Hydraulic valves and hydraulic circuits

Abstract

To finely control a flow rate while securing rigidity of a spool.SOLUTION: A flow control valve 40 controls a flow rate of oil from a meter-out port 41 to a drain port 42 through a main passage 63 by varying an opening area of a meter-out passage 63f with respect to the meter-out port 41 in accordance with movement of a spool 62. The main passage 63 of the spool 62 has a meter-out region 63b in which the meter-out passage 63f is provided, a drain region 63d in which a drain passage 63g is provided, and a tapered region 63c which connects the meter-out region 63b and the drain region 63d. An inside diameter of the meter-out region 63b is larger than that of the drain region 63d, and the tapered region 63c is formed into a tapered shape whose inside diameter is gradually reduced toward the drain region 63d.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a hydraulic valve having a spool inside a valve body and a hydraulic circuit.

Background Art

[0002] As this type of hydraulic valve, many are provided with a groove portion on the outer periphery of the spool (see, for example, Patent Document 1). In this hydraulic valve, since the spool moves in the axial direction with respect to the valve body, there is a problem that it is easily affected by the flow force. That is, when the port of the valve body starts to open due to the movement of the spool, the oil passes in an oblique direction. For this reason, a flow force is generated in the direction in which the spool closes the port, which may cause problems such as difficulty in fine flow rate control.

[0003] In order to reduce the influence of such flow force, there is also provided a hydraulic valve in which an oil passage is provided inside the spool. That is, in this hydraulic valve, a main passage along the axial direction is provided inside the spool, and an auxiliary passage is provided along the radial direction so as to open from the main passage to the outer peripheral surface of the spool, thereby reducing the flow force (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in order to precisely control the flow rate, it is preferable to open a number of independent sub-passages on the outer surface of the spool. To provide a number of sub-passages in the spool, it is necessary to increase the inner diameter of the main passage due to manufacturing issues. However, in a spool with an increased inner diameter of the main passage, it is difficult to ensure sufficient rigidity, and there is a concern that it may deform, such as bending, when a large hydraulic pressure is applied.

[0006] In view of the above circumstances, the present invention aims to provide a hydraulic valve and a hydraulic circuit that can perform precise flow rate control while ensuring the rigidity of the spool. [Means for solving the problem]

[0007] To achieve the above objective, the hydraulic valve according to the present invention comprises a valve body having a first port and a second port independent of each other, and a spool disposed to be movable along the axis of the valve body, wherein the spool is provided with a main passage portion provided in the axial portion, a first passage portion provided between the main passage portion and the outer circumferential surface and communicating with the first port, and a second passage portion provided between the main passage portion and the outer circumferential surface and communicating with the second port, and the hydraulic valve controls the flow rate of oil from the first port to the second port via the main passage portion by changing the opening area of ​​the first passage portion relative to the first port as the spool moves, wherein the main passage portion of the spool has a first region where the first passage portion is provided, a second region where the second passage portion is provided, and a third region that connects the first region and the second region, wherein the inner diameter of the first region is formed to be larger than that of the second region, and the third region is configured in a tapered shape in which the inner diameter gradually decreases toward the second region. [Effects of the Invention]

[0008] According to the present invention, since only the first region forming the first passage in the spool is configured with a large diameter, the influence of flow force can be reduced without causing rigidity problems in the spool. Moreover, since a third region is provided between the first and second regions, in which the inner diameter gradually decreases, even if bubbles are generated in the oil flowing from the first port into the main passage, they will smoothly pass through the third region, reach the second region without reversing back to the first region, and be discharged to the second port. Therefore, there is no risk of bubbles stagnating in the first region or reaching the land portion of the valve body via the first passage, and there is no concern about erosion occurring in the land portion of the valve body. As a result, the position of the spool can be controlled with high precision, enabling fine flow rate control. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a circuit diagram showing a hydraulic circuit to which a hydraulic valve, which is an embodiment of the present invention, is applied. [Figure 2] Figure 2 shows the state in which the hydraulic cylinder extends in the circuit diagram shown in Figure 1. [Figure 3] Figure 3 shows the state in which the hydraulic cylinder is in a retracted state in the circuit diagram shown in Figure 1. [Figure 4] Figure 4 is a cross-sectional view showing the structure of a hydraulic valve applied to the circuit diagram shown in Figure 1. [Figure 5] Figure 5 is an enlarged cross-sectional view of the main part of the hydraulic valve shown in Figure 4. [Modes for carrying out the invention]

[0010] Hereinafter, preferred embodiments of the hydraulic valve and hydraulic circuit according to the present invention will be described in detail with reference to the attached drawings.

[0011] Figures 1 to 3 show a hydraulic circuit according to an embodiment of the present invention. The hydraulic circuit illustrated here is for operating a hydraulic cylinder 1 with oil supplied from a hydraulic pump. The hydraulic cylinder 1 is a single-rod double-acting type equipped with a single piston 2. In this embodiment, the hydraulic cylinder 1 for operating a boom 3 in a work machine is illustrated. The work machine has an upper slewing body 5 rotatably disposed on top of a lower traveling body 4 around a slewing axis that runs vertically, and the boom 3 is mounted on the upper slewing body 5. The boom 3 is rotatably supported on the upper slewing body 5 via its base end by a boom support shaft that runs horizontally. Reference numeral 6 in the figures indicates an arm provided at the tip of the boom 3, and reference numeral 7 indicates a bucket provided at the tip of the arm.

[0012] The hydraulic cylinder 1 is connected to the upper slewing body 5 via the cylinder body 8 and to the boom 3 via the rod 9. When the hydraulic cylinder 1 extends, the tip of the boom 3 moves upward relative to the upper slewing body 5, and when the hydraulic cylinder 1 retracts, the tip of the boom 3 moves downward relative to the upper slewing body 5. The hydraulic cylinder 1 has a bottom oil passage 11 connected to the bottom chamber 1a and a rod oil passage 12 connected to the rod chamber 1b. The bottom oil passage 11 branches into a first bottom oil passage 11A and a second bottom oil passage (meter-out oil passage) 11B. Similarly, the rod oil passage 12 branches into a first rod oil passage 12A and a second rod oil passage 12B.

[0013] The hydraulic circuit includes a hydraulic pump 20, a directional control valve 30 for operating the hydraulic cylinder 1, and a flow control valve (hydraulic valve) 40.

[0014] The hydraulic pump 20 is a variable displacement type driven by an engine (not shown). A pump oil passage 22 having a check valve 21 is connected to the discharge port of the hydraulic pump 20.

[0015] The directional control valve 30 is operated by pilot pressure from an operating valve (not shown) and is configured to switch the connection state of the pump port 33 and the tank port 34 to the first input / output port 31 and the second input / output port 32. More specifically, when the directional control valve 30 is positioned in the neutral position shown in Figure 1, the two input / output ports 31 and 32, the pump port 33, and the tank port 34 are all blocked. When the directional control valve 30 is moved to the extended position as shown in Figure 2, the first input / output port 31 is connected to the pump port 33 and the second input / output port 32 is connected to the tank port 34. On the other hand, when the directional control valve 30 is moved to the retracted position as shown in Figure 3, the first input / output port 31 is connected to the tank port 34 and the second input / output port 32 is connected to the pump port 33. The directional control valve 30 has a first bottom oil passage 11A connected to the first input / output port 31, and a first rod oil passage 12A connected to the second input / output port 32. The pump oil passage 22 is connected to the pump port 33, and the tank oil passage 51 leading to the oil tank 50 is connected to the tank port 34.

[0016] The flow control valve 40 is operated by pilot pressure from an operating valve (not shown) and is configured to switch the connection state of the drain port (second port) 42 and the regeneration port 43 to the meter out port (first port) 41. More specifically, when the flow control valve 40 is positioned in the closed position shown in the figure, the meter out port 41, the drain port 42, and the regeneration port 43 are all shut off. When the flow control valve 40 is moved to the left from this state and positioned in the control position as shown in the figure, the meter out port 41 is connected to the drain port 42 and the regeneration port 43. Between the meter out port 41 and the drain port 42 and regeneration port 43, a meter out throttle 44 is provided such that its opening area increases as the pilot pressure applied from the operating valve (not shown) increases. Between the meter out port 41 and the drain port 42, a drain-side fixed throttle 45 is provided downstream of the meter out throttle 44. Between the meter-out port 41 and the regeneration port 43, a check valve 46 and a regeneration-side fixed throttle 47 are provided downstream of the meter-out throttle 44. The flow control valve 40 has a second bottom oil passage 11B connected to the meter-out port 41 and a tank oil passage 51 connected to the drain port 42. The regeneration port 43 is connected to a second rod oil passage 12B.

[0017] Figures 4 and 5 show the specific configuration of the flow control valve 40. Hereinafter, the configuration of the flow control valve 40 will be described in detail with appropriate reference to Figures 4 and 5, and the characteristic parts of the present invention will also be explained. As is clear from the figure, this flow control valve 40 includes a valve body 60 configured in a block shape. The valve body 60 is provided with a spool hole 61, and the meter out port 41, drain port 42, and regeneration port 43 described above are provided so as to communicate with the spool hole 61. The spool hole 61 is a through hole with a circular cross section and an axis along a straight line, and includes a spool 62 inside. The spool 62 is a columnar member having an outer diameter that fits into the spool hole 61, and is disposed in the valve body 60 so as to be movable along the axis of the spool hole 61. Although not shown in the figure, between the end of the spool 62 and the valve body 60, there is provided a return spring 48 (see Figure 1) that biases the spool 62 to the right side in Figure 4 with respect to the valve body 60 and maintains it in the normal position, and a pressure chamber 49 (see Figure 1) to which pilot pressure is supplied from an operation valve (not shown). The pressure chamber 49 functions to move the spool 62 to the left side in Figure 4 against the spring force of the return spring 48 when pilot pressure is supplied from an operation valve (not shown) so as to place the direction switching valve 30 in the retracted position. The meter out port 41, drain port 42, and regeneration port 43 are configured to have a portion surrounding the periphery of the spool hole 61, and are provided at positions spaced apart from each other in the axial direction of the spool 62. In the illustrated example, the drain port 42 and the regeneration port 43 are provided in portions on both sides sandwiching the meter out port 41.

[0018] The spool 62 is provided with a main passage portion 63. The main passage portion 63 is a through hole formed in the axial portion of the spool 62, and has a reference region 63a, a meter out region (first region) 63b, a taper region (third region) 63c, a drain region (second region) 63d, and a valve region 63e. The reference region 63a is a cavity with a circular cross section and is configured to have a constant inner diameter.

[0019] The meter-out region 63b is a circular cavity with a constant inner diameter, and is located adjacent to the right side of the reference region 63a in Figure 4. The inner diameter of the meter-out region 63b is formed to be larger than that of the reference region 63a. A meter-out passage section (first passage section) 63f for forming the meter-out throttle 44 described above is formed in this meter-out region 63b. The meter-out passage section 63f is a circular through-hole formed along the radial direction of the spool 62, and multiple such passages with different cross-sectional areas are formed side by side in the circumferential and axial directions. When the spool 62 is in its normal position, these meter-out passage sections 63f are completely covered by the land section 60a located between the meter-out port 41 and the drain port 42 in the valve body 60. In contrast, when the spool 62 moves to the left relative to the valve body 60, the meter-out passage 63f opens to the meter-out port 41 and functions to gradually increase the opening area between the main passage 63 and the meter-out port 41.

[0020] The tapered region 63c is a cavity located adjacent to the right side of the meter-out region 63b, and is formed in a tapered shape where the inner diameter gradually decreases toward the right. In this tapered region 63c, the inner diameter decreases at a constant rate, and the inner circumferential surface extends linearly in the cross-section including the axis. In the illustrated example, the tapered region 63c is formed such that the inclination angle θ with respect to the meter-out region 63b is 21°. The inclination angle θ of the tapered region 63c is preferably in the range of 15 to 30°. In other words, it is preferable that the rate at which the inner diameter decreases toward the right along the axial direction is in the range of tan15° to tan30°. The inner diameter of the rightmost part of the tapered region 63c is set to be larger than that of the reference region 63a and smaller than that of the meter-out region 63b.

[0021] The drain area 63d is a circular cavity with a constant inner diameter provided adjacent to the right side of the tapered area 63c. The inner diameter of the drain area 63d is the same as the narrowest part of the tapered area 63c. In this drain area 63d, a drain passage portion (second passage portion) 63g for forming the drain-side fixed throttle 45 described above is provided. The drain passage portion 63g is a through-hole with a circular cross-section formed along the radial direction of the spool 62, and a plurality of them are formed at equal intervals along the circumferential direction. These drain passage portions 63g are provided so as to always communicate with the drain port 42 from the state where the spool 62 is arranged at the normal position to the state where the spool 62 moves to the left side and all the meter-out passage portions 63f open to the meter-out port 41. A plug 64 is attached to a portion on the right side of the main passage portion 63 relative to the drain area 63d.

[0022] The valve area 63e is a circular cavity provided adjacent to a portion on the left side of the reference area 63a. In this valve area 63e, a valve body 65 and a return spring 66 for forming the check valve 46 described above are accommodated, and a regeneration passage portion 63h for forming the regeneration-side fixed throttle 47 described above is provided. The valve body 65 blocks the oil flow between them when it abuts against a valve seat portion 63i provided between the reference area 63a and the valve area 63e, while allowing the oil flow between them when it moves to the left side and separates from the valve seat portion 63i. The return spring 66 is interposed between a plug 67 attached to a portion on the left side of the valve area 63e in the main passage portion 63 and the valve body 65, and biases the valve body 65 to always abut against the valve seat portion 63i. The regeneration passage portion 63h is a through-hole with a circular cross-section formed along the radial direction of the spool 62, and a plurality of them are formed at equal intervals along the circumferential direction.

[0023] In the hydraulic circuit configured as described above, when the operating valve (not shown) is operated to raise the tip of the boom 3, the directional control valve 30 is moved to the extended position with the flow control valve 40 in the normal position, as shown in Figure 2. As a result, the oil discharged from the hydraulic pump 20 is supplied to the bottom chamber 1a of the hydraulic cylinder 1 via the pump oil passage 22 and the bottom oil passage 11. This causes the hydraulic cylinder 1 to extend, and the tip of the boom 3 moves upward.

[0024] On the other hand, when the operating valve (not shown) is operated to lower the tip of the boom 3, as shown in Figure 3, the direction switching valve 30 is positioned in the retracted position, and the spool 62 of the flow control valve 40 moves to the left relative to the valve body 60, and the opening area of ​​the meter-out passage 63f (meter-out throttle 44) changes according to the pilot pressure applied from the operating valve (not shown). As a result, a portion of the oil discharged from the bottom oil passage 11 passes through the second bottom oil passage 11B and the flow control valve 40, and the flow rate of oil reaching the oil tank 50 is limited by the meter-out throttle 44, and a portion of the oil that has passed through the flow control valve 40 is regenerated in the rod chamber 1b of the hydraulic cylinder 1 via the check valve 46, the regeneration passage 63h (regeneration-side fixed throttle 47), and the second rod oil passage 12B. Therefore, by adjusting the opening area of ​​the meter-out passage 63f in the flow control valve 40, it is possible to control the speed at which the hydraulic cylinder 1 retracts against the weight of the boom 3, arm 6, and bucket 7.

[0025] During this time, the flow control valve 40 described above allows oil to flow through the radial meter-out passage 63f provided in the spool 62. Therefore, the influence of the flow force generated when the oil from the second bottom oil passage 11B flows into the main passage 63 of the spool 62 can be reduced, and the opening area of ​​the meter-out passage 63f can be precisely adjusted. Moreover, since the meter-out region 63b for forming the meter-out passage 63f has a large inner diameter, it is possible to form a large number of meter-out passages 63f without them interfering with each other. In addition, since the meter-out region 63b is the only part of the spool 62 with a large inner diameter, there is no risk of problems such as bending even when a large hydraulic pressure is applied. As a result, the flow rate of oil passing through the flow control valve 40 can be precisely and finely controlled, making it possible to improve the operability of the boom 3 in the work machine.

[0026] Incidentally, when oil flows from the second bottom oil passage 11B into the main passage 63 of the spool 62, the pressure decreases, causing bubbles to form in the oil. When these bubbles collapse in the meter-out passage 63f, which is blocked by the land portion 60a of the valve body 60, they can cause erosion in the land portion 60a, raising concerns about affecting the sealing performance between the spool 62 and the valve body 60. However, with the flow control valve 40 described above, a tapered region 63c is provided between the meter-out region 63b and the drain region 63d such that the inner diameter gradually decreases, allowing the oil to flow smoothly downstream in the main passage 63 without reversing. Therefore, bubbles formed in the oil in the meter-out region 63b move to the tapered region 63c and the drain region 63d and are discharged to the outside from the drain passage 63g, preventing them from accumulating in the meter-out region 63b or the meter-out passage 63f. This prevents erosion from occurring in the land portion 60a of the valve body 60, and eliminates the risk of impaired sealing between the spool 62 and the valve body 60.

[0027] In the embodiments described above, a hydraulic cylinder for operating the boom of a work machine is used as an example, but the present invention is not limited to this. In this case, the first port does not need to be a meter-out port, nor does the second port need to be a drain port. Furthermore, although a tapered section in which the inner diameter decreases at a constant rate is shown as the third region, the rate at which the inner diameter decreases from the first region to the second region changes, and the tapered section may be curved in a convex shape or a concave shape. [Explanation of symbols]

[0028] 1. Hydraulic cylinder 1a Bottom chamber 11B Second bottom oil channel 40 Flow control valve 41 Meter Out Port 42 Drain port 50 oil tanks 51 Tank oil passage 60 Valve body 62 Spool 63 Main passage section 63b Meter output area 63c tapered region 63d Drain area 63f Meter Out Passage 63g Drain passage section

Claims

1. A valve body having a first port and a second port that are independent of each other, The valve body is equipped with a spool that is movably disposed along its axis, The spool is provided with a main passage portion located at the axial center, a first passage portion located between the main passage portion and the outer circumferential surface and capable of communicating with the first port, and a second passage portion located between the main passage portion and the outer circumferential surface and capable of communicating with the second port. A hydraulic valve that controls the flow rate of oil from the first port to the second port via the main passage by changing the opening area of ​​the first passage relative to the first port as the spool moves, The main passage portion of the spool has a first region where the first passage portion is provided, a second region where the second passage portion is provided, and a third region that connects the first region and the second region, wherein the inner diameter of the first region is formed to be larger than that of the second region, and the third region is configured in a tapered shape in which the inner diameter gradually decreases toward the second region.

2. The hydraulic valve according to claim 1, characterized in that the third region has an inner diameter that decreases at a constant rate from the first region to the second region.

3. The hydraulic valve according to claim 2, characterized in that the inclination angle of the third region is in the range of 15° to 30°.

4. A hydraulic circuit characterized in that a meter-out oil passage communicating with the bottom chamber of a hydraulic cylinder is connected to the first port of a hydraulic valve according to any one of claims 1 to 3, and a tank oil passage communicating with an oil tank is connected to the second port.

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