JPH04358699A - Lowering speed controller - Google Patents

Abstract

PURPOSE:To prevent a shock due to a sudden lowering during the lowering of an elevation lift cylinder of a fork lift. CONSTITUTION:The base end and the end of a hydraulic pipe line 16 are respectively provided with hydraulic sensors 17a, 17b. The difference of hydraulic pressure by the hydraulic sensors 17a, 17b is obtained so that flow rate Q is calculated and an electromagnetic proportional control valve is driven.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlling the descending speed of a lift cinder for lifting loads with a forklift or the like using electro-hydraulic control.

0002

BACKGROUND OF THE INVENTION Working machines, such as forklifts for handling and transporting cargo, need to ensure safety in their operations because they are used to load, unload, and transport cargo. In other words, when tilting or raising/lowering the fork using a hydraulic cylinder, it is necessary to securely place, load and unload the load, and to ensure that the load does not collapse or fall during transportation. Careful driving is required.

On the other hand, when focusing on mechanical forklifts, for example, when controlling a hydraulic cylinder in the lifting direction (referred to as a lift cylinder), the operation amount of the operating lever is controlled via a mechanical link mechanism. The amount of oil in the lift cylinder is controlled by controlling the opening degree of this control valve, which in turn adjusts the speed during lifting and lowering.

In this case, it is necessary to operate the lift cylinder to prevent the cargo from collapsing or falling as described above, and although a flow regulator is provided to keep the descending speed constant, with this conventional configuration, the cargo suddenly descends when it starts descending. There is a problem in that a shock occurs when a phenomenon occurs and normal function returns, resulting in a lack of safety.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a descending speed control device for an electro-hydraulic controlled working machine in order to obtain a highly safe working machine that prevents sudden descent at the start of descent.

[0006]

[Means for Solving the Problems] The present invention achieves the above-mentioned objects in a work machine in which a controller controls a hydraulic device that executes a function in response to an operation input of a work machine lever. The controller is connected to respective hydraulic pipes on the electromagnetic proportional control valve side and the lift cylinder side between the electromagnetic proportional control valve controlled by the electromagnetic proportional control valve and the lift cylinder driven by the electromagnetic proportional control valve. Equipped with an oil pressure sensor, it calculates the differential pressure between these two oil pressure sensors and calculates the flow rate corresponding to the load.
The present invention is characterized by comprising the controller that controls the opening and closing of the electromagnetic proportional control valve by comparing the flow rate with a set value.

[0007]

[Function] In electro-hydraulic controlled working machines, hydraulic pressure sensors are installed on the base end and distal end of the hydraulic piping in the hydraulic equipment, and the true flow rate is obtained by obtaining the difference in hydraulic pressure. Moreover, since the difference is calculated to compensate for various variations, it is possible to prevent a shock caused by a sudden drop, etc. at the start of descent.

[0008]

EXAMPLES The present invention will be explained in detail below based on examples.

FIG. 5 is a perspective view showing an example of a forklift to which this embodiment is applied. As shown in the figure, the lift cylinder 1 is fixed to a pair of left and right outer masts 2, and as the piston rod 1a expands and contracts, the outer masts 2
The pair of left and right inner masts 3 are raised and lowered using the inner masts 3 as a guide. At this time, the outer mast 2 is fixed to the vehicle body 7 at the front of the vehicle body 7. As a result, as the inner mast 3 moves up and down, an elevating section consisting of a bracket 5 suspended from a chain (not shown) and a fork 4 on which cargo is directly mounted moves up and down.

The tilt cylinder 8 is used to tilt the elevating section together with the outer mast 2 and the inner mast 3 forward (toward the vehicle body 7 side) and rearward (toward the vehicle body 7 side). That is, it tilts forward when unloading, and tilts backward when loading and transporting cargo, thereby maintaining good workability and ensuring safety.

The work equipment levers 9a and 9b are operated by an operator to control the operation of the lift cylinder 1 and the tilt cylinder 8 via the controller 10 and the electromagnetic proportional control valve 11, and are used to perform an emergency stop. It is housed in a joystick box 13 along with a safety switch 12 for use. Work machine levers 9c, 9d, 9
e is provided as a preliminary measure in case various attachments are attached. The seat switch 14 is a switch that operates when an operator sits on the driver's seat 15, and its output signal is sent to the controller 10.

FIG. 6 is a block diagram showing an example of a control device for the forklift. In the figure, parts that are the same as those in FIG. 5 are given the same numbers and redundant explanations will be omitted.

As shown in FIG. 6, the work machine levers 9a, 9
b. It is formed by a potentiometer and sends to the controller 10 a lever operation signal S1 whose current value is proportional to the amount of operation. The controller 10 receives a lever operation signal S1
Based on this, a flow rate control signal S2 is sent out to adjust the opening degree of the spool of the electromagnetic proportional control valve 11. The electromagnetic proportional control valve 11 controls the flow rate of hydraulic pressure flowing through the hydraulic line 16 by moving its spool in proportion to the magnitude of the flow rate control signal S2, thereby controlling the operating speed of the lift cylinder 1 and tilt cylinder 8. Control is performed to correspond to the amount of operation of the machine levers 9a and 9b.

The oil pressure sensors 17a and 17b are connected to the oil pressure pipe 16.
are arranged at the base end and tip of the hydraulic pipe line 1.
The load acting on the lift cylinder 1 or the tilt cylinder 8 is calculated by processing the hydraulic signals S3a and S3b representing the pressure of the pressure oil 6.

Furthermore, the controller 10 has a warning light 18.
When the starter switch 20 housed in the console box 19 is turned on, power is supplied from the battery 21 to operate, and when the safety switch 12 is operated and the seat switch 14 is not operated, the current value of the flow rate control signal S2 is changed. is set to zero, and the opening degree of the current proportional control valve 11 is controlled to be zero. That is, the vertical positions and postures of the lift cylinder 1 and the tilt cylinder 8 are maintained as they are.

In the figure, 22 is a hydraulic pump, and 23 is a hydraulic oil source. In addition, an electromagnetic proportional control valve 11, a hydraulic pipe line 16
, hydraulic system parts such as the oil pressure sensor 17 are connected to the work machine lever 9a.
The number corresponding to the number of ~9e is provided. Since this embodiment has two working machine levers 9a and 9b for lifting and tilting, two hydraulic systems are provided.

FIG. 1 shows the processing operation of the controller 10. That is, when the work implement lever 9a is operated with the seat switch 14 in FIGS. 5 and 6 on and the safety switch 12 off, the operation signal S1 is input to the control amount extraction means 100, and this control Amount extraction means 1
00, the control amount corresponding to the operation signal S1 is extracted from the operation amount/control amount correspondence table stored in the RAM 105 (ROM). In this case, the correspondence table has the characteristics shown in FIG. 2 with respect to the opening degree of the work equipment lever 9a, including a so-called dead zone part, an inching characteristic part where the control amount changes less than changes in the lever opening degree, and a lever It has a portion where the opening degree and the controlled amount are proportional.

On the other hand, the oil pressure signals S of the oil pressure sensor 17b provided in the hydraulic line on the lift cylinder 1 side and the oil pressure sensor 17a provided on the oil pressure line on the electromagnetic proportional control valve 11 side are
The flow rate calculating means 10 of the controller 10 to which the signals S3b and S3a are input calculates the flow rate based on the differential pressure between the hydraulic signals S3b and S3a. That is, the oil pressure P1 based on the oil pressure signal S3b
The differential pressure (P1
-P2) In other words, the flow rate is detected by piping resistance. and,
In this case, the flow rate Q is obtained by the following equation.

[0019]

[Math 1]

Here, Q is the lift descending flow rate, C is the flow rate coefficient, A is the opening area, g is the gravitational acceleration, and r is the unit volume weight. The above equation shows the relationship between the pressure difference (P1 - P2) and the lift downward flow rate, which is illustrated in the relationship shown in FIG. The flow rate due to this differential pressure (P1 - P2) is not controlled directly using the pressure of the lift cylinder 1, so it may be affected by variations in the hydraulic circuit, variations in the characteristics of the electromagnetic proportional control valve coil, or the controller's current. It is not easily affected by characteristics, etc., and can also eliminate sudden sudden drops.

The flow rate obtained by the flow rate calculation means 101 is
Comparison means 102 compares it with a set value. This set value is the maximum allowable flow rate corresponding to the load, and corresponds to the flow rate corresponding to the maximum allowable descending speed. Comparison means 10
If the comparison result in step 2 is set value > flow rate, the control amount output means 103 controls the electromagnetic proportional control valve 11 with the control amount corresponding to the opening degree of the work equipment lever 9a by the control amount extraction means 100, and vice versa. When the set value≦flow rate, the electromagnetic proportional control valve 11 is operated to be controlled with the control amount corresponding to the set value.

FIG. 4 shows a control flow. After initialization is performed at the start of the program, in block A it is determined whether the work implement lever is in the neutral position. In this case, the neutral position is a state in which the output value to the electromagnetic proportional control valve 11 corresponds to zero, each port of the electromagnetic proportional control valve 11 is closed, and the lift cylinder 1 maintains its position. As a result, when the work implement lever is in the neutral position, neutral control is performed in the controller 10 (block B), and the cylinder 1 is held in position. Further, when the work implement lever is in the up/down direction in block A, lift raising control is performed in block c. Further, when the work implement lever is in the downward direction in block A, a control amount corresponding to the opening degree of the work implement lever is calculated as the lever output. and,
In block E, the magnitude of the flow rate based on the oil pressure sensors 17b, 17a and the set value is determined, and if the flow rate is smaller than the set value, the lever output value is set as the output value of the controller (
Block F), if it is larger, set value x K (K coefficient) is set as the output value of the controller (Block G). In this way, the output of the electromagnetic proportional control valve is obtained from the controller as shown in block H.

[0023] In FIGS. 1 and 4, the explanation has been given using only the lift cylinder, but the invention is naturally applicable to the case of the tilt cylinder as well.

[0024]

[Effects of the Invention] As explained above, according to the present invention, hydraulic pressure sensors are provided at two locations in the hydraulic pipeline, and the flow rate is obtained based on the piping resistance to control the control valve and eventually the hydraulic cylinder, thereby eliminating various variations. True flow rate control eliminates shocks such as sudden drops at the start of descent, and prevents cargo from shifting or falling.

[Brief explanation of drawings]

FIG. 1 is a block diagram mainly showing control operations of a controller.

FIG. 2 is a characteristic diagram of the opening degree of the work implement lever and the control amount.

FIG. 3 is a characteristic diagram of pressure difference and lift downward flow rate.

FIG. 4 is a control flowchart.

FIG. 5 is an overall configuration diagram of a forklift.

FIG. 6 is a configuration diagram of a control circuit for a forklift.

[Explanation of symbols]

1 Lift cylinder 8 Tilt cylinder 9a, 9b Work machine lever 10 Controller 11 Solenoid proportional control valve 17a, 17b Oil pressure sensor 100 Controlled amount extraction force means 101 Flow rate calculation means 102 Comparison means

Claims (1)

[Claims] Claim 1: A work machine in which a controller controls a hydraulic device that executes a function based on an operation input of a work machine lever, comprising an electromagnetic proportional control valve in the hydraulic device and controlled by the controller, and the electromagnetic proportional control valve. A hydraulic pressure sensor connected to the controller is provided in each of the hydraulic lines between the electromagnetic proportional control valve side and the lift cylinder side, and the differential pressure between these two hydraulic pressure sensors is detected. A descending speed control device comprising: the controller configured to calculate a flow rate corresponding to a load, compare the flow rate with a set value, and control the opening and closing of the electromagnetic proportional control valve.