JP2008061551A - Elevator for implement of ground working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To absorb dispersion of dimensional accuracy of an electromagnetic control valve for a composite control valve in combination of the electromagnetic control valve and a check control valve openable by pushing with a spool of the electromagnetic control valve in an elevator for an implement of a ground working vehicle. <P>SOLUTION: The composite control valve 70 is composed of the electromagnetic control valve 80 for driving the spool 78 in the axial direction with a solenoid 74, reducing a hydraulic pressure when there is the input hydraulic pressure, feeding the hydraulic pressure to a lowering valve and projecting the tip of the spool when there is no input hydraulic pressure further from the maximum stroke when there is the input hydraulic pressure with a prescribed extent of projection, and the check control valve 90 for taking a holding position for holding the hydraulic pressure of a cylinder and a hydraulic pressure releasing position for releasing the hydraulic pressure of the cylinder. A check valve housing 82 of the check control valve 90 can be moved in the axial direction from a casing 72 and a gap ΔS between the electromagnetic control valve 80 and the check control valve 90 in the axial direction is adjusted by an adjusting screw 94. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a work implement lifting apparatus for a ground work vehicle, and more particularly to a work machine lift apparatus for a ground work vehicle that lifts and lowers the work equipment using hydraulic pressure.

  A vehicle that performs work on the ground, such as a tractor, mainly uses a hydraulic cylinder to move a working machine such as a rotary tiller up and down with respect to the ground. In this case, as a lifting device, a lift valve is provided between the hydraulic pump operated by the vehicle engine and the lifting hydraulic cylinder, and between the tank open to the atmosphere and the lifting hydraulic cylinder. A lowering valve is provided, and the working machine is moved up and down at a freely adjustable speed by driving and controlling the raising valve and the lowering valve, for example, with a proportional pressure reducing valve type electromagnetic control valve. Here, the electromagnetic control valve electrically controls the hydraulic pressure of oil supplied from the hydraulic pump by a solenoid, and the rising valve and the lowering valve are, for example, oil by a pilot hydraulic pressure controlled by the electromagnetic control valve. It is a fluid control valve that switches the flow direction. In this way, by using a switching valve that is controlled by pilot hydraulic pressure instead of using an electromagnetic control valve as an up valve and a down valve, the electromagnetic control valve itself can be downsized and a commercially available low-cost valve can be used. .

  By the way, when the lowering valve is controlled using the electromagnetic control valve, the pilot oil pressure cannot be obtained unless the engine is driven to operate the hydraulic pump. That is, even if it is noticed that the work implement has not been lowered after the engine has been stopped, the work implement cannot be lowered while the engine is stopped, and the engine must be started one by one. In order to avoid this, it suffices if the hydraulic cylinder can be drained with the engine stopped.

  For example, in Patent Document 1, a lowering valve for releasing hydraulic pressure of a hydraulic cylinder by a solenoid is provided in a working machine lifting device for a tractor, and further, a check ball type check valve is pushed open by the operation of the lowering valve. A working machine lifting device that can release the hydraulic pressure is disclosed. According to this technique, the hydraulic pressure of the hydraulic cylinder can be released only by operating the solenoid. For example, when it is desired to lower the work implement, it is not necessary to drive the engine and operate the hydraulic pump.

  Moreover, since the check ball type check valve is used in Patent Document 2 as a problem in Patent Document 1, when this check valve is pushed open, oil flows through the gap between the springs. It points out that a loss occurs. Therefore, it is disclosed that when the hydraulic pump is not in operation, a rod connected to the iron core of the electromagnetic pilot valve pushes the poppet valve and the spring of the poppet valve is provided outside the passage through which oil escapes.

Japanese Patent Laid-Open No. Sho 63-32409 Japanese Examined Patent Publication No. 6-68338

  As described above, according to the prior art, the cylinder is combined with the solenoid control valve driven by the solenoid and the valve pushed open by the moving body driven by the solenoid, so that the cylinder can be used even when no hydraulic pressure is supplied. The oil can be drained.

  Thus, an electromagnetic control valve that meets the product specifications is used, and a composite valve that combines a valve that is pushed open by the spool is designed in accordance with the operating point of the spool. However, the operating point of the spool varies depending on the dimensional accuracy of the electromagnetic control valve, and the operation of the valve that is pushed open by the spool varies. In some cases, the timing of draining the cylinder oil may be shifted.

  An object of the present invention is to provide a ground control vehicle that can absorb variations in the dimensional accuracy of an electromagnetic control valve with respect to a composite control valve that combines an electromagnetic control valve and a check valve that can be pushed open by a spool of the electromagnetic control valve. It is providing a working machine lifting device.

  A working machine lifting device for a ground working vehicle according to the present invention includes a lowering valve provided in a passage for returning oil of a hydraulic cylinder for lifting the working machine to a tank, and a composite control valve that controls the operation of the lowering valve, The composite control valve drives the spool in the axial direction by a solenoid, and when there is input hydraulic pressure, it reduces the hydraulic pressure by the cooperation of the spool and sleeve and supplies it to the lowering valve. An electromagnetic control valve that protrudes with a predetermined amount of protrusion beyond the maximum stroke when there is input hydraulic pressure, a holding position that is coaxial with the electromagnetic control valve and that holds the hydraulic pressure of the cylinder, and a hydraulic pressure release position that releases the hydraulic pressure of the cylinder A check valve, and the check valve is slidably inserted into the guide hole of the check valve housing and has a guide hole coaxial with the electromagnetic control valve. Along A check valve body that has a stop position in one direction, a spring member that holds the check valve body against the hydraulic pressure of the cylinder toward the stop position and holds the cylinder oil pressure, and a check valve housing. On the other hand, when the spool of the electromagnetic control valve is in a position within the maximum stroke and the biasing means for applying an axial biasing force against the pressing force of the spring member, Adjusting means for adjusting the axial position of the check valve housing relative to the electromagnetic control valve so as to move the check valve body and release the hydraulic pressure of the cylinder when the spool of the control valve protrudes with a predetermined protrusion amount. It is characterized by that.

  The adjusting means includes a holding portion that holds the check valve housing with respect to the electromagnetic control valve, an adjustment screw that at least partially meshes with a screw portion provided in the holding portion, and a tip portion that contacts the check valve housing; It is preferable to have.

  The adjusting means includes at least a part of a holding portion for holding the check valve housing with respect to the electromagnetic control valve and a screw portion provided on the holding portion, and a tip portion of the adjusting portion via the intermediate body. It is preferable to have an adjusting screw in contact therewith.

  The working machine lifting device for a ground working vehicle according to the present invention includes a lowering valve provided in a passage for returning the oil of the hydraulic cylinder for lifting the working machine to the tank, and a composite control valve for controlling the operation of the lowering valve. The composite control valve drives the spool in the axial direction by a solenoid, and when there is an input hydraulic pressure, it reduces the hydraulic pressure by the cooperation of the spool and the sleeve and supplies it to the lowering valve, and when there is no input hydraulic pressure, the spool An electromagnetic control valve that projects the tip of the cylinder with a predetermined amount of protrusion beyond the maximum stroke when there is input hydraulic pressure, a holding position that holds the cylinder's hydraulic pressure, and a hydraulic pressure that releases the cylinder's hydraulic pressure. A non-return valve, and a housing that holds the electromagnetic control valve and the check valve coaxially and integrally holds the check valve, and the check valve has a guide hole coaxial with the electromagnetic control valve. Axis with respect to the housing Check valve housing that is movable in the direction, a check valve body that is slidably inserted into the guide hole of the check valve housing and has a stop position in one direction along the axial direction, and a check valve body Is pressed against the cylinder hydraulic pressure toward the stop position, and a biasing force is applied to the check valve housing and an axial biasing force against the pressing force of the spring member to the check valve housing. And when the spool of the electromagnetic control valve protrudes by a predetermined protruding amount so that the check valve body takes a stopped position when the spool of the electromagnetic control valve is at a position within the maximum stroke. And adjusting means for adjusting the axial position of the check valve housing with respect to the electromagnetic control valve so as to move the check valve body and release the hydraulic pressure of the cylinder.

  The biasing means is preferably a leaf spring that generates a biasing force by being displaced in the axial direction. The leaf spring is preferably a corrugated leaf spring having a corrugated initial shape with respect to a plane perpendicular to the axial direction.

  With at least one of the above configurations, the check valve constituting the composite control valve is inserted into the guide hole of the check valve housing so that the check valve body stops in one direction by the spring member. The axial position of the stop valve housing is adjusted by the axial biasing means and the axial adjustment means. Adjustment is made so that when the spool of the electromagnetic control valve is in a position within the maximum stroke, the check valve body is moved to the stop position, so that the check valve body is moved when the spool of the electromagnetic control valve protrudes by a predetermined projection amount. This is done so as to release the hydraulic pressure of the cylinder. By this adjusting means, it is possible to absorb variations in the dimensional accuracy of the electromagnetic control valve in the operation of the composite control valve.

  Further, the adjusting means has an adjusting screw that at least partly meshes with a screw portion provided in a holding portion that holds the check valve housing with respect to the electromagnetic control valve, and that has a tip portion that contacts the check valve housing. By adjusting the meshing length of the screw with respect to the holding portion, it is possible to absorb variations in the dimensional accuracy of the electromagnetic control valve.

  In addition, since an intermediate body is provided between the tip of the adjusting screw and the check valve housing, the overall length of the composite control valve can be arbitrarily set regardless of the length of the electromagnetic control valve and the check valve. For example, the total length of the composite control valve can be standardized.

  In addition, the electromagnetic control valve and the check valve are integrally held in the housing by at least one of the above configurations. The check valve constituting the composite control valve is inserted into the guide hole of the check valve housing so that the check valve body is stopped in one direction by the spring member. It is moved and adjusted in the axial direction with respect to the housing by the direction biasing means and the axial direction adjusting means. Adjustment is made so that when the spool of the electromagnetic control valve is in a position within the maximum stroke, the check valve body is moved to the stop position, so that the check valve body is moved when the spool of the electromagnetic control valve protrudes by a predetermined projection amount. This is done so as to release the hydraulic pressure of the cylinder. By this adjusting means, it is possible to absorb variations in the dimensional accuracy of the electromagnetic control valve in the operation of the composite control valve.

  Further, the urging means is a leaf spring that generates an urging force by being displaced in the axial direction. Thereby, compared with a coil spring etc., the hysteresis etc. with respect to an axial displacement are decreased, and the axial direction position of a non-return valve housing can be adjusted accurately.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, a tractor that pulls a tiller will be described as the ground working vehicle. However, the working device that performs work on the ground may be any vehicle that moves up and down using hydraulic pressure. For example, a vehicle having a leveling work machine, a vehicle having a digging work machine, a vehicle having a seedling work machine, a vehicle having a mowing work machine, or the like may be used. In addition, the hydraulic control circuit described below is an example for explanation, and in order to lower the work implement, a composite control valve, that is, an electromagnetic control valve and a reverse that can be pushed open by a spool of the electromagnetic control valve. Any hydraulic control circuit other than the configuration described may be used as long as it is a hydraulic control circuit for using a composite control valve combined with a stop valve.

  FIG. 1 is a diagram illustrating a configuration of a ground work vehicle 10 including a work implement lifting device that uses a composite control valve for lowering a work implement. The ground work vehicle 10 includes a tiller as the work machine 30 and is a vehicle capable of moving the work machine up and down and traveling on the ground surface. The ground work vehicle 10 including the work implement 30 and the work implement lifting / lowering device includes an engine 12 that is used as a traveling drive source of the vehicle, a transmission 14 that transmits engine output to drive wheels, and the engine 12 via a transmission mechanism 16. Although not shown, a hydraulic control circuit that is supplied with hydraulic pressure from the hydraulic pump 18 through a filter 20 and the like, a lifting cylinder 22 included in the hydraulic control circuit, and a work machine 30 are illustrated. A tilting cylinder 24 for controlling the tilt of the working machine, a working machine lifting lever 26 operated by an operator, and a mounting hitch 28 for converting the operations of the lifting cylinder 22 and the tilting cylinder 24 into the lifting and tilting actions of the working machine 30. It is comprised including. In addition, in relation to the raising / lowering cylinder 22, the composite control valve 70 used for control of a lowering valve is also shown in figure. Details of the hydraulic control circuit will be described later.

  The work implement elevating apparatus includes elements necessary for elevating the work implement 30 using the hydraulic pressure of the hydraulic pump 18. In FIG. 1, the hydraulic pump 18, the filter 20, and the elevating cylinder 22 are included. The tilt cylinder 24 and the mounting hitch 28 are shown.

  FIG. 2 is a diagram mainly showing the configuration of the work implement lifting device 11 of the ground work vehicle 10 with the hydraulic control circuit 13 as the center. The work implement lifting device 11 includes a hydraulic control circuit 13 including the hydraulic pump 18, the filter 20, and the composite control valve 70 shown in FIG. 1, tanks 32, 34, and 36 related thereto, the lifting cylinder 22, and the tilting cylinder 24. The mounting hitch 28 is configured.

  Here, the mounting hitch 28 is a connection mechanism of a working machine having a function of converting the linear motion of the lifting cylinder 22 and the tilting cylinder 24 into the lifting motion and the tilting motion of the working machine that is a tiller. Configured. Specifically, two lower links 23 and 25 having tip portions attached to both ends in the width direction of the tiller that is a working machine and the rear end portions of the two lower links are rotatably supported. An attachment hitch 28 is configured including a pivot pin 27 attached to the rear portion of the tractor.

  The elevating cylinder 22 is a hydraulically driven piston / cylinder mechanism that drives the mounting hitch 28 connected to the output end of the piston by moving the piston forward or backward by controlling the hydraulic pressure, and elevating the tiller that is a working machine. It has a function to make it. The control content of the supplied hydraulic pressure will be described later.

  Specifically, as shown in FIG. 2, a kind of lift rod is provided between the pair of left and right lift arms 21a and 21b connected to the output end of the piston and the intermediate portions of the two lower links 23 and 25. When the piston moves forward, the middle part of the two lower links 23, 25 is simultaneously moved upward. When the output end of the piston moves backward, the middle part of the two lower links 23, 25 is simultaneously lowered. Move to. Thereby, the forward / backward movement of the piston is converted into the vertical movement of the tip portions of the two lower links 23 and 25. When the tips of the two lower links 23 and 25 are moved up and down at the same time, both ends in the width direction of the tiller that is a working machine attached to each of the tips are simultaneously moved up and down. Thus, the tiller, which is a working machine, can be raised and lowered by the operation of the lifting cylinder 22.

  The tilt cylinder 24 is also a piston / cylinder mechanism that is hydraulically driven, similar to the lift cylinder 22, and drives the mounting hitch 28 connected to the output end of the piston by moving the piston forward or backward by controlling the hydraulic pressure. It has a function of tilting a tiller that is a working machine along the width direction. The hydraulic pressure is separately supplied to the hydraulic chambers on both sides of the piston. The control content of the supplied hydraulic pressure will be described later.

  Specifically, as shown in FIG. 2, in a kind of lift rod that moves up and down the two lower links 23 and 25, an inclined cylinder 24 is disposed at an intermediate portion of the one side lower link 25. When the piston of the inclined cylinder 24 moves downward, the intermediate portion of the one side lower link 25 is moved downward. When the output end of the piston moves backward, the intermediate portion of the one side lower link 25 is moved upward. Move. As a result, the forward / backward movement of the piston is converted into the vertical movement of the tip of the one side lower link 25. Since the other side lower link 23 is not connected to the inclined cylinder 24, the position thereof does not change. Thereby, only the one side of the tiller which is a working machine attached to the front-end | tip part of the one side lower link 25 goes up and down. In this manner, the tiller that is the working machine can be tilted in the width direction by the operation of the tilt cylinder 24.

  As described with reference to FIG. 1, the hydraulic pump 18 is a fixed displacement gear pump that is operated by the engine 12 via the transmission mechanism 16. As the hydraulic pump 18, a variable displacement pump that generates hydraulic pressure by changing the volume of the hydraulic chamber according to the rotation of the pump shaft, which is a rotating shaft, can be used. For example, a variable displacement axial piston pump having a piston that operates according to the rotation of the pump shaft can be used. Alternatively, a variable displacement radial pump using a rotating ring eccentrically attached to the pump shaft may be used.

  The filter 20 is for removing impurities such as dust in oil that is a medium for transmitting fluid pressure. As the filter 20, a mesh filter having an appropriate roughness can be used.

  The tanks 32, 34, and 36 are oil containers for releasing the oil used for operation and the like in the hydraulic control circuit 13 to the atmosphere. In FIG. 2, in addition to the tank 32 that collects oil to be used again as the hydraulic oil for the hydraulic pump 18, in FIG. The tank 34 used for the purpose, etc., and the tank 36 used for releasing the hydraulic pressure to the atmosphere in the ascending valve 58 and the descending valve 64 system are shown.

  The hydraulic control circuit 13 is a hydraulic circuit that controls the hydraulic pressure supplied to the elevating cylinder 22 and the hydraulic pressure supplied to the tilt cylinder 24 based on the hydraulic pressure supplied from the hydraulic pump 18. Further, the hydraulic control circuit 13 performs control to drain the oil in the elevating cylinder 22 when the hydraulic pressure is not supplied from the hydraulic pump 18 by the function of the composite control valve 70.

  The configuration of the hydraulic control circuit 13 can be broadly divided into a hydraulic control portion supplied to the tilt cylinder 24 and a portion that performs control related to the operation of the lifting cylinder 22. The part regarding the inclination cylinder 24 is demonstrated first, and the part regarding the raising / lowering cylinder 22 is demonstrated next.

  The oil from the hydraulic pump 18 passes through the filter 20 and is supplied to the hydraulic control portion for the tilt cylinder 24 such as the direction control valve 44 through the throttle 42. A flow rate control valve 40 is provided in parallel with the throttle 42, whereby oil having a predetermined constant flow rate is supplied to the tilt cylinder 24, and oil exceeding the constant flow rate is supplied to the lifting cylinder 22. It is distributed to the oil supply path 54. Therefore, the flow control valve 40 and the throttle 42 have a function of distributing oil from the hydraulic pump 18 to oil for the tilt cylinder 24 and oil for the lift cylinder 22.

  The direction control valve 44 is an electromagnetic control valve operated by a solenoid, and two oil supply passages 50 and 52 are respectively connected to the oil from the hydraulic pump 18 via the throttle 42 to the hydraulic chambers on both sides of the piston of the tilt cylinder 24. It has a function to switch to which of the two to be supplied. At this time, the oil supply path on the side where oil is not supplied from the hydraulic pump 18 through the throttle 42 is opened to the tank 32 to the atmosphere. Note that check valves 46 and 48 and appropriate throttles are provided between the direction control valve 44 and the oil supply passages 50 and 52, respectively.

  For example, in FIG. 2, the directional control valve 44 is shown in a neutral state. However, when the directional control valve 44 moves from that state to the right side state, the oil that has passed through the throttle 42 from the hydraulic pump 18 is supplied to the oil supply path 50. At the same time, the oil supply path 52 is opened to the atmosphere toward the tank 32. That is, in FIG. 2, high-pressure oil is supplied to the hydraulic chamber below the piston of the tilt cylinder 24, and at the same time, the hydraulic chamber above the piston of the tilt cylinder 24 is opened to the atmosphere toward the tank 32. As a result, the piston of the tilt cylinder 24 is retracted upward, and the tiller, which is a working machine, tilts so that one side in the width direction is lifted. On the other hand, when the directional control valve 44 moves from the neutral state to the left side state, the oil that has passed through the throttle 42 from the hydraulic pump 18 is supplied to the oil supply path 52, and at the same time, the oil supply path 50 is directed toward the tank 32. Open to the atmosphere. That is, in FIG. 2, high-pressure oil is supplied to the hydraulic chamber above the piston of the tilt cylinder 24, and at the same time, the hydraulic chamber below the piston of the tilt cylinder 24 is opened to the atmosphere toward the tank 32. As a result, the piston of the tilt cylinder 24 moves downward, and the tiller, which is a working machine, tilts so that one side in the width direction is pushed down.

  Thus, by changing the state of the direction control valve 44, it is possible to control the inclination along the width direction of the tiller that is the working machine. In addition, by adjusting and setting the throttle on the oil supply path 50 side and the throttle on the oil supply path 52 side, the operation time for the inclination in one direction and the inclination in the other direction is made substantially the same. be able to.

  Next, the part regarding the raising / lowering cylinder 22 in the hydraulic control circuit 13 is demonstrated. The oil distributed to the oil supply path 54 by the flow control valve 40 is supplied to the two electromagnetic control valves 56, 80, the lift valve 58, and the unload valve 60. The two electromagnetic control valves 56 and 80 each have a function of controlling the pressure oil flowing through the oil supply path 54 and supplying pilot hydraulic pressure to the ascending valve 58 and the descending valve 64.

  The lift valve 58 is a directional control valve that is operated by a pilot hydraulic pressure generated by the electromagnetic control valve 56, and includes an appropriate throttle inside. The lift valve 58 has a function of changing the state of the oil supply path 62 connected to the lift cylinder 22 when the work implement is lifted. For example, in FIG. 2, the lift valve 58 is in a neutral state, shuts off high-pressure oil supplied from the hydraulic pump via the oil supply path 54, and at the same time, an oil supply path 62 connected to the elevating cylinder 22 is connected to the tank 36. A state of being connected to an oil release path 68 that is open to the atmosphere is shown. When moving from the neutral state to the state on the right side in FIG. 2, high-pressure oil supplied from the hydraulic pump via the oil supply path 54 is supplied to the oil supply path 62 via the variable throttle. Accordingly, the pressurized oil is supplied to the elevating cylinder 22 in accordance with the throttle state of the variable throttle, and the piston moves forward, thereby gradually raising the tiller, which is a working machine.

  When the state further moves from the state to the right side, the high-pressure oil supplied from the hydraulic pump via the oil supply path 54 is supplied to the oil supply path 62 via the fixed throttle. Therefore, pressurized oil is supplied to the lifting cylinder 22 and its piston moves forward, thereby raising the tiller, which is a working machine.

  The unload valve 60 is a control valve having a function of holding the oil pressure in the oil supply passage 54 at a predetermined unload pressure. The unload pressure can be set to, for example, about 0.5 MPa. As shown in FIG. 2, the differential pressure, which is the differential pressure between the oil pressure in the oil supply path 62 connected to the elevating cylinder 22 and the oil pressure in the oil supply path 54 to which oil from the hydraulic pump 18 is supplied, is unloaded. The load valve 60 is returned. Therefore, the pressure difference applied before and after the variable throttle or the fixed throttle when oil is supplied to the oil supply passage 62 becomes the unload pressure in the unload valve 60. That is, the pressure difference between the unload pressures is always applied to both ends of the variable throttle or the fixed throttle regardless of the load such as the weight of the tiller that is the working machine.

  The down valve 64 is a directional control valve that is operated by a pilot hydraulic pressure generated by the electromagnetic control valve 80, and includes a proper throttle inside. The lowering valve 64 has a function of changing the state of the oil supply path 62 connected to the elevating cylinder 22 when lowering the work implement. For example, FIG. 2 shows a state in which the lowering valve 64 is in a neutral state and the oil supply path 62 connected to the elevating cylinder 22 is blocked. When moving from the neutral state to the left side state in FIG. 2, the oil supply path 62 connected to the elevating cylinder 22 is connected to an oil release path 68 that is opened to the atmosphere toward the tank 36 via the variable throttle. The Therefore, according to the throttle state of the variable throttle, the oil in the lifting cylinder 22 is drawn into the tank 36 via the oil release path 68, and the piston moves backward due to the weight of the tiller that is the working machine. A tiller gradually descends.

  When the state further moves to the left side, the oil supply path 62 connected to the elevating cylinder 22 is connected to the oil release path 68 via the fixed throttle. Therefore, the oil in the lifting cylinder 22 is drawn into the tank 36 via the oil release path 68, the piston moves backward due to the weight of the tiller that is the working machine, and the tiller that is the working machine descends.

  As described above, the electromagnetic control valve 80 used for the descending valve 64 is an electromagnetic control valve that is operated by the electromagnetic proportional solenoid 74, and is a pilot based on the hydraulic pressure supplied from the hydraulic pump 18 via the oil supply path 54. Hydraulic pressure is generated and supplied to the lowering valve 64 via the oil supply path 66. As shown in FIG. 2, the pilot hydraulic pressure is returned to the spring receiving piston of the unload valve 60 as it is, so that the required pressure for the descending electromagnetic control valve 80 can be increased. Therefore, when the load such as the weight of the tiller that is the working machine is large, the working machine descends immediately, and when the load is small, the working machine descends slowly.

  The non-return control valve 90 provided between the oil supply path 62 connected to the lifting cylinder and the tank 36 has an oil supply path when the hydraulic pump 18 does not operate and no hydraulic pressure is supplied to the electromagnetic control valve 80. 62 has a function of connecting to an oil release path 68 that opens to the atmosphere toward the tank 36. FIG. 2 shows a state in which the oil supply path 62 and the tank 36 are blocked as a neutral state of the check control valve 90. When hydraulic pressure is not supplied to the electromagnetic control valve 80, the check control valve 90 moves from the neutral state to the lower state in FIG. 2 in conjunction with the movement of the solenoid 74 of the electromagnetic control valve 80, as will be described later. There, an oil supply path 62 connected to the lift cylinder 22 is connected to an oil release path 68 that is open to the atmosphere toward the tank 36, and the oil in the lift cylinder 22 is drained.

  Thus, by combining the solenoid control valve 80 driven by the solenoid and the check control valve 90 driven by the solenoid, the engine start key is set to the accessory position even when the hydraulic pressure is not supplied. Thus, when the work implement elevating lever 21 is placed in the lowered position, the oil in the elevating cylinder 22 can be drained, and thereby the tiller as the work implement can be lowered. Thus, the electromagnetic control valve 80 and the check control valve 90 can be combined to form one composite control valve 70.

  FIG. 3 is a partial cross-sectional view of the composite control valve 70 in which the electromagnetic control valve 80 and the check control valve 90 are combined. Elements similar to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The composite control valve 70 includes an electromagnetic control valve 80 that is operated and controlled by a solenoid 74, a check control valve 90 that is arranged coaxially with the electromagnetic control valve 80, and between the electromagnetic control valve 80 and the check control valve 90. An adjustment screw 94 for adjusting the axial positional relationship is included. These elements are respectively held in the casing 72.

  The casing 72 is a member having a function of holding each element of the composite control valve 70. When combining the composite control valve 70 as one independent product, the housing 72 is a member that forms the outer shape of the product. Further, when the composite control valve 70 is a product integrated with other elements, for example, other elements constituting the hydraulic control circuit 13, a part of the combined product is used as the casing 72 of the composite control valve 70. it can. Therefore, the casing 72 is a holding member having a function of holding each element of the composite control valve 70 in a broad sense. The structure of the housing 72 will be described in detail later in connection with the adjustment screw 94.

  The solenoid 74 is an electromagnetic actuator that includes a moving body that is at least partially made of a magnetic material, and a coil that is disposed around the moving body. Has a function of moving and driving in the axial direction. The solenoid 74 is fixedly attached to the casing 72 using an appropriate fixing means.

  The electromagnetic control valve 80 is a so-called sleeve-spool type fluid control valve that includes a spool 78 having a spool shape and a sleeve 76 that holds the outer shape of the spool 78. The spool 78 is a plurality of stepped shaft members having a large-diameter portion called a land and a small-diameter portion called a stem that connects adjacent lands. The spool 78 is connected to the moving body of the solenoid 74. Alternatively, it may be a part of the moving body of the solenoid 74. The sleeve 76 is a cylindrical member that has an inner wall that holds the outer shape of the land of the spool 78 and that is provided with three ports through which oil enters and exits toward the inner wall. The electromagnetic control valve 80 is positioned, fixed and held with respect to the casing 72. For example, the inner wall shape of the casing 72 corresponds to the outer shape of the sleeve 76, and is positioned by inserting the electromagnetic control valve 80 into the casing 72 according to the inner wall shape, and is fixed using an appropriate fixing member. And can be held.

  The three ports provided in the sleeve 76 are connected to the oil supply passage 54 described in FIG. 2 from the right side in FIG. This is a secondary port to which pilot oil pressure generated by the cooperation of the spool 78 is output, a tank port connected to the oil release path 68 and opened to the atmosphere toward the tank 36.

  As shown in FIG. 3, the outer diameters of the lands on both sides of the stem of the spool corresponding to the secondary port connected to the oil supply path 66 are different, and accordingly, the pressure receiving area for receiving the hydraulic pressure is set differently. ing. That is, the pressure receiving area of the land on the tank port side connected to the oil release path 68 is larger than the pressure receiving area of the land on the primary port side connected to the oil supply path 54.

  Here, before explaining the configuration of the check control valve 90 and the like, the operation of the electromagnetic control valve 80 will be explained. FIG. 3 is a view showing a neutral state of the electromagnetic control valve 80. In this state, of the lands on both sides of the spool corresponding to the position of the secondary port connected to the oil supply path 66, the primary port and 2 are connected by the land on the primary port side connected to the oil supply path 54. Between the secondary port and the tank port, the secondary port and the tank port are communicated with each other by the tank port side land connected to the oil release path 68. That is, the secondary port is opened to the atmosphere, and no pilot hydraulic pressure is generated in the oil supply path 66.

  Here, when the spool 78 is moved to the right in FIG. 3 by the solenoid 74, the positional relationship between the outer periphery of the land and the inner wall of the sleeve changes, and the primary port and the secondary port communicate with each other. The secondary port and the tank port are blocked. As a result, the oil from the oil supply path 54 connected to the primary port flows into the secondary port, and a pilot hydraulic pressure corresponding to the amount of movement of the spool 78 appears.

  At this time, as described above, the pressure receiving area of the land on the tank port side connected to the oil release path 68 is larger than the pressure receiving area of the land on the primary port side connected to the oil supply path 54. Since it is large, the spool 78 is pushed back to the tank port side, that is, the left side in FIG. 3 by the pilot hydraulic pressure of the secondary port. Therefore, in a normal case where hydraulic pressure is supplied from the oil supply path 54 to the primary port, the spool 78 is not connected between the secondary port and the tank port regardless of the drive of the solenoid 74. In FIG. 3, it moves to the right, but does not move further to the right. That is, the spool 78 can move to the right only up to the maximum stroke determined by the relative positional relationship with the sleeve 76.

  As described above, when the input hydraulic pressure is supplied from the hydraulic pump 18 to the electromagnetic control valve 80 via the oil supply path 54, the hydraulic pressure is reduced by the cooperation of the spool 78 and the sleeve 76 to reduce the secondary port. Can be output as a pilot hydraulic pressure to the oil supply passage 66 and supplied to the lowering valve.

  On the other hand, when not in use, such as when the hydraulic pump 18 is stopped, the input hydraulic pressure is not supplied to the electromagnetic control valve 80 via the oil supply path 54, so that the spool 78 is driven to move rightward in FIG. Even so, the pilot hydraulic pressure does not appear in the secondary port, and therefore, the spool 78 is not pushed back to the tank port side, that is, the left side in FIG. At this time, the spool is moved and driven as it is by the solenoid 74, and moves to the right in FIG. 3 beyond the maximum stroke when the input hydraulic pressure is present.

  That is, when the input hydraulic pressure is not supplied to the electromagnetic control valve 80 via the oil supply path 54, the tip of the spool 78 is further protruded from the maximum stroke when the input hydraulic pressure is present. The protrusion amount is determined by a control signal given to the solenoid 74. In this sense, if the control signal is determined, the tip of the spool 78 is protruded by a predetermined protrusion amount corresponding to the control signal. The protruding tip end of the spool 78 is received by the tip end of the shaft portion of the check valve body 84 of the check control valve 90, as will be described later.

  Next, the check control valve 90 will be described. The check control valve 90 is configured as a check valve that takes a holding position for holding the hydraulic pressure of the elevating cylinder and a hydraulic pressure releasing position for releasing the hydraulic pressure of the cylinder. Specifically, it includes a check valve housing 82, a check valve body 84, and a spring member 86 that applies a pressing force to the check valve body 84. The holding position can be obtained by the spring member 86 pressing the check valve body 84 against the check valve housing 82, and the oil draining position can be obtained by the spool 78 of the electromagnetic control valve 80 moving the check valve body 84. Can be taken at.

  The check valve housing 82 is a cylindrical member having a guide hole coaxial with the electromagnetic control valve 80 and is held by the casing 72 so as to be movable in the axial direction as will be described later. The coaxial with the electromagnetic control valve 80 means that the central axis of the spool 78 that is the moving body of the electromagnetic control valve 80 and the central axis of the guide hole of the check valve housing 82 are coaxial, that is, substantially aligned. Means.

  The check valve body 84 is a member that is slidably inserted into the guide hole of the check valve housing 82 and has a stop position in one direction along the axial direction by the action of the spring member 86. As shown in FIG. 3, the check valve body 84 has a flange portion and a shaft portion, and a thin shaft diameter is formed between the shaft portion and the flange portion. The thin shaft diameter portion corresponds to the tank port connected to the oil release path 68 and serves as a flow path when oil in the lifting cylinder is released. By reducing the shaft diameter, the resistance when oil escapes can be reduced. As described above, the tip end of the shaft portion has a function of receiving the tip end of the spool 78 protruding when the input hydraulic pressure is not supplied to the electromagnetic control valve 80.

  Corresponding to the shape of the check valve body 84, the check valve housing 82 has a shoulder portion that receives the collar portion. The shoulder portion is a stepped portion of the guide hole. In the case of FIG. 3, the end surface of the check valve housing 82 is used as the shoulder portion. The flange portion of the check valve body 84 receives the pressing force of the spring member 86 and tries to move in one direction along the axial direction, but is stopped by this shoulder portion and becomes a stop position.

  A tank port connected to the oil release path 68 is provided toward the inner wall of the check valve housing 82 corresponding to the thin shaft diameter portion of the check valve body 84.

  Further, the length of the guide hole of the check valve housing 82 is set according to the length of the shaft portion of the check valve body 84. The length of the guide hole, in particular, the length of the guide hole that guides the thicker shaft diameter portion of the check valve body 84 with a small shaft diameter suppresses oil leakage along the axial direction of the check valve body 84. In order to do so, an appropriate length is required. Further, since the tip of the shaft portion of the check valve body 84 has a function of receiving the movement of the spool 78 of the electromagnetic control valve 80, it is necessary to sufficiently protrude from the guide hole. That is, the total length of the guide hole in the axial direction is shorter than the total length of the check valve body 84, and the length of the portion that guides the thick shaft portion of the check valve body 84 is an appropriate length in consideration of oil leakage. Is done.

  The spring member 86 is a pressing spring having a function of holding the hydraulic pressure of the lifting cylinder by pressing the check valve body 84 toward the stop position against the hydraulic pressure of the lifting cylinder. As shown in FIG. 3, the spring member 86 is disposed outside the shoulder portion of the check valve housing 82 and applies a pressing force to the collar portion of the check valve body 84 that is stopped by the shoulder portion. The direction of the pressing force is a direction in which the check valve body 84 is moved to the electromagnetic control valve 80 side. Therefore, the shoulder portion has a receiving surface that faces the spring member 86 so as to receive the pressing force.

  Since the spring member 86 is thus arranged outside the check valve housing 82, it is actually arranged in a storage space provided in the housing 72. An intermediate body 96 provided between the spring member 86 and the adjustment screw 94 is also disposed in the storage space. An actuator port connected to the oil supply path 62 is provided toward the storage space. Since the oil supply path 62 is connected to the elevating cylinder as described with reference to FIG. 2, the hydraulic pressure of the elevating cylinder is supplied to the actuator port. The storage space is a space defined by the inner wall of the housing 72 and the shoulder side portion of the check valve housing 82, and oil leaks except for this actuator port and the guide hole in the shoulder side portion. There is no structure.

  Here, the operation of the check control valve 90 will be described. When the input hydraulic pressure is supplied to the electromagnetic control valve 80, the tip of the spool 78 operates within the range of the maximum stroke, so that the tip of the check valve body 84 contacts the tip of the spool 78 at this maximum stroke. By not doing so, the operation of the check control valve 90 can be prevented from being affected by the movement of the spool 78. Thus, when the axial positional relationship between the electromagnetic control valve 80 and the check control valve 90 is set, when the electromagnetic control valve 80 is in a normal operation, the spring member 86 in the check control valve 90 is The buttocks of the body 84 are pressed against the shoulder of the check valve housing 82 to obtain a stop position. Therefore, the hydraulic pressure of the elevating cylinder supplied from the oil supply path 62 to the storage space is maintained as it is without leaking.

  On the other hand, when the input hydraulic pressure is not supplied to the electromagnetic control valve 80, the spool 78 protrudes a predetermined amount beyond the maximum stroke by driving the solenoid 74. At this time, the tip of the check valve body 84 is the tip of the spool 78. The oil can be drained by the movement of the spool 78. That is, in this case, as the spool 78 moves, the check valve body 84 moves against the hydraulic pressure of the spring member 86 and the lifting cylinder, and the shoulder of the check valve housing 82 and the check valve body 84 are moved. Take the oil drain position that creates a gap with the heel. In the oil drain position, the oil in the storage space passes through the gap between the shoulder portion and the collar portion, flows through the tank port to the oil release passage 68, and the oil in the lift cylinder is drained. Thus, when the input hydraulic pressure is not supplied to the electromagnetic control valve 80, the check control valve 90 can drain the oil in the lifting cylinder by the cooperative action of the solenoid 74 and the electromagnetic control valve 80.

  Next, adjustment of the positional relationship between the electromagnetic control valve 80 and the check control valve 90 in the axial direction will be described. First, the structure of the housing 72 related to the positional relationship adjustment will be described.

  As shown in FIG. 3, the housing 72 holds the electromagnetic control valve 80 and the check control valve 90 so that they are coaxial. Here, as described above, the electromagnetic control valve 80 is positioned with respect to the casing 72, and its axial position is fixed by the fixing means. On the other hand, the check control valve 90 is held such that the check valve housing 82 is movable in the axial direction with respect to the housing 72. That is, the inner wall shape of the casing 72 corresponding to the outer shape of the check valve housing 82 is slightly larger than the outer diameter of the check valve housing 82 in the radial direction and sufficiently longer than the entire length of the check valve housing 82 in the axial direction. . Therefore, the check valve housing 82 is held by the casing 72 so as to be slidable in the axial direction.

  The spring member 88 is an urging means having a function of applying an urging force in the axial direction against the pressing force of the spring member 86 to the check valve housing 82. Specifically, it is possible to use a ring-shaped leaf spring that can give an initial displacement to a metal ring member having a hole in the center and generate an urging force in the axial direction. For example, a corrugated ring-shaped leaf spring in which a corrugated initial shape is given to the ring portion can be used. In this case, the shaft portion of the check valve body 84 passes through the center hole of the ring-shaped leaf spring, and the ring portion is received by an appropriate receiving surface provided in the housing 72, so that A direction biasing force can be applied. Of course, spring members having other configurations can be used.

  The mounting nut 92, the adjusting screw 94, and the intermediate body 96 together with the spring member 88 constitute an adjusting means for adjusting the axial positional relationship between the electromagnetic control valve 80 and the check control valve 90.

  The mounting nut 92 has a female thread portion that meshes with the adjustment screw 94 along the central axis, a male thread portion at a part of the outer periphery, and a guide portion that holds the intermediate body 96 so as to be movable in the axial direction. It is a member. The mounting nut 92 is an adjusting member that is used when it is difficult to provide a female thread portion that meshes with the adjusting screw 94 in the casing 72 or when it is desired to standardize the overall axial length of the composite control valve 70 regardless of its specifications. . Therefore, in the case of providing a female thread portion in which the adjustment screw 94 meshes with the housing 72, the mounting nut may be omitted by configuring the function of the mounting nut as a part of the housing 72.

  The adjustment screw 94 is a bolt member having a male screw portion that meshes with a female screw portion provided on the mounting nut 92. The intermediate body 96 is a member disposed between the spring member 86 and the tip of the adjustment screw 94 and has a bottomed hole for holding the spring member 86 at the tip. The intermediate body 96 is an adjustment member used when it is desired to standardize the dimensions of the composite control valve 70 regardless of differences in product specifications or components. For example, when it is desired to standardize the position of each port of the check control valve 90, when it is desired to standardize the positional relationship between the ports in the composite control valve 70, or when it is desired to standardize the total axial length of the check control valve 90 For example, an intermediate body 96 having an appropriate axial length can be used in accordance with the dimensions of the constituent elements.

  Adjustment of the positional relationship in the axial direction between the electromagnetic control valve 80 and the check control valve 90, specifically, the tip of the spool 78 of the electromagnetic control valve 80 and the tip of the check valve body 84 of the check control valve 90 The reason why adjustment of the axial clearance ΔS between them is necessary is due to variations in dimensional accuracy of the solenoid 74 and the electromagnetic control valve 80. Here, the position of the tip end of the spool 78 of the electromagnetic control valve 80, particularly the position of the maximum stroke thereof, is the size of the land and stem arrangement positions of the spool 78, the size of the inner wall shape of the sleeve 76 corresponding thereto, and the solenoid 74. It is determined by the arrangement position of the coil and the dimensions of the moving body. Each of these dimensions has a processing error and an assembly error, and the maximum stroke position of the spool 78 of the electromagnetic control valve 80 is determined by the accumulation thereof. Therefore, if the electromagnetic control valve 80 is different, the maximum stroke position of the spool 78 is also different. In an actual example, the axial error of the maximum stroke position of the spool 78 between the many electromagnetic control valves 80 may be about 1 mm or more.

  Along with this, an error occurs in the protruding position of the spool 78 when the input hydraulic pressure is not supplied to the electromagnetic control valve 80. The amount of protrusion from the maximum stroke position also causes an error due to variations in the reproducibility of the drive performance of the solenoid 74. When the error of the maximum stroke position and the variation of the protrusion amount are combined, the error of the operating position of the spool 78 when the input hydraulic pressure is not supplied to the electromagnetic control valve 80 may be about 1 mm to 2 mm.

  On the other hand, the function of the check control valve 90 as a check valve is that the lifting cylinder can be drained even if the check valve body 84 has a very small axial displacement, for example, 0.1 mm or less. Therefore, if the electromagnetic control valve 80 and the check control valve 90 are simply attached to the housing 72 without adjusting the positional relationship in the axial direction, the tip of the spool 78 of the electromagnetic control valve 80 and the check control valve The axial clearance ΔS between the 90 check valve bodies 84 and the tip of the check valve body 84 is too large or too small. FIG. 4 is a diagram illustrating a state in which the spool 78 of the electromagnetic control valve 80 contacts the tip of the check valve body 84 of the check control valve 90 when the spool 78 is in the maximum stroke state. In this case, even if the input hydraulic pressure is supplied to the electromagnetic control valve 80 and the normal pilot hydraulic pressure is generated, the tip of the check valve body 84 moves in the check control valve 90, and the lifting cylinder A malfunction occurs in which oil is drained.

  Therefore, the positional relationship in the axial direction between the electromagnetic control valve 80 and the check control valve 90 is adjusted using the adjusting screw 94. Specifically, the axial clearance between the tip of the spool 78 of the electromagnetic control valve 80 at the maximum stroke position and the tip of the check control valve 90 when the check valve body 84 is at the stop position. The screwing amount of the adjusting screw 94 is adjusted so that ΔS becomes a predetermined set value. The predetermined set value of the axial clearance ΔS is set to a value smaller than a predetermined protruding amount that the spool 78 further protrudes from the maximum stroke position by driving by the solenoid 74 when the input hydraulic pressure is not supplied to the electromagnetic control valve 80. it can. For example, when the predetermined protrusion amount is about 1.8 mm, the set value of the axial clearance ΔS by adjusting the adjustment screw 94 can be about 1.5 mm.

  In the adjustment of the axial clearance ΔS, when actual clearance measurement is difficult, the combined control valve 70 to be adjusted can be actually operated to determine the screwing amount of the adjusting screw 94. The procedure can be performed as follows.

  First, the screwing of the adjusting screw 94 is sufficiently returned in the reverse direction, and ΔS is set to a sufficiently large amount (returning step). Next, the input hydraulic pressure is supplied to the primary port of the electromagnetic control valve 80. The input hydraulic pressure is preferably equal to that at the time of actual operation. Further, an appropriate hydraulic pressure is supplied to the actuator port of the check control valve 90. This hydraulic pressure is also preferably equal to that at the time of actual operation (initial setting step). In this state, the solenoid 74 is driven to set the spool 78 to the position of the maximum stroke, and the position of the spool 78 is held there (maximum stroke setting step). Here, while monitoring the state of the tank port of the check control valve 90, the adjustment screw 94 is gradually screwed in until the oil comes out into the tank port, and the screwing is stopped in that state (oil missing setting step). Then, the adjustment screw 94 is screwed back by a length corresponding to a preset value of ΔS (adjustment process). For example, in the above example, when the set value of ΔS is about 1.5 mm and the screw pitch of the adjusting screw 94 is 3 mm, the screwing amount is returned by about a half turn. Thereby, the positional relationship of the axial direction between the electromagnetic control valve 80 and the non-return control valve 90 can be adjusted appropriately.

  FIG. 5 is a diagram showing a state in which the solenoid 74 is driven when the input hydraulic pressure is not supplied to the electromagnetic control valve 80 using the composite control valve 70 that has been appropriately adjusted. Here, the axial clearance ΔS is adjusted to about 1.5 mm, and the spool 78 of the electromagnetic control valve 80 protrudes about 2 mm by driving the solenoid 74, so that the tip of the spool 78 is the check valve of the check control valve 90. The tip of the body 84 is pushed to create a gap between the shoulder portion of the check valve housing 82 and the collar portion of the check valve body 84 against the hydraulic pressure of the spring member 86 and the lifting cylinder. As a result, the oil in the lifting cylinder is drained from the tank port to the oil release path 68. As described above, by performing appropriate adjustment, it is possible to absorb variations in dimensional accuracy, assembly accuracy, and the like of the solenoid 74, the electromagnetic control valve 80, and the like, and to ensure that the composite control valve 70 operates normally.

  FIG. 6 is a view showing a composite control valve 100 configured by omitting the mounting nut and the intermediate body. Elements similar to those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted. Here, an adjustment screw 98 having a male screw portion that at least partially meshes with the female screw portion provided in the housing 72 is used. A bottomed hole for holding the spring member 86 is provided at the tip of the adjustment screw 98. In this way, the tip of the adjustment screw 98 directly contacts the spring member 86 that is a component of the check control valve 90, and the adjustment screw 98 is screwed into the casing 72, whereby the check control valve 90 is axially moved. Can be moved to. The adjustment method of the axial clearance ΔS using the adjustment screw 98 is the same as that described with reference to FIG.

In embodiment which concerns on this invention, it is a figure which shows the structure of the ground work vehicle provided with the working machine raising / lowering apparatus which uses a composite control valve for the descent | fall of a working machine. In embodiment which concerns on this invention, it is a figure which mainly shows the structure of the working machine raising / lowering apparatus of a ground work vehicle centering around a hydraulic control circuit. In embodiment which concerns on this invention, it is a fragmentary sectional view of a composite control valve. As a part of the description of the embodiment according to the present invention, when the sleeve of the electromagnetic control valve is in the maximum stroke state, it is a diagram showing a state in which the tip of the check valve body of the control valve comes into contact. In embodiment which concerns on this invention, it is a figure which shows a mode when a solenoid is driven when input hydraulic_pressure | hydraulic is not supplied to an electromagnetic control valve using the composite control valve by which appropriate adjustment was performed. In embodiment which concerns on this invention, it is a figure which shows the composite control valve provided with another adjustment means.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Ground work vehicle, 11 Work implement lifting device, 12 Engine, 13 Hydraulic control circuit, 14 Transmission, 16 Transmission mechanism, 18 Hydraulic pump, 20 Filter, 21a, 21b Lift arm, 22 Lifting cylinder, 23, 25 Lower link, 24 Inclined cylinder, 26 Working machine lifting lever, 27 Axle support pin, 28 Mounting hitch, 30 Working machine, 32, 34, 36 Tank, 40 Flow control valve, 42 Restrictor, 44 Directional control valve, 46, 48 Check valve, 50 , 52, 54, 62, 66 Oil supply path, 56, 80 Electromagnetic control valve, 58 Lift valve, 60 Unload valve, 64 Down valve, 68 Oil release path, 70, 100 Combined control valve, 72 Housing, 74 Solenoid 76 sleeve, 78 spool, 82 check valve housing, 84 check valve body, 86 spring member, 88 spring member, 90 check valve, 92 mounting nut, 94, 98 adjusting screw, 96 intermediate.

Claims (6)

A lowering valve provided in a passage for returning hydraulic cylinder oil for lifting and lowering the work implement to the tank;
A composite control valve for controlling the operation of the down valve;
With
The composite control valve
The spool is driven in the axial direction by a solenoid, and when there is an input hydraulic pressure, the hydraulic pressure is reduced by the cooperation of the spool and the sleeve and supplied to the lowering valve. An electromagnetic control valve that protrudes with a predetermined protrusion amount further than the maximum stroke when,
A check valve that is arranged coaxially with the electromagnetic control valve and takes a holding position for holding the hydraulic pressure of the cylinder and a hydraulic pressure releasing position for releasing the hydraulic pressure of the cylinder;
Including
Check valve
A check valve housing having a guide hole coaxial with the electromagnetic control valve;
A check valve body that is slidably inserted into the guide hole of the check valve housing and has a stop position in one direction along the axial direction;
A spring member that holds the hydraulic pressure of the cylinder by pressing the check valve body against the hydraulic pressure of the cylinder toward the stop position;
An urging means for applying an urging force in the axial direction against the pressing force of the spring member to the check valve housing;
When the spool of the electromagnetic control valve is in the position within the maximum stroke, the check valve body is moved to the stop position. Adjusting means for adjusting the axial position of the check valve housing with respect to the electromagnetic control valve so as to release the hydraulic pressure of
A working machine lifting and lowering device for a ground working vehicle. The work machine lifting device for a ground working vehicle according to claim 1,
Adjustment means
A holding portion for holding the check valve housing with respect to the electromagnetic control valve;
An adjustment screw that at least partly meshes with a screw part provided in the holding part and whose tip part contacts the check valve housing;
A working machine lifting and lowering device for a ground working vehicle. The work machine lifting device for a ground working vehicle according to claim 1,
Adjustment means
A holding portion for holding the check valve housing with respect to the electromagnetic control valve;
An adjustment screw that at least partly meshes with a screw part provided in the holding part, and a tip part of which comes into contact with the check valve housing via an intermediate body;
A working machine lifting and lowering device for a ground working vehicle. A lowering valve provided in a passage for returning hydraulic cylinder oil for lifting and lowering the work implement to the tank;
A composite control valve that controls the operation of the down valve;
With
The composite control valve
The spool is driven in the axial direction by a solenoid, and when there is an input hydraulic pressure, the hydraulic pressure is reduced by the cooperation of the spool and the sleeve and supplied to the lowering valve. When there is no input hydraulic pressure, the tip of the spool has the input hydraulic pressure An electromagnetic control valve that protrudes with a predetermined protrusion amount further than the maximum stroke when,
A check valve that is arranged coaxially with the electromagnetic control valve and takes a holding position for holding the hydraulic pressure of the cylinder and a hydraulic pressure releasing position for releasing the hydraulic pressure of the cylinder;
A housing that integrally holds the electromagnetic control valve and the check valve coaxially; and
Including
The check valve
A check valve housing having a guide hole coaxial with the electromagnetic control valve and movable in the axial direction with respect to the housing;
A check valve body that is slidably inserted into the guide hole of the check valve housing and has a stop position in one direction along the axial direction;
A spring member that holds the hydraulic pressure of the cylinder by pressing the check valve body against the hydraulic pressure of the cylinder toward the stop position;
An urging means for applying an urging force in the axial direction against the pressing force of the spring member to the check valve housing;
When the spool of the electromagnetic control valve protrudes by a predetermined protruding amount so that the check valve body is stopped when the spool of the electromagnetic control valve is in a position within the maximum stroke, the check valve is Adjusting means for adjusting the axial position of the check valve housing relative to the electromagnetic control valve so as to move the body and release the hydraulic pressure of the cylinder;
A working machine lifting and lowering device for a ground working vehicle. In the working machine raising / lowering device of the ground work vehicle of any one of Claims 1-4,
The working machine lifting device for a ground working vehicle, wherein the biasing means is a leaf spring that is displaced in the axial direction to generate a biasing force. The work implement lifting device for a ground working vehicle according to claim 5,
The working machine lifting device for a ground working vehicle, wherein the leaf spring is a corrugated leaf spring having a corrugated initial shape with respect to a plane perpendicular to the axial direction.

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