Flow Control Valve

Abstract

A feedback throttle (54) increases an opening amount between a feedback flow path (49) and a back pressure chamber (47) as a main valve (43) is displaced in a direction away from a main valve seat (46). The feedback throttle (54) has a boundary part K that divides the section where the opening amount of the feedback diaphragm (54) changes, so that the rate of change of the opening amount of the feedback throttle (54) changes so as to be smaller with respect to the displacement of the main valve (43) toward the main valve seat (46). The boundary part K is located in the displacement area of the main valve (43) corresponding to the position where the opening part of a main valve throttle (53) is blocked, in relation to the displacement of the main valve (43) toward the main valve seat (46).

Description

[Technical field]

[0001] The present disclosure relates to a flow control valve that is provided in a hydraulic circuit of, for example, a construction machine and controls the flow rate of hydraulic oil supplied from a hydraulic pump to an actuator. [Background technology]

[0002] Hydraulic circuits of construction machines such as hydraulic excavators, hydraulic cranes, and wheel loaders are provided with sheet valve-type flow control valves having a flow control function. For example, Patent Document 1 describes a spool valve equipped with a check valve (main valve). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-017273 A (Patent No. 4463028 A) Summary of the Invention

[0004] Incidentally, FIG. 24 shows a flow control valve 101 according to a comparative example. The flow control valve 101 according to this comparative example is incorporated into a control valve device 21 as shown in FIG. 2 described later, for example. The control valve device 21 shown in FIG. 2 described later incorporates a flow control valve 33 (main valve 43) according to the first embodiment. Here, a comparative example will be described in which a flow control valve 101 (main valve 102) according to a comparative example in FIG. 24 is incorporated into the control valve device 21 in FIG. 2, instead of the flow control valve 33 (main valve 43) according to the first embodiment in FIG. 2. The flow control valve 101 according to the comparative example controls the displacement amount of the main valve 102 so that the opening amount of the feedback throttle 103 provided in the main valve 102 corresponds to the opening amount of the pilot throttle 56 (see FIG. 2) by variably controlling the opening amount of the pilot throttle 56 (see FIG. 2) provided in the pilot valve 55 (see FIG. 2). This allows the opening amount of the main valve throttle 104 provided in the main valve 102 to be variably controlled, and the flow rate from the inlet side flow passage 105 to the outlet side flow passage 106 to be controlled to a desired value.

[0005] For example, when the pilot valve 55 (see FIG. 2) changes so that the opening of the pilot throttle 56 (see FIG. 2) becomes smaller, the pressure (back pressure) in the back pressure chamber 107 of the main valve 102 approaches the pressure in the inlet-side flow path 105. Therefore, the increase in back pressure applies a force in the valve closing direction to the main valve 102, and the main valve 102 is displaced in the valve closing direction. On the other hand, as the main valve 102 is displaced in the valve closing direction, the opening of the feedback throttle 103 decreases, so the pressure (back pressure) in the back pressure chamber 107 approaches the pressure in the outlet-side flow path 106, and the decrease in back pressure applies a force in the valve opening direction to the main valve 102. As a result of this position feedback action, the main valve 102 stops at a position where the "valve opening force due to the pressures in the inlet-side flow path 105 and the outlet-side flow path 106" and the "valve closing force due to the back pressure and spring 108" are balanced.

[0006] FIG. 25 is a characteristic diagram showing an example of the relationship between the "displacement of the pilot valve 55" and the "opening of the feedback orifice 103, the opening of the pilot orifice 56, the displacement of the main valve 102, and the opening of the main valve orifice 104." As shown in FIG. 25, when the displacement of the pilot valve 55 changes from "0" to "displacement A," the opening of the pilot orifice 56 decreases, and accordingly, the displacement of the main valve 102 and the opening of the main valve orifice 104 also decrease, and the opening of the main valve orifice 104 reaches "0." Next, when the displacement of the pilot valve 55 changes from "displacement A" to "displacement B," the opening of the pilot orifice 56 decreases further, and accordingly, the displacement of the main valve 102 also decreases and reaches "0." FIG. 24 shows the state of the main valve 102 when the displacement of the pilot valve 55 is "displacement B."

[0007] Here, when a configuration is adopted in which the flow rate from the inlet side flow passage 105 to the outlet side flow passage 106 can be controlled to zero, that is, until the inlet side flow passage 105 and the outlet side flow passage 106 are blocked by the main valve 102 (the opening amount of the main valve throttle 104 becomes zero), two problems arise. These points will be explained below.

[0008] First, the first problem is that the proportional control range of the opening amount of the pilot orifice 56 includes a range (between "displacement A" and "displacement B" in FIG. 25) in which the opening amount of the main valve orifice 104 cannot be proportionally controlled. This range cannot be utilized to expand the proportional control range of the opening amount of the main valve orifice 104 to improve the proportional control. That is, the main valve 102 is provided with a seat portion 102A and a cylindrical portion 102B, and a tool relief groove 102C is provided between them. This is a necessary part in manufacturing to ensure the dimensional accuracy and surface roughness of the seat portion 102A and the cylindrical portion 102B. However, this range is a useless control range for opening control because the opening 104A of the main valve orifice 104 is blocked even if the displacement of the main valve 102 is proportionally controlled. In response to this, it is possible to increase the maximum displacement in the valve opening direction in order to expand the proportional control range. However, in this case, the parts will become larger and the costs will increase.

[0009] Next, the second problem is that the displacement of the main valve 102 becomes oscillatory due to fluid force near the displacement of the main valve 102 where the opening 104A of the main valve throttle 104 switches between open and closed. That is, as the opening amount of the main valve throttle 104 approaches "0", the direction of the jet passing through the main valve throttle 104 approaches the axial direction of the main valve 102. As a result, as the opening amount of the main valve throttle 104 approaches "0", the fluid force acting in the axial direction of the main valve 102 increases, making it easier to cause oscillatory behavior. In response to this, it is conceivable to increase the size of the main valve 102 and reduce the magnitude of the fluid force relative to the pressure acting on the main valve 102 in order to suppress oscillatory behavior. However, this also leads to an increase in the size of the parts and an increase in costs.

[0010] The object of the present invention is to provide a flow control valve which expands the range over which the opening of the main valve throttle can be proportionally controlled relative to the proportional control range of the pilot throttle opening, and which suppresses the oscillatory behavior of the displacement of the main valve due to fluid forces in the vicinity of the displacement of the main valve where the opening of the main valve throttle is switched between open and closed, thereby achieving highly accurate flow control.

[0011] The present invention relates to a valve device comprising: a housing; a main valve chamber provided in the housing; a main valve slidably provided in the main valve chamber and having a valve portion; a main valve seat provided on one end side of the main valve chamber and communicating or blocking a flow of a working fluid by the valve portion of the main valve being seated and released; an inlet side flow passage that applies pressure to the main valve in a direction away from the main valve seat and introduces working fluid from the outside of the main valve chamber into the main valve chamber; and an inlet side flow passage that, when the main valve is released from the main valve seat, delivers working fluid from the inside of the main valve chamber to the outside of the main valve chamber and presses the main valve from the main valve seat to the outside of the main valve chamber. a back pressure chamber provided on the other end side of the main valve chamber and providing a pressure to the main valve in a direction approaching the main valve seat; a feedback flow passage provided in the main valve and communicating the inlet flow passage with the back pressure chamber; a pilot flow passage provided in the housing and communicating the back pressure chamber with the outlet flow passage; a main valve throttle provided in the main valve and increasing an opening amount between the inlet flow passage and the outlet flow passage as the main valve is displaced in a direction away from the main valve seat; a feedback throttle provided between the inlet side flow passage and the back pressure chamber and configured to increase an opening amount between the feedback flow passage and the back pressure chamber in response to displacement of the main valve in a direction away from the main valve seat, a pilot valve slidably provided in the housing, and a pilot throttle provided in the pilot valve and configured to decrease or increase an opening amount of the pilot flow passage in response to displacement of the pilot valve, the flow control valve having a flow control function for variably controlling a flow rate from the inlet side flow passage to the outlet side flow passage by controlling an amount of displacement of the main valve in accordance with an opening amount of the pilot throttle, the feedback throttle has at least one or more boundary portions which divide a change range of the opening amount of the feedback throttle so that a rate of change of the opening amount of the feedback throttle with respect to displacement of the main valve in a direction approaching the main valve seat changes to a smaller side, and at least one of the boundary portions is present within a displacement region of the main valve corresponding to a position where an opening of the main valve throttle is blocked in response to displacement of the main valve in a direction approaching the main valve seat, or is present in a displacement range closer to the main valve seat of the main valve than this.

[0012] According to the present invention, the range over which the opening of the main valve throttle can be proportionally controlled relative to the proportional control range of the opening of the pilot throttle is expanded, and the oscillatory behavior of the displacement of the main valve due to fluid forces in the vicinity of the displacement of the main valve where the opening of the main valve throttle is switched between open and closed is suppressed, thereby achieving highly accurate flow rate control. [Brief description of the drawings]

[0013] [Figure 1] 1 is an overall configuration diagram showing a case in which a flow control valve according to a first embodiment is applied to a hydraulic circuit of a hydraulic excavator. [Diagram 2] 2 is a vertical cross-sectional view showing a flow control valve and a directional control valve in FIG. 1. [Diagram 3] FIG. 3 is an enlarged longitudinal sectional view showing a portion (III) in FIG. 2. [Figure 4] 4 is a vertical cross-sectional view taken in the same position as FIG. 3 and showing the main valve in a state where it is opened to a boundary portion where the rate of change of the opening amount of the feedback throttle changes. FIG. [Diagram 5] FIG. 4 is a vertical cross-sectional view taken from the same position as FIG. 3, showing the main valve in a maximum open position. [Figure 6] FIG. 2 is a perspective view showing a main valve (valve member). [Figure 7] FIG. 2 is a plan view showing the main valve (valve member). [Figure 8] 8 is a plan view showing the main valve (valve member) in a state rotated 90 degrees in the circumferential direction from the state in FIG. 7. FIG. [Figure 9] 9 is a vertical sectional view of the main valve (valve member) as viewed from the direction of arrows IX-IX in FIG. 7. [Figure 10] 9 is a vertical sectional view of the main valve (valve member) as viewed from the direction of arrow XX in FIG. 8. [Figure 11] 11 is a cross-sectional view of the main valve (valve member) as viewed from the direction of arrows XI-XI in FIG. [Figure 12] FIG. 4 is a characteristic diagram showing an example of the relationship among a pilot valve displacement amount, a feedback throttle opening amount, a pilot throttle opening amount, a main valve displacement amount, and a main valve throttle opening amount according to the first embodiment. [Figure 13] FIG. 4 is a characteristic diagram showing an example of the relationship between a main valve displacement amount, a main valve throttle opening amount, and a feedback throttle opening amount. [Figure 14] FIG. 11 is a perspective view showing a main valve (valve member) according to a second embodiment. [Figure 15] FIG. 11 is a plan view showing a main valve (valve member) according to a second embodiment. [Figure 16] 16 is a vertical sectional view of the main valve (valve member) as viewed in the direction of arrows XVI-XVI in FIG. 15. [Figure 17] FIG. 11 is a cutaway perspective view of a feedback diaphragm according to a second embodiment. [Figure 18] FIG. 2 is a perspective view showing a main valve (valve member) according to a first modified example. [Figure 19] FIG. 4 is a plan view showing a main valve (valve member) according to a first modified example. [Figure 20] 20 is a longitudinal sectional view of the main valve (valve member) as viewed in the direction of arrows XX-XX in FIG. 19. [Figure 21] FIG. 11 is a perspective view showing a main valve (valve member) according to a second modified example. [Figure 22] FIG. 11 is a plan view showing a main valve (valve member) according to a second modified example. [Diagram 23] 23 is a vertical sectional view of the main valve (valve member) as viewed in the direction of arrows XXIII-XXIII in FIG. 22. [Figure 24] FIG. 4 is a vertical cross-sectional view showing a flow control valve according to a comparative example. [Diagram 25] FIG. 11 is a characteristic diagram showing an example of the relationship among a pilot valve displacement amount, a feedback throttle opening amount, a pilot throttle opening amount, a main valve displacement amount, and a main valve throttle opening amount according to a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, a flow control valve according to an embodiment will be described in detail with reference to the accompanying drawings, taking as an example a case where it is applied to a hydraulic circuit of a hydraulic excavator.

[0015] Figures 1 to 13 show a first embodiment. In Figure 1, a hydraulic excavator 1, which is a representative example of a construction machine, is configured to include a self-propelled crawler-type lower traveling body 2, an upper rotating body 3 rotatably mounted on the lower traveling body 2, and a work device 4 of a multi-joint structure that is provided on the front side of the upper rotating body 3 so as to be capable of being raised and lowered and performs excavation work and the like. In this case, the lower traveling body 2 and the upper rotating body 3 form the vehicle body of the hydraulic excavator 1.

[0016] The working device 4, also called a working machine or a front, is configured to include, for example, a boom 5, an arm 6, and a bucket 7 as a working tool. The working device 4 is also configured to include a boom cylinder 8 as a hydraulic actuator (hydraulic actuator) that drives the boom 5, an arm cylinder 9 as a hydraulic actuator that drives the arm 6, and a bucket cylinder 10 (work tool cylinder) as a hydraulic actuator that drives the bucket 7. The working device 4 performs a lifting and lowering operation by extending or retracting the cylinders 8, 9, and 10, which are hydraulic cylinders, based on the supply of pressure oil from a hydraulic pump 11. Note that, in FIG. 1, hydraulic circuits related mainly to the boom cylinder 8 and the arm cylinder 9 are shown to avoid complicating the drawing.

[0017] A main hydraulic pump 11 mounted on the upper rotating body 3 of the hydraulic excavator 1 constitutes a hydraulic source together with a tank 12. The hydraulic pump 11 is rotated by a prime mover (not shown) such as a diesel engine. The hydraulic pump 11 sucks hydraulic oil in the tank 12 and discharges (supplies) the pressurized oil toward a pump line 13 and a center bypass line 14. The pressurized oil discharged to the pump line 13 and the center bypass line 14 is supplied to the boom cylinder 8 via a boom directional control valve 16, and is supplied to the arm cylinder 9 via an arm directional control valve 18. In addition, a tank line 15 is provided between the boom directional control valve 16 and the arm directional control valve 18 and the tank 12, for example, to return oil from the boom cylinder 8 and the arm cylinder 9 to the tank 12 side.

[0018] Here, branch pipelines 13A and 13B are provided in the middle of the pump pipeline 13. One branch pipeline 13A is connected to a high-pressure side port of an arm directional control valve 18 (i.e., an outlet-side flow path 27 shown in FIG. 2, which will be described later) via a flow control valve 33, which will be described later. The other branch pipeline 13B is connected to a high-pressure side port of a boom directional control valve 16, which will be described later. The pump pipeline 13 and the tank pipeline 15 are also connected to the bucket cylinder 10, etc., via another branch pipeline, another directional control valve (neither of which are shown), etc.

[0019] A boom directional control valve 16 (hereinafter referred to as boom control valve 16), which is a directional control valve for the boom cylinder 8, has left and right hydraulic pilot sections 16A and 16B, and is normally held in a neutral position (A). The boom control valve 16 is switched from the neutral position (A) to switching positions (B) and (C) by supplying pilot pressure to the left and right hydraulic pilot sections 16A and 16B from a boom lever operating device (not shown), which is, for example, a hydraulic pilot type operating valve.

[0020] A pair of actuator pipelines 17A, 17B are provided between the boom cylinder 8 and the boom control valve 16. One actuator pipeline 17A connects a bottom side oil chamber (not shown) of the boom cylinder 8 to one pressure oil inlet / outlet port of the boom control valve 16. The other actuator pipeline 17B connects a rod side oil chamber (not shown) of the boom cylinder 8 to the other pressure oil inlet / outlet port of the boom control valve 16.

[0021] The arm directional control valve 18 (hereinafter referred to as the arm control valve 18), which is a directional control valve for the arm cylinder 9, has left and right hydraulic pilot sections 18A and 18B, and is normally held in a neutral position (A). The arm control valve 18 is switched from the neutral position (A) to switching positions (B) and (C) by supplying pilot pressure to the left and right hydraulic pilot sections 18A and 18B from an arm lever operating device (not shown), which is, for example, a hydraulic pilot type operating valve.

[0022] A pair of actuator pipelines 19A, 19B are provided between the arm cylinder 9 and the arm control valve 18. One actuator pipeline 19A connects a bottom side oil chamber (not shown) of the arm cylinder 9 to one pressure oil inflow / outflow port of the arm control valve 18 (i.e., the inflow / outflow passage 28B shown in FIG. 2). The other actuator pipeline 19B connects a rod side oil chamber (not shown) of the arm cylinder 9 to the other pressure oil inflow / outflow port of the arm control valve 18 (i.e., the inflow / outflow passage 28A shown in FIG. 2).

[0023] When the arm control valve 18 is switched from the neutral position (A) to the switching position (B), pressure oil from the hydraulic pump 11 is supplied to the bottom side oil chamber of the arm cylinder 9 via the branch pipe 13A, the flow control valve 33 described below, the arm control valve 18, and the actuator pipe 19A. The pressure oil in the rod side oil chamber is discharged to the tank 12 via the actuator pipe 19B, the arm control valve 18, and the tank pipe 15. As a result, the arm cylinder 9 is extended by the pressure oil supplied to the bottom side oil chamber, and the arm 6 is rotated downward.

[0024] When the arm control valve 18 is switched from the neutral position (A) to the switching position (C), pressure oil from the hydraulic pump 11 is supplied to the rod side oil chamber of the arm cylinder 9 via the branch pipe 13A, the flow control valve 33, the arm control valve 18, and the actuator pipe 19B. The pressure oil in the bottom side oil chamber is discharged to the tank 12 via the actuator pipe 19A, the arm control valve 18, and the tank pipe 15. As a result, the arm cylinder 9 contracts due to the pressure oil supplied to the rod side oil chamber, and rotates the arm 6 upward.

[0025] The relief valve 20 is a variable set pressure type relief valve. The relief valve 20 is provided between the pump line 13 and the center bypass line 14 and the tank line 15. For example, when the pressure in the pump line 13 rises above the set pressure, the relief valve 20 opens and relieves the excess pressure to the tank line 15. The relief valve 20 has a pressure setting spring 20A and a pilot oil chamber 20B, and the set pressure of the pressure setting spring 20A changes according to the pilot pressure supplied from the outside to the pilot oil chamber 20B. As a result, the relief valve 20 is configured such that the relief set pressure can be adjusted in two or more stages between a low pressure setting and a high pressure setting.

[0026] The control valve device 21 includes the arm control valve 18 and a flow control valve 33, which will be described later. As shown in Fig. 2, the control valve device 21 has a housing 22 common to the arm control valve 18 and the flow control valve 33. In this case, the housing 22 includes a main housing 23 that houses the spool 29 of the arm control valve 18 and the main valve 43 of the flow control valve 33, and a pilot housing 36 that houses the main valve 43 and a pilot valve 55 of the flow control valve 33. The main housing 23 and the pilot housing 36 are formed separately as separate parts. Then, a single housing 22 is formed by attaching the pilot housing 36 to the main housing 23.

[0027] Next, a description will be given of the arm control valve 18 of the control valve device 21. Note that Fig. 2 shows the arm control valve 18 in the neutral position (A).

[0028] The arm control valve 18 is a spool valve device that controls the direction of pressure oil supplied from the hydraulic pump 11 to the arm cylinder 9. The arm control valve 18 includes a main housing 23, a spool slide hole 24, an inlet side flow path 25, an outlet side flow path 27, a pair of inflow and outflow passages 28A, 28B, a spool 29, left and right lid bodies 30A, 30B, a stopper 31, and a spring 32. The main housing 23 constitutes the housing 22 of the control valve device 21 together with a pilot housing 36. The main housing 23 is formed with the spool slide hole 24, the inlet side flow path 25, the outlet side flow path 27, and a pair of inflow and outflow passages 28A, 28B.

[0029] The spool sliding hole 24 extends linearly through the main housing 23 in the left-right direction (left-right direction in FIG. 2, the axial direction in which a spool 29 described later slides). First annular oil grooves 24A, 24B, second annular oil grooves 24C, 24D, and third annular oil grooves 24E, 24F are formed on the peripheral wall side of the spool sliding hole 24. The first annular oil grooves 24A, 24B are provided on the axial center side of the spool sliding hole 24, spaced apart from each other in the left-right direction. The second annular oil grooves 24C, 24D are provided on the axial outer side of the spool sliding hole 24 from the first annular oil grooves 24A, 24B, spaced apart from each other in the left-right direction. The third annular oil grooves 24E, 24F are provided at positions axially outward of the spool sliding hole 24 relative to the second annular oil grooves 24C, 24D and spaced apart from each other in the left and right directions.

[0030] The first annular oil grooves 24A, 24B communicate with each other through an outlet-side flow passage 27 formed in an inverted U-shape as a whole. The first annular oil grooves 24A, 24B communicate with and are cut off from the second annular oil grooves 24C, 24D when the spool 29 is displaced left or right from the neutral position shown in FIG. 2. The second annular oil grooves 24C, 24D are constantly in communication with the pair of actuator pipes 19A, 19B through the left and right inflow / outflow passages 28A, 28B. The third annular oil grooves 24E, 24F are constantly in communication with the tank 12 through the tank pipes 15. The third annular oil grooves 24E, 24F communicate with and are cut off from the second annular oil grooves 24C, 24D when the spool 29 is displaced left or right from the neutral position shown in FIG. 2.

[0031] The inlet side flow passage 25 is provided at a position radially spaced from the spool sliding hole 24. In this case, the inlet side flow passage 25 extends along a direction perpendicular to the spool sliding hole 24 (the front-to-back direction in FIG. 2). The inlet side flow passage 25 is connected to the hydraulic pump 11 via the pump pipe 13 (more specifically, the branch pipe 13A). The outlet side flow passage 27 intersects with the inlet side flow passage 25 at the position of the communication hole 26, and extends in an inverted U-shape as a whole. The outlet side flow passage 27 communicates with the first annular oil grooves 24A, 24B provided at a distance from each other.

[0032] The communication hole 26 is disposed at a position facing a valve disc slide hole 34, which will be described later, across the outlet-side flow path 27. The communication hole 26 communicates the inlet-side flow path 25 so as to cross the outlet-side flow path 27. The communication hole 26, together with the valve disc slide hole 34 and a recess 37 of the pilot housing 36, constitutes a main valve chamber 42. A tapered main valve seat 46, which serves as an annular valve seat on which a main valve 43, which will be described later, is seated and separated, is provided at the intersection between the outlet-side flow path 27 and the communication hole 26.

[0033] The pair of inflow / outflow passages 28A, 28B are provided spaced apart from each other in the left and right directions of the main housing 23, sandwiching the outlet-side flow path 27 and the valve body slide hole 34. The pair of inflow / outflow passages 28A, 28B configure pressure oil inflow / outflow ports of the arm control valve 18. That is, the pair of inflow / outflow passages 28A, 28B are connected to the arm cylinder 9 (the rod-side oil chamber and the bottom-side oil chamber) via actuator pipes 19A, 19B.

[0034] The spool 29 is inserted into the spool sliding hole 24 of the main housing 23. The spool 29 slides left and right in the spool sliding hole 24 according to pilot pressures supplied from the outside to the hydraulic pilot sections 18A and 18B. As a result, the arm control valve 18 shown in Fig. 1 switches from the neutral position (A) to the left and right switching positions (B) and (C).

[0035] 2, the spool 29 has switching lands 29A, 29B that selectively connect or disconnect the second annular oil grooves 24C, 24D to or from either the first annular oil grooves 24A, 24B or the third annular oil grooves 24E, 24F. The switching lands 29A, 29B each have a plurality of notches 29A1, 29B1 formed at intervals in the circumferential direction for finely adjusting the flow rate of pressure oil.

[0036] Here, when the spool 29 is slidably displaced to the left in Fig. 2, the switching land 29A of the spool 29 connects the first annular oil groove 24A to the second annular oil groove 24C. At the same time, the switching land 29B of the spool 29 blocks the first annular oil groove 24B from the second annular oil groove 24D and connects the second annular oil groove 24D to the third annular oil groove 24F. As a result, the arm control valve 18 is switched from the neutral position (A) shown in Fig. 1 to the switching position (C) on the right side.

[0037] On the other hand, when the spool 29 is slidably displaced to the right in Fig. 2, the switching land 29B of the spool 29 connects the first annular oil groove 24B to the second annular oil groove 24D. At the same time, the switching land 29A of the spool 29 blocks the first annular oil groove 24A from the second annular oil groove 24C and connects the second annular oil groove 24C to the third annular oil groove 24E. As a result, the arm control valve 18 is switched from the neutral position (A) shown in Fig. 1 to the switching position (B) on the left side.

[0038] The left and right lid bodies 30A, 30B constitute the arm control valve 18 together with the spool 29. The lid bodies 30A, 30B are located on both sides of the spool sliding hole 24 in the axial direction (left and right directions) and are attached to the main housing 23. The lid bodies 30A, 30B close both ends of the spool sliding hole 24. The right lid body 30B is formed longer than the left lid body 30A, and a centering spring 32 is provided inside the right lid body 30B. Hydraulic pilot parts 18A, 18B are provided inside the lid bodies 30A, 30B. Pilot pressure is supplied to the hydraulic pilot parts 18A, 18B from an operating valve (lever operating device). The spool 29 of the arm control valve 18 is slidably displaced left and right in the spool sliding hole 24 in the left and right directions in FIG. 2 according to the pilot pressure at this time.

[0039] The stopper 31 is provided integrally with the spool 29 on the right side of the spool 29. The stopper 31 is displaceably disposed within the cover body 30B, and has a shaft portion 31A extending axially within the cover body 30B. The stopper 31 restricts the stroke end of the spool 29 when the spool 29 is displaced to the right in FIG.

[0040] The spring 32 is a centering spring for holding the spool 29 in a neutral position. The spring 32 is located on the outer circumferential side of the shaft portion 31A of the stopper 31, and is disposed in a state in which an initial load is applied between the end face of the spool 29 and the stopper 31. The spring 32 holds the spool 29 in the neutral position when the pilot pressures from the hydraulic pilot portions 18A, 18B drop to the tank pressure level.

[0041] Next, the flow control valve 33 of the control valve device 21 will be described. Note that Figures 2 and 3 show a state in which the main valve 43 is closed, and Figures 4 and 5 show a state in which the main valve 43 is open. Also, Figure 5 shows a state in which the main valve 43 is fully open, providing a maximum flow rate.

[0042] The flow control valve 33 is a poppet valve device that adjusts the flow rate of pressure oil supplied to the arm cylinder 9. The flow control valve 33 in the first embodiment is a seat valve type flow control valve. The flow control valve 33 includes a housing 22, a main valve chamber 42, a main valve 43, a main valve seat 46, an inlet side flow path 25, an outlet side flow path 27, a back pressure chamber 47, a feedback flow path 49, a pilot flow path 50, a main valve throttle 53, a feedback throttle 54, a pilot valve 55, and a pilot throttle 56.

[0043] The housing 22 is composed of a main housing 23 and a pilot housing 36. That is, the main housing 23, together with the pilot housing 36, constitutes the housing 22 of the flow control valve 33. In addition to the inlet-side flow passage 25, the communication hole 26, and the outlet-side flow passage 27, the main housing 23 is also formed with a valve body slide hole 34 and a branch passage 35.

[0044] The valve disc slide hole 34 is disposed on the opposite side of the inlet-side flow passage 25 with the communication hole 26 and the outlet-side flow passage 27 in between, and is formed as a stepped hole. The valve disc slide hole 34 extends between the pilot housing 36 and the outlet-side flow passage 27 in a direction perpendicular to the spool slide hole 24 (upward and downward in FIG. 2). The valve disc slide hole 34, together with the communication hole 26 and the recess 37 of the pilot housing 36, constitutes a main valve chamber 42. A main valve 43 is displaceably inserted (fitted) into the main valve chamber 42.

[0045] The branch passage 35 is an oil passage branching off from the middle of the outlet-side passage 27. The branch passage 35 is constantly in communication with a second passage 40 on the pilot housing 36 side. The branch passage 35, together with the second passage 40 and a first passage 39, which is another passage provided in the pilot housing 36, constitute a pilot passage 50.

[0046] The pilot housing 36, together with the main housing 23, constitutes the housing 22 of the flow control valve 33. The pilot housing 36 is provided on the outer surface of the main housing 23 so as to close the valve body slide hole 34 of the main housing 23 from the outside. The pilot housing 36 is provided with a recess 37 in which a main valve 43 and a valve spring 48 described later are accommodated, a valve accommodating hole 38 in which a pilot valve 55 described later and the like are accommodated, a first passage 39 communicating between the valve accommodating hole 38 and the recess 37, a second passage 40 extending obliquely between the branch passage 35 of the main housing 23 and the valve accommodating hole 38 and communicated with and blocked from the first passage 39 by the pilot valve 55, and a supply and discharge port 41 for pilot pressure. The supply and discharge port 41 is connected to a pilot chamber 57 described later, which is defined by the inner surface of the valve accommodating hole 38 and the pilot valve 55.

[0047] The main valve chamber 42 is provided in the housing 22. That is, the main valve chamber 42 is formed by the valve body sliding hole 34 and the communication hole 26 of the main housing 23 and the recess 37 of the pilot housing 36, and accommodates the main valve 43 therein. Thus, the main valve chamber 42 is provided across both the main housing 23 and the pilot housing 36.

[0048] The main valve 43 is slidably provided in the main valve chamber 42. The main valve 43 is a valve body of the flow control valve 33, and has a seat portion 44D as a valve portion. In this case, the main valve 43 is configured to include a stepped valve member 44 inserted and fitted into the valve body sliding hole 34, and a valve holding member 45 that is screwed to one axial side of the valve member 44 and holds a check valve 62 (described later) displaceably between the valve member 44. The valve holding member 45 is configured to include a spring receiving portion 45A that supports the valve spring 48 in a compressed state between the recess 37 (the bottom portion of the recess 37) of the pilot housing 36, and a holding tube portion 45B that is formed in a bottomed cylindrical shape and displaceably holds the check valve 62 inside in a state where it is screwed into the valve member 44 (the upper side of the stepped hole portion 44G described later). The check valve 62 and the spring 63 are stored inside the holding tube portion 45B. The valve retaining member 45 is attached to the valve member 44 of the main valve 43 by screwing, with the check valve 62 and the spring 63 housed therein.

[0049] The valve member 44 includes a large diameter portion 44A slidably inserted in the valve body slide hole 34, a small diameter cylindrical portion 44B provided on one axial side of the large diameter portion 44A, a seat portion 44D formed integrally with the other axial side of the large diameter portion 44A via a small diameter reduced diameter portion 44C, the outer periphery of which is seated on and separated from a main valve seat 46 of the main housing 23, and a cylindrical portion 44E protruding in the axial direction from the other side (tip side) of the seat portion 44D toward the inlet side flow path 25. In this case, the seat portion 44D, which is a valve portion, is provided in the main valve 43 (valve member 44). The seat portion 44D comes into contact with (seats on) the main valve seat 46 to block the flow of the working fluid between the inlet side flow path 25 and the outlet side flow path 27.

[0050] The valve member 44 is provided with a stepped hole portion 44G extending from the inner circumferential side of the cylindrical portion 44E toward one axial side (upward) through the reduced diameter portion 44C, the large diameter portion 44A, and the small diameter cylindrical portion 44B, and with a valve seat 44F for the check valve 62 formed at an intermediate portion, a radial hole 44H extending in the radial direction of the stepped hole portion 44G, and a feedback throttle 54 described later. The stepped hole portion 44G communicates with the inlet side flow passage 25 via the inner circumferential side of the cylindrical portion 44E. The radial hole 44H communicates with the back pressure chamber 47 described later through the feedback throttle 54. As a result, the stepped hole portion 44G and the radial hole 44H form a feedback flow passage 49. The cylindrical portion 44E of the valve member 44 is provided with a main valve throttle 53 described later.

[0051] The main valve seat 46 is provided on one end side (the inlet side flow passage 25 side) of the main valve chamber 42. That is, the main valve seat 46 is provided at an intersection of the outlet side flow passage 27 and the communication hole 26 in the main housing 23, and is configured as a tapered annular valve seat. The main valve seat 46 communicates or blocks the working fluid by seating and separating from the seat portion 44D of the main valve 43.

[0052] The inlet-side flow passage 25 is provided in the main housing 23, and is connected to the discharge side of the hydraulic pump 11. The inlet-side flow passage 25 applies pressure to the main valve 43 in a direction away from the main valve seat 46 (valve opening direction) based on pressure oil (working fluid) supplied from the hydraulic pump 11. At the same time, the inlet-side flow passage 25 introduces the working fluid from the outside of the main valve chamber 42 (the hydraulic pump 11 side) to the inside of the main valve chamber 42. The inlet-side flow passage 25 faces the main valve seat 46.

[0053] The outlet side flow passage 27 is provided in the main housing 23 and is connected to the spool sliding hole 24 of the arm control valve 18. When the main valve 43 moves away from the main valve seat 46, the outlet side flow passage 27 guides the working fluid from the inside of the main valve chamber 42 (the communication hole 26 side) to the outside of the main valve chamber 42 (the spool sliding hole 24 side of the arm control valve 18, more specifically, the arm cylinder 9 side). At the same time, the outlet side flow passage 27 applies pressure to the main valve 43 in a direction away from the main valve seat 46 (valve opening direction). The outlet side flow passage 27 also faces the main valve seat 46. The inlet side flow passage 25 and the outlet side flow passage 27 apply pressure to the main valve 43 in the valve opening direction.

[0054] The back pressure chamber 47 is provided on the other end side of the main valve chamber 42 (the side opposite to the inlet side flow path 25). The back pressure chamber 47 applies pressure to the main valve 43 in a direction approaching the main valve seat 46 (valve closing direction). In other words, the back pressure chamber 47 is a control pressure chamber that variably controls the displacement amount (lift amount) of the main valve 43, and is formed between the recess 37 of the pilot housing 36 and the main valve 43. The back pressure chamber 47 is constantly in communication with the first passage 39 of the pilot housing 36.

[0055] The valve spring 48 is provided in the back pressure chamber 47. That is, the valve spring 48 is located in the back pressure chamber 47 and disposed between (the valve retaining member 45 of) the main valve 43 and (the bottom of) the recess 37 of the pilot housing 36. The valve spring 48 is configured using a coil spring or the like, and urges the valve member 44 in the valve closing direction via the valve retaining member 45. That is, the valve spring 48 constantly urges the main valve 43 (valve retaining member 45) in the valve closing direction. The main valve 43 is also pressed in the valve closing direction by the back pressure (control pressure) generated in the back pressure chamber 47.

[0056] The feedback flow passage 49 is provided inside the main valve 43. That is, the feedback flow passage 49 is formed by a stepped hole portion 44G and a radial hole 44H of the main valve 43 (valve member 44). In this case, the radial hole 44H communicates with the back pressure chamber 47 via a feedback throttle 54. As a result, the feedback flow passage 49 communicates between the inlet side flow passage 25 and the back pressure chamber 47.

[0057] The pilot flow passage 50 is provided in the housing 22 (the main housing 23 and the pilot housing 36). That is, the pilot flow passage 50 is composed of the branch passage 35 of the main housing 23 and the first passage 39 and the second passage 40 of the pilot housing 36. As a result, the pilot flow passage 50 communicates between the back pressure chamber 47 and the outlet-side flow passage 27. In this case, the first passage 39 constitutes a pilot throttle upstream pipe 51 which is a pipe on the upstream side of the pilot throttle 56. The second passage 40 and the branch passage 35 constitute a pilot throttle downstream pipe 52 which is a pipe on the downstream side of the pilot throttle 56.

[0058] The main valve throttle 53 is provided on the tip side (the inlet-side flow path 25 side) of the main valve 43 (more specifically, the valve member 44). As described below, the main valve throttle 53 is composed of a side hole 53A and a fixed throttle 53B. The main valve throttle 53 increases the opening between the inlet-side flow path 25 and the outlet-side flow path 27 as the main valve 43 is displaced in a direction away from the main valve seat 46 (displacement toward the upper side in the up-down direction in Figures 2 to 5).

[0059] The feedback throttle 54 is provided between the feedback flow path 49 and the back pressure chamber 47. The feedback throttle 54 is provided as a variable throttle on the outer circumferential surface side of the main valve 43 (the large diameter portion 44A of the valve member 44). The feedback throttle 54 increases the opening amount between the feedback flow path 49 and the back pressure chamber 47 as the main valve 43 is displaced in the direction away from the main valve seat 46 (the valve opening direction).

[0060] As shown in Fig. 2, the pilot valve 55 is slidably provided in the housing 22 (pilot housing 36). That is, the pilot valve 55 is slidably inserted (fitted) in the valve receiving hole 38 of the pilot housing 36. The pilot valve 55 is configured as a spool valve body having a pilot throttle 56. The pilot valve 55 is displaced by introducing working fluid into a pilot chamber 57 and pressurizing it. In addition, as the pilot valve 55 is displaced, the working fluid in a drain chamber 59 described below is discharged from a drain port 59A. The pilot chamber 57 and the drain chamber 59 are provided in the pilot housing 36.

[0061] The pilot throttle 56 is provided in the pilot valve 55. That is, the pilot throttle 56 is provided as a variable throttle on the outer peripheral surface side of the pilot valve 55. The pilot throttle 56 reduces the opening amount of the pilot flow passage 50 in association with the displacement of the pilot valve 55. That is, the pilot throttle 56 reduces the opening amount of the pilot flow passage 50 as the pilot valve 55 moves toward one side in the axial direction (to the right in the left-right direction in FIG. 2) in association with the supply of pressure oil (pilot pressure) to the pilot chamber 57. In this case, the pilot throttle 56 is configured as a notch whose depth increases toward one side in the axial direction (as it moves away from the pilot chamber 57). Note that the pilot throttle 56 may be configured as a notch whose depth is constant, for example.

[0062] The cover 58 is located on one axial side of the valve receiving hole 38 and is attached to the pilot housing 36 by screwing. The cover 58 closes one side of the valve receiving hole 38, thereby defining a drain chamber (spring chamber) 59 on one side of the pilot valve 55. A spring 60 is provided in a compressed state between the cover 58 and the pilot valve 55. The spring 60 biases the pilot valve 55 in the valve opening direction via a washer 61. That is, the drain chamber 59 is provided with the washer 61 that contacts the pilot valve 55 and the spring 60 that biases the pilot valve 55 in the valve opening direction via the washer 61. The cover 58 that is screwed to the pilot housing 36 is configured to bias the spring 60.

[0063] 1 by the spring 60, the pilot valve 55 communicates between the first and second passages 39, 40, which are the pilot flow passage 50, via the pilot throttle 56. At this time, the back pressure chamber 47 of the main valve 43 communicates with the outlet-side flow passage 27 via the first and second passages 39, 40 and the branch passage 35 on the main housing 23 side, and is maintained at a pressure equal to that of the outlet-side flow passage 27. As a result, the main valve 43 is opened to the fully open position.

[0064] On the other hand, when pilot pressure as an external command pressure supplied to the pilot chamber 57 from a remote control valve (not shown) for external command via the supply / discharge port 41 rises to a predetermined pressure value or more, the pilot valve 55 slides against the spring 60 to block the first and second passages 39, 40. As a result, the pilot valve 55 switches from the communication position (a) shown in FIG. 1 to the blocking position (b) against the spring 60. At this time, the back pressure chamber 47 of the main valve 43 is communicated with the second passage 40 (the outlet-side flow path 27) with a minimum opening amount. As a result, the main valve 43 is in the minimum opening position.

[0065] The check valve 62 is provided in the feedback flow passage 49. That is, the check valve 62 is accommodated between the valve member 44 and the valve holding member 45. The check valve 62 is slidably inserted into the holding cylindrical portion 45B of the valve holding member 45, and is normally biased by a spring 63 so as to seat on the valve seat 44F of the valve member 44. That is, the spring 63 for the check valve biases the check valve 62 in a valve closing direction. The check valve 62 allows the working fluid to flow from the inlet side flow passage 25 to the back pressure chamber 47, and prevents (blocks) the reverse flow. That is, when pressure in the inlet side flow passage 25 acts from the cylindrical portion 44E side of the valve member 44, the check valve 62 opens so as to move away from the valve seat 44F against the spring 63.

[0066] As a result, the pressure oil in the inlet-side flow passage 25 is supplied to the back pressure chamber 47 via the stepped hole portion 44G and radial hole 44H of the valve member 44, and the feedback orifice 54. In this way, the check valve 62 allows the pressure oil to flow from the inlet-side flow passage 25 toward the back pressure chamber 47 inside the main valve 43, and prevents a reverse flow. That is, the check valve 62 prevents the oil in the back pressure chamber 47 from flowing toward the stepped hole portion 44G and the inlet-side flow passage 25 via the radial hole 44H of the valve member 44, etc. The check valve 62, together with the seat portion 44D of the main valve 43, blocks a reverse flow from the outlet-side flow passage 27 to the inlet-side flow passage 25.

[0067] The flow control valve 33 thus configured has a flow control function and a load check function. That is, the flow control valve 33 has a flow control function of variably controlling the flow rate (flow rate of pressure oil flowing through the arm control valve 18) from the inlet-side flow passage 25 to the outlet-side flow passage 27 by controlling the displacement amount (lift amount, i.e., opening area) of the main valve 43 according to the opening amount of the pilot throttle 56. In addition, the flow control valve 33 has a load check function of blocking the flow of the working fluid (oil liquid) from the outlet-side flow passage 27 to the inlet-side flow passage 25 by the main valve 43 and the check valve 62 when the pressure of the inlet-side flow passage 25 is lower than the pressure of the outlet-side flow passage 27.

[0068] Next, the cylindrical portion 44E of the main valve 43 will be described.

[0069] That is, the main valve 43 is provided with a cylindrical portion 44E located on the inlet-side flow path 25 side, which is the tip side. In other words, the valve member 44 of the main valve 43 has the cylindrical portion 44E on the tip side. The cylindrical portion 44E is provided with a main valve throttle 53. In addition, a tool clearance groove 44J is provided on the base end side (seat portion 44D side) of the cylindrical portion 44E. That is, the tool clearance groove 44J is provided at the connection portion between the cylindrical portion 44E and the seat portion 44D, in other words, between the seat portion 44D and the cylindrical portion 44E. The tool clearance groove 44J functions as a clearance groove for a machining tool required to ensure the dimensional accuracy and surface roughness of the seat portion 44D and the cylindrical portion 44E.

[0070] The main valve throttle 53 adjusts the flow rate (the opening area of ​​the communication hole 26 with respect to the outlet side passage 27) of pressure oil flowing from the inlet side passage 25 to the outlet side passage 27 via the communication hole 26 in accordance with axial displacement (upward and downward displacement in Figs. 2 to 5) of the main valve 43. The main valve throttle 53 is composed of a plurality of (e.g., eight) side holes 53A and a plurality of (e.g., four) fixed throttles 53B.

[0071] The lateral hole 53A is provided in the cylindrical portion 44E of the main valve 43. The lateral hole 53A extends in the radial direction of the main valve 43 (in a direction perpendicular to the central axis of the main valve 43). That is, the lateral hole 53A is formed in the cylindrical portion 44E as a through hole penetrating between the outer circumferential side and the inner circumferential side of the cylindrical portion 44E. The fixed throttle 53B is provided in the cylindrical portion 44E of the main valve 43, positioned closer to the seat portion 44D side than the lateral hole 53A. The fixed throttle 53B extends in the radial direction of the main valve 43 (in a direction perpendicular to the central axis of the main valve 43), and is formed in the cylindrical portion 44E as a throttle hole having a smaller diameter than the lateral hole 53A.

[0072] That is, like the lateral hole 53A, the fixed orifice 53B also penetrates between the outer circumferential side and the inner circumferential side of the cylindrical portion 44E. The fixed orifice 53B is provided at a position corresponding to the tool clearance groove 44J. As a result, the fixed orifice 53B opens into the tool clearance groove 44J. The lateral hole 53A and the fixed orifice 53B communicate between the inlet-side flow path 25 and the outlet-side flow path 27 via the inside of the main valve 43 (more specifically, the inside of the cylindrical portion 44E).

[0073] Next, the feedback aperture 54 will be described.

[0074] The feedback orifice 54 is provided in the valve member 44 of the main valve 43. Here, in the first embodiment, the range in which the opening amount of the main valve orifice 53 can be proportionally controlled is expanded relative to the proportional control range of the opening amount of the pilot orifice 56, and the configuration is such that the oscillatory behavior of the displacement of the main valve 43 caused by fluid force can be suppressed in the vicinity of the displacement of the main valve 43 where the opening / closing of the opening (side hole 53A) of the main valve orifice 53 is switched between open and closed. For this reason, as shown in Figs. 2 to 11, the feedback orifice 54 is composed of a small change orifice 54A whose rate of change in the opening amount relative to the displacement amount of the main valve 43 is small, and a large change orifice 54B whose rate of change in the opening amount is large. The detailed configuration of the feedback orifice 54 will be described later.

[0075] The control valve device 21 equipped with the flow control valve 33 according to the first embodiment has the above-mentioned configuration, and its operation will now be described.

[0076] First, the pressure oil discharged from the hydraulic pump 11 flows from the branch pipe 13A of the pump pipe 13 through the inlet side passage 25 of the main housing 23 and between the main valve 43 and the communication hole 26 of the flow control valve 33 (main valve throttle 53) to the outlet side passage 27. The pressure oil that has flowed to the outlet side passage 27 is supplied to or discharged from the arm cylinder 9 via the pair of actuator pipes 19A, 19B by switching the arm control valve 18 from the neutral position (A) to the switching position (B) or (C).

[0077] The flow rate of the pressure oil supplied to the arm cylinder 9 is determined by the opening area of ​​the main valve 43 of the flow control valve 33 and the opening area of ​​the spool 29 (switching lands 29A, 29B) of the arm control valve 18. When blocking the flow of pressure oil from the inlet-side flow path 25 of the main housing 23 toward the outlet-side flow path 27, the main valve 43 of the flow control valve 33 blocks off both the flow paths 25, 27 by seating a seat portion 44D on a main valve seat 46 of the main housing 23.

[0078] When the flow rate from the inlet-side flow passage 25 to the outlet-side flow passage 27 is variably controlled, pilot pressure is supplied to the pilot chamber 57 of the pilot valve 55 to pressurize the pilot chamber 57, and the pilot valve 55 is displaced to the right in FIG. 2. This variably controls the opening amount of the pilot throttle 56 of the pilot valve 55. For example, when the pressure of the inlet-side flow passage 25 is higher than that of the outlet-side flow passage 27, a flow occurs from the inlet-side flow passage 25 to the outlet-side flow passage 27. At this time, a flow occurs from the inlet-side flow passage 25 to the check valve 62, the feedback throttle 54, and the back pressure chamber 47, and a flow also occurs from the back pressure chamber 47 to the pilot throttle upstream pipe 51, the pilot throttle 56, the pilot throttle downstream pipe 52, and the outlet-side flow passage 27.

[0079] Here, when the amount of displacement of the main valve 43 in the valve opening direction is large relative to the opening of the pilot throttle 56, which is the opening between the back pressure chamber 47 and the outlet side flow path 27, the opening of the feedback throttle 54 is large, so the pressure in the back pressure chamber 47 approaches the pressure in the inlet side flow path 25. As a result, the main valve 43 is displaced in the valve closing direction due to the force in the valve closing direction caused by the pressure in the back pressure chamber 47. As a result, the opening of the feedback throttle 54 decreases with the displacement of the main valve 43, so the pressure in the back pressure chamber 47 is reduced and the force in the valve closing direction caused by the pressure in the back pressure chamber 47 acting on the main valve 43 decreases.

[0080] As a result of this position feedback action, the main valve 43 stops at a position where the "valve opening force due to the pressures in the inlet-side flow path 25 and the outlet-side flow path 27" and the "valve closing force due to the pressure in the back pressure chamber 47 and the valve spring 48" are balanced. This controls the displacement of the main valve 43 so that the opening of the feedback throttle 54 corresponds to the opening of the variably controlled pilot throttle 56. By controlling the opening of the main valve throttle 53 accordingly, the flow rate from the inlet-side flow path 25 to the outlet-side flow path 27 can be variably controlled.

[0081] On the other hand, when the flow rate from the inlet side flow passage 25 to the outlet side flow passage 27 is controlled to a minimum, the pilot chamber 57 is pressurized to a maximum pressure, the pilot valve 55 is displaced to a maximum displacement amount, and the opening amount of the pilot throttle 56 is controlled to a minimum. Here, for example, when the pressure in the inlet side flow passage 25 is higher than that of the outlet side flow passage 27, a flow occurs from the inlet side flow passage 25 to the outlet side flow passage 27. At this time, a flow occurs from the inlet side flow passage 25 to the check valve 62, the feedback throttle 54, and the back pressure chamber 47, and a flow also occurs from the back pressure chamber 47 to the pilot throttle upstream pipe 51, the pilot throttle 56, the pilot throttle downstream pipe 52, and the outlet side flow passage 27.

[0082] By the above-mentioned position feedback action, the displacement amount of the main valve 43 is controlled to a minimum so that the opening amount of the feedback orifice 54 corresponds to the opening amount of the pilot orifice 56. In conjunction with this, the opening amount of the main valve orifice 53 is controlled to a minimum, so that the flow rate from the inlet side flow path 25 to the outlet side flow path 27 can be controlled to a minimum.

[0083] Regarding the load check function, when the pressure of the inlet-side flow passage 25 is lower than that of the outlet-side flow passage 27, a backflow tends to occur from the outlet-side flow passage 27 to the inlet-side flow passage 25. At this time, a flow occurs from the outlet-side flow passage 27 to the pilot throttle downstream pipe 52, the pilot throttle 56, the pilot throttle upstream pipe 51, the back pressure chamber 47, the feedback throttle 54, the check valve 62, and the inlet-side flow passage 25, but this flow is blocked by the check valve 62. As a result, the pressures of the back pressure chamber 47 and the outlet-side flow passage 27 become equal, and a force in the valve closing direction due to the pressure of the back pressure chamber 47 is generated in the main valve 43, displacing the main valve 43 in the valve closing direction. As a result, the seat portion 44D of the main valve 43 sits on the main valve seat 46, and the flow from the outlet-side flow passage 27 to the main valve throttle 53 and the inlet-side flow passage 25 is blocked. As a result, a backflow from the outlet-side flow passage 27 to the inlet-side flow passage 25 is prevented, and the load check function can be achieved.

[0084] As shown in Figs. 2 to 11, the feedback throttle 54 is composed of a small change throttle 54A having a small rate of change in the opening amount relative to the displacement amount of the main valve 43, and a large change throttle 54B having a large rate of change in the opening amount. The small change throttle 54A and the large change throttle 54B are separately provided on the outer circumferential surface of the main valve 43 (valve member 44). In this case, the small change throttle 54A and the large change throttle 54B are alternately provided at 90 degrees intervals in the circumferential direction of the main valve 43 (valve member 44). That is, two small change throttles 54A are provided on the outer circumferential surface of the valve member 44, spaced 180 degrees apart in the circumferential direction. Two large change throttles 54B are provided on the outer circumferential surface of the valve member 44, spaced 180 degrees apart in the circumferential direction. The small change throttle 54A is shifted 90 degrees from the large change throttle 54B in the circumferential direction.

[0085] The small change throttle 54A is configured to open at least in the displacement range of the main valve 43 where the opening (side hole 53A) of the main valve throttle 53 is blocked (corresponding to section L1 in FIG. 6). In this case, as shown in FIG. 9, the small change throttle 54A extends in the axial direction of the main valve 43 and is formed in the main valve 43 (valve member 44) as a notch (groove) with a constant depth. The small change throttle 54A extends in the axial direction of the main valve 43 (valve member 44) over both the "displacement range of the main valve 43 where the opening (side hole 53A) of the main valve throttle 53 is blocked (corresponding to section L1 in FIG. 6)" and the "displacement range of the main valve 43 where the opening (side hole 53A) of the main valve throttle 53 is open (corresponding to section L2 in FIG. 6)."

[0086] On the other hand, the large change throttle 54B is configured so that the displacement amount of the main valve 43 at which the opening of the large change throttle 54B switches between open and closed matches the displacement amount of the main valve 43 at which the opening (side hole 53A) of the main valve throttle 53 switches between open and closed. That is, the large change throttle 54B is configured to open in the displacement range of the main valve 43 where the opening (side hole 53A) of the main valve throttle 53 is open (corresponding to section L2 in FIG. 6). In this case, as shown in FIG. 10, the large change throttle 54B extends in the axial direction of the main valve 43 and is formed in the main valve 43 (valve member 44) as a groove (notch) whose depth increases toward the tip side of the main valve 43. Also, the large change throttle 54B extends in the axial direction of the main valve 43 (valve member 44) over the "displacement range of the main valve 43 where the opening (side hole 53A) of the main valve throttle 53 is open (corresponding to section L2 in FIG. 6)".

[0087] Thus, in the first embodiment, the feedback throttle 54 has a boundary section K which divides a change section of the opening amount of the feedback throttle 54 so that the rate of change of the opening amount of the feedback throttle 54 with respect to the displacement of the main valve 43 in the direction approaching the main valve seat 46 changes to the smaller side. The boundary section K corresponds to a section (change section) which divides sections with different change rates. The boundary section K exists within a displacement region of the main valve 43 corresponding to a position where the opening (side hole 53A) of the main valve throttle 53 is blocked with respect to the displacement of the main valve 43 in the direction approaching the main valve seat 46. In other words, the boundary section K exists at a position which coincides with the displacement (displacement region) of the main valve 43 corresponding to a position where the opening (side hole 53A) of the main valve throttle 53 is blocked. In this case, the feedback throttle 54 has a small change section L1 where the rate of change of the opening amount of the feedback throttle 54 with respect to the displacement of the main valve 43 is small, and a large change section L2 where the rate of change of the opening amount is large.

[0088] The small change section L1 corresponds to the small change throttle 54A. The small change section L1 exists in a section approaching the main valve seat 46 of the main valve 43 with the displacement (displacement region) of the main valve 43 corresponding to the position where the opening (side hole 53A) of the main valve throttle 53 switches between open and closed as a boundary. The large change section L2 corresponds to the large change throttle 54B and the small change throttle 54A. The large change section L2 exists in a section away from the main valve seat 46 of the main valve 43 with the displacement (displacement region) of the main valve 43 corresponding to the position where the opening (side hole 53A) of the main valve throttle 53 switches between open and closed as a boundary. In the first embodiment, the feedback throttle 54 is composed of two types of notches that open at different positions (displacement position, displacement region) relative to the displacement of the main valve 43, i.e., the small change throttle 54A and the large change throttle 54B.

[0089] In the first embodiment, the boundary K where the rate of change of the opening amount of the feedback orifice 54 changes (i.e., the boundary K where the large change orifice 54B switches between open and closed) is located within the displacement region of the main valve 43 corresponding to the position where the opening (side hole 53A) of the main valve orifice 53 is closed with respect to the displacement of the main valve 43 in the direction approaching the main valve seat 46. In other words, the boundary K is located at a position that coincides with the displacement (displacement region) of the main valve 43 corresponding to the position where the opening (side hole 53A) of the main valve orifice 53 is closed. In this case, "matching" does not only mean "perfectly matching", but also includes cases where the two do not match completely (where they substantially match) due to, for example, unavoidable deviations associated with manufacturing errors. Also, for example, "matching" includes cases where the range in which the opening amount of the main valve orifice 53 can be proportionally controlled can be expanded and the vibration behavior of the displacement of the main valve 43 due to fluid forces can be suppressed. For example, the displacement of the main valve 43 (the amount of displacement in the axial direction from the maximum open position to the maximum closed position) is assumed to be H. In this case, the "coincidence" also includes the case where the boundary part K deviates, for example, by about ±(1 / 35 to 1 / 70)H from the position that "completely coincides" with the displacement (displacement region) of the main valve 43 corresponding to the position where the opening (side hole 53A) of the main valve throttle 53 is blocked. In other words, the "coincidence" is also allowed even if it does not "completely coincide".

[0090] Figures 12 and 13 show the characteristics of the flow control valve 33 of the first embodiment. The state of the main valve 43 according to the displacement of the pilot valve 55 will be described with reference to Figures 12 and 13. When the displacement of the pilot valve 55 is "0", the opening of the pilot throttle 56 is at its maximum, and the displacement of the main valve 43 in the valve opening direction and the opening of the main valve throttle 53 are also at their maximums. The state of the main valve 43 at this time corresponds to Figure 5.

[0091] 12, when the displacement of pilot valve 55 changes from "0" to "displacement A", the opening of pilot orifice 56 decreases, and accordingly the displacement of main valve 43 and the opening of main valve orifice 53 also decrease, and the opening of main valve orifice 53 reaches "0". At this time, the opening of feedback orifice 54 is composed of the sum of the openings of small change orifice 54A and large change orifice 54B, as shown in Fig. 13. Also, the state of main valve 43 at "displacement A" of pilot valve 55 corresponds to Fig. 4.

[0092] Next, in Fig. 12, when the displacement of the pilot valve 55 changes from "displacement A" to "displacement B", the opening of the pilot orifice 56 decreases, and accordingly the displacement of the main valve 43 also decreases and reaches "0". At this time, the opening of the feedback orifice 54 is composed only of the opening of the small change orifice 54A, as shown in Fig. 13. Also, the state of the main valve 43 at "displacement B" of the pilot valve 55 corresponds to Fig. 3.

[0093] In the first embodiment as described above, the range over which the opening amount of the main valve throttle 53 can be proportionally controlled can be expanded relative to the proportional control range of the opening amount of the pilot throttle 56. Also, in the vicinity of the displacement (displacement range) of the main valve 43 where the opening (side hole 53A) of the main valve throttle 53 switches between open and closed, the oscillatory behavior of the displacement of the main valve 43 due to fluid force can be suppressed, enabling highly accurate flow control. This point will be explained by comparing the characteristics of the flow control valve 33 of the first embodiment with the characteristics of a flow control valve 101 (FIG. 24) of a comparative example.

[0094] Figures 12 and 13 show the characteristics of the flow control valve 33 of the first embodiment. In contrast, the dashed line in Figure 13 (characteristic line 100) and Figure 25 show the characteristics of a flow control valve 101 (Figure 24) of a comparative example. In the first embodiment, as shown in Figure 13, while matching the minimum and maximum opening amounts of the feedback throttle 103 of the comparative example, the opening amount of the feedback throttle 54 is made up of the sum of the opening amounts of the small change throttle 54A and the large change throttle 54B in the displacement range of the main valve 43 where the main valve throttle 53 is open (corresponding to section L2 in Figure 6).

[0095] For this reason, the rate of change of the opening of the feedback throttle 54 in the first embodiment can be made larger than the rate of change of the opening of the feedback throttle 103 in the comparative example. This makes it possible to widen the range of the displacement of the pilot valve from "0" to "displacement A" in the first embodiment compared to the range of the displacement of the pilot valve from "0" to "displacement A" in the comparative example, as shown in Figures 12 and 25. As a result, the proportional control range of the opening of the main valve throttle 53 can be expanded, improving proportional controllability.

[0096] 13, in the displacement range of main valve 43 where the opening (side hole 53A) of main valve throttle 53 is blocked (corresponding to section L1 in FIG. 6), the opening of feedback throttle 54 is constituted only by small change throttle 54A. Therefore, the rate of change in the opening of feedback throttle 54 in the first embodiment can be made smaller than the rate of change in the opening of feedback throttle 103 in the comparative example.

[0097] 12 and 25, the range from "displacement A" to "displacement B" of the pilot valve in the first embodiment can be narrowed compared to the range from "displacement A" to "displacement B" of the pilot valve in the comparative example. This makes it possible to increase the force due to pressure that functions as a position feedback action on the displacement of the main valve 43. As a result, the effect of the fluid force on the displacement of the main valve 43 can be relatively suppressed, and the oscillatory behavior of the displacement of the main valve 43 due to the fluid force can be suppressed.

[0098] As described above, according to the first embodiment, the feedback throttle 54 has a boundary portion K which divides a range in which the opening of the feedback throttle 54 changes so that the rate of change of the opening of the feedback throttle 54 relative to the displacement of the main valve 43 in the direction approaching the main valve seat 46 changes to the smaller side. The boundary portion K exists within a displacement range of the main valve 43 which corresponds to a position where the opening (side hole 53A) of the main valve throttle 53 is blocked relative to the displacement of the main valve 43 in the direction approaching the main valve seat 46. For this reason, when the opening of the pilot throttle 56 is gradually reduced, the main valve 43 displaces until the opening of the feedback throttle 54 reaches the boundary portion K, and the opening of the main valve throttle 53 can be proportionally controlled in this range, i.e., "range L2".

[0099] Furthermore, when the opening amount of the pilot orifice 56 decreases, the main valve 43 is displaced until the opening amount of the feedback orifice 54 reaches a corresponding value, but after passing the boundary K, the change in the opening amount of the feedback orifice 54 becomes smaller. Therefore, compared with before passing the boundary K, the change rate of the displacement of the main valve 43 becomes larger, and the main valve 43 is seated on the main valve seat 46. In this section, i.e., "section L1", the opening (side hole 53A) of the main valve orifice 53 is blocked, and the change rate of the displacement of the main valve 43 is large. Therefore, the range in which the opening (side hole 53A) of the main valve orifice 53 is blocked can be reduced relative to the proportional control range of the opening amount of the pilot orifice 56, and the range in which the main valve orifice 53 is open can be expanded. That is, the first problem described above can be solved.

[0100] Furthermore, in the section after passing through boundary K, i.e., in "section L1", the fact that the rate of change in the displacement of the main valve 43 is large means that the force due to the pressure that functions as a position feedback action on the displacement of the main valve 43 is large. This makes it possible to relatively suppress the effect of the fluid force on the displacement of the main valve 43. As a result, it is possible to suppress the oscillatory behavior of the displacement of the main valve 43 due to the fluid force. In other words, the second problem described above can also be solved.

[0101] According to the first embodiment, the feedback throttle 54 has a small change section L1 and a large change section L2. The small change section L1 exists in a section in a direction approaching the main valve seat 46 of the main valve 43, with a boundary being a displacement position (displacement region) corresponding to the position of the main valve 43 where the opening (side hole 53A) of the main valve throttle 53 switches between open and closed. The large change section L2 exists in a section in a direction away from the main valve seat 46 of the main valve 43, with a boundary being a displacement position (displacement region) of the main valve 43 corresponding to the position where the opening (side hole 53A) of the main valve throttle 53 switches between open and closed. For this reason, the boundary between the small change section L1 and the large change section L2 can be set as a boundary section K where the rate of change of the opening amount of the feedback throttle 54 changes.

[0102] According to the first embodiment, the feedback throttle 54 is composed of two types of notches, namely, small change throttle 54A and large change throttle 54B, which have different displacement positions (displacement regions) that open in response to the displacement of the main valve 43. For this reason, the boundary between "one notch (small change throttle 54A)" and "the other notch (large change throttle 54B)" of the two types of notches can be set as boundary part K where the rate of change of the opening amount of the feedback throttle changes.

[0103] Next, Fig. 14 to Fig. 17 show a second embodiment. The second embodiment is characterized in that the feedback throttle is configured by one type of notch whose width and depth differ midway. In the second embodiment, the same components as those in the first embodiment described above are given the same reference numerals, and the description thereof will be omitted.

[0104] The feedback throttle 71 of the second embodiment is configured such that a small change throttle 71A, whose rate of change in opening amount relative to the displacement amount of the main valve 43 is small, and a large change throttle 71B, whose rate of change in opening amount is large, are connected to each other. That is, the feedback throttle 71 is configured as one type of throttle in which the small change throttle 71A and the large change throttle 71B are connected to each other. Two feedback throttles 71 are provided 180 degrees apart in the circumferential direction of the main valve 43 (valve member 44).

[0105] The small change throttle 71A is configured to open in a displacement range (corresponding to section L1 in Fig. 14) of the main valve 43 where the opening (side hole 53A) of the main valve throttle 53 is blocked. In this case, as shown in Fig. 16 and Fig. 17, the small change throttle 71A extends in the axial direction of the main valve 43 and is formed in the main valve 43 (valve member 44) as a notch (groove) with a constant depth.

[0106] On the other hand, the large change throttle 71B is connected to the small change throttle 71A, and is configured so that the amount of displacement of the main valve 43 when it switches from the small change throttle 71A to the large change throttle 71B matches the amount of displacement of the main valve 43 when the opening (side hole 53A) of the main valve throttle 53 switches between open and closed. That is, the large change throttle 71B is configured to open in the displacement range of the main valve 43 (corresponding to section L2 in FIG. 14) where the opening (side hole 53A) of the main valve throttle 53 is open. In this case, as shown in FIG. 16 and FIG. 17, the large change throttle 71B is formed in the main valve 43 (valve member 44) as a groove (notch) that extends in the axial direction of the main valve 43 and becomes deeper toward the tip side of the main valve 43. The large change throttle 71B is wider and deeper than the small change throttle 71A.

[0107] Thus, in the second embodiment, like the first embodiment, the feedback throttle 71 has a boundary section K which divides change sections of the opening amount of the feedback throttle 71 so that the rate of change of the opening amount of the feedback throttle 71 relative to the displacement of the main valve 43 in a direction approaching the main valve seat 46 changes to the smaller side. The boundary section K exists within a displacement region of the main valve 43 which corresponds to a position where the opening (side hole 53A) of the main valve throttle 53 is blocked relative to the displacement of the main valve 43 in a direction approaching the main valve seat 46. In this case, the feedback throttle 71 has a small change section L1 where the rate of change of the opening amount of the feedback throttle 71 relative to the displacement of the main valve 43 is small and a large change section L2 where the rate of change of the opening amount is large.

[0108] The small change section L1 corresponds to the small change orifice 71A. The small change section L1 exists in a section in a direction approaching the main valve seat 46 of the main valve 43, with the displacement (displacement position, displacement area) of the main valve 43 corresponding to the position where the opening (side hole 53A) of the main valve orifice 53 switches between open and closed as a boundary. The large change section L2 corresponds to the large change orifice 71B. The large change section L2 exists in a section in a direction away from the main valve seat 46 of the main valve 43, with the displacement (displacement position, displacement area) of the main valve 43 where the opening (side hole 53A) of the main valve orifice 53 switches between open and closed as a boundary. In the second embodiment, the feedback orifice 71 is composed of one type of mutually communicating notches formed with different combinations of widths and depths, that is, one type of notch (groove) that communicates the small change orifice 71A and the large change orifice 71B with each other.

[0109] In the second embodiment, the feedback orifice 71 is configured by the small change orifice 71A and the large change orifice 71B as described above, and its basic operation is not particularly different from that of the first embodiment. That is, the feedback orifice 71 of the second embodiment can also realize the opening characteristics shown in FIG. 13. Therefore, the second embodiment can also achieve the same effects as the first embodiment. In particular, according to the second embodiment, the feedback orifice 71 is configured by one type of mutually communicating notches configured by a combination of different widths and depths, that is, the notches that communicate with the small change orifice 71A and the large change orifice 71B. Therefore, the part of the notch that has a different width and depth, that is, the connection part (boundary) between the small change orifice 71A and the large change orifice 71B, can be made into the boundary part K where the change rate of the opening amount of the feedback orifice 71 changes.

[0110] In the above-mentioned second embodiment, an example has been described in which the feedback orifice 71 is configured by one type of mutually communicating notches configured by a combination of different widths and depths, i.e., a notch (groove) that communicates with the small change orifice 71A and the large change orifice 71B. However, this is not limiting, and for example, as in the first modified example shown in Figures 18 to 20, the feedback orifice 72 may be configured by one type of mutually communicating notches configured by a combination of the same widths but different depths, i.e., a notch (groove) that communicates with the small change orifice 72A and the large change orifice 72B.

[0111] 21 to 23, the feedback orifice 73 may be formed of one type of communicating notches having the same depth but different widths, i.e., a notch (groove) in which a small change orifice 73A and a large change orifice 73B communicate with each other. Although not shown, the feedback orifice may be formed of two or more types of communicating notches having different widths or depths. That is, the feedback orifice can be formed of at least one type of communicating notches having different widths or depths.

[0112] In the above-mentioned first embodiment, an example has been described in which the feedback throttle 54 is configured from two types of notches that differ in the position (displacement position, displacement region) that opens in response to the displacement of the main valve 43, i.e., the small change throttle 54A and the large change throttle 54B. However, this is not limiting, and for example, the feedback throttle 54 may be configured from three or more types of notches that differ in the position (displacement position, displacement region) that opens in response to the displacement of the main valve. In other words, the feedback throttle can be configured from at least two or more types of notches that differ in the position (displacement position, displacement region) that opens in response to the displacement of the main valve.

[0113] In the first embodiment, a case has been described where boundary portion K where the rate of change of the opening amount of the feedback throttle 54 changes exists within a displacement region of the main valve 43 corresponding to a position where the opening (side hole 53A) of the main valve throttle 53 is blocked with respect to displacement in a direction approaching the main valve seat 46 of the main valve 43. However, this is not limiting, and for example, as shown by a two-dot chain characteristic line 81 in Fig. 13, boundary portion K' where the rate of change of the opening amount of the feedback throttle changes may be within a displacement section (for example, within section L1 in Fig. 6) closer to the main valve seat of the main valve than within the displacement region of the main valve corresponding to the position where the opening of the main valve throttle is blocked with respect to displacement in a direction approaching the main valve seat of the main valve.

[0114] In this case, boundary K' can be positioned within the range of a triangle surrounded by points P1, P2, and P3 in Fig. 13. This makes it possible to expand the range in which the opening amount of the main valve throttle can be proportionally controlled and to suppress oscillatory behavior of the main valve, compared to characteristic line 100 of the comparative example shown by the dashed line in Fig. 13. In other words, the boundary can be configured to exist within a displacement region of the main valve corresponding to the position where the opening of the main valve throttle is blocked with respect to displacement of the main valve in a direction approaching the main valve seat, or to exist in a displacement section closer to the main valve seat of the main valve.

[0115] In other words, the boundary portion can be provided between the "displacement region of the main valve corresponding to the position where the opening of the main valve throttle is blocked" and the "position where the displacement amount of the main valve is zero (position where the main valve sits on the main valve seat)." In this case, it is most preferable that the boundary portion exists in the "displacement region of the main valve corresponding to the position where the opening of the main valve throttle is blocked." Also, it is more preferable that the boundary portion is closer to the "displacement region of the main valve corresponding to the position where the opening of the main valve throttle is blocked." The same applies to the second embodiment, the first modified example, and the second modified example.

[0116] In the first embodiment, the case where the feedback throttle 54 has one boundary K at which the rate of change of the opening amount changes has been described as an example. However, the present invention is not limited to this, and the number of boundaries may be two, three, or more. In this case, for example, a plurality of boundaries may be connected along the straight lines P1-P2 and P2-P3 in FIG. 13. That is, the feedback throttle may have at least one boundary that divides the change section of the opening amount of the feedback throttle so that the rate of change of the opening amount of the feedback throttle with respect to the displacement in the direction approaching the main valve seat of the main valve changes to the smaller side. At least one of the boundaries may be present in a displacement region of the main valve corresponding to the position where the opening of the main valve throttle is blocked with respect to the displacement in the direction approaching the main valve seat of the main valve, or may be present in a displacement section closer to the main valve seat of the main valve. This is the same for the second embodiment, the first modified example, and the second modified example.

[0117] In the first embodiment, the main housing 23 and the pilot housing 36 are used to form one (integral or common) casing. However, the present invention is not limited to this. For example, the main housing and the pilot housing may be disposed separately, and a connecting pipe may be provided between the main housing and the pilot housing. In this case, the main valve chamber is provided in the main housing. That is, the main valve chamber may be provided in the main housing, in addition to the configuration in which the main valve chamber is provided across the main housing and the pilot housing as in the above-mentioned embodiment. In short, the main valve chamber is provided in the housing (more specifically, at least the main housing of the main housing and the pilot housing). This also applies to the second embodiment, the first modified example, and the second modified example.

[0118] In the first embodiment, the pilot throttle 56 of the pilot valve 55 is configured to reduce the opening amount of the pilot flow path 50 in accordance with the displacement of the pilot valve 55. However, the present invention is not limited to this, and for example, the pilot throttle of the pilot valve may be configured to increase the opening amount of the pilot flow path in accordance with the displacement of the pilot valve. This also applies to the second embodiment, the first modified example, and the second modified example.

[0119] In the first embodiment, the flow control valve 33 that adjusts the flow rate of pressure oil supplied / discharged from the arm control valve 18 to the arm cylinder 9 has been described as an example. However, the present invention is not limited to this, and may be applied to a flow control valve for adjusting the flow rate of pressure oil supplied / discharged from the boom control valve 16 to the boom cylinder 8, and may also be applied to a flow control valve for supplying / discharging pressure oil to a bucket cylinder or other hydraulic actuator through a directional control valve. The same applies to the second embodiment, the first modified example, and the second modified example.

[0120] In the above-mentioned embodiments and modifications, the hydraulic excavator 1 has been taken as an example of the construction machine. However, the present invention is not limited to this and can be widely applied to various construction machines such as wheel loaders, hydraulic cranes, bulldozers, etc. Also, the flow control valve 33 may be configured to variably control the flow rate of the working fluid from a small flow rate to a large flow rate according to the displacement amount (lift amount) of the main valve 43, and can be widely applied as a flow control valve used in various industrial equipment and mechanical devices.

[0121] Furthermore, each embodiment and each modification is merely an example, and it goes without saying that partial substitution or combination of the configurations shown in each embodiment and each modification is possible. [Explanation of symbols]

[0122] 1: Hydraulic excavator (construction machinery) 21: Control valve device 22: Housing 25: Inlet side flow path 27: Outlet side flow path 33: Flow control valve 36: Pilot Housing 42: Main valve chamber 43: Main valve 44D: Seat section (valve section) 46: Main valve seat 47:Back pressure chamber 49: Feedback channel 50: Pilot channel 53: Main valve throttle 54, 71, 72, 73: Feedback throttle 54A: Small change aperture (notch, small change section, large change section) 54B: Large change aperture (notch, large change section) 55: Pilot valve 56: Pilot aperture 71A, 72A, 73A: Small change restriction (notch, small change section) 71B, 72B, 73B: Large change aperture (notch, large change section) K, K′: Boundary part

Claims

1. Housing and A main valve chamber provided in the housing; a main valve slidably provided in the main valve chamber and having a valve portion; a main valve seat that is provided at one end side of the main valve chamber and communicates or blocks the working fluid by seating or separating a valve portion of the main valve from the main valve; an inlet side flow passage that applies pressure to the main valve in a direction away from the main valve seat and introduces a working fluid from the outside of the main valve chamber into the main valve chamber; an outlet side flow passage that discharges the working fluid from inside the main valve chamber to outside the main valve chamber when the main valve is separated from the main valve seat and that applies a pressure to the main valve in a direction away from the main valve seat; a back pressure chamber provided at the other end side of the main valve chamber and configured to apply pressure to the main valve in a direction approaching the main valve seat; a feedback passage provided in the main valve and communicating between the inlet side passage and the back pressure chamber; a pilot passage provided in the housing and communicating between the back pressure chamber and the outlet side passage; a main valve throttle provided in the main valve and configured to increase an opening between the inlet side flow passage and the outlet side flow passage as the main valve is displaced in a direction away from the main valve seat; a feedback throttle provided between the feedback flow passage and the back pressure chamber, the feedback throttle increasing an opening between the feedback flow passage and the back pressure chamber as the main valve is displaced in a direction away from the main valve seat; a pilot valve slidably disposed in the housing; a pilot throttle provided in the pilot valve for decreasing or increasing an opening amount of the pilot flow path in accordance with a displacement of the pilot valve; A flow control valve having a flow control function for variably controlling a flow rate from the inlet side flow path to the outlet side flow path by controlling a displacement amount of the main valve in accordance with an opening amount of the pilot throttle, the feedback throttle has at least one boundary portion which divides a range in which an opening of the feedback throttle changes so that a rate of change of the opening of the feedback throttle with respect to displacement of the main valve in a direction toward the main valve seat changes to a smaller rate, At least one of the boundaries is present within a displacement region of the main valve corresponding to a position where an opening of the main valve throttle is blocked with respect to displacement of the main valve in a direction approaching the main valve seat, or is present in a displacement section closer to the main valve seat of the main valve than the displacement region. A flow control valve comprising:

2. 2. The flow control valve according to claim 1, the feedback throttle has a small change section in which a rate of change in an opening of the feedback throttle with respect to a displacement of the main valve is small, and a large change section in which a rate of change in an opening of the feedback throttle with respect to a displacement of the main valve is large, the small change section exists in a section in a direction approaching the main valve seat of the main valve, with a displacement region of the main valve corresponding to a position where an opening of the main valve throttle is switched between open and closed as a boundary, The large change section exists in a section in a direction away from the main valve seat of the main valve, with a boundary being a displacement region of the main valve corresponding to a position where the opening of the main valve throttle is switched between open and closed. A flow control valve comprising:

3. 2. The flow control valve according to claim 1, The feedback throttle is composed of at least two types of notches that open at different positions relative to the displacement of the main valve. A flow control valve comprising:

4. 2. The flow control valve according to claim 1, The feedback throttle is composed of at least one or more types of notches that communicate with each other and are configured in a combination of at least one different width or depth. A flow control valve comprising:

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