CN107013513B - Lifting control device for working machine - Google Patents

Abstract

A lifting control device of a working machine comprises a lifting cylinder; a directional control valve for controlling supply/discharge of pressure oil in the lift cylinder; and a valve housing in which the directional control valve is installed and which has an opening portion serving as a pump port, a tank port, and a cylinder port, wherein the lift control device of the working machine is provided with a manifold interposed between the cylinder port of the valve housing and the hydraulic lift cylinder, and an electromagnetic shut-off valve attached to the manifold. A pump-tank side oil passage and a cylinder side oil passage are formed in the manifold, and a portion where an end portion of the pump-tank side oil passage opens is connected to an opening portion of the valve housing, which is the cylinder port, whereby the manifold is detachably attached to the valve housing.

Description

Lifting control device for working machine

Technical Field

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

Background

Conventionally, a riding rice transplanter includes: a vehicle main body; a working machine (an insertion portion) attached to a rear portion of the vehicle, the working machine including: a seedling stage, transplanting claws, a transplanting transmission for transmitting the output of an engine mounted on a vehicle to the seedling stage and the transplanting claws, and the like. A link mechanism is provided at a rear portion of the vehicle and is pivotally supported to be vertically rotatable, and the working machine is mounted to the vehicle so as to be movable up and down via the link mechanism.

The link mechanism is vertically rotated by the amount of movement of the piston of the lift cylinder (i.e., the amount of telescopic movement of the piston rod), and is configured as a hydraulic circuit system as disclosed in japanese unexamined patent application publication No. 62-198907 for controlling the operation of the piston of the hydraulic cylinder. The hydraulic circuit system includes: the directional control valve (spool valve) is used to select any one of three setting states, i.e., supply of oil to the lift cylinder, discharge of oil from the lift cylinder, and stop of supply/discharge of oil to/from the lift cylinder.

The directional control valve is switched mainly between a rising position for supplying oil to the lift cylinder and rotating the lift arm to rise, a falling position for discharging oil from the lift cylinder and rotating the lift arm to fall, and a neutral position for stopping the supply and discharge of oil to and from the lift cylinder and the lift arm, and the directional control valve is biased toward the falling position.

A manually operated shutoff valve is provided in an oil path between the directional control valve and the lift cylinder, and the work implement is maintained at a position where the directional control valve is set to a neutral position in a raised state, for example, when the work implement is raised for loading the riding rice transplanter. When the rice transplanting operation process is finished and the rice transplanting operation process is stored in a storehouse for a long time before the next season, the stop valve is closed through manual operation, so that the operating machine stopped in the ascending state is reliably kept at the position.

Disclosure of Invention

Problems to be solved by the invention

However, since the shutoff valve is manually operated, when the directional control valve is located at the neutral position after the lift, the shutoff valve is likely to be forgotten to be closed, and when oil to be sealed between the lift cylinder and the directional control valve has pressure due to the weight of the working machine when the oil is forgotten to be closed, the oil leaks toward the tank port side from a small gap between the directional control valve and the valve housing, and the working machine is likely to be accidentally lowered. In particular, when the work implement is loaded with a heavy load, the work implement is likely to fall down naturally when the operator forgets to close the stop valve.

Means for solving the problems

The present invention relates to a lifting control device for a working machine, comprising:

a hydraulic lift cylinder for raising and lowering the working machine, which is supplied with pressure oil when raising the working machine and discharges the pressure oil when lowering the working machine;

a directional control valve for controlling supply/discharge of pressure oil to/from the hydraulic lift cylinder; and

a valve housing in which the direction control valve is installed and having a pump port, an oil tank port, and a cylinder port.

In order to solve the above problems, the lift control device has the following features.

The disclosed device is provided with: and the manifold is clamped between the cylinder opening of the valve shell and the hydraulic lifting cylinder.

A pump/tank-side oil passage and a cylinder-side oil passage are formed in the manifold.

The portion of the manifold where the end of the pump/tank side oil passage opens is connected to the cylinder port of the valve casing, and is detachably attached to the valve casing.

The open end of the cylinder-side oil passage of the manifold can be connected to the hydraulic lift cylinder.

An electromagnetic shut-off valve is mounted in the manifold.

The electromagnetic cut-off 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 in a non-excited state of the solenoid thereof.

The solenoid is in an excited state, and is in an open state in which oil can be circulated in both directions between the pump-tank side oil passage and the cylinder side oil passage of the manifold.

The directional control valve is configured to be settable at any one of a rising position for supplying pressure oil to the hydraulic lift cylinder, a falling position for discharging pressure oil from the hydraulic lift cylinder, and a neutral position for stopping supply and discharge of pressure oil to the hydraulic lift cylinder.

Only when the directional control valve is set at the lowered position, the solenoid of the electromagnetic cut-off valve is linked to an operating tool of the directional control valve so as to be excited.

Effects of the invention

The lifting control device for a working machine, which can reliably prevent an accidental lowering of the working machine when the working machine is set in a stopped state, can be simply configured by installing a valve housing, which houses a directional control valve for controlling the supply of pressure oil to a hydraulic lift cylinder for lifting the working machine, and by detachably installing an automatically controllable electromagnetic cut-off valve via a manifold.

Further, since the cylinder port of the valve housing is a portion for mounting the manual-operated shutoff valve in the related art, the electromagnetic shutoff valve is provided with a manifold connectable to the portion, and modularization is achieved, and since the electromagnetic shutoff valve does not need to be equipped in the valve housing, and the lift control device of the working machine can be configured at low cost, the conventional shutoff valve can be mounted instead of the electromagnetic shutoff valve, and the lift control device of the conventional working machine can be easily changed to the lift control device of the conventional working machine.

Thus, the lifting control device of the working machine with excellent cost performance can be provided.

Further, the electromagnetic shutoff valve is configured to: the solenoid functions as a check valve that permits only the flow of oil from the pump/tank-side oil passage of the manifold to the cylinder-side oil passage in a non-excited state of the solenoid, and if this non-excited state is used, the solenoid functions as a shutoff valve in a state in which the lifting of the working machine is set to be stopped, and the flow of oil from the hydraulic lift cylinder to the directional control valve can be reliably stopped.

In the above-described configuration, the solenoid of the electromagnetic cut-off valve is excited only when the directional control valve is set to the lowered position, and thereby the solenoid is not excited when the directional control valve to stop the lifting of the working machine is set to the neutral position, and the electromagnetic cut-off valve automatically functions as the cut-off valve, and thus the leakage of oil from the hydraulic lift cylinder to the directional control valve can be reliably prevented, and the accidental lowering of the working machine can be prevented.

Drawings

Fig. 1 is a hydraulic circuit diagram including a valve device of the present invention.

Fig. 2 is a perspective view of the valve device.

Fig. 3 is a top view of the valve device.

Fig. 4 is a cross-sectional view along line IV-IV of fig. 3.

Fig. 5 is a front sectional view of the shutoff valve.

Fig. 6 is a cross-sectional view taken along line VI-VI of fig. 4.

Fig. 7 is a sectional view of a main part of the electromagnetic shutoff valve in a closed state in which a solenoid is not excited.

Fig. 8 is a sectional view of a main part of the electromagnetic shutoff valve in an open state in which a solenoid is not excited.

Fig. 9 is a sectional view of a main part of the electromagnetic shutoff valve in an initial open state in which the solenoid is excited.

Fig. 10 is a sectional view of a main part of the electromagnetic shutoff valve in a fully opened state in which a solenoid is excited.

Detailed Description

A structure of a hydraulic circuit for controlling raising and lowering of a working machine, which includes a valve device 10 according to the present invention, will be described with reference to fig. 1.

In a riding rice transplanter not shown, a lift arm 1 for lifting a working machine is pivotally supported by a pivot support shaft 1a so as to be vertically rotatable, and the tip end of a piston rod 3 of a lift cylinder 2 is pivotally connected to the lift arm 1.

The lift cylinder 2 is a single-acting hydraulic cylinder, and when oil is supplied to an oil chamber 2a of the lift cylinder 2, the piston rod 3 is extended to rotate the lift arm 1 upward to raise the working machine (including the transplanting portion of the seedling table); when oil is drawn from the oil chamber 2a, the piston rod 3 contracts, the lift arm 1 is rotated downward, and the work machine is lowered.

In the case of a rice transplanter, an operating tool such as a control lever for raising and lowering a working machine is disposed near a driver's seat, and when turning around a ridge or traveling on the road, the amount of telescopic movement of the piston rod 3 of the lift cylinder 2 (vertical rotation of the lift arm 1) is controlled by operating the operating tool in order to raise the working machine.

In addition, during the operation running, for the purpose of adjusting the height of the working machine, the amount of telescopic movement of the piston rod 3 of the lift cylinder 2 may be automatically controlled in accordance with the ground pressure of a float plate of the rice transplanter provided in the working machine.

In order to control the elevation of the working machine, the valve device 10, which is an elevation control device for the working machine according to the present invention, controls the supply of the discharge oil from the hydraulic pump P driven by the engine E of the rice planting machine to the oil chamber 2a of the lift cylinder 2 and the discharge of the discharge oil from the oil chamber 2 a.

The valve device 10 includes: the pump port 10P, the oil tank port 10T, and the cylinder port 10c are connected to the discharge port of the hydraulic pump P via an oil passage (pressure oil pipe) L1, the oil tank port 10T is connected to an oil tank T such as an oil sump in a transmission of a rice transplanter, for example, via an oil passage (pressure oil pipe) L2, and the cylinder port 10c is connected to the oil chamber 2a of the lift cylinder 2 via an oil passage (piping) L3.

The valve device 10 is explained with reference to fig. 1 to 6. The valve device 10 has a valve housing 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 built in the valve housing 11. Further, an electromagnetic shutoff valve 30 is attached to a manifold 40 externally provided to the valve housing 11 for pipe connection to the lift cylinder 2.

The directional control valve 20 as a spool includes: the shoulder portion opens and closes a pump passage 20p, a tank passage 20t, a cylinder passage 20c, and a passage 20r formed in the valve housing 11.

The pump oil passage 11a is formed in the valve housing 11 so as to extend from the pump passage 20p, and an opening end portion of the pump oil passage 11a on the outer side surface of the valve housing 11 is defined as a pump port 11p of the valve housing 11.

A pipe joint 12 is attached to an opening end portion of the pump oil passage 11a as the pump port 11p, and the pump port 10p of the valve device 10 shown in fig. 1 is configured by the pump port 11p of the valve housing 11 and the pipe joint 12.

To the pipe joint 12 is connected a pressure oil pipe as an oil passage L1 shown in fig. 1. Further, a line filter 13 shown in fig. 1 is provided in the pipe joint 12, and oil from the pressure oil line as the oil passage L1 is filtered by the line filter 13 and flows into the pump oil passage 11 a.

A pressure-adjusting relief valve 15 and a flow rate control valve 16 are connected to the pump passage 11a in the valve housing 11, and the discharge oil from the hydraulic pump 11, which flows into the pump passage 11a from the pipe joint 12 serving as the pump port 10p, is pressure-adjusted by the pressure-adjusting relief valve 15, and then is flow-adjusted by the flow rate control valve 16 to be supplied to the pump port 20p of the directional control valve 20.

Further, a tank oil passage 11b extending from the tank passage 20t is formed in the valve housing 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 rate control valve 16, and an opening end portion of the tank oil passage 11b on an outer side surface (an opposite side to the pump port 11p in the present embodiment) of the valve housing 11 is defined as a tank port 11t of the valve housing 11.

A pipe joint 14 is fitted into an opening end portion of the tank oil passage 11b as the tank port 11t, and the tank port 10t of the valve device 10 shown in fig. 1 is configured by the tank port 11t of the valve housing 11 and the pipe joint 14. To the pipe joint 14 is connected a pressure oil pipe as an oil passage L2 shown in fig. 1.

Further, an oil passage 11r for feeding the oil passing through the variable throttle 25 from the passage 20r to the tank oil passage 11b is formed in the valve housing 11.

Further, a cylinder oil passage 11c extending from the cylinder passage 20c is formed in the valve housing 11, and the opening end portion thereof is defined as a cylinder port 11d of the valve housing 11.

A pilot oil passage 11e that branches from the cylinder oil passage 11c to the flow rate control valve 16 is formed in the valve housing 11, and when the control valve 20 restricts the flow rate to the cylinder port 10c in a transition period of the directional control valve 20 from the neutral position to the raised position, the flow rate control valve 16 that discharges the surplus oil is opened and closed in accordance with the restriction.

An electromagnetic shutoff valve 30 is externally mounted to the valve housing 11 via a manifold 40.

The manifold 40 has a valve chamber 43 in which the check valve assembly 50 of the electromagnetic shutoff valve 30 is housed, and a pump/tank side oil passage 42 and a cylinder side oil passage 44 that are connected to each other at right angles are formed via the valve chamber 43.

An opening end portion of the pump/tank-side oil passage 42 is defined as a pump/tank port 41 of the manifold 40. The electromagnetic shutoff valve 30 is attached to the valve housing 11 by fitting the end portion of the manifold 40, which is the pump/tank port 41, into the opening end portion of the cylinder port 11d, which is the valve housing 11, and the cylinder oil passage 11c in the valve housing 11 and the pump/tank side oil passage 42 in the manifold 40 communicate with each other.

On the other hand, the opening end of the cylinder-side oil passage 44 is a cylinder port 45 of the manifold 40, the pipe joint 17 is fitted to the opening end of the cylinder port 45, and the cylinder port 10c of the valve device 10 shown in fig. 1 is configured by the cylinder port 45 of the manifold 40 and the pipe joint 17. The pipe joint 17 is connected with a pressure oil pipe as an oil passage L3 shown in fig. 1. In addition, a line filter 18 shown in fig. 1 is provided in the pipe joint 17.

Next, the directional control valve 20 of the valve device 10 will be described in detail with reference to fig. 1, 6, and the like.

The directional control valve 20 includes a spool 21, and the spool 21 is switched to a rising position U, a neutral position N, and a falling position D by movement in the axial direction thereof.

The spool 21 is biased toward the lowering position D by a spring 22 wound around the spool 21. In the lowering position D, the spool valve 21 communicates the pump passage 20p and the tank passage 20t via a land provided on the outer periphery thereof, so that the suction oil from the pump port 10p flows through the tank port 10t without flowing to the cylinder passage 20c, and communicates the cylinder passage 20c and the passage 20r, so that the oil flowing from the oil chamber 2a of the lift cylinder 2 into the cylinder passage 20c is discharged to the tank port 10t via the variable throttle valve 25.

The throttle valve 25 has a function of suppressing the speed of the lift arm 1 that is about to descend by its own weight by restricting the flow speed from the cylinder passage 20c to the discharge oil passage 11b, but in addition to this, in a state where the spool 21 is located at the throttle-down position Da in the middle of the transition from the neutral position N to the down position D, the flow of oil from the cylinder passage 20c to the passage 20r in the spool 21 is further throttled, and the work machine does not start to descend suddenly.

By moving the spool 21 from the lowering position D (past the throttle lowering 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 are always in communication, while the spool 21 may block the cylinder passage 20c from the passage 20r or block the cylinder passage 20c from the tank passage 20 t. Thus, even if oil flows into the cylinder passage 20c from the oil chamber 2a of the lift cylinder 2, the oil cannot flow into the orifice passage 20r, and therefore, the discharge of the oil 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.

In this way, in the neutral position N, as long as the situation in which the oil leaks to the tank port 10t side due to the load from the lift cylinder 2 as described above does not occur, the oil in the cylinder passage 20c does not flow, and therefore the oil pressure in the oil chamber 2a of the lift cylinder 2 is maintained in this state, and the lift arm 1 is held at the current position.

When the spool valve 21 is moved in the direction against the spring 22 to reach the raised position U, the spool valve 21 connects the pump passage 20p to the cylinder passage 20c via its land, closes the tank passage 20t and the passage 20r, respectively, and supplies the suction oil from the pump port 10p to the cylinder passage 20d, and opens the check valve 32 of the electromagnetic shutoff valve 30 by the oil pressure of the oil from the pump port 10p to supply the suction oil from the pump port 10p to the oil chamber 2a of the lift cylinder 2, thereby rotating the lift arm 1 upward.

In the state where the spool 21 is at the throttle up position Ua in the middle of the transition from the neutral position N to the up position U, the flow of oil from the pump passage 20p through the cylinder passage 20c is restricted by the notch formed in the surface of the land, and the work machine does not start to rise quickly.

Next, the structure of the electromagnetic shutoff valve 30 will be described in detail with reference to fig. 1 to 5 and 7 to 10.

The electromagnetic shutoff valve 30 is configured as a cylinder type in which a check valve assembly 50 and a solenoid 60 are combined.

The check valve assembly 50 is formed by combining a valve seat member 51, a movable valve member 52, a spool 53, a spring 54, and a check ball valve 55.

The valve seat member 51 is fitted into and fixed to the valve chamber 43 of the manifold 40, and the nut portion 51d thereof is disposed outside the manifold 40. A pump/tank side port 51a opens in a portion of the valve seat member 51 facing the pump/tank side oil passage 42, and a cylinder side port 51c opens in a portion facing the cylinder side oil passage 44. Further, 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 51 c.

A movable valve member 52 having a poppet shape is disposed in the valve seat member 51 so as to be slidable on the same axial center as the pump/tank side oil passage 42 (hereinafter, referred to as the axial center direction of the electromagnetic shutoff valve 30).

By seating the movable valve member 52 on the valve seat 51b of the valve seat member 51, the space between the pump/tank-side port 51a and the cylinder-side port 51c of the valve seat member 51 is blocked, and the flow of oil between the pump/tank-side oil passage 42 and the cylinder-side oil passage 44 is blocked. This state is a closed state of the electromagnetic cut-off valve 30.

Then, the movable valve member 52 slides on the opposite side of the pump/tank side oil passage 42 and moves away from the valve seat 51b, so that a gap is created in the valve seat 51 to communicate the pump/tank side port 51a with the cylinder side port 51c, 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 cut-off valve 30.

Further, a back pressure chamber 51e is formed in the nut portion 51d of the valve seat member 51.

The movable valve member 52 has a spool valve chamber 52a formed therein, and an oil passage 52b formed therein for allowing the spool valve chamber 52a and the cylinder port 51c of the valve seat member 51 to communicate with each other at all times (regardless of whether the movable valve member 52 is seated on the valve seat 51 b).

In the spool chamber 52a of the movable valve member 52, the spool 53 is disposed so as to be slidable relative to the movable valve member 52 in the axial direction of the electromagnetic shutoff valve 30. A spiral groove 53a is formed in the outer peripheral portion of the spool valve 53, and oil that has flowed into the spool chamber 52a through the oil passage 52b can flow into the back pressure chamber 51e through the spiral groove 53 a.

Further, a damper hole 52c is formed in the movable valve member 52 so as to communicate the spool chamber 52a with the pump/tank side port 51a of the valve seat member 51. Normally, the open end of the orifice 52c facing the spool chamber 52a is closed by the tip end of the spool 53 (see fig. 7, 8, and 10).

Further, a spring 54 is interposed between the movable valve member 52 and the spool 53 in the spool chamber 52 a.

A check ball valve 55 is provided in a tip end portion of the movable valve member 52 facing the pump/tank side port 51 a.

If the pressure of the pump/tank side port 51a is equal to the pressure of the back pressure chamber 51e, the open end of the orifice 52c facing the pump/tank side port 51a is not closed by the check ball valve 55 but communicates with the pump/tank side port 51a (see fig. 7, 9, and 10), but when the pressure of the pump/tank side port 51a becomes higher than the pressure of the back pressure chamber 51e, the check ball valve 55 is pressed by the oil pressure to close the open end of the orifice 52c facing the pump/tank side port 51a (see fig. 8).

The solenoid 60 is formed by combining a core barrel 61, a movable core 62, a fixed core 63, a spring 64, a coil 65, and the like.

The core barrel 61 is a mounting member for the entire solenoid 60, and the solenoid 60 is mounted to the check valve assembly 50 by fitting and fixing the core barrel 61 into the back pressure chamber 51e that is opened in the nut portion 51d of the valve seat member 51 of the check valve assembly 50.

A movable core 62 is provided in a core barrel 61 fitted and fixed to the back pressure chamber 51e so as to be slidable in the axial direction of the electromagnetic shutoff valve 30, and a tip end portion thereof is brought into close contact with an end portion of the spool 53 protruding from the movable valve member 52 into the back pressure chamber 51e, and the spool 53 is slid in the axial direction of the electromagnetic shutoff valve 30 integrally with the movable core 62.

A fixed core 63 extends on the same axial center as the movable core 62 on the opposite side of the movable core 62 from the check valve assembly 50, and a coil 65 is provided around the fixed core 63 and the core tube 61.

When the coil 65 is energized, the fixed core 63 is excited, and the movable core 62 slides in the opposite direction to the check valve assembly 50, that is, in the valve opening direction of the electromagnetic shutoff valve 30, and is attracted to the fixed core 63.

Further, a spring 64 is disposed inside the movable core 62, and the spring 64 biases the movable core 62 toward the check valve assembly 50, that is, in the valve closing direction of the electromagnetic shutoff 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 shutoff valve 30 is closed, a gap G is formed between the movable core 62 and the fixed core 63.

A forced opening valve lever 66 is provided so as to penetrate through the axial center portions of the movable iron core 62 and the fixed iron core 63, and an outer end portion thereof protrudes outward of the fixed iron core 63, and a forced opening valve knob 67 is fixed to the protruding end portion.

For example, the configuration is: when the work machine is to be lowered after the engine is stopped or when the solenoid 60 cannot be energized due to a failure of the electric system, the forcible opening knob 67 is manually operated to pull the forcible opening lever 66, the forcible opening lever 66 is in a state where the movable core 62 is pressed against the fixed core 63, the movable valve member 52 is separated from the valve seat 51b, and the electromagnetic shutoff valve 30 can be forcibly opened.

With reference to fig. 7 to 10, the state change of the check valve assembly 50 of the electromagnetic shutoff valve 30, the change of the flow of oil in the manifold 40, and the like, which are associated with the excitation/non-excitation of the control solenoid 60 and the shifting of the directional control valve 20, will be described.

First, fig. 7 shows a case of the electromagnetic cut-off valve 30 in a closed state with the solenoid 60 being in an unexcited state, and fig. 8 shows a case of the electromagnetic cut-off valve 30 in an opened state with the solenoid 60 being in an unexcited state.

When the coil 65 is not energized, the tip end of the spool 53 that moves integrally with the movable core 62 is pressed against the movable valve member 52 by the spring 54 in a state where the opening end of the orifice 52c is closed as described above, and thereby the movable valve member 52 is pressed against the valve seat 51b of the valve seat member 51.

In this state, when the directional control valve 20 is in the neutral position N or the lowering position D, the hydraulic pressure in the pump/tank side port 51a is lower than that in the cylinder side port 51c, and the electromagnetic cut-off valve 30 is closed as shown in fig. 7.

When the directional control valve 20 is located at the neutral position N as well as when the directional control valve 20 is located at the lowering position D, a load in a direction in which the piston rod 3 contracts is applied to the lift cylinder 2 by the weight of the working machine coupled to the lift arm 1. However, when the solenoid 60 is in the non-excited state, as shown in fig. 7, as long as the electromagnetic shutoff valve 30 is closed, the oil in the cylinder side oil passage 44 flows from the orifice hole 51b into the slide valve chamber 52a and is guided into the back pressure chamber 51e, and the biasing force of the spring 54 is added to the oil pressure, thereby acting on the movable valve member 52 in the valve closing direction.

Therefore, although the directional control valve 20 is set at the neutral position N, the work implement does not drop unexpectedly. In other words, the electromagnetic solenoid valve 30 functions as a shutoff valve (relief valve) that prevents oil from leaking from the lift cylinder 2 to the directional control valve 20.

Further, if the directional control valve 20 is set to the raising position U in the state where the solenoid 60 is not excited, the movable valve member 52 is opened by receiving the hydraulic pressure thereof, and oil is supplied to the oil chamber 2a of the lift cylinder 2 to raise the working machine.

Therefore, it can be said that the electromagnetic solenoid valve 30 when the solenoid 60 is not excited also functions as a check valve that allows only the flow of oil from the pump/tank side oil passage 42 to the cylinder side oil passage 44 of the manifold 40.

Next, fig. 9 and 10 show the electromagnetic cut-off valve 30 when the solenoid 60 is excited.

When the solenoid 60 is excited, the movable core 62 slides toward the fixed core 63, and the spool 53 is attracted to the fixed core 63 and also slides toward the solenoid 60 integrally with the movable core 62.

Fig. 9 is a diagram showing an initial state in which the movable core 62 is attracted to the fixed core 63, and the spool 53 instantaneously slides together with the movable core 62 against the biasing force of the spring 54, but the movable valve member 52 is still seated on the valve seat 51b by the hydraulic pressure in the spool chamber 52 a.

When the tip end of the spool 53 leaves the open end of the orifice 52c facing the spool chamber 52a, the pump/tank-side port 51a and the cylinder-side port 51c communicate via the spool chamber 52a and the oil passage 52b or the orifice 52 c. Therefore, if the solenoid 60 is excited when the directional control valve 20 is located at the lowering position D, oil is drawn from the oil chamber 2a of the lift cylinder 2, and the working machine can be lowered.

To switch the solenoid 60 from the non-excited state to the excited state, it is conceivable to: for example, a switch for opening the electromagnetic cut-off valve 30 is provided in the vicinity of the driver's seat of the vehicle in advance, and the operator manually performs a switching operation of the switch. However, from the viewpoint of preventing an operational error (forgetting to operate) of the shutoff valve, it is preferable that the switching of the excitation/non-excitation of the solenoid 60 is performed automatically, and it is preferable that the switching of the excitation/non-excitation of the solenoid 60 is electrically connected to the shifting of the directional control valve 20 that manually operates an operation tool (a control lever, a switch, or the like) for raising and lowering the working machine located near the driver's seat of the vehicle.

Therefore, it is preferable that the vehicle is provided with a controller and an automatic control system of the electromagnetic cut-off valve 30, and the automatic control system of the electromagnetic cut-off valve 30 is configured to: based on the detection of the operation position of the operation tool for raising and lowering the work implement or the operation position of the spool 21 of the directional control valve 20, a command signal is sent to the solenoid 60 of the electromagnetic cut-off valve 30 by the controller.

When configuring such an automatic control system, it is important to excite or deexcite the solenoid 60 when setting the directional control valve 20 at each of the lowering position D, the neutral position N, and the raising position U.

First, if the solenoid 60 is not excited, the electromagnetic cut-off valve 30 does not open so that oil flows from the cylinder-side port 51c to the pump/tank-side port 51a, and therefore, when the directional control valve 20 is set at the lowered position D, the solenoid 60 should be excited.

When the directional control valve 20 is set at the raised position U, the electromagnetic cut valve 30 is opened so that the oil flows from the pump/tank side port 51a to the cylinder side port 51c regardless of whether the solenoid 60 is in the excited or non-excited state.

When the solenoid 60 is deenergized when the directional control valve 20 is set to the neutral position N, the electromagnetic cut-off valve 30 in the deenergized position 30a reliably blocks the flow of oil from the cylinder-side port 51c to the pump/tank-side port 51a, and therefore, accidental lowering of the work machine can be prevented. Therefore, when the directional control valve 20 is set to the neutral position N, the electromagnetic cut-off valve 30 functions as a cut-off valve for preventing an unexpected lowering of the working machine.

As described above, if the valve device 10 including the electromagnetic cut-off valve 30 according to the present invention is used, the solenoid 60 of the electromagnetic cut-off valve 30 is only excited when the direction control valve 20 is set to the lowering position D, and therefore, the natural lowering of the working machine when the direction control valve 20 is set to the neutral position N can be reliably suppressed while the power consumption is controlled.

Instead of the electromagnetic cut-off valve 30, a conventional cut-off valve that can be switched by a switching operation of a switch by a manual operation or the like may be attached to the valve device 10. In this case, the opening end portion of the pump/tank side port as the shutoff valve may be connected to the cylinder port 11d of the valve housing 11.

Conversely, in the valve device 10 including the electromagnetic shut-off valve 30 of the present invention, the valve housing 11 in which the relief valve 15 for pressure adjustment, the flow rate control valve 16, the directional control valve 20, the variable throttle valve 25, and the like, which have been conventionally used as an elevation control device of a working machine, are incorporated is used as it is, and thus modularization is achieved so that the electromagnetic shut-off valve 30 can be easily replaced with an existing shut-off valve.

Description of reference numerals:

1 lifting arm

2 lifting cylinder

10-valve device

11 valve housing

11p (of the valve housing 11) pump port

11t (of the valve housing 11) oil tank port

11d (of the valve housing 11) cylinder port

20-way control valve

30 electromagnetic stop valve

40 manifold

42 pump/oil tank side oil circuit

44 cylinder side oil circuit

50 one-way valve assembly

60 solenoid.

Claims (3)

1. A lifting control device for a working machine is provided with:

a hydraulic lift cylinder for raising and lowering the working machine, which is supplied with pressure oil when raising the working machine and discharges the pressure oil when lowering the working machine;

a directional control valve for controlling supply/discharge of pressure oil to/from the hydraulic lift cylinder; and

a valve housing in which the direction control valve is installed and having a pump port, an oil tank port, and a cylinder port,

the lift control device for a working machine is characterized in that,

the disclosed device is provided with: a manifold clamped between the cylinder port of the valve housing and the hydraulic lift cylinder,

a pump/tank-side oil passage and a cylinder-side oil passage are formed in the manifold,

a portion of the manifold, at which an end portion of the pump-tank side oil passage opens, is connected to the cylinder port of the valve casing and is detachably attached to the valve casing,

the open end portion of the cylinder-side oil passage of the manifold can be connected to the hydraulic lift cylinder,

an electromagnetic shut-off valve is installed in the manifold,

the electromagnetic shutoff valve and the manifold are configured to be replaceable as a module.

2. The lift control device of a working machine according to claim 1,

the electromagnetic cut-off valve functions as a check valve that permits only a flow of oil from the pump/tank-side oil passage to the cylinder-side oil passage of the manifold in a non-excited state of a solenoid thereof,

the electromagnetic cut-off valve is in an open state in which oil can be bidirectionally circulated between the pump/tank side oil passage and the cylinder side oil passage of the manifold in an excited state of the solenoid.

3. The elevation control apparatus of a working machine according to claim 2,

the directional control valve is configured to be settable at any one of a rising position for supplying pressure oil to the hydraulic lift cylinder, a falling position for discharging pressure oil from the hydraulic lift cylinder, and a neutral position for stopping supply/discharge of pressure oil to/from the hydraulic lift cylinder,

only when the directional control valve is set at the lowered position, the solenoid of the electromagnetic cut-off valve is linked to an operating tool of the directional control valve so as to be excited.

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