Fluid pressure control device

Abstract

This fluid pressure control device 100 is provided with: control valves 7, 10 that are driven by operating-oil guided to pilot chambers 7a, 11A; a neutral cut valve 20, the position of which is switched in accordance with the balance between the biasing force of a spring 21 and the pressure of the operating-oil acting from the side opposite the spring 21; a housing 30 in which the control valves 7, 10 and the neutral cut valve 20 are disposed; and a cap 40 provided with an electromagnetic proportional valve 50 that controls the pressure of the pilot chambers 7a, 11A and the operating-oil guided to the pilot chambers 7a, 11A. The cap 40 comprises: a drain channel 43 that guides the operating-oil discharged via the electromagnetic proportional valve 50 from the pilot chambers 7a, 11A of the control valves 7, 10; a drain chamber 23 that accommodates the spring 21 of the neutral cut valve 20; and a drain port 45 that discharges the operating-oil from the drain chamber 23. The drain channel 43 and the drain port 35 communicate with one another.

Description

Fluid Pressure Control Device

[0001] The present invention relates to a fluid pressure control device.

[0002] JP2020-133692A (see, for example, FIG. 5) discloses a multi-control valve unit in which an electromagnetic proportional valve that controls the pilot pressure of a control valve is attached to the cover of a housing that accommodates a spool of the control valve.

[0003] A fluid pressure control device may be provided with a second control valve other than a first control valve whose pilot pressure is controlled by an electromagnetic proportional valve. If the drain system for the working fluid is laid out without taking such a second control valve into consideration, a separate drain port will be provided for the working fluid discharged from the pilot chamber of the first control valve through the electromagnetic proportional valve, which could increase the number of drain ports and make the piping connections to the drain ports more complicated.

[0004] The present invention has been made in view of the above problems, and has an object to simplify the piping connection to the drain port.

[0005] According to one aspect of the present invention, there is provided a fluid pressure control device comprising: a first control valve driven by working fluid led to a pilot chamber; a second control valve whose position is switched depending on the balance between the biasing force of a biasing member and the pressure of the working fluid acting from the opposite side of the biasing member; a housing in which the first control valve and the second control valve are provided; and a cap attached to the housing in which a pilot chamber and an electromagnetic proportional valve that controls the pressure of the working fluid led to the pilot chamber are provided, wherein the cap has a drain passage that leads the working fluid discharged from the pilot chamber of the first control valve through the electromagnetic proportional valve, a drain chamber that accommodates the biasing member of the second control valve, and a drain port that discharges the working fluid from the drain chamber, and the drain passage and the drain port are connected to each other.

[0006] Fig. 1 is a diagram showing a fluid pressure control device according to an embodiment of the present invention. Fig. 2 is a diagram showing main parts of the fluid pressure control device according to an embodiment of the present invention. Fig. 3 is a diagram showing a hydraulic circuit in a cap according to an embodiment of the present invention. Fig. 4 is a diagram showing main parts of a straight traveling control valve and an electromagnetic proportional valve according to an embodiment of the present invention. Fig. 5 is a diagram showing main parts of a control valve and an electromagnetic proportional valve according to an embodiment of the present invention. Fig. 6 is a diagram showing main parts of a neutral cut valve according to an embodiment of the present invention.

[0007] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0008] The fluid pressure control device 100 described below is used in a work machine such as a power shovel. Although the following description will be given of a case in which the work machine is a power shovel, the work machine may be another work machine such as a wheel loader. Furthermore, although hydraulic oil is used as the working fluid, the working fluid may be another fluid such as hydraulic water.

[0009] As shown in FIG. 1, the fluid pressure control device 100 includes a first circuit system 210 connected to a first pump OP1 and supplied with hydraulic oil from the first pump OP1, and a second circuit system 220 connected to a second pump OP2 and supplied with hydraulic oil from the second pump OP2.

[0010] The first circuit system 210 comprises a control valve 5 that controls the supply and discharge of hydraulic oil to the actuator, a first neutral passage 211 that guides hydraulic oil from the first pump OP1 to a tank T through the control valve 5, a first supply passage 212 that branches off from the first neutral passage 211 upstream of the control valve 5 and connects to the control valve 5, and guides hydraulic oil to be supplied to the actuator to the control valve 5, a first tank passage 213 that connects the control valve 5 and the tank T, and guides hydraulic oil discharged from the actuator through the control valve 5 to the tank T, and a first relief valve 214 that is provided downstream of the control valve 5 in the first neutral passage 211 and determines the maximum pressure of the first neutral passage 211.

[0011] The second circuit system 220 comprises a control valve 10 that controls the supply and discharge of hydraulic oil to the actuator, a second neutral passage 221 that guides hydraulic oil from the second pump OP2 to a tank T through the control valve 10, a second supply passage 222 that branches off from the second neutral passage 221 upstream of the control valve 10 and connects to the control valve 10, and guides the hydraulic oil to be supplied to the actuator to the control valve 10, a second tank passage 223 that connects the control valve 10 and the tank T, and guides the hydraulic oil discharged from the actuator through the control valve 10 to the tank T, and a second relief valve 224 that is provided downstream of the control valve 10 in the second neutral passage 221 and determines the maximum pressure of the second neutral passage 221.

[0012] A first pump pressure passage 215 branches off from the first neutral passage 211 upstream of the control valve 5, and guides hydraulic oil at pump pressure (discharge pressure) discharged from the first pump OP1. A second pump pressure passage 225 branches off from the second supply passage 222 upstream of the control valve 10, and guides hydraulic oil at pump pressure discharged from the second pump OP2. The pump pressure passages 215, 225 are connected to a relief passage 230 via check valves C1, C2, and hydraulic oil from either the first pump OP1 or the second pump OP2, whichever has the higher pump pressure, flows into the relief passage 230. The relief passage 230 is connected to the first tank passage 213 via a relief valve 231, which determines the maximum pressure of the hydraulic oil from the first pump OP1 or the second pump OP2, thereby determining the maximum pressure of the hydraulic oil from the first pump OP1 or the second pump OP2.

[0013] The check valves C1, C2, etc. are oriented as shown in the figure, and for example, the check valve C1 allows the flow of hydraulic oil from the first pump OP1 side and blocks the flow of hydraulic oil from the opposite side. The first tank passage 213 connects the control valve 5 and the tank T, and is also in communication with the second tank passage 223 via communication passages 232, 233.

[0014] The first circuit system 210 has a plurality of control valves 5, which are connected in series by a first neutral passage 211 and in parallel by a first supply passage 212 and a first tank passage 213. Check valves C11 to C14 are provided at the branching portions of the first supply passage 212 to the control valves 5B to 5E, respectively.

[0015] The first neutral passage 211 is provided with a plurality of control valves 5, which are arranged in this order from the upstream side: a first traveling control valve 5A that controls the supply and discharge of hydraulic oil to a traveling motor provided on the left side of the body of the power shovel (not shown); a spare control valve 5B that controls the supply and discharge of hydraulic oil to an actuator that drives an attachment such as a breaker or crusher that is attached in place of a bucket; a swing control valve 5C that controls the supply and discharge of hydraulic oil to a swing motor that swings a swing body that is arranged on top of the body; a boom second-speed control valve 5D that controls the supply and discharge of hydraulic oil to an actuator that drives the boom; and an arm first-speed control valve 5E that controls the supply and discharge of hydraulic oil to an arm cylinder 90 that serves as an actuator that drives the arm.

[0016] In the first circuit system 210, when all the control valves 5 are in the neutral position, the first pump OP1 and the tank T are connected through the first neutral passage 211, and when at least one of the multiple control valves 5 is in the operating position, the connection between the first pump OP1 and the tank T through the first neutral passage 211 is cut off.

[0017] The second circuit system 220 has a plurality of control valves 10, which are connected in series by a second neutral passage 221 and in parallel by a second supply passage 222 and a second tank passage 223, respectively.

[0018] The second neutral passage 221 is provided with a plurality of control valves 10, which are, in order from the upstream side, a second traveling control valve 10A that controls the supply and discharge of hydraulic oil to a traveling motor provided on the right side of the body of the power shovel, a bucket control valve 10B that controls the supply and discharge of hydraulic oil to an actuator that drives the bucket, a boom first-speed control valve 10C that controls the supply and discharge of hydraulic oil to a boom cylinder 91 that serves as an actuator that drives the boom, and an arm second-speed control valve 10D that controls the supply and discharge of hydraulic oil to an actuator that drives the arm.

[0019] The second circuit system 220 is further provided with a straight traveling control valve 7. The straight traveling control valve 7 is provided in the second neutral passage 221 upstream of the control valve 10 (upstream of the second traveling control valve 10A), and the straight traveling control valve 7 is connected to a first supply passage 212. The first supply passage 212 has an upstream supply passage 212a that connects the first neutral passage 211 and the straight traveling control valve 7, and a downstream supply passage 212b that connects the straight traveling control valve 7 and the control valves 5B to 5E. The upstream supply passage 212a is connected to the first traveling control valve 5A, and the downstream supply passage 212b branches off and is connected to the control valves 5B to 5E.

[0020] The second supply passage 222 branches off from the second neutral passage 221 at a position upstream of the straight traveling control valve 7, and check valves C21 to C24 are provided at the branching portion of the second supply passage 222 to the control valves 10A to 10D. A branch supply passage 226 that supplies hydraulic oil to the second traveling control valve 10A branches off from the second neutral passage 221 at a position downstream of the straight traveling control valve 7 and upstream of the second traveling control valve 10A, and is connected to the second supply passage 222 at a position downstream of the check valve C21. In addition to the check valve C21, a throttle TH is also provided at the branching portion of the second supply passage 222 to the second traveling control valve 10A, and the throttle TH is provided upstream of the check valve C21 at the branching portion.

[0021] The straight-line travel control valve 7 has a normal position A that connects the upstream supply passage 212a and the downstream supply passage 212b and also connects the second pump OP2 and the second travel control valve 10A, and a straight-line travel position B that connects the upstream supply passage 212a and the second travel control valve 10A and also connects the second pump OP2 and the downstream supply passage 212b.

[0022] At straight travel position B, when the travel motor and an actuator other than the travel motor are operated simultaneously, hydraulic oil discharged from the first pump OP1 is supplied to the first travel control valve 5A and the second travel control valve 10A, and hydraulic oil discharged from the second pump OP2 is supplied to the other control valves 5B to 5E and 10B to 10D. Therefore, even when the travel motor and an actuator other than the travel motor are operated simultaneously, the vehicle's ability to travel straight is ensured.

[0023] A branch supply passage 216 that supplies hydraulic oil to the control valves 5B to 5E branches off from a portion of the first neutral passage 211 between the control valves 5A and 5B and connects to the downstream supply passage 212b upstream of the control valves 5B to 5E through a check valve C15. Therefore, when the first traveling control valve 5A is in the neutral position, hydraulic oil can also be supplied from the first pump OP1 through the branch supply passage 216 to the control valves 5B to 5E.

[0024] A neutral cut valve 20 is further provided in the second neutral passage 221. The neutral cut valve 20 is provided downstream of the control valve 10 (downstream of the arm second-speed control valve 10D) in the second neutral passage 221. The neutral cut valve 20 has a normal position D in which the second neutral passage 221 is connected, and a blocking position E in which the second neutral passage 221 is blocked, and can be switched between the two positions.

[0025] When the neutral cut valve 20 is in the normal position D, when all the control valves 10 are in the neutral position, the second pump OP2 and the tank T are connected through the second neutral passage 221, and when at least one of the multiple control valves 10 is in the operating position, the connection between the second pump OP2 and the tank T through the second neutral passage 221 is cut off.

[0026] Even when at least one of the control valves 10 is in the actuated position, the neutral cut valve 20 can block the flow of hydraulic oil in the second neutral passage 221 when the control valve 10 in the actuated position does not sufficiently block the flow of hydraulic oil in the second neutral passage 221. This makes it possible to suppress a pressure drop of the hydraulic oil through the second neutral passage 221.

[0027] A supply / discharge passage 217 that communicates with the high load side pressure chamber 90a of the arm cylinder 90 and guides hydraulic oil to and from the high load side pressure chamber 90a is connected to the arm first-speed control valve 5E in the first circuit system 210. In the arm cylinder 90 that contracts when lifting the arm, the high load side pressure chamber 90a is configured as the rod side chamber.

[0028] A flow rate adjustment valve 218 that adjusts the flow rate of hydraulic oil is provided downstream of the check valve C14 in the downstream supply passage 212b. By limiting the flow rate of hydraulic oil supplied to the arm cylinder 90 by the flow rate adjustment valve 218, it is possible to increase the amount of hydraulic oil supplied to the other actuators when multiple actuators are operated in combination, and it is possible to prevent the arm cylinder 90 from operating before the other actuators.

[0029] A branch supply passage 219, which branches off from a portion of the first neutral passage 211 between the control valves 5D and 5E and supplies hydraulic oil to the arm first-speed control valve 5E, joins the downstream supply passage 212b downstream of the flow rate adjustment valve 218 via a check valve C16. In addition, a branch supply passage 227, which branches off from a portion of the second neutral passage 221 between the control valves 10C and 10D and supplies hydraulic oil to the arm second-speed control valve 10D, joins the second supply passage 222 downstream of the check valve C24 via a check valve C25.

[0030] The first circuit system 210 is further provided with a first load holding section 60 that is interposed in the supply / discharge passage 217 and that holds the load pressure acting on the high-load pressure chamber 90a. The first load holding section 60 holds the load pressure, thereby preventing the arm from descending.

[0031] The first load holding section 60 has a first operated check valve 61 interposed in the supply / discharge passage 217 and having a back pressure chamber 61a, a first switching valve 62 that switches the operation of the first operated check valve 61, and a first check valve passage 63 that is connected to the first operated check valve 61 through the first switching valve 62, and the hydraulic oil in the back pressure chamber 61a is led to the outside of the first load holding section 60 through the first check valve passage 63 in accordance with the switching of the first switching valve 62.

[0032] A supply / discharge passage 228 that communicates with the high load side pressure chamber 91 a of the boom cylinder 91 and guides hydraulic oil to and from the high load side pressure chamber 91 a is connected to the boom first-speed control valve 10C in the second circuit system 220. In the boom cylinder 91 that extends when the boom is raised, the high load side pressure chamber 91 a is configured as the bottom side chamber.

[0033] The second circuit system 220 is further provided with a second load holding section 65 that is interposed in the supply / discharge passage 228 and holds the load pressure acting on the high-load-side pressure chamber 91 a. The second load holding section 65 holds the load pressure, thereby preventing the boom from lowering.

[0034] The second load holding section 65 has a second operated check valve 66 interposed in the supply / discharge passage 228 and having a back pressure chamber 66a, a second switching valve 67 that switches the operation of the second operated check valve 66, and a second check valve passage 68 that is connected to the second operated check valve 66 through the second switching valve 67, and the hydraulic oil in the back pressure chamber 66a is led to the outside of the second load holding section 65 through the second check valve passage 68 in accordance with the switching of the second switching valve 67.

[0035] The first check valve passage 63 and the second check valve passage 68 are connected to the neutral cut valve 20 through a drain introduction passage 30f that introduces drain (hydraulic oil discharged into the tank T) to the drain chamber 23 of the neutral cut valve 20 described later.

[0036] The straight traveling control valve 7 is driven in response to the pressure (pilot pressure) of hydraulic oil introduced into the pilot chamber 7a, and the control valve 10 is driven in response to the pressure (pilot pressure) of hydraulic oil introduced into the pilot chambers 11A and 11B. The neutral cut valve 20 is driven in response to the pressure (pilot pressure) of hydraulic oil introduced into a pilot chamber 27 of the neutral cut valve 20. Hereinafter, the straight traveling control valve 7 will also be simply referred to as the control valve 7.

[0037] Hydraulic oil reduced to secondary pressure by a solenoid proportional valve 50 (see FIG. 2) is introduced into the pilot chambers 7a, 11A of the control valves 7, 10 through a secondary pressure passage 42, which will be described later. Hydraulic oil at pilot pressure is introduced from the outside into the pilot chamber 27 of the neutral cut valve 20 through a pilot pressure passage 28. Note that hydraulic oil reduced to secondary pressure by a solenoid proportional valve similar to the solenoid proportional valve 50 is also introduced into the pilot chamber 11B of the control valve 10 and the pilot chamber of the control valve 5.

[0038] Next, the main parts of the fluid pressure control device 100 including the control valves 7, 10 and the neutral cut valve 20 will be described.

[0039] 2, the fluid pressure control device 100 includes the control valves 7, 10 as first control valves driven by hydraulic oil guided to pilot chambers 7a, 11A, a neutral cut valve 20 as a second control valve whose position is switched depending on the balance between the biasing force of a spring 21 and the pressure (pilot pressure) of the hydraulic oil acting from the opposite side of the spring 21, a housing 30 in which the control valves 7, 10 and the neutral cut valve 20 are provided, and a cap 40 attached to the housing 30 in which an electromagnetic proportional valve 50 is provided that controls the pilot chambers 7a, 11A and the pressure (pilot pressure) of the hydraulic oil guided to the pilot chambers 7a, 11A. The control valves 7, 10 and the neutral cut valve 20 are arranged so that their axial directions are parallel to each other and extend in the vertical direction in FIG.

[0040] As shown in FIG. 4, the straight-line travel control valve 7 has a pilot chamber 7a, a spool 7b that is driven by the pressure of hydraulic oil introduced into the pilot chamber 7a, a rod 7c that is connected to one end of the spool 7b and extends into the pilot chamber 7a, and a spring 7d (see FIG. 1) that applies a biasing force to the spool 7b from the side opposite the pilot chamber 7a.

[0041] As shown in FIG. 5, the control valve 10 has a pilot chamber 11A, a spool 12 that is driven by the pressure of hydraulic oil introduced into the pilot chamber 11A, a rod 13 that is connected to one end of the spool 12 and extends into the pilot chamber 11A, a spring 14 that is housed in the pilot chamber 11A and applies a biasing force to one end of the spool 12, and spring receiving members 15 and 16 that are housed in the pilot chamber 11A and can slide along the outer periphery of the rod 13 with the spring 14 interposed therebetween.

[0042] As shown in Figure 6, the neutral cut valve 20 has a spring 21, a spool 22 that is driven by the biasing force of the spring 21 and the pressure of hydraulic oil (pilot pressure) acting from the opposite side of the spring 21, a drain chamber 23 that houses the spring 21, a rod 24 that is connected to one end of the spool 22 and extends into the drain chamber 23, spring receiving members 25 and 26 that are housed in the drain chamber 23 so as to be slidable along the outer periphery of the rod 24 with the spring 21 interposed therebetween, and a pilot chamber 27 that applies the pressure of hydraulic oil (pilot pressure) to the spool 22 from the opposite side of the spring 21.

[0043] When pilot pressure is supplied to the pilot chamber 27, the pilot pressure causes the spool 22 to move toward the drain chamber 23 against the biasing force of the spring 21, thereby blocking the flow of hydraulic oil in the second neutral passage 221. When the supply of pilot pressure to the pilot chamber 27 is blocked, the spool 22 moves toward the pilot chamber 27 due to the biasing force of the spring 21, thereby allowing the flow of hydraulic oil in the second neutral passage 221.

[0044] 2, the spool 7b of the straight-line travel control valve 7, the spool 12 of the control valve 10, and the spool 22 of the neutral cut valve 20 are slidably mounted in the housing 30. The housing 30 has an installation surface 30a on which the cap 40 is installed. The installation surface 30a of the housing 30 has openings 30b, 30c, and 30d for the spools 7b, 12, and 22.

[0045] The cap 40 has a mounting surface 40a for mounting to the housing 30, and is fixed to the housing 30 with bolts (not shown) with the mounting surface 40a abutting the installation surface 30a. The pilot chambers 7a, 11A and the drain chamber 23 open to the mounting surface 40a of the cap 40, and the pilot chambers 7a, 11A and the drain chamber 23 are defined by attaching the cap 40 to the housing 30. Therefore, the cap 40 is provided with the drain chamber 23 of the neutral cut valve 20 in addition to the pilot chambers 7a, 11A of the control valves 7, 10.

[0046] The cap 40 is a long cap that extends in the axial direction (vertical direction in FIG. 2 ) according to the lengths of the pilot chamber 11A that accommodates the spring 14 and the drain chamber 23 that accommodates the spring 21. The pilot chamber 7a and the rod 7c of the straight traveling control valve 7 may be formed shorter than the pilot chamber 11A of the control valve 10 and the drain chamber 23 of the neutral cut valve 20.

[0047] The cap 40 has an installation surface 40b on which the electromagnetic proportional valve 50 is installed, and a housing chamber 44 formed in the installation surface 40b to house the valve element 51 of the electromagnetic proportional valve 50. The installation surface 40b is located opposite the mounting surface 40a, and the housing chamber 44 extends in a direction perpendicular to the installation surface 40b (the up-down direction in FIG. 2 ) and thus extends along the axial direction of the control valves 7, 10 and the neutral cut valve 20. The electromagnetic proportional valve 50 is attached to the installation surface 40b with the valve element 51 inserted into the housing chamber 44, and the valve element 51 is slidably housed in the housing chamber 44.

[0048] As shown in FIGS. 2 to 5, the cap 40 has a primary pressure passage 41 that guides the hydraulic oil discharged from a pump (for example, the second pump OP2 shown in FIG. 1) serving as a fluid pressure supply source to the electromagnetic proportional valve 50 as hydraulic oil at a primary pressure, a secondary pressure passage 42 (see FIGS. 3 to 5) that guides the hydraulic oil that has been reduced in pressure from the primary pressure hydraulic oil guided to the primary pressure passage 41 to a secondary pressure by the electromagnetic proportional valve 50 to the pilot chambers 7 a, 11A, and a drain passage 43 that guides the hydraulic oil that is discharged from the secondary pressure passage 42 (i.e., from the pilot chambers 7 a, 11A) through the electromagnetic proportional valve 50.

[0049] As shown in FIG. 2 , the primary pressure passage 41 and the drain passage 43 open to one end face (the right end face in FIG. 1 ) 40c and the other end face (the left end face in FIG. 1 ) 40d of the cap 40. The primary pressure passage 41 has a main primary pressure passage 41a extending in the direction in which the plurality of electromagnetic proportional valves 50 are arranged, and the drain passage 43 has a main drain passage 43a extending in the direction in which the plurality of electromagnetic proportional valves 50 are arranged. The main primary pressure passage 41a and the main drain passage 43a extend linearly from the one end face 40c to the other end face 40d of the cap 40, and hydraulic oil from the pump is guided to one end (the right end in FIG. 1 ) of the main primary pressure passage 41a through an inlet opening IO of the primary pressure passage 41. The other end (the left end in FIG. 1 ) of the main primary pressure passage 41a and both ends of the main drain passage 43a are sealed by plugs PG.

[0050] The electromagnetic proportional valve 50 has a valve body 51 formed of a shaft-shaped member, a solenoid 52 that applies thrust to the valve body 51, and a coil spring 53 (see Figures 3 to 5) that serves as a biasing member that applies a biasing force to the valve body 51 in a direction opposite to the thrust of the solenoid 52.

[0051] The solenoid 52 is fixed to the cap 40 with bolts. The solenoid 52 is an actuator that moves a push rod 52a (see FIGS. 4 and 5) forward and backward in response to a supplied control current, and one end of the valve element 51 is fixed to the push rod 52a. The coil spring 53 (see FIGS. 3 to 5) contracts in accordance with the amount of movement of the valve element 51, and applies to the valve element 51 a biasing force corresponding to the amount of contraction (amount of elastic deformation) from its natural length, thereby biasing the valve element 51 toward the solenoid 52.

[0052] The electromagnetic proportional valve 50 controls the secondary pressure (pilot pressure) output to the pilot chambers 7a, 11A (see FIG. 2) in accordance with the control current supplied to the solenoid 52. A direct proportional pressure reducing valve that increases the secondary pressure as the current supplied to the solenoid 52 increases can be used as the electromagnetic proportional valve 50. A plurality of electromagnetic proportional valves 50 are provided in the housing 30 corresponding to the straight traveling control valve 7 and the plurality of control valves 10.

[0053] 3 to 5, the primary pressure passage 41 further has an auxiliary primary pressure passage 41b, one end of which is connected to the main primary pressure passage 41a and the other end of which is connected to the electromagnetic proportional valve 50. A plurality of auxiliary primary pressure passages 41b are provided corresponding to each electromagnetic proportional valve 50. A plurality of secondary pressure passages 42 are also provided corresponding to each electromagnetic proportional valve 50.

[0054] The drain passage 43 further includes a sub-drain passage 43b, one end of which is connected to the main drain passage 43a and the other end of which is connected to the electromagnetic proportional valve 50. A plurality of sub-drain passages 43b are provided corresponding to each electromagnetic proportional valve 50.

[0055] The solenoid proportional valve 50 has an input port P1 through which hydraulic oil at primary pressure is guided from a primary pressure passage 41, an output port P2 through which hydraulic oil at secondary pressure is guided to a secondary pressure passage 42, and a drain port P3 through which drain is guided to a drain passage 43. As shown in Figures 4 and 5, the passages 41 to 43 communicate with the accommodation chamber 44 via the ports P1 to P3.

[0056] As shown in FIG. 3 , the solenoid proportional valve 50 operates between a closed position C in which communication between the input port P1 and the output port P2 is blocked and communication between the output port P2 and the drain port P3 is established, and an open position O in which communication between the input port P1 and the output port P2 is established and communication between the output port P2 and the drain port P3 is blocked. At an intermediate position M between the closed position C and the open position O, the input port P1 communicates with both the output port P2 and the drain port P3 via a restriction.

[0057] The electromagnetic proportional valve 50 controls the secondary pressure (pilot pressure) output to the pilot chambers 7a, 11A (see FIG. 2) by adjusting the communication between the input port P1 and the drain port P3 and the output port P2 through the balance (equivalent) of the thrust force exerted on the valve body 51 by the solenoid 52, the biasing force of the coil spring 53, and the thrust force due to the secondary pressure.

[0058] 2, the cap 40 in which the pilot chambers 7a, 11A of the control valves 7, 10 are provided is further provided with a drain port 45 that discharges hydraulic oil from the drain chamber 23 of the neutral cut valve 20, and a connecting passage 46 that connects the drain port 45 to the neutral cut valve 20. The drain port 45 communicates with the drain chamber 23 of the neutral cut valve 20 through the connecting passage 46, and discharges hydraulic oil from the drain chamber 23 to the tank T (see FIG. 1) through piping (not shown).

[0059] The drain port 45 extends in the direction in which the storage chamber 44 extends in the cap 40 (vertical direction in Figure 2) and opens to the installation surface 40b, which is the outer surface on which the storage chamber 44 is formed, and is positioned so that it overlaps with the drain chamber 23 when viewed along the opening direction of the drain port 45 (vertical direction in Figure 2).

[0060] This allows the drain port 45 to be positioned overlapping the drain chamber 23 by utilizing the thickness of the cap 40 where the storage chamber 44 is provided (the thickness along the extension direction of the storage chamber 44), thereby making the cap 40 more compact. This prevents the cap 40 from becoming larger in size in order to ensure installation space for the drain port 45, improving layout flexibility when installing the fluid pressure control device 100. Furthermore, by providing the drain port 45 overlapping the drain chamber 23, the connecting passage 46 connecting the drain chamber 23 and the drain port 45 can be linearly extended along the opening direction of the drain port 45 (the vertical direction in FIG. 2 ), thereby facilitating and simplifying the processing of the connecting passage 46. The drain port 45 is positioned coaxially with the drain chamber 23.

[0061] As shown in Figure 6, the connecting passage 46 extends from the center of the bottom of the drain port 45 along the opening direction of the drain port 45 (the up-down direction in Figure 6) and connects to the end of the neutral cut valve 20 on the drain chamber 23 side. The cap 40 has a drain chamber wall 47 that forms the drain chamber 23, and the rod 24 has a communicating passage 24a that communicates the drain chamber 23 with the connecting passage 46 when the movement of the spool 22 is restricted by the drain chamber wall 47. Therefore, even when the movement of the spool 22 is restricted by the drain chamber wall 47, the flow of hydraulic oil from the drain chamber 23 to the drain port 45 is not interrupted, and the hydraulic oil in the drain chamber 23 can be discharged to the tank T through the drain port 45 regardless of the position of the spool 22.

[0062] The accommodation hole 30d of the neutral cut valve 20 communicates with the drain chamber 23 through a clearance with the spool 22, and hydraulic oil flows into the drain chamber 23 from the accommodation hole 30d. Hydraulic oil discharged from the first load holding unit 60 and the second load holding unit 65 (see FIG. 1) is also introduced into the drain chamber 23 through a drain introduction passage 30f that communicates with the accommodation hole 30d. Therefore, the hydraulic oil discharged from the first load holding unit 60 and the second load holding unit 65 is also discharged from the drain chamber 23 through the drain port 45 to the tank T. The drain introduction passage 30f does not have to be connected to the drain chamber 23.

[0063] A drain passage 43 is further connected to the connection passage 46. Therefore, the drain port 45 also communicates with the drain passage 43, and the hydraulic oil discharged from the pilot chambers 7a, 11A (see FIGS. 4 and 5) through the proportional solenoid valve 50 (see FIG. 5) to the drain passage 43 is also discharged to the tank T through the drain port 45.

[0064] In the fluid pressure control device 100, the drain chamber 23 of the neutral cut valve 20 and the drain port 45 are provided together in the cap 40 in which the pilot chambers 7a, 11A of the control valves 7, 10 are provided. In this way, the drain passage 43 and the drain port 45 can be connected in the cap 40. As a result, the drain port 45 can be shared between the pilot chambers 7a, 11A and the drain chamber 23, simplifying the piping connection to the drain port 45.

[0065] 2 and 4 to 6, the drain port 45 is arranged alongside a plurality of solenoid proportional valves 50 that are lined up in the direction in which the main drain passage 43a extends (the left-right direction in FIG. 2). This simplifies the passage structure by simply extending the sub-drain passage 43b and the connecting passage 46 along the axial direction (the up-down direction in FIG. 2) and connecting them to the main drain passage 43a.

[0066] 5 and 6 , the control valve 10 is disposed offset in the horizontal direction (to the right in FIG. 5 ) from the plurality of electromagnetic proportional valves 50 that are disposed side by side, and the neutral cut valve 20 is disposed coaxially with the drain port 45 that is disposed side by side with the plurality of electromagnetic proportional valves 50. Therefore, the control valve 10 and the neutral cut valve 20 are disposed offset from each other in the horizontal direction (left and right direction in FIGS. 5 and 6 ) with respect to the arrangement direction of the plurality of electromagnetic proportional valves 50. Therefore, even if the control valve 10 and the neutral cut valve 20 are brought closer to each other in the arrangement direction of the plurality of electromagnetic proportional valves 50 (left and right direction in FIG. 2 ), the control valve 10 and the neutral cut valve 20 are less likely to interfere with each other compared to when the control valve 10 and the neutral cut valve 20 are arranged in a horizontal straight line in the same direction, and the cap 40 can be made more compact.

[0067] In this embodiment, the case has been described in which the control valve 10 for the actuator that supplies and discharges hydraulic oil to the actuator and the straight-line driving control valve 7 other than for the actuator are provided in the cap 40, but one of the control valves 7, 10 does not have to be provided in the cap 40. Also, instead of the neutral cut valve 20, a three-position switching valve or the like may be used as the second control valve.

[0068] In this embodiment, the structure shown in Figures 2, 4 to 6 and the passage configuration shown in Figure 3 are realized in the second circuit system 220 provided with the control valve 10 and neutral cut valve 20, but a similar structure and passage configuration may also be realized by providing a neutral cut valve and drain port similar to the neutral cut valve 20 and drain port 45 in the first circuit system 210 provided with the control valve 5.

[0069] The configuration, operation, and effects of the embodiment of the present invention will be described below.

[0070] The fluid pressure control device 100 includes control valves 7, 10 as first control valves driven by hydraulic oil guided to pilot chambers 7 a, 11A, a neutral cut valve 20 as a second control valve whose position is switched depending on the balance between the biasing force of a spring 21 and the pressure of hydraulic oil acting from the opposite side of the spring 21, a housing 30 in which the control valves 7, 10 and the neutral cut valve 20 are provided, and a cap 40 attached to the housing 30 in which an electromagnetic proportional valve 50 is provided to control the pressure of the hydraulic oil guided to the pilot chambers 7 a, 11A and the pilot chambers 7 a, 11A. The cap 40 has a drain passage 43 that guides hydraulic oil discharged from the pilot chambers 7 a, 11A of the control valves 7, 10 through the electromagnetic proportional valve 50, a drain chamber 23 that accommodates the spring 21 of the neutral cut valve 20, and a drain port 45 that discharges hydraulic oil from the drain chamber 23, and the drain passage 43 and the drain port 45 are in communication with each other.

[0071] According to this configuration, the drain chamber 23 of the neutral cut valve 20 and the drain port 45 are provided together in the cap 40 in which the pilot chambers 7a, 11A of the control valves 7, 10 are provided, so that the drain port 45 can be shared by the pilot chambers 7a, 11A and the drain chamber 23, simplifying the piping connection to the drain port 45.

[0072] The cap 40 has a storage chamber 44 that houses the valve body 51 of the electromagnetic proportional valve 50, and the drain port 45 extends in the direction in which the storage chamber 44 extends in the cap 40, opening into the installation surface 40b, which is the outer surface on which the storage chamber 44 is formed, and is positioned so that it overlaps with the drain chamber 23 when viewed along the opening direction of the drain port 45.

[0073] According to this configuration, the thickness of the cap 40 at the portion where the storage chamber 44 is provided (the thickness along the direction in which the storage chamber 44 extends) is utilized to provide the drain port 45 in an overlapping position with the drain chamber 23, thereby making it possible to make the cap 40 compact.

[0074] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0075] This application claims priority based on Japanese Patent Application No. 2024-106379, filed with the Japan Patent Office on July 1, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A fluid pressure control device comprising: a first control valve driven by working fluid led to a pilot chamber; a second control valve whose position is switched according to the balance between the biasing force of a biasing member and the pressure of working fluid acting from the opposite side of the biasing member; a housing in which the first control valve and the second control valve are provided; and a cap attached to the housing in which an electromagnetic proportional valve is provided that controls the pilot chamber and the pressure of the working fluid led to the pilot chamber, wherein the cap has: a drain passage that leads working fluid discharged from the pilot chamber of the first control valve through the electromagnetic proportional valve; a drain chamber that accommodates the biasing member of the second control valve; and a drain port that discharges working fluid from the drain chamber, wherein the drain passage and the drain port are connected.

2. A fluid pressure control device as set forth in claim 1, wherein the cap has a chamber that houses the valve body of the electromagnetic proportional valve, and the drain port extends in the direction in which the chamber extends in the cap, opens onto the outer surface on which the chamber is formed, and is positioned so as to overlap the drain chamber when viewed along the opening direction of the drain port.

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