JP3401666B2 - Control device for loading cylinder of forklift truck - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling a cargo handling cylinder in a forklift truck. 2. Description of the Related Art Conventionally, a reach forklift truck, which is a kind of forklift truck, is provided with a vehicle body 2 having a driving section 1 formed at a rear portion thereof, and a front lower portion of the vehicle body 2 is provided at a front lower portion thereof as shown in FIG. A pair of left and right reach legs 3 lie sideways is provided, and a pair of left and right masts 4 are erected along the reach legs 3 so that the mast 4 slides along the reach legs 3. This is done by the reach cylinder 5 lying down. And
The mast 4 was provided with a lift bracket 6 and a fork claw 7 that moved up and down. In this reach forklift truck, as a control device for controlling the reach cylinder 5, as shown in FIG. 2, a hydraulic pump 11 for supplying hydraulic oil to the reach cylinder 5, and a drive of the hydraulic pump 11 And a hydraulic pump 1
1 is provided with a proportional solenoid valve 13 for supplying the working oil supplied from 1 to a desired side of the reach cylinder 5 and a desired flow rate. The proportional solenoid valve 13 has three positions: a forward position F, a neutral position N, and a reverse position R. It has two moving positions and is connected to the front side of the reach cylinder 5 by the first flow path 14, and is connected to the rear side of the reach cylinder 5 by the second flow path 15. The hydraulic cylinder 15 is supplied with hydraulic oil to make the reach cylinder 5 move forward, and in the reverse position R, hydraulic oil is supplied to the first flow path 14 to move the reach cylinder 5 backward. And this proportional solenoid valve 13
Is connected to a controller 16 mounted inside the vehicle body 2, and the controller 16
Is controlled in accordance with the operation side and the operation amount. [0004] In such a conventional control device for controlling a reach cylinder, the reach cylinder is moved forward or backward to operate until the stroke end, and then the reverse operation (reverse operation or reverse operation) is performed. When the forward movement is performed, a steep pressure acts due to the accumulated pressure in the first flow path or the second flow path, and an impact occurs on the operation of the reach cylinder. This is, for example, when moving the reach cylinder forward
Hydraulic oil is supplied to the second flow path by the proportional solenoid valve. When the hydraulic oil is operated up to the stroke end, the hydraulic oil is supplied even after the advance operation of the reach cylinder is stopped, and the second flow path has a high pressure. Then, when the proportional solenoid valve moves to the neutral position, the storage pressure of the second flow path remains at a high pressure, and when the reverse operation is performed in this state, the high-pressure hydraulic oil in the second flow path is discharged. Hydraulic oil is supplied to the first flow path without being discharged,
When the hydraulic fluid in the second flow path has been discharged to some extent, that is, when the pressure in the first flow path is high, the reach cylinder starts a reverse operation. Then, an abrupt pressure due to the high pressure in the first flow path causes an impact on the backward movement of the reach cylinder. For this reason, there is a possibility that the luggage placed on the fork claws may collapse. An object of the present invention is to solve this problem. [0005] In order to solve the above-mentioned problems, the present invention comprises a hydraulic pump for supplying hydraulic oil to a cargo handling cylinder, and a hydraulic pump driving means for driving the hydraulic pump. A controller which includes a proportional solenoid valve for supplying a desired flow rate of the working oil supplied from the hydraulic pump to a desired side of the cargo handling cylinder, and controls the proportional solenoid valve in accordance with the operation side of the operation means and the operation amount In the control device for a loading cylinder of a forklift truck provided with: when the proportional solenoid valve is in the neutral position after the loading cylinder is operated by the controller, the proportional solenoid valve is opposite to the side on which the proportional solenoid valve has been operated. This is a control device for a loading cylinder of a forklift truck controlled to operate for a short time on the side. According to the present invention, after the cargo handling cylinder is operated, the hydraulic oil accumulated in the flow path between the cargo handling cylinder and the proportional solenoid valve can be discharged, and the accumulated pressure there is reduced. By preventing the high pressure, the cargo handling cylinder operates to the stroke end, and when the opposite operation is performed from this point, it is possible to prevent sudden pressure from acting because the storage pressure in the flow path does not become high. Therefore, it is possible to prevent the operation of the cargo handling cylinder from being impacted. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a control device for a loading cylinder of a forklift truck according to the present invention will be described. This example is for a reach cylinder, which is a type of cargo handling cylinder in a reach forklift truck. In the reach forklift truck, as a control device for controlling the reach cylinder 5, as shown in FIG. 3, a hydraulic pump 11 for supplying hydraulic oil to the reach cylinder 5, and a hydraulic pump driving means for driving the hydraulic pump 11 And a proportional solenoid valve 13 for supplying hydraulic oil supplied from the hydraulic pump 11 to a desired side of the reach cylinder 5 and a desired flow rate. The proportional solenoid valve 13 is movable. And a solenoid A and a solenoid B for moving the spool to the left and right, and a forward position F,
It has three moving positions, a neutral position N and a reverse position R, and gradually moves between these three moving positions. In the proportional solenoid valve 13,
It is connected to the front side of the reach cylinder 5 by the first flow path 14 and is connected to the rear side of the reach cylinder 5 by the second flow path 15. The hydraulic fluid is supplied to the flow path 15, and the hydraulic oil is supplied to the rear side of the reach cylinder 5 to cause the reach cylinder 5 to move forward and discharge the hydraulic oil accumulated in the first flow path 14 to the tank 18. . Further, at the reverse position R, the hydraulic oil from the hydraulic pump 11 is supplied to the first flow path 14 and the hydraulic oil is supplied to the front side of the reach cylinder 5 so that the reach cylinder 5 is moved backward and the second flow Road 15
The working oil accumulated in the tank is discharged to the tank 18. In the neutral position N, the hydraulic oil from the hydraulic pump 11 is discharged to the tank 18. The proportional solenoid valve 13 is connected to a controller 16 mounted inside the vehicle body 2. The controller 16 normally detects the operation side and the operation amount of an operation lever 17 as operation means. Then, based on this, an operation signal is sent to each of the solenoids A and B of the proportional solenoid valve 13 to move the spool to the forward position F, the reverse position R or the neutral position N, and the reach cylinder 5 is operated. As described above, the flow rate of the proportional solenoid valve 13 is controlled by the controller 16 in accordance with the operation side and the operation amount of the operation lever 17. The controller 16 is also connected to the motor 12, and controls the motor 12. In such a control device, when the proportional solenoid valve 13 reaches the neutral position N after the reach cylinder 5 is operated, the controller 16 determines whether the proportional solenoid valve 13 has been operated. It is controlled to operate on the opposite side for a short time. When the reach cylinder 5 is moved forward, as shown in FIG. 4, the controller 16 inputs the operation side (forward side) and the operation amount from the operation lever 17 and proportionally outputs an operation signal based on the input. The output is output to the solenoid A of the solenoid valve 13, the spool is moved to the forward position F by the proportional solenoid valve 13, hydraulic oil is supplied to the rear side of the reach cylinder 5, and the reach cylinder 5 is moved forward. When the operator returns the operation lever 17 to neutral after the reach cylinder 5 has moved forward to the front stroke end and stopped, for example, the controller 16 transmits an operation signal to the solenoid A of the proportional solenoid valve 13. The output is eliminated, the spool of the proportional solenoid valve 13 is moved to the neutral position N, and the supply of the hydraulic oil to the rear side of the reach cylinder 5 is stopped. Then, for a short time after a lapse of a predetermined time, a small operation signal is output to the solenoid B of the proportional solenoid valve 13 which is on the opposite side to the side that has been operated so far, and the spool of the proportional solenoid valve 13 is moved. Then, the output of the operation signal to the solenoid B of the proportional solenoid valve 13 is immediately stopped, and the spool of the proportional solenoid valve 13 is moved to the neutral position N. In the reverse position R of the proportional solenoid valve 13, the operation is performed in response to a small operation signal for a short time, so that the reach cylinder 5 does not actually perform the reverse operation. Next, when the reach cylinder 5 is moved backward, the controller 13 also inputs the operation side (reverse side) and the operation amount from the operation lever 17 and outputs an operation signal based on the operation signal to the solenoid B of the proportional solenoid valve 13. And the spool is moved in the proportional solenoid valve 13 to the reverse position R,
Hydraulic oil is supplied to the front side of the reach cylinder 5 to move the reach cylinder 5 backward. For example, when the operator returns the operation lever 17 to neutral after the reach cylinder 5 has moved backward to the rear stroke end and stopped, the controller 16 issues an operation signal to the solenoid B of the proportional solenoid valve 13. , The spool of the proportional solenoid valve 13 is moved to the neutral position N, and the supply of hydraulic oil to the front side of the reach cylinder 5 is stopped. Then, for a short time after the elapse of a predetermined time, a small operation signal is output to the solenoid A of the proportional solenoid valve 13 on the opposite side to the side that has been operated so far, and the spool of the proportional solenoid valve 13 is moved. Then, the output of the operation signal to the solenoid A of the proportional solenoid valve 13 is immediately stopped, and the spool of the proportional solenoid valve 13 is moved to the neutral position N. In addition, even in the forward position F of the proportional solenoid valve 13, since it operates by receiving a small operation signal for a short time, the reach cylinder 5 does not actually move forward. As described above, in the controller 16, when the proportional solenoid valve 13 is in the neutral position N after the reach cylinder 5 is operated, a slight amount is provided on the side opposite to the side where the proportional solenoid valve 13 has been operated. By operating for a time, for example, the first flow path 1 interposed between the reach cylinder 5 and the proportional solenoid valve 13 when operating to the stroke end
Hydraulic oil accumulated in the fourth or second flow path 15 can be discharged, and the accumulated hydraulic oil in the first flow path 14 or the second flow path 15 is prevented from becoming high pressure by discharging the accumulated hydraulic oil. can do. As a result, when the reach cylinder 5 is operated to the stroke end, and when the reverse operation is performed from this point, the pressure in the first flow path 14 or the second flow path 15 does not become high, so that a sudden pressure acts. To eliminate the problem that an impact occurs in the operation of the reach cylinder 5. In the above-described embodiment, the case of the reach cylinder 5 which is a kind of the cargo handling cylinder in the reach forklift truck has been described.
The present invention is not limited to this, and may be used for a tilt cylinder in a forklift truck or another attachment cylinder. In the above-described embodiment, when the proportional solenoid valve 13 reaches the neutral position N after the reach cylinder 5 operates, the proportional solenoid valve 13 is moved to the side opposite to the side on which the proportional solenoid valve 13 has been operated. The controller 16 is set to operate for a short time.
However, the controller 16 is provided with a detecting means such as a sensor for detecting that the reach cylinder 5 has operated to the end of the stroke, and the controller 16 uses the data from the detecting means only when the reach cylinder 5 operates to the end of the stroke. Alternatively, the proportional solenoid valve 13 may be controlled to operate for a short period of time on the side opposite to the side on which it has been operating. After the cargo handling cylinder has been operated, the hydraulic oil accumulated in the flow path between the cargo handling cylinder and the proportional solenoid valve can be discharged, and the storage pressure of the working oil becomes high. By operating the cargo handling cylinder up to the stroke end and performing the opposite operation from here, the stow pressure in the flow path does not become high, eliminating the sudden pressure,
Eliminates impacts on the operation of the cargo handling cylinder. As a result, it is possible to eliminate the occurrence of collapse of the luggage or the like placed on the fork claws.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side view of a reach forklift truck. FIG. 2 is a configuration diagram of a conventional control device for a cargo handling cylinder. FIG. 3 is a configuration diagram of a control device for a cargo handling cylinder according to the present invention. FIG. 4 is an explanatory diagram showing control in a controller. [Explanation of Signs] 1 ... operating unit, 2 ... body, 3 ... reach leg, 4 ... mast, 5 ... reach cylinder, 6 ... lift bracket, 7 ...
Fork claws 7, 11: hydraulic pump, 12: motor, 13
... Proportional solenoid valve, 14 ... First flow path, 15 ... Second flow path, 16
... Controller, 17 ... Operation lever, 18 ... Tank.

Claims (1)

(57) Claims 1. A hydraulic pump 11 for supplying hydraulic oil to a cargo handling cylinder, a hydraulic pump driving means for driving the hydraulic pump 11, and a supply from the hydraulic pump 11 And a controller 16 for controlling the proportional solenoid valve 13 in accordance with the operation side and the operation amount of the operation means. In the control device for a loading cylinder of a forklift truck, when the proportional solenoid valve 13 is in the neutral position after the loading cylinder is operated by the controller 16, the proportional solenoid valve 13 is opposite to the side that has been operated. A control device for a loading cylinder of a forklift truck, wherein the control device is operated so as to be operated for a short time to the side.