JP2013170014A - Lifting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly perform operation while reducing shock which may occur when a lifted item is subjected to moving down operation.SOLUTION: A pilot check valve 19 having a throttle flow passage at a valve body inside a body is arranged on an oil passage between a lift cylinder 10 and a hydraulic pump motor 11. Further, an ON-OFF valve 21 is arranged on an oil passage through which a hydraulic oil circulates which has passed through the throttle flow passage. By opening the ON-OFF valve 21 upon moving down operation of a fork F, the hydraulic oil inside the lift cylinder 10 is discharged to the oil passage between the hydraulic pump motor 11 and the pilot check valve 19 through the throttle flow passage. By this means, a pressure difference between an upstream side and a downstream side of the throttle flow passage is caused, so that the valve body is operated in a direction which opens the oil passage between the lift cylinder 10 and the hydraulic pump motor 11.

Description

  The present invention relates to an elevating device that includes an elevating hydraulic cylinder and moves an elevating object up and down by hydraulic drive of the hydraulic cylinder.

  For example, forklift lifting devices described in Patent Documents 1 and 2 are known as lifting devices that lift and lower an object by hydraulic drive of a hydraulic cylinder. A lifting device for a forklift moves a fork (loading implement) as a lifting object up and down by supplying and discharging hydraulic oil to and from a hydraulic cylinder. In this type of lifting device, a switching valve that controls the flow of hydraulic oil is disposed in the hydraulic piping between the hydraulic cylinder and the hydraulic pump, and the lifting and lowering operation of the fork is performed by opening and closing the switching valve. .

  However, in the lifting device for a forklift, when the switching valve is opened to lower the fork in a state where a pressure difference is generated between the upstream side and the downstream side of the hydraulic oil flow in the switching valve, the hydraulic oil flows out. There is a risk of shock. This shock makes the operation of the fork unstable and causes a load collapse.

  Therefore, in the lifting devices of Patent Documents 1 and 2, measures are taken to solve the above problems. Specifically, in the lifting devices of Patent Documents 1 and 2, in order to eliminate the above-described pressure difference, at the start of the lowering operation, according to the pressure between the hydraulic cylinder and the switching valve for a predetermined time. The hydraulic pump is once operated so as to raise the fork.

JP 2008-63072 A JP 2008-7258 A

  However, in the elevating devices of Patent Documents 1 and 2, since the hydraulic pump is operated in the upward direction, the hydraulic cylinder may move in the upward direction. A time lag occurs before the descent operation starts.

  The present invention has been made paying attention to such problems existing in the prior art, and its purpose is to operate quickly while reducing the shock that may occur when the lifting object is lowered. An object of the present invention is to provide an elevating device that can perform the above.

  In order to solve the above-mentioned problems, the invention according to claim 1 is a lifting / lowering device that moves a lifting / lowering object by supplying / discharging hydraulic oil to / from the hydraulic cylinder, The pilot check valve that is disposed in the first oil passage between the hydraulic pump and the hydraulic cylinder and that has a throttle passage in the valve body inside the main body, and the hydraulic oil that has passed through the throttle passage circulates. An ON-OFF valve disposed in the second oil passage, and the pressurizing force of the hydraulic oil in the first oil passage acts in the direction of opening the valve body and the operation in the second oil passage The gist of the invention is that the oil pressure acts in the direction of closing the valve body, and the return path connected to the outflow side of the ON-OFF valve is connected to the hydraulic pump.

  According to this, the pressure which acts in the direction which closes the valve body of the 2nd oil way falls gradually by the operation of a pilot check valve and an ON-OFF valve. That is, the flow path through which the hydraulic oil flows for the lowering operation is prevented from being suddenly opened. Therefore, it is possible to operate quickly while reducing a shock that may occur when the lifting object is lowered.

  According to a second aspect of the present invention, in the lifting device according to the first aspect, when the pilot check valve is in a closed state, the hydraulic pump is rotated in the ascending operation direction, whereby the first oil passage in the first oil passage is provided. The gist is to reduce a pressure difference between the hydraulic cylinder side of the pilot check valve and the hydraulic pump side of the pilot check valve in the first oil passage.

  According to this, the pressure difference between the hydraulic cylinder side of the pilot check valve and the hydraulic pump side of the pilot check valve can be reduced. That is, the pressure between the pilot check valve and the hydraulic pump is increased. As a result, the shock that can occur when the pilot check valve is opened and the first oil passage is opened can be further reduced. That is, the oil passage can be opened in a more stable state. Further, since the hydraulic pump is rotated in the upward movement direction while the pilot check valve is closed, the hydraulic cylinder is prevented from operating in the upward movement direction. Therefore, it is possible to minimize the time lag from when the descending operation is instructed until when the descending operation is actually performed. As a result, the elevator can be operated quickly.

  According to a third aspect of the present invention, in the lifting device according to the second aspect, the ON-OFF valve is opened after the hydraulic pump is rotated in the upward operation direction with the ON-OFF valve closed. The gist is to make it a state.

  According to this, since the hydraulic pump is rotated in the upward movement direction when the ON-OFF valve is closed, it is possible to reduce the pressure difference between the second oil path side and the return path side connected to the ON-OFF valve. it can. As a result, it is possible to reduce a shock that may occur when the return path is opened by opening the ON-OFF valve. That is, the oil passage can be opened in a more stable state.

  According to a fourth aspect of the present invention, in the elevating device according to the first or second aspect, the ON-OFF valve is connected from the pilot check valve to the oil path between the pilot check valve and the ON-OFF valve. The gist of the invention is that a check valve is provided so as to allow the hydraulic fluid to flow through.

  According to this, since the check valve is disposed in the second oil passage, even when the hydraulic pump is temporarily rotated in the upward operation direction when the hydraulic cylinder is moved downward, the ON-OFF valve at that time Can be opened. That is, the action of the check valve suppresses the pilot check valve from opening and suppresses the hydraulic cylinder from moving up. Therefore, the lowering operation can be started more quickly than when the ON-OFF valve is opened when the hydraulic pump is rotated in the upward operation direction and then in the downward operation direction.

  According to a fifth aspect of the present invention, in the elevating device according to any one of the first to third aspects, the first oil passage is interposed in the first oil passage through the throttle passage during the raising operation of the hydraulic cylinder. Ascending oil passage for circulating hydraulic oil through the second oil passage, and ascending oil passage for circulating hydraulic oil through the throttle passage during the downward movement of the hydraulic cylinder When the hydraulic cylinder is raised, the ON-OFF valve is opened.

  According to this, the ascending oil passage for circulating hydraulic oil to the hydraulic cylinder during the ascending operation is connected to the throttle passage side of the pilot check valve. For this reason, even if the hydraulic pump is rotated in the ascending operation direction during the descending operation, the hydraulic oil can be reliably prevented from flowing to the hydraulic cylinder side when the ON-OFF valve is closed. . That is, it is possible to prevent the hydraulic cylinder from moving in the upward movement direction. Therefore, it is possible to minimize the time lag from when the descending operation is instructed until when the descending operation is actually performed. As a result, the elevator can be operated quickly.

  ADVANTAGE OF THE INVENTION According to this invention, it can be made to operate | move rapidly, reducing the shock which may arise when operating a raising / lowering object.

The circuit diagram of the raising / lowering apparatus of 1st Embodiment. The schematic diagram which showed the internal structure of the pilot check valve typically. The circuit diagram of the raising / lowering apparatus of 2nd Embodiment. The circuit diagram of the raising / lowering apparatus of 3rd Embodiment.

(First embodiment)
DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is embodied in a lifting device provided with a lift cylinder that lifts and lowers a fork of a forklift will be described with reference to FIGS.

  A fork F as a cargo handling tool (lifting object) arranged in front of the forklift moves up and down by operating the lift lever L provided at the driver's seat and expanding and contracting the lift cylinder 10 as a hydraulic cylinder.

Hereinafter, a hydraulic control mechanism for operating the lift cylinder 10 in the present embodiment will be described with reference to FIG.
A hydraulic pump motor 11 that functions as a hydraulic pump and a hydraulic motor is connected to the main pipe K having a closed circuit configuration, and a hydraulic oil supply / discharge path to the lift cylinder 10 is formed in the main pipe K. A pipe K1 connected to the bottom chamber 10a of the lift cylinder 10 is connected. The hydraulic pump motor 11 is configured to be bi-directionally rotatable. The main pipe K is connected to the flow ports 11 a and 11 b of the hydraulic pump motor 11. The flow ports 11a and 11b of the hydraulic pump motor 11 become a suction port (inlet) or a discharge port (outlet) depending on the flow direction of the hydraulic oil.

  The hydraulic pump motor 11 is connected to a lift motor (rotating electric machine) 12 that functions as an electric motor and a generator. The lift motor 12 functions as an electric motor by rotating the rotor by energizing a stator coil (not shown), and functions as a generator by generating electric power in the stator coil by rotating the rotor. In the present embodiment, the lift motor 12 is an electric motor when the hydraulic pump motor 11 is operated as a hydraulic pump, and is a generator when the hydraulic pump motor 11 is operated as a hydraulic motor.

  The main pipe K is connected to a supply pipe K2 for circulating hydraulic oil pumped up from the oil tank 13 by the operation of the hydraulic pump motor 11 when the lift cylinder 10 is moved up. A check valve (check valve) 14 for preventing a back flow from the main pipe K to the oil tank 13 is provided. The main pipe K is connected to a discharge pipe K3 for circulating hydraulic oil returned to the oil tank 13 by the operation of the hydraulic pump motor 11 when the lift cylinder 10 is lowered. A check valve (check valve) 15 for preventing a back flow from the oil tank 13 to the main pipe K is provided. Further, a filter 16 is disposed between the oil tank 13 and the check valve 15 in the discharge pipe K3.

  The main pipe K has a check valve (a check valve) for preventing a backflow from the main pipe K connected to the flow port 11a of the hydraulic pump motor 11 to the main pipe K connected to the flow port 11b of the hydraulic pump motor 11. Valve) 17 is provided. The check valve 17 is disposed on an oil passage between a flow port 11 a that can be a discharge port of the hydraulic pump motor 11 and an oil tank 13 that stores hydraulic oil. The check valve 17 allows the hydraulic oil to flow from the oil tank 13 side to the main pipe K on the flow port 11 b side of the hydraulic pump motor 11. The main pipe K is provided with a relief valve 18 for preventing a pressure increase.

  A pilot check valve 19 is disposed in the pipe K <b> 1 connected to the bottom chamber 10 a of the lift cylinder 10. In the present embodiment, the pilot check valve 19 is disposed on the first oil passage constituted by the main pipe K from the connection portion of the pipe K1 and the pipe K1 to the flow port 11a of the hydraulic pump motor 11. As schematically shown in FIG. 2, the pilot check valve 19 of the present embodiment has a structure having a throttle channel 19b in a valve body 19a inside the main body. The throttle channel 19b communicates the pipe K1 between the pilot check valve 19 and the bottom chamber 10a of the lift cylinder 10 and the spring chamber 19c inside the main body. The throttle channel 19b is formed with a large-diameter channel 19d that opens toward the spring chamber 19c, and is formed so as to penetrate from the peripheral surface of the valve body 19a toward the large-diameter channel 19d and has a smaller diameter than the large-diameter channel 19d. And a small-diameter channel 19e.

  The pilot check valve 19 is discharged from the flow port 11a serving as a discharge port by the operation of the hydraulic pump motor 11, and the valve body 19a receives the pressure of the hydraulic oil flowing through the main pipe K to operate. The valve is in an open state in which hydraulic fluid is circulated to the lift cylinder 10 side. That is, the pressurizing force of the hydraulic oil in the first oil passage described above acts in a direction to open the valve body 19 a of the pilot check valve 19. In addition, when the hydraulic pump motor 11 is stopped and the flow of hydraulic oil is stopped, the pilot check valve 19 in the open state is operated by the valve body 19a receiving the urging force of the spring in the spring chamber 19c. State. Further, when the difference between the pressure on the pipe K1 side between the pilot check valve 19 and the lift cylinder 10 and the pressure on the spring chamber 19c reaches a predetermined pressure, the pilot check valve 19 receives the differential pressure by the valve body 19a. By operating, the valve is opened. In this open state, the pilot check valve 19 causes the hydraulic oil discharged from the bottom chamber 10a of the lift cylinder 10 to flow to the main pipe K (hydraulic pump motor 11) side. That is, the pilot check valve 19 is opened with the differential pressure as the pressure for operating the valve body 19a (pilot pressure).

  A pipe K4 as a second oil passage is connected to the spring chamber 19c of the pilot check valve 19, and an ON-OFF valve 21 is disposed in the pipe K4 via a filter 20. The pressurizing force of the hydraulic oil in the pipe K4 as the second oil passage acts in a direction in which the valve body 19a of the pilot check valve 19 is closed. The channel diameter when the ON-OFF valve 21 is opened is set larger than the channel diameter of the small-diameter channel 19e. The ON-OFF valve 21 is connected to a pipe K5 as a return path on the outflow side of the ON-OFF valve 21. The pipe K5 is an oil path between the hydraulic pump motor 11 and the pilot check valve 19. It is connected to the main pipe K connected to. As a result, the hydraulic fluid flowing through the pilot check valve 19 → the pipe K4 → the ON-OFF valve 21 → the pipe K5 is returned to the flow port 11a of the hydraulic pump motor 11 through the main pipe K. At this time, the flow port 11a of the hydraulic pump motor 11 serves as a hydraulic oil inflow port.

Next, the configuration of the control unit S of the hydraulic control mechanism will be described.
A potentiometer Lm that detects the operation amount of the lift lever L is electrically connected to the control unit S. And the control part S controls the rotation speed of the motor 12 for a lift based on the detection signal from the potentiometer Lm based on the operation amount of the lift lever L. FIG. Further, the control unit S controls the opening and closing of the ON-OFF valve 21.

  In addition, an inverter S1 is electrically connected to the control unit S. The lift motor 12 is supplied with power from the battery BT mounted on the forklift via the inverter S1. The electric power generated by the lift motor 12 is accumulated in the battery BT via the inverter S1. The forklift according to the present embodiment is a battery-type forklift that travels by supplying electric power stored in the battery BT to a traveling motor serving as a prime mover.

Hereinafter, the operation of the hydraulic control mechanism of the present embodiment will be described.
First, the raising operation of the fork F will be described.
When the fork F is moved up, hydraulic oil is supplied to the bottom chamber 10 a of the lift cylinder 10. Therefore, the control unit S controls the rotation speeds of the hydraulic pump motor 11 and the lift motor 12 so as to operate at an instruction speed corresponding to the operation amount of the lift lever L. As a result, the hydraulic oil in the oil tank 13 pumped up by the hydraulic pump motor 11 flows through the main pipe K to the pilot check valve 19, and is supplied to the bottom chamber 10a by opening the pilot check valve 19. The As a result, the fork F moves up by the extension of the lift cylinder 10. The hydraulic pump motor 11 during the ascending operation operates as a hydraulic pump. And the control part S stops rotation of the hydraulic pump motor 11 and the motor 12 for a lift, when complete | finishing a raise operation | movement. As a result, the pilot check valve 19 is closed by the biasing force of the spring in the spring chamber 19c. Note that the ON-OFF valve 21 during the ascending operation is closed. In addition, after the pilot check valve 19 is closed, the pressure in the main pipe K between the lift cylinder 10 and the pilot check valve 19 and the pressure in the main pipe K between the hydraulic pump motor 11 and the pilot check valve 19 are A pressure difference can occur between the two. More specifically, the pressure in the main pipe K between the lift cylinder 10 and the pilot check valve 19 is higher than the pressure in the main pipe K between the hydraulic pump motor 11 and the pilot check valve 19. Yes.

Next, the lowering operation of the fork F will be described.
When lowering the fork F, the hydraulic oil is discharged from the bottom chamber 10a of the lift cylinder 10. In the hydraulic control mechanism of the present embodiment, a pilot check valve 19 is disposed on an oil passage through which hydraulic oil discharged from the bottom chamber 10a is circulated to the oil tank 13 through the hydraulic pump motor 11. The pilot check valve 19 opens freely when the hydraulic oil is circulated from the main pipe K side as in the ascending operation, but the hydraulic oil is supplied from the bottom chamber 10a side (the pipe K1 side) as in the descending operation. In the case of circulation, the flow is shut off and the valve is opened by applying a predetermined pilot pressure.

  In the present embodiment, the controller S lifts the hydraulic pump motor 11 so as to rotate in the upward operation direction before the ON-OFF valve 21 is opened, that is, in a state where the ON-OFF valve 21 is closed. The motor 12 is driven. The upward movement direction is a direction in which hydraulic oil is circulated to the pilot check valve 19 side via the main pipe K. When the hydraulic pump motor 11 is thus rotated in the upward movement direction, the pressure in the main pipe K between the hydraulic pump motor 11 and the pilot check valve 19 is increased. Furthermore, in this embodiment, since the piping K5 of the ON-OFF valve 21 is connected to the main piping K, the pressure in the piping K5 is also increased.

  In the present embodiment, the control unit S rotates the hydraulic pump motor 11 in the ascending operation direction at a constant rotation speed and for a predetermined rotation time. The rotation time is a fixed time calculated in advance by simulation, and varies depending on the type of forklift. The rotation time is determined as a time during which the pressure in the main pipe K can be increased so that the driver or the like does not feel a shock when the pilot check valve 19 is opened along with the lowering operation.

  And if the control part S rotates the hydraulic pump motor 11 to a raise operation direction during rotation time, while opening the ON-OFF valve 21, it will stop the hydraulic pump motor 11. FIG. When the ON-OFF valve 21 is opened, the hydraulic oil between the bottom chamber 10a and the pilot check valve 19 passes through the throttle passage 19b formed in the valve body 19a of the pilot check valve 19 and then spring chamber 19c → piping K4 → It flows in the order of the ON-OFF valve 21 → pipe K5. That is, when the ON-OFF valve 21 is opened, the flow path for the hydraulic oil to return from the main pipe K to the flow port 11a of the hydraulic pump motor 11 through the pipe K5 is opened. Further, the hydraulic fluid that has flowed to the hydraulic pump motor 11 also flows to the oil tank 13 side due to internal leakage (internal leakage) of the hydraulic pump motor 11. In this embodiment, the pressure difference between the pipe K4 on the upstream side of the ON-OFF valve 21 and the pipe K5 side on the downstream side is increased by increasing the pressure in the pipe K5 before the ON-OFF valve 21 is opened. Has been resolved. This reduces the occurrence of shock when the ON-OFF valve 21 is opened.

  On the other hand, the pilot check valve 19 has a spring chamber 19c on the upstream side of the throttle channel 19b and on the downstream side of the throttle channel 19b due to pressure loss caused by the hydraulic oil passing through the throttle channel 19b. Differential pressure is generated on the side. Specifically, the pressure on the spring chamber 19c side is lower than the pressure on the pipe K1 side. Further, in the pilot check valve 19, when the ON-OFF valve 21 is opened, the flow rate passing through the throttle channel 19b gradually increases due to internal leakage of the hydraulic pump motor 11. In other words, when the flow rate gradually increases, the pressure of the hydraulic oil in the pipe K4 as the second oil passage acting in the direction of closing the valve body 19a of the pilot check valve 19 also gradually decreases. . When the flow rate passing through the throttle channel 19b exceeds a certain amount, the pilot check valve 19 opens due to a pressure difference between the upstream side and the downstream side of the throttle channel 19b. That is, the pilot check valve 19 does not open rapidly due to the action of the ON-OFF valve 21. When the pilot check valve 19 is opened, the flow path for the hydraulic oil in the bottom chamber 10a of the lift cylinder 10 to return from the main pipe K to the flow port 11a of the hydraulic pump motor 11 through the pipe K1 is opened. In the present embodiment, since the hydraulic pump motor 11 is rotated in the ascending operation direction before the ON-OFF valve 21 is opened, the pressure inside the pipe K5 is increased. Thereby, after the ON-OFF valve 21 is opened, the pressure on the side where the working oil flows from the pilot check valve 19 to the pipe K5 is increased. The pressure difference between the upstream side and the downstream side of 19b does not increase rapidly. That is, the pilot check valve 19 does not open suddenly. As a result, the occurrence of shock when the pilot check valve 19 is opened is reduced.

  After the pilot check valve 19 is opened, the control unit S controls the rotational speeds of the hydraulic pump motor 11 and the lift motor 12 so that the pilot check valve 19 is operated at an instruction speed corresponding to the operation amount of the lift lever L. That is, the control unit S drives the lift motor 12 so that the hydraulic pump motor 11 rotates in the descending operation direction. The downward movement direction is a direction in which the hydraulic oil is circulated to the hydraulic pump motor 11 side through the main pipe K. Further, the hydraulic oil discharged from the bottom chamber 10 a of the lift cylinder 10 flows through the main pipe K and the pipe K 5 and is sucked into the flow port 11 a of the hydraulic pump motor 11. At this time, the circulation port 11a functions as a suction port. The hydraulic pump motor 11 operates as a hydraulic motor using the hydraulic oil discharged from the bottom chamber 10a as a driving force. As a result, the lift motor 12 functions as a generator, and the electric power generated by the lift motor 12 is stored in the battery BT via the inverter S1. That is, when the fork F is lowered, a regenerative operation is performed.

  And when stopping a descent | fall operation | movement, the control part S closes the ON-OFF valve 21. FIG. Thereby, the pilot check valve 19 closes the flow path when the valve body 19a is pushed in the direction of closing the flow path by the cylinder pressure of the lift cylinder 10.

  If the diameter (minimum diameter) of the small-diameter channel 19e constituting the throttle channel 19b is too large with respect to the opening degree of the ON-OFF valve 21, a pressure difference occurs between the upstream side and the downstream side of the throttle channel 19b. Therefore, the valve body 19a does not open. On the other hand, if the diameter (minimum diameter) of the small-diameter channel 19e is too small, the pressure difference between the upstream side and the downstream side of the throttle channel 19b becomes too large, and the valve element 19a is opened at once. Therefore, the diameter (minimum diameter) of the small-diameter channel 19e is set to a diameter that can cause the pressure difference to open the valve body 19a and is moderate in consideration of the opening degree of the ON-OFF valve 21. Is set to a suitable diameter. Further, the opening degree of the ON-OFF valve 21 is smaller than the opening degree of the pilot check valve 19.

Therefore, according to the present embodiment, the following effects can be obtained.
(1) The operation of the pilot check valve 19 and the ON-OFF valve 21 restricts the flow rate of the hydraulic oil flowing through the pipe K1 and the main pipe K to the hydraulic pump motor 11 during the lowering operation. That is, the flow path through which the hydraulic oil flows for the lowering operation is prevented from being suddenly opened. Therefore, it is possible to reduce a shock that may occur when the lifting object (fork F) is lowered.

  (2) The hydraulic pump motor 11 is rotated in the upward operation direction when the pilot check valve 19 and the ON-OFF valve 21 are closed. For this reason, even if hydraulic fluid is sent out from the main pipe K to the pilot check valve 19, the pilot check valve 19 can be prevented from opening. That is, it is possible to suppress the lift cylinder 10 from moving in the upward direction. Therefore, it is possible to minimize the time lag from when the descending operation is instructed until when the descending operation is actually performed. As a result, the elevator (fork F) can be operated quickly.

  (3) The pipe K5 as the return path is connected to the main pipe K, and the hydraulic oil that has circulated through the pipe K5 is circulated from the main pipe K to the hydraulic pump motor 11. For this reason, the hydraulic oil that has circulated through the pipe K <b> 5 can be used for the regenerative operation of the hydraulic pump motor 11. Therefore, regeneration can be performed efficiently.

  (4) When the pilot check valve 19 is closed, the hydraulic pump motor 11 is rotated in the upward movement direction. Thereby, the pressure difference between the pipe K1 side connecting the pilot check valve 19 and the bottom chamber 10a and the main pipe K side connecting the pilot check valve 19 and the hydraulic pump motor 11 can be eliminated (reduced). As a result, the shock that can occur when the pilot check valve 19 is opened to open the first oil passage (the pipe K1 and the main pipe K) can be further reduced. That is, the oil passage can be opened in a more stable state.

  (5) When the ON-OFF valve 21 is closed, the hydraulic pump motor 11 is rotated in the upward movement direction. Thereby, the pressure difference between the pipe K4 and the pipe K5 connected to the ON-OFF valve 21 can be eliminated (reduced). As a result, it is possible to reduce a shock that may occur when the ON-OFF valve 21 is opened and the return path (pipe K5) is opened. That is, the flow path can be opened in a more stable state.

  (6) Also, the hydraulic pump motor 11 is rotated in the upward movement direction to increase the pressure in the pipe K5. Thereby, even if the ON-OFF valve 21 is opened, the pressure difference between the upstream side and the downstream side of the throttle channel 19b does not increase rapidly. That is, the pilot check valve 19 does not open suddenly. As a result, the occurrence of shock when the pilot check valve 19 is opened can be further reduced. That is, the oil passage can be opened in a more stable state.

  (7) The ON-OFF valve 21 is adopted. For this reason, compared with the case where an electromagnetic proportional valve is arrange | positioned between the pilot check valve 19 and the piping K5, the increase in the cost of a hydraulic control mechanism can be suppressed. Further, since the ON-OFF valve 21 is a valve that can take two positions of open and closed, the control can be simplified as compared with the electromagnetic proportional valve.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG.
Note that, in the embodiments described below, the same reference numerals are given to the same configurations as those of the embodiments already described, and redundant descriptions thereof are omitted or simplified.

  In the hydraulic control mechanism of the present embodiment, the first oil path between the lift cylinder 10 and the hydraulic pump motor 11 is a pipe K1a through which hydraulic oil flows mainly from the hydraulic pump motor 11 toward the lift cylinder 10 during the ascending operation. , And a piping K1b through which hydraulic fluid flows mainly from the lift cylinder 10 toward the hydraulic pump motor 11 during the lowering operation. In the present embodiment, the pipe K1a is an ascending oil path, and the pipe K1b is a descending oil path. A check valve C1, a pilot check valve 19, and a check valve C2 are sequentially arranged in the pipe K1a along the direction in which the hydraulic oil is directed from the hydraulic pump motor 11 to the lift cylinder 10. The pipe K1a is disposed so that the check valves C1 and C2 allow the hydraulic oil to flow in the direction from the hydraulic pump motor 11 toward the lift cylinder 10, so that the hydraulic oil flows during the ascending operation. Configured as an oil passage. In addition, a check valve C3, a pilot check valve 19, and a check valve C4 are sequentially arranged in the pipe K1b along the direction in which the hydraulic oil flows from the lift cylinder 10 to the hydraulic pump motor 11. The pipe K1b is arranged so that the check valves C3 and C4 allow the hydraulic oil to flow in the direction from the lift cylinder 10 to the hydraulic pump motor 11, so that the hydraulic oil flows during the lowering operation. Configured as an oil passage. In the hydraulic control mechanism of this embodiment, the flow direction of the hydraulic oil is controlled by disposing a plurality of (four in the embodiment) check valves C1 to C4 on the first oil passage. Further, in the hydraulic control mechanism of the present embodiment, the pipes K1a and K1b are connected to the pilot check valve so that the hydraulic oil flows into the throttle flow path 19b side of the pilot check valve 19 in both the ascending operation and the descending operation. 19 is connected.

  Further, in the hydraulic control mechanism of the present embodiment, a pipe K4 as a second oil passage is connected to the spring chamber 19c of the pilot check valve 19 as in the first embodiment, and the pipe K4 is turned on. A -OFF valve 21 is provided. Similarly to the first embodiment, a pipe K5 as a return path is connected to the ON-OFF valve 21 on the outflow side of the ON-OFF valve 21, and the pipe K5 is connected to the hydraulic pump motor 11. It is connected to a main pipe K connected to the circulation port 11a. As a result, the hydraulic fluid flowing through the pilot check valve 19 → the pipe K4 → the ON-OFF valve 21 → the pipe K5 is returned to the flow port 11a of the hydraulic pump motor 11 through the main pipe K. At this time, the flow port 11a of the hydraulic pump motor 11 serves as a hydraulic oil inflow port.

Hereinafter, the operation of the hydraulic control mechanism of the present embodiment will be described.
First, the raising operation of the fork F will be described.
When the fork F is moved up, hydraulic oil is supplied to the bottom chamber 10 a of the lift cylinder 10. Therefore, the control unit S controls the rotation speeds of the hydraulic pump motor 11 and the lift motor 12 so as to operate at an instruction speed corresponding to the operation amount of the lift lever L. In the present embodiment, the control unit S opens the ON-OFF valve 21 in order to distribute the hydraulic oil pumped up by the hydraulic pump motor 11 to the lift cylinder 10. As a result, the hydraulic oil in the oil tank 13 pumped up by the hydraulic pump motor 11 flows through the main pipe K to the pilot check valve 19, and is supplied to the bottom chamber 10a by opening the pilot check valve 19. The That is, in this embodiment, the differential pressure between the pipe K1a on the upstream side of the throttle channel 19b and the spring chamber 19c on the downstream side of the throttle channel 19b, which can be generated by the hydraulic oil passing through the throttle channel 19b. To open the pilot check valve 19. This differential pressure can be generated by opening the ON-OFF valve 21.

  When the hydraulic oil flows into the bottom chamber 10a of the lift cylinder 10 by opening the pilot check valve 19, the lift cylinder 10 extends and the fork F moves up. The hydraulic pump motor 11 during the ascending operation operates as a hydraulic pump. Then, when ending the ascending operation, the controller S stops the rotation of the hydraulic pump motor 11 and the lift motor 12 and closes the ON-OFF valve 21. As a result, the pilot check valve 19 is closed by the biasing force of the spring in the spring chamber 19c.

Next, the lowering operation of the fork F will be described.
When lowering the fork F, the hydraulic oil is discharged from the bottom chamber 10a of the lift cylinder 10. In this embodiment, the controller S raises the hydraulic pump motor 11 before opening the ON-OFF valve 21, that is, in a state where the ON-OFF valve 21 is closed, as in the first embodiment. The lift motor 12 is driven so as to rotate in the operation direction. Thus, when the hydraulic pump motor 11 is rotated in the upward movement direction, the pressure in the pipe K1a between the hydraulic pump motor 11 and the pilot check valve 19 is increased. Furthermore, in this embodiment, the pressure inside the pipe K5 is also increased. As in the first embodiment, the control unit S rotates the hydraulic pump motor 11 in the ascending operation direction at a constant rotation speed and for a predetermined rotation time. In the present embodiment, the hydraulic oil pumped up by the hydraulic pump motor 11 when rotating in the upward operation direction flows through the throttle channel 19b of the pilot check valve 19. However, since the ON-OFF valve 21 is closed, the pilot check valve 19 is kept closed. That is, the hydraulic oil does not flow to the lift cylinder 10.

  And the control part S will open the ON-OFF valve 21, if the hydraulic pump motor 11 is rotated to a raise operation direction during rotation time. When the ON-OFF valve 21 is opened, the hydraulic oil between the bottom chamber 10a and the pilot check valve 19 passes through the pipe K1b through the throttle channel 19b → the spring chamber 19c → the pipe K4 → the ON-OFF valve 21 → the pipe K5. Circulate in order. That is, when the ON-OFF valve 21 is opened, the flow path for the hydraulic oil to return from the main pipe K to the flow port 11a of the hydraulic pump motor 11 through the pipe K5 is opened. And in this embodiment, generation | occurrence | production of the shock at the time of opening the ON-OFF valve 21 is reduced because the inside of piping K5 is pressure | voltage-risen similarly to 1st Embodiment.

  Also in this embodiment, the differential pressure between the pipe K1b on the upstream side of the throttle channel 19b and the spring chamber 19c on the downstream side of the throttle channel 19b, which can be generated by the hydraulic oil passing through the throttle channel 19b. To open the pilot check valve 19. This differential pressure can be generated by opening the ON-OFF valve 21. In the present embodiment as well, the second oil passage acting in the direction of closing the valve body 19a of the pilot check valve 19 is obtained by gradually increasing the flow rate passing through the throttle passage 19b due to the internal leak of the hydraulic pump motor 11. The pressure of the hydraulic oil in the pipe K4 also gradually decreases. When the pilot check valve 19 is opened, the flow path for the hydraulic oil in the bottom chamber 10a of the lift cylinder 10 to return from the main pipe K to the flow port 11a of the hydraulic pump motor 11 through the pipe K1b is opened. Also in this embodiment, since the hydraulic pump motor 11 is rotated in the ascending operation direction before the ON-OFF valve 21 is opened, the pressure inside the pipe K5 is increased. Thereby, after the ON-OFF valve 21 is opened, the pressure on the side where the working oil flows from the pilot check valve 19 to the pipe K5 is increased. The pressure difference between the upstream side and the downstream side of 19b does not increase rapidly. That is, the pilot check valve 19 does not open suddenly. As a result, the occurrence of shock when the pilot check valve 19 is opened is reduced.

  After the pilot check valve 19 is opened, the control unit S controls the rotational speeds of the hydraulic pump motor 11 and the lift motor 12 so that the pilot check valve 19 is operated at an instruction speed corresponding to the operation amount of the lift lever L. Further, the hydraulic oil discharged from the bottom chamber 10 a of the lift cylinder 10 flows through the piping K 1 b and the piping K 5 and is sucked into the distribution port 11 a of the hydraulic pump motor 11. At this time, the circulation port 11a functions as a suction port. The hydraulic pump motor 11 operates as a hydraulic motor using the hydraulic oil discharged from the bottom chamber 10a as a driving force. As a result, the lift motor 12 functions as a generator, and the electric power generated by the lift motor 12 is stored in the battery BT via the inverter S1. That is, when the fork F is lowered, a regenerative operation is performed.

  And when stopping a descent | fall operation | movement, the control part S closes the ON-OFF valve 21. FIG. Thereby, the pilot check valve 19 closes the flow path when the valve body 19a is pushed in the direction of closing the flow path by the cylinder pressure of the lift cylinder 10.

Therefore, according to this embodiment, in addition to the effects (1) to (7) of the first embodiment, the following effects can be obtained.
(8) A pipe K1a for circulating hydraulic oil to the lift cylinder 10 during the ascending operation is connected to the throttle flow path 19b side of the pilot check valve 19. For this reason, even if the hydraulic pump motor 11 is rotated in the ascending operation direction during the descending operation, when the ON-OFF valve 21 is closed, the hydraulic oil is reliably prevented from flowing to the lift cylinder 10 side. can do. That is, it is possible to prevent the lift cylinder 10 from moving in the upward movement direction. Therefore, it is possible to minimize the time lag from when the descending operation is instructed until when the descending operation is actually performed. As a result, the elevator (fork F) can be operated quickly.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG.
In the hydraulic control mechanism of the present embodiment, a check valve C5 is provided in a pipe K4 between the pilot check valve 19 and the ON-OFF valve 21. The check valve C5 is disposed so as to allow the flow of hydraulic oil in the direction from the pilot check valve 19 toward the ON-OFF valve 21. Further, in the hydraulic control mechanism of the present embodiment, a throttle 22 is disposed in the pipe K <b> 1 between the hydraulic pump motor 11 and the pilot check valve 19.

Hereinafter, the operation of the hydraulic control mechanism of the present embodiment will be described.
In addition, since the effect | action at the time of raising operation | movement of the fork F is the same as 1st Embodiment, the overlapping description is abbreviate | omitted and the effect | action at the time of descent | fall operation | movement is demonstrated below.

  In the present embodiment, the control unit S drives the lift motor 12 so that the hydraulic pump motor 11 rotates in the upward operation direction with the ON-OFF valve 21 opened. When the hydraulic pump motor 11 is thus rotated in the upward movement direction, the pressure in the pipe K1 between the hydraulic pump motor 11 and the pilot check valve 19 is increased. Furthermore, in this embodiment, the pressure inside the pipe K5 is also increased. At this time, in the hydraulic control mechanism of the present embodiment, the ON-OFF valve 21 is opened, but the pilot check valve 19 is kept closed by the action of the check valve C5. That is, the hydraulic oil does not flow to the lift cylinder 10. As in the first embodiment, the control unit S rotates the hydraulic pump motor 11 in the ascending operation direction at a constant rotation speed and for a predetermined rotation time.

  After the rotation time elapses, the hydraulic oil between the bottom chamber 10a and the pilot check valve 19 passes through the throttle channel 19b of the pilot check valve 19 and the spring chamber 19c → pipe K4 (check valve C5) → ON-OFF. It flows in the order of valve 21 → pipe K5. That is, when the ON-OFF valve 21 is opened, the flow path for the hydraulic oil to return from the main pipe K to the flow port 11a of the hydraulic pump motor 11 through the pipe K5 is opened. And in this embodiment, generation | occurrence | production of the shock at the time of opening the ON-OFF valve 21 is reduced because the inside of piping K5 is pressure | voltage-risen similarly to 1st Embodiment.

  In this embodiment, the differential pressure between the pipe K1 on the upstream side of the throttle channel 19b and the spring chamber 19c on the downstream side of the throttle channel 19b can be generated by the hydraulic oil passing through the throttle channel 19b. To open the pilot check valve 19. This differential pressure can be generated by opening the ON-OFF valve 21. In the present embodiment as well, the second oil passage acting in the direction of closing the valve body 19a of the pilot check valve 19 is obtained by gradually increasing the flow rate passing through the throttle passage 19b due to the internal leak of the hydraulic pump motor 11. The pressure of the hydraulic oil in the pipe K4 also gradually decreases. When the pilot check valve 19 is opened, the flow path for the hydraulic oil in the bottom chamber 10a of the lift cylinder 10 to return from the main pipe K to the flow port 11a of the hydraulic pump motor 11 through the pipe K1 is opened. Also in this embodiment, since the hydraulic pump motor 11 is rotated in the upward movement direction, the pressure inside the pipe K5 is increased. As a result, the pressure on the side where the hydraulic oil flows from the pilot check valve 19 to the pipe K5 is increased, so that the pressure difference between the upstream side and the downstream side of the throttle channel 19b does not suddenly increase. That is, the pilot check valve 19 does not open suddenly. As a result, the occurrence of shock when the pilot check valve 19 is opened is reduced.

  After the pilot check valve 19 is opened, the control unit S controls the rotational speeds of the hydraulic pump motor 11 and the lift motor 12 so that the pilot check valve 19 is operated at an instruction speed corresponding to the operation amount of the lift lever L. Further, the hydraulic oil discharged from the bottom chamber 10 a of the lift cylinder 10 flows through the piping K <b> 1 and the piping K <b> 5 and is sucked into the distribution port 11 a of the hydraulic pump motor 11. At this time, the circulation port 11a functions as a suction port. The hydraulic pump motor 11 operates as a hydraulic motor using the hydraulic oil discharged from the bottom chamber 10a as a driving force. As a result, the lift motor 12 functions as a generator, and the electric power generated by the lift motor 12 is stored in the battery BT via the inverter S1. That is, when the fork F is lowered, a regenerative operation is performed.

  And when stopping a descent | fall operation | movement, the control part S closes the ON-OFF valve 21. FIG. Thereby, the pilot check valve 19 closes the flow path when the valve body 19a is pushed in the direction of closing the flow path by the cylinder pressure of the lift cylinder 10.

Therefore, according to this embodiment, in addition to the effects (1) to (7) of the first embodiment, the following effects can be obtained.
(9) A check valve C5 is provided in the pipe K4. Thereby, even when the hydraulic pump motor 11 is once rotated in the upward operation direction when the lift cylinder 10 is moved downward, the ON-OFF valve 21 can be opened at that time. That is, the action of the check valve C5 suppresses the pilot check valve 19 from opening and suppresses the lift cylinder 10 from moving up. Therefore, when the hydraulic pump motor 11 is rotated in the upward operation direction and then in the downward operation direction, the downward operation can be started more quickly than when the ON-OFF valve 21 is opened.

In addition, you may change the said embodiment as follows.
In each embodiment, the lowering operation may be performed without rotating the hydraulic pump motor 11 in the upward operation direction. Even in this case, after the ON-OFF valve 21 is opened, the hydraulic pump motor 11 gradually rotates in the lowering operation direction, so that a shock that may occur when the lowering operation is performed can be sufficiently reduced.

In each embodiment, the arrangement and shape of the throttle channel 19b formed in the valve body 19a may be changed.
O The hydraulic control mechanism of each embodiment is not limited to a forklift, and can be applied as long as the descent operation is performed by its own weight. For example, you may apply to a hydraulic elevator etc.

  In each embodiment, a pressure sensor or a load sensor that detects the cylinder pressure of the lift cylinder 10 may be provided, and the hydraulic pump motor 11 may be moved up during the lowering operation based on the detection results of these sensors.

In the third embodiment, the check valve C5 may be disposed in the throttle channel 19b of the pilot check valve 19.
In each embodiment, after rotating the hydraulic pump motor 11 in the ascending operation direction for the rotation time, the hydraulic pump motor 11 is rotated so that the rotational speed of the hydraulic pump motor 11 gradually increases in the descending operation direction. Also good. Even with this configuration, the flow rate passing through the throttle channel 19b can be gradually increased. That is, the applied pressure of the hydraulic oil in the pipe K4 as the second oil passage acting in the direction of closing the valve body 19a of the pilot check valve 19 can be gradually reduced.

  DESCRIPTION OF SYMBOLS 10 ... Lift cylinder, 11 ... Hydraulic pump motor, 19 ... Pilot check valve, 19a ... Valve body, 19b ... Restriction flow path, 21 ... ON-OFF valve, C5 ... Check valve, K ... Main piping, K1, K4 ... Piping , K5 ... Return road.

Claims (5)

In the lifting device that moves the lifting object up and down by supplying and discharging hydraulic oil to and from the hydraulic cylinder,
A hydraulic pump for supplying hydraulic oil to the hydraulic cylinder;
A pilot check valve disposed in a first oil passage between the hydraulic pump and the hydraulic cylinder and having a throttle channel in a valve body inside the main body;
An ON-OFF valve disposed in a second oil passage through which the hydraulic oil that has passed through the throttle passage flows,
The pressurizing force of the hydraulic oil in the first oil passage acts in the direction of opening the valve body, and the pressurizing force of the hydraulic oil in the second oil passage acts in the direction of closing the valve body,
A lifting device characterized in that a return path connected to the outflow side of the ON-OFF valve is connected to the hydraulic pump.   By rotating the hydraulic pump in the upward operation direction when the pilot check valve is closed, the pilot check valve in the hydraulic cylinder side of the pilot check valve in the first oil passage and the pilot check valve in the first oil passage The lifting device according to claim 1, wherein a pressure difference on the hydraulic pump side is reduced.   The elevating device according to claim 2, wherein the ON-OFF valve is opened after the hydraulic pump is rotated in the ascending operation direction with the ON-OFF valve closed.   A check valve is provided on an oil passage between the pilot check valve and the ON-OFF valve so as to allow a flow of hydraulic oil from the pilot check valve to the ON-OFF valve. The lifting device according to claim 1 or 2. The first oil passage includes an ascending oil passage for flowing hydraulic oil to the second oil passage through the restricting passage when the hydraulic cylinder is raised, and the restrictor when the hydraulic cylinder is lowered. A descent oil path for circulating hydraulic oil through the flow path to the second oil path,
The elevating device according to any one of claims 1 to 3, wherein the ON-OFF valve is opened when the hydraulic cylinder is raised.