Poppet valve device, and hydraulic drive system comprising the same

Abstract

To provide a poppet valve device that can improve controllability related to a flow rate.SOLUTION: A poppet valve device comprises: a housing including a valve passage, a valve seat interposed in the valve passage, a valve hole comprising a back pressure chamber to which an upstream pressure of the valve passage is guided, and a discharge flow passage leading to the back pressure chamber; a poppet valve element housed in the valve hole so as to be capable of being seated on and separated from the valve seat, to be stroked in accordance with a back pressure of the back pressure chamber, and for opening the valve passage at an opening degree according to a stroke amount; and a spool for adjusting the back pressure by controlling the opening degree of the discharge flow passage. The discharge flow passage is connected to a tank.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a poppet valve device that adjusts the opening degree of a valve passage, and a hydraulic drive system including the same. [Background technology]

[0002] A known example of a poppet valve device that adjusts the aperture of a valve passage is the flow control valve disclosed in Patent Document 1. In the flow control valve of Patent Document 1, a main valve seat is formed between an inlet passage and an outlet passage, and the main valve opens and closes the inlet passage and the outlet passage by seating and lifting on the main valve seat. The main valve strokes in response to hydraulic pressure in a back pressure chamber, opening the inlet passage and the outlet passage at an aperture corresponding to the stroke amount. The back pressure chamber is connected to the inlet passage via a feedback passage and is further connected to the outlet passage via a pilot passage. A pilot valve is disposed in the pilot passage, and the pilot valve controls the aperture of the pilot passage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-166300 Summary of the Invention [Problem to be solved by the invention]

[0004] Construction machinery such as hydraulic excavators are equipped with flow control valves to control the flow of hydraulic fluid to hydraulic actuators such as boom cylinders. Flow control valves are mainly composed of spool valves, but it is being considered to adopt poppet valve devices such as the flow control valve in Patent Document 1. However, with poppet valve devices such as the flow control valve in Patent Document 1, when the pressure difference between the hydraulic pressure in the inlet flow path and the hydraulic pressure in the outlet flow path increases, the back pressure is likely to fluctuate, reducing controllability over the flow rate.

[0005] Therefore, an object of the present disclosure is to provide a poppet valve device that can improve controllability regarding flow rate, and a hydraulic drive system including the same. [Means for solving the problem]

[0006] The poppet valve device of the first disclosure comprises: a housing including a valve passage, a valve seat interposed in the valve passage, a valve hole having a back pressure chamber to which upstream pressure of the valve passage is directed, and a discharge passage connected to the back pressure chamber; a poppet valve element accommodated in the valve hole so as to be able to seat on and separate from the valve seat, which strokes in response to the back pressure of the back pressure chamber and opens the valve passage at an opening degree corresponding to the stroke amount; and a spool which adjusts the back pressure by controlling the opening degree of the discharge passage, and the discharge passage is connected to a tank.

[0007] According to the above disclosure, the exhaust passage is connected to the tank. Therefore, the back pressure in the back pressure chamber can be stabilized regardless of the pressure difference between the upstream and downstream pressures of the valve passage. This improves the controllability of the flow rate in the poppet valve device.

[0008] The hydraulic drive system of the present disclosure controls the flow of hydraulic fluid from a pump to two ports of a hydraulic actuator, and includes a first meter-in control valve device that controls the flow rate of hydraulic fluid supplied to one port of the hydraulic actuator, a first meter-out control valve device that controls the flow rate of hydraulic fluid discharged from the one port, a second meter-in control valve device that controls the flow rate of hydraulic fluid supplied to the other port of the hydraulic actuator, and a second meter-out control valve device that controls the flow rate of hydraulic fluid discharged from the other port, and at least one of the first meter-in control valve device, the first meter-out control valve device, the second meter-in control valve device, and the second meter-out control valve device is the poppet valve device described above.

[0009] According to the above disclosure, at least one of the first meter-in control valve device, the first meter-out control valve device, the second meter-in control valve device, and the second meter-out control valve device is the poppet valve device described above, thereby reducing the cost of the hydraulic drive system.

[0010] The poppet valve device of the second disclosure includes a housing including a valve passage, a valve seat interposed in the valve passage, a valve hole having a back pressure chamber to which upstream pressure of the valve passage is introduced, a discharge passage connected to the back pressure chamber, and a spool hole interposed in the discharge passage; a poppet valve element accommodated in the valve hole so as to be able to seat on and separate from the valve seat, which strokes in response to the back pressure of the back pressure chamber and opens the valve passage at an opening degree in accordance with the stroke amount; and a spool hole inserted in the axial direction so as to be able to stroke, which controls the opening degree of the discharge passage by stroking to adjust the back pressure. the discharge flow path has an inlet-side flow path portion connected to the back pressure chamber and the spool hole, and an outlet-side flow path portion connected to the spool hole, the spool has a first notch that connects the inlet-side flow path portion and the outlet-side flow path portion when the spool switches from a closed position that closes the discharge flow path to an open position that opens the discharge flow path, the first notch having an inlet-side portion that connects to the inlet-side flow path portion when switched, and an outlet-side portion that connects to the outlet-side flow path portion, the inlet-side portion extending in a direction perpendicular to the axial direction, and the outlet-side portion extending in the axial direction.

[0011] According to the disclosure above, the first notch has an inlet-side portion and an outlet-side portion, and the inlet-side portion extends in a direction perpendicular to the axial direction. Therefore, wastewater flowing from the inlet-side flow passage into the inlet-side portion can flow in a direction perpendicular to the axial direction. This reduces the axial flow force that the spool receives from wastewater flowing through the first notch.

[0012] A third disclosed poppet valve device includes a housing including a valve passage, a valve seat interposed in the valve passage, a valve hole having a back pressure chamber to which upstream pressure of the valve passage is introduced, a discharge passage connected to the back pressure chamber, a spool hole interposed in the discharge passage, and a sleeve inserted into the spool hole; a poppet valve element accommodated in the valve hole so as to be able to seat on and separate from the valve seat, which strokes in response to the back pressure of the back pressure chamber and opens the valve passage at an opening degree corresponding to the stroke amount; and a poppet valve element inserted in the sleeve so as to be able to stroke, which controls the opening degree of the discharge passage by stroking to reduce the back pressure. and a spool for adjusting the length of the exhaust passage, the exhaust passage having an inlet-side passage portion connected to the back pressure chamber and the spool hole, and an outlet-side passage portion connected to the spool hole, the sleeve having an inlet-side through passage that is connected to the inlet-side passage portion and penetrates radially, and an outlet-side through passage that is connected to the outlet-side passage portion and penetrates radially, the spool strokes in one axial direction within the sleeve from an open position that closes the exhaust passage to an open position that opens the exhaust passage, and the inlet-side through passage is inclined in one axial direction as it progresses radially.

[0013] According to the above disclosure, the spool strokes in one axial direction within the sleeve from an open position that closes the discharge flow path to an open position that opens the discharge flow path, and the inlet-side through-passage is inclined in one axial direction as it advances in the radial direction. This allows the flow direction of the waste liquid flowing from the inlet-side through-passage into the sleeve to be opposite to the flow direction of the waste liquid flowing in the other axial direction within the sleeve. This reduces the flow force that the spool receives from the waste liquid. [Effects of the Invention]

[0014] According to the first disclosure, it is possible to improve the controllability regarding the flow rate.

[0015] According to the second and third disclosures, the flow force that the spool receives from the waste liquid can be reduced. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2 is a circuit diagram showing a circuit of the hydraulic drive system according to the embodiment of the present disclosure. [Figure 2] 2 is a cross-sectional view showing a first poppet valve device applied to a meter-in flow control valve of the hydraulic drive system of FIG. 1. FIG. [Figure 3] 3 is an enlarged cross-sectional view showing a poppet valve provided in the first poppet valve device of FIG. 2. FIG. [Figure 4] 3 is an enlarged cross-sectional view showing a spool valve provided in the first poppet valve device of FIG. 2. FIG. [Figure 5] 3 is an enlarged cross-sectional view showing a spool of the spool valve of FIG. 2 in a further enlarged manner. FIG. [Figure 6] FIG. 4 is an enlarged cross-sectional view showing a cross section of the spool of FIG. 3. [Figure 7] 2 is a cross-sectional view showing a second poppet valve device applied to a meter-out flow control valve of the hydraulic drive system of FIG. 1. FIG. [Figure 8] 3 is an enlarged cross-sectional view showing a poppet valve provided in the second poppet valve device of FIG. 2. FIG. [Figure 9] FIG. 10 is an enlarged cross-sectional view showing a spool of a spool valve provided in a poppet valve device according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, the poppet valve devices 1 and 2 according to the present embodiment of the present disclosure and the hydraulic drive system 3 including the same will be described with reference to the drawings mentioned above. Note that the concepts of directions used in the following description are used for the convenience of explanation and do not limit the orientation of the configuration of the invention to those directions. Furthermore, the poppet valve devices 1 and 2 and the hydraulic drive system 3 described below are merely one embodiment of the present disclosure. Therefore, the present disclosure is not limited to the embodiment, and additions, deletions, and modifications are possible within the scope of the spirit of the invention.

[0018] [Hydraulic drive system] The hydraulic drive system 3 shown in FIG. 1 is provided in a construction machine such as a shovel. The construction machine is provided with a hydraulic actuator 4, and performs various tasks by driving the hydraulic actuator 4. The hydraulic drive system 3 supplies hydraulic fluid to the hydraulic actuator 4 to drive the hydraulic actuator 4. More specifically, the hydraulic actuator 4 has two ports 4a, 4b. In this embodiment, the hydraulic actuator 4 is a hydraulic cylinder, and has a rod-side port 4a and a head-side port 4b. The hydraulic actuator 4 may also be a hydraulic motor, etc.

[0019] The hydraulic drive system 3 supplies hydraulic fluid to one of two ports 4a, 4b of the hydraulic actuator 4 and discharges the hydraulic fluid from the other port. The hydraulic drive system 3 controls the flow rate of the hydraulic fluid supplied to one of the two ports 4a, 4b (i.e., the meter-in flow rate), and controls the flow rate of the hydraulic fluid discharged from the other port (i.e., the meter-out flow rate). More specifically, the hydraulic drive system 3 can independently control the meter-in flow rate and the meter-out flow rate for the hydraulic actuator 4. The hydraulic drive system 3 configured in this manner includes a hydraulic pump 5, two meter-in control valve devices 6R, 6H, and two meter-out control valve devices 7R, 7H. The hydraulic drive system 3 also includes an operating device 8 and a control device 9.

[0020] The hydraulic pump 5 discharges hydraulic fluid. More specifically, the hydraulic pump 5 is driven by a drive source (e.g., an engine or an electric motor) not shown. This causes the hydraulic pump 5 to discharge hydraulic fluid. In this embodiment, the hydraulic pump 5 is, for example, a variable displacement swash plate pump. However, the hydraulic pump 5 may be a fixed displacement pump. The hydraulic pump 5 may also be a variable displacement bent axis pump or the like, and the type is not important. The hydraulic pump 5 is connected to the pump passage 11 and discharges hydraulic fluid into the pump passage 11.

[0021] The two meter-in control valve devices 6R, 6H control the flow rate (i.e., meter-in flow rate) of hydraulic fluid supplied from the hydraulic pump 5 to each port 4a, 4b. More specifically, the two meter-in control valve devices 6R, 6H are connected in parallel to a pump passage 11 and are connected to the hydraulic pump 5 via the pump passage 11. The first meter-in control valve device 6R, which is one of the two meter-in control valve devices 6R, 6H, is connected to the rod-side port 4a of the hydraulic actuator 4 via a rod-side passage 12. The second meter-in control valve device 6H, which is the other of the two meter-in control valve devices 6R, 6H, is connected to the head-side port 4b of the hydraulic actuator 4 via a head-side passage 13. Each of the meter-in control valve devices 6R, 6H adjusts its opening depending on the energization state (e.g., current or voltage). The meter-in control valve devices 6R, 6H each adjust the opening degree to control the flow rate of the hydraulic fluid flowing from the hydraulic pump 5 to each of the ports 4a, 4b independently of each other.

[0022] The two meter-out control valve devices 7R, 7H control the flow rate (i.e., meter-out flow rate) of hydraulic fluid discharged from the respective ports 4a, 4b to the tank 15. More specifically, the first meter-out control valve device 7R, which is one of the two meter-out control valve devices 7R, 7H, is connected to the rod-side port 4a of the hydraulic actuator 4 via a rod-side passage 12. The second meter-out control valve device 7H, which is the other of the two meter-out control valve devices 7R, 7H, is connected to the head-side port 4b of the hydraulic actuator 4 via a head-side passage 13. More specifically, the first meter-out control valve device 7R is connected to the rod-side passage 12 so as to be parallel to the first meter-in control valve device 6R, and the second meter-out control valve device 7H is connected to the head-side passage 13 so as to be parallel to the second meter-in control valve device 6H. The two meter-out control valve devices 7R, 7H are connected to the tank 15 via a downstream-side passage 14. Each of the meter-out control valve devices 7R, 7H adjusts its opening depending on the energized state (for example, current or voltage). Each of the meter-out control valve devices 7R, 7H adjusts its opening to independently control the flow rate of the hydraulic fluid discharged from each of the ports 4a, 4b to the tank 15.

[0023] An operation command is input to the operating device 8 to operate the hydraulic actuator 4. The operating device 8 has an operating tool 8a. The operating tool 8a is, for example, an operating lever. The operating tool 8a may also be an operating pedal. The operating device 8 outputs an operation command according to the amount of operation of the operating tool 8a.

[0024] The control device 9 controls the opening degrees of the control valve devices 6R, 6H, 7R, and 7H, respectively. More specifically, the control device 9 energizes each of the control valve devices 6R, 6H, 7R, and 7H in response to an operation command output from the operating device 8. More specifically, the control device 9 applies a current or voltage in response to the operation command to each of the control valve devices 6R, 6H, 7R, and 7H. In this way, the control device 9 controls the opening degrees of the control valve devices 6R, 6H, 7R, and 7H to an opening degree in response to the operation amount of the operating implement 8a.

[0025] The hydraulic drive system 3 configured as described above operates to drive the hydraulic actuator 4 as follows. That is, in the hydraulic drive system 3, when the operating tool 8a of the operating device 8 is operated, the operating device 8 outputs an operation command to the control device 9. The control device 9 energizes the control valve devices 6R, 6H, 7R, and 7H in response to the operation command. For example, when the hydraulic actuator 4 is to be contracted, the control device 9 energizes the first meter-in control valve device 6R and the second meter-out control valve device 7H. This causes hydraulic fluid to be supplied to the rod-side port 4a of the hydraulic actuator 4 and the hydraulic fluid to be discharged from the head-side port 4b. This causes the hydraulic actuator 4 to contract. Furthermore, in the hydraulic drive system 3, the first meter-in control valve device 6R controls the meter-in flow rate for the rod-side port 4a, and the second meter-out control valve device 7H controls the meter-out flow rate for the head-side port 4b. The first meter-in control valve device 6R and the second meter-out control valve device 7H can be operated independently of each other. As a result, in the hydraulic drive system 3, the meter-in flow rate for the rod side port 4a and the meter-out flow rate for the head side port 4b can be controlled independently of each other.

[0026] Furthermore, when the hydraulic actuator 4 is to be extended, the control device 9 energizes the second meter-in control valve device 6H and the first meter-out control valve device 7R. This causes hydraulic fluid to be supplied to the head side port 4b of the hydraulic actuator 4 and the hydraulic fluid to be discharged from the rod side port 4a. This causes the hydraulic actuator 4 to be extended. Furthermore, the second meter-in control valve device 6H and the first meter-out control valve device 7R can also be operated independently of each other, so the meter-in flow rate for the head side port 4b and the meter-out flow rate for the rod side port 4a can be controlled independently of each other.

[0027] The two meter-in control valve devices 6R, 6H configured as described above have the same configuration in this embodiment. In this embodiment, the two meter-in control valve devices 6R, 6H are each provided with a first poppet valve device 1, which will be described below. The two meter-out control valve devices 7R, 7H are also each provided with a similar configuration in this embodiment. In this embodiment, the two meter-out control valve devices 7R, 7H are each provided with a second poppet valve device 2, which will be described below. However, the two meter-in control valve devices 6R, 6H do not necessarily have to be configured in the same way, and may be configured differently from each other. The same is true for the two meter-in control valve devices 6R, 6H. Specific configurations of the poppet valve devices 1, 2 applied to the meter-in control valve devices 6R, 6H and the meter-out control valve devices 7R, 7H are described below.

[0028] [First poppet valve device] The first poppet valve device 1 shown in Fig. 2 controls the flow rate of working fluid according to an energized state (for example, current or voltage). The poppet valve device 1 is a valve device in which, for example, a poppet valve 16 and a spool valve 17 are integrally configured. Explained in more detail, the first poppet valve device 1 includes a housing 21, a main valve element 22, and a spool 23. Explained in even more detail, the first poppet valve device 1 further includes a check valve element 24, a main valve spring member 25, an electric device 26, and a spool spring member 27. The poppet valve 16 is configured by a portion of the housing 21 (a first housing portion 21a, which will be described in detail later), the main valve element 22, the check valve element 24, and the main valve spring member 25. On the other hand, the spool valve 17 is made up of a part of the housing 21 (a second housing part 21b, which will be described in detail later), a spool 23, an electric device 26, and a spring member 27 for the spool.

[0029] Furthermore, a valve passage 32 is formed in the first housing portion 21a, as will be described in detail later, and the poppet valve 16 adjusts the opening degree of the valve passage 32. More specifically, the poppet valve 16 adjusts the opening degree of the valve passage 32 in accordance with the back pressure, as will be described in detail later. As a result, the poppet valve 16 allows the flow of hydraulic fluid at a flow rate that corresponds to the back pressure. Furthermore, the spool valve 17 is electrically conductive, and its opening degree is adjusted in accordance with the state of current flow. The spool valve 17 adjusts the back pressure by changing its opening degree.

[0030] [housing] The housing 21 includes a valve hole 31, a valve passage 32, a valve seat 33, and a tank passage 34. The housing 21 also includes a spool hole 35 and a discharge passage 36. More specifically, the housing 21 has a first housing portion 21a and a second housing portion 21b. As shown in FIG. 3, the first housing portion 21a includes the valve hole 31, the valve passage 32, the valve seat 33, and the tank passage 34, and constitutes the poppet valve 16. As shown in FIG. 4, the second housing portion 21b includes the spool hole 35 and the discharge passage 36, and constitutes the spool valve 17.

[0031] [Poppet valve] The poppet valve 16 includes a first housing portion 21a, a main valve element 22, a check valve element 24, and a main valve spring member 25. As described above, the first housing portion 21a includes the valve hole 31, the valve passage 32, the valve seat 33, and the tank passage 34. The valve hole 31 is a bottomed hole extending along a predetermined axis L1. The main valve element 22, which will be described in detail later, is housed in the valve hole 31. The valve passage 32 is formed in the housing 21 (more specifically, in the first housing portion 21a) so as to interpose the valve hole 31 therebetween. More specifically, the valve passage 32 includes a first passage portion 32a and a second passage portion 32b.

[0032] The first passage portion 32a is connected to the valve hole 31 via a valve port 31a that opens at the bottom surface of the valve hole 31. In this embodiment, the first passage portion 32a extends from the valve port 31a in a first direction. The first direction is the direction in which the axis L1 of the valve hole 31 extends. The valve seat 33 is interposed between the first passage portion 32a and the second passage portion 32b. In this embodiment, the valve seat 33 is formed at the bottom surface of the valve hole 31 so as to surround the valve port 31a.

[0033] The second passage portion 32b opens onto the inner circumferential surface of the bottom portion of the valve hole 31 and is connected to the valve hole 31. More specifically, an annular space 31b is formed on the inner circumferential surface of the bottom portion of the valve opening 31a, and the second passage portion 32b opens onto and is connected to the annular space 31b. In this way, the first passage portion 32a and the second passage portion 32b are each connected to the valve hole 31 and are connected to each other via the valve hole 31.

[0034] In the valve passage 32 configured in this manner, for example, the pump passage 11 is connected to the first passage portion 32a, and the rod-side passage 12 or the head-side passage 13 is connected to the second passage portion 32b. Therefore, in the valve passage 32, the working fluid flows from the first passage portion 32a to the second passage portion 32b via the valve hole 31. That is, the first passage portion 32a is located upstream of the valve seat 33 in the valve passage 32, and the second passage portion 32b is located upstream of the valve seat 33 in the valve passage 32.

[0035] The valve hole 31 has a back pressure chamber 31c. The back pressure chamber 31c receives the upstream pressure of the valve passage 32. The upstream pressure is the hydraulic pressure upstream of the valve seat 33 in the valve passage 32. On the other hand, the downstream pressure is the hydraulic pressure downstream of the valve seat 33 in the valve passage 32. In this embodiment, the hydraulic pressure of the first passage portion 32a is received in the back pressure chamber 31c. More specifically, the back pressure chamber 31c is a space defined by the valve hole 31 by the main valve element 22 (described later) and is located on the opposite side of the valve hole 31 from the valve orifice 31a in the first direction. That is, the valve orifice 31a is located on one side of the valve hole 31 in the first direction, and the back pressure chamber 31c is located on the other side of the valve hole 31 in the first direction. The valve hole 31 also has an annular passage portion 31d. The annular passage portion 31d is an annular groove recessed radially outward in the axially intermediate portion of the valve hole 31. The back pressure chamber 31c is connected to the first passage portion 32a via a feedback passage 22a and an annular passage portion 31d, which will be described in detail later.

[0036] 1, the tank passage 34 is connected to a discharge flow path 36 (more specifically, an outlet-side flow path portion 36b) of the second housing portion 21b, which will be described in detail later. The tank passage 34 is also connected to the tank 15, and discharges the waste liquid discharged to the outlet-side flow path portion 36b to the tank 15. Therefore, the pressure of the waste liquid discharged to the tank passage 34 is the tank pressure.

[0037] The main valve element 22, which is an example of a poppet valve element, is provided in the valve hole 31 so as to be movable in a first direction. Explaining in more detail, the main valve element 22 is provided in the valve hole 31 so as to be able to slide in a first direction. Explaining in even more detail, the main valve element 22 is accommodated in the valve hole 31 so as to be able to seat on and leave a valve seat 33. That is, the main valve element 22 is provided in the valve hole 31 so as to be able to move between a closed position where the main valve element 22 seats on the valve seat 33 to close the valve port 31a and an open position where the main valve element 22 leaves the valve seat 33 to open the valve port 31a. Furthermore, in the open position, the main valve element 22 opens the valve port 31a by an opening degree corresponding to the stroke amount. Thus, the main valve element 22 opens and closes the valve port 31a by stroking in the first direction, and adjusts the opening degree of the valve passage 32 according to the stroke amount.

[0038] As shown in FIG. 2, the main valve element 22 defines a back pressure chamber 31c in the valve hole 31. More specifically, the back pressure chamber 31c is formed on the opposite side of the valve port 31a in the first direction across the main valve element 22 in the valve hole 31. As described above, the upstream pressure of the valve passage 32 is introduced to the back pressure chamber 31c. The main valve element 22 receives back pressure, which is the hydraulic pressure in the back pressure chamber 31c, in one first direction (i.e., the closing direction that closes the valve passage 32). More specifically, the main valve element 22 includes a feedback flow path 22a, and the upstream pressure of the valve passage 32 is introduced to the back pressure chamber 31c via the feedback flow path 22a and the annular passage portion 31d. The feedback flow path 22a introduces hydraulic fluid from the first passage portion 32a to the back pressure chamber 31c. More specifically, the feedback flow path 22a includes an internal passage portion 22b and a plurality of side notches 22c.

[0039] The internal passage portion 22b is formed inside the main valve element 22 and is connected to the first passage portion 32a. More specifically, the main valve element 22 has a tip portion protruding from the valve seat 33 toward the first passage portion 32a, and the internal passage portion 22b is connected to the first passage portion 32a at the tip side of the main valve element 22. Therefore, hydraulic fluid is guided from the first passage portion 32a to the internal passage portion 22b. A plurality of side notches 22c are arranged at intervals in the middle of the outer circumferential surface of the main valve element 22 and are connected to the internal passage portion 22b. Each of the side notches 22c is arranged corresponding to the annular passage portion 31d and is connected to the back pressure chamber 31c via the annular passage portion 31d.

[0040] The check valve element 24 opens and closes the feedback flow path 22a. More specifically, the check valve element 24 is slidably disposed within the main valve element 22. A check valve seat 22e is formed in the internal passage portion 22b. The check valve element 24 closes the feedback flow path 22a by seating on the check valve seat 22e (see FIG. 3), and opens the feedback flow path 22a by moving away from the check valve seat 22e (see FIG. 4). The check valve element 24 receives the hydraulic pressure of the hydraulic fluid flowing from the first passage portion 32a to the back pressure chamber 31c, and is urged toward the check valve seat 22e against this hydraulic pressure. As a result, the check valve element 24 allows the hydraulic fluid to flow from the first passage portion 32a to the back pressure chamber 31c and prevents the hydraulic fluid from flowing in the reverse direction.

[0041] The main valve spring member 25 biases the main valve element 22 toward the closed position. More specifically, the main valve spring member 25 is a compression coil spring. The main valve spring member 25 is accommodated in a compressed state in the back pressure chamber 31c. In this embodiment, the back pressure chamber 31c is blocked by the second housing portion 21b. The main valve spring member 25 abuts against the second housing portion 21b and the main valve element 22, and is accommodated in the back pressure chamber 31c in a compressed state. As a result, the main valve element 22 is biased in the closing direction, i.e., toward the valve seat 33.

[0042] [Spool valve] As described above, the spool valve 17 includes the second housing portion 21b, the spool 23, the electric device 26, and the spool spring member 27. The second housing portion 21b is provided in the first housing portion 21a. More specifically, the second housing portion 21b is provided in the first housing portion 21a so as to close the valve hole 31. The second housing portion 21b has a spool hole 35 and a discharge flow path 36, as shown in FIG. 4.

[0043] The spool hole 35 accommodates the spool 23 so that it can move. In this embodiment, the spool hole 35 extends in the second direction in the second housing portion 21b. The second direction is, for example, a direction perpendicular to the first direction, and is the direction in which the axis L2 of the spool 23, which will be described in detail later, extends, i.e., the axial direction. The spool hole 35 also penetrates the second housing portion 21b in the second direction. One side of the spool hole 35 in the second direction is blocked by the spring receiving portion 28, and the other side in the second direction is blocked by the electric device 26. The spool hole 35 also has a communication hole portion 35a. The communication hole portion 35a is located in an intermediate portion of the spool hole 35. The communication hole portion 35a is formed with a smaller diameter than the inlet-side space 35b and the outlet-side space 35c adjacent to it in the second direction. The inlet-side space 35b and the outlet-side space 35c are connected to an inlet-side flow path portion 36a and an outlet-side flow path portion 36b of a discharge flow path 36, which will be described in detail later, respectively.

[0044] The discharge flow path 36 is connected to the back pressure chamber 31c. The discharge flow path 36 is also connected to the tank 15. More specifically, as described above, the first housing portion 21a has the tank passage 34, and the discharge flow path 36 is connected to the tank 15 via the tank passage 34. The discharge flow path 36 has a spool hole 35 interposed therebetween. More specifically, the discharge flow path 36 has an inlet-side flow path portion 36a and an outlet-side flow path portion 36b. The inlet-side flow path portion 36a is connected to the back pressure chamber 31c, and the outlet-side flow path portion 36b is connected to the tank 15 via the tank passage 34. The inlet-side flow path portion 36a and the outlet-side flow path portion 36b are each connected to the spool hole 35, more specifically, to the inlet-side space 35b and the outlet-side space 35c, respectively. That is, the inlet-side flow passage portion 36a is connected to the spool hole 35 and the back pressure chamber 31c, and the outlet-side flow passage portion 36b is connected to the spool hole 35 and the tank 15.

[0045] As shown in FIG. 5 , the spool 23 is inserted into the spool hole 35 so as to be able to move. More specifically, the spool 23 moves between a closed position that closes the discharge flow path 36 and an open position that opens the discharge flow path 36. That is, the spool 23 opens and closes the discharge flow path 36 by moving its stroke. More specifically, the spool 23 moves its stroke to open and close the inlet-side flow path 36a and the outlet-side flow path 36b. In addition, in the open position, the spool 23 controls the opening degree of the discharge flow path 36 by an amount corresponding to the stroke amount. In this embodiment, when the spool 23 moves its stroke, it adjusts the opening degree between the inlet-side flow path 36a and the outlet-side flow path 36b by an amount corresponding to the stroke amount.

[0046] More specifically, the spool 23 has a land portion 23a. The land portion 23a has a larger diameter than the portions on both sides in the second direction. The outer diameter of the land portion 23a matches the diameter of the communication hole 35a. When the spool 23 is in the closed position, the land portion 23a fits into the communication hole 35a, thereby closing the gap between the inlet-side flow passage 36a and the outlet-side flow passage 36b. Furthermore, as the spool 23 strokes in one direction in the second direction, the inlet-side flow passage 36a and the outlet-side flow passage 36b are eventually connected via the notches 23b and 23c, which will be described in detail later. Further strokes of the spool 23 cause the land portion 23a to disengage from the communication hole 35a, thereby connecting the inlet-side flow passage 36a and the outlet-side flow passage 36b via the communication hole 35a. As the land portion 23a moves away from the communication hole portion 35a, the opening between the inlet-side channel portion 36a and the outlet-side channel portion 36b increases.

[0047] The spool 23 also has a plurality of notches 23b, 23c. In this embodiment, the spool 23 has two first notches 23b and two second notches 23c. The four notches 23b, 23c connect the inlet-side flow passage portion 36a and the outlet-side flow passage portion 36b when switching from the closed position to the open position. More specifically, the four notches 23b, 23c connect the inlet-side space 35b and the outlet-side space 35c. The four notches 23b, 23c are formed in the land portion 23a of the spool 23 and are alternately arranged at intervals from one another in the circumferential direction in this embodiment.

[0048] The first notch 23b is formed in a passage shape. More specifically, as shown in FIG. 6, the first notch 23b has two inlet-side portions 23d and 23e and an outlet-side portion 23f. The inlet-side portions 23d and 23e connect to the inlet-side flow passage portion 36a of the discharge flow passage 36 when the spool 23 is switched from the closed position to the open position. That is, the inlet-side portions 23d and 23e are formed on the outer peripheral surface of the land portion 23a and are positioned and blocked by the communication hole portion 35a in the closed position. When the spool 23 is switched from the closed position to the open position, the inlet-side portions 23d and 23e exit the communication hole portion 35a and open to the inlet-side space 35b. The inlet-side portions 23d and 23e configured in this manner extend, for example, in a direction perpendicular to the second direction of the spool 23. More specifically, the first inlet portion 23d extends in the radial direction of the spool 23, and the second inlet portion 23e extends in a direction intersecting the first inlet portion 23d when viewed in the second direction. The two inlet portions 23d, 23e are arranged, for example, in a V-shape. The outlet portion 23f extends in the second direction. The outlet portion 23f is arranged at the intersection of the two inlet portions 23d, 23e. That is, the waste liquid flows into the outlet portion 23f via the two inlet portions 23d, 23e. The second notch 23c is a groove extending in the second direction and formed on the outer peripheral surface of the spool 23. This ensures a sufficient flow rate of waste liquid flowing from the inlet-side channel portion 36a to the outlet-side channel portion 36b when switching from the closed position to the open position.

[0049] The electric device 26 strokes the spool 23 to adjust the opening of the discharge flow path 36. More specifically, the electric device 26 is attached to the second housing portion 21b so as to close the opening on the other side of the spool hole 35 in the second direction. The electric device 26 is an electrically driven linear motion device that applies a load to the spool 23 according to the energized state, thereby stroking the spool 23 in one direction in the second direction. The electric device 26 is, for example, a linear motion solenoid and a ball screw motor. In this embodiment, the electric device 26 is a linear motion solenoid.

[0050] The spool spring member 27 biases the spool 23 in the other second direction. More specifically, the spool spring member 27 biases the spool 23 against the load from the electric device 26. The spool spring member 27 is, for example, a compression coil spring. The spool spring member 27 is housed in a compressed state on one side of the spool hole 35 in the second direction. As a result, the spool 23 is biased in the other second direction by the spool spring member 27.

[0051] [Operation of the first poppet valve device] In the first poppet valve device 1, when the electric device 26 of the spool valve 17 is energized, the following operation occurs. That is, in the spool valve 17, the spool 23 strokes in one direction in the second direction, opening the gap between the inlet-side flow path 36a and the outlet-side flow path 36b. This causes pressurized fluid in the back pressure chamber 31c of the poppet valve 16 to flow from the inlet-side flow path 36a to the outlet-side flow path 36b and then to be discharged to the tank 15 via the tank passage 34 (see FIG. 4). Meanwhile, in the poppet valve 16, the discharge of pressurized fluid from the back pressure chamber 31c opens the feedback flow path 22a, which had been closed by the check valve element 24 (see FIG. 3). As a result, the working fluid in the first passage portion 32a of the valve passage 32 is guided to the back pressure chamber 31c via the feedback flow path 22a, the annular passage 31d, and the gap between the main valve element 22 and the valve hole 31 (see the bold line in FIG. 3). At this time, a pressure loss occurs in the side notch 22c, so the pressure in the back pressure chamber 31c, i.e., the back pressure, is reduced, and the main valve element 22 lifts to a position where the back pressure, the upstream pressure of the valve passage 32, and the biasing force of the main valve spring member 25 are balanced.

[0052] The back pressure is a pressure that corresponds to the ratio of the opening area of ​​the side notch 22c to the degree of opening between the inlet-side flow passage 36a and the outlet-side flow passage 36b. Therefore, the main valve element 22 lifts by a lift amount that corresponds to the ratio of the opening area of ​​the side notch 22c to the degree of opening between the inlet-side flow passage 36a and the outlet-side flow passage 36b. The degree of opening between the inlet-side flow passage 36a and the outlet-side flow passage 36b is controlled according to the energization state of the electric device 26 of the spool valve 17 (i.e., the energization state of the spool valve 17), so the main valve element 22 lifts by a lift amount that corresponds to the energization state of the spool valve 17. Therefore, in the first poppet valve device 1, the flow rate through the valve passage 32 can be controlled to a flow rate that corresponds to the energization state of the spool valve 17.

[0053] [Second poppet valve device] The second poppet valve device 2 shown in Figure 7 has a similar configuration to the first poppet valve device 1. Therefore, the configuration of the second poppet valve device 2 will be mainly described in terms of differences from the first poppet valve device 1, and the same components will be assigned the same reference numerals and descriptions thereof will be omitted.

[0054] The second poppet valve device 2 includes a housing 21A, a main valve element 22A, and a spool 23. Explaining in more detail, the poppet valve device 1 further includes a check valve element 24, a main valve spring member 25, an electric device 26, and a spool spring member 27. The poppet valve 16A is made up of a portion of the housing 21A (a first housing portion 21Aa, which will be described in detail later), the main valve element 22A, the check valve element 24, and the main valve spring member 25. On the other hand, the spool valve 17 is made up of a portion of the housing 21A (a second housing portion 21b, which will be described in detail later), the spool 23, the electric device 26, and the spool spring member 27.

[0055] The housing 21A includes a valve hole 31, a valve passage 32A, a valve seat 33, a connecting passage 34A, a spool hole 35, and a discharge passage 36. More specifically, the housing 21 has a first housing portion 21Aa that constitutes the poppet valve 16A, and a second housing portion 21b that constitutes the spool valve 17. The first housing portion 21a includes the valve hole 31, the valve passage 32A, the valve seat 33, and the connecting passage 34A.

[0056] As shown in FIG. 8 , the valve passage 32A is formed in the first housing portion 21a with the valve hole 31 interposed therebetween. More specifically, the valve passage 32A includes a first passage portion 32Aa and a second passage portion 32Ab. The first passage portion 32Aa opens at the inner circumferential surface of the bottom portion of the valve hole 31 and is connected to the valve hole 31. On the other hand, the second passage portion 32Ab is connected to the valve hole 31 via a valve port 31a. In this embodiment, the second passage portion 32Ab extends in a first direction from the valve port 31a. In the valve passage 32A configured in this manner, for example, the rod-side passage 12 or the head-side passage 13 is connected to the first passage portion 32Aa, and the tank 15 is connected to the second passage portion 32Ab via a downstream-side passage 14. Therefore, in the valve passage 32A, the hydraulic fluid flows from the first passage portion 32Aa through the valve hole 31 to the second passage portion 32Ab.

[0057] The connection passage 34A is connected to the discharge flow passage 36 (more specifically, the outlet-side flow passage portion 36b) of the second housing portion 21b. The connection passage 34A is also connected to the tank 15, and discharges the waste liquid discharged to the outlet-side flow passage portion 36b to the tank 15. More specifically, the connection passage 34A is connected to the second passage portion 32Ab. Therefore, the waste liquid discharged to the outlet-side flow passage portion 36b is discharged to the tank 15 via the connection passage 34A and the second passage portion 32Ab. Therefore, the pressure of the waste liquid discharged to the connection passage 34A also becomes the tank pressure.

[0058] The main valve element 22A is movably mounted in the valve hole 31. The main valve element 22A opens and closes the valve passage 32A by stroking, and adjusts the opening degree of the valve passage 32A depending on its position. The main valve element 22A also defines a back pressure chamber 31c in the valve hole 31 and includes a feedback flow path 22Aa that directs the upstream pressure of the valve passage 32 to the back pressure chamber 31c. The feedback flow path 22Aa directs the working fluid from the first passage portion 32Aa to the back pressure chamber 31c. More specifically, the feedback flow path 22Aa has an internal passage portion 22Ab and multiple side notches 22c.

[0059] The internal passage 22Ab is formed inside the main valve element 22A and is connected to the first passage portion 32Aa. More specifically, the valve hole 31 has a larger diameter on the valve seat 33 side, forming an annular space 31b. The annular space 31b is an annular space surrounding the main valve element 22A and is connected to the first passage portion 32Aa. The internal passage 22Ab opens at a position on the outer circumferential surface of the main valve element 22A corresponding to the annular space 31b and is connected to the first passage portion 32Aa via the annular space 31b. Therefore, hydraulic fluid is guided from the first passage portion 32Aa to the internal passage 22b.

[0060] [Operation of the second poppet valve device] In the second poppet valve device 2, when the electric device 26 of the spool valve 17 is energized, the second poppet valve device 2 operates as follows. That is, in the spool valve 17, the spool 23 strokes in one direction, opening the gap between the inlet-side flow path 36a and the outlet-side flow path 36b. Pressurized fluid in the back pressure chamber 31c of the poppet valve 16A flows from the inlet-side flow path 36a to the outlet-side flow path 36b, and is then discharged to the tank 15 via the connecting passage 34A and the second passage portion 32Ab. This causes the check valve 24 to open the feedback flow path 22Aa, and hydraulic fluid in the first passage portion 32Aa of the valve passage 32A is guided to the back pressure chamber 31c via the feedback flow path 22Aa, the annular passage portion 31d, and the gap between the main valve element 22A and the valve hole 31 (see the bold line in FIG. 8 ). As a result, the main valve element 22A lifts by an amount corresponding to the energized state of the spool valve 17, similar to the first poppet valve device 1. Therefore, in the second poppet valve device 2, the flow rate through the valve passage 32A can be controlled to a flow rate corresponding to the energized state of the spool valve 17 (see the dashed line in FIG. 8).

[0061] In the poppet valve devices 1 and 2 of the present embodiment, the discharge flow path 36 is connected to the tank 15. Therefore, the back pressure in the back pressure chamber 31c can be stabilized regardless of the pressure difference between the upstream and downstream pressures of the valve passages 32 and 32A. This improves the controllability of the flow rate in the poppet valve devices 1 and 2.

[0062] Furthermore, in the first poppet valve device 1 of this embodiment, the discharge flow path 36 is connected to the tank 15 via the tank passage 34. Therefore, the hydraulic pressure in the discharge flow path 36 can be maintained at the tank pressure, which further suppresses fluctuations in the back pressure in the back pressure chamber 31c. Therefore, the controllability of the flow rate in the poppet valve device 1 can be further improved.

[0063] Furthermore, in the second poppet valve device 2 of this embodiment, the discharge flow path 36 is connected to the tank 15 via the second passage portion 32Ab. Therefore, the discharge flow path 36 can be easily connected to the tank 15, which simplifies the configuration of the second poppet valve device 2.

[0064] Furthermore, the poppet valve devices 1 and 2 of the present embodiment further include an electric device 26 that strokes the spool 23 to control the opening degree of the discharge flow path 36. This reduces the cost of the poppet valve devices 1 and 2 and improves the flexibility of layout.

[0065] Furthermore, in the poppet valve device 1, 2 of this embodiment, the first notch 23b has inlet-side portions 23d, 23e and outlet-side portions 23f, and the inlet-side portions 23d, 23e extend in a direction perpendicular to the second direction. Therefore, the wastewater flowing from the inlet-side flow passage 36a into the inlet-side portions 23d, 23e can flow radially. This reduces the flow force in the second direction that the spool 23 receives from the wastewater flowing through the first notch 23b.

[0066] Furthermore, in the poppet valve devices 1 and 2 of the present embodiment, the second notch 23c is a groove extending in the second direction on the outer circumferential surface of the spool 23. Therefore, it is possible to ensure the flow rate of the drained liquid flowing from the inlet-side flow path portion 36a to the outlet-side flow path portion 36b when switching from the closed position to the open position.

[0067] In the poppet valve device 1 of this embodiment, the first poppet valve device 1 is applied to the meter-in control valve devices 6R, 6H, and the second poppet valve device 2 is applied to the meter-out control valve devices 7R, 7H. Therefore, the cost of the hydraulic drive system 3 can be reduced.

[0068] <Other embodiments> In the hydraulic drive system 3 of this embodiment, the first poppet valve device 1 is applied to the meter-in control valve devices 6R, 6H, and the second poppet valve device 2 is applied to the meter-out control valve devices 7R, 7H, but this configuration is not necessarily required. For example, the second poppet valve device 2 may be applied to the meter-in control valve devices 6R, 6H, and the first poppet valve device 1 may be applied to the meter-out control valve devices 7R, 7H, or the first poppet valve device 1 or the second poppet valve device 2 may be applied to all of the control valve devices 6R, 6H, 7R, 7H. Furthermore, it is sufficient that the poppet valve device 1, 2 is applied to at least one of the control valve devices 6R, 6H, 7R, 7H, and the others may be configured as spool valve devices.

[0069] Furthermore, in the poppet valve devices 1 and 2 of the present embodiment, the electric device 26 is used as the drive device for stroking the spool 23, but a hydraulic drive device may also be used. The hydraulic drive device includes, for example, a proportional valve, and strokes the spool 23 using pilot pressure output from the proportional valve. The proportional valve outputs pilot pressure according to its energized state, and the spool 23 strokes to a position according to the pilot pressure, i.e., controls the opening of the discharge flow path 36. As a result, the poppet valve devices 1 and 2 can operate in the same way even when a hydraulic drive device is used as the drive device.

[0070] Furthermore, in the poppet valve devices 1 and 2 of this embodiment, the spool 23 is formed with first notches 23b to reduce the flow force. However, this may be configured as the spool valve 17B of the poppet valve devices 1B and 2B shown in FIG. 9. That is, in the spool valve 17B, the housing 21B further includes a sleeve 41. The sleeve 41 is inserted into the spool hole 35. The sleeve 41 has a plurality of inlet-side through passages 41a and a plurality of outlet-side through passages 41b. The inlet-side through passages 41a penetrate the sleeve 41 radially and are connected to the inlet-side flow passage portion 36a. The outlet-side through passages 41b also penetrate the sleeve 41 radially and are connected to the outlet-side flow passage portion 36b. In this embodiment, four inlet-side through passages 41a and four outlet-side through passages 41b are formed in the sleeve 41, and are arranged at equal intervals in the circumferential direction of the sleeve 41. More specifically, an inlet-side annular groove 41c and an outlet-side annular groove 41d are formed on the outer peripheral surface of the sleeve 41. The inlet-side annular groove 41c is disposed on the outer peripheral surface of the sleeve 41 at a position corresponding to the inlet-side flow passage portion 36a and extends over the entire circumferential direction. The four inlet-side through passages 41a are connected to the inlet-side flow passage portion 36a via the inlet-side annular groove 41c. The outlet-side annular groove 41d is disposed on the outer peripheral surface of the sleeve 41 at a position corresponding to the outlet-side flow passage portion 36b and extends over the entire circumferential direction. The four outlet-side through passages 41b are connected to the outlet-side flow passage portion 36b via the outlet-side annular groove 41d.

[0071] Furthermore, the spool 23B is slidably inserted through the sleeve 41. In the closed position, the spool 23B blocks the inlet-side through passage 41a with the land portion 23Ba. Therefore, the discharge flow passage 36 is closed. On the other hand, the inlet-side through passage 41a is opened by the spool 23B stroking in one direction in the second direction toward the open position. This opens the discharge flow passage 36. The outlet-side flow passage 36b is disposed on the other side of the second direction relative to the inlet-side flow passage 36a, i.e., the outlet-side through passage 41b is disposed on the other side of the second direction relative to the inlet-side through passage 41a. Therefore, the discharged liquid flows through the sleeve 41 in the other side of the second direction.

[0072] On the other hand, the inlet-side through-passage 41a is inclined toward one side of the second direction as it advances radially in the sleeve 41. That is, the inlet-side through-passage 41a is inclined in the same direction as the spool 23 strokes from the closed position to the open position. Therefore, when the wastewater flows from the inlet-side through-passage 41a into the sleeve 41, it flows in one side of the second direction. That is, the direction of the wastewater flowing from the inlet-side through-passage 41a into the sleeve 41 can be made opposite to the direction of the wastewater flowing through the sleeve 41. This suppresses the flow rate of the wastewater flowing through the sleeve 41 and reduces the flow force acting on the spool 23. The outlet-side through-passage 41b is also inclined toward one side of the second direction as it advances radially in the sleeve 41. However, the inlet-side through-passage 41a and the outlet-side through-passage 41b do not necessarily have to be configured as described above.

[0073] In the poppet valve devices 1B and 2B of the above-described embodiments, the spool 23 strokes in one second direction within the sleeve 41 from the open position toward the open position, and the inlet-side through-passage 41a is inclined in one second direction as it advances in the radial direction. This allows the flow direction of the waste liquid flowing from the inlet-side through-passage 41a into the sleeve 41 to be opposite to the direction of the waste liquid flowing within the sleeve 41. This reduces the flow force that the spool 23 receives from the waste liquid.

[0074] Although the poppet valve devices 1, 1B, 2, and 2B each include the first notch 23b and the sleeve 41 to reduce the flow force, these are not necessarily required. Furthermore, in the poppet valve device 1 of this embodiment, the discharge flow path 36 is connected to the tank 15 via the tank passage 34, but this is not necessarily required. The discharge flow path 36 may be connected to the first passage portion 32a, for example. Even in this case, the poppet valve device achieves the same effects as those described above due to the first notch 23b and the sleeve 41.

[0075] Furthermore, in the hydraulic drive system 3 of this embodiment, the control device 9 may control the aperture of each control valve device 6R, 6H, 7R, 7H in response to the differential pressure between the upstream and downstream pressures of the valve passages 32, 32A in addition to the amount of operation of the operating device 8a. More specifically, pressure sensors are provided in the first passage portions 32a, 32Aa and the second passage portions 32b, 32Ab of the valve passages 32, 32A, respectively, and the control device 9 calculates the differential pressure in response to the pressures acquired by the pressure sensors. The control device 9 has a map showing the relationship between the amount of operation of the operating device 8a and the aperture (or energization state) for each differential pressure, for example, and calculates the aperture (or energization state) based on the calculated map and the amount of operation of the operating device 8a. The hydraulic drive system 3 configured in this manner can more accurately control the meter-in flow rate or meter-out flow rate. Furthermore, the control device 9 may calculate and control the aperture of each control valve device 6R, 6H, 7R, 7H in accordance with a program.

[0076] Exemplary Embodiments A poppet valve device in a first aspect includes a housing including a valve passage, a valve seat interposed in the valve passage, a valve hole having a back pressure chamber to which upstream pressure of the valve passage is directed, and a discharge passage connected to the back pressure chamber; a poppet valve element accommodated in the valve hole so as to be able to seat on and leave the valve seat, which strokes in response to the back pressure of the back pressure chamber and opens the valve passage at an opening degree corresponding to the stroke amount; and a spool which adjusts the back pressure by controlling the opening degree of the discharge passage, and the discharge passage is connected to a tank.

[0077] According to the above aspect, the exhaust passage is connected to the tank. Therefore, the back pressure in the back pressure chamber can be stabilized regardless of the pressure difference between the upstream and downstream pressures of the valve passage. This improves the controllability of the flow rate in the poppet valve device.

[0078] In a second aspect of the poppet valve device, in the poppet valve device of the first aspect, the housing further includes a tank passage connected to the tank, and the discharge flow path is connected to the tank via the tank passage.

[0079] According to the above aspect, the discharge flow path is connected to the tank via the tank passage. Therefore, the hydraulic pressure in the discharge flow path can be maintained at the tank pressure, and fluctuations in the back pressure in the back pressure chamber can be further suppressed. Therefore, the controllability of the flow rate in the poppet valve device can be further improved.

[0080] In a third aspect, in the poppet valve device of the first or second aspect, the valve passage has a first passage portion located upstream of the valve seat and a second passage portion located downstream of the valve seat and connected to the tank, and the discharge flow path is connected to the tank via the second passage portion.

[0081] According to the above aspect, the discharge flow path is connected to the tank via the second passage portion. Therefore, the discharge flow path can be easily connected to the tank, and the poppet valve device can be easily configured.

[0082] In a fourth aspect, the poppet valve device is the poppet valve device of any one of the first to third aspects, further comprising an electric device that strokes the spool to adjust the opening of the discharge flow path.

[0083] According to the above aspect, an electric device is further provided that strokes the spool to control the opening degree of the exhaust flow path, thereby reducing the cost of the poppet valve device and improving the degree of freedom in layout.

[0084] In a fifth aspect, in the poppet valve device of any one of the first to fourth aspects, the housing has a spool hole that is interposed in the discharge flow path and through which the spool is inserted so as to be movable in the axial direction, the discharge flow path has an inlet-side flow path portion that is connected to the back pressure chamber and the spool hole, and an outlet-side flow path portion that is connected to the spool hole and the tank, the spool has a first notch that connects the inlet-side flow path portion and the outlet-side flow path portion when the spool switches from a closed position that closes the discharge flow path to an open position that opens the discharge flow path, the first notch having an inlet-side portion that connects to the inlet-side flow path portion when switched and an outlet-side portion that connects to the outlet-side flow path portion, the inlet-side portion extending in a direction perpendicular to the axial direction, and the outlet-side portion extending in the axial direction.

[0085] According to the above aspect, the first notch has an inlet-side portion and an outlet-side portion, and the inlet-side portion extends in a direction perpendicular to the axial direction. Therefore, wastewater flowing from the inlet-side flow path into the inlet-side portion can flow in a direction perpendicular to the axial direction. This reduces the axial flow force that the spool receives from wastewater flowing through the first notch.

[0086] In a sixth aspect, the poppet valve device is the poppet valve device of the fifth aspect, wherein the spool has a second notch that connects the inlet-side flow path portion and the outlet-side flow path portion when switching from a closed position to an open position, and the second notch is a groove that extends in the axial direction on the outer peripheral surface of the spool.

[0087] According to the above aspect, the second notch is a groove extending in the axial direction on the outer peripheral surface of the spool, which ensures a sufficient flow rate of the waste liquid flowing from the inlet-side flow path to the outlet-side flow path when switching from the closed position to the open position.

[0088] In a seventh aspect, in the poppet valve device of any one of the first to sixth aspects, the housing further includes a spool hole interposed in the discharge flow passage, and a sleeve inserted into the spool hole and into which the spool is inserted so as to be able to stroke, the discharge flow passage has an inlet-side flow passage portion connected to the back pressure chamber and the spool hole, and an outlet-side flow passage portion connected to the spool hole and the tank, the sleeve has an inlet-side through passage connected to the inlet-side flow passage portion and penetrating therethrough in the radial direction, and an outlet-side through passage connected to the outlet-side flow passage portion and penetrating therethrough in the radial direction, the spool strokes in one axial direction within the sleeve from an open position that closes the discharge flow passage to an open position that opens the discharge flow passage, and the inlet-side through passage is inclined in one axial direction as it progresses in the radial direction.

[0089] According to the above aspect, the spool strokes in one axial direction within the sleeve from an open position that closes the discharge flow path to an open position that opens the discharge flow path, and the inlet-side through-passage is inclined in one axial direction as it advances in the radial direction. This allows the flow direction of the waste liquid flowing from the inlet-side through-passage into the sleeve to be opposite to the flow direction of the waste liquid flowing in the other axial direction within the sleeve. This reduces the flow force that the spool receives from the waste liquid.

[0090] A hydraulic drive system in an eighth aspect is a hydraulic drive system that controls the flow of hydraulic fluid from a pump to two ports of a hydraulic actuator, and includes a first meter-in control valve device that controls the flow rate of hydraulic fluid supplied to one port of the hydraulic actuator, a first meter-out control valve device that controls the flow rate of hydraulic fluid discharged from the one port, a second meter-in control valve device that controls the flow rate of hydraulic fluid supplied to the other port of the hydraulic actuator, and a second meter-out control valve device that controls the flow rate of hydraulic fluid discharged from the other port, and at least one of the first meter-in control valve device, the first meter-out control valve device, the second meter-in control valve device, and the second meter-out control valve device is the poppet valve device of any of the first to seventh aspects.

[0091] According to the above aspect, at least one of the first meter-in control valve device, the first meter-out control valve device, the second meter-in control valve device, and the second meter-out control valve device is the poppet valve device, thereby reducing the cost of the hydraulic drive system.

[0092] A poppet valve device according to a ninth aspect includes a housing including a valve passage, a valve seat disposed in the valve passage, a valve hole having a back pressure chamber to which an upstream pressure of the valve passage is introduced, a discharge passage connected to the back pressure chamber, and a spool hole disposed in the discharge passage; a poppet valve element accommodated in the valve hole so as to be able to seat on and separate from the valve seat, which strokes in response to the back pressure of the back pressure chamber and opens the valve passage at an opening degree in accordance with the stroke amount; and a spool hole inserted in the axial direction so as to be able to stroke, which controls the opening degree of the discharge passage by stroking, thereby adjusting the back pressure. the discharge flow path has an inlet-side flow path portion connected to the back pressure chamber and the spool hole, and an outlet-side flow path portion connected to the spool hole, the spool has a first notch that connects the inlet-side flow path portion and the outlet-side flow path portion when the spool switches from a closed position that closes the discharge flow path to an open position that opens the discharge flow path, the first notch having an inlet-side portion that connects to the inlet-side flow path portion when switched, and an outlet-side portion that connects to the outlet-side flow path portion, the inlet-side portion extending in a direction perpendicular to the axial direction, and the outlet-side portion extending in the axial direction.

[0093] According to the above aspect, the first notch has an inlet-side portion and an outlet-side portion, and the inlet-side portion extends in a direction perpendicular to the axial direction. Therefore, wastewater flowing from the inlet-side flow path into the inlet-side portion can flow in a direction perpendicular to the axial direction. This reduces the axial flow force that the spool receives from wastewater flowing through the first notch.

[0094] A poppet valve device according to a tenth aspect of the present invention comprises a housing including a valve passage, a valve seat disposed in the valve passage, a valve hole having a back pressure chamber to which an upstream pressure of the valve passage is introduced, a discharge passage connected to the back pressure chamber, a spool hole disposed in the discharge passage, and a sleeve inserted into the spool hole; a poppet valve element accommodated in the valve hole so as to be able to seat on and separate from the valve seat, which strokes in response to the back pressure of the back pressure chamber and opens the valve passage at an opening degree in accordance with the stroke amount; and a poppet valve element inserted in the sleeve so as to be able to stroke, which controls the opening degree of the discharge passage by stroking to discharge the back pressure. and a spool for adjusting the length of the exhaust passage, the exhaust passage having an inlet-side passage portion connected to the back pressure chamber and the spool hole, and an outlet-side passage portion connected to the spool hole, the sleeve having an inlet-side through passage that is connected to the inlet-side passage portion and penetrates radially, and an outlet-side through passage that is connected to the outlet-side passage portion and penetrates radially, the spool strokes in one axial direction within the sleeve from an open position that closes the exhaust passage to an open position that opens the exhaust passage, and the inlet-side through passage is inclined in one axial direction as it progresses radially.

[0095] According to the above aspect, the spool strokes in one axial direction within the sleeve from an open position that closes the discharge flow path to an open position that opens the discharge flow path, and the inlet-side through-passage is inclined in one axial direction as it advances in the radial direction. This allows the flow direction of the waste liquid flowing from the inlet-side through-passage into the sleeve to be opposite to the flow direction of the waste liquid flowing in the other axial direction within the sleeve. This reduces the flow force that the spool receives from the waste liquid. [Explanation of symbols]

[0096] 1,1B First poppet valve device 2,2B Second poppet valve device 3 Hydraulic drive system 4 Hydraulic Actuators 4a Rod side port 4b Head side port 5 Hydraulic Pump 6R First meter-in control valve device 6H Second meter-in control valve device 7R First meter-out control valve device 7H Second meter-out control valve device 15 Tank 21, 21A, 21B Housing 22, 22A Main valve body (poppet valve body) 23,23B spool 23b First notch 23c 2nd notch 23d,23e Entrance side part 23f Exit side part 26 Electric equipment 31 Valve orifice 31c Back pressure chamber 32 Valve passage 32a,32Aa 1st passage section 32b,32Ab 2nd passage section 33 Valve seat 34 Tank Passage 35 spool holes 36 Discharge flow path 36a Inlet side channel section 36b Outlet side flow path section 41 Sleeve 41a Entrance side passageway 41b Exit side passageway

Claims

1. a housing including a valve passage, a valve seat interposed in the valve passage, a valve hole having a back pressure chamber to which upstream pressure of the valve passage is introduced, and a discharge flow path connected to the back pressure chamber; a poppet valve element that is accommodated in the valve hole and can be seated on and released from the valve seat, that strokes in response to the back pressure in the back pressure chamber, and that opens the valve passage by an opening amount corresponding to the stroke amount; a spool that adjusts the back pressure by controlling the opening of the discharge flow path, The poppet valve device wherein the discharge passage is connected to a tank.

2. the housing further includes a tank passage connected to the tank; The poppet valve device according to claim 1 , wherein the discharge passage is connected to the tank via the tank passage.

3. the valve passage has a first passage portion located upstream of the valve seat and a second passage portion located downstream of the valve seat and connected to the tank, 2. The poppet valve assembly according to claim 1, wherein the discharge passage is connected to the tank via the second passage portion.

4. The poppet valve device according to claim 1 , further comprising an electric device that strokes the spool to adjust the opening of the discharge passage.

5. the housing has a spool hole interposed in the discharge flow path and through which the spool is inserted so as to be capable of moving in the axial direction; the discharge flow path has an inlet-side flow path portion connected to the back pressure chamber and the spool hole, and an outlet-side flow path portion connected to the spool hole and the tank, the spool has a first notch that connects the inlet-side flow path portion and the outlet-side flow path portion when switching from a closed position that closes the discharge flow path to an open position that opens the discharge flow path, the first notch has an inlet-side portion that connects to the inlet-side flow path portion when switching, and an outlet-side portion that connects to the outlet-side flow path portion, The inlet side portion extends in a direction perpendicular to the axial direction, The poppet valve assembly of claim 1 , wherein the outlet portion extends axially.

6. the spool has a second notch that connects the inlet-side flow path portion and the outlet-side flow path portion when switching from the closed position to the open position; 6. The poppet valve assembly of claim 5, wherein the second notch is a groove extending axially in the outer peripheral surface of the spool.

7. the housing further includes a spool hole interposed in the discharge flow path, and a sleeve inserted into the spool hole and into which the spool is inserted so as to be capable of being stroked; the discharge flow path has an inlet-side flow path portion connected to the back pressure chamber and the spool hole, and an outlet-side flow path portion connected to the spool hole and the tank, The sleeve has an inlet-side through passage that is connected to the inlet-side flow passage portion and penetrates in a radial direction, and an outlet-side through passage that is connected to the outlet-side flow passage portion and penetrates in a radial direction, the spool strokes in one axial direction within the sleeve from an open position that closes the discharge flow passage to an open position that opens the discharge flow passage, The poppet valve device according to claim 1 , wherein the inlet-side through passage is inclined in one axial direction as it advances in the radial direction.

8. 1. A hydraulic drive system for controlling the flow of hydraulic fluid from a pump to two ports of a hydraulic actuator, comprising: a first meter-in control valve device that controls the flow rate of hydraulic fluid supplied to one port of the hydraulic actuator; a first meter-out control valve device that controls the flow rate of the hydraulic fluid discharged from the one port; a second meter-in control valve device that controls the flow rate of hydraulic fluid supplied to the other port of the hydraulic actuator; a second meter-out control valve device that controls the flow rate of the hydraulic fluid discharged from the other port, 2. A hydraulic drive system, wherein at least one of the first meter-in control valve device, the first meter-out control valve device, the second meter-in control valve device, and the second meter-out control valve device is the poppet valve device according to claim 1.

9. a housing including: a valve passage; a valve seat interposed in the valve passage; a valve hole having a back pressure chamber to which upstream pressure of the valve passage is introduced; a discharge flow path connected to the back pressure chamber; and a spool hole interposed in the discharge flow path; a poppet valve element that is accommodated in the valve hole and can be seated on and released from the valve seat, that strokes in response to the back pressure in the back pressure chamber, and that opens the valve passage by an opening amount corresponding to the stroke amount; a spool that is inserted into the spool hole so as to be able to move in the axial direction and that adjusts the back pressure by controlling the opening degree of the discharge flow path by stroking, the discharge flow path has an inlet-side flow path portion connected to the back pressure chamber and the spool hole, and an outlet-side flow path portion connected to the spool hole, the spool has a first notch that connects the inlet-side flow path portion and the outlet-side flow path portion when switching from a closed position that closes the discharge flow path to an open position that opens the discharge flow path, the first notch has an inlet-side portion that connects to the inlet-side flow path portion when switching, and an outlet-side portion that connects to the outlet-side flow path portion, The inlet side portion extends in a direction perpendicular to the axial direction, The poppet valve device wherein the outlet portion extends in an axial direction.

10. a housing including a valve passage, a valve seat interposed in the valve passage, a valve hole having a back pressure chamber to which upstream pressure of the valve passage is directed, a discharge flow path connected to the back pressure chamber, a spool hole interposed in the discharge flow path, and a sleeve inserted into the spool hole; a poppet valve element that is accommodated in the valve hole and can be seated on and released from the valve seat, that strokes in response to the back pressure in the back pressure chamber, and that opens the valve passage by an opening amount corresponding to the stroke amount; a spool that is inserted into the sleeve so as to be able to stroke, and that adjusts the back pressure by controlling the opening degree of the discharge flow path by stroking; the discharge flow path has an inlet-side flow path portion connected to the back pressure chamber and the spool hole, and an outlet-side flow path portion connected to the spool hole, The sleeve has an inlet-side through passage that is connected to the inlet-side flow passage portion and penetrates in a radial direction, and an outlet-side through passage that is connected to the outlet-side flow passage portion and penetrates in a radial direction, the spool strokes in one axial direction within the sleeve from an open position that closes the discharge flow passage to an open position that opens the discharge flow passage, The poppet valve device, wherein the inlet-side through passage is inclined in one axial direction as it progresses in the radial direction.

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