Control valve device and work machine

Abstract

To accurately detect a flow rate of pressure oil flowing through a center bypass oil passage irrespective of pressure loss that is diverse for each individual.SOLUTION: A control valve device 20 includes: a pump port 21A connected to a hydraulic pump 14; a tank port 21B connected to a tank 15; a valve casing 21 provided with actuator ports 21C, 21D connected to a hydraulic actuator; and a spool valve 29 provided in the valve casing 21 to switch a direction of pressure oil discharged from the hydraulic pump 14 to the pump port 21A between the tank port 21B and the actuator ports 21C, 21D, where a turbine 30 is installed in the valve casing 21, the turbine rotating with the pressure oil flowing through a center bypass oil passage 24 that connects between the pump port 21A and the tank port 21B and detecting a flow rate of the pressure oil flowing through the center bypass oil passage 24.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a control valve device and a work machine that controls the supply and discharge of pressure oil to, for example, a hydraulic actuator. [Background technology]

[0002] Work machines such as wheel loaders and hydraulic excavators have a self-propelled vehicle body and a work implement attached to the vehicle body, and perform work such as earth removal and excavation using the work implement. The work implement is driven by a plurality of hydraulic actuators, and the vehicle body of the work machine is equipped with a hydraulic pump that pressurizes hydraulic oil and supplies it to the hydraulic actuators, and a control valve device that supplies and discharges pressure oil discharged from the hydraulic pump to the plurality of hydraulic actuators. Generally, work machines are equipped with a variable displacement hydraulic pump having a variable displacement unit, and the amount of pressure oil discharged is controlled by driving the variable displacement unit using a displacement control mechanism.

[0003] The control valve device is provided with a pump port connected to the hydraulic pump, a tank port connected to a tank, an actuator port connected to a hydraulic actuator, and a spool valve that switches the direction of pressure oil discharged from the hydraulic pump to the pump port to either the tank port or the actuator port. The control valve device also has a center bypass oil passage that connects the pump port and the tank port via the spool valve, and when the hydraulic actuator is not being operated, the pressure oil discharged from the hydraulic pump returns to the tank through the center bypass oil passage.

[0004] In the prior art, a control valve device equipped with a negative control system in which a relief valve and a throttle are provided downstream of the center bypass oil passage has been proposed. This control valve device with a negative control system directs the differential pressure generated across the relief valve and the throttle to a displacement control mechanism to drive the displacement variable part of the hydraulic pump. This can limit the flow rate of the hydraulic pump when the hydraulic actuator is not being operated, contributing to energy savings (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5870205 Specification [Patent Document 2] Patent No. 3051059 specification Summary of the Invention [Problem to be solved by the invention]

[0006] However, the control valve devices described in Patent Documents 1 and 2 are configured to intentionally create a pressure difference across the relief valve and the throttle, and to drive the variable displacement mechanism based on this pressure difference. Therefore, the structure that creates a pressure difference between the relief valve and the throttle itself causes pressure loss in the center bypass oil passage, resulting in the problem of energy loss in the hydraulic pump.

[0007] Furthermore, because oil passages such as the center bypass oil passage provided in the control valve device are generally formed integrally with the casing by casting, the pressure loss in the center bypass oil passage varies for each individual valve casing. As a result, the pressure difference between the relief valve and the throttle varies depending on the pressure loss in each individual center bypass oil passage. Therefore, when the capacity variable mechanism controls the capacity variable part of the hydraulic pump based on the pressure difference between the relief valve and the throttle, there is a problem in that the flow rate of the hydraulic pump also varies for each individual hydraulic pump.

[0008] The present invention has been made in consideration of the above-mentioned problems with the conventional technology, and an object of the present invention is to provide a control valve device and a working machine that can accurately detect the flow rate of pressurized oil flowing through a center bypass oil passage regardless of pressure loss that varies from one device to another, and that can suppress energy loss in the hydraulic pump when detecting the flow rate of pressurized oil. [Means for solving the problem]

[0009] The present invention provides a control valve device comprising: a valve casing provided with a pump port connected to a hydraulic pump, a tank port connected to a tank, and an actuator port connected to a hydraulic actuator; and a spool valve provided in the valve casing for switching the direction of pressurized oil discharged from the hydraulic pump to the pump port to the tank port or the actuator port, wherein the valve casing is provided with a turbine that detects the flow rate of pressurized oil flowing through a center bypass oil passage connecting the pump port and the tank port by being rotated by the pressurized oil flowing through the center bypass oil passage.

[0010] The present invention relates to a working machine comprising a self-propelled vehicle body, a working device rotatably mounted on the vehicle body, a hydraulic actuator that drives the working device, a hydraulic pump that supplies operating pressure oil to the hydraulic actuator, and a control valve device that controls the direction of pressure oil discharged from the hydraulic pump, wherein the hydraulic pump is equipped with a variable capacity section that varies the discharge capacity, and a capacity control mechanism that controls the operation of the variable capacity section, wherein the control valve device comprises a valve casing that is provided with a pump port connected to the hydraulic pump, a tank port connected to a tank, and an actuator port connected to the hydraulic actuator, and a spool valve that is provided in the valve casing and switches the direction of pressure oil discharged from the hydraulic pump to the pump port to either the tank port or the actuator port, and wherein the valve casing is provided with a turbine that is rotated by pressure oil flowing in a center bypass oil passage connecting the pump port and the tank port, thereby detecting the flow rate of pressure oil flowing in the center bypass oil passage, and the capacity control mechanism controls the operation of the variable capacity section in accordance with the rotation of the turbine. [Effects of the Invention]

[0011] According to the present invention, the flow rate of pressure oil flowing through the center bypass oil passage can be accurately detected based on the turbine rotation speed, regardless of the pressure loss that differs from one individual to another. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a left side view showing a wheel loader equipped with a control valve device according to an embodiment of the present invention. [Figure 2] 1 is a configuration diagram of a hydraulic control device according to a first embodiment, including a control valve device and a hydraulic circuit. [Figure 3] FIG. 2 is a plan view showing the control valve device alone. [Figure 4] 4 is a right side view of the control valve device as seen from the direction of arrows IV-IV in FIG. 3. [Figure 5] 4 is a cross-sectional view of the control valve device as seen from the direction of arrow VV in FIG. 3. [Figure 6] FIG. 6 is a cross-sectional view showing the turbine in FIG. 5 alone. [Figure 7] FIG. 2 is a perspective view showing the turbine alone. [Figure 8] FIG. 4 is a configuration diagram of a hydraulic control device according to a second embodiment including a control valve device and a hydraulic circuit. DETAILED DESCRIPTION OF THE INVENTION

[0013] A control valve device according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings, taking as an example a case where the control valve device is mounted on a wheel loader. Note that in the embodiment, the traveling direction of the wheel loader is defined as the front-rear direction, and the direction perpendicular to the traveling direction is defined as the left-right direction.

[0014] Figures 1 to 7 show a first embodiment of the present invention. In Figure 1, the wheel loader 1 is configured to include a rear vehicle body 2, a front vehicle body 3, rear wheels 4, front wheels 5, and a working device 6 provided in front of the front vehicle body 3. The front vehicle body 3 is connected to the front side of the rear vehicle body 2 so as to be able to swing in the left-right direction. The rear wheels 4 are provided on both left-right sides of the rear vehicle body 2, and the front wheels 5 are provided on both left-right sides of the front vehicle body 3.

[0015] The working device 6 is configured to include an arm 6A rotatably attached to the front vehicle body 3, a loader bucket 6B rotatably attached to the tip side of the arm 6A, a lift cylinder (not shown) that rotates the arm 6A in the vertical direction, and a bucket cylinder 6C that rotates the loader bucket 6B in the vertical direction. The working device 6 uses the loader bucket 6B to perform work such as removing earth and sand.

[0016] The rear body 2 is equipped with an engine 7 serving as a drive source, a torque converter 8, a transmission 9, a hydraulic pump 14 (described later), and the like. The transmission 9 is connected to a rear axle unit 10 via a propeller shaft 9A extending in the longitudinal direction, and is connected to a front axle unit 11 via a propeller shaft 9B. A cab 12 in which an operator sits is provided above the rear body 2. The front body 3 is also equipped with a control valve unit 20 (described later), and the like.

[0017] The rear axle unit 10 is provided below the rear vehicle body 2. The rear axle unit 10 extends in the left-right direction, and rear wheels 4 are attached to both left and right ends of the rear axle unit 10. The rear axle unit 10 is connected to a propeller shaft 9A to rotate the left and right rear wheels 4.

[0018] The front axle unit 11 is provided below the front vehicle body 3. Like the rear axle unit 10, the front axle unit 11 is formed to extend in the left-right direction, and front wheels 5 are attached to both left and right ends of the front axle unit 11. The front axle unit 11 is connected to a propeller shaft 9B to rotate the left and right front wheels 5.

[0019] Next, the hydraulic control device 13 according to this embodiment will be described with reference to Fig. 2. The hydraulic control device 13 is configured to include a hydraulic pump 14, a servo piston mechanism 17, a solenoid valve 18, a control valve device 20, a tachometer 38, a controller 39, a generator 40, a storage battery 41, etc. The hydraulic control device 13 supplies pressure oil discharged from the hydraulic pump 14 to hydraulic actuators such as the bucket cylinder 6C via the control valve device 20. The hydraulic control device 13 also controls the capacity of the hydraulic pump 14 using the servo piston mechanism 17.

[0020] The hydraulic pump 14, together with the tank 15, constitutes the hydraulic power source of the wheel loader 1. The hydraulic pump 14 is configured as, for example, a variable displacement hydraulic pump, and is driven by the engine 7 to discharge hydraulic oil stored in the tank 15 as pressurized oil. The hydraulic pump 14 has a variable displacement unit 14A formed, for example, of a swash plate or the like whose tilt angle changes, and this variable displacement unit 14A is driven by a servo piston mechanism 17 to change the discharge capacity of the pressurized oil.

[0021] The pilot pump 16 constitutes a pilot hydraulic pressure source together with the tank 15. The pilot pump 16 is driven together with the hydraulic pump 14 by the engine 7. A servo piston mechanism 17 is connected to the discharge side of the pilot pump 16 via a control pressure line 19, which will be described later.

[0022] Servo piston mechanism 17, which serves as a displacement control mechanism, is connected to variable displacement unit 14A of hydraulic pump 14. Pilot pressure from pilot pump 16 is supplied to and discharged from servo piston mechanism 17 via solenoid valve 18, which together with servo piston mechanism 17 constitutes a displacement control mechanism, thereby driving variable displacement unit 14A and controlling the discharge capacity of hydraulic pump 14. Solenoid valve 18 is configured, for example, by a 3-port 2-position directional control valve, and is provided in a control pressure line 19 that connects pilot pump 16 and servo piston mechanism 17.

[0023] The solenoid valve 18 is normally held in a closed position (a) by a spring 18A, and is switched to an open position (b) when a control signal is supplied from a controller 39 (described later) to an electromagnetic pilot unit 18B. When no signal is supplied to the electromagnetic pilot unit 18B, the solenoid valve 18 holds the closed position (a), and hydraulic oil in the servo piston mechanism 17 is discharged to the tank 15 through a control pressure line 19. As a result, the servo piston mechanism 17 holds, for example, the capacity variable unit 14A of the hydraulic pump 14 on the large tilt side, thereby increasing the discharge capacity of the hydraulic pump 14. On the other hand, when a control signal is supplied to the electromagnetic pilot unit 18B, the solenoid valve 18 is switched to an open position (b), and pilot pressure discharged from the pilot pump 16 is supplied to the servo piston mechanism 17 through the control pressure line 19. As a result, the servo piston mechanism 17 changes the capacity variable unit 14A of the hydraulic pump 14 from the large tilt side to the small tilt side, thereby controlling the discharge capacity of the hydraulic pump 14.

[0024] The control valve device 20 is disposed in the front body 3 of the wheel loader 1. The control valve device 20 is provided between the hydraulic pump 14 and a plurality of hydraulic actuators, such as the bucket cylinder 6C and lift cylinder (not shown), and supplies pressure oil discharged from the hydraulic pump 14 to the hydraulic actuator to be operated. As shown in Figures 2 to 4, the control valve device 20 is configured to include a valve casing 21, a spool valve 29, and a turbine 30, which will be described later.

[0025] The valve casing 21 serves as the base of the control valve device 20 and is formed into a block shape by casting. The valve casing 21 is formed with a pump port 21A, a tank port 21B, actuator ports 21C and 21D, and a plurality of oil passages connected to these ports 21A, 21B, 21C, and 21D. The pump port 21A is connected to the discharge side of the hydraulic pump 14 via a pump line 22, and the tank port 21B is connected to the tank 15 via a tank line 23. The actuator port 21C is connected to, for example, a bottom-side oil chamber of the bucket cylinder 6C via a hydraulic line, and the actuator port 21D is connected to a rod-side oil chamber of the bucket cylinder 6C via a hydraulic line.

[0026] A center bypass oil passage 24 is provided within the valve casing 21. The center bypass oil passage 24 connects the pump port 21A and the tank port 21B via a spool valve 29, forming a pump-tank line. A supply oil passage 25 and actuator oil passages 26 and 27 are also provided within the valve casing 21. The supply oil passage 25 branches off from the center bypass oil passage 24 and connects either the actuator oil passage 26 or the actuator oil passage 27 to the pump port 21A depending on the operation of the spool valve 29. The actuator oil passage 26 is connected to the actuator port 21C, and the actuator oil passage 27 is connected to the actuator port 21D. A return oil passage 28 is provided within the valve casing 21 and connected to the tank port 21B via the center bypass oil passage 24. The return oil passage 28 connects either the actuator oil passage 26 or the actuator oil passage 27 to the tank port 21B depending on the operation of the spool valve 29.

[0027] The spool valve 29 is provided in the valve casing 21 and controls the direction of pressure oil supplied from the hydraulic pump 14 to the bucket cylinder 6C. The spool valve 29 is configured, for example, as a 6-port 3-position directional control valve and is switchable between a neutral position (c) and switching positions (d) and (e). That is, the spool valve 29 has a spring 29A that maintains the neutral position (c), and is switched to the switching position (d) or (e) when pilot pressure is supplied from the pilot pump 16.

[0028] When the spool valve 29 is held in the neutral position (c), the pressure oil discharged from the hydraulic pump 14 is led from the pump port 21A to the tank port 21B through the center bypass oil passage 24. The pressure oil led to the tank port 21B is discharged into the tank 15 via the tank pipe line 23.

[0029] When the spool valve 29 is switched to the switching position (d), the pressure oil discharged from the hydraulic pump 14 is discharged from the pump port 21A through the supply oil passage 25 and the actuator oil passage 27 to the actuator port 21D. The pressure oil discharged to the actuator port 21D is supplied to the rod-side oil chamber of the bucket cylinder 6C through the hydraulic lines. At this time, the hydraulic oil in the bottom-side oil chamber of the bucket cylinder 6C is discharged from the actuator port 21C through the actuator oil passage 26, the return oil passage 28, and the center bypass oil passage 24 to the tank port 21B, and is discharged to the tank 15 via the tank line 23.

[0030] When spool valve 29 is switched to the switching position (e), pressure oil discharged from hydraulic pump 14 is discharged from pump port 21A through supply oil passage 25 and actuator oil passage 26 to actuator port 21C. The pressure oil discharged to actuator port 21C is supplied to the bottom-side oil chamber of bucket cylinder 6C through hydraulic lines. At this time, the hydraulic oil in the rod-side oil chamber of bucket cylinder 6C is discharged from actuator port 21D through actuator oil passage 27, return oil passage 28, and center bypass oil passage 24 to tank port 21B, and is discharged to tank 15 via tank line 23.

[0031] A turbine mounting hole 21E communicating with the center bypass oil passage 24 is formed in the valve casing 21 (see FIG. 5). The turbine mounting hole 21E is located downstream of the spool valve 29 in the flow direction of the pressurized oil flowing through the center bypass oil passage 24, and a support case 31 of a turbine 30 (described later) is mounted in the turbine mounting hole 21E. A female thread portion 21G is formed on the inner circumferential surface of the turbine mounting hole 21E on the side of an opening end 21F that opens to the outside of the valve casing 21.

[0032] 2 only shows a spool valve 29 that controls the supply and discharge of pressure oil to and from the bucket cylinder 6C. However, the control valve device 20 is provided with a plurality of spool valves in parallel that correspond not only to the bucket cylinder 6C but also to other hydraulic actuators such as a lift cylinder (not shown) mounted on the wheel loader 1.

[0033] Next, the turbine 30 used in this embodiment will be described with reference to FIGS.

[0034] The turbine 30 is attached to the valve casing 21. The turbine 30 is rotated by the pressurized oil flowing through the center bypass oil passage 24, and detects the flow rate of the pressurized oil flowing through the center bypass oil passage 24. The turbine 30 includes a support case 31 that serves as a base, a turbine body 34 that is rotatably arranged within the support case 31, and a turbine shaft 35 that has one end fixed to the turbine body 34 within the support case 31 and the other end protruding outside the support case 31.

[0035] The support case 31 of the turbine 30 is detachably attached to the turbine mounting hole 21E of the valve casing 21 with the turbine body 34 supported therein. The support case 31 is formed in a stepped cylindrical shape and has a large-diameter hole 31H (described later) at one axial end 31A and a small-diameter hole 31J at the other axial end 31B. A polygonal tool engagement portion 31C, a large-diameter disc-shaped flange 31D, and a male threaded portion 31E are formed on the outer circumferential surface of the support case 31 at the other end 31B, adjacent to each other in the axial direction. By threading the male threaded portion 31E of the support case 31 into the female threaded portion 21G of the turbine mounting hole 21E, the flange 31D abuts against the open end 21F of the turbine mounting hole 21E. In this state, the support case 31 is fixed in the turbine mounting hole 21E of the valve casing 21, and the outer peripheral surface of one end 31A of the support case 31 fits into the inner peripheral surface of the turbine mounting hole 21E.

[0036] An annular one-end seal groove 31F is formed in the outer peripheral surface of one end 31A of support case 31, and an annular other-end seal groove 31G is formed in the outer peripheral surface of the boundary between flange 31D and male threaded portion 31E of support case 31. A one-end O-ring 32 is attached to one-end seal groove 31F, and one-end O-ring 32 provides a seal between the outer peripheral surface of one end 31A of support case 31 and the inner peripheral surface of turbine mounting hole 21E. A other-end O-ring 33 is attached to other-end seal groove 31G, and other-end O-ring 33 provides a seal between flange 31D of support case 31 and open end 21F of turbine mounting hole 21E.

[0037] A large-diameter hole 31H with a bottom and a small-diameter hole 31J having a diameter smaller than that of the large-diameter hole 31H are formed on the inner periphery of the support case 31. The large-diameter hole 31H and the small-diameter hole 31J are formed concentrically. The large-diameter hole 31H has an open end on one end 31A of the support case 31, which serves as an inlet 31L through which pressure oil flowing through the center bypass oil passage 24 flows. The small-diameter hole 31J opens to the other end 31B of the support case 31 and to a bottom 31K of the large-diameter hole 31H. An outlet 31M is formed in the axially intermediate portion of the support case 31, penetrating from the outer peripheral surface of the support case 31 to the large-diameter hole 31H. The outlet 31M opens at a position adjacent to the bottom 31K of the large-diameter hole 31H and allows pressure oil that has flowed into the large-diameter hole 31H of the support case 31 from the inlet 31L to flow out of the support case 31.

[0038] As shown in Fig. 5, when the support case 31 is attached to the turbine mounting hole 21E of the valve casing 21, the inlet 31L and outlet 31M of the large diameter hole 31H provided in the support case 31 communicate with the center bypass oil passage 24. When the spool valve 29 is in the neutral position (c), the pressurized oil discharged from the hydraulic pump 14 to the center bypass oil passage 24 flows from the inlet 31L to the outlet 31M of the large diameter hole 31H, as shown by arrow F in Fig. 5.

[0039] The turbine body 34 is rotatably disposed within the large diameter hole 31H of the support case 31. The turbine body 34 is formed using a radial fan such as a plate fan having a plurality of blades 34A. The blades 34A of the turbine body 34 are radially opposed to the outlet 31M of the support case 31, and an axial end face 34B of the turbine body 34 is axially opposed to the bottom 31K of the large diameter hole 31H.

[0040] A cylindrical turbine shaft 35 is rotatably supported via a bearing 36 within the small-diameter hole 31J of the support case 31. One end 35A of the turbine shaft 35 is fixed to an end face 34B of the turbine body 34, and the turbine body 34 and the turbine shaft 35 rotate together. Therefore, pressurized oil flowing through the center bypass oil passage 24 of the valve casing 21 flows from the inlet 31L to the outlet 31M of the support case 31 as shown by arrow F in Figure 5, causing the turbine body 34 and the turbine shaft 35 to rotate together. The turbine 30 detects the flow rate of pressurized oil flowing through the center bypass oil passage 24 in accordance with its rotational speed.

[0041] The other end 35B of the turbine shaft 35 protrudes to the outside from the other end 31B of the support case 31. An oil seal 37 is provided at the opening end of a small diameter hole 31J that opens to the other end 31B of the support case 31. The oil seal 37 prevents oil from leaking to the outside through the small diameter hole 31J of the support case 31.

[0042] The tachometer 38 is arranged around the control valve device 20. The tachometer 38 detects the rotation speed of the turbine shaft 35 protruding from the other end 31B of the support case 31 to the outside, and outputs a signal (rotation speed signal) corresponding to the rotation speed of the turbine shaft 35 to the controller 39.

[0043] A tachometer 38 is connected to the input side of the controller 39, and an electromagnetic pilot unit 18B of the solenoid valve 18 is connected to the output side of the controller 39. The controller 39 outputs a control signal to the electromagnetic pilot unit 18B in response to a signal input from the tachometer 38. The solenoid valve 18 switches from a closed valve position (a) to an open valve position (b) in response to the current of the control signal input to the electromagnetic pilot unit 18B. As a result, the pilot pressure discharged from the pilot pump 16 is supplied to the servo piston mechanism 17 through the control pressure line 19, and the servo piston mechanism 17 changes the displacement variable unit 14A of the hydraulic pump 14 from the large displacement side to the small displacement side, thereby controlling the discharge displacement of the hydraulic pump 14.

[0044] The generator 40 and the storage battery 41 are arranged around the control valve device 20. The generator 40 and the storage battery 41 are electrically connected. The rotor (not shown) of the generator 40 is arranged coaxially with the turbine shaft 35 and is rotated by the turbine shaft 35. The generator 40 generates electric power through the rotation of the turbine shaft 35, and the generated electric power is stored in the storage battery 41.

[0045] The control valve device 20 according to this embodiment has the turbine 30 as described above, and the operation of the hydraulic control device 13 including the control valve device 20 will be described below.

[0046] First, the operator of the wheel loader 1 gets into the cab 12 and starts the engine 7, and operates an operating lever or the like (not shown) to operate the transmission 9. The rotation of the output shaft of the transmission 9 is transmitted from the propeller shaft 9A to the rear axle unit 10, and from the propeller shaft 9B to the front axle unit 11. This drives the left and right rear wheels 4 and the left and right front wheels 5 to rotate, allowing the wheel loader 1 to travel.

[0047] Meanwhile, the started engine 7 drives the hydraulic pump 14 and the pilot pump 16. As a result, the hydraulic pump 14 discharges pressurized oil toward the pump line 22 and the center bypass oil line 24. In this state, for example, to rotate the loader bucket 6B, an operating device (not shown) disposed inside the cab 12 is operated to switch the spool valve 29 of the control valve device 20 from the neutral position (c) to the switching position (d) or (e).

[0048] When the spool valve 29 is switched to the switching position (d), the pressure oil discharged from the hydraulic pump 14 is guided from the pump port 21A through the supply oil passage 25 and the actuator oil passage 27 to the actuator port 21D. This causes the pressure oil to be supplied to the rod-side oil chamber of the bucket cylinder 6C. At this time, the hydraulic oil in the bottom-side oil chamber of the bucket cylinder 6C is discharged from the actuator port 21C through the actuator oil passage 26, the return oil passage 28, the center bypass oil passage 24, and the tank pipe line 23 to the tank 15. This causes the bucket cylinder 6C to contract, and the loader bucket 6B to rotate downward.

[0049] When the spool valve 29 is switched to the switching position (e), the pressure oil discharged from the hydraulic pump 14 is guided from the pump port 21A through the supply oil passage 25 and the actuator oil passage 26 to the actuator port 21C. This causes the pressure oil to be supplied to the bottom-side oil chamber of the bucket cylinder 6C. At this time, the hydraulic oil in the rod-side oil chamber of the bucket cylinder 6C is discharged from the actuator port 21D through the actuator oil passage 27, the return oil passage 28, the center bypass oil passage 24, and the tank pipe line 23 to the tank 15. This causes the bucket cylinder 6C to extend, and the loader bucket 6B to rotate upward.

[0050] On the other hand, while hydraulic actuators such as the bucket cylinder 6C are not operated and the spool valve 29 is held in the neutral position (c), the hydraulic pump 14 and the tank 15 are connected via the center bypass oil passage 24. Therefore, the pressure oil discharged from the hydraulic pump 14 to the center bypass oil passage 24 flows back to the tank 15 from the center bypass oil passage 24 through the tank pipe line 23. At this time, as shown by arrow F in FIG. 5, the pressure oil flowing through the center bypass oil passage 24 flows from the inlet 31L to the outlet 31M of the support case 31 attached to the turbine mounting hole 21E of the valve casing 21. As a result, the turbine body 34 and the turbine shaft 35 rotate together at a rotation speed corresponding to the flow rate of the pressure oil flowing through the center bypass oil passage 24.

[0051] The tachometer 38 detects the rotation of the turbine shaft 35 protruding outside the valve casing 21, and outputs a rotation speed signal corresponding to the rotation speed of the turbine shaft 35 to the controller 39. The controller 39 outputs a control signal to the electromagnetic pilot unit 18B in accordance with the rotation speed signal input from the tachometer 38. The solenoid valve 18 switches from a closed valve position (a) to an open valve position (b) in accordance with the current of the control signal input to the electromagnetic pilot unit 18B. As a result, the pilot pressure discharged from the pilot pump 16 is supplied to the servo piston mechanism 17 through the control pressure line 19, and the servo piston mechanism 17 changes the displacement variable unit 14A of the hydraulic pump 14 between large displacement and small displacement, thereby controlling the discharge displacement of the hydraulic pump 14.

[0052] When the rotation speed of the turbine shaft 35 is high, the servo piston mechanism 17 changes the capacity variable unit 14A of the hydraulic pump 14 to the small flow rate side so as to reduce the flow rate of pressurized oil discharged from the hydraulic pump 14. When the rotation speed of the turbine shaft 35 decreases, the servo piston mechanism 17 changes the capacity variable unit 14A of the hydraulic pump 14 to the large flow rate side so as to increase the flow rate of pressurized oil discharged from the hydraulic pump 14. As a result, when the spool valve 29 is held in the neutral position (c), the flow rate of pressurized oil that is wasted and discharged from the hydraulic pump 14 to the tank 15 via the center bypass oil passage 24 can be reduced, thereby achieving energy savings.

[0053] According to this embodiment, the flow rate of the pressurized oil flowing through the center bypass oil passage 24 can be accurately detected based on the rotation speed of the turbine 30, regardless of the influence of variations in pressure loss between individual parts of the center bypass oil passage 24. As a result, the servo piston mechanism 17 can control the capacity variable unit 14A of the hydraulic pump 14 based on the flow rate of the pressurized oil detected by the turbine 30. Therefore, accurate flow rate control of the hydraulic pump 14 can be achieved, regardless of variations in pressure loss between individual parts of the valve casing 21 in the center bypass oil passage 24.

[0054] Furthermore, in this embodiment, the flow rate of pressurized oil can be detected based on the rotation speed of the turbine shaft 35, so compared to the conventional configuration in which the differential pressure across a relief valve and a throttle is detected when controlling the displacement variable section of the hydraulic pump, it is possible to eliminate the need for a relief valve and a throttle, which cause pressure loss in the center bypass oil passage. As a result, in this embodiment, it is possible to suppress energy loss in the hydraulic pump 14 when detecting the flow rate of pressurized oil flowing through the center bypass oil passage 24.

[0055] Furthermore, in this embodiment, a generator 40 is provided that generates electric power in response to the rotation of the turbine shaft 35, and the electric power generated by the generator 40 is stored in a storage battery 41. In this way, by recovering the rotation of the turbine 30 as electric energy and storing this electric energy in the storage battery 41, it is possible to reduce unnecessary energy consumption.

[0056] Thus, in the embodiment, the control valve device 20 includes a valve casing 21 provided with a pump port 21A connected to the hydraulic pump 14, a tank port 21B connected to the tank 15, and actuator ports 21C and 21D connected to hydraulic actuators, and a spool valve 29 provided in the valve casing 21 for switching the direction of pressure oil discharged from the hydraulic pump 14 to the pump port 21A to the tank port 21B or the actuator ports 21C and 21D. Within the valve casing 21, there is provided a turbine 30 that detects the flow rate of pressure oil flowing through the center bypass oil passage 24 by being rotated by pressure oil flowing through the center bypass oil passage 24 connecting the pump port 21A and the tank port 21B.

[0057] According to this configuration, the flow rate of the pressurized oil flowing through the center bypass oil passage 24 can be accurately detected based on the rotation speed of the turbine 30, regardless of the influence of variations in pressure loss between individual parts of the center bypass oil passage 24. As a result, the servo piston mechanism 17 can control the capacity variable unit 14A of the hydraulic pump 14 based on the flow rate of the pressurized oil detected by the turbine 30. Therefore, accurate flow rate control of the hydraulic pump 14 can be achieved based on the rotation speed of the turbine 30, regardless of variations in pressure loss between individual parts of the center bypass oil passage 24.

[0058] In this embodiment, the turbine 30 is equipped with a generator 40 that generates electric power in response to the rotation of the turbine 30. With this configuration, the rotation of the turbine 30 can be recovered as electric energy, thereby reducing unnecessary energy consumption.

[0059] In this embodiment, the generator 40 is connected to a storage battery 41 that stores the electric power generated by the generator 40. With this configuration, the rotation of the turbine 30 can be recovered as electric energy and stored in the storage battery 41.

[0060] In this embodiment, the turbine 30 is detachably attached to the valve casing 21. According to this configuration, the turbine 30, which is a separate member from the valve casing 21, can be easily incorporated into the valve casing 21 that is formed by casting, for example.

[0061] In this embodiment, the turbine 30 includes a cylindrical support case 31 that is provided with an inlet 31L and an outlet 31M that communicate with the center bypass oil passage 24 and that has an external thread 31E formed on its outer periphery and that is threaded into the valve casing 21, a turbine body 34 that is rotatably arranged within the support case 31 and that is rotated by pressurized oil that flows from the inlet 31L to the outlet 31M, and a turbine shaft 35 that has one end 35A fixed to the turbine body 34 within the support case 31 and the other end 35B protruding outside the support case 31. With this configuration, the turbine 30 can be easily assembled within the valve casing 21 by threading the external thread 31E of the support case 31 into the valve casing 21 with the turbine body 34 to which the turbine shaft 35 is fixed placed within the support case 31.

[0062] In the embodiment, the working machine is configured to include a self-propelled rear body 2 and a front body 3, a working device 6 rotatably provided on the front body 3, a hydraulic actuator that drives the working device 6, a hydraulic pump 14 that supplies pressure oil for operation to the hydraulic actuator, and a control valve device 20 that controls the direction of the pressure oil discharged from the hydraulic pump 14, and the hydraulic pump 14 is equipped with a capacity variable unit 14A that changes the discharge capacity and a capacity control mechanism that controls the operation of the capacity variable unit 14A, and the control valve device 20 is equipped with a pump port 21A connected to the hydraulic pump 14, a tank port 21B connected to a tank 15, and a control valve device 20 that controls the direction of the pressure oil discharged from the hydraulic actuator. The hydraulic control mechanism includes a valve casing 21 provided with actuator ports 21C, 21D to be connected to the variable displacement unit 14A, and a spool valve 29 provided in the valve casing 21 for switching the direction of pressurized oil discharged from the hydraulic pump 14 to the pump port 21A to the tank port 21B or the actuator ports 21C, 21D. A turbine 30 is provided within the valve casing 21 and rotates due to the pressurized oil flowing through a center bypass oil passage 24 connecting the pump port 21A and the tank port 21B, thereby detecting the flow rate of the pressurized oil flowing through the center bypass oil passage 24. The capacity control mechanism controls the operation of the capacity variable unit 14A in accordance with the rotation of the turbine 30.

[0063] According to this configuration, when the hydraulic actuator is not operated and the pressurized oil discharged from the hydraulic pump 14 flows through the center bypass oil passage 24, the flow rate of this pressurized oil can be accurately detected based on the rotation speed of the turbine 30. As a result, the capacity control mechanism controls the capacity variable unit 14A of the hydraulic pump 14 based on the flow rate of the pressurized oil detected by the turbine 30, and can accurately control the flow rate of the hydraulic pump 14.

[0064] Next, FIG. 8 shows a hydraulic control device 42 according to a second embodiment, which is provided with the control valve device 20.

[0065] The hydraulic control device 42 according to the present embodiment is configured to include a hydraulic pump 14, a servo piston mechanism 17, a control valve device 20, a generator 40, a storage battery 41, a controller 43, etc., similar to the hydraulic control device 13 according to the first embodiment. However, the hydraulic control device 42 differs from the hydraulic control device 13 according to the first embodiment in that it does not include a tachometer 38. In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0066] Electric power generated by the generator 40 in accordance with the rotation speed of the turbine shaft 35 is input to the input side of a controller 43 of the hydraulic control device 42 as a detection signal indicating the flow rate of pressurized oil flowing through the center bypass oil passage 24. The controller 43 outputs a control signal in accordance with the electric power corresponding to the rotation speed of the turbine shaft 35 to an electromagnetic pilot unit 18B of the solenoid valve 18. The solenoid valve 18 switches from a closed valve position (a) to an open valve position (b) in accordance with the current of the control signal input to the electromagnetic pilot unit 18B. As a result, the pilot pressure discharged from the pilot pump 16 is supplied to the servo piston mechanism 17, and the servo piston mechanism 17 changes the displacement variable unit 14A of the hydraulic pump 14 between large displacement and small displacement, thereby controlling the discharge displacement of the hydraulic pump 14.

[0067] The hydraulic control device 42 according to the present embodiment has the configuration as described above, and in the present embodiment, as in the first embodiment, the flow rate of pressurized oil flowing through the center bypass oil passage 24 can be accurately detected based on the rotation speed of the turbine 30. The generator 40 supplies electric power corresponding to the rotation speed of the turbine 30 to the storage battery 41 for storage therein, and outputs the generated electric power to the controller 43. As a result, the controller 43 supplies a control signal corresponding to the flow rate of pressurized oil flowing through the center bypass oil passage 24 to the solenoid valve 18, and controls the capacity variable unit 14A of the hydraulic pump 14 by the servo piston mechanism 17. As a result, in the present embodiment as well, accurate flow rate control of the hydraulic pump 14 can be achieved regardless of variations in pressure loss in the center bypass oil passage 24 that occur for each individual valve casing 21.

[0068] Moreover, in this embodiment, the electric power generated by the generator 40 due to the rotation of the turbine 30 is input to the controller 43 as a detection signal indicating the flow rate of pressurized oil flowing through the center bypass oil passage 24. This eliminates the need for a tachometer for detecting the rotation speed of the turbine 30, thereby simplifying the overall configuration of the hydraulic control device 42 and enabling it to be made smaller.

[0069] In the embodiment, a wheel loader 1 is exemplified as a work machine equipped with the control valve device 20. However, the present invention is not limited to this, and the control valve device 20 may be mounted on other work machines such as a hydraulic excavator. [Explanation of symbols]

[0070] 2 Rear body 3 Front body 6. Work equipment 14 Hydraulic pump 14A variable capacity part 15 Tank 17 Servo piston mechanism (capacity control mechanism) 18 Solenoid valve (capacity control mechanism) 20 Control valve device 21 Valve casing 21A Pump Port 21B Tank Port 21C, 21D Actuator Port 24 Center bypass oil passage 29 Spool valve 30 Turbine 31 Support Case 31E male thread 31L inlet 31M Outlet 34 Turbine body 35 Turbine shaft 35A one end 35B other end 38 Tachometer 39,43 Controller 40 Generator 41 Storage battery

Claims

1. a valve casing provided with a pump port connected to a hydraulic pump, a tank port connected to a tank, and an actuator port connected to a hydraulic actuator; a spool valve provided in the valve casing and configured to switch the direction of pressure oil discharged from the hydraulic pump to the pump port to the tank port or the actuator port, a turbine disposed within the valve casing for detecting a flow rate of pressurized oil flowing through a center bypass oil passage connecting the pump port and the tank port by being rotated by the pressurized oil flowing through the center bypass oil passage.

2. 2. The control valve device according to claim 1, wherein a generator is attached to the turbine for generating electric power in response to the rotation of the turbine.

3. 3. The control valve device according to claim 2, wherein a storage battery for storing the electric power generated by the generator is connected to the generator.

4. 2. The control valve device according to claim 1, wherein the turbine is detachably attached to the valve casing.

5. The turbine is a cylindrical support case provided with an inlet and an outlet communicating with the center bypass oil passage, and having a threaded portion formed on an outer circumferential surface thereof to be screwed into the valve casing; a turbine body that is rotatably disposed within the support case and rotated by pressure oil flowing from the inlet to the outlet; 2. The control valve device according to claim 1, further comprising a turbine shaft having one end fixed to the turbine body within the support case and the other end protruding outside the support case.

6. The hydraulic control system includes a self-propelled vehicle body, a working device rotatably provided on the vehicle body, a hydraulic actuator that drives the working device, a hydraulic pump that supplies pressure oil for operation to the hydraulic actuator, and a control valve device that controls the direction of the pressure oil discharged from the hydraulic pump, In a working machine, the hydraulic pump is provided with a variable displacement unit that changes a discharge displacement, and a displacement control mechanism that controls the operation of the variable displacement unit, the control valve device comprises: a valve casing provided with a pump port connected to the hydraulic pump, a tank port connected to a tank, and an actuator port connected to the hydraulic actuator; and a spool valve provided in the valve casing and configured to switch the direction of pressure oil discharged from the hydraulic pump to the pump port to the tank port or the actuator port, a turbine is provided within the valve casing, the turbine being rotated by pressure oil flowing through a center bypass oil passage connecting the pump port and the tank port, thereby detecting a flow rate of pressure oil flowing through the center bypass oil passage; The work machine is characterized in that the capacity control mechanism controls the operation of the capacity variable section in accordance with the rotation of the turbine.

7. a tachometer for detecting the rotation speed of the turbine; 7. The working machine according to claim 6, further comprising a controller that outputs a control signal to the capacity control mechanism based on the number of revolutions of the turbine detected by the tachometer.

8. a generator that generates electricity in response to the rotation of the turbine; 7. The working machine according to claim 6, further comprising a controller that outputs a control signal to the capacity control mechanism based on the electric power generated by the generator.

9. 9. The work machine according to claim 8, further comprising a storage battery for storing the electric power generated by the generator.

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