Valve device and flow rate control device provided with valve device

Abstract

A valve device (10, 510, 710, 810) comprises a solenoid (12), a solenoid proportional reducing valve (20, 720, 820), and a first switching valve (30, 530, 730, 830) that switches from a normal position (D, L, N, P) to a fail position (E, M, O, Q) at the time of failure of the solenoid (12). A valve body of the solenoid proportional reducing valve (20, 720, 820) and a valve body of the first switching valve (30, 530, 730, 830) are integrally constituted by one spool (13, 513, 713, 813).

Description

Valve device and flow control device equipped with valve device

[0001] The present invention relates to a valve device and a flow control device including the valve device.

[0002] JP2018-84196A discloses a pump flow rate control device including a variable displacement pump, a servo piston that changes the tilt angle of the pump, a regulating valve for driving the servo piston, and an electromagnetic proportional valve that outputs a secondary pressure according to a command current. The pump flow rate control device of JP2018-84196A changes the displacement of the variable displacement pump by changing the biasing force applied to the regulating valve by the secondary pressure from the electromagnetic proportional valve.

[0003] Furthermore, JP2018-84196A discloses a pump displacement control device that switches a switching valve to apply the pump discharge pressure to the adjustment valve when a malfunction of the electromagnetic proportional valve occurs due to a disconnection of the electrical system or a failure of the electromagnetic proportional valve (see Figure 4).As a result, the pump displacement control device disclosed in JP2018-84196A is able to perform flow control when a malfunction of the electromagnetic proportional valve occurs, while limiting the pump discharge flow rate when the relationship between the pump discharge pressure and discharge flow rate exceeds a predetermined horsepower control characteristic line.

[0004] However, in the pump displacement control device described in JP2018-84196A, the switching valve and the electromagnetic proportional pressure reducing valve are provided separately, which requires a large space for installing them.

[0005] SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an object to reduce the size of a switching valve and an electromagnetic proportional pressure reducing valve.

[0006] According to one aspect of the present invention, a valve device includes a solenoid, an electromagnetic proportional pressure reducing valve that reduces primary pressure and adjusts it to a secondary pressure that corresponds to a command current applied to the solenoid, and a first switching valve that has a normal position and a fail position that are switchable in response to the biasing force generated by the solenoid and that switches from the normal position to the fail position in the event of a solenoid failure, wherein the valve element of the electromagnetic proportional pressure reducing valve and the valve element of the first switching valve are integrally formed by a single spool, and the first switching valve has an input port to which the primary pressure is directed on the upstream side, an output port on the downstream side, and a drain port that communicates with a tank, and when the first switching valve switches from the normal position to the fail position, communication between the output port and the drain port switches to communication between the output port and the input port, or communication between the output port and the input port switches to communication between the output port and the drain port, thereby changing the pressure on the output port side.

[0007] FIG. 1 is a hydraulic circuit diagram showing the configuration of a pump system including a pump displacement control device according to a first embodiment of the present invention. FIG. 2A is a cross-sectional view showing the main components of the valve system according to the first embodiment of the present invention when a solenoid in the valve system is de-energized. FIG. 2B is a cross-sectional view showing the main components of the valve system according to the first embodiment of the present invention when a solenoid in the valve system is energized. FIG. 2C is a cross-sectional view showing the main components of the valve system according to the first embodiment of the present invention when an electromagnetic proportional pressure reducing valve is at a set pressure. FIG. 3 is a hydraulic circuit diagram of a modified example of the pump displacement control device according to the first embodiment. FIG. 4 is a hydraulic circuit diagram of a modified example of the pump displacement control device according to the first embodiment. FIG. 5 is a hydraulic circuit diagram of a modified example of the pump displacement control device according to the first embodiment. FIG. 6 is a hydraulic circuit diagram showing the configuration of a pump system including a pump displacement control device according to a second embodiment of the present invention. FIG. 7A is a cross-sectional view showing the main components of the valve system according to the second embodiment of the present invention when a solenoid in the valve system is de-energized. FIG. 7B is a cross-sectional view showing the main components of the valve system according to the second embodiment of the present invention when a solenoid in the valve system is energized. FIG. 7C is a cross-sectional view showing a main part of the valve device in a state where the electromagnetic proportional pressure reducing valve is at a set pressure in the valve device according to a second embodiment of the present invention. FIG. 8 is a hydraulic circuit diagram of a modified example of the pump displacement control device according to the second embodiment. FIG. 9 is a hydraulic circuit diagram showing the configuration of a pump device including a pump displacement control device according to a third embodiment of the present invention. FIG. 10A is a cross-sectional view showing a main part of the valve device in a state where the solenoid in the valve device according to a third embodiment of the present invention is de-energized. FIG. 10B is a cross-sectional view showing a main part of the valve device in a state where the solenoid in the valve device according to a third embodiment of the present invention is energized. FIG. 10C is a cross-sectional view showing a main part of the valve device in a state where the electromagnetic proportional pressure reducing valve is at a set pressure in the valve device according to the third embodiment of the present invention. FIG. 11 is a hydraulic circuit diagram showing the configuration of a pump device including a pump displacement control device according to a fourth embodiment of the present invention. FIG. 12A is a cross-sectional view showing a main part of the valve device in a state where the solenoid in the valve device according to the fourth embodiment of the present invention is de-energized.Fig. 12B is a cross-sectional view showing a main part of the valve device in a state where a solenoid is energized in the valve device according to a fourth embodiment of the present invention. Fig. 12C is a cross-sectional view showing a main part of the valve device in a state where the electromagnetic proportional pressure reducing valve is at a set pressure in the valve device according to a fourth embodiment of the present invention. Fig. 13 is a hydraulic circuit diagram of a modified example of the pump displacement control device according to the first embodiment.

[0008] First Embodiment A valve device 10 and a flow control device 100 including the valve device 10 according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2A to 2C.

[0009] FIG. 1 is a hydraulic circuit diagram showing the configuration of a pump unit PU equipped with a flow control device 100 according to a first embodiment. The flow control device 100 according to this embodiment is a device for controlling the displacement (displacement) of a swash plate-type variable displacement pump (pump P) by changing the tilt angle of the pump P. As shown in FIG. 1 , the pump unit PU includes a swash plate-type variable displacement pump P and a flow control device 100 that controls the flow rate of the pump P. The flow control device 100 includes a valve device 10, a flow control unit M that controls the displacement of the pump P, and a high-pressure selection valve 40 serving as a second switching valve that outputs a pressure for switching between enabling and disabling horsepower control (described later). The displacement of the pump P refers to the amount of working fluid discharged per rotation of the pump P. Hereinafter, the displacement of the pump P will be referred to as the "pump displacement."

[0010] The pump unit PU according to this embodiment uses hydraulic oil as the working fluid. However, other working fluids such as hydraulic water or a water-soluble substitute liquid may be used instead of hydraulic oil. The pump unit PU is provided as a pressure source for hydraulic equipment mounted on construction machinery such as a hydraulic excavator.

[0011] The pump P is a swash plate type piston pump whose capacity can be changed according to the tilt angle of the swash plate 2, and is rotationally driven by the power of the engine E serving as a drive source. The pump P draws in hydraulic oil stored in a tank T and discharges the pressurized hydraulic oil (pressurized oil) to a discharge passage 3. The hydraulic oil discharged from the pump P is supplied to hydraulic equipment of the construction machine (not shown). Examples of hydraulic equipment of the construction machine include hydraulic cylinders that drive the boom, arm, and bucket of a hydraulic excavator, and hydraulic motors that drive the crawlers of the hydraulic excavator.

[0012] The construction machine is equipped with a controller C that controls each part of the construction machine. The controller C is connected to an operation sensor 41a as a detection device that detects the amount of operation of an operation lever 41 operated by an operator.

[0013] 1, the valve device 10 includes a solenoid 12, an electromagnetic proportional pressure reducing valve 20 that reduces a primary pressure to adjust it to a secondary pressure corresponding to a command current applied to the solenoid 12, and a first switching valve 30 that is switched to a normal position D or a fail position E according to the biasing force generated by the solenoid 12. The specific configuration of the valve device 10 will be described later.

[0014] The controller C controls the electromagnetic proportional pressure reducing valve 20 based on the detection result of the operation sensor 41 a. The electromagnetic proportional pressure reducing valve 20 reduces the pressure of the hydraulic oil supplied from a hydraulic power source (not shown) in accordance with a command current from the controller C, and outputs the reduced pressure to the flow rate control unit M. In this embodiment, the electromagnetic proportional pressure reducing valve 20 is a direct proportional type electromagnetic proportional pressure reducing valve that outputs a higher secondary pressure as the command current applied to the solenoid 12 increases. Hereinafter, the "secondary pressure" output from the electromagnetic proportional pressure reducing valve 20 will also be referred to as the "input pressure Pi" input to the flow rate control unit M.

[0015] The controller C controls the pump displacement based on the operation amount of the control lever 41 detected by the operation sensor 41 a. A data table of command current values ​​relative to the operation amount of the control lever 41 is stored in the memory of the controller C. The controller C refers to the data table and calculates a command current value relative to the operation amount of the control lever 41. The controller C increases the command current value for the electromagnetic proportional pressure reducing valve 20 as the operation amount of the control lever 41 detected by the operation sensor 41 a increases. In other words, the controller C controls the electromagnetic proportional pressure reducing valve 20 so that the pump displacement increases as the operation amount of the control lever 41 increases, i.e., so that the input pressure Pi to the flow rate control unit M increases. Note that although only one control lever 41 is shown in FIG. 1 , in reality, there are multiple control levers 41. When these multiple control levers 41 are operated simultaneously, the controller C calculates a command current value corresponding to the sum of these operation amounts.

[0016] The flow control unit M includes a flow control mechanism M1 for performing flow control that controls the pump capacity based on the input pressure Pi, a horsepower control mechanism M2 for performing horsepower control that controls the pump capacity based on the discharge pressure Pout of the pump P, a locking mechanism 50 that switches the control by the horsepower control mechanism M2 between enabled and disabled, a servo piston 4 connected to the swash plate 2 of the pump P and that changes the tilt angle of the pump P, a control pressure adjustment valve 5 that adjusts the control pressure Pc that controls the displacement of the servo piston 4, and a feedback lever 7 connected to the spool 5f of the control pressure adjustment valve 5 and the servo piston 4.

[0017] The flow rate control mechanism M1 performs flow rate control by controlling the tilt angle of the swash plate 2 of the pump P so that the pump displacement increases as the input pressure Pi increases. The horsepower control mechanism M2 performs horsepower control by controlling the pump displacement based on the discharge pressure Pout of the pump P. Note that horsepower control is a control that prevents engine stall by controlling the pump displacement so that the power required to drive the pump P does not exceed the output of the engine E. In the horsepower control state, the horsepower control mechanism M2 controls the tilt angle of the swash plate 2 of the pump P so that the pump displacement decreases as the discharge pressure Pout of the pump P increases.

[0018] The flow control mechanism M1 has a pressure chamber 8a to which the input pressure Pi from the electromagnetic proportional pressure reducing valve 20 is introduced, a flow control spool 8 whose one end face faces the pressure chamber 8a and which is displaced according to the input pressure Pi, and a spring 8b that biases the flow control spool 8 in a direction opposite to the biasing force of the input pressure Pi introduced into the pressure chamber 8a.

[0019] The position of the flow control spool 8 is set by the balance between the biasing force of the input pressure Pi introduced into the pressure chamber 8a in the +X direction shown in Fig. 1 and the biasing force of the spring 8b in the -X direction shown in Fig. 1. When the input pressure Pi is lower than a predetermined pressure, the flow control spool 8 is positioned in its initial position by the biasing force of the spring 8b, and as the input pressure Pi increases above the predetermined pressure, it moves in the +X direction.

[0020] The horsepower control mechanism M2 has a pressure chamber 9a to which the discharge pressure Pout of the pump P is introduced through a branch passage 3a branching off from the discharge passage 3, a horsepower control spool 9 whose one end face faces the pressure chamber 9a and which is displaced according to the discharge pressure Pout, and springs 9b and 9c which bias the horsepower control spool 9 in a direction opposite to the biasing force of the discharge pressure Pout introduced into the pressure chamber 9a.

[0021] The position of the power control spool 9 is set by the balance between the biasing force of the hydraulic oil at discharge pressure Pout in the -X direction and the biasing force of springs 9b and 9c in the +X direction. When discharge pressure Pout is lower than a predetermined pressure, the power control spool 9 is biased in the +X direction by the biasing forces of springs 9b and 9c, and is in its initial position separated from the feedback lever 7.

[0022] In this embodiment, the flow rate control spool 8 and the horsepower control spool 9 are arranged parallel to each other with the feedback lever 7 therebetween.

[0023] The lock mechanism 50 has a pressure chamber 50a to which the secondary pressure regulated by the electromagnetic proportional pressure reducing valve 20 is introduced, and a lock pin 50b whose one end face faces the pressure chamber 50a and which is displaced according to the pressure of the hydraulic oil introduced into the pressure chamber 50a. When the pressure acting on the lock pin 50b is equal to or greater than a predetermined value, the horsepower control by the horsepower control mechanism M2 is disabled, and when the pressure acting on the lock pin 50b is less than the predetermined value, the horsepower control by the horsepower control mechanism M2 is enabled. The secondary pressure regulated by the electromagnetic proportional pressure reducing valve 20 is introduced into the pressure chamber 50a through a passage 61.

[0024] A biasing force in the +X direction acts on the lock pin 50b due to the pressure of the hydraulic oil introduced into the pressure chamber 50a. This biasing force opposes a biasing force in the −X direction on the power control spool 9, which is generated by the pressure of the hydraulic oil introduced into the pressure chamber 9a. The biasing force in the +X direction, which is the sum of the biasing force acting on the lock pin 50b and the biasing force of the springs 9b and 9c, is set to be greater than the biasing force in the −X direction on the power control spool 9 that is generated when the maximum discharge pressure Poutmax acts on the power control spool 9. Therefore, when pressure (e.g., secondary pressure) equal to or greater than a predetermined value acts on the lock pin 50b, the power control spool 9 does not contact the feedback lever 7, and no biasing force in the −X direction from the power control spool 9 acts on the feedback lever 7. In other words, when pressure equal to or greater than a predetermined value acts on the lock pin 50b, power control by the power control spool 9 is not performed. In other words, for example, in a situation where secondary pressure is not output from the electromagnetic proportional pressure reducing valve 20 (in the event of a failure), secondary pressure does not act on the lock pin 50b, and therefore horsepower control is performed by the horsepower control spool 9. In this way, the flow rate control device 100 performs flow rate control in the normal state, and performs horsepower control in the event of a failure. Flow rate control and horsepower control will be described later.

[0025] The servo piston 4 is connected to the swash plate 2. The tilt angle of the swash plate 2 is changed by moving the servo piston 4 in the axial direction (X direction). The servo piston 4 has a large diameter portion 4a formed at one axial end and a small diameter portion 4b formed at the other axial end and having a smaller diameter than the large diameter portion 4a.

[0026] A housing (not shown) of the pump P is formed with a large-diameter side chamber 6a facing the large-diameter portion 4a of the servo piston 4, and a small-diameter side chamber 6b facing the small-diameter portion 4b of the servo piston 4. The pressure-receiving area of ​​the large-diameter portion 4a of the servo piston 4, on which the pressure of the large-diameter side chamber 6a acts, is larger than the pressure-receiving area of ​​the small-diameter portion 4b of the servo piston 4, on which the pressure of the small-diameter side chamber 6b acts. The large-diameter side chamber 6a is connected to a control pressure port 5c of the control pressure adjustment valve 5 through a control pressure passage 6c, and the small-diameter side chamber 6b is connected to a branch passage 3a branching from the discharge passage 3 of the pump P.

[0027] The control pressure adjustment valve 5 has a pump port 5a connected to the branch passage 3a, a tank port 5b connected to the tank T through a drain passage, a control pressure port 5c connected to the large-diameter side chamber 6a through a control pressure passage 6c, a spool 5f, a spring 5d that biases the spool 5f in a direction switching from a tank communication position A to a pump communication position C, which will be described later, and a connecting portion 5e that is connected to the feedback lever 7.

[0028] The control pressure regulating valve 5 has a tank communication position A, a shutoff position B, and a pump communication position C. In the tank communication position A, the control pressure port 5c and the tank port 5b are connected to each other, and the communication between the pump port 5a and the control pressure port 5c is shut off. In the shutoff position B, the communication between the pump port 5a and the control pressure port 5c is shut off, and the communication between the tank port 5b and the control pressure port 5c is shut off. In the pump communication position C, the pump port 5a and the control pressure port 5c are connected to each other, and the communication between the tank port 5b and the control pressure port 5c is shut off.

[0029] When the control pressure regulating valve 5 is switched to the tank communication position A, hydraulic oil is discharged from the large diameter side chamber 6a to the tank T through the control pressure regulating valve 5, and the pressure in the large diameter side chamber 6a decreases. When the control pressure regulating valve 5 is switched to the shut-off position B, the pressure in the large diameter side chamber 6a is maintained at a constant pressure. When the control pressure regulating valve 5 is switched to the pump communication position C, hydraulic oil is introduced into the large diameter side chamber 6a through the control pressure regulating valve 5, and the pressure in the large diameter side chamber 6a increases. In the initial state, the spool 5f of the control pressure regulating valve 5 is held at the pump communication position C by the biasing force of the spring 5d.

[0030] When the pressure in the large-diameter side chamber 6a becomes greater than a predetermined pressure, the servo piston 4 moves in the +X direction in FIG. 1. This reduces the tilt angle of the pump P, and the volume of the pump P decreases. When the pressure in the large-diameter side chamber 6a becomes less than a predetermined pressure, the servo piston 4 moves in the -X direction in FIG. 1. This increases the tilt angle of the pump P, and the volume of the pump P increases.

[0031] The feedback lever 7 feeds back the displacement of the servo piston 4 to the spool 5 f of the control pressure regulating valve 5 .

[0032] The high-pressure selection valve 40 outputs the higher of the secondary pressure output from the electromagnetic proportional pressure reducing valve 20 (secondary pressure port P4 of the valve device 10) and the output pressure output from the first switching valve 30 (output port P2 of the valve device 10) to a passage 62. The pressure output to the passage 62 is led to the pressure chamber 8a of the flow control mechanism M1.

[0033] Next, a specific configuration of the valve device 10 will be described with reference to Figures 1 and 2A-2C. Figure 2A is a cross-sectional view showing the main parts of the valve device 10 when the solenoid 12 is not energized. Figure 2B is a cross-sectional view showing the main parts of the valve device 10 when the solenoid 12 is energized. Figure 2C is a cross-sectional view showing the main parts of the valve device 10 when the electromagnetic proportional pressure reducing valve 20 has reached the set pressure.

[0034] As shown in FIGS. 2A, 2B, and 2C, the valve device 10 includes a housing 11, a solenoid 12, a spool 13 as a valve body, and a spring 14.

[0035] The housing 11 is provided with a bottomed accommodation hole 11a that slidably accommodates the spool 13. The opening of the accommodation hole 11a is closed by a solenoid 12. A spring 14 is provided on one end face of the spool 13 to bias the spool 13 in the +Y direction, which is the second direction. The other end face of the spool 13 is provided with a solenoid 12 that biases the spool 13 in the -Y direction, which is the first direction.

[0036] The housing 11 is further provided with an input port P1 to which primary pressure (hydraulic oil from a hydraulic power source) is introduced, an output port P2, a drain port P3 that communicates with a tank T, and a secondary pressure port P4 that outputs a secondary pressure adjusted by reducing the primary pressure (see also FIG. 1 ). The input port P1 is an upstream port in the valve device 10, and the output port P2 and the secondary pressure port P4 are downstream ports in the valve device 10.

[0037] The solenoid 12 is a solenoid driven by a direct current. The biasing force acting on the plunger 12a in the -Y direction of the solenoid 12 changes depending on the magnitude of the current applied to the solenoid 12. The plunger 12a of the solenoid 12 abuts against the other end face of the spool 13.

[0038] The spool 13 is biased in the +Y direction by the biasing force of the spring 14 and pressed against the plunger 12a of the solenoid 12. In other words, the plunger 12a of the solenoid 12 and the other end face of the spool 13 are always in contact with each other. Therefore, when the current applied to the solenoid 12 changes and the plunger 12a moves, the position of the spool 13 changes.

[0039] As shown in Figures 2A, 2B, and 2C, the spool 13 includes a first land portion 13a, a second land portion 13b, a third land portion 13c, a communication passage 13d extending in the axial direction of the spool 13 and communicating between the space 11b facing one end face of the spool 13 and the space 11c facing the other end face of the spool 13, a first annular groove 13e formed between the first land portion 13a and the second land portion 13b, and a second annular groove 13f formed between the second land portion 13b and the third land portion 13c.

[0040] The first land portion 13a, the second land portion 13b, and the third land portion 13c are provided at intervals in the axial direction in that order from the spring 14 side. The first land portion 13a is formed in a tapered shape that decreases in diameter toward one end face of the spool 13 (the spring 14 side). The outer diameter of a portion of the first land portion 13a facing the second land portion 13b across the first annular groove 13e is smaller than the outer diameter of the second land portion 13b, and the second land portion 13b and the third land portion 13c are formed to have the same outer diameter.

[0041] The first land portion 13a controls communication between the secondary pressure port P4 and the drain port P3. The second land portion 13b controls communication between the input port P1 and the secondary pressure port P4. The third land portion 13c controls communication between the input port P1 and the output port P2 and between the output port P2 and the drain port P3.

[0042] The space 11b is provided on the bottom side of the receiving hole 11a and is defined by the housing 11 and the spool 13 (first land portion 13a). The space 11b is constantly in communication with the drain port P3.

[0043] The space 11c is provided on the opening side of the accommodation hole 11a and is defined by the housing 11, the solenoid 12, and the spool 13 (third land portion 13c). The space 11c is constantly in communication with the drain port P3 through the communication passage 13d and the space 11b.

[0044] In this embodiment, the solenoid 12, the spring 14, the input port P1, the secondary pressure port P4, the drain port P3, the first land portion 13a of the spool 13, and the second land portion 13b of the spool 13 constitute an electromagnetic proportional pressure reducing valve 20. Furthermore, the solenoid 12, the spring 14, the input port P1, the output port P2, the drain port P3, and the third land portion 13c of the spool 13 constitute a first switching valve 30. That is, in the valve device 10 of this embodiment, the electromagnetic proportional pressure reducing valve 20 and the first switching valve 30 are integrally configured, and the valve bodies of the electromagnetic proportional pressure reducing valve 20 and the first switching valve 30 are integrally configured by the single spool 13. Furthermore, the electromagnetic proportional pressure reducing valve 20 and the first switching valve 30 are controlled by the single solenoid 12.

[0045] The operation of the valve device 10 configured in this manner will now be described.

[0046] When no current is applied to the solenoid 12, the spool 13 is in the position shown in Figure 2A. Specifically, the secondary pressure port P4 and the drain port P3 are in communication with each other, and the second land portion 13b blocks communication between the input port P1 and the secondary pressure port P4. Furthermore, the input port P1 and the output port P2 are in communication with each other, and the third land portion 13c blocks communication between the output port P2 and the drain port P3. In the position shown in Figure 2A, the input port P1 and the output port P2 are in communication with each other, so that hydraulic oil from the hydraulic power source is supplied to the pressure chamber 8a of the flow control mechanism M1 through the input port P1, the output port P2, the high-pressure selection valve 40, and the passage 62 (see also Figure 1).

[0047] When the operating lever 41 is operated and a command current is applied from the controller C to the solenoid 12, the biasing force of the solenoid 12 exceeds the biasing force of the spring 14, and the spool 13 moves from the position shown in FIG. 2A to the position shown in FIG. 2B (in the −Y direction). As a result, the input port P1 communicates with the secondary pressure port P4, and the third land portion 13c blocks the communication between the input port P1 and the output port P2. The first land portion 13a also blocks the communication between the secondary pressure port P4 and the drain port P3. Furthermore, the output port P2 communicates with the drain port P3 via the space 11c, the communication passage 13d, and the space 11b.

[0048] When the input port P1 and the secondary pressure port P4 are connected to each other, hydraulic oil is supplied from the hydraulic source to the secondary pressure port P4, increasing the pressure at the secondary pressure port P4. The hydraulic oil at the secondary pressure port P4 is supplied to the pressure chamber 50a of the lock mechanism 50 through the passage 61. This disables the horsepower control by the horsepower control mechanism M2.

[0049] Furthermore, the hydraulic oil at the secondary pressure port P4 passes through the high pressure selection valve 40 and the passage 62 and is led to the pressure chamber 8a of the flow control mechanism M1 (see FIG. 1). In the state shown in FIG. 2B, the pressure at the output port P2 is the drain pressure, so the pressure from the secondary pressure port P4 is output from the high pressure selection valve 40 to the passage 62.

[0050] As described above, the outer diameter of the portion of the first land portion 13a facing the second land portion 13b across the first annular groove 13e is smaller than the outer diameter of the second land portion 13b. Therefore, when secondary pressure acts on these portions, a biasing force acts on the spool 13 in the +Y direction (rightward) in FIG. 2B due to the difference in their pressure-receiving areas. This biasing force biases the spool 13 in opposition to the biasing force of the solenoid 12. In other words, the pressure acting on the difference in pressure-receiving areas between the first land portion 13a and the second land portion 13b corresponds to the feedback pressure in the electromagnetic proportional pressure reducing valve 20. Note that the configuration related to this difference in pressure-receiving areas between the first land portion 13a and the second land portion 13b corresponds to the "feedback section" in the claims.

[0051] As the secondary pressure increases, the biasing force of the secondary pressure (feedback pressure) biasing the spool 13 in the +Y direction increases, causing the spool 13 to move in the +Y direction (rightward) in FIG. 2B. This reduces the supply of hydraulic oil from the input port P1 to the secondary pressure port P4. When the spool 13 moves to a position (shown in FIG. 2C) where the combined biasing force of the feedback pressure acting on the spool 13 in the +Y direction and the biasing force of the spring 14 in the +Y direction balances with the biasing force of the solenoid 12 in the -Y direction, the second land portion 13b blocks communication between the input port P1 and the secondary pressure port P4. Note that in the state shown in FIG. 2C, the output port P2 and the drain port P3 remain in communication.

[0052] In the valve device 10, the first switching valve 30 is used to detect a failure of the solenoid 12. This will be explained in detail below.

[0053] 1, the first switching valve 30 has a normal position D (corresponding to the positions shown in FIGS. 2B and 2C) and a fail position E (corresponding to the position shown in FIG. 2A). In the normal position D, 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. In the fail position E, 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.

[0054] In this embodiment, even when the control lever 41 is not operated, a constant command current is applied to the solenoid 12 while the pump unit PU is operating (hereinafter, this command current value will be referred to as the "minimum command current"). When the minimum command current is applied to the solenoid 12 of the valve device 10, the first switching valve 30 is switched to the normal position D. Therefore, while the pump unit PU is operating, the first switching valve 30 is maintained in the normal position D regardless of whether the control lever 41 is operated. As a result, the output port P2 is maintained at drain pressure.

[0055] For example, if a failure occurs, such as a break in the coil of the solenoid 12 or a failure in outputting a command current from the controller C to the solenoid 12 (hereinafter, such a situation will also be referred to as a "solenoid 12 failure"), the biasing force of the solenoid 12 is lost, and the first switching valve 30 is switched from the normal position D to the fail position E by the biasing force of the spring 14. As a result, the input port P1 and the output port P2 are connected to each other, and primary pressure (hydraulic oil from the hydraulic power source) is output from the output port P2. Furthermore, if the solenoid 12 fails, the secondary pressure output from the electromagnetic proportional pressure reducing valve 20 decreases. This reduces the pressure in the pressure chamber 50a of the lock mechanism 50, enabling horsepower control by the horsepower control mechanism M2. Furthermore, if the secondary pressure output from the electromagnetic proportional pressure reducing valve 20 decreases, the high-pressure selecting valve 40 outputs the primary pressure (hydraulic oil from the hydraulic power source) output from the output port P2 to the passage 62. Therefore, if the solenoid 12 fails, the primary pressure (hydraulic oil from the hydraulic source) is supplied to the pressure chamber 8a of the flow control mechanism M1, causing the flow control mechanism M1 to request the pump P to deliver the maximum discharge flow rate.

[0056] Next, the operation of the pump unit PU will be described with reference to FIG.

[0057] When the operating lever 41 is operated, the controller C calculates a command current value corresponding to the amount of operation of the operating lever 41 based on the detection result of the operation sensor 41a, as described above, and applies the calculated command current to the solenoid 12 of the valve device 10. When the command current applied to the solenoid 12 increases, the secondary pressure (input pressure Pi) output from the electromagnetic proportional pressure reducing valve 20 increases, and the pressure supplied to the pressure chamber 8a of the flow rate control mechanism M1 through the secondary pressure port P4, the high pressure selection valve 40, and the passage 62 also increases. At this time, the secondary pressure (input pressure Pi) output from the electromagnetic proportional pressure reducing valve 20 is also guided to the pressure chamber 50a of the lock mechanism 50 through the passage 61. As a result, as described above, the horsepower control by the horsepower control mechanism M2 is disabled, and flow rate control by the flow rate control mechanism M1 is executed.

[0058] Next, the flow rate control by the flow rate control mechanism M1 will be described.

[0059] When the operating lever 41 is operated and the secondary pressure (input pressure Pi) output from the electromagnetic proportional pressure reducing valve 20, i.e., the pressure of the hydraulic oil in the pressure chamber 8a, increases, the biasing force in the +X direction acting on the flow rate control spool 8 increases. As a result, the flow rate control spool 8 moves in the +X direction against the biasing force of the spring 8b. The flow rate control spool 8 moves to a position where the biasing force in the +X direction due to the pressure of the hydraulic oil in the pressure chamber 8a and the biasing force in the -X direction by the spring 8b balance each other, and then stops.

[0060] Furthermore, since the spool 5f of the control pressure regulating valve 5 is connected to the feedback lever 7, the feedback lever 7 is pushed in the +X direction by the flow control spool 8, causing the valve to switch to the tank communication position A. In the tank communication position A, the tank port 5b and the control pressure port 5c are connected to each other, so that hydraulic oil is discharged from the large-diameter side chamber 6a to the tank T, and the biasing force that biases the servo piston 4 in the +X direction decreases. This causes the servo piston 4 to move in the -X direction, and the tilt angle of the swash plate 2 increases. In other words, the pump capacity increases.

[0061] Since the spool 5f of the control pressure regulating valve 5 is connected to the feedback lever 7, when the servo piston 4 moves in the -X direction, the spool 5f of the control pressure regulating valve 5 switches from the tank communication position A to the cut-off position B. This stops the discharge of hydraulic oil from the large-diameter side chamber 6a, and the servo piston 4 stops. As a result, the tilting of the swash plate 2 stops.

[0062] In this way, in the flow control by the flow control mechanism M1, the tilt angle of the swash plate 2 increases in accordance with an increase in the secondary pressure (input pressure Pi) output from the electromagnetic proportional pressure reducing valve 20, that is, an increase in the amount of operation of the operating lever 41.

[0063] In contrast, when the amount of operation of the operating lever 41 decreases (the operating lever 41 is returned) and the secondary pressure (input pressure Pi) output from the electromagnetic proportional pressure reducing valve 20, that is, the pressure of the hydraulic oil in the pressure chamber 8a, decreases, the biasing force in the +X direction acting on the flow rate control spool 8 decreases. As a result, the flow rate control spool 8 moves in the -X direction due to the biasing force of the spring 8b. The flow rate control spool 8 moves to a position where the biasing force pushing it in the +X direction by the pressure of the hydraulic oil in the pressure chamber 8a and the biasing force pushing it in the -X direction by the spring 8b balance each other, and then stops.

[0064] Furthermore, because the spool 5f of the control pressure regulating valve 5 is connected to the feedback lever 7, the feedback lever 7 is pulled in the -X direction by the flow control spool 8, switching it from the shut-off position B to the pump communication position C. In the pump communication position C, the pump port 5a and the control pressure port 5c are connected to each other, so that the discharge pressure Pout is supplied to the large-diameter side chamber 6a, and the biasing force that biases the servo piston 4 in the +X direction increases. This causes the servo piston 4 to move in the +X direction, and the tilt angle of the swash plate 2 decreases. In other words, the pump displacement decreases.

[0065] Since the spool 5f of the control pressure regulating valve 5 is connected to the feedback lever 7, when the servo piston 4 moves in the +X direction, the spool 5f of the control pressure regulating valve 5 switches from the pump communication position C to the cut-off position B. This stops the supply of hydraulic oil to the large-diameter side chamber 6a, and the servo piston 4 stops. As a result, the tilting of the swash plate 2 also stops.

[0066] In this way, in the flow control by the flow control mechanism M1, the tilt angle of the swash plate 2 decreases in accordance with the decrease in the secondary pressure (input pressure Pi) output from the electromagnetic proportional pressure reducing valve 20, that is, the decrease in the amount of operation of the operating lever 41.

[0067] When the operation of the operating lever 41 ends (the operation amount of the operating lever 41 becomes 0 (zero)), the secondary pressure (input pressure Pi) output from the electromagnetic proportional pressure reducing valve 20 decreases, and the flow control spool 8 moves in the −X direction due to the bias of the spring 8b and returns to its initial position.

[0068] In this way, in the flow control by the flow control mechanism M1, the flow rate discharged from the pump P is controlled by controlling the tilt angle of the swash plate 2 in accordance with the amount of operation of the operating lever 41.

[0069] In this embodiment, even when the operating lever 41 is not operated, the minimum command current is applied to the solenoid 12 as described above. This causes the electromagnetic proportional pressure reducing valve 20 to supply a predetermined secondary pressure (input pressure Pi) to the pressure chamber 50a of the lock mechanism 50, preventing horsepower control by the horsepower control mechanism M2.

[0070] In this way, in the flow control by the flow control mechanism M1, the pump capacity of the pump P can be controlled by driving the flow control spool 8 and controlling the tilt angle of the swash plate 2 based on the secondary pressure (input pressure Pi) corresponding to the amount of operation of the operating lever 41.

[0071] Next, the horsepower control by the horsepower control mechanism M2 will be described.

[0072] The horsepower control is performed when the solenoid 12 of the valve device 10 (electromagnetic proportional pressure reducing valve 20) fails as described above. The horsepower control is performed based on the discharge pressure Pout and the control pressure Pc of the pump P, regardless of the amount of operation of the operating lever 41.

[0073] As described above, if the solenoid 12 fails, the first switching valve 30 switches to the fail position E, and the primary pressure is supplied to the pressure chamber 8a of the flow control mechanism M1. As a result, the flow control mechanism M1 enters a state in which it requests the pump P to deliver the maximum discharge flow rate.

[0074] When the discharge pressure Pout of the pump P increases, the discharge pressure Pout of the pump P is supplied to the small diameter side chamber 6b and the pressure chamber 9a of the horsepower control mechanism M2 through the discharge passage 3 and the branch passage 3a, and the pressure in the small diameter side chamber 6b and the pressure chamber 9a increases.

[0075] Even if the pressure in the small diameter side chamber 6b rises, when the spool 5f of the control pressure regulating valve 5 is in the shutoff position B, the large diameter side chamber 6a is shut off, so the servo piston 4 does not move.

[0076] When the pressure in pressure chamber 9a increases, a biasing force in the −X direction acts on the power control spool 9. When the solenoid 12 fails, as described above, no pressure is supplied to the pressure chamber 50a of the locking mechanism 50, so the power control spool 9 moves in the −X direction against the biasing forces of the springs 9b and 9c and comes into contact with the feedback lever 7, pushing the feedback lever 7 in the −X direction.

[0077] The spool 5f of the control pressure control valve 5 is connected to the feedback lever 7, and when the horsepower control spool 9 pushes the feedback lever 7 in the -X direction, the control lever 7 switches from the shutoff position B to the pump communication position C. In the pump communication position C, the pump port 5a and the control pressure port 5c communicate with each other, and the control pressure Pc supplied to the large-diameter side chamber 6a increases. This increases the biasing force that biases the servo piston 4 in the +X direction, and the servo piston 4 moves in the +X direction. As a result, the tilt angle of the swash plate 2 decreases, and the pump capacity decreases.

[0078] When the servo piston 4 moves in the +X direction, the servo piston 4 pushes the spool 5 f of the control pressure adjustment valve 5 in the +X direction via the feedback lever 7. As a result, the spool 5 f of the control pressure adjustment valve 5 switches from the pump communication position C to the cut-off position B.

[0079] In this way, in the horsepower control by the horsepower control mechanism M2, when the discharge pressure Pout of the pump P increases, the tilt angle of the swash plate 2 is controlled to decrease accordingly.

[0080] On the other hand, when the discharge pressure Pout of the pump P decreases, the pressure in the pressure chamber 9a and the small diameter side chamber 6b decreases.

[0081] Even if the pressure in the small diameter side chamber 6b drops, when the spool 5f of the control pressure regulating valve 5 is in the shutoff position B, the large diameter side chamber 6a is shut off, so the servo piston 4 does not move.

[0082] When the pressure in the pressure chamber 9a decreases, the horsepower control spool 9 is pushed in the -X direction by the biasing force of springs 9b and 9c. Because the spool 5f of the control pressure regulating valve 5 is connected to the feedback lever 7, the horsepower control spool 9 pushes the feedback lever 7 in the +X direction, switching it from the shut-off position B to the tank communication position A. In the tank communication position A, the tank port 5b and the control pressure port 5c are connected to each other, so the pressure in the large-diameter side chamber 6a (control pressure Pc) decreases. This reduces the biasing force that biases the servo piston 4 in the +X direction, causing the servo piston 4 to move in the -X direction. As a result, the tilt angle of the swash plate 2 increases, and the pump capacity increases.

[0083] When the servo piston 4 moves in the −X direction, the servo piston 4 pulls the spool 5 f of the control pressure adjustment valve 5 in the −X direction via the feedback lever 7. As a result, the spool 5 f of the control pressure adjustment valve 5 switches from the tank communication position A to the cut-off position B.

[0084] In this way, in the horsepower control by the horsepower control mechanism M2, when the discharge pressure Pout of the pump P increases, the tilt angle of the swash plate 2 is controlled to decrease accordingly.

[0085] In this way, while the horsepower control is being performed in the pump unit PU, the tilt angle of the swash plate 2 is constantly controlled as described above based on changes in the discharge pressure Pout of the pump P. Therefore, even if the solenoid 12 fails, the flow rate of the pump P can be reliably controlled, and stalling of the engine E can be prevented.

[0086] The valve device 10 and the flow rate control device 100 in the first embodiment configured as described above have the following advantages.

[0087] In the flow control device 100, under normal conditions, that is, when the solenoid 12 is not malfunctioning, the flow rate is controlled by the flow rate control mechanism M1, and when the solenoid 12 is malfunctioning, the horsepower control mechanism M2 controls the horsepower. This allows the flow rate of the pump P to be reliably controlled even when the solenoid 12 is malfunctioning.

[0088] Furthermore, in the valve device 10 of this embodiment, the electromagnetic proportional pressure reducing valve 20 and the first switching valve 30 are formed integrally, and further, the valve element of the electromagnetic proportional pressure reducing valve 20 and the valve element of the first switching valve 30 are formed integrally by a single spool 13. This allows the valve device 10 to be made smaller, and the number of parts is reduced, resulting in cost reduction.

[0089] Furthermore, in the valve device 10 of this embodiment, the input port P1 and the drain port P3 are common to the electromagnetic proportional pressure reducing valve 20 and the first switching valve 30. This makes it possible to reduce the number of ports.

[0090] Furthermore, in the valve device 10, when the solenoid 12 fails, the output port P2 communicates with the input port P1 via the drain port P3. Therefore, if the solenoid 12 fails, when the solenoid 12 is turned from OFF to ON, the output port P2 remains in communication with the input port P1. Therefore, by detecting the pressure on the output port P2 side, it is possible to determine whether there is an abnormality in the solenoid 12 when the device is started.

[0091] Furthermore, for example, if the valve device 10 is applied to a hydraulic excavator or the like, if a malfunction occurs in an actuator such as a boom while the actuator is being operated, the solenoid 12 can be switched ON and OFF to determine whether or not there is an abnormality in the solenoid 12 based on whether or not there is a change in the pressure on the output port P2 side. In other words, if the pressure on the output port P2 side changes, it can be determined that there is no abnormality in the valve device 10, and if the pressure on the output port P2 side does not change, it can be determined that the valve device 10 may be stuck in the open state. In this way, the valve device 10 in which the electromagnetic proportional pressure reducing valve 20 is integrally provided with the first switching valve 30 can also determine whether or not there is an abnormality in the valve device 10 based on a change in the pressure on the output port P2 side.

[0092] Next, a flow control device 200, which is a modified example of the flow control device 100, will be described with reference to FIG.

[0093] In the above-described flow control device 100, the second switching valve is configured as a high-pressure selection valve 40, whereas in the flow control device 200 of this modified example, the second switching valve is configured as a 5-port switching valve 240, which is different from the flow control device 100 of the first embodiment. Only the differences from the flow control device 100 will be described below, and the same components will be assigned the same numbers and will not be described again.

[0094] 3, the switching valve 240 is a pilot-operated 5-port 2-position switching valve. The switching valve 240 has a normal position F in which the passage 62 communicates with the secondary pressure port P4 and the passage 61 communicates with the hydraulic power source through a passage 263, and a fail position G in which the passage 62 communicates with the hydraulic power source through the passage 263 and the passage 61 communicates with the tank T.

[0095] The switching valve 240 is switched in response to the pressure output from the output port P2. When no pressure is output from the output port P2 (the state shown in FIG. 3), the switching valve 240 is held in the normal position F by the biasing force of the spring 240a. When pressure is output from the output port P2, the switching valve 240 is switched from the normal position F to the fail position G.

[0096] The operation of the flow rate control device 200 configured in this manner will be described.

[0097] When the solenoid 12 is normal, as described above, the first switching valve 30 is switched to the normal position D. In the normal position D, the output port P2 is connected to the tank T, so the pilot pressure of the switching valve 240 is the tank pressure, and the switching valve 240 is located in the normal position F by the biasing force of the spring 240a.

[0098] As described above, in the normal position F, the passage 61 communicates with the hydraulic pressure source through the passage 263, and therefore the primary pressure is supplied to the pressure chamber 50a of the locking mechanism 50 through the passage 263, the switching valve 240, and the passage 61. This disables the horsepower control by the horsepower control mechanism M2.

[0099] Also, as described above, in the normal position F, the passage 62 and the secondary pressure port P4 are connected, so that the secondary pressure (input pressure Pi) is supplied to the pressure chamber 8a of the flow control mechanism M1 through the secondary pressure port P4, the switching valve 240 and the passage 62.

[0100] In this way, in the flow control device 200, when the solenoid 12 is operating normally, the switching valve 240 is held in the normal position F, and flow control based on the input pressure Pi is executed.

[0101] On the other hand, if the solenoid 12 fails, as described above, the biasing force of the solenoid 12 is lost, and the first switching valve 30 is switched from the normal position D to the fail position E by the biasing force of the spring 14. As a result, the input port P1 and the output port P2 are communicated, and the primary pressure is supplied as pilot pressure to the switching valve 240 through the first switching valve 30. As a result, the switching valve 240 is switched from the normal position F to the fail position G.

[0102] As described above, in the fail position G, the passage 62 and the passage 263 communicate with each other, and therefore the primary pressure is supplied to the pressure chamber 8 a of the flow rate control mechanism M 1 through the passage 263 and the passage 62 .

[0103] Furthermore, as described above, in the fail position G, the passage 61 communicates with the tank T, so that the hydraulic oil in the pressure chamber 50a of the locking mechanism 50 is discharged to the tank T through the passage 61 and the switching valve 240. This enables the horsepower control by the horsepower control mechanism M2.

[0104] The operations of the valve device 10 and the flow control unit M in the flow control device 200 are the same as those in the flow control device 100, and therefore will not be described here.

[0105] The flow control device 200 according to this modified example can also achieve the same effects as the flow control device 100 .

[0106] In the flow control device 200, the case where the spring 240a is used to switch the switching valve 240 to the normal position F has been described, but this is not limiting, and for example, instead of the spring 240a, the switching valve 240 may be switched to the normal position F by the secondary pressure output from the secondary pressure port P4. Even in this case, when the solenoid 12 fails, the secondary pressure drops and the primary pressure acts on the switching valve 240 as a pilot pressure, so that the switching valve 240 switches to the fail position G.

[0107] Next, a flow control device 300, which is a modified example of the flow control device 200, will be described with reference to FIG.

[0108] In the flow control device 200, the second switching valve is configured as a five-port switching valve 240, whereas in the flow control device 300 of this modified example, the second switching valve is configured as a three-port switching valve 341 and a high-pressure selection valve 342, which is a difference from the flow control device 200 of the modified example. Only the differences from the flow control devices 100 and 200 will be explained below, and the same components will be assigned the same numbers and will not be explained again.

[0109] 4, the switching valve 341 is a pilot-operated three-port two-position switching valve. The switching valve 341 has a normal position H in which the passage 61 communicates with the hydraulic power source through the passage 263, and a fail position I in which the passage 61 communicates with the tank T.

[0110] The switching valve 341 is switched in response to the pressure output from the output port P2. When no pressure is output from the output port P2 (the state shown in FIG. 4), the switching valve 341 is held in the normal position H by the biasing force of the spring 341a. When pressure is output from the output port P2, the switching valve 341 is switched from the normal position H to the fail position I.

[0111] The high-pressure selection valve 342 outputs to the passage 62 the pressure output from the secondary pressure port P4 or the pressure output from the output port P2, whichever is higher.

[0112] The operation of the flow rate control device 300 configured in this manner will be described.

[0113] When the solenoid 12 is normal, as described above, the first switching valve 30 is switched to the normal position D. In the normal position D, the output port P2 is connected to the tank T, so the pilot pressure of the switching valve 341 is the tank pressure, and the switching valve 341 is located in the normal position H due to the biasing force of the spring 341a.

[0114] As described above, in the normal position H, the passage 61 communicates with the hydraulic power source through the passage 263, and therefore the primary pressure is supplied to the pressure chamber 50a of the locking mechanism 50 through the passage 263, the switching valve 341, and the passage 263. This disables the horsepower control by the horsepower control mechanism M2.

[0115] Furthermore, when the solenoid 12 is operating normally, the secondary pressure (input pressure Pi) is output from the secondary pressure port P4. Therefore, the secondary pressure (input pressure Pi) is output from the high-pressure selection valve 342. As a result, the secondary pressure (input pressure Pi) is supplied to the pressure chamber 8a of the flow control mechanism M1 through the secondary pressure port P4, the passage 364, the high-pressure selection valve 342, and the passage 62.

[0116] In this way, in the flow control device 300, when the solenoid 12 is operating normally, the switching valve 341 is held in the normal position H, and the flow control mechanism M1 executes flow control based on the input pressure Pi.

[0117] On the other hand, if the solenoid 12 fails, as described above, the biasing force of the solenoid 12 is lost, and the first switching valve 30 is switched from the normal position D to the fail position E by the biasing force of the spring 14. As a result, the input port P1 and the output port P2 are communicated, and the primary pressure is supplied as pilot pressure to the switching valve 341 through the first switching valve 30. As a result, the switching valve 341 is switched from the normal position H to the fail position I.

[0118] When the solenoid 12 fails and the first switching valve 30 switches from the normal position D to the fail position E, the input port P1 and the output port P2 communicate with each other, and the primary pressure is supplied from the output port P2 to the passage 364. Furthermore, when the solenoid 12 fails, the pressure output from the secondary pressure port P4 of the electromagnetic proportional pressure reducing valve 20 drops. Therefore, the primary pressure supplied from the output port P2 to the passage 364 is output from the high-pressure selection valve 342. As a result, the primary pressure is supplied to the pressure chamber 8a of the flow control mechanism M1 through the passages 263 and 62.

[0119] Furthermore, as described above, in the fail position I, the passage 61 communicates with the tank T, and therefore the hydraulic oil in the pressure chamber 50a of the locking mechanism 50 is discharged to the tank T through the passage 61 and the switching valve 240. This enables the horsepower control by the horsepower control mechanism M2.

[0120] The operations of the valve device 10 and the flow control unit M in the flow control device 300 are the same as those in the flow control devices 100 and 200, and therefore will not be described here.

[0121] The flow control device 300 according to this modified example can also achieve the same effects as the flow control devices 100 and 200.

[0122] Next, a flow control device 400, which is a modified example of the flow control device 300, will be described with reference to FIG.

[0123] In the flow control device 300, the second switching valve is composed of a three-port switching valve 341 and a high-pressure selection valve 342, whereas in the flow control device 400 of this modified example, the second switching valve is composed of only a three-port switching valve 440, which is different from the flow control device 300 of the modified example. In addition, the flow control device 400 of this modified example differs from the flow control device 300 of the modified example in that a lock pin 450b in a lock mechanism 450 is configured integrally with the horsepower control spool 9. Only the differences from the flow control devices 100, 200, and 300 will be described below, and the same components will be assigned the same numbers and will not be described again.

[0124] 5, the switching valve 440 is a pilot-operated three-port two-position switching valve. The switching valve 440 has a normal position J in which the passage 461 communicates with the secondary pressure port P4, and a fail position K in which the passage 461 communicates with the hydraulic power source via the passage 263.

[0125] The switching valve 440 is switched in response to the pressure output from the output port P2. When no pressure is output from the output port P2 (the state shown in FIG. 5), the switching valve 440 is held in the normal position J by the biasing force of the spring 440a. When pressure is output from the output port P2, the switching valve 440 is switched from the normal position J to the fail position K.

[0126] As shown in Figure 5, in the flow control device 400, the locking mechanism 450 has a pressure chamber 450a that communicates with the output port P2 through a passage 462, and a locking pin 450b that has one end face facing the pressure chamber 450a and is displaced in response to the pressure of the hydraulic oil introduced into the pressure chamber 450a.

[0127] In this modification, the lock pin 450 b has a smaller diameter than the power control spool 9 and is formed integrally with the power control spool 9 .

[0128] In the flow control device 400 of this modified example, when the pressure acting on the lock pin 450b is equal to or less than a predetermined value, the horsepower control by the horsepower control mechanism M2 is disabled, and when the pressure acting on the lock pin 450b is greater than the predetermined value, the horsepower control by the horsepower control mechanism M2 is enabled.

[0129] Specifically, the biasing force of the springs 9b, 9c is set to be greater than the biasing force generated when the maximum discharge pressure Poutmax acts on the power control spool 9, but smaller than the biasing force generated when the primary pressure acts on the lock pin 450b. As a result, when no pressure is supplied to the pressure chamber 450a, in other words, when no biasing force is acting on the lock pin 450b, the power control spool 9 does not displace. In other words, power control is disabled.

[0130] In contrast, when primary pressure (pressure of the hydraulic power source) is supplied to pressure chamber 450a, the sum of the biasing force acting on the horsepower control spool 9 and the biasing force acting on lock pin 450b becomes greater than the biasing force of springs 9b and 9c, and the horsepower control spool 9 can be displaced in accordance with the pressure supplied to pressure chamber 9a. In other words, horsepower control becomes effective.

[0131] The operation of the flow rate control device 400 configured in this manner will be described.

[0132] When the solenoid 12 is normal, as described above, the first switching valve 30 is switched to the normal position D. In the normal position D, the output port P2 is connected to the tank T, so the pilot pressure of the switching valve 440 is the tank pressure, and the switching valve 440 is located in the normal position J by the biasing force of the spring 440a.

[0133] Furthermore, when the first switching valve 30 is in the normal position D, the pressure chamber 450a of the locking mechanism 450 is in communication with the tank T through the passage 462 and the first switching valve 30. Therefore, the horsepower control by the horsepower control mechanism M2 is disabled.

[0134] When the switching valve 440 is in the normal position J, the passage 461 is connected to the secondary pressure port P4, so that the secondary pressure (input pressure Pi) is supplied to the pressure chamber 8a of the flow control mechanism M1 through the secondary pressure port P4, the switching valve 440 and the passage 461.

[0135] In this way, in the flow control device 400, when the solenoid 12 is operating normally, the switching valve 440 is held in the normal position J, and the flow control mechanism M1 executes flow control based on the input pressure Pi.

[0136] On the other hand, if the solenoid 12 fails, as described above, the biasing force of the solenoid 12 is lost, and the first switching valve 30 is switched from the normal position D to the fail position E by the biasing force of the spring 14. As a result, the input port P1 and the output port P2 are communicated, and the primary pressure is supplied as pilot pressure to the switching valve 440 through the first switching valve 30. As a result, the switching valve 440 is switched from the normal position J to the fail position K.

[0137] As described above, in the fail position K, the passage 461 communicates with the hydraulic pressure source through the passage 263, so that the primary pressure is supplied to the pressure chamber 8a of the flow control mechanism M1 through the passages 263 and 461.

[0138] Furthermore, as described above, when the first switching valve 30 switches from the normal position D to the fail position E, the primary pressure is supplied to the pressure chamber 450a of the lock mechanism 450 through the output port P2 of the first switching valve 30 and the passage 462. This enables the horsepower control by the horsepower control mechanism M2.

[0139] The operations of the valve device 10 and the flow control unit M in the flow control device 400 are the same as those in the flow control devices 100, 200, and 300, and therefore will not be described here.

[0140] The flow control device 400 according to this modification also achieves the same effects as the flow control devices 100, 200, and 300. Furthermore, compared to the flow control device 300, the flow control device 400 does not use the high-pressure selection valve 342, and therefore the number of parts can be reduced.

[0141] Second Embodiment A valve device 510 and a flow control device 500 including the valve device 510 according to a second embodiment will be described with reference to FIGS. 6 and 7A to 7C.

[0142] In the flow control device 100 according to the first embodiment, when the input pressure Pi input to the flow control mechanism M1 increases during flow control, the tilt angle of the swash plate 2 (pump capacity) increases. However, in the flow control device 500 according to the second embodiment, when the input pressure Pi input to the flow control mechanism M11 increases during flow control, the tilt angle of the swash plate 2 (pump capacity) decreases, which is different from the flow control device 100 according to the first embodiment.

[0143] Furthermore, in the valve device 10 according to the first embodiment, when the solenoid 12 fails, the input port P1 and the output port P2 are connected, whereas in the valve device 510 according to the second embodiment, when the solenoid 12 fails, the output port P2 and the drain port P3 are connected, which is different from the valve device 10 according to the first embodiment.

[0144] In the following, only the differences from the first embodiment and its modified examples will be described, and the same components will be assigned the same numbers and descriptions thereof will be omitted.

[0145] As shown in FIG. 6 , the flow control mechanism M11 in the flow control device 500 has a pressure chamber 508a to which the input pressure Pi from the electromagnetic proportional pressure reducing valve 20 is introduced, a flow control spool 508 having one end face facing the pressure chamber 508a and displacing in accordance with the input pressure Pi, and a spring 508b that biases the flow control spool 508 in a direction opposite to the biasing force of the input pressure Pi introduced to the pressure chamber 508a.

[0146] The position of the flow control spool 508 is set by the balance between the biasing force of the input pressure Pi introduced into the pressure chamber 508a in the −X direction shown in Fig. 6 and the biasing force of the spring 508b in the +X direction shown in Fig. 6. When the input pressure Pi is lower than a predetermined pressure, the flow control spool 508 is positioned in its initial position by the biasing force of the spring 508b, and as the input pressure Pi increases above the predetermined pressure, it moves in the −X direction.

[0147] In the flow control mechanism M11 configured as described above, as the input pressure Pi increases above a predetermined pressure, the flow control spool 508 moves in the −X direction, and the feedback lever 7 is pushed in the −X direction by the flow control spool 508. As described above, the spool 5f of the control pressure control valve 5 is connected to the feedback lever 7. When the flow control spool 8 pushes the feedback lever 7 in the −X direction, the spool 5f of the control pressure control valve 5 switches from the shutoff position B to the pump communication position C. At the pump communication position C, the pump port 5a and the control pressure port 5c communicate with each other, so that the discharge pressure Pout is supplied to the large-diameter side chamber 6a, and the biasing force that biases the servo piston 4 in the +X direction increases. This causes the servo piston 4 to move in the +X direction, reducing the tilt angle of the swash plate 2. In other words, the pump displacement decreases.

[0148] In contrast, in the flow control mechanism M11, as the input pressure Pi decreases, the flow control spool 508 moves in the +X direction, pushing the feedback lever 7 in the +X direction. As described above, the spool 5f of the control pressure control valve 5 is connected to the feedback lever 7. When the flow control spool 8 pushes the feedback lever 7 in the +X direction, the spool 5f of the control pressure control valve 5 switches from the shutoff position B to the tank communication position A. At the tank communication position A, the tank port 5b and the control pressure port 5c are connected to each other, so the hydraulic oil in the large-diameter side chamber 6a is discharged and the biasing force that biases the servo piston 4 in the +X direction is reduced. This causes the servo piston 4 to move in the -X direction, increasing the tilt angle of the swash plate 2. In other words, the pump displacement increases.

[0149] In this way, in the flow control device 500, the pump capacity of the pump P decreases as the secondary pressure (input pressure Pin) from the electromagnetic proportional pressure reducing valve 20 increases, and the pump capacity of the pump P increases as the secondary pressure (input pressure Pin) from the electromagnetic proportional pressure reducing valve 20 decreases.

[0150] Next, the valve device 510 will be described.

[0151] As shown in FIG. 6 , the valve device 510 includes a solenoid 12, an electromagnetic proportional pressure reducing valve 20 that reduces the primary pressure and adjusts it to a secondary pressure that corresponds to a command current applied to the solenoid 12, and a first switching valve 530 that can be switched to a normal position L or a fail position M in accordance with the biasing force generated by the solenoid 12.

[0152] The specific configuration of the valve device 510 will be described with reference to Figures 6 and 7A-7C. Figure 7A is a cross-sectional view showing the main parts of the valve device 510 when the solenoid 12 is not energized. Figure 7B is a cross-sectional view showing the main parts of the valve device 510 when the solenoid 12 is energized. Figure 7C is a cross-sectional view showing the main parts of the valve device 10 when the electromagnetic proportional pressure reducing valve 20 has reached the set pressure.

[0153] As shown in FIGS. 7A, 7B, and 7C, the valve device 510 includes a housing 511, a solenoid 12, a spool 513 as a valve body, and a spring 14.

[0154] The housing 511 is provided with a bottomed accommodation hole 511a that slidably accommodates the spool 513. A spring 14 that urges the spool 513 in the +Y direction is provided on one end face side of the spool 513. A solenoid 12 that urges the spool 513 in the -Y direction is provided on the other end face side of the spool 513.

[0155] The housing 511 is further provided with an input port P1 to which primary pressure (hydraulic oil from the hydraulic power source) is introduced, an output port P2, a drain port P3 communicating with the tank T, and a secondary pressure port P4 from which adjusted secondary pressure is output by reducing the primary pressure (see also FIG. 6).

[0156] The spool 513 is biased in the +Y direction by the biasing force of the spring 14 and pressed against the plunger 12a of the solenoid 12. In other words, the plunger 12a of the solenoid 12 and the other end face of the spool 513 are always in contact with each other. Therefore, when the current applied to the solenoid 12 changes and the plunger 12a moves, the position of the spool 513 changes.

[0157] As shown in Figures 7A, 7B, and 7C, the spool 513 includes a first land portion 513a, a second land portion 513b, a third land portion 513c, a fourth land portion 513h, a communication passage 513d extending in the axial direction of the spool 513 and communicating between a space 511b facing one end face of the spool 513 and a space 511c facing the other end face of the spool 513, a first annular groove 513e formed between the first land portion 513a and the second land portion 513b, a second annular groove 513f formed between the second land portion 513b and the third land portion 513c, and a third annular groove 513g formed between the third land portion 513c and the fourth land portion 513h.

[0158] The first land portion 513a, the second land portion 513b, the third land portion 513c, and the fourth land portion 513h are provided at intervals in the axial direction in that order from the spring 14 side. The first land portion 513a is formed in a tapered shape that decreases in diameter toward one end face side (the spring 14 side) of the spool 513. The outer diameter of a portion of the first land portion 513a that faces the second land portion 513b across the first annular groove 513e is smaller than the outer diameter of the second land portion 513b, and the second land portion 513b, the third land portion 513c, and the fourth land portion 513h are formed to have the same outer diameter.

[0159] The first land portion 513a controls communication between the secondary pressure port P4 and the drain port P3. The second land portion 513b controls communication between the input port P1 and the secondary pressure port P4. The third land portion 513c controls communication between the input port P1 and the output port P2. The fourth land portion 513h controls communication between the output port P2 and the drain port P3.

[0160] The space 511b is formed in the receiving hole 511a as a space for receiving the spring 14. The space 511b is always in communication with the drain port P3.

[0161] The space 511c is provided on the solenoid 12 side of the accommodation hole 511a and is defined by the housing 511, the solenoid 12, and the spool 513 (fourth land portion 513h). The space 511c is constantly in communication with the drain port P3 through a communication passage 513d.

[0162] In this embodiment, the solenoid 12, the spring 14, the input port P1, the secondary pressure port P4, the drain port P3, the first land portion 513a of the spool 513, and the second land portion 513b of the spool 513 constitute the electromagnetic proportional pressure reducing valve 20. Furthermore, the solenoid 12, the spring 14, the input port P1, the output port P2, the drain port P3, and the third land portion 513c and the fourth land portion 513h of the spool 513 constitute the first switching valve 530. That is, in the valve device 510 of this embodiment, the electromagnetic proportional pressure reducing valve 20 and the first switching valve 530 are integrally formed, and the valve bodies of the electromagnetic proportional pressure reducing valve 20 and the first switching valve 530 are integrally formed by the single spool 513. Furthermore, the electromagnetic proportional pressure reducing valve 20 and the first switching valve 530 are controlled by the single solenoid 12.

[0163] The operation of the valve device 510 configured in this manner will now be described.

[0164] When no current is applied to the solenoid 12, the spool 513 is in the position shown in Figure 7A. Specifically, the secondary pressure port P4 and the drain port P3 are in communication with each other, and the second land portion 513b blocks communication between the input port P1 and the secondary pressure port P4. Furthermore, the third land portion 513c blocks communication between the input port P1 and the output port P2, and the output port P2 and the drain port P3 are in communication with each other. In the position shown in Figure 7A, the output port P2 and the drain port P3 are in communication with each other, so the pressure in the pressure chamber 50a of the locking mechanism 50 is tank pressure (see also Figure 6).

[0165] When the operating lever 41 is operated and a command current is applied from the controller C to the solenoid 12, the biasing force of the solenoid 12 exceeds the biasing force of the spring 14, and the spool 513 moves from the position shown in FIG. 7A to the position shown in FIG. 7B (in the −Y direction). This connects the input port P1 to the secondary pressure port P4, and also connects the input port P1 to the output port P2. Furthermore, the first land portion 513a blocks communication between the secondary pressure port P4 and the drain port P3.

[0166] When the input port P1 and the output port P2 are connected to each other, hydraulic oil is supplied from the hydraulic power source to the output port P2. The hydraulic oil in the output port P2 is supplied to the pressure chamber 50a of the lock mechanism 50 through a passage 561 (see also FIG. 6). This disables the horsepower control by the horsepower control mechanism M2.

[0167] Furthermore, when the input port P1 and the secondary pressure port P4 are connected to each other, hydraulic oil is supplied from the hydraulic power source to the secondary pressure port P4, increasing the pressure at the secondary pressure port P4. As shown in Figure 6, the hydraulic oil at the secondary pressure port P4 is guided through a passage 562 to the pressure chamber 508a of the flow control mechanism M1.

[0168] As described above, the outer diameter of the portion of the first land portion 513a facing the second land portion 513b across the first annular groove 513e is smaller than the outer diameter of the second land portion 513b. Therefore, when secondary pressure acts on these portions, a biasing force acts on the spool 513 in the +Y direction (rightward) in FIG. 7B due to the difference in their pressure-receiving areas. This biasing force biases the spool 513 in opposition to the biasing force of the solenoid 12. In other words, in the valve device 510, the pressure acting on the difference in pressure-receiving areas between the first land portion 513a and the second land portion 513b corresponds to the feedback pressure in the electromagnetic proportional pressure reducing valve 20. Note that the configuration related to this difference in pressure-receiving areas between the first land portion 513a and the second land portion 513b corresponds to the "feedback section" in the claims.

[0169] As the secondary pressure increases, the biasing force of the secondary pressure (feedback pressure) biasing the spool 513 in the +Y direction increases, causing the spool 513 to move in the +Y direction (rightward) in FIG. 7B . This reduces the supply of hydraulic oil from the input port P1 to the secondary pressure port P4. When the spool 513 moves to a position (shown in FIG. 7C ) where the combined biasing force of the feedback pressure acting on the spool 513 in the +Y direction and the biasing force of the spring 14 in the +Y direction balances with the biasing force of the solenoid 12 in the -Y direction, the second land portion 513b blocks communication between the input port P1 and the secondary pressure port P4. Note that in the state shown in FIG. 7C , the input port P1 and the output port P2 remain in communication.

[0170] 6, the first switching valve 530 has a normal position L (corresponding to the position shown in FIGS. 7B and 7C) and a fail position M (corresponding to the position shown in FIG. 7A). In the normal position L, the input port P1 and the output port P2 are connected, and the output port P2 and the drain port P3 are disconnected. In the fail position M, the output port P2 and the drain port P3 are connected, and the input port P1 and the output port P2 are disconnected.

[0171] In this embodiment, even if the control lever 41 is not operated, when the pump unit PU is operating, a minimum command current is applied to the solenoid 12. When the minimum command current is applied to the solenoid 12 of the valve device 510, the first switching valve 530 is switched to the normal position L. Therefore, when the pump unit PU is operating, the first switching valve 530 is maintained in the normal position L regardless of whether the control lever 41 is operated. As a result, the output port P2 is maintained at the drain pressure.

[0172] If the solenoid 12 fails, the biasing force of the solenoid 12 is lost, and the first switching valve 530 is switched from the normal position L to the fail position M by the biasing force of the spring 14. As a result, the output port P2 and the drain port P3 are connected, and the pressure in the output port P2 becomes the tank pressure. This enables the horsepower control by the horsepower control mechanism M2.

[0173] If the solenoid 12 fails, the secondary pressure output from the electromagnetic proportional pressure reducing valve 20 drops, causing the pressure in the pressure chamber 508a of the flow control mechanism M11 to drop. As a result, the flow control mechanism M11 requests the pump P to deliver the maximum discharge flow rate.

[0174] The operation of the flow control device 500 other than the flow control mechanism M11 related to the flow control unit M is the same as that of the flow control devices 100, 200, 300, and 400, and therefore will not be described.

[0175] The valve device 510 and the flow rate control device 500 according to the second embodiment configured as described above have the following advantages.

[0176] In the flow control device 500, under normal conditions, that is, when the solenoid 12 is not malfunctioning, the flow rate is controlled by the flow rate control mechanism M11, and when the solenoid 12 is malfunctioning, the horsepower control mechanism M2 controls the horsepower. This allows the flow rate of the pump P to be reliably controlled even when the solenoid 12 is malfunctioning.

[0177] Furthermore, in the valve device 510 of this embodiment, the electromagnetic proportional pressure reducing valve 20 and the first switching valve 530 are formed integrally, and further, the valve element of the electromagnetic proportional pressure reducing valve 20 and the valve element of the first switching valve 530 are configured integrally by a single spool 13. This allows the valve device 510 to be made smaller, and the number of parts to be reduced, thereby reducing costs.

[0178] Next, a flow control device 600, which is a modified example of the flow control device 500, will be described with reference to FIG.

[0179] The flow control device 500 described above is provided with a valve device 510, whereas the flow control device 600 of this modified example differs from the flow control device 500 in that it includes the valve device 10 of the first embodiment. Furthermore, the flow control device 500 described above is provided with a locking mechanism 50, whereas the flow control device 600 of this modified example differs from the flow control device 500 in that it includes the locking mechanism 450 of the flow control device 400, which is a modified example of the first embodiment. Below, only the differences from the other embodiments will be described, and the same components will be assigned the same numbers and will not be described again. Note that the configurations and operations of the valve device 10 and the locking mechanism 450 have also been described in the above embodiment and modified examples, so description thereof will be omitted here.

[0180] The operation of the flow rate control device 600 will now be described.

[0181] When the solenoid 12 is normal, as described above, the first switching valve 30 is switched to the normal position D. In the normal position D, the output port P2 is in communication with the tank T, and therefore the pressure chamber 450a of the locking mechanism 450 is in communication with the tank T through the passage 462 and the first switching valve 30. Therefore, the horsepower control by the horsepower control mechanism M2 is disabled.

[0182] Furthermore, the secondary pressure (input pressure Pi) is supplied to the pressure chamber 508a of the flow rate control mechanism M11 from the secondary pressure port P4 of the electromagnetic proportional pressure reducing valve 20 through a passage 562. In this way, flow rate control is performed by the flow rate control mechanism M11.

[0183] On the other hand, if the solenoid 12 fails, the biasing force of the solenoid 12 is lost, and the first switching valve 30 is switched from the normal position D to the fail position E by the biasing force of the spring 14. When the first switching valve 30 switches from the normal position D to the fail position E, the primary pressure is supplied to the pressure chamber 450a of the lock mechanism 450 through the output port P2 of the first switching valve 30 and the passage 462. This enables horsepower control by the horsepower control mechanism M2.

[0184] If the solenoid 12 fails, the secondary pressure output from the electromagnetic proportional pressure reducing valve 20 drops, causing the pressure in the pressure chamber 8a of the flow control mechanism M1 to drop. As a result, the flow control mechanism M11 requests the pump P to deliver the maximum discharge flow rate.

[0185] Other operations related to the flow control unit M of the flow control device 600 are the same as those of the flow control device 500, and therefore will not be described.

[0186] The flow control device 600 according to the above-described modified example also achieves the same effects as the flow control device 500 .

[0187] Third Embodiment A valve device 710 and a flow rate control device 700 including the valve device 710 according to a third embodiment will be described with reference to FIGS. 9 and 10A to 10C.

[0188] The flow control device 100 according to the first embodiment was equipped with a direct proportional type electromagnetic proportional pressure reducing valve 20 and a first switching valve 30, but the flow control device 700 according to the third embodiment differs from the valve device 10 according to the first embodiment in that it is equipped with an inverse proportional type electromagnetic proportional pressure reducing valve 720 and a first switching valve 730.

[0189] In the following, only the differences from the valve device 10 and the flow control device 100 will be described, and the same components will be assigned the same numbers and will not be described again.

[0190] As shown in FIG. 9 , the valve device 710 includes a solenoid 12, an electromagnetic proportional pressure reducing valve 720 that reduces the primary pressure and adjusts it to a secondary pressure corresponding to a command current applied to the solenoid 12, and a first switching valve 730 that can be switched to a normal position N or a fail position O according to the biasing force generated by the solenoid 12.

[0191] The electromagnetic proportional pressure reducing valve 720 of this embodiment is an inverse proportional type electromagnetic proportional pressure reducing valve that outputs a smaller secondary pressure as the command current applied to the solenoid 12 increases.

[0192] The specific configuration of the valve device 710 will be described with reference to Figures 9 and 10A-10C. Figure 10A is a cross-sectional view showing the main parts of the valve device 710 when the solenoid 12 is not energized. Figure 10B is a cross-sectional view showing the main parts of the valve device 710 when the solenoid 12 is energized. Figure 10C is a cross-sectional view showing the main parts of the valve device 710 when the electromagnetic proportional pressure reducing valve 720 has reached the set pressure.

[0193] As shown in FIGS. 10A, 10B, and 10C, the valve device 710 includes a housing 711, a solenoid 12, a spool 713 as a valve body, and a spring 14.

[0194] The housing 711 is provided with a cylindrical accommodation hole 711a that slidably accommodates the spool 713. A spring 14 that urges the spool 713 in the +Y direction is provided on one end face side of the spool 713. A solenoid 12 that urges the spool 713 in the -Y direction is provided on the other end face side of the spool 713.

[0195] The housing 711 is further provided with an input port P1 to which primary pressure (hydraulic oil from the hydraulic power source) is introduced, an output port P2, a drain port P3 communicating with the tank T, and a secondary pressure port P4 from which adjusted secondary pressure is output by reducing the primary pressure (see also FIG. 9).

[0196] The spool 713 is biased in the +Y direction by the biasing force of the spring 14 and pressed against the plunger 12a of the solenoid 12. In other words, the plunger 12a of the solenoid 12 and the other end face of the spool 713 are always in contact with each other. Therefore, when the current applied to the solenoid 12 changes and the plunger 12a moves, the position of the spool 713 changes.

[0197] As shown in Figures 10A, 10B, and 10C, the spool 713 includes a first land portion 713a, a second land portion 713b, a third land portion 713c, a communication passage 713d extending in the axial direction of the spool 713 and communicating between a space 711b facing one end face of the spool 713 and a space 711c facing the other end face of the spool 713, a first annular groove 713e formed between the first land portion 713a and the second land portion 713b, and a second annular groove 713f formed between the second land portion 713b and the third land portion 713c.

[0198] The first land portion 713a, the second land portion 713b, and the third land portion 713c are provided at intervals in the axial direction in that order from the solenoid 12 side. The first land portion 713a is formed in a tapered shape that decreases in diameter toward the other end face (solenoid 12 side) of the spool 713. The outer diameter of a portion of the first land portion 713a that faces the second land portion 713b across the first annular groove 713e is smaller than the outer diameter of the second land portion 713b, and the second land portion 713b and the third land portion 713c are formed to have the same outer diameter.

[0199] The first land portion 713a controls communication between the secondary pressure port P4 and the drain port P3. The second land portion 713b controls communication between the input port P1 and the secondary pressure port P4. The third land portion 713c controls communication between the input port P1 and the output port P2, and communication between the output port P2 and the drain port P3.

[0200] The space 711b is formed in the receiving hole 711a as a space for receiving the spring 14. The space 711b is always in communication with the drain port P3 through a communication passage 713d.

[0201] The space 711c is provided on the solenoid 12 side of the accommodation hole 711a, and is defined by the housing 711, the solenoid 12, and the spool 713 (first land portion 713a). The space 711c is constantly in communication with the drain port P3.

[0202] In this embodiment, the solenoid 12, the spring 14, the input port P1, the secondary pressure port P4, the drain port P3, the first land portion 713a of the spool 713, and the second land portion 713b of the spool 713 constitute an electromagnetic proportional pressure reducing valve 720. Furthermore, the solenoid 12, the spring 14, the input port P1, the output port P2, the drain port P3, and the third land portion 713c of the spool 713 constitute a first switching valve 730. That is, in the valve device 710 of this embodiment, the electromagnetic proportional pressure reducing valve 720 and the first switching valve 730 are integrally formed, and the valve bodies of the electromagnetic proportional pressure reducing valve 720 and the first switching valve 730 are integrally formed by the single spool 713. Furthermore, the electromagnetic proportional pressure reducing valve 720 and the first switching valve 730 are controlled by the single solenoid 12.

[0203] The operation of the valve device 710 configured in this manner will now be described.

[0204] When no current is applied to the solenoid 12, the spool 713 is in the position shown in FIG. 10A . Specifically, the first land portion 713a blocks communication between the secondary pressure port P4 and the drain port P3, while the input port P1 and the secondary pressure port P4 are connected. In this state, the pressure at the secondary pressure port P4 is equal to the primary pressure (the pressure at the input port P1). Furthermore, the third land portion 713c blocks communication between the input port P1 and the output port P2, while connecting the output port P2 and the drain port P3. In the position shown in FIG. 10A , the input port P1 and the secondary pressure port P4 are connected, so that hydraulic oil from the hydraulic source is supplied to the pressure chamber 8a of the flow control mechanism M1 through the input port P1, the secondary pressure port P4, and the passage 762 (see also FIG. 9 ). In addition, in the position shown in FIG. 10A, the output port P2 and the drain port P3 are in communication with each other, so the pressure in the pressure chamber 50a of the lock mechanism 50 is the tank pressure (see also FIG. 9).

[0205] As described above, the outer diameter of the first land portion 713a, which faces the second land portion 713b across the first annular groove 713e of the spool 713, is smaller than the outer diameter of the second land portion 713b. Therefore, when secondary pressure acts on these portions, a biasing force acts on the spool 713 in the −Y direction (leftward) in FIG. 10A due to the difference in their pressure-receiving areas. This biasing force biases the spool 713 in opposition to the biasing force of the spring 14. In other words, the pressure acting on the difference in the pressure-receiving areas between the first land portion 713a and the second land portion 713b corresponds to the feedback pressure in the electromagnetic proportional pressure-reducing valve 720. Note that the configuration related to this difference in the pressure-receiving areas between the first land portion 713a and the second land portion 713b corresponds to the "feedback section" in the claims.

[0206] In the valve device 710, the spring load of the spring 14 is set so that the biasing force in the +Y direction by the spring 14 exceeds the biasing force in the −Y direction by the feedback pressure when no current is applied to the solenoid 12. As a result, when no current is applied to the solenoid 12, the spool 713 is maintained in the position shown in FIG.

[0207] When the operating lever 41 is operated and a command current is applied from the controller C to the solenoid 12, the sum of the biasing force of the solenoid 12 and the biasing force of the feedback pressure exceeds the biasing force of the spring 14, and the spool 713 moves from the position shown in FIG. 10A to the position shown in FIG. 10B (in the −Y direction). As a result, communication between the input port P1 and the secondary pressure port P4 is blocked, and communication between the secondary pressure port P4 and the drain port P3 is established. Furthermore, 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 by the third land portion 713c.

[0208] When the secondary pressure port P4 and the drain port P3 communicate with each other, the hydraulic oil in the pressure chamber 8a, the passage 762, and the secondary pressure port P4 is discharged to the tank T, and the pressure in the secondary pressure port P4 decreases. Furthermore, when the input port P1 and the output port P2 communicate with each other, the hydraulic oil in the input port P1 is supplied to the pressure chamber 50a of the lock mechanism 50 through the output port P2 and the passage 761. This disables the horsepower control by the horsepower control mechanism M2.

[0209] When the pressure in the secondary pressure port P4 decreases and the spool 713 moves to a position (the position shown in FIG. 10C) where the total biasing force of the feedback pressure acting on the spool 713 in the -Y direction and the biasing force of the solenoid 12 in the -Y direction balances with the biasing force of the spring 14 in the +Y direction, the first land portion 713a blocks communication between the secondary pressure port P4 and the drain port P3, and the discharge of hydraulic oil from the secondary pressure port P4 stops. In the state shown in FIG. 10C, the input port P1 and the output port P2 are maintained in communication.

[0210] In the valve device 710, the first switching valve 730 is used to detect a failure of the solenoid 12. This will be explained in detail below.

[0211] 9, the first switching valve 730 has a normal position N (corresponding to the position shown in FIGS. 10B and 10C) and a fail position O (corresponding to the position shown in FIG. 10A). In the normal position N, the input port P1 and the output port P2 are in communication with each other, and the output port P2 and the drain port P3 are in communication with each other. In the fail position O, the input port P1 and the output port P2 are in communication with each other, and the output port P2 and the drain port P3 are in communication with each other.

[0212] In this embodiment, even if the control lever 41 is not operated, when the pump unit PU is operating, a minimum command current is applied to the solenoid 12. When the minimum command current is applied to the solenoid 12 of the valve device 710, the first switching valve 730 is switched to the normal position N. Therefore, when the pump unit PU is operating, the first switching valve 730 is maintained in the normal position N regardless of whether the control lever 41 is operated. As a result, the output port P2 is maintained at the primary pressure.

[0213] If the solenoid 12 fails, the biasing force of the solenoid 12 is lost, and the first switching valve 730 is switched from the normal position N to the fail position O by the biasing force of the spring 14. This allows the output port P2 to communicate with the drain port P3, and the hydraulic oil in the pressure chamber 50a of the locking mechanism 50 is discharged to the tank T through the passage 761 and the first switching valve 730. As a result, horsepower control by the horsepower control mechanism M2 becomes effective.

[0214] If the solenoid 12 fails, the secondary pressure output from the electromagnetic proportional pressure reducing valve 720 becomes maximum (becomes the primary pressure), causing the pressure chamber 8a of the flow control mechanism M1 to rise, thereby requesting the pump P to deliver the maximum discharge flow rate by the flow control mechanism M1.

[0215] Other operations related to the flow control unit M of the flow control device 700 are the same as those of the flow control device 100, and therefore will not be described.

[0216] The valve device 710 and the flow rate control device 700 according to the third embodiment configured as above have the following advantages.

[0217] In the flow control device 700, under normal conditions, that is, when the solenoid 12 is not malfunctioning, the flow rate is controlled by the flow rate control mechanism M1, and when the solenoid 12 is malfunctioning, the horsepower control mechanism M2 controls the horsepower. This allows the flow rate of the pump P to be reliably controlled even when the solenoid 12 is malfunctioning.

[0218] Furthermore, in the valve device 710 of this embodiment, the electromagnetic proportional pressure reducing valve 720 and the first switching valve 730 are formed integrally, and further, the valve element of the electromagnetic proportional pressure reducing valve 720 and the valve element of the first switching valve 730 are configured integrally by a single spool 713. This allows the valve device 710 to be made smaller, and the number of parts is reduced, resulting in cost reduction.

[0219] Furthermore, even when the inverse proportional type electromagnetic proportional pressure reducing valve 720 is used, the same effects as when the direct proportional type electromagnetic proportional pressure reducing valves 20, 520 are used can be achieved.

[0220] Fourth Embodiment Next, a valve device 810 according to a fourth embodiment and a flow rate control device 800 including the valve device 810 will be described with reference to FIGS. 11 and 12A to 12C.

[0221] In the flow control device 700 according to the third embodiment, the first switching valve 730 of the valve device 710 is configured to connect the output port P2 and the drain port P3 when the first switching valve 730 is in the fail position O, but in the flow control device 800 according to the fourth embodiment, the first switching valve 830 of the valve device 810 is configured to connect the input port P1 and the output port P2 when the first switching valve 830 is in the fail position Q, which is different from the flow control device 700 according to the third embodiment. Furthermore, while the flow control device 700 according to the third embodiment is provided with a lock mechanism 50, the flow control device 800 according to the fourth embodiment is provided with a lock mechanism 450, which is different from the flow control device 700 according to the third embodiment.

[0222] In the following, only the differences from other embodiments will be described, and the same components will be assigned the same numbers and descriptions thereof will be omitted.

[0223] As shown in FIG. 11, the valve device 810 includes a solenoid 12, an electromagnetic proportional pressure reducing valve 820 that reduces the primary pressure and adjusts it to a secondary pressure corresponding to a command current applied to the solenoid 12, and a first switching valve 830 that can be switched to a normal position P or a fail position Q according to the biasing force generated by the solenoid 12.

[0224] The electromagnetic proportional pressure reducing valve 820 of this embodiment is an inverse proportional type electromagnetic proportional pressure reducing valve that outputs a smaller secondary pressure as the command current applied to the solenoid 12 increases.

[0225] The specific configuration of the valve device 810 will be described with reference to Figures 11 and 12A-12C. Figure 12A is a cross-sectional view showing the main parts of the valve device 810 when the solenoid 12 is not energized. Figure 12B is a cross-sectional view showing the main parts of the valve device 810 when the solenoid 12 is energized. Figure 12C is a cross-sectional view showing the main parts of the valve device 810 when the electromagnetic proportional pressure reducing valve 820 has reached the set pressure.

[0226] As shown in FIGS. 12A, 12B, and 12C, the valve device 810 includes a housing 811, a solenoid 12, a spool 813 as a valve body, and a spring 14.

[0227] The housing 811 is provided with a cylindrical accommodation hole 811a that slidably accommodates the spool 813. A spring 14 that urges the spool 813 in the +Y direction is provided on one end face side of the spool 813. A solenoid 12 that urges the spool 813 in the -Y direction is provided on the other end face side of the spool 813.

[0228] The housing 811 is further provided with an input port P1 to which primary pressure (hydraulic oil from the hydraulic power source) is introduced, an output port P2, a drain port P3 communicating with the tank T, and a secondary pressure port P4 from which adjusted secondary pressure is output by reducing the primary pressure (see also FIG. 11).

[0229] The spool 813 is biased in the +Y direction by the biasing force of the spring 14 and pressed against the plunger 12a of the solenoid 12. In other words, the plunger 12a of the solenoid 12 and the other end face of the spool 813 are always in contact with each other. Therefore, when the current applied to the solenoid 12 changes and the plunger 12a moves, the position of the spool 813 changes.

[0230] As shown in Figures 12A, 12B, and 12C, the spool 813 includes a first land portion 813a, a second land portion 813b, a third land portion 813c, a fourth land portion 813h, a communication passage 813d extending in the axial direction of the spool 813 and communicating between a space 811b facing one end face of the spool 813 and a space 811c facing the other end face of the spool 813, a first annular groove 813e formed between the first land portion 813a and the second land portion 813b, a second annular groove 813f formed between the second land portion 813b and the third land portion 813c, and a third annular groove 813g formed between the third land portion 813c and the fourth land portion 813h.

[0231] The first land portion 813a, the second land portion 813b, the third land portion 813c, and the fourth land portion 813h are provided at intervals in the axial direction in that order from the solenoid 12 side. The first land portion 813a is formed in a tapered shape that decreases in diameter toward the other end face (solenoid 12 side) of the spool 813. The outer diameter of a portion of the first land portion 813a facing the second land portion 813b across the first annular groove 813e is smaller than the outer diameter of the second land portion 813b, and the second land portion 813b, the third land portion 813c, and the fourth land portion 813h are formed to have the same outer diameter.

[0232] The first land portion 813a controls communication between the secondary pressure port P4 and the drain port P3. The second land portion 813b controls communication between the input port P1 and the secondary pressure port P4. The third land portion 813c controls communication between the input port P1 and the output port P2. The fourth land portion 813h controls communication between the output port P2 and the drain port P3.

[0233] The space 811b is formed in the receiving hole 811a as a space for receiving the spring 14. The space 811b is always in communication with the drain port P3 through a communication passage 813d.

[0234] The space 811c is provided on the solenoid 12 side of the accommodation hole 811a, and is defined by the housing 811, the solenoid 12, and the spool 813 (first land portion 813a). The space 811c is constantly in communication with the drain port P3.

[0235] In this embodiment, the solenoid 12, the spring 14, the input port P1, the secondary pressure port P4, the drain port P3, the first land portion 813a of the spool 813, and the second land portion 813b of the spool 813 constitute an electromagnetic proportional pressure reducing valve 820. Furthermore, the solenoid 12, the spring 14, the input port P1, the output port P2, the drain port P3, the third land portion 813c of the spool 813, and the fourth land portion 813h of the spool 813 constitute a first switching valve 830. That is, in the valve device 810 of this embodiment, the electromagnetic proportional pressure reducing valve 820 and the first switching valve 830 are integrally configured, and the valve bodies of the electromagnetic proportional pressure reducing valve 820 and the first switching valve 830 are integrally configured by the single spool 813. Furthermore, the electromagnetic proportional pressure reducing valve 820 and the first switching valve 830 are controlled by the single solenoid 12.

[0236] The operation of the valve device 810 configured in this manner will now be described.

[0237] When no current is applied to the solenoid 12, the spool 813 is in the position shown in FIG. 12A. Specifically, the first land portion 813a blocks communication between the secondary pressure port P4 and the drain port P3, and the input port P1 and the secondary pressure port P4 are connected. In this state, the pressure at the secondary pressure port P4 is equal to the primary pressure (the pressure at the input port P1). Furthermore, the input port P1 and the output port P2 are connected, and the fourth land portion 813h blocks communication between the output port P2 and the drain port P3.

[0238] 12A, the input port P1 and the secondary pressure port P4 are in communication with each other, so that hydraulic oil from the hydraulic power source passes through the input port P1, the secondary pressure port P4, and the passage 862 to be supplied to the pressure chamber 8a of the flow rate control mechanism M1 (see FIG. 11). In addition, the input port P1 and the output port P2 are in communication with each other, so that hydraulic oil from the hydraulic power source passes through the input port P1, the output port P2, and the passage 862 to be supplied to the pressure chamber 450a of the lock mechanism 450 (see FIG. 11).

[0239] As described above, the outer diameter of the first land portion 813a, which faces the second land portion 813b across the first annular groove 813e of the spool 813, is smaller than the outer diameter of the second land portion 813b. Therefore, when secondary pressure acts on these portions, a biasing force acts on the spool 813 in the −Y direction (leftward) in FIG. 12A due to the difference in their pressure-receiving areas. This biasing force biases the spool 13 in opposition to the biasing force of the spring 14. In other words, the pressure acting on the difference in pressure-receiving areas between the first land portion 813a and the second land portion 813b corresponds to the feedback pressure in the electromagnetic proportional pressure-reducing valve 820. Note that the configuration related to this difference in pressure-receiving areas between the first land portion 813a and the second land portion 813b corresponds to the “feedback section” in the claims.

[0240] In the valve device 810, the spring load of the spring 14 is set so that the biasing force in the +Y direction by the spring 14 exceeds the biasing force in the −Y direction by the feedback pressure when no current is applied to the solenoid 12. As a result, when no current is applied to the solenoid 12, the spool 813 is maintained in the position shown in FIG.

[0241] When the operating lever 41 is operated and a command current is applied from the controller C to the solenoid 12, the sum of the biasing force of the solenoid 12 and the biasing force of the feedback pressure exceeds the biasing force of the spring 14, and the spool 813 moves from the position shown in FIG. 12A to the position shown in FIG. 12B (in the −Y direction). This blocks communication between the input port P1 and the secondary pressure port P4, and connects the secondary pressure port P4 to the drain port P3. Furthermore, the third land portion 813c blocks communication between the input port P1 and the output port P2, and connects the output port P2 to the drain port P3.

[0242] When the secondary pressure port P4 and the drain port P3 communicate with each other, the hydraulic oil in the pressure chamber 8a, the passage 862, and the secondary pressure port P4 is discharged to the tank T, and the pressure in the secondary pressure port P4 decreases. Furthermore, when the output port P2 and the drain port P3 communicate with each other, the hydraulic oil in the pressure chamber 450a of the locking mechanism 450 is discharged to the tank T through the passage 861, the output port P2, and the drain port P3. This disables the horsepower control by the horsepower control mechanism M2.

[0243] When the pressure in the secondary pressure port P4 decreases and the spool 813 moves to a position (the position shown in FIG. 12C) where the total biasing force of the feedback pressure acting on the spool 813 in the -Y direction and the biasing force of the solenoid 12 in the -Y direction balances with the biasing force of the spring 14 in the +Y direction, the first land portion 813a blocks communication between the secondary pressure port P4 and the drain port P3, and the discharge of hydraulic oil from the secondary pressure port P4 stops. Note that in the state shown in FIG. 12C, communication between the input port P1 and the output port P2 is maintained blocked.

[0244] In the valve device 810, the first switching valve 830 is used to detect a failure of the solenoid 12. This will be explained in detail below.

[0245] 11, the first switching valve 830 has a normal position P (corresponding to the position shown in FIGS. 12B and 12C) and a fail position Q (corresponding to the position shown in FIG. 12A). In the normal position P, 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. In the fail position Q, 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.

[0246] In this embodiment, even if the control lever 41 is not operated, when the pump unit PU is operating, a minimum command current is applied to the solenoid 12. When the minimum command current is applied to the solenoid 12 of the valve device 810, the first switching valve 830 is switched to the normal position P. Therefore, when the pump unit PU is operating, the first switching valve 830 is maintained in the normal position P regardless of whether the control lever 41 is operated. As a result, the output port P2 is maintained at the tank pressure.

[0247] If the solenoid 12 fails, the biasing force of the solenoid 12 is lost, and the first switching valve 830 is switched from the normal position P to the fail position Q by the biasing force of the spring 14. This connects the input port P1 and the output port P2, and hydraulic oil from the hydraulic source is supplied to the pressure chamber 450a of the lock mechanism 450. As a result, horsepower control by the horsepower control mechanism M2 becomes effective.

[0248] If the solenoid 12 fails, the secondary pressure output from the electromagnetic proportional pressure reducing valve 820 will be maximized (become the primary pressure), causing the pressure chamber 8a of the flow control mechanism M1 to rise, resulting in a state in which the flow control mechanism M1 requests the pump P to deliver the maximum discharge flow rate.

[0249] Other operations of the flow control unit M of the flow control device 800 are the same as those of the other embodiments, and therefore will not be described.

[0250] The valve device 810 and the flow control device 800 in the fourth embodiment configured as described above can also achieve the same effects as the flow control device 700 in the third embodiment.

[0251] It is also possible to combine the above embodiments. For example, in the flow control device 200 and the flow control device 400 shown in Figures 3 and 5, the valve device 10 can be the valve device 810 shown in Figure 11, and the flow control mechanism M1 can be the flow control mechanism M11.

[0252] Furthermore, as shown as a flow control device 900 in FIG. 13, the configuration related to the locking mechanism 450 of the flow control device 400 shown in FIG. 5 may be adopted instead of the configuration related to the locking mechanism 50 in the flow control device 100 shown in FIG. 1.

[0253] The configuration, operation, and effects of the embodiment of the present invention configured as above will be described below.

[0254] The valve device 10, 510, 710, 810 includes a solenoid 12, an electromagnetic proportional pressure reducing valve 20, 720, 820 that reduces the primary pressure and adjusts it to a secondary pressure corresponding to a command current applied to the solenoid 12, and a first switching valve 30, 530, 730, 830 that has normal positions D, L, N, P and fail positions E, M, O, Q that are switched according to the biasing force generated by the solenoid 12 and that switches from the normal position D, L, N, P to the fail position E, M, O, Q when the solenoid 12 fails, and the valve element of the electromagnetic proportional pressure reducing valve 20, 720, 820 and the valve element of the first switching valve 30, 530, 730, 830 are connected to one spool 13, 513, 7 13, 813, and the first switching valve 30, 530, 730, 830 has an input port P1 to which primary pressure is introduced on the upstream side, an output port P2 on the downstream side, and a drain port P3 that communicates with the tank T. When the first switching valve 30, 530, 730, 830 switches from the normal position D, L, N, P to the fail position E, M, O, Q, the communication between the output port P2 and the drain port P3 switches to communication between the output port P2 and the input port P1, or the communication between the output port P2 and the input port P1 switches to communication between the output port P2 and the drain port P3, and the pressure on the output port P2 side changes.

[0255] This configuration makes it possible to reduce the size of the valve device 10, 510, 710, 810. The valve element of the electromagnetic proportional pressure reducing valve 20, 720, 820 and the valve element of the first selector valve 30, 530, 730, 830 are integrally configured by a single spool 13, 513, 713, 813, so it is possible to reduce the number of flow paths, accommodation holes for accommodating the valve elements, etc., compared to when the electromagnetic proportional pressure reducing valve 20, 720, 820 and the first selector valve 30, 530, 730, 830 are each provided with a spool 13, 513, 713, 813. Furthermore, the first switching valve 30, 530, 730, 830 is switched by a solenoid 12 that adjusts the secondary pressure of the electromagnetic proportional pressure reducing valve 20, 720, 820, and when the solenoid 12 fails, it mechanically switches from a normal position D, L, N, P to a fail position E, M, O, Q, thereby changing the pressure on the output port P2 side. As a result, for example, by detecting the pressure on the output port P2 side, it is possible to detect a failure of the solenoid 12. Furthermore, by enabling or disabling control of the horsepower control mechanism M2 based on the pressure on the output port P2 side depending on whether the first switching valve 30, 530, 730, 830 is in the normal position D, L, N, P or the fail position E, M, O, Q, automatic switching can be performed when the solenoid 12 fails.

[0256] The valve device 10, 510, 710, 810 further has a secondary pressure port P4 from which secondary pressure is output, and the electromagnetic proportional pressure reducing valve 20, 720, 820 and the first switching valve 30, 530, 730, 830 have a common input port P1, and the communication between the output port P2 and the input port P1 and the communication between the secondary pressure port P4 and the input port P1 are controlled by the spool 13, 513, 713, 813.

[0257] In this configuration, communication is controlled according to the position of the spool 13, 513, 713, 813, so the input port P1 of the valve device 10, 510, 710, 810 can be unified, eliminating the need to configure a separate flow path for directing primary pressure to the input port P1. This allows the valve device 10, 510, 710, 810 to be made smaller.

[0258] The valve device 10 further has a secondary pressure port P4 from which secondary pressure is output, a spring 14 that urges the spool 13 in a second direction that is opposite to the first direction in which the solenoid 12 urges the spool 13, and a feedback section in which the secondary pressure acts to urge the spool 13 in the second direction, and the spool 13 has a first land section 13a for connecting or blocking the secondary pressure port P4 and the drain port P3, a second land section 13b that is provided at a distance from the first land section 13a and for connecting or blocking the input port P1 and the secondary pressure port P4, and a third land section 13c that is provided at a distance from the second land section 13b and for selectively connecting either the input port P1 or the drain port P3 to the output port P2.

[0259] The valve device 810 further has a secondary pressure port P4 from which the secondary pressure is output, a spring 14 that urges the spool 813 in a second direction that is opposite to the first direction in which the solenoid 12 urges the spool 813, and a feedback section in which the secondary pressure acts to urge the spool 813 in the first direction, and the spool 813 has a first land section 813a for connecting or blocking the secondary pressure port P4 and the drain port P3, a second land section 813b that is provided at a distance from the first land section 813a and for connecting or blocking the input port P1 and the secondary pressure port P4, a third land section 813c that is provided at a distance from the second land section 813b and for connecting or blocking the input port P1 and the output port P2, and a fourth land section 813h that is provided at a distance from the third land section 813c and for connecting or blocking the output port P2 and the drain port P3.

[0260] The valve device 510 further has a secondary pressure port P4 from which the secondary pressure is output, a spring 14 that urges the spool 513 in a second direction that is opposite to the first direction in which the solenoid 12 urges the spool 513, and a feedback section in which the secondary pressure acts to urge the spool 513 in the second direction, and the spool 513 has a first land section 513a for connecting or blocking the secondary pressure port P4 and the drain port P3, a second land section 513b that is provided on the first land section 513a with a gap therebetween and for connecting or blocking the input port P1 and the secondary pressure port P4, a third land section 513c that is provided on the second land section 513b with a gap therebetween and for connecting or blocking the input port P1 and the output port P2, and a fourth land section 513h that is provided on the third land section 513c with a gap therebetween and for connecting or blocking the output port P2 and the drain port P3.

[0261] The valve device 710 further has a secondary pressure port P4 from which secondary pressure is output, a spring 14 that urges the spool 713 in a second direction that is opposite to the first direction in which the solenoid 12 urges the spool 713, and a feedback section in which the secondary pressure acts to urge the spool 713 in the first direction, and the spool 713 has a first land section 713a for connecting or blocking the secondary pressure port P4 and the drain port P3, a second land section 713b that is provided at a distance from the first land section 713a and for connecting or blocking the input port P1 and the secondary pressure port P4, and a third land section 713c that is provided at a distance from the second land section 713b and for selectively connecting either the input port P1 or the drain port P3 to the output port P2.

[0262] According to these configurations, each port P1 to P4 is switched using a single spool 13, 513, 713, 813 on which each land 13a to 13c, 513a to 513c, 513h, 713a to 713c, 713h, 813a to 813c is formed. Therefore, compared to a configuration using multiple spools, for example, the number of ports can be reduced, and the valve device 10, 510, 710, 810 can be made smaller.

[0263] The valve device 10, 510, 710, 810 further includes a communication passage 13d, 513d, 713d, 813d formed to penetrate the spool 13, 513, 713, 813 and directing the hydraulic fluid discharged from the output port P2 to the drain port P3.

[0264] According to this configuration, the hydraulic fluid discharged from the output port P2 can be discharged by joining it with the drain port P3 through the communication passages 13d, 513d, 713d, 813d formed in the spool 13, 513, 713, 813. This allows the number of ports formed in the housing 11, 511, 711, 811 to be reduced, thereby enabling the valve device 10, 510, 710, 810 to be made more compact.

[0265] The flow control devices 100, 200, 300, 500, 700 each include a valve device 10, 510, 710, a flow control mechanism M1, M11 that controls the flow rate of the pump P according to the secondary pressure, and a horsepower control mechanism M2 that controls the horsepower of the pump P when the solenoid 12 fails. The horsepower control mechanism M2 has a lock pin 50b, 450b that enables or disables the control of the horsepower control mechanism M2. When the valve device 10, 510, 710 is normal, the secondary pressure or the primary pressure acts on the lock pin 50b, 450b, disabling the control of the horsepower control mechanism M2. When the solenoid 12 fails, the secondary pressure or the primary pressure no longer acts on the lock pin 50b, 450b, enabling the control of the horsepower control mechanism M2.

[0266] According to this configuration, even if the solenoid 12 fails and the secondary pressure cannot be controlled by the electromagnetic proportional pressure reducing valve 20, 720, the pump P can be controlled by switching to horsepower control.

[0267] The flow control devices 200, 300 further include a second switching valve (switching valve 240, switching valve 341) that is switched depending on the pressure output from the output port P2, and the second switching valve (switching valve 240, switching valve 341) supplies primary pressure to the lock pin 50b of the horsepower control mechanism M2 when the valve device 10 is normal, and is switched to discharge the pressure acting on the lock pin 50b of the horsepower control mechanism M2 when the solenoid 12 fails.

[0268] The flow control devices 400, 600, 800, 900 each include a valve device 10, a flow control mechanism M1, M11 that controls the flow rate of the pump P according to the secondary pressure, and a horsepower control mechanism M2 that controls the horsepower of the pump P when the solenoid 12 fails. The horsepower control mechanism M2 has a lock pin 450b that enables or disables the control of the horsepower control mechanism M2. When the valve devices 10, 810 are normal, the secondary pressure or primary pressure does not act on the lock pin 450b, thereby disabling the control of the horsepower control mechanism M2. When the solenoid 12 fails, the primary pressure acts on the lock pin 450b, thereby enabling the control of the horsepower control mechanism M2.

[0269] According to this configuration, even if the solenoid 12 fails and the secondary pressure cannot be controlled by the electromagnetic proportional pressure reducing valve 20, 820, the pump P can be controlled by switching to horsepower control.

[0270] The flow control devices 100, 300, 400 further include a high-pressure selection valve 40, 342 that selects the higher pressure from the secondary pressure and the pressure output from the output port P2 and outputs the selected pressure to the flow control mechanism.

[0271] According to this configuration, since the high pressure selection valves 40, 342 are employed, the device can be made smaller than when control is performed using a switching valve.

[0272] The flow control devices 200, 400 further include a second switching valve (switching valve 240, switching valve 440) that is switched depending on the pressure output from the output port P2, and the second switching valve (switching valve 240, switching valve 440) supplies secondary pressure to the flow control mechanism M1 when the valve device 10 is normal, and supplies primary pressure to the flow control mechanism M1 when the solenoid 12 fails.

[0273] 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.

[0274] This application claims priority based on Japanese Patent Application No. 2023-158373, filed with the Japan Patent Office on September 22, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A valve device comprising: a solenoid; an electromagnetic proportional pressure reducing valve which reduces primary pressure and adjusts it to a secondary pressure corresponding to a command current applied to the solenoid; and a first switching valve which has a normal position and a fail position which are switched according to the biasing force generated by the solenoid, and which switches from the normal position to the fail position when the solenoid fails, wherein the valve body of the electromagnetic proportional pressure reducing valve and the valve body of the first switching valve are integrally formed by a single spool, and the first switching valve has an input port to which primary pressure is introduced on the upstream side, an output port on the downstream side, and a drain port communicating with a tank, and when the first switching valve switches from the normal position to the fail position, communication between the output port and the drain port switches to communication between the output port and the input port, or communication between the output port and the input port switches to communication between the output port and the drain port, thereby changing the pressure on the output port side.

2. A valve device as described in claim 1, further comprising a secondary pressure port from which the secondary pressure is output, the electromagnetic proportional pressure reducing valve and the first switching valve having a common input port, and the communication between the output port and the input port and the communication between the secondary pressure port and the input port are controlled by the spool.

3. A valve device as described in claim 1, further comprising: a secondary pressure port from which the secondary pressure is output; a spring which urges the spool in a second direction which is opposite to the first direction in which the solenoid urges the spool; and a feedback section in which the secondary pressure acts to urge the spool in the second direction, wherein the spool has: a first land section for connecting or blocking the secondary pressure port and the drain port; a second land section provided at a distance from the first land section, for connecting or blocking the input port and the secondary pressure port; and a third land section provided at a distance from the second land section, for selectively connecting either the input port or the drain port to the output port.

4. A valve device as claimed in claim 1, further comprising: a secondary pressure port from which the secondary pressure is output; a spring which urges the spool in a second direction which is opposite to the first direction in which the solenoid urges the spool; and a feedback section in which the secondary pressure acts to urge the spool in the first direction, wherein the spool has: a first land section for connecting or blocking the secondary pressure port and the drain port; a second land section which is provided at a distance from the first land section and for connecting or blocking the input port and the secondary pressure port; a third land section which is provided at a distance from the second land section and for connecting or blocking the input port and the output port; and a fourth land section which is provided at a distance from the third land section and for connecting or blocking the output port and the drain port.

5. A valve device as claimed in claim 1, further comprising: a secondary pressure port from which the secondary pressure is output; a spring which urges the spool in a second direction which is opposite to the first direction in which the solenoid urges the spool; and a feedback section in which the secondary pressure acts to urge the spool in the second direction, wherein the spool has: a first land section for connecting or blocking the secondary pressure port and the drain port; a second land section provided at a distance from the first land section, for connecting or blocking the input port and the secondary pressure port; a third land section provided at a distance from the second land section, for connecting or blocking the input port and the output port; and a fourth land section provided at a distance from the third land section, for connecting or blocking the output port and the drain port.

6. A valve device as claimed in claim 1, further comprising: a secondary pressure port from which the secondary pressure is output; a spring which urges the spool in a second direction which is opposite to the first direction in which the solenoid urges the spool; and a feedback section in which the secondary pressure acts to urge the spool in the first direction, wherein the spool has: a first land section for connecting or blocking the secondary pressure port and the drain port; a second land section provided at a distance from the first land section, for connecting or blocking the input port and the secondary pressure port; and a third land section provided at a distance from the second land section, for selectively connecting either the input port or the drain port to the output port.

7. The valve device according to claim 1, further comprising a communication passage formed to pass through said spool and for directing the working fluid discharged from said output port to said drain port.

8. A flow control device for controlling the flow rate of a pump, comprising: a valve device as described in claim 1; a flow control mechanism for controlling the flow rate of the pump in accordance with the secondary pressure; and a horsepower control mechanism for performing horsepower control on the pump when the solenoid fails, wherein the horsepower control mechanism has a lock pin for enabling or disabling control of the horsepower control mechanism, and when the valve device is normal, the secondary pressure or the primary pressure acts on the lock pin, disabling control of the horsepower control mechanism, and when the solenoid fails, the secondary pressure or the primary pressure no longer acts on the lock pin, thereby enabling control of the horsepower control mechanism.

9. A flow control device as described in claim 8, further comprising a second switching valve that is switched in response to the pressure output from the output port, wherein the second switching valve supplies the primary pressure to the lock pin of the horsepower control mechanism when the valve device is normal, and is switched to discharge the pressure acting on the lock pin of the horsepower control mechanism when the solenoid fails.

10. A flow control device for controlling the flow rate of a pump, comprising: a valve device as described in claim 1; a flow control mechanism for controlling the flow rate of the pump in accordance with the secondary pressure; and a horsepower control mechanism for controlling the horsepower of the pump when the solenoid fails, wherein the horsepower control mechanism has a lock pin for enabling or disabling control of the horsepower control mechanism, and when the valve device is normal, the secondary pressure or the primary pressure does not act on the lock pin, thereby disabling control of the horsepower control mechanism, and when the solenoid fails, the primary pressure acts on the lock pin, thereby enabling control of the horsepower control mechanism.

11. A flow control device according to claim 8 or 10, further comprising a high pressure selection valve which selects the higher of the secondary pressure and the pressure output from the output port and outputs the selected pressure to the flow control mechanism.

12. A flow control device as described in claim 8 or 10, further comprising a second switching valve that is switched according to the pressure output from the output port, wherein the second switching valve supplies the secondary pressure to the flow control mechanism when the valve device is normal, and supplies the primary pressure to the flow control mechanism when the solenoid fails.

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