JP2009249070A - Forklift control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forklift control system capable of preventing the fork lowering speed from being excessively high when the weight of a load is large, and ensuring the opening of a lift proportional valve so that the inching is not disturbed. <P>SOLUTION: The control system comprises a control valve for limiting the amount of working fluid to be returned from a lift cylinder when a fork is lowered, and a hydraulic pressure sensor for indirectly detecting the weight of a load, and the opening of a lift proportional valve is changed according to the weight and the lift lever angle in accordance with the predetermined regulation (maps M<SB>0-8</SB>). The regulation (map M<SB>0-8</SB>) has the first tendency that the opening of the lift proportional valve is decreased as the weight is increased, and the second tendency that the opening of the lift proportional valve is increased as the lift lever angle is increased. The first tendency is intensified as the lift lever angle is increased, and preferably, the first tendency is less present in the inching area. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a forklift control system that detects a load of a load on a fork and controls a descending speed of the fork.

  As one of conventionally known forklifts, there is a forklift that detects the load of a load on the fork and performs various controls such as cargo handling control and travel control based on the detection information. In such a forklift, the pressure of the hydraulic system for raising and lowering the fork is usually detected by a hydraulic sensor, and the load of the load is detected indirectly (see, for example, Patent Documents 1 and 2).

  Of the various controls described above, raising and lowering of the fork according to the operation amount of the lift lever is performed by the control system shown in FIG. The control system 1 ′ includes a tank 100 that stores hydraulic oil, a pump 24 that sends hydraulic oil in the tank 100 to the lift cylinder 13 when the lift lever is operated to the lift side, and a lift lever that is operated to the lift side. The hydraulic oil sent from the pump 24 at this time is sent to the lift cylinder 13 by an amount corresponding to the opening to raise the fork, and when the lift lever is operated to the descending side, the operation corresponding to the opening is performed. And a lift proportional valve 101 for returning the oil to the tank 100 and lowering the fork. The pump 24 is driven by the motor 23.

  The control system 1 ′ includes a controller 2, a storage unit 3 ′ in which a plurality of maps referred to when the fork is lowered, and a hydraulic sensor 25 that detects the hydraulic pressure between the lift proportional valve 101 and the lift cylinder 13. Prepare. The hydraulic pressure between the lift proportional valve 101 and the lift cylinder 13 increases in proportion to the load of the load. Therefore, the load of the load can be indirectly detected by detecting the oil pressure.

The storage unit 3 ′ stores eight maps M ′ ₀ to ₇ shown in FIG. 9A, and the controller 2 uses one map (hereinafter referred to as “map”) that is used based on the detection information of the hydraulic sensor 25. Simply called “Selection Map”. Then, the lift proportional valve opening corresponding to the lift lever angle is determined using the selection map, and the lift proportional valve 101 is controlled to the opening. The controller 2 also controls the rotation speed of the motor 23 when the fork is raised.

Specifically, when the load is not loaded on the fork or the load is considerably small, the map M ′ ₀ having the largest lift proportional valve opening is selected, and the map M ′ ₁ is increased as the load of the load increases. ··· M _'7 is selected. That is, when the fork descends, the lift proportional valve opening corresponding to the same lift lever angle decreases as the load increases, and the amount of hydraulic fluid returned through the lift proportional valve 101 decreases. Thereby, when the load is large, the descending speed of the fork is prevented from becoming excessively high, and accidents such as load collapse while the fork is descending are prevented.
JP-A-5-4796 JP 2001-35497 A

  By the way, in cargo handling work using a forklift, “inching” is often performed in which the height of the fork is finely adjusted by repeatedly raising and lowering every minute. The operation amount of the lift lever 20 at the time of inching is very small, and the lift lever angle is operated within the range of the inching region of FIG.

However, when the load of the load is considerably large, that is, when the map M ′ ₇ , M ′ ₆ or the like is selected, the lift proportional valve 101 is hardly opened even if the lift lever is operated in the inching region, and as expected. In some cases, the fork could not be lowered.
By using the map shown in FIG. 9 (B), it is conceivable that a certain degree of lift proportional valve opening is ensured even when the map M ′ ₇ , M ′ _6, etc. is selected, and the above problem is solved. In this map M ′ _0-7 , when the lift lever angle is increased, the fork descending speed becomes excessively high, and there is a risk of collapse of the load.

  Therefore, the present invention prevents the fork descending speed from becoming excessively high when the load of the load on the fork is large, and secures a lift proportional valve opening degree that can smoothly perform inching. An object of the present invention is to provide a forklift control system capable of achieving the above.

  In order to solve the above problems, a forklift control system according to the present invention limits a lift cylinder that lifts and lowers a fork when a lift lever is operated, and an amount of hydraulic fluid returned from the lift cylinder when the fork is lowered. A control valve; and a hydraulic sensor that indirectly detects a load of the load on the fork by detecting a hydraulic pressure between the lift cylinder and the control valve, the load and the lift under a predetermined rule. A control system for a forklift in which the opening degree of the control valve is changed according to the amount of operation of the lever, and the rule is that the opening degree of the control valve decreases as the load increases, and is returned when the fork is lowered. The first tendency for the amount of hydraulic oil to decrease and the degree of opening of the control valve increases as the operation amount of the lift lever increases. , And a second tendency to amount of hydraulic oil to be returned when the fork descends increases, the first trend is characterized by stronger as the operation amount of the lift lever is increased.

  Preferably, the inking operation of the fork has almost no first tendency.

  Preferably, the second tendency in the control system is parabolic.

  Preferably, the rule in the control system is a map or an arithmetic expression indicating a relationship between an operation amount of the lift lever and an opening degree of the control valve.

  Moreover, in order to solve the said subject, the forklift which concerns on this invention is equipped with one of the said control systems, It is characterized by the above-mentioned.

  According to the present invention, when the load of the load on the fork is large, it is possible to prevent the fork descending speed from becoming excessively high and to ensure a lift proportional valve opening degree that allows inching to be performed smoothly. A forklift control system can be provided.

  Hereinafter, a preferred embodiment of a forklift control system according to the present invention will be described with reference to the accompanying drawings.

  The control system according to the first embodiment is provided, for example, in a forklift as shown in FIG. The forklift 10 includes a mast 12 supported so as to be tiltable forward and backward. The mast 12 includes a fork 11 supported so as to be movable up and down, and a lift cylinder 13 for moving the fork 11 up and down. In addition, the forklift 10 is provided with a tilt cylinder 14 for tilting the mast 12 and a steering cylinder 15 (not shown) for changing the steering angle of the steering wheel 16 located at the rear of the vehicle body. .

  Further, a lift lever 20 for raising and lowering the fork 11, a tilt lever 21 for tilting the mast 12 forward / backward, and a steering wheel 22 for changing the steering angle are provided in front of the driver's seat. For example, when the operator operates the lift lever 20 to the upward side, an amount of hydraulic oil corresponding to the lift lever angle is sent from the control system 1 to the lift cylinder 13 and the fork 11 is raised. On the contrary, when the operator operates the lift lever 20 to the lowering side, the amount of hydraulic oil corresponding to the lift lever angle is returned from the lift cylinder 13 to the control system 1 and the fork 11 is lowered.

  As shown in FIG. 2, the control system 1 includes a tank 100 that stores hydraulic oil, a pump 24 that sends hydraulic oil in the tank 100 to the lift cylinder 13 when the lift lever 20 is operated to the lift side, and a lift lever. The hydraulic oil sent from the pump 24 when the 20 is operated to the ascending side is sent to the lift cylinder 13 by an amount corresponding to the opening degree to raise the fork 11 and the lift lever 20 is operated to the descending side. At this time, a lift proportional valve 101 (corresponding to a “control valve”) that returns hydraulic oil in an amount corresponding to the opening to the tank 100 and lowers the fork 11 is provided. The pump 24 is driven by the motor 23.

  The control system 1 also includes a controller 2, a storage unit 3 in which a plurality of maps referred to when the fork is lowered, and a hydraulic sensor 25 that detects the hydraulic pressure between the lift proportional valve 101 and the lift cylinder 13. The hydraulic pressure between the lift proportional valve 101 and the lift cylinder 13 increases in proportion to the load of the load. Therefore, the load of the load can be indirectly detected by detecting the oil pressure. The hydraulic sensor 25 outputs an analog voltage signal that changes in proportion to the load to the controller 2 as detection information.

The storage unit 3 stores nine maps _M0 to _M8 shown in FIG. In the maps _{M0 to 8} applied in this embodiment, the relationship between the lift lever angle and the lift proportional valve opening is a parabolic shape. The controller 2 determines a selection map from the maps M _{0 to 8} based on the detection signal received from the hydraulic sensor 25. Then, the lift proportional valve opening corresponding to the lift lever angle is determined using the selection map, and the lift proportional valve 101 is controlled to the opening. The controller 2 also controls the rotation speed of the motor 23 when the fork is raised.

Specifically, when the hydraulic sensor 25 capable of detecting a load up to 1.8 t is used, if the detected load is 0.2 t from 0 t (a state where no load is loaded on the fork 11), the lift proportional valve opening is the largest map M ₀ is selected. Further, load if 0.4t from 0.2t, map _{M 1} is selected. Similarly, the detected load is equal to or larger than 1.6t, the smallest map M ₈ lift proportional valve opening is selected. That is, as the load increases, the lift proportional valve opening corresponding to the same lift lever angle decreases, and the amount of hydraulic fluid returned through the lift proportional valve 101 when the fork descends is limited (first tendency). .

Further, the maps _{M0 to 8} used in the present embodiment also have a second tendency that the lift proportional valve opening increases as the lift lever angle increases. As described above, in the maps _{M0 to M8} , the relationship between the lift lever angle and the lift proportional valve opening is a parabola, so the first tendency becomes stronger as the lift lever angle increases.

As a result, even when a map M ₈ , M _7, etc. with a considerably large load is selected, when the lift lever is operated in the inching region, it is almost the same as when the map M ₀ , M _1, etc. is selected. Thus, a sufficient lift proportional valve opening degree can be ensured. Further, according to the maps _M0 to _M8 , when the lift lever angle is increased, the lift proportional valve opening can be sufficiently limited.

  Therefore, according to the control system according to the first embodiment, even when the load of the load on the fork is large, the fork can be prevented from being excessively lowered and the fork can be lowered as desired during inching. .

  FIG. 4 shows a control system according to the second embodiment. The control system 1 according to the present embodiment includes a calculation unit 4 instead of the storage unit 3 (see FIG. 2) as a rule for determining the lift proportional valve opening. The calculation unit 4 calculates the lift proportional valve opening by calculation using the detection signal of the hydraulic sensor 25 and the lift lever angle of the lift lever 20 as variables.

ここで、Ｖ_ＯＰはリフト比例弁開度、θはリフトレバー角、ｗｔは油圧センサ２５で検出された荷重である。リフトレバー角θのとり得る値は０〜３２０であり、リフトレバー２０を下降側に最大操作した位置で“３２０”、操作しない中立位置で“０”となる。また、荷重ｗｔのとり得る値は０〜８であり、実施例１におけるマップの選択と同様に、荷重０〜０．２ｔで“０”、荷重１．６ｔ以上で“８”となる。 Although various formulas can be applied as the calculation formula, as an example, in this embodiment, the lift proportional valve opening is obtained by the following formula.

Here, V _OP is the lift proportional valve opening, θ is the lift lever angle, and wt is the load detected by the hydraulic sensor 25. Possible values of the lift lever angle θ are 0 to 320, “320” when the lift lever 20 is fully operated to the lower side and “0” when the lever is not operated. Further, the value that can be taken by the load wt is 0 to 8, which is “0” when the load is 0 to 0.2 t and “8” when the load is 1.6 t or more, as in the map selection in the first embodiment.

According to the above equation (1), the relationship between the lift lever angle θ and the lift proportional valve opening V _OP as shown in FIG. 5 can be obtained. The relationship shown in FIG. 5 and the map (see FIG. 3) used in the first embodiment are substantially the same, and the control system according to the present embodiment also obtains the same effects as the control system according to the first embodiment. be able to.

  In other words, even with the control system according to the second embodiment, even when the load of the load on the fork is large, the fork can be prevented from being excessively lowered and the fork can be lowered as desired during inching.

The present invention can also be applied to a control system having another hydraulic system. For example, the hydraulic system shown in FIG. 3 of Japanese Patent Application No. 2008-069591 is applied to the control system according to the third embodiment shown in FIG.
The control system according to the present embodiment includes a first hydraulic system 30 and a second hydraulic system 33, and the lift cylinder 13, the tilt cylinder are based on the operation amounts of the lift lever 20, the tilt lever 21, and the steering 22. 14 and the steering cylinder 15 are operated. Various types of information output from the lift lever 20, the tilt lever 21, the steering 22, and the hydraulic pressure sensor 25 are collected in the controller 2.

  The first hydraulic system 30 includes a plurality of valves including a first motor 31, a first pump 32, and a lift proportional valve 101. The first motor 31 rotates at a predetermined number of revolutions according to an instruction from the controller 2 and drives the first pump 32. The first pump 32 sends hydraulic oil in an amount proportional to the rotation speed of the first motor 31 to the priority valve 104. The orbit roll 105, the lift proportional valve 101 and the tilt proportional valve 102 in the control valve 106 are opened and closed according to the instruction of the controller 2, and the hydraulic oil sent through the priority valve 104 is supplied to the lift cylinder 13, the tilt cylinder 14, and Distribute to the steering cylinder 15.

  The second hydraulic system 33 includes a second motor 34, a second pump 35, and a lift electromagnetic valve 103. The second motor 34 rotates at a predetermined number of revolutions according to an instruction from the controller 2 and drives the second pump 35. The second pump 35 sends hydraulic oil in an amount proportional to the rotational speed of the second motor 34 to the lift electromagnetic valve 103. The lift solenoid valve 103 opens and closes in accordance with an instruction from the controller 2, and sends the supplied hydraulic oil to the lift cylinder 13. The second hydraulic system 33 also has a function of regenerating battery power using the potential energy of the fork 11 and the load when the fork descends.

  When the fork descends, the control system according to the present embodiment uses the lift lever angle of the lift lever 20, the load detected by the hydraulic sensor 5, and the map stored in the storage unit 3 (or the calculation formula of the calculation unit 4). Used to control the opening degree of the lift proportional valve 101.

  In other words, the control system according to the third embodiment can achieve the same effect as the control system according to the first and second embodiments. Even when the load on the fork is large, the fork descending speed is excessively high. In addition to preventing it from becoming faster, the fork can be lowered as desired during inching.

The preferred embodiments of the control system according to the present invention have been described above, but the present invention is not limited to these configurations.
For example, the map is not limited to that of the first embodiment (see FIG. 3), and a map as shown in FIG. 7 in which the lift proportional valve opening is hardly changed according to the load in the inching region can be applied. . Similarly, the expression (1) in the second embodiment is merely an example, and other arithmetic expressions can be applied.
Also, other hydraulic systems can be applied to the hydraulic system of each embodiment. Any hydraulic system in which the amount of hydraulic fluid returned from the lift cylinder when the fork descends is limited by a lift proportional valve (control valve) can be applied to the control system according to the present invention.

It is a side view of an example of a forklift to which the present invention is applied. 1 is a block diagram illustrating a configuration of a control system according to a first embodiment and its peripheral portion, and a hydraulic circuit diagram. It is a map which shows the correspondence of a lift lever angle and a lift proportional valve opening degree applied to the control system which concerns on Example 1. FIG. FIG. 6 is a block diagram illustrating a configuration of a control system according to a second embodiment and a peripheral portion thereof, and a hydraulic circuit diagram. Obtained by the calculation formula to be applied to the control system according to the second embodiment, a graph showing a relationship between the lift lever angle θ and the lift proportional valve opening V _OP. FIG. 9 is a block diagram illustrating a configuration of a control system according to a third embodiment and its peripheral portion, and a hydraulic circuit diagram. It is a map which shows the correspondence of a lift lever angle and a lift proportional valve opening degree applied to the control system which concerns on a modification. It is the block diagram and hydraulic circuit diagram which show the structure of the conventional control system and its peripheral part. FIG. 6A is a map showing a correspondence relationship between a lift lever angle and a lift proportional valve opening, which is applied to a conventional control system, and (A) is a map that emphasizes that the descending speed of the fork is not excessively increased; B) is a map that emphasizes operability during inching.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control system 2 Controller 3 Memory | storage part 4 Calculation part 10 Forklift 11 Fork 12 Mast 13 Lift cylinder 14 Tilt cylinder 15 Steering cylinder 16 Steering wheel 20 Lift lever 21 Tilt lever 22 Steering 23 Motor 24 Pump 25 Hydraulic sensor 30 1st hydraulic system 31 1st motor 32 1st pump 33 2nd hydraulic system 34 2nd motor 35 2nd pump 100 tank 101 lift proportional valve (control valve)
102 Tilt proportional valve 103 Lift solenoid valve 104 Priority valve 105 Orbit roll 106 Control valve

Claims (5)

A lift cylinder that raises and lowers the fork when the lift lever is operated, a control valve that limits the amount of hydraulic fluid returned from the lift cylinder when the fork is lowered, and a hydraulic pressure between the lift cylinder and the control valve is detected. And a hydraulic sensor that indirectly detects the load of the load on the fork, and a forklift whose opening degree of the control valve is changed according to the load and the amount of operation of the lift lever under a predetermined rule Control system
According to the rule, as the load increases, the opening degree of the control valve decreases, and the amount of hydraulic fluid returned when the fork descends decreases, and the operation amount of the lift lever increases. As the opening of the control valve increases, the amount of hydraulic fluid returned when the fork is lowered has a second tendency to increase,
The control system according to claim 1, wherein the first tendency becomes stronger as the operation amount of the lift lever becomes larger.   2. The control system according to claim 1, wherein at the time of inching operation of the fork, the control system has almost no first tendency.   The control system according to claim 1, wherein the second tendency is a parabolic shape.   The control system according to claim 1, wherein the rule is a map or an arithmetic expression that indicates a relationship between an operation amount of the lift lever and an opening degree of the control valve.   A forklift comprising the control system according to claim 1.

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