JPH06144794A - Oil-hydraulic circuit for lift cylinder in cargo handling device - Google Patents

Abstract

PURPOSE:To enhance workability by forming an oil-hydraulic circuit for lift cylinder into a small and simple configuration in a cargo handling device for cargo vehicle. CONSTITUTION:The location for flowing pressure oil in a first line 16 to a tank 18 is provided with an operating valve 17 for switching operation. The piston 4 of a lift cylinder 2 is provided with check valves 8 for flowing pressure oil in a rod chamber 6 to a bottom chamber 7 when oil hydraulic pressure in the rod chamber 6 has increased. An actuator 23 is provided between the rod chamber 6 of the lift cylinder 2 and the tank 18. In the actuator 23, its inner channel 24 is provided with a suction valve 26 formed in a closed position under normal operation and an open position by negative pressure in the rod chamber 6, and a piston part 29 is provided to actuate the suction valve 26 to the open position. The piston part 29 is connected to a pilot line 34 connected to the bottom chamber 7 of the lift cylinder 2 to actuate the piston part 29 by oil hydraulics in the bottom chamber 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lift cylinder hydraulic circuit for raising and lowering a fork in a cargo handling apparatus for a cargo handling vehicle such as a forklift truck.

[0002]

2. Description of the Related Art Conventionally, in a cargo handling apparatus for a cargo handling vehicle such as a forklift truck, the fork rising speed is changed depending on whether there is a load on the fork and the load is large, or when there is no load on the fork and the load is small. It is known to have been made. A hydraulic circuit for a lift cylinder that supplies pressure oil to the bottom chamber and the rod chamber of the lift cylinder that moves up and down the fork of the cargo handling vehicle is connected to the tank 40 via a pump 41, as shown in FIG. A pump line 42 and a tank line 43 connected to the tank 40 are provided, and the pump line 42 and the tank line 43 are connected to the operation valve 44. The operation valve 44 has a pump port 44a, a tank port 44b, a first port 44c and a second port 44d. The pump port 44a is connected to the pump line 42 and the tank port 44b is connected to the tank line 43. In the middle position F, the pump port 44a and the tank port 44b are connected to each other and the first port 4
4c and the second port 44d are blocked, and at the upper position E, the pump port 44a is connected to the first port 44c and the tank port 44b and the second port 44d are blocked,
In the lower position G, the first port 44c and the second port 44
connected to the pump port 44a and the tank port 44b.
And are to be cut off. And the operation valve 44
To the first port 44c of the first conduit 45, the second port 44
The second pipelines 46 are respectively connected to d, and the first pipeline 4 is connected.
5 and the second conduit 46 are connected to the actuator 47. On the other hand, a lift cylinder 49 that moves up and down the fork 48 is provided with a rod conduit 51 that connects to the rod chamber 50 and a bottom conduit 53 that connects to the bottom chamber 52.
Is provided, and the rod conduit 51 and the bottom conduit 53 are connected to the actuator 47. Inside the actuator 47, the first conduit 45 and the bottom conduit 53 are connected by a first internal flow path 54, and a first switching valve 55 and a second switching valve 56 are internally provided. The first switching valve 5 is provided.
5 has a first port 55a, a second port 55b, and a third port 55c, the rod conduit 51 is connected to the first port 55a, and in the lower position H, the first port 55a.
To the second port 55b, the third port 55c is blocked, the first port 55a and the third port 55c are connected in the upper position I, the second port 55b is blocked, and the first switching valve 55 is connected. The second port 55b is connected to the first internal flow path 54 through the check valve 57, and the third port 55c is connected to the second internal flow path 58.
The switching operation of the first switching valve 55 is performed by the first internal flow path 54.
So as to be operated by the hydraulic pressure of the first internal flow path 54 in the pilot conduit 59 connected to the second internal flow path 58 and operated by the hydraulic pressure of the second internal flow path 58 in the pilot conduit 60 connected to the second internal flow path 58. It has become. Then, the second internal flow path 58 is branched midway, and one of the second internal flow path 58 and the second pipe path 46 is branched.
And the other is connected to the second switching valve 56. The second switching valve 56 has an inlet port 56a and an outlet port 56b, the second internal flow path 58 is connected to the inlet port 56a, and at the lower position J, the inlet port 56a and the outlet port 56b are connected. Shut off, upper position K
Is connected from the inlet port 56a to the outlet port 56b, the switching operation of the second switching valve 56 is operated by the hydraulic pressure in the second internal flow passage 58 in the pilot pipe 61 connected to the second internal flow passage 58. It is supposed to do. The outlet port 56b of the second switching valve 56 is connected to the tank 40 via the tank pipe 62.

With such a structure, when the operation valve 44 is set to the middle position F, the pressure oil discharged from the tank 40 by the pump 41 returns to the tank 40 through the tank pipe line 43, and the lift cylinder 49 is neutral. The fork 48 provided on the rod tip side of the lift cylinder 49 is stopped. Operate valve 44 to upper position E
When the pressure is set to 0, the pressure oil discharged from the tank 40 is
5, the first internal flow path 54, and the bottom pipe path 53 to flow into the bottom chamber 52 of the lift cylinder 49,
9, the pressure oil in the rod chamber 50 of the lift cylinder 49 is transferred to the first switching valve 5 of the actuator 47 by the rod conduit 51.
Flush to 5. At this time, when there is no load on the fork 48 and the load is small, the first switching valve 55 moves to the lower position H and the pressure oil in the rod chamber 50 of the lift cylinder 49 enters the first flow path 54 via the check valve 57. As a result, the amount of pressure oil to the bottom chamber 52 of the lift cylinder 49 is increased, and the lift speed of the lift cylinder 49 is increased. Further, when there is a load on the fork 48 and the load is large, the hydraulic pressure in the first internal flow passage 54 increases, and the pilot switching pipe 59 causes the hydraulic pressure in the first internal flow passage 54 to move the first switching valve 55 to the upper position I. The pressure oil in the rod chamber 50 of the lift cylinder 49 flows into the second switching valve 56 via the second internal flow path 58, and from the second switching valve 56 to the tank 40 via the tank line 62. Then, the lift cylinder 49 is raised at a normal speed. As a result, the fork 48 is raised at the normal speed and the high speed. When the operation valve 44 is set to the lower position G, the lift cylinder 49 descends by its own weight, and the pressure oil in the bottom chamber 52 of the lift cylinder 49 flows through the bottom pipe line 53, the first internal flow passage 54, and the first pipe line 45. Then, it flows to the operation valve 44, and then flows from the operation valve 44 to the second internal flow path 58 via the second pipe line 46. At this time, in the first switching valve 55 and the second switching valve 56, the first switching valve 55 is actuated first, and the pressure oil flowing into the second internal flow path 58 is the first. After passing through the exchange valve 55, it flows into the rod conduit 51 and flows into the rod chamber 50 of the lift cylinder 49.
The fork 48 is lowered.

[0004]

In the hydraulic circuit for the lift cylinder in the conventional cargo handling apparatus, in the actuator 47 provided between the operation valve 44 and the lift cylinder 49, the operation valve 44 is provided inside the actuator 47. A flow path connecting the bottom chamber 52 of the lift cylinder 49, a flow path connecting the operation valve 44 to the rod chamber 50 of the lift cylinder 49, a flow path connecting the rod chamber 50 of the lift cylinder 49 to the tank 40, The lift cylinder 49 has a flow path connecting from the rod chamber 50 to the bottom chamber 52, and the inside becomes complicated, and the actuator 47 has a large and complicated structure.
The entire lift cylinder hydraulic circuit becomes large in size, and there is a problem that a large space must be secured on the vehicle body side when the lift cylinder hydraulic circuit is installed in the vehicle body. Further, since the pipes are connected to the operation valve 44, the actuator 47, and the lift cylinder 49 in a complicated manner, there are problems that the number of connecting parts increases and the pressure loss in the connecting parts becomes very large. The object of the present invention is to solve these problems.

[0005]

According to the present invention, there is provided a position for supplying pressure oil discharged from a pump to a first pipe line connected to a bottom chamber of a lift cylinder, and the pressure oil discharged from the pump flowing out to a tank. And a position where the pressure oil in the first pipeline flows out to the tank, the piston of the lift cylinder is provided with a pressure in the rod chamber when the oil pressure in the rod chamber increases. A check valve that allows oil to flow to the bottom chamber is provided, and an actuator is provided between the rod chamber of the lift cylinder and the tank, and the actuator is normally closed in its internal flow path and opened by negative pressure in the rod chamber. With a suction valve that is in position, a piston portion that operates the suction valve to an open position is provided, and the piston portion is connected to a pilot line that connects to the bottom chamber of the lift cylinder,
The piston portion is operated by the hydraulic pressure in the bottom chamber.

[0006]

According to the present invention, the piston of the lift cylinder is provided with a check valve for causing the pressure oil of the rod chamber to flow to the bottom chamber when the hydraulic pressure of the rod chamber becomes high, thereby raising the rod of the lift cylinder. At this time, when there is no load on the fork and the load on the lift cylinder is small, the hydraulic pressure in the rod chamber increases in the bottom chamber and the rod chamber, the check valve is activated, and the pressure oil in the rod chamber passes through the check valve to the bottom. Flow into the chamber and increase the amount of pressure oil to the bottom chamber of the lift cylinder to accelerate the lift speed of the rod of the lift cylinder, and when there is a load on the fork and the load on the lift cylinder is large, this The hydraulic pressure in the bottom chamber of the lift cylinder increases due to the load, and the piston part of the actuator is activated, the check valve of the actuator is activated, and the internal flow path of the actuator is opened. To, the pressure oil in the rod chamber to flow through the actuator to a tank, performs an increase in the lift cylinder rod at the normal speed.

[0007]

EXAMPLE A hydraulic circuit for a lift cylinder in a cargo handling apparatus according to the present invention will be described. As shown in FIG. 1, a lift cylinder 2 that moves up and down a fork 1 is composed of a cylinder tube 3, a piston 4 and a piston rod 5, and a rod chamber 6 and a bottom chamber 7 are formed inside the cylinder tube 3. The fork 1 is provided on the tip side of the piston rod 5. In the lift cylinder 2, the piston 4 is provided with two check valves 8, and the check valve 8 has a small diameter from the upper surface (the rod chamber 6 side) to the lower surface (the bottom chamber 7 side) of the piston 4. A hole 9 and a large-diameter hole 10 are formed, a valve seat 11 is provided at a step portion between the small-diameter hole 9 and the large-diameter hole 10, a ball 12 is housed in the large-diameter hole 10, and the ball 12 is attached to a spring 13 The ring member 14 supports the spring 13 upward, and the ball 12 moves when the hydraulic pressure of a predetermined pressure or more is applied to the check valve 8 to move the pressure oil from the rod chamber 6 to the bottom chamber. It is designed to flow only in one direction. Then, the first pipe line 16 is connected to the connection portion 15 on the bottom chamber 7 side of the lift cylinder 2, and the first pipe line 16 is connected to the operation valve 17. Further, a pump pipeline 20 connected to the tank 18 via a pump 19 and a tank pipeline 21 connected to the tank 18 are provided, and the pump pipeline 20 and the tank pipeline 21 are connected to the operation valve 17. . The operation valve 17 has a pump port 17a, a tank port 17b, and a first port 17c.
The pump line 20 is connected to a, the tank line 21 is connected to the tank port 17b, and the first line 16 is connected to the first port 17c. At the middle position B, the pump port 17a and the tank port 17b are connected. Connected to the first port 17
c is blocked, and pump port 17a is in the upper position A.
To the first port 17c and the tank port 17b is blocked, and in the lower position C, the first port 17c is connected to the tank port 17b and the pump port 17a is blocked. On the other hand, the actuator 23 is welded and fixed to the side surface of the cylinder tube 3 so as to be connected to the connecting portion 22 on the rod chamber 6 side of the lift cylinder 2, and the actuator 23 is provided with an internal flow path 24 inside thereof. One end of the internal flow path 24 is connected to the connecting portion 22 on the rod chamber 6 side, and the other end of the internal flow path 24 is connected to a tank pipe line 25 connecting to the tank 18. A suction valve 26 is provided in the internal flow path 24, and the suction valve 26 includes a poppet 27 that moves up and down to open and close the internal flow path 24, and a spring 28 that pushes the poppet 27 downward. . Further, a piston portion 29 is provided below the suction valve 26, and the piston portion 29 includes a piston body 30 that moves up and down,
A spring 31 pushing the piston body 30 downward
And a ball 32 that abuts the lower portion of the piston body 30, and a pilot pipe 34 connected to a connecting portion 33 provided on the bottom chamber 7 side of the lift cylinder 2 is connected to the pilot pipe 34. The piston body 30 is moved upward by hydraulic pressure to push the poppet 27 of the suction valve 26 upward.

Next, the operating state of the lift cylinder hydraulic circuit thus constructed will be described. When the operation valve 17 is in the middle position B, as shown in FIG. 1, the pressure oil discharged from the tank 18 by the pump 19 returns to the tank 18 via the tank pipe line 21, and the lift cylinder 2 remains stopped in the neutral state. Become. As a result, the fork 1 provided on the tip side of the rod 5 of the lift cylinder 2 can be kept stopped. When the operation valve 17 is in the upper position A,
The pressure oil discharged from the tank 18 flows into the bottom chamber 7 of the lift cylinder 2 through the first pipe line 16 and raises the rod 5 of the lift cylinder 2 (the lift cylinder 2 is in an extended state). At this time, when there is no load on the fork 1 and the load is small, the piston 4 rises and the rod chamber 6 contracts, as shown in FIG. 6, the hydraulic pressure of the check valve 8 in the piston 4 is applied to a pressure higher than a predetermined pressure to push the ball 12 of the check valve 8 downward, and the pressure oil of the rod chamber 6 flows into the bottom chamber 7 through the check valve 8. As a result, the amount of pressure oil to the bottom chamber 7 of the lift cylinder 2 is increased to accelerate the rising speed of the rod 5 of the lift cylinder 2. Further, when there is a load on the fork 1 and the load is large, as shown in FIG. 3, this load increases the hydraulic pressure in the bottom chamber 7 of the lift cylinder 2, and the pilot conduit 3
The piston portion 29 of the actuator 23 is operated via 4, and the operation of the piston portion 29 is to lift the ball 32 of the piston portion 29 upward by the hydraulic pressure of the pilot conduit 34,
The piston body 30 is lifted up, the poppet 27 of the suction valve 26 is lifted up to open the internal flow path 24 of the actuator 23, and the check valve 8 provided in the piston 4 does not operate and the rod chamber 6 Actuator 2 for pressure oil
It is made to flow to the tank 18 through the internal flow path 24 and the tank line 25 of No. 3, and the rod 5 of the lift cylinder 2 is raised at a normal speed. As a result, it is possible to raise the fork 1 at a normal speed and a high speed. Control valve 1
7 when it is in the lower position C, the rod 5 of the lift cylinder 2
Is lowered by its own weight (a state in which the lift cylinder 2 contracts), and the pressure oil in the bottom chamber 7 of the lift cylinder 2 flows into the operation valve 17 via the first pipe line 16, and from the operation valve 17 via the tank pipe line 21 to the tank 18 Shed on. At this time, when there is a load on the fork 1 and the load is large, the hydraulic pressure in the bottom chamber 7 of the lift cylinder 2 increases and the pilot conduit 3
4, the piston portion 29 of the actuator 23 is operated, the poppet 27 of the suction valve 26 of the actuator 23 is lifted upward to open the internal flow path 24, and the rod chamber 6 of the lift cylinder 2 becomes negative pressure. As a result, the pressure oil flows from the tank 18 into the rod chamber 6 of the lift cylinder 2 through the tank pipe line 25 and the internal flow path 24 of the actuator 23. On the other hand, when there is no load on the fork 1 and the load is small, as shown in FIG. 5, the rod chamber 6 of the lift cylinder 2 becomes a negative pressure to suck the poppet 27 of the suction valve 26 of the actuator 23. The actuator 23
The internal flow path 24 is opened, and the pressure oil flows from the tank 18 into the rod chamber 6 of the lift cylinder 2 through the tank pipeline 25 and the internal flow path 24 of the actuator 23. As a result, the fork 1 can be lowered.

Further, as shown in FIG. 1, in the piston portion 29 of the actuator 23, the lower portion of the piston body 30 is a large-diameter disk portion 30a and the lower portion thereof is a small-diameter cylindrical portion 30b having substantially the same diameter as the ball 32. And the piston body 30 is lifted up by the oil pressure in the pilot conduit 34, the oil pressure in the large diameter disc portion 30a of the piston body 30 causes the oil pressure in the pilot conduit 34 to slightly decrease. However, since the pressure receiving area is large, the piston body 30 does not easily move downward.

With this structure, the actuator 23 is provided with the suction valve 26 and the piston portion 29, and only the internal flow path 24 connecting the rod chamber 6 of the lift cylinder 2 and the tank 18 is provided therein. It suffices to adopt a configuration having the above, and it is possible to make the configuration smaller and simpler than the conventional one. Further, in the operation valve 17, the pump port 17
The three ports of a, the tank port 17b and the first port 17c are sufficient, the number of ports can be reduced as compared with the conventional one, and the operation valve 17 can be made small and simple. Further, by making the actuator 23 and the operation valve 17 have a simple structure, it is possible to reduce the number of pipe lines connecting them, as compared with the conventional one, and reduce the pressure loss and oil leakage at each connection portion. can do.

In this embodiment, the actuator 23 is welded and fixed to the side surface of the cylinder tube 3 of the lift cylinder 2. However, the actuator 23 is provided separately from the lift cylinder 2, and the actuator 23 is provided separately. The lift cylinder 2 and the lift cylinder 2 may be connected via a conduit. Further, although two check valves 8 are provided in the piston 4 of the lift cylinder 2 in the present embodiment, one or more check valves may be provided, and a cone is used instead of the balls 12 of the check valve 8. Is also good.

[0012]

According to the lift cylinder hydraulic circuit of the cargo handling apparatus of the present invention, the actuator is provided with the suction valve and the piston portion, and the flow path connecting the rod chamber of the lift cylinder and the tank therein. By having only the structure, the actuator can be made small and simple, and the entire lift cylinder hydraulic circuit can be made small and simple. When installing the lift cylinder hydraulic circuit in the vehicle body, ,
It is not necessary to secure a large space on the vehicle body side, the installation work is facilitated, and the workability during assembly or maintenance can be improved. Also, by simplifying the structure of the actuator, the number of pipe lines in the hydraulic circuit for the lift cylinder can be reduced, and the number of operating valves, lift cylinders, and the connections between the actuator and the pipes can be reduced, and Pressure loss and oil leakage can be reduced, and the performance and safety of the lift cylinder hydraulic circuit can be improved.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram of a hydraulic circuit for a lift cylinder according to the present invention.

FIG. 2 is a circuit diagram illustrating an operating state of a hydraulic circuit for a lift cylinder according to the present invention.

FIG. 3 is a circuit diagram illustrating an operating state of a hydraulic circuit for a lift cylinder according to the present invention.

FIG. 4 is a circuit diagram illustrating an operating state of a hydraulic circuit for a lift cylinder according to the present invention.

FIG. 5 is a circuit diagram illustrating an operating state of a hydraulic circuit for a lift cylinder according to the present invention.

FIG. 6 is a schematic circuit diagram of a conventional hydraulic circuit for a lift cylinder.

[Explanation of symbols]

1 ... Fork, 2 ... Lift cylinder, 3 ... Cylinder tube, 4 ... Piston, 5 ... Piston rod, 6 ... Rod chamber, 7 ... Bottom chamber, 8 ... Check valve, 9 ... Small diameter hole,
10 ... Large diameter hole, 11 ... Valve seat, 12 ... Ball, 1
3 ... Spring, 14 ... Ring member, 15 ... Connection part, 1
6 ... First conduit, 17 ... Operating valve, 17a ... Pump port,
17b ... Tank port, 17c ... First port, 18 ... Tank, 19 ... Pump, 20 ... Pump line, 21 ... Tank line, 22 ... Connection part, 23 ... Actuator, 24 ... Internal flow path,
25 ... Tank pipe line, 26 ... Suction valve, 27 ... Poppet, 28 ... Spring, 29 ... Piston part, 30 ... Piston body, 30a ... Large diameter disc part, 30b ... Small diameter cylinder part,
31 ... Spring, 32 ... Ball, 33 ... Connection part, 34
… Pilot line, 40… Tank, 41… Pump, 42
... Pump line, 43 ... Tank line, 44 ... Control valve, 44
a ... Pump port, 44b ... Tank port, 44c ... First port, 44d ... Second port, 45 ... First pipeline, 46
... second pipeline, 47 ... actuator, 48 ... fork, 49 ... lift cylinder, 50 ... rod chamber, 51 ... rod pipeline, 5
2 ... Bottom chamber, 53 ... Bottom pipe line, 54 ... First internal flow path, 55 ... First switching valve, 55a ... First port, 55b ...
2nd port, 55c ... 3rd port, 56 ... 2nd switching valve,
56a ... inlet port, 56b ... outlet port, 57 ... check valve, 58 ... second internal flow path, 59 ... pilot line, 60 ... pilot line, 61 ... pilot line.

Claims (1)

[Claims] 1. A position for supplying the pressure oil discharged from the pump 20 to a first pipe line 16 connected to the bottom chamber 7 of the lift cylinder 2 and the pressure oil discharged from the pump 20 in the tank 1.
8 of the lift cylinder 2 and the rod chamber 6 of the lift cylinder 2.
When the hydraulic pressure in the bottom chamber 7 becomes high
A check valve 8 is installed to flow to the front lift cylinder 2
An actuator 23 is provided between the rod chamber 6 and the tank 18 of
The suction valve 2 of the actuator 23, which is normally closed in its internal flow path 24, is opened by negative pressure in the rod chamber 6.
6 is provided, and a piston part 29 for operating the suction valve 26 to the open position is provided, and a pilot pipe line 34 connected to the bottom chamber 7 of the lift cylinder 2 is connected to the piston part 29 to connect the bottom chamber 7 A hydraulic circuit for a lift cylinder in a cargo handling device, wherein the piston portion 29 is operated by hydraulic pressure.