JP2017120109A - Lift control device for work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lift control device capable of preventing a work machine from being unexpectedly lowered since the work machine is apt to be lowered naturally as a stop valve is left unclosed when the work machine is placed at a lifted position.SOLUTION: A lift control device for a work machine is composed of: a lift cylinder; a direction control valve for controlling supply and discharge of pressure oil to and from the lift cylinder; a valve case which has the direction control valve incorporated and comprises an opening part as a pump port, a tank port and a cylinder port; a manifold interposed between the cylinder port of the valve case and the hydraulic lift cylinder; and an electromagnetic stop valve mounted on the manifold. The manifold has a pump tank-side oil passage and a cylinder-side oil passage formed inside. The manifold is mounted removably on the valve case by connecting a part where an end of the pump tank-side oil passage is open to the opening part as the cylinder port of the valve case.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lifting control device for a working machine equipped in a riding rice transplanter or the like.

  Conventionally, a riding rice transplanter is composed of a vehicle body and a work machine (planting part) mounted on the rear part of the vehicle. The work machine is mounted on a seedling stand, a planting claw, and a vehicle. A planting transmission or the like for transmitting the output of the engine to a seedling stand or a planting claw is provided. A link mechanism pivotally supported so as to be pivotable up and down is provided at the rear part of the vehicle, and the work implement is mounted on the vehicle so as to be able to be moved up and down via the link mechanism.

  The link mechanism is rotated up and down by the movement of the piston of the lift cylinder (that is, the expansion and contraction of the piston rod), and a hydraulic circuit as disclosed in Patent Document 1 is to control the operation of the piston of the hydraulic cylinder. The system is configured. This hydraulic circuit system is a directional control valve for selecting one of three setting states: oil supply to the lift cylinder, oil discharge from the lift cylinder, and oil supply / discharge stop in the lift cylinder. (Spool valve).

Japanese Utility Model Publication No. 62-198907

  This directional control valve is roughly divided into a lift position for supplying oil to the lift cylinder to lift and lift the lift arm, a drop position for discharging oil from the lift cylinder and lowering the lift arm, and a lift cylinder. The supply of oil to the cylinder and the discharge of oil from the lift cylinder are stopped to switch to the neutral position where the lift arm is stopped, and the direction control valve is biased to the lowered position. A manually operated stop valve is provided in the oil passage between the direction control valve and the lift cylinder. For example, the work machine is raised to put the riding rice transplanter into the barn, and the direction control is performed in the raised state. By setting the valve to the neutral position, the work implement maintains its position. When storing in the barn for a long time until the end of the rice transplanting operation, the stop valve is manually closed to ensure that the work equipment stopped in the raised state is securely held in that position. Yes. However, since this stop valve is manually operated, it is easy to forget to close the stop valve after it has been raised and the directional control valve is in the neutral position. If the oil that is to be closed between the directional control valve is under pressure due to the weight of the work implement, the oil leaks from the minute gap between the directional control valve and the valve case to the tank port side. The work machine tends to descend. In particular, when a heavy load is applied to the work implement, such as when a heavy load is applied, the work implement is likely to be naturally lowered when the stop valve is forgotten to be closed.

  In order to solve the above-described problem, the lifting control device for a working machine according to the present invention is a hydraulic lift cylinder for lifting a working machine, and supplies hydraulic oil when raising the working machine and lowers the working machine. A configuration that discharges pressure oil, a direction control valve for controlling supply / discharge of pressure oil in the hydraulic lift cylinder, and a valve case that includes the direction control valve, and includes a pump port and a tank port And a cylinder port, a manifold interposed between the cylinder port of the valve case and the hydraulic lift cylinder, and an electromagnetic stop valve mounted on the manifold. The manifold forms a pump / tank side oil passage and a cylinder side oil passage inside, and connects a portion where an end of the pump / tank side oil passage opens to the cylinder port of the valve case. The cylinder is detachably attached to the case, and the opening end of the cylinder side oil passage in the manifold can be connected to the hydraulic lift cylinder.

  The electromagnetic stop valve functions as a check valve that allows only the flow of oil from the pump / tank side oil passage to the cylinder side oil passage of the manifold when the solenoid is not excited. Thus, the valve is opened so that oil can flow in both directions between the pump / tank side oil passage and the cylinder side oil passage of the manifold.

  Further, the directional control valve includes a raised position for supplying pressure oil to the hydraulic lift cylinder, a lowered position for discharging pressure oil from the hydraulic lift cylinder, and supply of pressure oil to the hydraulic lift cylinder. It is configured to be set at any neutral position for stopping discharge, and the solenoid of the electromagnetic stop valve is controlled so that it is excited only when the direction control valve is set at the lowered position. It is linked to the valve operating tool.

  By simply detachably attaching an electromagnetic stop valve that can be automatically controlled via a manifold to a valve case equipped with a directional control valve for controlling the hydraulic oil supply to the hydraulic lift cylinder for lifting and lowering the work implement. A lifting / lowering control device for a working machine that can reliably prevent the unexpected lowering of the working machine when set to the stop state can be easily configured. In addition, the cylinder port of the valve case is a part that was conventionally used to mount a manually operated stop valve, so the electromagnetic stop valve has a manifold that can be connected to this part, making it modular. It is not necessary to equip the valve case with an electromagnetic stop valve, and it is possible to configure a lifting control device for a work machine at a low cost. In addition to the electromagnetic stop valve, a conventional stop valve is installed, and a conventional work machine is installed. It can also be easily changed to the lifting control device. Thus, the raising / lowering control apparatus of the working machine excellent in cost performance can be provided.

  In addition, the electromagnetic stop valve is configured to function as a check valve that permits only the flow of oil from the pump / tank side oil passage to the cylinder side oil passage in the manifold in a non-excited state. If the non-excited state is utilized, it can function as a stop valve that reliably stops the flow of oil from the hydraulic lift cylinder to the direction control valve in a state where the lifting and lowering of the work implement is stopped.

  The solenoid of the electromagnetic stop valve is energized only when the direction control valve is in the lowered position. When the direction control valve is in the neutral position to stop the lifting and lowering of the work implement, the solenoid is not excited. Thus, the electromagnetic stop valve automatically functions as a stop valve as described above, and it is possible to reliably prevent oil leakage from the hydraulic lift cylinder to the direction control valve and prevent the work machine from being unexpectedly lowered. This excitation is performed only when the directional control valve is moved to the lowered position, so that power consumption can be suppressed. Also in this aspect, it is possible to provide a lifting / lowering control device for a work machine having excellent cost performance.

It is a hydraulic circuit diagram provided with the valve apparatus which concerns on this invention. It is a perspective view of the valve device. It is a top view of the said valve apparatus. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. It is front sectional drawing of a stop valve. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 4. It is principal part sectional drawing of the electromagnetic stop valve in the valve closing state by which a solenoid is not excited. It is principal part sectional drawing of the electromagnetic stop valve in the valve opening state by which a solenoid is not excited. It is principal part sectional drawing of the electromagnetic stop valve in the valve opening start state which excited the solenoid. It is principal part sectional drawing of the electromagnetic stop valve in the complete valve opening state which excited the solenoid.

  With reference to FIG. 1, the structure of a hydraulic circuit for work implement lifting control having a valve device 10 according to the present invention will be described. An unillustrated riding rice transplanter is provided with a lift arm 1 for raising and lowering a work implement pivotably supported by a pivot shaft 1a. The lift arm 1 has a tip of a piston rod 3 of a lift cylinder 2. Are pivoted. The lift cylinder 2 is a single-acting hydraulic cylinder, and when oil is supplied to the oil chamber 2a of the lift cylinder 2, the piston rod 3 extends to rotate the lift arm 1 upward, and the working machine (seeding platform) When the oil is removed from the oil chamber 2a, the piston rod 3 contracts and the lift arm 1 is rotated downward to lower the work implement.

  In the case of a rice transplanter, operating tools such as a lever for raising and lowering the working machine are arranged in the vicinity of the driver's seat, and by operating this operating tool to raise the working machine during headland turning and traveling on the road The expansion and contraction of the piston rod 3 of the lift cylinder 2 (up and down rotation of the lift arm 1) is controlled. In addition, during work travel, the expansion and contraction of the piston rod 3 of the lift cylinder 2 is automatically controlled according to the ground pressure of the float mounted on the work machine for the purpose of adjusting the height of the work machine. Sometimes.

  The valve device 10 as the lifting control device of the working machine according to the present invention is a lift cylinder for the oil discharged from the hydraulic pump P driven by the engine E of the rice transplanter for the lifting control of the working machine. The supply to the second oil chamber 2a and the discharge from the oil chamber 2a are controlled. The valve device 10 includes a pump port 10p, a tank port 10t, and a cylinder port 10c. The pump port 10p is connected to a discharge port of the hydraulic pump P via an oil passage (pressure oil pipe) L1, and an oil passage (pressure oil pipe). ) The tank port 10t is connected to the tank T, which is used as an oil reservoir in the transmission of the rice transplanter, for example, via L2, and the cylinder port 10c is connected to the oil chamber 2a of the lift cylinder 2 via the oil passage (pipe) L3. Connected.

  The valve device 10 will be described with reference to FIGS. The valve device 10 has a valve case 11, and a pressure regulating relief valve 15, a flow rate control valve 16, a direction control valve 20, and a variable throttle valve 25 are housed in the valve case 11. Further, an electromagnetic stop valve 30 is mounted on a manifold 40 that is externally attached to the valve case 11 for pipe connection to the lift cylinder 2.

  The directional control valve 20 that is a spool valve includes land portions that open and close the pump passage 20p, the tank passage 20t, the cylinder passage 20c, and the passage 20r formed in the valve case 11, respectively. A pump oil passage 11 a is formed in the valve case 11 so as to extend from the pump passage 20 p, and an opening end portion of the pump oil passage 11 a on the outer surface of the valve case 11 is used as a pump port 11 p of the valve case 11. Yes. A pipe joint 12 is attached to the opening end of a pump oil passage 11a serving as the pump port 11p, and the pump port 10p of the valve device 10 shown in FIG. Is configured. A pressure oil pipe as an oil passage L1 shown in FIG. 1 is connected to the pipe joint 12. Moreover, the line filter 13 shown in FIG. 1 is provided in the pipe joint 12, and the oil from the pressure oil pipe as the oil passage L1 is filtered by the line filter 13 and flows into the pump oil passage 11a. It is said.

  In the valve case 11, a pressure regulating relief valve 15 and a flow rate control valve 16 are connected to the pump oil passage 11a, and from the hydraulic pump 11 flowing into the pump oil passage 11a from the pipe joint 12 as the pump port 10p. The discharged oil is regulated by the pressure regulating relief valve 15, further metered by the flow control valve 16, and supplied to the pump port 20 p of the direction control valve 20. A pipe joint 14 serving as the cylinder port 10c, which is provided with a pipe joint 12 serving as the pump port 10p and a pipe joint 13 serving as the tank port 10t on the outside, is provided in the electromagnetic stop valve 30. A line filter 18 illustrated in FIG. 1 is mounted in the line filter 13 and the pipe joint 17 illustrated in FIG.

  A tank oil passage 11b extending from the tank passage 20t is formed in the valve case 11 so as to merge with the relief passage 15a of the pressure regulating relief valve 15 and the relief passage 16a of the flow control valve 16. The open end of the tank oil passage 11b on the outer surface of the valve case 11 (in the present embodiment, on the opposite side of the pump port 11p) serves as the tank port 11t of the valve case 11. A pipe joint 14 is fitted to the opening end of the tank oil passage 11b serving as the tank port 11t, and the tank port of the valve device 10 shown in FIG. 10t is configured. A pressure oil pipe as an oil passage L2 shown in FIG. 1 is connected to the pipe joint 14. In the valve case 11, an oil passage 11r is formed for sending oil from the passage 20r through the variable throttle valve 25 to the tank oil passage 11b.

  Further, a cylinder oil passage 11 c extending from the cylinder passage 20 c is formed in the valve case 11, and an opening end portion thereof is used as a cylinder port 11 d of the valve case 11. Furthermore, a pilot oil passage 11e that branches from the cylinder oil passage 11c to the flow control valve 16 is formed in the valve case 11, and the control valve is controlled during the transition period from the neutral position to the ascent position. When 20 restricts the flow rate to the cylinder port 10c, the flow control valve 16 opens and closes to discharge the excess oil.

  An electromagnetic stop valve 30 is externally attached to the valve case 11 via a manifold 40. The manifold 40 forms therein a valve chamber 43 that houses the check valve assembly 50 of the electromagnetic stop valve 30, and is connected to the pump / tank side oil passage 42 and the cylinder through the valve chamber 43 in a direction perpendicular to each other. A side oil passage 44 is formed. An opening end of the pump / tank side oil passage 42 is used as a pump / tank port 41 of the manifold 40. By inserting the end of the manifold 40 as the pump / tank port 41 into the open end of the valve case 11 as the cylinder port 11d, the electromagnetic stop valve 30 is attached to the valve case 11, and the valve case 11 The cylinder oil passage 11 c in the inside communicates with the pump / tank side oil passage 42 in the manifold 40.

  On the other hand, the opening end of the cylinder side oil passage 44 is used as a cylinder port 45 of the manifold 40, and the pipe joint 17 is fitted into the opening end of the manifold port 45, and the cylinder port 45 and the pipe joint 17 of the manifold 40 are fitted. Thus, the cylinder port 10c of the valve device 10 shown in FIG. 1 is configured. A pressure oil pipe as an oil passage L3 shown in FIG. 1 is connected to the pipe joint 17. A line filter 18 shown in FIG. 1 is provided in the pipe joint 17.

  Next, the directional control valve 20 in the valve device 10 will be described in detail with reference to FIGS. The direction control valve 20 includes a spool 21, and the spool 21 is switched to the raised position U, the neutral position N, and the lowered position D by movement in the axial direction. The spool 21 is biased to the lowered position D by a spring 22 wound around the spool 21. At the lowered position D, the spool 21 communicates between the pump passage 20p and the tank passage 20t at the land provided on the outer periphery thereof, so that the suction oil from the pump port 10p does not flow into the cylinder passage 20c, but the tank port 10t. The oil that flows into the cylinder passage 20c from the oil chamber 2a of the lift cylinder 2 is discharged to the tank port 10t through the variable throttle valve 25, while communicating with the cylinder passage 20c and the passage 20r. It is said. The throttle valve 25 has a function of suppressing the speed of the lift arm 1 that tends to descend by its own weight by limiting the flow rate from the cylinder passage 20c to the discharge oil passage 11b. In the state where the spool 21 is in the throttle lowering position Da during the transition from the lower position D to the lowering position D, the oil flow from the cylinder passage 20c to the passage 20r in the spool 21 is further restricted, and the working machine descends suddenly. I do n’t want to start.

  By moving the spool 21 from the lowered position D (through the diaphragm lowered position Da) in a direction against the spring 22 (in the direction of the arrow in FIG. 6), the spool 21 first reaches the neutral position N. In the neutral position N, the pump passage 20p and the tank passage 20t remain in communication, while the spool 21 blocks the cylinder passage 20c from the passage 20r and the tank passage 20t. As a result, even if oil flows from the oil chamber 2a of the lift cylinder 2 into the cylinder passage 20c, it cannot flow to the throttle passage 20r, and therefore the oil discharge from the lift cylinder 2 is stopped. Further, since the cylinder passage 20c does not communicate with the pump passage 20p, the oil from the pump port 10p is not supplied to the lift cylinder 2. Thus, in the neutral position N, the oil in the cylinder passage 20c does not flow unless the situation that the load from the lift cylinder 2 leaks to the tank port 10t side as described above occurs. The hydraulic pressure in the chamber 2a is held as it is, and the lift arm 1 is held at that position.

  When the spool 21 is further moved in the direction against the spring 22 to reach the raised position U, the spool 21 connects the pump passage 20p to the cylinder passage 20c through the land, while the tank passage 20t and the passage. 20r is closed, the suction oil from the pump port 10p is supplied to the cylinder oil passage 20d, and the check valve 32 of the electromagnetic stop valve 30 is opened by the oil pressure from the pump port 10p. The suction oil from the pump port 10p is supplied to the oil chamber 2a of the lift cylinder 2, and the lift arm 1 is rotated upward. In the state where the spool 21 is in the throttle raised position Ua during the transition from the neutral position N to the raised position U, the flow of oil passing through the cylinder passage 20c from the pump passage 20p is a notch formed on the surface of the land. It is restricted so that the working machine does not start to rise suddenly.

  Next, the configuration of the electromagnetic stop valve 30 will be described in detail with reference to FIGS. 1 to 5 and FIGS. 7 to 10. The electromagnetic stop valve 30 is configured as a cartridge type in which a check valve assembly 50 and a solenoid 60 are combined. The check valve assembly 50 is a combination of a valve seat member 51, a movable valve member 52, a spool 53, a spring 54, and a ball check valve 55. The valve seat member 51 is fitted and fixed in the valve chamber 43 of the manifold 40, and the nut portion 51 d is arranged outside the manifold 40. A portion of the valve seat member 51 facing the pump / tank side oil passage 42 is opened with a pump / tank side port 51a, and a portion facing the cylinder side oil passage 44 is opened with a cylinder side port 51c. doing. A valve seat 51b is formed in a portion of the valve seat member 51 between the pump / tank side port 51a and the cylinder side port 51c.

  The poppet-shaped movable valve member 52 is slidably disposed within the valve seat member 51 on the same axis as the pump / tank side oil passage 42 (hereinafter referred to as the axial direction of the electromagnetic stop valve 30). ing. When the movable valve member 52 is seated on the valve seat 51b of the valve seat member 51, the pump / tank side port 51a and the cylinder side port 51c of the valve seat member 51 are shut off, and the pump / tank side oil passage 42 The oil flow between the cylinder side oil passage 44 is blocked. This state is the closed state of the electromagnetic stop valve 30. The movable valve member 52 slides in the opposite direction with respect to the pump / tank side oil passage 42 and moves away from the valve seat 51b, so that the pump / tank side port 51a and the cylinder side port are provided in the valve seat member 51. A gap communicating with 51c is formed, and oil can flow between the pump / tank side oil passage 42 and the cylinder side oil passage 44. This state is the open state of the electromagnetic stop valve 30. A back pressure chamber 51e is formed in the nut portion 51d of the valve seat member 51 described above.

  A spool chamber 52a is formed in the movable valve member 52, and the spool chamber 52a and the cylinder side port 51c of the valve seat member 51 are always connected (whether the movable valve member 52 is seated on the valve seat 51b or not). Regardless of this, an oil passage 52b is formed. The spool 53 is disposed in the spool chamber 52 a of the movable valve member 52 so as to be slidable relative to the movable valve member 52 in the axial direction of the electromagnetic stop valve 30. A spiral groove 53a is formed in the outer periphery of the spool 53, and oil that flows into the spool chamber 52a via the oil passage 52b can flow into the back pressure chamber 51e via the spiral groove 53a. .

  Further, the movable valve member 52 is formed with an orifice 52 c so as to communicate the spool chamber 52 a with the pump / tank side port 51 a of the valve seat member 51. The opening end of the orifice 52c facing the spool chamber 52a is normally closed at the tip of the spool 53 (see FIGS. 7, 8, and 10). A spring 54 is interposed between the movable valve member 52 and the spool 53 in the spool chamber 52a.

  A ball check valve 55 is provided in a tip portion of the movable valve member 52 facing the pump / tank side port 51a. The opening end of the orifice 52c facing the pump / tank side port 51a communicates with the pump / tank side port 51a without being closed by the ball check valve 55 if the pump / tank side port 51a and the back pressure chamber 51e have the same pressure. However, when the pressure of the pump / tank side port 51a becomes higher than the back pressure chamber 51e, the ball check valve 55 is pressed by the hydraulic pressure, and the pump / tank side port 51a. Close the open end of the orifice 52c facing (see FIG. 8).

  The solenoid 60 is formed by combining an iron core cylinder 61, a movable iron core 62, a fixed iron core 63, a spring 64, a coil 65, and the like. The iron core cylinder 61 is a mounting member for the solenoid 60 as a whole, and the solenoid cylinder 60 is fitted and fixed in the back pressure chamber 51e that is opened by the nut portion 51d of the valve seat member 51 of the check valve assembly 50. The check valve assembly 50 is mounted. A movable iron core 62 is slidably provided in the axial direction of the electromagnetic stop valve 30 in the iron core cylinder 61 fitted and fixed in the back pressure chamber 51e. The spool 53 is fixed to the end of the spool 53 protruding into the pressure chamber 51e, and the spool 53 and the movable iron core 62 are integrally slid in the axial direction of the electromagnetic stop valve 30.

  On the opposite side of the movable iron core 62 from the check valve assembly 50, a fixed iron core 63 extends on the same axis as the movable iron core 62, and a coil 65 is provided around the fixed iron core 63 and the iron core cylinder 61. Yes. When the coil 65 is energized, the fixed iron core 63 is excited, and the movable iron core 62 slides in the direction opposite to the check valve assembly 50, that is, in the valve opening direction of the electromagnetic stop valve 30, and is attracted to the fixed iron core 63. The Further, a spring 64 is disposed inside the movable iron core 62, and the movable iron core 62 is urged by the spring 64 toward the check valve assembly 50, that is, in the valve closing direction of the electromagnetic stop valve 30. . As shown in FIG. 5 and the like, when the movable valve member 52 is seated on the valve seat 51b of the valve seat member 51, that is, when the electromagnetic stop valve 30 is closed, the movable core 62 is fixed. There is a gap G between the iron core 63 and the iron core 63.

  Note that a forced valve opening rod 66 is provided so as to pass through the shaft cores of the movable iron core 62 and the fixed iron core 63, and its outer end protrudes to the outside of the fixed iron core 63 and is forced to the protruding end. A valve opening knob 67 is fixed. For example, when it is desired to lower the work machine after the engine is stopped or when the solenoid 60 cannot be energized due to a failure in the electrical system, the forced valve opening knob 67 is manually operated to pull the forced valve opening rod 66. Then, the forcible valve opening rod 66 presses the movable iron core 62 against the fixed iron core 63, the movable valve member 52 is separated from the valve seat 51b, and the electromagnetic stop valve 30 can be forcibly opened. .

  Regarding the change in the state of the check valve assembly 50 of the electromagnetic stop valve 30 and the change in the oil flow in the manifold 40 in relation to the excitation / de-energization control of the solenoid 60 and the shift of the direction control valve 20, This will be described with reference to FIGS.

  First, FIG. 7 shows the state of the electromagnetic stop valve 30 in the non-excited state and the valve closed state, and FIG. 8 shows the state of the electromagnetic stop valve 30 in the open state with the solenoid 60 in the non-excited state. Show. When the coil 65 is not energized, the tip of the spool 53 that moves integrally with the movable iron core 62 is pressed against the movable valve member 52 by the spring 54 with the opening end of the orifice 52c closed as described above. Thus, the movable valve member 52 is pressed against the valve seat 51 b of the valve seat member 51.

  In this state, when the directional control valve 20 is in the neutral position N or the lowered position D, the hydraulic pressure in the pump / tank side port 51a is lower than that in the cylinder side port 51c, and as shown in FIG. Closes.

  Not only when the directional control valve 20 is in the lowered position D but also when it is in the neutral position N, the lift cylinder 2 is retracted in the direction in which the piston rod 3 contracts due to the weight of the work implement connected to the lift arm 1. Load is applied. However, as long as the solenoid 60 is in a non-excited state and the electromagnetic stop valve 30 is closed as shown in FIG. 7, the oil in the cylinder side oil passage 44 is thus introduced from the orifice 51b into the spool chamber 52a. It flows in and is guided into the back pressure chamber 51e, and the urging force of the spring 54 is applied to this oil pressure, so that the movable valve member 52 acts in the valve closing direction. Therefore, there is no situation where the work implement unexpectedly descends even though the directional control valve 20 is set to the neutral position N. In other words, the electromagnetic solenoid valve 30 functions as a stop valve (safety valve) that prevents oil leakage from the lift cylinder 2 to the direction control valve 20.

If the directional control valve 20 is moved to the raised position U while the solenoid 60 is de-energized, the movable valve member 52 is opened by receiving the oil pressure, and is supplied to the oil chamber 2a of the lift cylinder 2 to raise the work machine. Can be made. Accordingly, it can be said that the electromagnetic solenoid valve 30 when the solenoid 60 is de-energized also functions as a check valve that allows only the oil flow from the pump / tank side oil passage 42 to the cylinder side oil passage 44 of the manifold 40. .

  Next, FIGS. 9 and 10 show the state of the electromagnetic stop valve 30 when the solenoid 60 is excited. When the solenoid 60 is excited, the movable iron core 62 slides to the fixed iron core 63 and is attracted to the fixed iron core 63, and the spool 53 also slides integrally with the movable iron core 62 toward the solenoid 60 side. FIG. 9 shows an initial state in which the movable iron core 62 is attracted to the fixed iron core 63, and the spool 53 momentarily slides with the movable iron core 62 against the biasing force of the spring 54. The movable valve member 52 is still seated on the valve seat 51b by the hydraulic pressure in the spool chamber 52a.

  When the tip of the spool 53 is separated from the opening end of the orifice 52c facing the spool valve chamber 52a, the pump / tank side port 51a and the cylinder side port 51c communicate with each other via the spool chamber 52a, the oil passage 52b, and the orifice 52c. . Therefore, if the solenoid 60 is excited when the directional control valve 20 is set to the lowered position D, oil can be released from the oil chamber 2a of the lift cylinder 2 and the work implement can be lowered.

  The reason for switching the solenoid 60 from the non-excited state to the excited state may be that, for example, a switch for opening the electromagnetic stop valve 30 is provided in the vicinity of the driver's seat of the vehicle, and the operator manually switches the switch. . However, from the viewpoint of preventing an operation error (forgetting operation) of the stop valve, it is preferable to automatically switch the excitation / de-energization of the solenoid 60, and for raising and lowering the work implement in the vicinity of the driver's seat of the vehicle. It is preferable to electrically link the switching of excitation / non-excitation of the solenoid 60 with the shift of the direction control valve 20 by manually operating the operation tool (lever, switch, etc.). Therefore, the vehicle is provided with a controller, and a command signal is sent from the controller to the solenoid 60 of the electromagnetic stop valve 30 based on the detection of the operating position of the operating tool for lifting the work implement or the operating position of the spool 21 of the direction control valve 20. It is preferable that an automatic control system for the electromagnetic stop valve 30 is provided.

  When such an automatic control system is configured, when the directional control valve 20 is set at the lowered position D, the neutral position N, and the raised position U, whether the solenoid 60 should be excited or not excited. It becomes important. First, if the solenoid 60 is not energized, the directional control valve 20 is set to the lowered position D because the electromagnetic stop valve 30 does not open so that oil flows from the cylinder side port 51c to the pump / tank side port 51a. If so, the solenoid 60 should be excited. When the directional control valve 20 is set to the raised position U, the electromagnetic stop valve 30 causes oil to flow from the pump / tank side port 51a to the cylinder side port 51c regardless of whether the solenoid 60 is excited or not. However, from the viewpoint of cost performance, it is considered preferable to be non-excited.

  When the directional control valve 20 is set to the neutral position N, if the solenoid 60 is de-energized, the electromagnetic stop valve 30 at the non-excitation position 30a is reliably transferred from the cylinder side port 51c to the pump / tank side port 51a. Since the oil flow is cut off, it is possible to prevent the work machine from descending unexpectedly. Therefore, when the direction control valve 20 is set to the neutral position N, the electromagnetic stop valve 30 functions as a stop valve for preventing the work machine from unexpectedly descending.

  As described above, if the valve device 10 with the electromagnetic stop valve 30 of the present invention is used, the solenoid 60 of the electromagnetic stop valve 30 may be excited only when the direction control valve 20 is in the lowered position D. While suppressing power consumption, the natural descent of the work implement when the direction control valve 20 is set to the neutral position N can be reliably suppressed.

  Instead of the electromagnetic stop valve 30, a conventional stop valve configured to be switched by a manual switch operation or the like may be mounted on the valve device 10. In this case, an open end as a pump / tank side port of the stop valve may be connected to the cylinder port 11d of the valve case 11. Conversely, the valve device 10 with the electromagnetic stop valve 30 according to the present invention has been conventionally used as a lift control device for a work machine so that the electromagnetic stop valve 30 can be easily replaced with a conventional stop valve. Modularization is achieved by using the valve case 11 having the pressure regulating relief valve 15, the flow control valve 16, the direction control valve 20, the variable throttle valve 25 and the like as they are.

DESCRIPTION OF SYMBOLS 1 Lift arm 2 Lift cylinder 10 Valve apparatus 11 Valve case 11p (Valve case 11) Pump port 11t (Valve case 11) Tank port 11d (Valve case 11) Cylinder port 20 Directional control valve 30 Electromagnetic stop valve 40 Manifold 42 Pump / tank side oil passage 44 Cylinder side oil passage 50 Check valve assembly 60 Solenoid

Claims (3)

A hydraulic lift cylinder for raising and lowering the work implement, which is configured to supply pressure oil when raising the work implement and discharging pressure oil when lowering the work implement; A directional control valve for controlling supply / discharge, a valve case including the directional control valve, including a pump port, a tank port, and a cylinder port, and the cylinder port and the hydraulic pressure of the valve case A lifting control device for a work machine comprising a manifold interposed between a lift cylinder and an electromagnetic stop valve mounted on the manifold,
The manifold forms a pump / tank side oil passage and a cylinder side oil passage inside, and connects a portion where an end of the pump / tank side oil passage opens to the cylinder port of the valve case. A lifting control device for a working machine, which is detachably attached to a case, wherein an opening end of the cylinder side oil passage in the manifold can be connected to the hydraulic lift cylinder.   The electromagnetic stop valve functions as a check valve that allows only the flow of oil from the pump / tank side oil passage to the cylinder side oil passage of the manifold when the solenoid is not excited. 2. The working machine according to claim 1, wherein the valve is in an open state that allows oil to flow in both directions between the pump tank side oil passage and the cylinder side oil passage of the manifold. Lift control device. The directional control valve has a raised position for supplying pressure oil to the hydraulic lift cylinder, a lowered position for discharging pressure oil from the hydraulic lift cylinder, and supply / discharge of pressure oil in the hydraulic lift cylinder. The solenoid can be set to any neutral position for stopping, and the solenoid of the electromagnetic stop valve is energized only when the directional control valve is set to the lowered position. The lifting control device for a working machine according to claim 2, wherein the lifting control device is linked to an operation tool.

Images