KR20070068943A - Operator sensing hydraulic system of loading attachments in forklift trucks - Google Patents

Abstract

An operator sensing hydraulic system of a loading apparatus of a forklift truck is provided to operate the loading apparatus only when an operator is present by detecting the state of the operator. An operator sensing hydraulic system of a loading apparatus of a forklift truck includes a limit switch, an unloading valve(4), and a lift down lock solenoid valve(8). The limit switch is installed on a seat to detect the seated state of an operator. The unloading valve activates an unloading solenoid valve according to the seated state of the operator and normally operates the loading apparatus of the forklift truck. The lift down lock solenoid valve interrupts a hydraulic circuit so as not to lower a lift cylinder(6) even when a control valve(5) of the loading apparatus is switched.

Description

Operator Sensing Hydraulic System of Loading Attachments in Forklift Trucks}

1 is a circuit diagram of an unloading device hydraulic system of a general forklift truck;

Figure 2 is a circuit diagram of a driver-sensing unloading device hydraulic system of the forklift according to the present invention.

<Description of the symbols for the main parts of the drawings>

(1): prime mover (2): pump

(3): Priority valve (4): Unloading valve

(4-1): first logic valve (4-2): second logic valve

(4-3): Unloading solenoid valve (5): Unloading control valve

(5-1): First Directional Valve (5-2): Second Directional Valve

(5-3): Third Directional Valve (5-4): Fourth Directional Valve

(5-5): relief valve (5-6): tilt lock valve

(6): lift cylinder (7): tilt cylinder

(8): lift down lock solenoid valve (9): lift down control valve

(10): Lift-down safety valve (11): Suction stator

(12): return filter (13): first hydraulic line

14: second hydraulic line 15: hydraulic tank

16: third hydraulic line 17: fourth hydraulic line

(18): return line

The present invention relates to a driver-sensing unloading device hydraulic system of a forklift, and when the driver is normally in a position to operate the forklift (hereinafter when seated), the unloading device control valve is operated to operate the unloading device as the operator intends. However, if the unloading device control valve is operated irrespective of the driver's intention when the driver is displaced from the normal driving position (hereinafter the seat seating state), the hydraulic oil delivered to the unloading cylinder is bypassed to the hydraulic tank so that the unloading device It relates to a hydraulic system of a forklift truck which makes it inoperative.

The general forklift truck has an unloading device hydraulic system that can unload heavy loads, a steering system hydraulic system that can change the direction of movement of the forklift truck to move the load to a desired position, and a braking system hydraulic system that realizes driving deceleration of the forklift truck. In particular, the unloading device hydraulic system is a pump for discharging the pressure oil, the priming valve for distributing the flow to the steering device and the unloading device, the unloading device control valve for controlling the flow direction of the pressure oil and the flow rate, the third hydraulic line Or a lift down control valve and a lift down safety valve for preventing a sudden drop of the lift cylinder due to a rupture of the fourth hydraulic line, a hydraulic actuator for mechanical work, and the like.

Figure 1 shows a circuit diagram of a conventional forklift hydraulic system.

A pump 2 driven by a prime mover 1 such as an engine such as an internal combustion engine or the like is configured, and the pump 2 sucks hydraulic oil from the hydraulic tank 15 and transfers it to the priority valve 3. .

The priority valve is a steering load-sensitive flow rate distribution valve, which, when the steering wheel is operated, is preferentially distributed to the steering unit of the flow rate transferred from the pump 2, so that the steering operation is prioritized over the unloading device.

When the steering wheel is not operated, most of the flow rate transferred from the pump 2 is transferred to the unloading control valve 5, and in the neutral state in which the unloading control valve 5 is not operated, the hydraulic oil is returned to the return line 18. ) Is returned to the hydraulic tank (15), and when the unloading device control valve is operated for the purpose of changing the conveying direction of the hydraulic oil and controlling the flow rate, the hydraulic oil is transferred to the hydraulic actuators (6, 7), and the lift cylinder is raised and lowered and tilted. Fore and aft cylinders, and other auxiliary actuators, will perform mechanical tasks.

The unloading device control valve 5 includes a first direction switching valve 5-1, a second direction switching valve 5-2, a third direction switching valve 5-3, and a fourth direction switching valve 5-4. ), And the fifth direction change valve (5-5) and the like.

The first directional valve 5-1 is moved in the reverse direction such that the pressure oil discharged from the pump 2 is transferred to the large chamber of the lift cylinder 6 via the port 1A of the lowering device control valve 5. When the changeover is performed, the lift cylinder 6 rises, and when the first direction changeover valve 5-1 is switched in the reverse direction, the first direction changeover valve 5-1 moves the return line 18. The oil passage is formed so that the hydraulic oil is transferred to the hydraulic tank 15 via the lift cylinder 6, and the lift cylinder 6 is lowered by the weight of the mast.

The second directional valve 5-2 has a role of forming a flow path such that the mast has a foreground and a rear diameter. When the second direction change valve 5-2 is switched so that the pressure oil discharged from the pump 2 is transferred to the large chamber of the tilt cylinder 7 via the 2B port of the unloading device control valve 5, the mast Is generally in the foreground, the second directional valve (5) such that the pressure oil discharged from the pump (2) is moved to the small chamber of the tilt cylinder (7) via the port 2A of the unloading device control valve (5) When -2) is switched, the mast is usually rearviewed. The operation of the front and rear mirrors of the mast is generally operated as described above, but the direction of movement of the mast may be reversed from the above depending on the mounting conditions of the mast, the carriage and the tilt cylinder 7.

The third direction switching valve 5-3 and the fourth direction switching valve 5-4 have a role of controlling the movement direction of the auxiliary unloading device and the flow rate. The hydraulic oil discharged from the pump is transferred to the service ports 3A, 3B, 4A, and 4B of the unloading device control valve 5 so that the actuator of the auxiliary unloading device does mechanical work as the driver intends.

Then, in the unloading device control valve 5, a relief valve 5-5 is provided to prevent the pressure of the unloading device hydraulic circuit from rising above a prescribed pressure. The relief valve 5-5 causes the part or all of the pressure oil to flow back to the hydraulic tank 13 through the return line 18 when the pressure oil discharged from the pump 2 reaches the specified pressure, thereby unloading the hydraulic system. To keep it below the specified pressure.

However, the conventional unloading hydraulic system as described above has the following problems.

The unloading device control valve 5 is operated when the driver is seated, so that the hydraulic actuators 6 and 7 should be normally operated as the driver intends. Due to the operation of 5) and other unintended operation, the hydraulic actuators 6 and 7 have a problem that the driver may perform abnormal operation not intended. In particular, in the case of the lift cylinder 6, even when the prime mover 1 is not driven, the first directional valve 5-1 is opened so that the flow path to the large chamber of the lift cylinder 6 and the hydraulic tank 15 is opened. When the switch is made, the lift cylinder 6 is lowered, which may cause a dangerous situation in the forklift in the seat of the driver's seat.

The present invention has been made to solve the above-mentioned conventional problems, and when the unloading device control valve (5) is operated in a state where the driver is not normally in a position to operate the forklift, the unloading valve (4) And an unloading hydraulic system of the forklift which stops the mechanical movement of the unloading device by blocking the flow of the hydraulic oil to be transferred to the hydraulic actuator due to the operation of the lift down lock solenoid valve 8.

The present invention for achieving the above object is a pump for discharging the pressure oil by the drive of the prime mover, a priority valve for distributing the flow rate to the steering device and the unloading device, and the pressure oil discharged from the pump when the driver's seat is seated as a hydraulic tank Lifting due to returning unloading valve, unloading valve control valve to control the flow direction of the hydraulic oil and flow rate, lift down lock solenoid valve for preventing lowering due to the weight of the lift cylinder, rupture of the 3rd or 4th hydraulic line Lift down control valve and lift down safety valve to prevent the cylinder from descending, characterized in that consisting of a hydraulic actuator for mechanical work.

The configuration and operation of the present invention will be described in more detail with reference to the hydraulic circuit diagram shown in FIG. 2.

Figure 2 shows a hydraulic circuit diagram of a forklift driver sensitive unloading hydraulic system for achieving the object of the present invention.

The hydraulic system is provided with a pump 2 driven by a prime mover 1 such as an engine such as an internal combustion engine. The pump 2 sucks up the hydraulic oil stored in the hydraulic tank 15 by the driving force of the prime mover 1 and discharges the high pressure hydraulic oil. The discharged pressurized oil is transferred to the priorimetry valve 3, which has a role of sensing a load from the steering system and preferentially supplying a flow rate to the steering system.

When the steering system is not in operation, the priority valve 3 switches so that most of the flow rate discharged from the pump 2 is transferred to the unloading device. The flow rate via the priority valve 3 is transferred to the unloading valve 4.

The unloading valve 4 is composed of a first logic valve 4-1, a second logic valve 4-2, and an unloading solenoid valve 4-3. The unloading valve 4 is activated or deactivated according to whether the operator is seated or seated by the operator, and the unloading device of the forklift truck is operated only when the driver is seated in the seat due to the above operation. Make it work normally.

The driver's seat or seat is detected by the limit switch installed in the forklift's seat.

When the driver is seated in the seat, the electric signal detected from the limit switch controls the unloading solenoid valve 4-3 to be activated. When the unloading solenoid valve 4-3 is activated, the flow rate of the signal flow rate in the second hydraulic line 14 is blocked by the unloading solenoid valve 4-3 to the hydraulic tank 15. On the other hand, the first hydraulic line 13 is connected to the hydraulic tank 15 so that the signal flow rate in the first hydraulic line 13 is returned to the hydraulic tank 15. Due to the series of operations, the first logic valve is closed and the second logic valve is opened so that the hydraulic oil discharged from the pump 2 is returned to the hydraulic tank 15 through the T port of the unloading valve 4. Since the hydraulic oil formed from the pump 2 is not transferred to the unloading device, mechanical work in the hydraulic actuator becomes impossible.

On the other hand, in the state where the driver is seated in the seat, the electric signal detected from the limit switch is controlled to deactivate the unloading solenoid valve 4-3. When the unloading solenoid valve 4-3 is deactivated, the second hydraulic line 14 is connected to the hydraulic tank 15 so that the signal flow rate in the second hydraulic line 14 is returned to the hydraulic tank 15. On the other hand, the signal flow rate in the first hydraulic line 13 is blocked by the flow path to the hydraulic tank 15 by the unloading solenoid valve 4-3. Due to the series of operations, the first logic valve is opened and the second logic valve is closed, so that the pressure oil discharged from the pump 2 is transferred to the unloading control valve 5 through the S port of the unloading valve 4. Transported to ensure normal operation of the unloading device.

The pressure oil discharged to the S port of the unloading valve 4 is transferred to the unloading device control valve 5. The unloading device control valve 5 includes a first diverter valve 5-1, a second diverter valve 5-2, a third diverter valve 5-3, and a fourth diverter valve 5-4. ) And a relief valve 5-5, etc., and the above components implement the direction change of the hydraulic oil, control of the flow rate, control of the maximum system pressure, and the like.

As the first direction switching valve 5-1 is switched, the lift cylinder 6 performs the work of raising and lowering. When the seat is seated, the hydraulic oil discharged from the pump 2 from the unloading valve 4 is transferred to the hydraulic tank ( In the condition returned to 15), the lift cylinder 6 is lowered when the first direction switching valve 5-1 is switched so that the lift cylinder 6 is lowered. This is because when the first direction switching valve (5-1) is switched so that the lift cylinder (6) is lowered, the large chamber of the lift cylinder (6) is in communication with the hydraulic tank (15), and lift cylinder ( 6) This is because the pressurized oil filled in the large chamber is returned to the hydraulic tank 15.

That is, even if the hydraulic oil discharged from the pump 2 in the unloading valve 4 flows back into the hydraulic tank 15, the lift cylinder 6 can be lowered. A lift down lock solenoid valve (8) is required for complete unloading operation of the seat. The lift down lock solenoid valve 8 is installed on a hydraulic line connecting the unloading device control valve 5 and the large chamber of the lift cylinder 6. The lift down lock solenoid valve 8 is deactivated when the seat is seated, and the first directional valve 5-1 is switched so that the lift cylinder 6 is lowered to fill the large chamber of the lift cylinder 6. Even if a flow path is formed to flow back into the oil pressure hydraulic tank 15, when the lift down lock solenoid valve 8 is inactivated, the check valve in the lift down lock solenoid valve 8 causes the large lift cylinder 6 to move. The flow path between the chamber and the hydraulic tank 15 is blocked, so that the lift cylinder 6 can not be lowered.

In the condition that the oil pressure discharged from the pump 2 is returned to the hydraulic tank 15 through the unloading valve 4 when the seat is seated, the second turning valve 5-2 is in the foreground of the tilt cylinder 7. When switching is possible, the tilt cylinder 7 small chamber and the hydraulic tank 15 communicate with each other, and the mast is in the foreground by the mast load. However, with the tilt lock valve 5-6 provided in the unloading device control valve 5, the mast foreground due to the mast load under the above conditions can be prevented. When the hydraulic oil discharged from the pump 2 is transferred to the cargo handling device control valve 5, the tilt lock valve 5-6 is switched by the hydraulic oil discharged from the pump 2, and the tilt lock valve 5-6 The oil pressure of the small chamber of the tilt cylinder 7 is returned to the hydraulic tank 15 by the switching of, so that the foreground of the mast is possible. However, when the pressurized oil discharged from the pump 2 through the unloading valve 4 flows back into the hydraulic tank 15, switching of the tilt lock valve 5-6 becomes impossible, and the tilt lock valve 5- If 6) is not switched, the transfer of the hydraulic oil 15 to the hydraulic cylinder 15, which is filled in the tilt cylinder 7 small chamber, becomes impossible, so that the movement of the tilt cylinder 7 becomes impossible, and thus the foreground of the mast becomes impossible. In the condition that the oil pressure discharged from the pump 2 is returned to the hydraulic tank 15 through the unloading valve 4 when the seat is seated, the second turning valve 5-2 is in the foreground of the tilt cylinder 7. Even if the switchover is possible, the mast view by the mast load is impossible.

A lift down control valve 9 and a lift down safety valve 10 are provided on the hydraulic line connecting the unloading device control valve 5 and the large chamber of the lift cylinder 6. The lift down control valve 9 is installed for the purpose of controlling the lowering speed of the lift cylinder lowered by its own weight, and serves to pass the prescribed flow rate so that the lowering speed of the lift cylinder does not exceed the prescribed speed. Has The lift down safety valve 10 has a role of preventing a sudden drop of the lift cylinder 6 when the hydraulic line connecting the lift cylinder 6 and the unloading device control valve 5 is broken.

According to the configuration of the hydraulic circuit as described above, it is possible to implement a hydraulic system capable of controlling the unloading device according to whether the forklift driver's seat is seated. The illustrated hydraulic circuit of FIG. 2 illustrates one embodiment of the present invention.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by those skilled in the art without departing from the gist of the present invention as claimed in the claims. Of course, such changes will fall within the scope of the claims.

The effects of the present invention that can be expected by the configuration and action as described above are as follows.

The unloading device operates only when the driver's seat is seated by detecting whether the driver is seated, and it provides an effect of removing all risks that may occur when the unloading device is unintentionally operated when the driver's seat is seated.

Claims (2)

Pump 2 driven by prime mover 1 such as an engine such as an internal combustion engine, priority valve 3 for distributing the flow rate to the steering device and the unloading device, and unloading for controlling the transfer direction of the hydraulic oil and the flow rate. Lift down control valve 9 and lift down to prevent the lift cylinder 6 from suddenly lowering due to rupture of the device control valve 5 and the third hydraulic line 16 or the fourth hydraulic line 17. In the hydraulic system of the forklift, which includes the safety valve 10 and the hydraulic actuators 6 and 7 that perform mechanical work, A limit switch installed in the seat to determine whether the driver is seated or seated, The unloading solenoid valve 4-3 is activated or deactivated according to whether the seat or seat of the driver is received by the electric signal detected by the limit switch, and the forklift is unloaded only when the driver is seated on the seat. Unloading valve (4) to ensure normal operation of the device, Even if the unloading device control valve 5 is switched so that the lift cylinder 6 can be lowered when the driver's seat is seated, the lift down lock solenoid valve 8 which shuts off the hydraulic circuit so that the lift cylinder 6 does not lower, Driver forklift hydraulic system of the forklift, characterized in that comprising a. The method of claim 1, The unloading valve 4 is installed on the hydraulic line between the pump 2 and the inlet port P of the unloading device control valve 5, and the pressure oil discharged from the pump 2 is unloading device control valve 5. First logic valve (4-1) to be transferred to A second logic valve 4-2 for allowing the pressurized oil discharged from the pump 2 to flow back into the hydraulic tank 15; Driver unloading hydraulic system of the forklift, characterized in that it comprises a non-loading solenoid valve (4-3) for detecting the seat of the driver to control the direction of the logic valve.

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