifying the at least one spool on an outer circumferential surface of the small diameter portion of the at least one spool.

11. 4. The valve device according to claim 2 or 3, wherein a diameter of the first outer small diameter portion is greater than a diameter of the first inner small diameter portion.

12. A valve device for a construction machine that controls the flow of hydraulic oil supplied to and discharged from a plurality of hydraulic actuators including a boom cylinder, a first spool and a second spool spaced axially from each other; a housing having a plurality of spool holes including a boom cylinder spool hole into which the first spool and the second spool are inserted, a first pump passage, a second pump passage, a first tank passage and a second tank passage connected to the boom cylinder spool holes, a rod side passage connected to the boom cylinder spool hole and connected to a rod side chamber of the boom cylinder, a head side passage connected to the boom cylinder spool hole and connected to a head side chamber of the boom cylinder, and a first pilot chamber and a second pilot chamber located on both sides of the boom cylinder spool hole, a portion of the boom cylinder spool hole between the first spool and the second spool constitutes a third pilot chamber, The first spool is a first pump side land portion that opens and closes between the rod side passage and the first pump passage; a first tank side land portion that opens and closes between the rod side passage and the first tank passage; a first small diameter portion connecting the first pump side land portion and the first tank side land portion, The second spool is a second inner land portion isolating the second pump passage from a third pilot chamber; a second intermediate land portion that opens and closes between the head side passage and the second pump passage and also opens and closes between the head side passage and the second tank passage; a second outer land portion that blocks the second tank passage from a second pilot chamber; a second inner small diameter portion connecting the second inner land portion and the second intermediate land portion; a second outer small diameter portion connecting the second outer land portion and the second intermediate land portion, the first pump side land portion has a plurality of first notches arranged at intervals in a circumferential direction at an end portion of an outer circumferential surface of the first pump side land portion on a side of the first small diameter portion for communicating between the rod side passage and the first pump passage, At least one of the plurality of first notches has a taper that decreases in depth as it moves away from an end face of the first pump side land portion to which the first small diameter portion is connected.

Images