JP2000355497A - Cylinder control device for cargo handling of forklift truck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make proper the operability of an operation lever in work even at any state regardless of a load or noload. SOLUTION: The control device for the lift cylinder 3 of a forklift truck provided with a controller 9 for outputting an order signal and controlling the operation of a comparative solenoid valve 8 is provided with a pressure sensor 11 for detecting a load. In the controller 9, the initial value of an order signal outputting to the comparative solenoid valve 8 is enlarged as the load is bigger based on the load detected by this pressure sensor 11 and the lever operation range of the operation lever 10 is enlarged by minifying the change amount of this order signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling a cargo handling cylinder such as a lift cylinder for raising and lowering a fork, a tilt cylinder for tilting a mast, and other attachment cylinders in a forklift truck.

[0002]

2. Description of the Related Art As a conventional control device for a cargo handling cylinder of a forklift truck, first, as shown in FIG.
The control device of the lift cylinder 3, which is a cargo handling cylinder that moves the lift cylinder 3 up and down through the chain 2, includes a hydraulic pump 6 that discharges hydraulic oil from a hydraulic tank 5 as a hydraulic circuit 4 that drives the lift cylinder 3, A pump motor 7 for driving the pump 6 is provided, and a proportional solenoid valve 8 as an operation valve for regulating a flow rate of hydraulic oil discharged from the hydraulic pump 6 and supplying a desired flow rate to the lift cylinder 3 is provided.

The proportional solenoid valve 8 moves the spool by the solenoid A and the solenoid B based on the input command signal, and moves at the ascending position U, the stop position N, and the descending position D, and the hydraulic oil flows. The lift, stop, and descent of the lift cylinder 3 are performed by changing the flow rate of the hydraulic oil by changing the direction and the valve opening.

[0004] The solenoids A and B are connected to a controller 9 and are controlled by receiving a command signal from the controller 9. The controller 9 is connected to an operation lever 10 installed in the cab of the vehicle body, inputs an operation direction and an operation amount of the operation lever 10, thereby driving the pump motor 7, and based on the operation amount. A command signal is output to the solenoid A or the solenoid B to control the operation of the proportional solenoid valve 8.

[0005] In such a controller 9,
The command signal output to control the operation of the proportional solenoid valve 8 is a valve opening calculated by a calculation map indicating a valve opening of the proportional solenoid valve 8 with respect to a preset lever operation amount shown in FIG. This calculation map sets the lever operation amount from 0% to 100%, for example, once at 10%, rises up to a predetermined value as an initial value,
From this, the valve opening is linearly increased to the lever operation amount of 80%, and the valve opening is set to 100% which is the full opening of the valve opening at the lever operation amount of 80%.

[0006]

In a conventional control apparatus for a loading cylinder of a forklift truck, a calculation map indicating a valve opening of a proportional solenoid valve with respect to a lever operation amount preset in a controller is determined uniformly. Therefore, the weight is determined based on the no-load condition where the load placed on the fork is zero. For this reason, for example, as for the operating speed of the lift cylinder when the fork is raised, if the command signal is the same both when the load is placed on the fork and when the load is not loaded, as shown in FIG. When the load is applied, the operating speed is in accordance with the lever operation amount as indicated by the line A. However, when the load is placed on a fork, the load does not increase the lever operation amount with respect to the lever operation as indicated by the line B due to the load. This is because the actual operation of the lift cylinder is delayed by the load even if the predetermined command signal is output. In addition, due to the delay in the operation, the lever operation (stroke) range in which the operator can control the lift speed becomes extremely small as compared with the case where no load is applied. From 80% to 80% under load, and the lever operation range becomes extremely small. Therefore, there has been a problem that it is extremely difficult for the operator to adjust the operating speed by operating the operation lever. An object of the present invention is to solve this problem.

[0007]

SUMMARY OF THE INVENTION The present invention provides a hydraulic pump for discharging working oil, a proportional solenoid valve for regulating the flow rate of hydraulic oil discharged from the hydraulic pump and supplying a desired flow rate to a cargo handling cylinder. A load detection cylinder for a forklift truck, comprising: a controller that outputs a command signal based on the operation of an operation lever to the proportional solenoid valve and controls the operation of the proportional solenoid valve. Means for increasing the initial value of the command signal output to the proportional solenoid valve as the load increases based on the load detected by the load detecting means, and reducing the amount of change in the command signal. Thus, the present invention provides a control apparatus for a loading cylinder of a lift truck, in which a lever operation range of the operation lever is increased.

[0008]

According to the present invention, it is possible to eliminate the possibility that the lever does not move unless the lever operation amount becomes large with respect to the lever operation at the time of load operation, and to control the lift speed by the operator. The range can be prevented from becoming smaller than when there is no load, and the operation speed can be easily adjusted by operating the operation lever, so that work can be performed regardless of load or no load. To improve the operability of the operation lever.

[0009]

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. In a forklift truck, as shown in FIG. 4, for example, a control device for a lift cylinder 3 which is a loading / unloading cylinder for moving the fork 1 up and down via a chain 2 includes a hydraulic circuit 4 for driving the lift cylinder 3.
A hydraulic pump 6 for discharging hydraulic oil from a hydraulic tank 5
And a proportional solenoid valve 8 that regulates the flow rate of hydraulic oil discharged from the hydraulic pump 6 and supplies a desired flow rate to the lift cylinder 3.

The proportional solenoid valve 8 moves a spool by a solenoid A and a solenoid B based on an input command signal, so that the hydraulic oil is supplied to the bottom side of the lift cylinder 3 at a raised position U, at which a hydraulic oil is supplied. It moves at a stop position N at which the flow is interrupted and at a descending position D at which the hydraulic oil flows from the bottom side of the lift cylinder 3 to the hydraulic tank 5, and the flow direction of the hydraulic oil and the flow rate of the hydraulic oil are changed. Then, the lift cylinder 3 is moved up, stopped, and lowered.

The solenoids A and B are connected to a controller 9 and are controlled by receiving a command signal from the controller 9. The controller 9 is connected to an operation lever 10 installed in the cab of the vehicle body, inputs an operation direction and an operation amount of the operation lever 10, thereby driving the pump motor 7, and based on the operation amount. Solenoid A or solenoid B
To control the operation of the proportional solenoid valve 8.

A pressure sensor 11 is provided as load detecting means for detecting the pressure of the lift cylinder 3, that is, the load in the hydraulic circuit 4. The pressure sensor 11 detects the load on the lift cylinder 3, so that it is mounted on a fork. The load of the loaded cargo, which is the weight of the loaded luggage, is detected. The pressure sensor 11 is also connected to the controller 9 and inputs the load of the lift cylinder 3 detected by the pressure sensor 11 to the controller 9.

The controller 9 outputs a command signal for controlling the operation of the proportional solenoid valve 8 in a calculation map indicating the valve opening of the proportional solenoid valve 8 with respect to a preset lever operation amount shown in FIG. Calculated by
Based on the load on the lift cylinder 3 detected by the pressure sensor 11, the valve opening is such that the larger the load, the larger the initial value of the command signal and the smaller the amount of change of the command signal.

The calculation of the command signal will be specifically described. First, a command signal corresponding to the lever operation amount is calculated from a calculation map indicating the valve opening of the proportional solenoid valve 8 with respect to the lever operation amount. As shown in FIG. 5, the calculation map indicating the valve opening degree of the proportional solenoid valve 8 with respect to the lever operation amount is based on a no-load condition where the weight of the load placed on the fork is 0. At a lever operation amount of 10%, it once rises greatly and becomes a predetermined value as an initial value. The predetermined value is a substantially maximum value in a range where the lift cylinder 3 does not actually operate when there is no load, which is obtained in advance through experiments or the like. Specifically, the variation (value) of the operation of the proportional solenoid valve 8 is obtained by subtracting the variation (value) of the operation of the proportional solenoid valve 8 from the value at which the lift cylinder 3 actually operates, and the obtained value is used as an initial value. The valve opening is linearly increased so that the valve opening is fully opened at 100% when the lever operation amount is 80%. Thus, when there is no luggage in the fork, that is, when there is no load, the command signal corresponding to the lever operation amount is calculated as described above.

On the other hand, when a load is placed on a fork with a load, the command signal calculated as described above is changed according to the load detected by the pressure sensor 11 for calculation.
First, for example, as shown in FIG. 6, in the initial value of the command signal, a calculation map indicating the initial increase amount with respect to the load is used, and this calculation map is obtained in advance by an experiment or the like. Specifically, as shown in FIG. 6, an initial value is obtained for each of several types of loads in the same manner as for no-load, and the amount of increase between these initial values is obtained by interpolation. Note that, although the calculation map is a polygonal line, it may be a linear one. Further, the calculation may be performed by using an expression without using such an operation map. For example, if the load is linear, the maximum initial increase amount imax is obtained in advance, and the load (pressure) is calculated.
The value obtained by subtracting the no-load (pressure) P0 from P is divided by the value obtained by subtracting the no-load (pressure) P0 from the rated load (pressure) Pmax, and this value is a maximum initial increase imax obtained in advance.
To calculate the initial increase with respect to the load. When this is expressed as an equation, the initial increase amount = imax × (P
−P0) ÷ (Pma−P0). The initial increase with respect to the load can be obtained by such various methods. Then, an initial increase amount with respect to the load is calculated using an arithmetic map or an expression indicating the initial increase amount with respect to the load, and the arithmetic map indicating the valve opening degree of the proportional solenoid valve 8 with respect to the lever operation amount is calculated using the initial increase amount. The initial value of the command signal changed according to the load is calculated by adding to the initial value of the command signal calculated on the basis of the initial value, and the initial value of the command signal increases as the load increases.

In the command signal when the lever operation amount is increased, the command signal calculated by using the above-mentioned operation map showing the valve opening of the proportional solenoid valve 8 with respect to the lever operation amount is calculated by the increase amount according to the load. The command signal is calculated by adding and changing. To calculate the command signal changed according to the load, first, a coefficient corresponding to the lever operation amount is calculated, and as shown in FIG. 7, the coefficient is calculated from a calculation map indicating the coefficient for the lever operation amount. In the operation map, when the lever operation amount is small, for example, 10% or less, its value is set to 1, and the value gradually decreases as the lever operation amount increases, and becomes 0 at 80%. The amount of increase is calculated by multiplying the coefficient corresponding to the lever operation amount by the initial increase amount calculated at the initial value of the command signal, and the increase amount is calculated by opening the proportional solenoid valve 8 with respect to the lever operation amount. A command signal changed according to the load is calculated by adding to the command signal calculated using the calculation map indicating the degree, and the change amount of the command signal decreases as the load increases.

As a result, as shown in FIG. 5, the command signal finally output to the proportional solenoid valve 8 becomes a line as shown by a solid line in FIG. For example, the maximum load) is a line shown by a dashed line in FIG. 5, and changes between the line at the time of no load and the line at the time of the rated load according to the load.

As described above, in the controller 9, the command signal based on the operation of the operation lever 10 output to the proportional solenoid valve 8 is calculated by changing it according to the load input from the pressure sensor 11, and this is calculated. 8, the operation signal of the lift cylinder 3 when the fork 1 rises has different command signals at no load and at each load. As shown in FIG. As shown, the operating speed is in accordance with the lever operation amount. In addition, when a load is placed on the fork 1, for example, between a rated load indicated by a dashed line in FIG. 8 and a no-load indicated by a solid line, the load changes according to the load. Not only does not move unless the lever operation amount becomes large, and the lever operation (stroke) range in which the operator can control the lift speed can be increased as well as when there is no load.
For example, the lever operation range is 10% to 80% when no load is applied, and 10% to 80% when load is applied. Thus, the lever operation range can be increased both when no load is applied and when load is applied.

This prevents the operating range of the operating lever 10 from being reduced during loading and unloading work, particularly during load operation, and allows the operating speed of the operating lever 10 to be adjusted by operating the operating lever 10. Can be made easier,
The operability of the operation lever 10 in the cargo handling operation can be improved.

In the arithmetic map showing the valve opening degree of the proportional solenoid valve 8 with respect to the lever operation amount as a command signal output for controlling the operation of the proportional solenoid valve 8 in the controller 9, However, the present invention is not limited to this. For example, as shown in FIG. 9, the increase from the initial value may be a curve-like increase instead of the aforementioned linear increase.

Next, a description will be given of another embodiment of the control device for a loading cylinder of a forklift truck according to the present invention.
The calculation of the command signal output to control the operation of the proportional solenoid valve 8 in the controller 9 is different from that of the above-described embodiment. Therefore, the calculation of the command signal will be specifically described.
A command signal corresponding to the lever operation amount is calculated from the operation map indicating the valve opening degree of the valve. The operation map indicating the valve opening degree of the proportional solenoid valve 8 with respect to the lever operation amount is, as shown in FIG. No-load operation line A based on time
The operation line B for small load, the initial value of which is slightly larger and the change amount is slightly smaller than the operation line A for no load, and the initial value is larger and the change amount thereof is smaller for the operation line A for no load. And a large load operation line C to distinguish between no load, small load, and large load.

The no-load operation line A, for example, once rises sharply at a lever operation amount of 10% to become a predetermined value as an initial value. The valve opening is linearly increased from this initial value to a lever operation amount of 80% by setting it to a substantially maximum value in a range where the lift cylinder 3 does not actually operate.
Full opening of valve opening at 80% lever operation 1
00%. Also, the operation line B for small load
Is a substantially maximum value in a range in which the lift cylinder 3 does not actually operate at a small load, that is, an initial value that is slightly larger than the no-load operation line A when a lever operation amount is 10% and is obtained in advance through experiments or the like. The valve opening is linearly increased from this initial value to a lever operation amount of 80%, and the valve opening is fully opened at a lever operation amount of 80%.
%, And the slope of the linearly increasing portion is slightly smaller than the no-load operation line A, that is, the amount of change is slightly smaller. Furthermore, the heavy load operation line C
Is a substantially maximum value in a range where the lift cylinder 3 does not actually operate under a large load, that is, an initial value that is a large value with respect to the no-load operation line A, which is obtained in advance by experiment or the like at a lever operation amount of 10%. The valve opening is linearly increased from this initial value to a lever operation amount of 80%, so that the valve opening becomes 100%, which is a full opening of the valve opening at a lever operation amount of 80%, and the linearly increasing portion. Is significantly smaller than the no-load operation line A, that is, the amount of change is reduced.

According to the load detected by the pressure sensor 11, the operation map A for no load, the operation line B for small load, the operation line B for large load, A desired operation line is selected from the operation lines C, and a command signal corresponding to the lever operation amount is calculated using the selected operation line.

As a result, the command signal finally output to the proportional solenoid valve 8 is changed according to the load. As in the above-described embodiment, during the loading operation, particularly during the load operation. In addition, it is possible to prevent the lever operation range of the operation lever 10 from being reduced, to easily adjust the operation speed by operating the operation lever 10, and to improve the operability of the operation lever 10 in the cargo handling operation. be able to.

The proportional solenoid valve 8 for the lever operation amount
Is not limited to the three patterns of the no-load operation line A, the small-load operation line B, and the large-load operation line C, but may be further divided into a plurality of patterns. Is also good.

Further, in each of the above-described embodiments, an example in which a lift cylinder is used as a cargo handling cylinder has been described. However, the present invention is not limited to this. Attachment cylinders and the like may be used.

[0027]

As described above, according to the present invention, it is possible to eliminate the need for the lever operation amount to become large with respect to the lever operation during work under load, and to prevent the operator from controlling the lift speed. The range can be prevented from becoming smaller than when there is no load, and the operation speed can be easily adjusted by operating the operation lever, so that work can be performed regardless of load or no load. , The operability of the operation lever can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a conventional control device for a loading cylinder of a forklift truck.

FIG. 2 is a table for explaining a conventional calculation map showing a valve opening degree of a proportional solenoid valve with respect to a lever operation amount.

FIG. 3 is a table for explaining an operation speed according to a conventional lever operation amount.

FIG. 4 is a configuration diagram of a control device for a loading cylinder of a forklift truck according to the present invention.

FIG. 5 is a table for explaining a calculation map showing a valve opening degree of a proportional solenoid valve with respect to a lever operation amount according to the present invention.

FIG. 6 is a table for explaining a calculation map showing an initial increase amount with respect to a load according to the present invention.

FIG. 7 is a table illustrating a calculation map indicating a coefficient with respect to a lever operation amount according to the present invention.

FIG. 8 is a table illustrating an operating speed according to a lever operation amount according to the present invention.

FIG. 9 is a table for explaining a calculation map showing a valve opening degree of a proportional solenoid valve with respect to another lever operation amount according to the present invention.

FIG. 10 is a table for explaining a calculation map showing a valve opening degree of a proportional solenoid valve with respect to another lever operation amount according to the present invention.

[Explanation of symbols]

1 ... fork, 2 ... chain, 3 ... lift cylinder, 4
... Hydraulic circuit, 5 ... Hydraulic tank, 6 ... Hydraulic pump, 7 ... Pump motor, 8 ... Proportional solenoid valve, 9 ... Controller, 10
... operation lever, 11 ... pressure sensor.

Claims (1)

[Claims] 1. A hydraulic pump 6 for discharging working oil, and a proportional solenoid valve 8 for regulating a flow rate of hydraulic oil discharged from the hydraulic pump 6 and supplying a desired flow rate to a cargo handling cylinder. In a control device for a loading cylinder of a forklift truck provided with a controller 9 for controlling the operation of the proportional solenoid valve 8 by outputting a command signal based on the operation of the operation lever 10 to the solenoid valve 8, a load detecting means for detecting a load And the controller 9 increases the initial value of the command signal output to the proportional solenoid valve 8 and reduces the amount of change of the command signal as the load increases based on the load detected by the load detecting means. The control of the cargo handling cylinder of the forklift truck, characterized in that the lever operation range of the operation lever 10 is increased. Location.