GB2554244A

GB2554244A - Flow control valve

Info

Publication number: GB2554244A
Application number: GB1717277.6A
Authority: GB
Inventors: Isogai Hiroki
Original assignee: KYB Corp
Current assignee: KYB Corp
Priority date: 2015-04-24
Filing date: 2016-04-08
Publication date: 2018-03-28
Anticipated expiration: 2036-04-08
Also published as: KR20170130575A; GB201717277D0; JP2016205549A; JP6423754B2; CN107532617B; WO2016171015A1; GB2554244B; CN107532617A

Abstract

A flow control valve (50) has, in sequence from the opening side of a housing hole (51), a tank port (52), an actuator discharge port (53), an internal pilot port (54), and an in-block supply passage. The distance (L1) between the in-block supply passage and the internal pilot port (54) measured along the axis of the housing hole (51) is greater than the distance (L2) between the internal pilot port (54) and the actuator discharge port (53) measured along the axis of the housing hole (51).

Description

(56) Documents Cited:

US 5862831 A (58) Field of Search:

INT CLF15B, F16K

F15B 11/00 (2006.01) F16K 27/04 (2006.01) (86) International Application Data:

PCT/JP2016/061590 Ja 08.04.2016 (87) International Publication Data:

W02016/171015 Ja 27.10.2016 (71) Applicant(s):

KYB Corporation World Trade Center Bldg, 4-1, Hamamatsu-cho-2-chome, Minato-Ku, Tokyo 105-6111, Japan (72) Inventor(s):

Hiroki Isogai (74) Agent and/or Address for Service:

Mewburn Ellis LLP

City Tower, 40 Basinghall Street, LONDON, Greater London, EC2V 5DE, United Kingdom (54) Title of the Invention: Flow control valve Abstract Title: Flow control valve (57) A flow control valve (50) has, in sequence from the opening side of a housing hole (51), a tank port (52), an actuator discharge port (53), an internal pilot port (54), and an in-block supply passage. The distance (L1) between the in-block supply passage and the internal pilot port (54) measured along the axis of the housing hole (51) is greater than the distance (L2) between the internal pilot port (54) and the actuator discharge port (53) measured along the axis of the housing hole (51).

1/5

100

FIG.1

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FIG.2

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FIG.3

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100

FIG.4

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FIG.5

- 1 DESCRIPTION

FLOW CONTROL VALVE

TECHNICAL FIELD [0001] The present invention relates to a flow control valve.

BACKGROUND ART [0002] JP2009-41616A discloses an invention of a control device including: a first circuit system connected to a first pump, being provided with a plurality of switching valves; and a second circuit system connected to a second pump, being provided with a plurality of switching valves. In the control device disclosed in JP2009-41616A, a switching valve is provided, which switching valve includes in the first circuit system a recycling function to recycle return fluid from a specific actuator to a supplying side of that specific actuator. Furthermore, this switching valve provides a recycling throttle in a passage serving as a returning side when the switching valve is switched to a recycling position, and is configured to recycle the return fluid with a pressure of an amount of pressure lost when the fluid passes this recycling throttle.

SUMMARY OF INVENTION [0003] In the control device of JP2009-41616A, the recycling throttle of the passage serving as the returning side is configured as a fixed throttle, so hence a recycling flow rate could not be adjusted. Therefore, there exists a flow control valve of a variable recycling throttle, to allow for adjusting the recycling flow rate. For such a flow control valve, there exists an external pilot type that uses a signal supplied externally as a pilot signal to control the flow rate, and an internal pilot type that uses a supplying pressure supplied from a pump to a switching valve as the pilot signal to control the flow rate. Furthermore, in

- 2 manufacturing the flow control valve, there is also a demand of being able to use a common valve block for the external pilot type and the internal pilot type. [0004] The present invention is accomplished in view of the above problems, and an object thereof is to provide a flow control valve having a valve block that can be used commonly between the internal pilot type and the external pilot type.

[0005] the fluid pressure control device includes: a control valve connected to the pump, the control valve being configured to control supplying and discharging of working fluid to one and another pressure chambers of the actuator, the control valve having a recycling passage for recycling working fluid discharged from the one pressure chamber to the another pressure chamber; an intermediate passage configured to return the working fluid supplied from the pump when the control valve is in an intermediate position; a supplying passage branching from the intermediate passage, the supplying passage being configured to supply working fluid to the control valve; a first tank passage provided between the control valve and the tank, the first tank passage being configured to discharge working fluid from the one pressure chamber of the actuator to the tank; a second tank passage provided between the control valve and the tank, the second tank passage being configured to discharge working fluid from the another pressure chamber of the actuator to the tank; and the flow control valve provided in the first tank passage, the flow control valve being configured to control a flow rate of working fluid passing through the first tank passage in accordance with a pilot pressure, wherein the flow control valve includes: a valve block having a bottomed cylindrical housing hole formed therein; and a valve body inserted into the housing hole, the valve block is formed with, from an opening portion side of the housing hole in a manner intersecting with the housing hole, a tank port provided downstream of the valve body in the first tank passage and communicating

- 3 with the tank, an actuator discharging port provided upstream of the valve body in the first tank passage and communicating with the control valve, and an internal pilot port communicating with the supplying passage, the valve block is further formed with an in-block supplying passage configured to receive working fluid discharged from the pump, the in-block supplying passage is formed at a position where at least one part thereof is on an axis of the housing hole and is away from the bottom portion of the housing hole on an opposite side of the opening portion, a distance between the in-block supplying passage and the internal pilot port along the axis of the housing hole is greater than a distance between the internal pilot port and the actuator discharging port along the axis of the housing hole.

BRIEF DESCRIPTION OF DRAWINGS [0006] Fig. 1 is a circuit diagram showing a fluid pressure control device including a flow control valve of an internal pilot type according to an embodiment of the present invention.

Fig. 2 is a view enlarging a portion of a fluid pressure control device including a flow control valve according to an embodiment of the present invention.

Fig. 3 is a structural sectional view of a flow control valve of an internal pilot type according to an embodiment of the present invention.

Fig. 4 is a circuit diagram showing a fluid pressure control device including a flow control valve of an external pilot type according to an embodiment of the present invention.

Fig. 5 is a structural sectional view of a flow control valve of an external pilot type according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

- 4 [0007] Described below with reference to the drawings is a flow control valve 50 according to an embodiment of the present invention.

[0008] First described with reference to Fig. 1 is a fluid pressure control device 100 to which the flow control valve 50 in the present embodiment is applied.

[0009] The fluid pressure control device 100 is used in work machines such as a power shovel. In this embodiment, although explanation will be provided for a case in which the work machine is a power shovel, the fluid pressure control device 100 is also applicable to other work machines such as a wheel loader. Moreover, in the fluid pressure control device 100, although working oil is used as the working fluid, other fluids such as working water may be used as the working fluid.

[0010] As shown in Fig. 1, the fluid pressure control device 100 includes a first circuit system 10 connected to a first pump Pl and being supplied with working oil from the first pump Pl, and a second circuit system 20 connected to a second pump P2 and being supplied with working oil from the second pump P2.

[0011] The first circuit system 10 includes: a first intermediate passage 11 that guides the working oil supplied from the first pump Pl to a tank T; a plurality of control valves 121 to 125 that are connected to the first intermediate passage 11 in series; and a first parallel passage 13 branching from the first intermediate passage 11 at a position upstream of the control valves 121 to 125. The control valves 121 to 125 are connected in series by the first intermediate passage 11, and are connected in parallel by the first parallel passage 13.

[0012] The working oil discharged from the first pump Pl is guided to, in order from the upstream side, a first traveling control valve 121, an auxiliary control valve 122, a revolving control valve 123, a first boom control valve 124, and a first arm control valve 125. The first traveling control valve 121 controls the supplying and discharging of the working oil to a traveling motor provided on the left side of the vehicle body of a power shovel (not illustrated). The auxiliary control valve 122 controls the supplying and discharging of the working oil to an actuator that drives an attachment such as a breaker or crusher that is attached instead of the bucket. The revolving control valve 123 controls the supplying and discharging of the working oil to a revolving motor that revolves a revolving body disposed on an upper portion of the vehicle body. The first boom control valve 124 controls the supplying and discharging of the working oil to an actuator that drives the boom. The first arm control valve 125 controls the supplying and discharging of the working oil to an actuator that drives the arm.

[0013] In the first circuit system 10, when all the control valves 121 to 125 are in an intermediate position, the working oil supplied from the first pump Pl is returned to the tank T by the first intermediate passage 11. On the other hand, when at least one of the control valves 121 to 125 is in a working position, the connection between the first pump Pl and the tank T in the first intermediate passage 11 is disconnected.

[0014] Moreover, in the first circuit system 10, even when one of the control valves 121 to 124 is switched to the working position and the connection between the first pump Pl and the tank T in the first intermediate passage 11 is disconnected, the working oil supplied from the first pump Pl can be supplied to the control valves 122 to 125 via the first parallel passage 13. [0015] The fluid pressure control device 100 stacks a plurality of valve blocks and tightens these together by sandwiching them with a bolt or like item, to form its main body. The fluid pressure control device 100 may be formed of one valve block.

[0016] The first circuit system 10 further includes an intermediate cut

- 6 valve 40 that is provided downstream of the control valves 121 to 125 in the first intermediate passage 11 and which allows or prohibits communication between the first intermediate passage 11 and the tank T. The intermediate cut valve 40 communicates the connection of the first intermediate passage 11 with the tank T when at a G position in Fig. 1 (normal position), and disconnects the connection of the first intermediate passage 11 with the tank T when at an H position (disconnecting position).

[0017] Next, the specific structure of the intermediate cut valve 40 is described with reference to Fig. 3. Fig. 3 is a sectional view showing a cross section when the intermediate cut valve 40 is at the G position (normal position).

[0018] As shown in Fig. 3, the intermediate cut valve 40 includes: a valve block 60 having a bottomed cylindrical housing hole 61; a spool 41 as a valve body, being housed inside the housing hole 61 to disconnect or communicate the connection of the first intermediate passage 11 with the tank T; a drain chamber 48 defined between one end of the spool 41 and a bottom portion of the housing hole 61 and communicating with the tank T; a pilot pressure chamber 49 provided on the other end of the spool 41 and formed by the valve block 60 and a cap member 43; and a return spring 44 provided within the pilot pressure chamber 49 to energize the spool 41 in a direction that the first intermediate passage 11 communicates with the tank T (left direction in Fig. 2) The cap member 43 is provided with a pilot port 42 for supplying and discharging pilot pressure to the pilot pressure chamber 49.

[0019] The spool 41 includes a first land portion 45 and a second land portion 46 that move slidably along an inner circumferential surface of the housing hole 61, and an annular groove 47 formed between the first land portion 45 and the second land portion 46.

[0020] Formed in the valve block 60 are: an intermediate passage portion

- 7 66 that penetrates through the valve block 60 in a direction orthogonal to an axis of the housing hole 61 and communicates with a part downstream of the first arm control valve 125; an inlet port portion 62 formed to the housing hole 61 so as to surround the spool 41 and communicating with the intermediate passage portion 66; and an outlet port portion 63 formed to the housing hole so as to surround the spool 41 and communicating with the tank T. A flow passage from the intermediate passage portion 66 within the valve block 60, through the inlet port portion 62 and to the outlet port portion 63, constitutes one part of the first intermediate passage 11. The flow passage from the intermediate passage portion 66 to the outlet port portion 63 through the inlet port portion 62 corresponds to an in-block supplying passage.

[0021] Next describes operations of the intermediate cut valve 40.

[0022] The intermediate cut valve 40, in a state in which no working oil within the pilot pressure chamber 49 is supplied, has the spool 41 in a state as shown in Fig. 3, that is to say, positioned at the G position in Fig. 1 (normal position). In this state, the inlet port portion 62 communicates with the outlet port portion 63 via the annular groove 47 formed on the spool 41. Accordingly, the working oil flowing into the inlet port portion 62 from the intermediate passage portion 66 that communicates with a part downstream of the first arm control valve 125 in the first intermediate passage 11 is returned into the tank T via the annular groove 47 and the outlet port portion 63. That is to say, by switching the intermediate cut valve 40 to the G position (normal position), the first intermediate passage 11 communicates with the tank T.

[0023] When the working oil of the pilot pressure chamber 49 is supplied from this state, the spool 41 moves towards the right side in Fig. 3 against the energizing force by the return spring 44, due to the pressure of the working oil supplied to the pilot pressure chamber 49. This causes the inlet port portion and the outlet port portion 63 to be disconnected by the first land portion

- 8 45 of the spool 41. That is to say, the intermediate cut valve 40 switches to the H position (disconnecting position) of Fig. 1. Accordingly, the working oil flowing into the inlet port portion 62 from the intermediate passage portion 66 that communicates with a part downstream of the first arm control valve 125 in the first intermediate passage 11 is prevented from flowing into the outlet port portion 63, by the first land portion 45. That is to say, by switching the intermediate cut valve 40 to the H position (disconnecting position), the connection of the first intermediate passage 11 with the tank T is disconnected.

[0024] Next described is the first arm control valve 125, with reference to Fig. 1 and Fig. 2.

[0025] As shown in Fig. 1 and Fig. 2, the first arm control valve 125 is connected to: the first intermediate passage 11; a supplying passage 12 that branches from the first intermediate passage 11 and supplies working oil for driving an arm cylinder 90; a first cylinder passage 91a communicating with a pressure chamber 90a on a high load side of the arm cylinder 90; a second cylinder passage 91b communicating with a pressure chamber 90b on a low load side of the arm cylinder 90; a first tank passage 14 to discharge the working oil of the pressure chamber 90a to the tank T; and a second tank passage 15 to discharge the working oil of the pressure chamber 90b to the tank T. The first parallel downstream passage 13b joins to the supplying passage 12. Check valves 17 are each provided at upstream sides of a joining portion on the supplying passage 12 and the first parallel passage 13, to prevent a reverse flow of the working oil. In the first tank passage 14, a flow control valve 50 is provided to control a flow rate of the working oil passing through the first tank passage 14, in accordance with the pilot pressure. [0026] The first arm control valve 125 is switched between three positions, an intermediate position A, a high load working position B shown on the right

- 9 sides in Fig. 1 and Fig. 2, and a low load working position C shown on the left sides in Fig. 1 and Fig. 2. The positions A, B, and C of the first arm control valve 125 are switched in accordance with a pilot pressure supplied to the pilot chambers 125a and 125b provided on either end of the first arm control valve 125. When the pilot pressure is acting on neither of the pilot chambers 125a or 125b, the first arm control valve 125 becomes in the intermediate position A due to the energizing force of springs 125c provided on either side of the first arm control valve 125. When the pilot pressure is supplied to the pilot chamber 125b, the first arm control valve 125 switches to the high load working position B, and when the pilot pressure is supplied to the pilot chamber 125a, the first arm control valve 125 switches to the low load working position C.

[0027] In the intermediate position A, the first intermediate passage 11 is connected to the tank T, and other passages are disconnected. This causes no working oil to be supplied to or discharged from the pressure chambers 90a and 90b of the arm cylinder 90, and the arm cylinder 90 is kept at that position.

[0028] In the high load working position B, the first intermediate passage 11 is disconnected, the supplying passage 12 is connected to the first cylinder passage 91a, and the second cylinder passage 91b is connected to the second tank passage 15. This causes the working oil discharged from the first pump Pl to be supplied to the pressure chamber 90a from the first intermediate passage 11 and the first parallel downstream passage 13b via the supplying passage 12 and the first cylinder passage 91a. Moreover, the working oil within the pressure chamber 90b is discharged to the tank T via the second cylinder passage 91b and the second tank passage 15.

[0029] In the low load position C, the first intermediate passage 11 is disconnected, the supplying passage 12 is connected to the second cylinder

- 10 passage 91b, and the first cylinder passage 91a is connected to the first tank passage 14. This causes the working oil discharged from the first pump Pl to be supplied to the pressure chamber 90b from the first intermediate passage 11 and the first parallel passage 13 via the supplying passage 12 and the second cylinder passage 91b. Moreover, the working oil within the pressure chamber 90a is discharged to the tank T via the first cylinder passage 91a and the first tank passage 14. At this time, the flow rate of the working oil discharged to the tank T via the first tank passage 14 is controlled by the flow control valve 50.

[0030] Moreover, in the low load position C, formed in the first arm control valve 125 are: a first internal passage 126 that connects the first cylinder passage 91a with the first tank passage 14; a second internal passage 127 that connects the supplying passage 12 with the second cylinder passage 91b; and a recycling passage 128 that connects the first internal passage 126 with the second internal passage 127 (see Fig. 2). The recycling passage 128 is provided with a check valve 129 that allows just a flow from the first internal passage 126 to the second internal passage 127. Accordingly, it is possible to recycle the working oil discharged from the pressure chamber 90a to the pressure chamber 90b via the recycling passage 128. The first internal passage 126 is provided with a throttle 130 that controls the flow rate of the working oil discharged from the pressure chamber 90a.

[0031] Next, the specific structure of the flow control valve 50 is described with reference to Fig. 1, Fig. 2, and Fig. 3.

[0032] As described above, the flow control valve 50 is provided in the first tank passage 14. The flow control valve 50 shown in Fig. 1, Fig. 2, and Fig. 3 is a flow control valve of an internal pilot type in which the working oil supplied via a pilot passage 16 branched from the supplying passage 12 is controlled as the pilot pressure.

- 11 [0033] As shown in Fig. 3, the flow control valve 50 includes: a valve block 60 having a bottomed cylindrical housing hole 51 formed therein; a sleeve 70 to be inserted into the housing hole 51; and a spool 80 as a valve body inserted into the housing hole 51 via the sleeve 70. The intermediate cut valve 40 and the flow control valve 50 uses a common valve block 60, however they may include separate valve blocks each.

[0034] Formed in the valve block 60 are, from an opening side of the housing hole 51 in a manner so as to intersect with the housing hole 51: a tank port 52 provided downstream of the spool 80 in the first tank passage 14 and communicating with the tank T; an actuator discharging port 53 provided upstream of the spool 80 in the first tank passage 14 and communicating with the first arm control valve 125; and an internal pilot port 54 communicating with the supplying passage 12 via the pilot passage 16.

[0035] The valve block 60 has a space 65 formed along a flow passage that connects the intermediate passage portion 66 with the inlet port portion 62. The space 65 is formed along the axis of the housing hole 51 at a position away from the bottom portion of the housing hole 51 in an opposite direction to the opening. Alternatively, no space 65 may be provided, and an intermediate passage portion 66 may be formed instead, at the position where the space 65 is provided.

[0036] The sleeve 70 is formed in a hollow cylindrical shape. Formed in the sleeve 70 are: a plurality of first penetrating holes 71 that communicate with the tank port 52; a plurality of second penetrating holes 72 that communicate with the actuator discharging port 53; and a plurality of slits 73 formed on an end plane that comes into contact with the housing hole 51. The sleeve 70 is housed in the housing hole 51, and is fixed as though being pressed against the bottom surface of the housing hole 51 by a plug 77 screwed onto the valve block 60.

- 12 [0037] The spool 80 includes: a first land portion 81 and a second land portion 82 that move slidably along an inner circumferential surface of the sleeve 70; an annular groove 83 formed between the first land portion 81 and the second land portion 83; and a piston 84 provided to come into contact with an end plane on an opposite side of the annular groove 83 of the second land portion 82. The piston 84 may be formed integrally to the spool 80.

[0038] On the bottom portion of the housing hole 51, an internal pilot pressure chamber 55 is defined by the inner circumferential surface of the sleeve 70 and an end plane of the piston 84. The internal pilot pressure chamber 55 communicates with the internal pilot port 54 via the slit 73. [0039] Inside the plug 77, a spring housing space 74 is formed, in which a spool spring 75 is housed, which spool spring energizes the spool 80 towards the bottom plane side of the housing hole 51. The spring housing space 74 communicates with the tank port 52 via a through hole 76.

[0040] Next described is the second circuit system 20, with reference to Fig.

1.

[0041] The second circuit system 20 includes: a second intermediate passage 21 that guides the working oil supplied from the second pump P2 to a tank T; a plurality of control valves 221 to 224 that are connected to the second intermediate passage 21 in series; and a second parallel passage 23 branching from the second intermediate passage 21 on a side upstream of the control valves 221 to 224. The control valves 221 to 224 are connected in series by the second intermediate passage 21, and are connected in parallel by the second parallel passage 23.

[0042] The working oil discharged from the second pump P2 is guided to, in order from the upstream side, a second traveling control valve 221, a bucket control valve 222, a second boom control valve 223, and a second arm control valve 224. The second traveling control valve 221 controls the supplying and

- 13 discharging of the working oil to a traveling motor provided on the right side of the vehicle body of a power shovel (not illustrated). The bucket control valve 222 controls the supplying and discharging of the working oil to an actuator that drives the bucket. The second boom control valve 223 controls the supplying and discharging of the working oil to an actuator that drives the boom. The second arm control valve 224 controls the supplying and discharging of the working oil to an actuator that drives the arm. The control valves 221 to 224 correspond to the second control valves.

[0043] In the second circuit system 20, when all the control valves 221 to 224 are in the intermediate positions, the working oil supplied from the second pump P2 is returned to the tank T by the second intermediate passage 21. On the other hand, when at least one of the control valves 221 to 224 is in a working position, the connection of the second pump P2 with the tank T in the second intermediate passage 21 is disconnected.

[0044] Moreover, in the second circuit system 20, even when any one of the control valves 221 to 223 is switched to the working position and the connection of the second pump P2 with the tank T in the second intermediate passage 21 is disconnected, the working oil supplied from the second pump P2 can be supplied to the control valves 222 to 224 via the second parallel passage 23.

[0045] The second circuit system 20 further includes an intermediate cut valve 24 that is provided downstream of the second arm control valve 224 in the second intermediate passage 21 and which allows or prohibits communication between the second intermediate passage 21 and the tank T. A structure identical to that of the intermediate cut valve 40 is used for the intermediate cut valve 24.

[0046] The second circuit system 20 further includes a branching passage 29 downstream of the second arm control valve 224 in the second intermediate

- 14 passage 21 and communicating with a part upstream of the intermediate cut valve 24, and capable of supplying the working oil discharged from the second pump P2.

[0047] The second circuit system 20 further includes a linear travel control valve 25 connected at a part downstream of a branching point with the second parallel passage 23 in the second intermediate passage 21 and upstream of the second traveling control valve 221. The first parallel passage 13 is connected to the linear travel control valve 25. The first parallel passage 13 has: a first parallel upstream passage 13a that connects the first pump Pl with the linear travel control valve 25; and a first parallel downstream passage 13b that connects the linear travel control valve 25 with the control valves 122 to 125. [0048] The linear travel control valve 25 switches between three positions, of a normal position D shown in the center in Fig. 1, a linear travel position E shown on the left side in Fig. 1, and a joining position F shown on the right side in Fig. 1. The positions D, E, F of the linear travel control valve 25 are switched in accordance with a pilot pressure supplied to the pilot chambers 25a and 25b provided on either end of the linear travel control valve 25. When the pilot pressure is acting on neither of the pilot chambers 25a or 25b, the linear travel control valve 25 becomes in the normal position D due to the energizing force of springs 25c provided on either side of the linear travel control valve 25. When the pilot pressure is supplied to the pilot chamber 25a, the linear travel control valve 25 switches to the linear travel position E, and when the pilot pressure is supplied to the pilot chamber 25b, the linear travel control valve 25 switches to the joining position F.

[0049] In the normal position D, the first parallel upstream passage 13a of the first parallel passage 13 is connected to the first parallel downstream passage 13b of the first parallel passage 13, and the second intermediate passage 21 is connected to the second pump P2. This causes the working oil

- 15 discharged from the first pump Pl to be supplied to the control valves 121 to 125 via the first intermediate passage 11 and the first parallel passage 13. Moreover, the working oil discharged from the second pump P2 is supplied to the control valves 221 to 224 via the second intermediate passage 21 and the second parallel passage 23. That is to say, when just the traveling motor is to be operated, the working oil discharged from the first pump Pl is supplied to the first traveling control valve 121, and the working oil discharged from the second pump P2 is supplied to the second traveling control valve 221.

[0050] In the linear travel position E, the first parallel upstream passage 13a of the first parallel passage 13 is connected to the second intermediate passage 21 downstream of the linear travel control valve 25, and the first parallel downstream passage 13b is connected to the second pump P2. That is to say, when the traveling motor and an actuator other than the traveling motor are operated simultaneously, the working oil discharged from the first pump Pl is supplied to the first traveling control valve 121 and the second traveling control valve 221, and the working oil discharged from the second pump P2 is supplied to the other control valves 122 to 125 and other control valves 222 to 224. Accordingly, in the linear travel position E, even if the traveling motor and actuators other than the traveling motor are operated simultaneously, the circuit of the traveling motor and the circuit of the actuator other than the traveling motor are independent from each other, so the linear traveling ability of the vehicle body will be secured.

[0051] In the joining position F of the linear travel control valve 25, the second intermediate passage 21 upstream of the linear travel control valve 25 is connected to the second intermediate passage 21 downstream of the linear travel control valve 25, and the first parallel upstream passage 13a is connected to the second intermediate passage 21 via a joining passage 26 formed inside the linear travel control valve 25. This causes the working oil of

- 16 the first pump Pl to join with the working oil of the second pump P2 and be supplied to the second control valve, and allows for supplying more working oil to the actuator connected to the second control valve.

[0052] The joining passage 26 formed inside the linear travel control valve 25 is provided with, from its upstream side in this order, a check valve 27 that allows just a flow from the first parallel upstream passage 13a to the second intermediate passage 21, and a throttle 28 that restricts the flow of the working oil within the joining passage 26. This allows for preventing the working oil of the second pump P2 from flowing to the first parallel upstream passage 13a side, and allows for joining of the working oil into the second intermediate passage 21 in a state that the amount of the working oil joining from the first pump Pl to that from the second pump P2 is adjusted by restricting the working oil of the first parallel upstream passage 13a in a complex operation of the first control valve with the second control valve. [0053] Here described is a case in which the working oil discharged from the first pump Pl is joined into the second intermediate passage 21 while driving the cylinder 22 that drives the bucket.

[0054] The working oil is supplied to: a pilot pressure chamber of the bucket control valve 222 that controls the supplying and discharging of the working oil to the cylinder 22 which drives the bucket; the pilot pressure chamber 49 of the intermediate cut valve 40; and the pilot chamber 25b of the linear travel control valve 25. Accordingly, when the bucket control valve 222 is operated, the second intermediate passage 21 and the second parallel passage 23 are supplied with, in addition to the working oil discharged from the second pump P2, the working oil discharged from the first pump Pl supplied via the joining passage 26 of the linear travel control valve 25. Accordingly, the cylinder 22 is driven in a state in which the working oil discharged from the first pump Pl is joined with the working oil discharged

- 17 from the second pump P2. Therefore, the cylinder 22 can be driven at a high speed.

[0055] Next, functions of the flow control valve 50 is described with reference to Fig. 2 and Fig. 3. Fig. 3 is a view showing a state in which the pilot pressure acting on the internal pilot pressure chamber 55 is low.

[0056] The flow control valve 50, in a case in which the first arm control valve 125 is switched to the low load position C, adjusts the flow rate of the working oil returned to the tank T from the pressure chamber 90a on the high load side via the first tank passage 14. More specifically, when the pilot pressure is supplied to the pilot chamber 125a of the first arm control valve 125, the first arm control valve 125 switches to the low load position C. This causes the working oil within the pressure chamber 90a on the high load side of the arm cylinder 90 to flow into an actuator discharging port 53 of the flow control valve 50, via the first cylinder passage 91a, the first internal passage 126 and the first tank passage 14. The working oil flown into the actuator discharging port 53 flows from the second through hole 72 to the annular groove 83, and flows out to the tank port 52 through the first through hole 71. [0057] When the pilot pressure acting on the internal pilot pressure chamber 55 from the supplying passage 12 via the pilot passage 16 is low, the spool 80 is energized by the spool spring 75 towards the bottom side of the housing hole 51. This causes, as shown in Fig. 3, the flow passage area to become in a narrowed state by the first land portion 81 of the spool 80 that overlaps with the first through hole 71. In this state, the flow rate of the working oil that can pass through the first tank passage 14 is low. Therefore, most of the working oil discharged from the pressure chamber 90a is recycled to the pressure chamber 90b via the recycling passage 128.

[0058] When the pilot pressure acting on the internal pilot pressure chamber 55 increases from this state, the spool 80 moves towards the plug 77

- 18 side, against the energizing force of the spool spring 75. This causes the overlap of the first through hole 71 with the first land portion 81 to decrease, and the flow passage area of the first through hole 71 increases. Accordingly, the flow rate of the working oil that can pass through the first tank passage 14 increases, and the flow rate of the working oil that is recycled from the pressure chamber 90a to the pressure chamber 90b via the recycling passage 128 decreases. When the pilot pressure acting on the internal pilot pressure chamber 55 further increases, the spool 80 moves further towards the plug 77 side. This causes the flow rate of the working oil that can pass through the first tank passage 14 to further increase. Accordingly, the working oil is not recycled from the pressure chamber 90a to the pressure chamber 90b via the recycling passage 128, but the working oil within the pressure chamber 90a is discharged to the tank T by its entire amount.

[0059] As such, the flow control valve 50 adjusts the flow rate recycled from the pressure chamber 90a to the pressure chamber 90b via the recycling passage 128 by adjusting the flow rate of the working oil passing through the first tank passage 14 in accordance with the pilot pressure acting on the internal pilot pressure chamber 55.

[0060] In a fluid pressure control device 100 including the flow control valve 50 of an inner pilot type configured as described above, when the pressure of the working oil within the supplying passage 12 decreases due to a complex operation of the cylinder or like cause, that is to say, when the pilot pressure decreases, the flow control valve 50 can recycle the working oil within the pressure chamber 90a to the pressure chamber 90b by throttling the first tank passage 14. On the other hand, when the pressure of the working oil within the supplying passage 12 is high (does not decrease) such as a sole operation of the arm cylinder 90, that is say, when the pilot pressure is high, the working oil within the pressure chamber 90a is not recycled to the

- 19 pressure chamber 90b and is discharged to the tank T, by the flow control valve 50 releasing the first tank passage 14.

[0061] Next described is a flow control valve 150 of an external pilot type, with reference to Fig. 4 and Fig. 5.

[0062] The flow control valve 150 shown in Fig. 4 differs from the fluid pressure control device 100 shown in Fig 1 in a point that the pilot pressure is supplied externally of the fluid pressure control device.

[0063] With reference to Fig. 5, described is a specific configuration of the flow control valve 150. Regarding the flow control valve 150, configurations identical to the flow control valve 50 are provided with reference signs of the same number in the drawings, and their descriptions are omitted.

[0064] The flow control valve 150 includes: a valve block 160 having a bottomed cylindrical housing hole 151 formed therein; a spool 180 as a valve body to be inserted into the housing hole 151; a drain port 156 defined between one end of the spool 180 and a bottom portion of the housing hole 151, and communicating with the tank T; an external pilot pressure chamber 155 provided on a side of the other end of the spool 180 and defined by the valve block 160 and a cap member 173; and a spool spring 175 provided within the external pilot pressure chamber 155 and energizing the spool 180 to a direction of the cap member 173 (left direction in Fig. 5). The cap member 173 is provided with a pilot port 174 for supplying and discharging the pilot pressure to the external pilot pressure chamber 155.

[0065] The valve block 160 of the flow control valve 150 shown in Fig. 5 and the valve block 60 of the flow control valve 50 shown in Fig. 3 are obtained by processing a valve block produced with a common mold. The housing hole 151 of the valve block 160 is deeper than the housing hole 51 in the valve block 60, and is processed to intersect with the drain port 156.

[0066] As described above, in the valve block 160, a drain port 156 is

- 20 provided at a position between the internal pilot port 54 and the space 65. Therefore, the valve block produced by a mold secures, in advance, a space that allows for providing the drain port 156 between the internal pilot port 54 and the space 65. More specifically, the ports are disposed so that a distance LI along an axis of the housing holes 51 and 151 between the space 65 and the internal pilot port 54 is greater than a distance L2 along the axis of the housing holes 51 and 151 between the internal pilot port 54 and the actuator discharging port 53.

[0067] The spool 180 includes: a first land portion 181 and second land portion 182 that move slidably along an inner circumferential plane of the housing hole 151 of the valve block 160; an annular groove 183 formed between the first land portion 181 and the second land portion 182; and a plurality of notches 184 provided on an end portion on the annular groove 183 side of the second land portion 182. The flow control valve 150 may provide a sleeve between the valve block 160 and the spool 180.

[0068] Next described are functions of the flow control valve 150, with reference to Fig. 4 and Fig. 5. Fig. 5 is a view showing a state in which the pilot pressure acting on the external pilot pressure chamber 155 is low.

[0069] The flow control valve 150, in a case in which the first arm control valve 125 is switched to the low load position C, adjusts the flow rate of the working oil returned to the tank T from the pressure chamber 90a on the high load side via the first tank passage 14. More specifically, when the pilot pressure is supplied to the pilot chamber 125a of the first arm control valve 125, the first arm control valve 125 switches to the low load position C. This causes the working oil within the pressure chamber 90a on the high load side of the arm cylinder 90 to flow into the actuator discharging port 53, via the first cylinder passage 91a, the first internal passage 126, and the first tank passage 14. The working oil flown into the actuator discharging port 53 flows out to

- 21 the tank port 52 through the notches 184. At this time, although the working oil acts on the internal pilot port 54 from the supplying passage 12 via the pilot passage 16, the internal pilot port 54 is constantly closed by the second land portion 182.

[0070] When the pilot pressure is low, the spool 180 is energized by the spool spring 175 towards the bottom side of the housing hole 151. This causes, as shown in Fig. 5, a flow area of the notches 184 of the second land portion 182 to become in a narrowed state. In this state, the flow rate of the working oil that can pass through the notch 184 is small. Therefore, most of the working oil discharged from the pressure chamber 90a is recycled to the pressure chamber 90b via the recycling passage 128.

[0071] When the pilot pressure acting on the external pilot pressure chamber 155 gradually increases from this state, the spool 180 moves towards the bottom side of the housing hole 151, against the energizing force of the spool spring 175. This causes the flow passage area of the notches 184 to be in an increased state. Accordingly, the flow rate of the working oil that can pass through the first tank passage 14 increases, and the flow rate of the working oil that is recycled from the pressure chamber 90a to the pressure chamber 90b via the recycling passage 128 decreases. When the pilot pressure acting on the external pilot pressure chamber 155 further increases, the spool 180 moves further towards the bottom side of the housing hole 151. This causes the flow rate of the working oil that can pass through the first tank passage 14 to further increase. Accordingly, the working oil is not recycled from the pressure chamber 90a to the pressure chamber 90b via the recycling passage 128, but the working oil within the pressure chamber 90a is discharged to the tank T by its entire amount.

[0072] As such, the flow control valve 150 can adjust the flow rate recycled from the pressure chamber 90a to the pressure chamber 90b via the recycling

- 22 passage 128 by adjusting the flow rate of the working oil passing through the first tank passage 14 in accordance with the pilot pressure acting on the external pilot pressure chamber 155.

[0073] According to the above embodiment, the following effects are achieved.

[0074] In the valve block 60 of the flow control valve 50, a distance LI along the axis of the housing hole 51 between the space 65 and the internal pilot port 54 is formed to be greater than a distance L2 along the axis of the housing hole 51 between the internal pilot port 54 and the actuator discharging port 53. This allows for securing a space to add a drain port 156 for using the flow control valve as an external pilot type. Accordingly, even if the valve block of the internal pilot type and the valve block of the external pilot type are made common, the valve block 60 of the internal pilot type can be used with the flow control valve 150 of the outer pilot type just by conducting a simple additional processing thereto. That is to say, according to the flow control valves 50 and 150, it is possible to make the valve blocks used in the flow control valves of the internal pilot type and the external pilot type common.

[0075] Moreover, in the flow control valve 50, the internal pilot port 54 is preferably provided at a position substantially middle between the tank port 52 and the space 65. Between the internal pilot port 54 and the tank port 52, the actuator discharging port 53 is provided. That is to say, between the internal pilot port 54 and the tank port 52, there is a space secured to provide the actuator discharging port 53. The distance LI between the internal pilot port 54 and the space 65 is formed substantially equal to a distance L3 between the internal pilot port 54 and the tank port 52; thus, a space for forming the drain port 156 is secured in advance, between the internal pilot port 54 and the space 65.

[0076] A description is made collectively for the configuration, functions,

- 23 and effects of the embodiment of the present invention configured as described above.

[0077] The fluid pressure control device 100 includes: a first arm control valve 125 connected to a first pump Pl, the first arm control valve being configured to control the supplying and discharging of working fluid to one and another pressure chambers 90a and 90b of an actuator (arm cylinder 90), the control valve having a recycling passage 128 for recycling working fluid discharged from the one pressure chamber 90a to the another pressure chamber 90b; an intermediate passage (first intermediate passage 11) configured to return the working fluid supplied from the first pump Pl to the tank T when the first arm control valve 125 is in an intermediate position; a supplying passage 12 that branches from the intermediate passage (first intermediate passage 11), the supplying passage 12 being configured to supply working oil to the first arm control valve 125; a first tank passage 14 provided between the first arm control valve 125 and the tank T, the first tank passage 14 being configured to discharge working oil from the one pressure chamber 90a of the actuator (arm cylinder 90) to the tank T; a second tank passage 15 provided between the first arm control valve 125 and the tank T, the second tank passage 15 being configured to discharge working oil from the another pressure chamber 90b of the actuator (arm cylinder 90) to the tank T; and flow control valves 50 and 150 provided in the first tank passage 14, the flow control valves 50 and 150 being configured to control flow rates of the working fluid passing through the first tank passage 14 in accordance with a pilot pressure, wherein the flow control valves 50 and 150 have: valve blocks 60 and 160 having bottomed cylindrical housing holes 51 and 151 formed therein, respectively; and valve bodies (spools 80 and 180) configured to be inserted into the housing holes 51 and 151, respectively, the valve blocks 60 and 160 are formed with, from an opening portion side of the housing holes 51 and 151

- 24 in a manner intersecting with the housing holes 51 and 151, a tank port 52 provided downstream of the valve bodies (spools 80 and 180) in the first tank passage 14 and communicating with the tank T, an actuator discharging port 53 provided upstream of the valve bodies (spools 80 and 180) in the first tank passage 14 and communicating with the first arm control valve 125, and an internal pilot port 54 communicating with the supplying passage 12, the valve blocks 60 and 160 is further formed with an in-block supplying passage (intermediate passage portion 66, space 65, inlet port portion 62, outlet port portion 63) to which the working oil discharged from the first pump Pl is supplied, the in-block supplying passage (intermediate passage portion 66, space 65, inlet port portion 62, outlet port portion 63) is formed at a position where at least one port thereof is on an axis of the housing holes 51 and 151 and is away from a bottom portion of the housing holes 51 and 151 on an opposite side of the opening portion, and a distance LI between the in-block supplying passage (intermediate passage portion 66, space 65, inlet port portion 62 and outlet port portion 63) and the internal pilot port 54 along the axis of the housing holes 51 and 151 is greater than a distance L2 between the internal pilot port 54 and the actuator discharging port 53 along the axis of the housing holes 51 and 151.

[0078] In this configuration, in the valve blocks 60 and 160 of the flow control valves 50 and 150, the distance LI between the in-block supplying passage (intermediate passage portion 66, space 65, inlet port portion 62, outlet port portion 63) and the internal pilot port 54 along the axis of the housing holes 51 and 151 is formed greater than the distance L2 between the internal pilot port 54 and the actuator discharging port 53 along the axis of the housing holes 51 and 151. This allows for securing a space to add a drain port for using the flow control valves 50 and 150 as an external pilot type. Accordingly, it is possible to make the valve blocks 60 and 160 used in the flow

- 25 control valves 50 and 150 of the internal pilot type and the external pilot type common.

[0079] Moreover, in the flow control valves 50 and 150, the internal pilot port 54 is provided substantially middle between the tank port 52 and the in-block supplying passage (space 65) along the axis of the housing holes 51 and 151.

[0080] Moreover, the flow control valve 50 is the pilot pressure is a pressure of working fluid supplied to the internal pilot port 54, an internal pilot pressure chamber 55 communicating with the internal pilot port 54 is formed between a bottom portion of the housing hole 51 and one end plane of the valve body (spool 80), and a flow rate of the working fluid passing through the first tank passage 14 is controlled by the valve body (spool 80) moving in accordance with the pilot pressure.

[0081] In this configuration, the flow control valve 50 can be used as an internal pilot type that is controlled by the working fluid supplied to the internal pilot port 54.

[0082] Moreover, the flow control valve 150 has, formed in the valve block 160, a drain port 156 facing one end plane of the valve body (spool 180), the drain port 156 formed between the in-block supplying passage (space 65) and the internal pilot port 54 along the axis of the housing hole 151, an external pilot pressure chamber 155 facing another end plane of the valve body (spool 180) is formed between the valve block 160 and a cap member 173 provided outside the valve block 160, the pilot pressure is a pressure of the working fluid supplied to the external pilot pressure chamber 155, and a flow rate of working fluid passing through the first tank passage 14 is controlled by the valve body (spool 180) moving in accordance with the pilot pressure.[0083]

In this configuration, the flow control valve 150 can be used as an external pilot type controlled by the working fluid supplied to the external pilot

- 26 pressure chamber 155.

[0084] Moreover, the internal pilot port 54 is constantly closed by the valve body (spool 180).

[0085] In this configuration, even if the internal pilot port 54 is present in the valve block 160, the internal pilot port 54 is constantly closed by the valve body (spool 180); thus, it is possible to use the valve block 60 of the inner pilot type as the flow control valve 150 of the outer pilot type, just by conducting a simple additional processing thereto.

[0086] Moreover, the in-block supplying passage is one part of the intermediate passage (first intermediate passage 11).

[0087] Embodiments of this invention were described above, but the above embodiments are merely examples of applications of this invention, and the technical scope of this invention is not limited to the specific constitutions of the above embodiments.

[0088] For example, at least one of the control valves 121 to 125 is provided.

The second circuit system 20 does not need to be provided in particular. Moreover, the in-block supplying passage may be one part of the first parallel passage 13.

[0089] This application claims priority based on Japanese Patent Application No.2015-89391 filed with the Japan Patent Office on April 24, 2015, the entire contents of which are incorporated into this specification.

Claims

1. A flow control valve used in a fluid pressure control device configured to control an actuator driven by working fluid supplied from a pump, the fluid pressure control device comprising:

a control valve connected to the pump, the control valve being configured to control supplying and discharging of working fluid to one and another pressure chambers of the actuator, the control valve having a recycling passage for recycling working fluid discharged from the one pressure chamber to the another pressure chamber;

an intermediate passage configured to return the working fluid supplied from the pump to a tank when the control valve is in an intermediate position;

a supplying passage branching from the intermediate passage, the supplying passage being configured to supply working fluid to the control valve;

a first tank passage provided between the control valve and the tank, the first tank passage being configured to discharge working fluid from the one pressure chamber of the actuator to the tank;

a second tank passage provided between the control valve and the tank, the second tank passage being configured to discharge working fluid from the another pressure chamber of the actuator to the tank; and the flow control valve provided in the first tank passage, the flow control valve being configured to control a flow rate of working fluid passing through the first tank passage in accordance with a pilot pressure, wherein the flow control valve includes:

a valve block having a bottomed cylindrical housing hole formed therein;

and

- 28 a valve body inserted into the housing hole, the valve block is formed with, from an opening portion side of the housing hole in a manner intersecting with the housing hole, a tank port provided downstream of the valve body in the first tank passage and communicating with the tank, an actuator discharging port provided upstream of the valve body in the first tank passage and communicating with the control valve, and an internal pilot port communicating with the supplying passage, the valve block is further formed with an in-block supplying passage to which the working oil discharged from the pump is supplied, the in-block supplying passage is formed at a position where at least one part thereof is on an axis of the housing hole and is away from the bottom portion of the housing hole on an opposite side of the opening portion, a distance between the in-block supplying passage and the internal pilot port along the axis of the housing hole is greater than a distance between the internal pilot port and the actuator discharging port along the axis of the housing hole.

2. The flow control valve according to claim 1, wherein the internal pilot port is provided substantially middle between the tank port and the in-block supplying passage along the axis of the housing hole.

3. The flow control valve according to claim 1 or 2, wherein the pilot pressure is a pressure of working fluid supplied to the internal pilot port, an internal pilot pressure chamber communicating with the internal pilot port is formed between a bottom portion of the housing hole and one end plane of the valve body, and

- 29 a flow rate of working fluid passing through the first tank passage is controlled by the valve body moving in accordance with the pilot pressure.

4. The flow control valve according to claim 1 or 2, wherein the valve block is further formed with a drain port facing one end plane of the valve body, the drain port being formed at a position between the in-block supplying passage and the internal pilot port along the axis of the housing hole, an external pilot pressure chamber facing another end plane of the valve body is formed between the valve block and a cap member provided outside the valve block, the pilot pressure is a pressure of working fluid supplied to the external pilot pressure chamber, and a flow rate of working fluid passing through the first tank passage is controlled by the valve body moving in accordance with the pilot pressure.

5. The flow control valve according to claim 4, wherein the internal pilot port is constantly closed by the valve body.

6. The flow control valve according to claim 1 or 2, wherein the in-block supplying passage is one part of the intermediate passage.