JP4719423B2 - Pressure control valve - Google Patents

Description

  The present invention relates to a pressure control valve that controls a discharge pressure of a hydraulic pump to a pressure corresponding to a load pressure of an actuator.

  A relief valve is generally known as a pressure control valve for controlling the discharge pressure of a hydraulic pump. The relief valve includes a spool that opens and closes a relief oil passage branched from the discharge oil passage of the hydraulic pump, and a spring that biases the spool toward the closed side of the relief oil passage, and is guided through the pilot oil passage. The hydraulic pump discharge pressure causes the spool to operate directly on the open side of the relief oil path (direct acting type) or indirectly due to the pressure difference generated by operating the pilot piston (balance piston type). I have. Further, in such a pressure control valve, the relief pressure can be variably set according to the load of the actuator by feeding back the load pressure of the actuator and acting it on the closed side of the spool. What has been devised has also been devised (see, for example, the following patent document).

  The pressure-compensated directional flow control valve includes a pressure control valve unit that performs discharge pressure control of the hydraulic pump, and a directional flow control valve unit that performs control to supply pressure oil generated in the pressure control valve unit to the actuator. It is comprised. The pressure control valve section employs the relief valve of the above-described variable relief pressure type, and the discharge pressure of the hydraulic pump can be set to a pressure corresponding to the load pressure of the actuator, so that power loss can be greatly reduced.

In such a relief pressure variable type control valve and pressure compensation type directional flow control valve, the relief pressure is variably set according to the load pressure of the actuator, so an external force is applied to the actuator and vibration (load fluctuation) occurs. In some cases, the load pressure changes accordingly, and the pulsation level of the hydraulic pump discharge pressure may increase. When the pulsation level of the hydraulic pump discharge pressure increases in this way, the supply pressure to the actuator also fluctuates greatly, so that the vibration of the actuator may be further amplified (so-called hunting). In order to prevent such hunting, conventionally, (1) a method of slowing the movement of the spool by providing a damping orifice or choke in the load pressure introduction path connected to the load pressure oil chamber, or (2) an actuator A method for reducing the pressure fluctuation of the pressure oil supplied to the actuator by increasing the inner diameter and length of the hydraulic oil supply line (for example, hose) to the actuator, and (3) suppressing an increase in the pulsation level of the hydraulic pump discharge pressure Means such as a method of additionally providing a relief valve for the purpose have been used.
Japanese Patent No. 339141

  However, in the method (1), there may be a case where an orifice or choke having an appropriate dimension according to the size (for example, cylinder diameter) of the actuator to be used cannot be provided. There were cases where structural constraints were imposed on the installation and routing of the hydraulic oil supply line. In the method (3), in order to effectively prevent hunting while satisfying the operating speed specifications in the entire operating region of the actuator, it is necessary to prepare relief valves with different relief characteristics for each actuator. It was.

  The present invention has been made in view of such a problem, and does not depend on the size of the actuator or the like, and is not subject to structural restrictions such as mounting or routing of the hydraulic oil supply line to the actuator. It is an object of the present invention to provide a pressure control valve having a configuration capable of effectively and inexpensively preventing the above.

The pressure control valve according to the present invention is configured to supply the hydraulic pump discharge oil to an actuator (for example, the hoisting cylinder 91 and the telescopic cylinder 92 in the embodiment ) to operate the actuator, and to control the discharge pressure of the hydraulic pump. This is a pressure control valve that controls the pressure according to the load pressure of the actuator , and is freely movable in a spool receiving hole formed across a relief oil passage that is branched from the discharge oil passage of the hydraulic pump. And a spool that opens and closes the relief oil passage in response to movement in the spool housing hole, and acts on one end of the spool to move the spool to the side that closes the relief oil passage in the spool housing hole. a spring member for biasing manner (e.g., a spring 25 in the embodiment), and the pilot oil passage for guiding the discharge pressure of the hydraulic pump, spray Connected to the pilot oil passage while being formed opposite to the other end of Le, the discharge pressure of the hydraulic pump is caused to act on the other end of the spool, opening the relief oil passage spool in said spool receiving bore side A directional flow control valve ( provided in a pilot oil chamber for applying hydraulic pressure to be moved to the actuator, and a supply oil passage for supplying discharge oil of the hydraulic pump to the actuator to perform supply switching and supply stop control of pressure oil to the actuator) For example, the first and second flow control valves 72 and 75) in the embodiment are connected to a load pressure introduction path that guides the load pressure of the actuator in accordance with the switching state of the directional flow control valve, and one end side of the spool. together formed to connect with a load pressure introduction passage, the load pressure of the actuator is allowed to act on one end of the spool, the relief spool in the spool housing hole A load pressure oil chamber for applying a hydraulic pressure force for moving the side to close the road, the volume of the load pressure oil chamber and a adjustable load pressure oil chamber volume adjusting means, the load pressure oil chamber volume adjustment means a freely piston moves the piston moving space forming part of the load oil chamber I connected to the load pressure oil chamber, the piston moving means for moving the piston in the piston moving space (e.g., a piston moving in the embodiment Knob 32).

In the above case, the internal volume of the piston moving space forming part of the load pressure oil chamber connected to the load pressure oil chamber is rather smaller than the internal volume of the load oil chamber except piston movement space, the piston moving means Is provided with a rod-shaped piston movement knob screwed in a state extending in the direction of the load pressure oil chamber, and the piston is attached to the end of the piston movement knob on the load pressure oil chamber side , and the piston movement knob is rotated. More preferably , the piston is moved in the piston movement space by moving in the axial direction .

In the pressure control valve according to the present invention, an actuator is provided by a load pressure oil chamber volume adjusting means including a piston movable in a piston moving space connected to a load pressure oil chamber and a piston moving means for moving the piston in the piston moving space. By adjusting the volume of the load pressure oil chamber according to the size (for example, the cylinder diameter) or the like, it is possible to suppress a change in the load pressure transmitted to the load pressure oil chamber even when the load of the actuator varies. For this reason, the relief pressure set in the pressure control valve only changes at a level lower than the load fluctuation of the actuator, and the pulsation level of the hydraulic pump discharge pressure is kept small, so that the actuator hunting is effective. Can be prevented. And since such an effect can be obtained only by adjusting the volume of the load pressure oil chamber, it is not subject to structural restrictions such as mounting or routing of the hydraulic oil supply line to the actuator in addition to the size of the actuator, etc. In addition, the configuration is highly flexible.

In the pressure control valve, the load pressure oil chamber volume adjusting means includes a piston movable in a piston moving space connected to the load pressure oil chamber, and a piston moving means for moving the piston in the piston moving space (for example, implementation The piston movement space is composed of a piston movement knob 32), or one end of the piston movement space is connected to the load pressure oil chamber and the inner volume is smaller than the inner volume of the load pressure oil chamber. , comprising a piston moving knob screwed to the rod-like in a state of extending in the load oil chamber direction, the piston is mounted on the load pressure oil chamber side end portion of the piston moving the knob, the increase in pulsation level of the oil pressure pump discharge pressure Compared to a conventional method in which a relief valve for the purpose of suppressing the above is separately added, the above-described effect can be obtained with an inexpensive configuration.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 2 shows an aerial work vehicle 80 having a hydraulic circuit having a pressure compensated directional flow control valve 1 to which the present invention is applied. First, the construction of the aerial work vehicle 80 will be described. . The aerial work vehicle 80 includes tire-type wheels 82, 82,..., A truck-type traveling body 81 that can be operated from a driver's seat 83, a swivel base 84 provided on the traveling body 81, and the turning A telescopic boom 87 attached to the upper part of a support column 85 extending upward from the base 84 by a foot pin 86 so as to be swingable up and down, and a work board for operator boarding attached to the tip of the boom 87. 89.

  The swivel base 84 is attached to the rear portion of the traveling body 81 so as to be capable of rotating 360 degrees around the vertical axis, and can be operated to turn horizontally by hydraulically driving a turning motor 93 built in the traveling body 81. The boom 87 has a structure in which a proximal boom 87a, an intermediate boom 87b, and a distal boom 87c are assembled in a nested manner, and is telescopically operated in the longitudinal direction (axial direction) by hydraulically driving a built-in telescopic cylinder 92. Can do. Further, the boom 87 can be raised and lowered within the upper and lower surfaces by hydraulically driving a hoisting cylinder 91 straddled between the base end boom 87a and the support column 85.

  The work bench 89 is rotatably attached to a vertical post 88 that is always held in a vertical posture at the tip of the tip boom 87c, and hydraulically drives a swing motor 94 built in the work bench 89 itself. It is possible to swivel (swing) around the vertical post 88. Here, since the vertical post 88 is always maintained in the vertical posture as described above, the floor surface of the work table 89 is always held horizontally regardless of the posture (the undulation angle) of the boom 87.

  Jacks 95, 95,... Are provided at the front, rear, left and right portions of the traveling body 81 to support the traveling body 81 in operation in a stable state. Each jack 95 includes an outer jack (cylinder tube) 95a suspended from the traveling body 81, an inner jack (piston rod) 95b provided in the outer jack 95a and movable in the vertical direction, and a lower end of the inner jack 95b. And a jack pad 95c that is swingably provided at the portion. The inner jack 95b is moved downward, and the jack pad 95c is grounded to the ground and stretched to lift the traveling body 81. Can be supported. Each of these jacks 95 can be put into a retracted state by moving the inner jack 95b upward to completely contract.

  On the work table 89, a boom operation lever 96 and a work table swing operation lever 97 are provided. The boom operation lever 96 is a lever for operating the hoisting cylinder 91, the telescopic cylinder 92 and the turning motor 93, and the work table swing operation lever 97 is a lever for operating the swing motor 94. For this reason, the operator OP who has boarded the work platform 89 operates the boom operation lever 96 to move the boom 30 up, down, extend, and rotate, and operates the work table swing operation lever 97 to move the work platform 89 to the vertical post. The work table 89 can be moved in a desired manner by swinging around 88, and work can be performed at an arbitrary high position.

  FIG. 3 shows a part of the hydraulic circuit provided in the aerial work vehicle 80, and shows a part related to the operation control of the hoisting cylinder 91 and the telescopic cylinder 92. In the hydraulic circuit relating to the operation control of the hoisting cylinder 91 and the telescopic cylinder 92, the hydraulic pump P is driven by an engine (or an electric motor provided separately) of the traveling body 81 and supplies the discharge pressure into the discharge oil passage 50. .

  As shown in FIG. 3, the pressure compensated directional flow control valve 1 includes a pressure control valve portion 2 and a directional flow control valve portion 3. The pressure control valve unit 2 includes a pressure control valve 10 and a plurality of oil passages attached thereto. The directional flow control valve unit 3 includes a first pressure adjustment valve 71, a second pressure adjustment valve 74, and a first directional flow control valve. 72, a second direction flow control valve 75, a shuttle valve 77, and a plurality of oil passages attached thereto.

  As shown in FIG. 3, the discharge oil passage 50 of the hydraulic pump P includes an oil passage 51 that supplies pressure oil to the hoisting cylinder 91, an oil passage 55 that supplies pressure oil to the telescopic cylinder 92, and a relief connected to the oil tank T. Branches to an oil passage 59. The first pressure regulating valve 71 is interposed in the oil passage 51, and the pressure in the oil passage 51 is increased to a pressure suitable for the operation of the hoisting cylinder 91 and supplied to the P port of the first direction flow control valve 72. To do. Further, the second pressure regulating valve 74 is interposed in the oil passage 55, and the pressure in the oil passage 55 is increased to a pressure suitable for the operation of the expansion / contraction cylinder 92 to increase the P port of the second direction flow control valve 75. To supply.

  The A port of the first direction flow control valve 72 is connected to the bottom side oil chamber 91 a of the hoisting cylinder 91 via the oil passage 53, and the B port of the first direction flow control valve 72 is the rod side oil chamber of the hoisting cylinder 91. 91 b and the oil passage 54 are connected to each other. The first direction flow rate control valve 72 is an electromagnetic pilot proportional valve, and the pressure oil in the oil passage 51 is boosted by an electromagnetic pilot control of a spool (not shown) performed by a controller (not shown). Control of switching and direction switching. Specifically, when the spool (not shown) is located at the neutral position 72a, the P, A, and B ports are blocked and the T port is connected to the oil tank T to stop the operation of the hoisting cylinder 91. When located at the side switching position 72b, the P port is connected to the A port and the B port is connected to the T port to supply the pressure oil into the bottom side oil chamber 91a of the hoisting cylinder 91, and the hoisting cylinder 91 is operated to extend (this) As a result, the boom 87 rises). When the spool is positioned at the contraction side switching position 72c, the P port is connected to the B port and the A port is connected to the T port to supply the pressure oil into the rod side oil chamber 91b of the hoisting cylinder 91. The contraction operation is performed (this causes the boom 87 to fall down).

  Further, when the first direction flow control valve 72 is positioned at the extension side switching position 72b or the contraction side switching position 72c for operating the hoisting cylinder 91, the pressure oil in the P port is adjusted from the oil passage 52 to the first pressure adjustment. While acting on the valve 71 and energizing its spool (not shown) to the open side (the direction in which the oil passage 51 is opened), the oil passage 52 is drained when it is in the neutral position 72a. Yes. For this reason, the pressure in the oil passage 51 is maintained at a higher value when the hoisting cylinder 91 is operated than when the hoisting cylinder 91 is not operated.

  A first counter balance valve 73 is interposed in the oil passages 53, 54 connecting the first direction flow control valve 72 and the undulation cylinder 91. The first direction flow control valve 72 functions to constantly apply a back pressure in the bottom side oil chamber 91a of the hoisting cylinder 91.

  The A port of the second direction flow control valve 75 is connected to the bottom side oil chamber 92 a of the expansion cylinder 92 via the oil passage 57, and the B port of the second direction flow control valve 75 is connected to the rod side oil chamber of the expansion cylinder 92. 92b and the oil passage 58 are connected. The second direction flow rate control valve 75 is also an electromagnetic pilot proportional valve, and is pressurized by an oil pilot 55 (second pressure adjusting valve 74) by an electromagnetic pilot control of a spool (not shown) performed by a controller (not shown). (Controlled pressure oil) is controlled intermittently and direction switching. Specifically, when the spool (not shown) is in the neutral position 75a, the P port is blocked and the A, B and T ports are connected to the oil tank T to stop the operation of the telescopic cylinder 92. When it is positioned at the side switching position 75b, the P port is connected to the A port and the B port is connected to the T port to extend the telescopic cylinder 92 (this causes the boom 87 to extend). Further, when the spool is positioned at the contraction side switching position 75c, the telescopic cylinder 92 is contracted by connecting the P port to the B port and the A port to the T port (the boom 87 contracts).

  Further, when the second direction flow control valve 75 is located at the extension side switching position 75b or the contraction side switching position 75c for operating the telescopic cylinder 92, the pressure oil in the P port is adjusted from the oil passage 56 to the second pressure adjustment. While acting on the valve 74 to urge the spool (not shown) to the open side (the direction to open the oil passage 55), the oil passage 56 is drained when the valve 74 is in the neutral position 75a. Yes. For this reason, the pressure in the oil passage 55 is maintained at a higher value when the expansion cylinder 92 is operated than when the expansion cylinder 92 is not operated.

  A second counter balance valve 76 is interposed in both the oil passages 57 and 58 that connect the second direction flow control valve 75 and the telescopic cylinder 92. The second direction flow control valve 75 functions to constantly apply a back pressure to both the bottom side oil chamber 92a and the rod side oil chamber 92b of the expansion / contraction cylinder 92.

  As shown in FIG. 3, the pressure control valve 10 is interposed in the relief oil passage 59 that is branched from the discharge oil passage 50 of the hydraulic pump P, and the discharge pressure of the hydraulic pump P becomes the set pressure. When it reaches, a part of the pressure oil in the discharge oil passage 50 is discharged from the relief oil passage 59 to the oil tank T so that the discharge pressure of the hydraulic pump P does not exceed a predetermined pressure (relief pressure). . That is, in the pressure compensation type directional flow control valve 1, the discharge pressure from the hydraulic pump P is controlled to a predetermined pressure (relief pressure) or less in the pressure control valve unit 2, and then the first directional flow control valve 72 and the second directional flow control valve 1. By the operation of the directional flow control valve 75, the pressure (pressure increase) is increased to a pressure suitable for the operation of the actuator (the undulation cylinder 91 and the expansion cylinder 92).

  As shown in FIG. 1, the pressure control valve 10 includes a valve body 20 including a body portion 21 in which a cylindrical spool accommodating hole 20 a is provided and a cap portion 22 attached to the upper portion of the body portion 21. The spool 24 is movably provided in the spool housing hole 20a so as to be movable in the vertical direction (the vertical direction in FIG. 1; the same applies hereinafter), and is retracted between the spool 24 and the cap portion 22 so that the spool 24 is always downward. And a spring 25 for biasing.

  The cap portion 22 of the valve body 20 has a hollow cylindrical portion 23 that is formed in a cylindrical shape and extends downward. The hollow cylindrical portion 23 is attached so as to be fitted into the spool accommodating hole 20a from above. Yes. As shown in FIG. 1, a piston moving space 22 a that is located concentrically with and communicates with the internal space of the hollow cylindrical portion 23 is provided inside the cap portion 22. The inner diameter of the piston moving space 22a is slightly smaller than the inner diameter of the hollow cylindrical portion 23, and a step surface 22b is formed at the boundary.

  The upper portion of the spool 24 is formed in a hollow cylindrical shape that is recessed downward and has a bottom surface 24a. The internal space and the internal space of the hollow cylindrical portion 23 of the cap portion 22 form a single continuous load pressure oil chamber 26. Forming. The spring 25 is installed (contracted) so as to extend vertically in the load pressure oil chamber 26, and its upper end is in contact with the step surface 22 b and its lower end is in contact with the bottom surface 24 a of the spool 24. .

  A spool oil passage 27 having a shape extending in the vertical direction and opening downward is provided at the lower portion of the spool 24, and a plug 28 is attached to the lower portion of the spool 24 so as to close the oil passage 27 in the spool. Yes. Further, an inlet oil passage 29 and an outlet oil passage 30 communicating with the spool oil passage 27 are provided in the lower portion of the spool 24 so as to extend horizontally from the top.

  In the piston moving space 22a formed in the cap portion 22, a piston 31 having a ring-shaped oil seal 31a fitted on the outer peripheral portion is provided so as to be movable up and down. The piston 31 is attached with a lower end portion of a rod-shaped piston movement knob 32 screwed in a state where the upper portion of the cap portion 22 extends in the vertical direction, and the piston movement is performed by twisting the piston movement knob 32. The piston 31 can be moved in the vertical direction within the space 22a. The piston 31 and the piston moving knob 32 constitute load pressure oil chamber volume adjusting means capable of adjusting the volume of the load pressure oil chamber 26.

  The body 21 of the valve body 20 includes a pressure oil chamber 41 and a pressure oil chamber communication passage 41a connected thereto, a pilot oil chamber 42 and a pilot oil chamber communication passage 42a connected thereto, a drain oil chamber 43 and A drain oil chamber communication passage 43 a connected to this and a load pressure oil chamber communication passage 26 a connected to the load pressure oil chamber 26 are provided. A first orifice 42b is provided in the pilot oil chamber communication passage 42a, and a second orifice 26b is provided in the load pressure oil chamber communication passage 26a.

  The spool 24 is movable up and down in the spool accommodation hole 20a, and the lower limit position thereof is a position where the bottom surface of the plug 28 provided in the lower portion of the spool 24 itself is brought into contact with the bottom surface of the spool accommodation hole 20a. The upper limit position is a position where the upper end 24b of the spool 24 itself is brought into contact with the lower end of the hollow cylindrical portion 23 from below (FIG. 1 shows a state where the spool 24 is in the lower limit position). Here, when the spool 24 is at the lower limit position, the inlet oil passage 29 is positioned below the pressure oil chamber 41 and is closed by the inner peripheral surface of the spool housing hole 20a, and the outlet oil passage 30 is drain oil. It will be in the state located in chamber 43. When the spool 24 rises from this lower limit position, the inlet oil passage 29 comes to be positioned in the pressure oil chamber 41. On the other hand, the outlet oil passage 30 is always located in the drain oil chamber 43 regardless of the position of the spool 24.

  The pressure oil chamber communication passage 41a is connected to an oil passage on the side of the hydraulic pump P constituting the relief oil passage 59 (this is referred to as a pressure oil passage 59a), and the relief oil passage 59 is connected to the drain oil chamber communication passage 43a. Is connected to an oil passage on the oil tank T side (this is a drain oil passage 59b). Further, an oil passage branched from the pressure oil passage 59a (this is referred to as a pilot oil passage 59c) is connected to the pilot oil chamber communication passage 42a.

  As shown in FIG. 3, the branched oil 52 a branched and extended from the oil passage 52 connected to the first directional flow control valve 72 and the branched oil extended from the oil passage 56 connected to the second directional flow control valve 75. The passage 56a merges, and the shuttle valve 77 is interposed at the junction. The shuttle valve 77 connects the branch oil passage having the larger pressure between the two branch oil passages 52a and 56a to the load pressure introduction passage 60 connected to the load pressure oil chamber communication passage 26a of the pressure control valve 10, and the pressure is increased. Close the smaller branch oil passage. For this reason, the larger pressure of the pressure in the branch oil passage 52 a and the pressure in the branch oil passage 56 a, that is, the larger pressure of the load pressure of the undulation cylinder 91 and the load pressure of the telescopic cylinder 92 is the load pressure introduction passage 60. Then, it is introduced into the load pressure oil chamber 26 via the load pressure oil chamber communication passage 26a (the second orifice 26b is provided in the middle).

  In the pressure control valve 10 having such a configuration, the discharge pressure of the hydraulic pump P acts in the pressure oil chamber 41 via the discharge oil passage 50, the pressure oil passage 59a, and the pressure oil chamber communication passage 41a, and the pilot oil passage. It acts in the pilot oil chamber 42 via 59c and the pilot oil chamber communication passage 42a (the first orifice 42b is provided in the middle). Here, when pressure oil is not supplied from the hydraulic pump P into the discharge oil passage 50, the spool 24 is pushed down by the urging force of the spring 25 and the bottom surface of the plug 28 attached to the lower portion is used as the bottom surface of the spool housing hole 20a. It will be in the state made to contact. When the discharge pressure of the hydraulic pump P increases from here, the pressure in the pilot oil chamber 42 tends to push the spool 24 upward, and the pressure in the spring 25 and the load pressure oil chamber 26 The spool 24 is positioned at a position where the force that pushes the pressure downward 24 balances, but the inlet oil passage 29 formed in the spool 24 is positioned below the pressure oil chamber 41. Since the pressure oil chamber 41 is closed by the outer peripheral surface of the spool 24, the relief oil passage 59 is maintained closed by the spool 24. For this reason, the pressure oil discharged from the hydraulic pump P is not discharged from the relief oil passage 59, and the pressure in the discharge oil passage 50 further increases.

  When the discharge pressure of the hydraulic pump P further rises and reaches the cracking pressure (relief start pressure) of the pressure control valve 10, the inlet oil passage 29 formed in the spool 24 opens into the pressure oil chamber 41. Part of the pressure oil discharged from the pump P into the discharge oil passage 50 flows into the oil passage 27 in the spool through the pressure oil passage 59a, the pressure oil chamber communication passage 41a, the pressure oil chamber 41, and the inlet oil passage 29. Then, the oil is discharged to the oil tank T through the outlet oil passage 30, the drain oil chamber 43, the drain oil chamber communication passage 43a, and the drain oil passage 59b. That is, the relief oil passage 59 is opened and a part of the pressure oil in the discharge oil passage 50 is drained. Here, the larger the discharge pressure of the hydraulic pump P, the larger the communication opening area between the inlet oil passage 29 and the pressure oil chamber 41, and the corresponding flow rate of the hydraulic oil discharged from the relief oil passage 59 to the oil tank T. Will increase. At the upper limit position where the spool 24 can be located (as described above, the position where the upper end 24b of the spool 24 abuts the lower end of the hollow cylindrical portion 23), the total amount of pressure oil discharged by the hydraulic pump P is the relief oil passage. Relief from 59 (the discharge pressure of the hydraulic pump P at this time corresponds to the relief pressure). For this reason, the pressure in the discharge oil passage 50 does not become higher than the relief pressure, and the situation where the piping and the actuator connected thereto are damaged due to the pressure in the discharge oil passage 50 continuing to rise is prevented.

  Here, in the load pressure oil chamber 26 as described above, the larger one of the load pressure of the hoisting cylinder 91 and the load pressure of the expansion / contraction cylinder 92 is introduced (feedback) as the load pressure. Along with the urging force, the discharge pressure of the hydraulic pump P applied in the pilot oil chamber 42 acts against the urging force that moves the spool 24 upward, so that the load pressure of the hoisting cylinder 91 and the telescopic cylinder The relief pressure corresponding to the larger one of the 92 load pressures is variably set. The reason why the relief pressure is set in accordance with the larger one of the load pressure of the undulating cylinder 91 and the load pressure of the expansion / contraction cylinder 92 is that both the cylinders 91 and 92 can be operated simultaneously. Because.

  Thus, in this pressure compensation type directional flow control valve 1, the load pressure of the actuator that operates by receiving the discharge pressure of the hydraulic pump P (here, the larger one of the load pressure of the undulating cylinder 91 and the load pressure of the telescopic cylinder 92). Pressure) is introduced into the load pressure oil chamber 26. At this time, when an external force is applied to the boom 87 and vibrations, that is, load fluctuations occur in the actuator, the load fluctuations cause the load pressure oil chamber 26 to move into the load pressure oil chamber 26. The pressure transmitted to (load pressure) also changes. When the pressure in the load pressure oil chamber 26 changes in this way, the relief pressure set in the pressure control valve 10 also changes, so the pulsation level of the hydraulic pump P discharge pressure increases, and as a result, the initial vibration of the actuator results. Will be amplified (hunting). In order to prevent such adverse effects, the volume in the load pressure oil chamber 26 may be adjusted (expanded here) according to the size of the actuator (for example, the cylinder diameter), etc. In the valve 1, this can be done by twisting the piston moving knob 32 to move the piston 31 in the piston moving space 22a. That is, as can be seen from FIG. 1, since the piston moving space 22a formed in the cap portion 22 communicates with the spool accommodation hole 20a formed in the body portion 21, the piston 31 is moved in the piston moving space 22a. Thus, the volume of the load pressure oil chamber 26 can be adjusted.

  Here, if the volume in the load pressure oil chamber 26 is V, the flow rate of the hydraulic oil flowing into the load pressure oil chamber 26 is Q, and the inflow time of the hydraulic oil into the load pressure oil chamber 26 is T, the load pressure The pressure change ΔP in the oil chamber 26 can be expressed as an equation ΔP = k / V × Q × T, where k is the bulk modulus. FIG. 4 is a graph showing the pressure change in the load pressure oil chamber 26 according to the volume of the load pressure oil chamber 26 based on such an expression. The hydraulic oil inflow time is shown on the vertical axis, and the pressure in the load pressure oil chamber 26 is shown on the vertical axis. In the drawing, V1 and V2 are volumes of the load pressure oil chamber 26 (including a portion of the piston moving space 22a that communicates with the load pressure oil chamber 26 and contributes to volume adjustment (expansion) of the load pressure oil chamber 26). Yes, V1 <V2. As can be seen from this graph, if the volume of the load pressure oil chamber 26 is increased, the pressure change in the load pressure oil chamber 26 per unit time becomes smaller. Since the pressure change in the load pressure oil chamber 26 affects the pulsation level of the hydraulic pump P discharge pressure, it is possible to reduce the pulsation level of the hydraulic pump P discharge pressure by increasing the volume of the load pressure oil chamber 26. It is. When the load pressure passes through the orifice (for example, the orifice 26b provided in the load pressure oil chamber communication passage 26a) and flows into the load pressure oil chamber 26 as in this embodiment, the effect is small. Even a change (volume change of the load pressure oil chamber 26) can be sufficiently obtained. However, since the time until the pressure in the load pressure oil chamber 26 reaches a predetermined pressure becomes longer, the volume of the load pressure oil chamber 26 does not have to be increased, and the size of the actuator (for example, the cylinder diameter) ) Etc., it is necessary to select an optimal value.

  Thus, in the pressure compensation type flow control valve 1, by adjusting the volume of the load pressure oil chamber 26 according to the size of the actuator and the like by the load pressure oil chamber volume adjusting means including the piston 31 and the piston moving knob 32, Even when there is a change in the load of the actuator, the change in the load pressure transmitted to the load pressure oil chamber 26 can be kept small. For this reason, the relief pressure set in the pressure control valve unit 1 changes only at a level lower than the load fluctuation of the actuator, and the pulsation level of the hydraulic pump P discharge pressure is kept small. It can be effectively prevented. Such an effect can be obtained only by adjusting the volume of the load pressure oil chamber 26 (in this case, expansion), so that there are structural restrictions such as the size and size of the actuator, as well as the mounting and routing of the hydraulic oil supply line to the actuator. It has a low cost and high design freedom.

  In the pressure compensation flow control valve 1, the load pressure oil chamber volume adjusting means has a piston 31 that is movable in the load pressure oil chamber 26 and a piston movement that moves the piston 31 in the load pressure oil chamber 26. Since it is composed of the knob 32, the above-mentioned effect can be obtained with a low-cost configuration compared to the conventional method such as adding a relief valve separately for the purpose of suppressing an increase in the pulsation level of the discharge pressure of the hydraulic pump P. it can.

  FIG. 5 shows a modified example of the load pressure oil chamber volume adjusting means constituting the pressure compensated directional flow control valve 1. A piston 31 movable within the load pressure oil chamber 26 and a piston moving knob 32 for moving the piston 31 are provided. Instead of providing, a volume adjusting member 34 having an internal space 35 communicating with the load pressure oil chamber 26 is detachably provided on the cap portion 22. The volume adjusting member 34 includes a connection fitting 34a that is screwed onto the cap portion 22, a hollow hose 34b that is connected to the cap portion 22 by the connection fitting 34a, and an end cap 34c that is attached to the end of the hose 34b. Consists of. If a plurality of such volume adjusting members 34 having different lengths (or thicknesses) are prepared, they are introduced into the load pressure oil chamber 26 by replacing them according to the size of the actuator. It is possible to suppress a change in the load pressure. The volume adjusting member 34 has an internal space that is detachably attached to the pressure control valve 10 and communicates with the load pressure oil chamber 26, in addition to the configuration including the connection fitting 34a, the hose 34b, and the end cap 34c. It may be. As a specific example, the container has a screw part that can be screwed into the cap part 22, is detachable from the cap part 22, and has a space capable of communicating with the load pressure oil chamber 26 inside. In such a container, if a plurality of containers having different internal volumes are prepared, the change in the load pressure supplied into the load pressure oil chamber 26 can be suppressed by replacing them according to the size of the actuator. It is possible. Even with such a configuration, the above-described effects can be obtained at low cost.

  The pressure compensation type directional flow control valve 1 can be configured as a so-called composite valve in which the pressure control valve portion 2 (pressure control valve 10) and the directional flow control valve portion 3 are integrally formed. Can also be used as a single product without being incorporated into such a composite valve. The pressure control valve according to the present invention corresponds to a pressure control valve that can be used as a single component that is not incorporated into the composite valve. In this case, the pressure control valve can have the same configuration as that of the pressure control valve 10 incorporated in the pressure-compensated directional flow control valve 1 described above.

  Although the preferred embodiments of the present invention have been described so far, the scope of the present invention is not limited to those shown in the above-described embodiments. For example, in the above-described embodiment, the directional flow control valve (the first directional flow control valve 71 and the second directional flow control valve 75) included in the directional flow control valve unit 3 of the pressure compensation type directional flow control valve is proportional to the electromagnetic pilot. The valve is not necessarily an electromagnetic pilot proportional valve as long as it is a directional flow control valve. That is, it may be an electromagnetic proportional valve that moves the spool directly (regardless of pilot pressure) by an electromagnetic solenoid, a manual type directional flow control valve that is manually operated, or the like.

  In the above-described embodiment, the actuators controlled in the pressure control valve unit 2 in the pressure compensation type directional flow control valve 1 are the undulation cylinder 91 and the telescopic cylinder 92. However, this is an example, and other hydraulic cylinders are used. Or a hydraulic motor etc. may be sufficient. Further, the number of actuators is not necessarily two, and may be one or three or more.

  Further, the hydraulic circuit including the pressure control valve according to the present invention is not limited to the aerial work vehicle shown in the above-described embodiment, and can be applied to other power machines in general.

It is a longitudinal cross-sectional view of the pressure control valve which comprises the pressure control valve part of the pressure compensation type directional flow control valve to which this invention was applied. It is a side view of an aerial work vehicle having a hydraulic circuit provided with the pressure compensation type directional flow control valve. It is a part of the hydraulic circuit provided in the aerial work vehicle and is a part related to the operation control of the hoisting cylinder and the telescopic cylinder. It is a graph which shows the pressure change in a load pressure oil chamber according to the size of the volume of a load pressure oil chamber. It is a figure which shows the modification of the load pressure oil chamber volume adjustment means which comprises the said pressure compensation type | mold direction flow control valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pressure compensation type directional flow control valve 2 Pressure control valve part 3 Directional flow control valve part 10 Pressure control valve 22a Piston movement space 24 Spool 25 Spring (spring member)
26 Load pressure oil chamber 31 Piston (Load pressure oil chamber volume adjusting means)
32 Piston movement knob (Load pressure oil chamber volume adjustment means, piston movement means)
34 Volume adjusting member (Load pressure oil chamber volume adjusting means)
42 Pilot oil chamber 50 Discharge oil passage 59 Relief oil passage 59c Pilot oil passage 60 Load pressure introduction passage 72 First direction flow control valve (directional flow control valve)
75 Second direction flow control valve (directional flow control valve)
77 Shuttle valve 91 Relief cylinder (actuator)
92 Telescopic cylinder (actuator)
P Hydraulic pump

Claims (2)

A pressure control valve configured to supply the discharge oil of the hydraulic pump to the actuator to operate the actuator, and control the discharge pressure of the hydraulic pump to be a pressure corresponding to a load pressure of the actuator ;
The relief oil passage is movably provided in a spool accommodation hole formed across a relief oil passage that is branched from the discharge oil passage of the hydraulic pump, and the relief oil passage is moved according to the movement in the spool accommodation hole. A spool that opens and closes;
A spring member that acts on one end side of the spool and urges the spool to move to the side that closes the relief oil passage in the spool housing hole ;
A pilot oil passage for guiding the discharge pressure of the hydraulic pump;
The spool is formed opposite to the other end of the spool and connected to the pilot oil passage, and the discharge pressure of the hydraulic pump is applied to the other end of the spool so that the spool is relieved in the spool receiving hole. A pilot oil chamber for applying oil pressure to move the oil passage to the open side ;
A switching direction of the directional flow control valve is connected to a directional flow control valve that is provided in a supply oil passage that supplies the discharge oil of the hydraulic pump to the actuator and performs supply switching and supply stop control of pressure oil to the actuator. A load pressure introduction path for guiding the load pressure of the actuator according to
The relief oil passage is formed facing the one end side of the spool and is connected to the load pressure introduction path, and the load pressure of the actuator is applied to one end side of the spool so that the spool is in the spool accommodation hole. A load pressure oil chamber for applying an oil pressure to move to the closing side ,
Load pressure oil chamber volume adjustment means capable of adjusting the volume of the load pressure oil chamber,
The load pressure oil chamber volume adjusting means includes a movable piston moves the piston moving space forming part of the load pressure oil chamber I connected to the load pressure oil chamber, said piston in said piston moving space A pressure control valve comprising piston moving means for moving. The internal volume of the piston moving space connected to the load pressure oil chamber forming part of the load pressure oil chamber, rather less than the internal volume of the load pressure oil chamber except for the piston moving space,
The piston moving means includes a rod-like piston moving knob screwed in a state extending in the direction of the load pressure oil chamber,
The piston is attached to an end portion of the piston movement knob on the load pressure oil chamber side , and the piston movement knob is rotated and moved in the axial direction so that the piston is moved in the piston movement space. the pressure control valve according to claim 1, characterized in that it is configured.

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